JP2017139211A - Illumination optical communication device and communication module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination optical communication device and a communication module which can suppress occurrence of a reception error of a reception device.SOLUTION: An illumination optical communication device includes a light source 53 for emitting illumination light, a power supply circuit 52a for supplying current to the light source 53 and making the average of the current constant, a switch SW which is connected in series with the light source 53 for making the current flowing through the light source 53 intermittent, a signal generating circuit SG for generating a binary communication signal for controlling ON and OFF of the switch SW to modulate the illumination light, and a current suppressing circuit 1 which is connected in series with the light source 53 and the switch SW and suppresses the current flowing through the light source 53 according to a reference value so that the current does not exceed the current set value corresponding to the reference value.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to an illumination light communication device and a communication module that perform visible light communication by modulating illumination light.

2. Description of the Related Art Conventionally, visible light communication in which a signal is transmitted by modulating the intensity of illumination light has been proposed in a luminaire including a light emitting diode (LED) as a light source. In such an illumination light communication device, a signal is transmitted by modulating the illumination light itself, so that a special device such as an infrared communication device is not required. In addition, since a power saving can be realized by using a light emitting diode as a light source for illumination, use in a ubiquitous information system in an underground shopping area is being studied.

  FIG. 164A is a diagram illustrating a configuration of the illumination light communication apparatus disclosed in Patent Document 2. In this circuit, a resistor R3 for current detection, a load circuit 53 including three light emitting diodes, an inductor L1, and a switch element Q1 are connected in series between both ends of the DC power supply 51, and the switch element Q1 is controlled. On / off is controlled by the circuit 54. Further, a smoothing capacitor C3 and a rectifier diode D2 are connected between both ends of the series circuit of the load circuit 53 and the inductor L1, and a DC-DC converter is configured together with the inductor L1 and the switch element Q1. The control circuit 54 receives a feedback signal from the constant current feedback circuit 55 and controls the output current of the DC-DC converter to be substantially constant. The DC-DC converter is a constant current feedback type power source controlled to supply a constant current. Further, the communication signal S1 is input to the control circuit 54, and the load current I1 is modulated by turning on / off the switch element Q1 at a high frequency during a period when the communication signal is high.

  FIG. 164B is a diagram showing a circuit portion including a specific example of the constant current feedback circuit 55 of FIG. 164A. The constant current feedback circuit 55 compares the voltage drop of the resistor R3 through which the load current I1 flows with the level of the reference source E1 by the error amplifier A1, amplifies the deviation, and outputs the amplified deviation to the control circuit 54. The series circuit of the resistor R4 and the capacitor C2 connected between the inverting input terminal and the output terminal of the error amplifier A1 constitutes a phase compensation circuit for ensuring the stability of the feedback system. In such a phase compensation circuit, a compensation circuit including an integration element is generally used to adjust a gain and a phase in a circuit transfer function, which is known as PI control or PID control in classical information theory. For example, FIG. 164C is a diagram illustrating an illumination light communication device including an average current detection circuit disclosed in Patent Document 1. It can be said that the integrating circuit 56 (consisting of the resistor R5 and the capacitor C3) connected between both ends of the current detection resistor R3 uses the above-described PI control as the output averaging means.

  Further, in Patent Document 3, in visible light communication using illumination light, the brightness of illumination is made constant both during non-communication in which a carrier signal for communication is not exchanged and in communication in which a carrier signal is exchanged. At the same time, a power source for illumination light communication with low cost and high light source utilization efficiency and power efficiency is disclosed.

  Furthermore, the illumination light communication device of Patent Document 4 includes a DC-DC converter having a step-up mode and a step-down mode, a constant current clamp switch, and a constant current clamp control circuit, and the on-duty of the constant current clamp switch is stored in advance. It is disclosed that the current limit is started when the maximum value (or the minimum value) is reached, and that the limit is stopped when the current becomes smaller than the maximum value (or greater than the minimum value).

  Further, Patent Document 5 discloses a dimming illumination device that makes flicker inconspicuous even when the amount of light is small, and improves the data transmission speed.

JP 2006-120910 A JP 2012-69505 A JP 2010-283616 A JP 2011-130557 A Japanese Patent Laying-Open No. 2015-216580

  FIG. 165 is a diagram schematically showing waveforms of an intermittent signal, an output voltage at the time of modulation, and a load current (LED current) in a circuit configuration of 100% modulation using a constant current feedback type power supply. Here, 100% modulation means that the illumination light is modulated in two states, a lighting state and a light-off state. The intermittent signal is a modulation signal that controls on and off of the switch. The output voltage is an output voltage of a constant current feedback type power supply. The LED current is a current flowing through the LED.

  In the figure, when the intermittent signal (modulation signal) is low, the switch is turned off and the LED is turned off. The longer the OFF period, the greater the output voltage across the smoothing capacitor 65. At the moment when the intermittent signal (modulation signal) becomes high, a large overshoot occurs in the LED current. That is, since the output voltage is high at the moment when the intermittent signal (modulation signal) becomes high, the peak value of the LED current increases, and the LED current also decreases as the output voltage decreases.

  Thus, there is a problem that the overshoot of the LED current increases as the switch is intermittent. In general, a receiving device for optical communication reads a change in an optical signal. When the overshoot is large, it becomes a main cause of malfunction (for example, reception error). As described above, when 100% modulation is performed using a constant current type power supply, there is a problem that the receiving apparatus may malfunction.

  An object of the present invention is to provide an illumination optical communication device and a communication module that are unlikely to cause a reception error of the receiving device even when optical communication with 100% modulation is performed using a constant current feedback type power source.

  In order to achieve the above object, one embodiment of an illumination light communication apparatus according to the present invention includes a light source that emits illumination light, a power supply circuit that supplies current to the light source and makes the current constant, and the light source. Connected in series with the switch for intermittently passing the current flowing through the light source, a signal generating circuit for generating a binary communication signal for controlling on and off of the switch to modulate the illumination light, the light source, and A current suppression circuit connected in series with the switch and configured to suppress a current flowing through the light source so as not to exceed a variable current set value;

  One embodiment of the communication module according to the present invention is a communication module that modulates illumination light that can be attached to and detached from the illumination device, the switch being connected in series with the light source of the illumination device, and the illumination light being modulated. A signal generation circuit for generating a binary communication signal for controlling on and off of the switch, and the light source connected in series with the light source and the switch so as not to exceed a variable current set value. A current suppression circuit for suppressing a flowing current.

  According to the illumination light communication device and the communication module according to the present invention, there is an effect that it is difficult to cause a reception error of the reception device even when optical communication with 100% modulation is performed using a constant current feedback power source.

1A is a circuit diagram showing a configuration of an illumination light communication apparatus according to Embodiment 1. FIG. FIG. 1B is a circuit diagram illustrating a configuration of a lighting device to which a communication module is not added in the first embodiment. FIG. 2 is a circuit diagram showing a first modification of the current suppression circuit in FIG. 1A. FIG. 3 is a circuit diagram showing a second modification of the current suppression circuit in FIG. 1A. FIG. 4 is a circuit diagram showing a third modification of the current suppression circuit in FIG. 1A. FIG. 5 is a diagram showing a first simulation result for the circuit example of FIG. FIG. 6 is a diagram illustrating a second simulation result for the circuit example of FIG. FIG. 7 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 8 is a diagram showing a fourth simulation result for the circuit example of FIG. FIG. 9 is a diagram illustrating a fifth simulation result for the circuit example of FIG. FIG. 10 is a diagram illustrating a sixth simulation result for the circuit example of FIG. FIG. 11 is a diagram showing a seventh simulation result for the circuit example of FIG. FIG. 12 is a diagram showing an eighth simulation result for the circuit example of FIG. FIG. 13 is a diagram illustrating a ninth simulation result for the circuit example in FIG. 2. FIG. 14 is a diagram illustrating a tenth simulation result for the circuit example of FIG. FIG. 15 is an explanatory diagram showing a modulation method of a communication signal. FIG. 16 is a diagram illustrating examples (1) to (4) of communication signals. FIG. 17 is a diagram illustrating a simulation result (part 1) of the case (1) of FIG. FIG. 18 is a diagram illustrating a simulation result (part 2) of the case (1) of FIG. FIG. 19 is a diagram illustrating a simulation result (part 1) of the case (2) of FIG. FIG. 20 is a diagram illustrating a simulation result (part 2) of the case (2) of FIG. FIG. 21 is a diagram showing a simulation result (part 1) of the case (3) of FIG. FIG. 22 is a diagram showing a simulation result (part 2) of the case (3) of FIG. FIG. 23 is a diagram illustrating a simulation result (part 1) of the case (4) of FIG. FIG. 24 is a diagram illustrating a simulation result (part 2) of the case (4) in FIG. FIG. 25A is a diagram showing the relationship between the current setting value and the LED current (average value and fluctuation value) as a simulation result of case (1) in FIG. FIG. 25B is a diagram showing a relationship between the current set value and the ripple rate of the LED current as a simulation result of the case (1) of FIG. FIG. 25C is a diagram illustrating a relationship between the current setting value and the circuit loss as a simulation result of the case (1) of FIG. FIG. 26A is a diagram showing the relationship between the current setting value and the LED current (average value and fluctuation value) as a simulation result of case (2) in FIG. FIG. 26B is a diagram illustrating a relationship between the current setting value and the ripple rate of the LED current as a simulation result of the case (2) of FIG. FIG. 26C is a diagram illustrating a relationship between the current set value and the circuit loss as a simulation result of the case (2) of FIG. FIG. 27A is a diagram showing the relationship between the current setting value and the LED current (average value and fluctuation value) as a simulation result of case (3) in FIG. FIG. 27B is a diagram showing a relationship between the current set value and the ripple rate of the LED current as a simulation result of the case (3) of FIG. FIG. 27C is a diagram illustrating a relationship between the current set value and the circuit loss as a simulation result of the case (3) in FIG. FIG. 28A is a diagram showing the relationship between the current setting value and the LED current (average value and fluctuation value) as a simulation result of case (4) in FIG. FIG. 28B is a diagram showing a relationship between the current set value and the ripple rate of the LED current as a simulation result of the case (4) in FIG. FIG. 28C is a diagram illustrating a relationship between the current setting value and the circuit loss as a simulation result of the case (4) in FIG. 16. FIG. 29A is an explanatory diagram illustrating a waveform of an intermittent LED current. FIG. 29B is a diagram showing a current setting value according to the on-duty ratio. FIG. 30A is a circuit diagram showing a modification of the illumination light communication apparatus in the first embodiment. FIG. 30B is a waveform diagram showing threshold control of the switching current in the power supply circuit of FIG. 30A. FIG. 31A is a diagram illustrating a first configuration example of the current suppression circuit in the second embodiment. FIG. 31B is a diagram illustrating a second configuration example of the current suppression circuit according to Embodiment 2. FIG. 32A is a diagram showing a relationship between the on-duty ratio and the LED current as a simulation result of the circuit in which the diode of FIG. 31A is deleted. FIG. 32B is a diagram showing a relationship between the on-duty ratio and the LED current ripple rate as a simulation result of the circuit in which the diode of FIG. 31A is deleted. FIG. 33A is a diagram showing the relationship between the on-duty ratio and the LED current as a simulation result of FIG. 31A. FIG. 33B is a diagram showing a relationship between the on-duty ratio and the LED current ripple rate as a simulation result of FIG. 31A. FIG. 34 is a diagram showing the relationship between the on-duty ratio and the circuit loss as a simulation result of FIG. 31A. FIG. 35A is a diagram illustrating a configuration example of a current suppression circuit in the third embodiment. FIG. 35B is a diagram illustrating a first configuration example of the current suppression circuit in the fourth embodiment. FIG. 35C is a diagram illustrating a second configuration example of the current suppression circuit in the fourth embodiment. FIG. 35D is a diagram illustrating a third configuration example of the current suppression circuit in the fourth embodiment. FIG. 35E is a diagram illustrating a configuration example of the current suppression circuit in the fifth embodiment. FIG. 35F is a diagram illustrating a configuration example of a current suppression circuit in the sixth embodiment. FIG. 36 is a diagram showing a relationship between the on-duty ratio and the LED current as a simulation result of FIG. 35A in the third embodiment. FIG. 37 is a diagram showing the relationship between the on-duty ratio and the ripple rate of the LED current as a simulation result of FIG. 35A in the third embodiment. FIG. 38 is a diagram showing the relationship between the on-duty ratio and the circuit loss as a simulation result of FIG. 35A in the third embodiment. FIG. 39 is a diagram showing a relationship between the on-duty ratio and the LED current as a simulation result of FIG. 35B in the fourth embodiment. FIG. 40 is a diagram illustrating a relationship between the on-duty ratio and the ripple rate of the LED current as a simulation result of FIG. 35B in the fourth embodiment. FIG. 41 is a diagram showing the relationship between the on-duty ratio and the circuit loss as a simulation result of FIG. 35B in the fourth embodiment. FIG. 42 is a diagram showing a relationship between the on-duty ratio and the LED current as a simulation result of FIG. 35E in the fifth embodiment. FIG. 43 is a diagram showing a relationship between the on-duty ratio and the ripple rate of the LED current as a simulation result of FIG. 35E in the fifth embodiment. FIG. 44 is a diagram showing the relationship between the on-duty ratio and the circuit loss as a simulation result of FIG. 35E in the fifth embodiment. FIG. 45 is a diagram illustrating a comparative reference example in which the current suppression circuit is deleted from FIG. 1A. FIG. 46 is a diagram showing LED current and output voltage waveforms when the on-duty ratio is 60%, 75%, 90%, and 100%, as a simulation result of the comparative reference circuit of FIG. FIG. 47 is a diagram showing the LED current and output voltage waveforms when the on-duty ratio is 75% and the smoothing capacitors are 10 μF, 20 μF, and 30 μ as simulation results of the comparative reference circuit of FIG. FIG. 48A is a diagram showing a relationship between the on-duty ratio and the LED current as a simulation result of the circuit for comparison and reference in FIG. FIG. 48B is a diagram showing a relationship between the on-duty ratio and the ripple rate of the LED current as a simulation result of the circuit for comparison and reference in FIG. FIG. 49A is a diagram showing a relationship between the on-duty ratio and the output voltage as a simulation result of the circuit for comparison and reference in FIG. FIG. 49B is a diagram showing a relationship between the on-duty ratio and the ripple rate of the output voltage as a simulation result of the circuit for comparison and reference in FIG. FIG. 50A is a circuit diagram showing a configuration example of the illumination light communication apparatus in the seventh embodiment. FIG. 50B is a diagram showing a truth table representing the communication signals of the signal generation circuit in FIG. 50A, the operating states of the switches, and transistors. FIG. 51 is a diagram showing a first simulation result for the circuit example of FIG. 50A. FIG. 52 is a diagram showing a second simulation result for the circuit example of FIG. 50A. FIG. 53 is a diagram showing a third simulation result for the circuit example of FIG. 50A. FIG. 54 is a diagram showing a fourth simulation result for the circuit example of FIG. 50A. FIG. 55 is a diagram illustrating a configuration example of a communication module according to the eighth embodiment. FIG. 56 is a diagram showing simulation results for the circuit example of FIG. FIG. 57A is a diagram illustrating a configuration example of a communication module according to Embodiment 9. FIG. 57B is a diagram showing a truth value table representing operation states of communication signals, two valves, and transistors from the signal generation circuit in FIG. 57A. FIG. 57C is a diagram illustrating a modification of the communication module according to Embodiment 9. FIG. 57D is a diagram showing a truth table representing the operation state of the communication signal, the two valves, and the transistor 2 from the signal generation circuit in FIG. 57C. FIG. 57E is a diagram showing another modification of the communication module in Embodiment 9. FIG. 57F is a diagram showing a truth table representing the communication signals from the signal generation circuit in FIG. 57E, the operating states of the two valves, the transistor, and the bipolar transistor. FIG. 57G is a diagram illustrating a configuration example of the communication module 10 including a modification of the dual control circuit of FIG. 57A. FIG. 58 is a diagram showing a first simulation result for the circuit example of FIG. 57C. FIG. 59 is a diagram showing a second simulation result for the circuit example of FIG. 57C. FIG. 60 is a diagram illustrating a third simulation result for the circuit example in FIG. 57C. FIG. 61 is a diagram showing a first simulation result for the circuit example of FIG. 57E. FIG. 62 is a diagram showing a second simulation result for the circuit example of FIG. 57E. FIG. 63 is a diagram showing a third simulation result for the circuit example of FIG. 57E. FIG. 64 is a circuit diagram showing a modification of the illumination light communication apparatus in the seventh embodiment. FIG. 65 is a block diagram of the illumination light communication apparatus according to the tenth embodiment. FIG. 66 is a diagram showing another example of the current suppression circuit according to the tenth embodiment. FIG. 67 is a diagram illustrating another example of the current suppression circuit according to the tenth embodiment. FIG. 68 is a diagram showing another example of the current suppression circuit according to the tenth embodiment. FIG. 69 is a diagram illustrating an operation example of the illumination light communication apparatus according to the tenth embodiment. FIG. 70 is a diagram showing a schematic configuration of the illumination light communication apparatus according to the tenth embodiment. FIG. 71 is a diagram illustrating a schematic configuration of an illumination light communication apparatus according to a comparative example of the tenth embodiment. FIG. 72 is a diagram showing a first control example of the current set value according to the tenth embodiment. FIG. 73 is a diagram illustrating a second control example of the current set value according to the tenth embodiment. FIG. 74 is a diagram showing a third control example of the current set value according to the tenth embodiment. FIG. 75 is a diagram showing a modification of the third control example of the current set value according to the tenth embodiment. FIG. 76 is a diagram showing a fourth control example of the current set value according to the tenth embodiment. FIG. 77 is a diagram illustrating a usage example of the illumination light communication apparatus according to Embodiment 10. FIG. 78 is a diagram showing an example of the appearance of the illumination light communication apparatus according to Embodiment 10. FIG. 79 is a diagram illustrating another example of use of the illumination light communication apparatus according to Embodiment 10. FIG. 80 is a circuit diagram showing a modification of the illumination light communication apparatus in the eleventh embodiment. FIG. 81 is a circuit diagram showing a fourth modification of the current suppression circuit. FIG. 82 is a circuit diagram showing a fifth modification of the current suppression circuit. FIG. 83 is a block diagram illustrating a configuration example of the control circuit and the signal generation circuit. FIG. 84A is a flowchart illustrating a processing example of the control circuit. FIG. 84B is an explanatory diagram of the shift register in the control circuit. FIG. 84C is a flowchart showing an example of correction in step S45 of FIG. 84B. FIG. 85 is a circuit diagram showing a configuration example of the illumination light communication apparatus in the twelfth embodiment. FIG. 86 is a diagram illustrating a circuit example of the DC-DC converter according to the twelfth embodiment. FIG. 87 is a time chart of each part potential of the illumination light communication apparatus according to the twelfth embodiment. FIG. 88 is a circuit diagram showing a configuration example of the illumination light communication apparatus in the thirteenth embodiment. FIG. 89 is a circuit diagram illustrating a configuration example of the illumination light communication apparatus in the comparative reference example. FIG. 90 is a time chart of each part potential of the illumination optical communication device in the comparative reference example. FIG. 91 is a circuit diagram showing a modification of the illumination light communication apparatus according to the twelfth or thirteenth embodiment. FIG. 92 is a waveform diagram showing threshold control of switching current in the power supply circuit of FIG. FIG. 93A is a circuit diagram showing a configuration of the illumination light communication apparatus in the fourteenth embodiment. FIG. 93B is a circuit diagram illustrating a more detailed configuration example of the current suppression circuit. FIG. 94A is a diagram showing a first simulation result. FIG. 94B is a diagram showing a second simulation result. FIG. 95 is a diagram schematically showing the relationship between two communication signals having different on-duty ratios and the LED current. FIG. 96 is a diagram showing the relationship between the on-duty ratio and the LED current when the current set value is fixed. FIG. 97A is a diagram showing a third simulation result. FIG. 97B is a diagram showing a fourth simulation result. FIG. 98 is a diagram showing LED current, output voltage, SW voltage, and current suppression circuit voltage in FIG. 93A. FIG. 99A is a circuit diagram showing a configuration of the illumination light communication apparatus in the fifteenth embodiment. FIG. 99B is a circuit diagram showing a configuration of an illumination light communication apparatus to which a communication module is not added in the fifteenth embodiment. FIG. 99C is a circuit diagram showing a specific configuration example of the communication module and the second current suppression circuit in the fifteenth embodiment. FIG. 100 is a diagram showing simulation results for the circuit examples of FIGS. 99A and 99C. FIG. 101 is a diagram showing a current setting value according to the on-duty ratio. FIG. 102 is a circuit diagram showing a configuration of the illumination light communication apparatus in the sixteenth embodiment. FIG. 103 is a circuit diagram showing a configuration of the illumination light communication apparatus in the seventeenth embodiment. FIG. 104 is a diagram showing a first simulation result for the circuit example of FIG. FIG. 105 is a diagram showing a second simulation result for the circuit example of FIG. FIG. 106 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 107 is a diagram showing a first simulation result for the circuit example of FIG. 103. FIG. 108 is a diagram illustrating a second simulation result for the circuit example of FIG. 103. FIG. 109 is a diagram illustrating a third simulation result for the circuit example of FIG. 103. FIG. 110 is a circuit diagram showing a configuration of the illumination light communication apparatus in the eighteenth embodiment. FIG. 111 is a circuit diagram showing another configuration of the illumination light communication apparatus in the eighteenth embodiment. FIG. 112A is a circuit diagram showing a current suppression circuit including a first modification of the reference source in the eighteenth embodiment. FIG. 112B is a circuit diagram showing a current suppression circuit including a second modification of the reference source in the eighteenth embodiment. FIG. 113 is a block diagram of the illumination light communication apparatus according to the nineteenth embodiment. FIG. 114 is a diagram illustrating the configuration of the illumination unit according to Embodiment 19. In FIG. FIG. 115 is a diagram illustrating a modulation operation by the illumination light communication apparatus according to the nineteenth embodiment. FIG. 116 is a diagram illustrating a dimming operation by the illumination light communication apparatus according to the nineteenth embodiment. FIG. 117 is a diagram for explaining a problem when the modulation operation and the dimming operation are combined. FIG. 118 is an operation flowchart of the illumination light communication apparatus according to the nineteenth embodiment. FIG. 119 is a diagram illustrating a first operation example of the illumination light communication apparatus according to the nineteenth embodiment. FIG. 120 is a diagram illustrating a second operation example of the illumination light communication apparatus according to the nineteenth embodiment. FIG. 121 is a block diagram of a receiving apparatus according to the nineteenth embodiment. FIG. 122 is a flowchart of operation by the receiving apparatus according to the nineteenth embodiment. FIG. 123 is a block diagram of an illumination light communication apparatus according to the twentieth embodiment. FIG. 124 is a diagram illustrating an operation example of the illumination light communication apparatus according to the twentieth embodiment. FIG. 125 is a block diagram of a modification of the illumination light communication apparatus according to Embodiment 20. FIG. 126 is a diagram illustrating a usage example of the illumination light communication apparatus according to Embodiment 20. FIG. 127 is a block diagram illustrating a configuration example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 128 is a waveform diagram showing a first operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 129A is a waveform diagram showing a second operation example of the illumination light communication apparatus according to Embodiment 21. FIG. 129B is a waveform diagram illustrating a second operation example of the illumination light communication apparatus according to Embodiment 21. FIG. 130 is a waveform diagram showing a third operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 131 is a waveform diagram showing a first operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 132 is a waveform diagram showing a second operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 133 is a waveform diagram showing a third operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 134 is a waveform diagram showing a fourth operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 135 is a waveform diagram showing a fifth operation example of the illumination light communication apparatus according to the twenty-first embodiment. FIG. 136 is a diagram illustrating a configuration example of a modulation circuit which is a premise of the twenty-second embodiment. FIG. 137 is a diagram illustrating a configuration example of a modulation circuit and a configuration example of an overpower detection circuit according to the twenty-second embodiment. FIG. 138 is a waveform diagram of each part during normal operation in the twenty-second embodiment. FIG. 139 is a waveform diagram of each part during overpower operation in the twenty-second embodiment. FIG. 140 is a diagram showing main circuit loss and overpower detection level in six models with different LED loads. FIG. 141 is a diagram illustrating a configuration example of a modulation circuit according to the twenty-third embodiment. FIG. 142 is a waveform diagram of each part during normal operation in the twenty-third embodiment. FIG. 143 is a waveform diagram of each part during overpower operation in the twenty-second embodiment. FIG. 144 is a diagram illustrating main circuit loss and overpower detection level in six models with different LED loads. FIG. 145 is a diagram illustrating a configuration example of the modulation circuit according to the twenty-fourth embodiment. FIG. 146 is a diagram illustrating a configuration example of the modulation circuit according to the twenty-fifth embodiment. FIG. 147 is a diagram illustrating a configuration example of the modulation circuit according to the twenty-sixth embodiment. FIG. 148 is a diagram illustrating a configuration example of the modulation circuit according to the twenty-seventh embodiment. FIG. 149 is a diagram illustrating a configuration example of the modulation circuit according to the twenty-eighth embodiment. FIG. 150 is a waveform diagram (normal state) of each part of the explanation during normal operation in the twenty-second embodiment. FIG. 151 is a diagram illustrating a result of simulating rising waveforms of the gate voltage and the LED current when the inverted communication signal rises. FIG. 152 is a diagram illustrating a result of simulating falling waveforms of the gate voltage and the LED current when the inverted communication signal falls. FIG. 153 is a diagram illustrating signal waveforms of respective units in the case where the rise delay time is involved. FIG. 154 is a diagram illustrating a configuration example of the modulation circuit including the delay circuit according to the twenty-eighth embodiment. FIG. 155 is a diagram illustrating signal waveforms of the respective units in FIG. 154. FIG. 156 is a diagram illustrating main circuit loss with respect to LED current in a plurality of models having different load capacities. FIG. 157 is a diagram illustrating main circuit loss with respect to load power in a plurality of models having different load capacities. FIG. 158 is a diagram illustrating the optimum resistance value with respect to the LED current in a plurality of models having different load capacities. FIG. 159 is a diagram illustrating the optimum reference resistance with respect to the load power in a plurality of models having different load capacities. FIG. 160 is a circuit diagram for explaining the gate capacitance. FIG. 161 is a diagram for explaining the influence of the gate capacitance. FIG. 162 is a diagram illustrating a configuration example of a modulation circuit including a delay circuit according to the twenty-ninth embodiment. FIG. 163 is a diagram illustrating signal waveforms of the respective units in FIG. 162. FIG. 164A is a diagram illustrating a configuration of the illumination light communication apparatus disclosed in Patent Document 2. FIG. 164B is a diagram showing a circuit portion including a specific example of the constant current feedback circuit of FIG. 164A. FIG. 164C is a diagram illustrating an illumination optical communication device including an average current detection circuit disclosed in Patent Document 1. FIG. 165 is a diagram schematically showing waveforms of an intermittent signal, an output voltage at the time of modulation, and a load current (LED current) in a circuit configuration of 100% modulation using a constant current feedback type power supply.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, steps, the order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims showing the highest concept of the present invention will be described as optional constituent elements that constitute a more preferable embodiment. Each figure is a schematic diagram and does not necessarily represent exact dimensions and numerical values.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
[1.1 Illumination light communication device configuration]
First, the configuration of the illumination light communication apparatus according to the first embodiment will be described.

  1A is a circuit diagram showing a configuration of an illumination light communication apparatus according to Embodiment 1. FIG. The illumination light communication device includes a power supply circuit 52 a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and the communication module 10. The communication module 10 includes an intermittent switch SW, a signal generation circuit SG, and a current suppression circuit 1.

  The power supply circuit 52 a includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64, a detection resistor 66, and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

  The power supply circuit 52a performs full-wave rectification on a commercial power supply (for example, AC 100V) with a rectifier bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected across the output of the DC-DC converter 64. In parallel with the smoothing capacitor 65, a series circuit of the load circuit 53, the current suppression circuit 1, and the intermittent switch SW is connected.

  The power supply circuit 52a has a function of detecting the current flowing through the load circuit 53 directly or indirectly and controlling the current value to be constant. This function is based on the detection resistor 66 and the constant current feedback circuit 67 for directly detecting the current of the load circuit 53 in FIG. 1A. The constant current feedback circuit 67 includes an amplifier 69, a reference voltage source 72 connected to the positive input terminal of the amplifier 69, an input resistor 68 connected to the negative input terminal of the amplifier 69, an output terminal of the amplifier 69, and the amplifier 69. Gain adjustment resistor 71 and phase compensation capacitor 70 connected between the negative input terminals. The constant current feedback circuit 67 compares the voltage drop of the detection resistor 66 with the voltage of the reference voltage source 72 by the amplifier 69, amplifies the difference, and feeds back to the control unit of the DC-DC converter 64. That is, negative feedback control is applied to the DC-DC converter 64 so that the voltage drop of the detection resistor 66 matches the reference voltage. Further, the gain is set by the voltage dividing ratio of the resistor 71 connected between the inverting input terminal and the output terminal of the amplifier 69 and the input resistor 68, and the capacitor 70 provided in parallel with the resistor 71 is integrated for phase compensation. Acts as an element.

  The smoothing capacitor 65 is connected between the outputs of the power supply circuit 52a and smoothes the output of the power supply circuit 52a.

  The load circuit 53 includes a plurality of light emitting diodes connected in series between the outputs of the power supply circuit 52a, and the output of the power supply circuit is supplied. The plurality of light emitting diodes are light sources that emit illumination light.

  The intermittent switch SW is added in series with the load circuit 53, and interrupts the current supplied from the power supply circuit 52a to the load circuit 53.

  The signal generation circuit SG generates a binary communication signal for controlling on / off of the intermittent switch SW in order to modulate the illumination light. The communication signal is input to the control terminal of the intermittent switch SW and turns on / off the intermittent switch SW. The signal generation circuit SG may repeatedly generate an ID signal indicating an ID unique to the illumination light communication device as a communication signal, or generate a communication signal according to a transmission signal input from an external device. Also good.

[1.2 Configuration of Current Suppression Circuit 1]
Next, a configuration example of the current suppression circuit 1 will be described.

  The current suppression circuit 1 is added in series with the load circuit 53 and the intermittent switch SW, and suppresses the magnitude of the current flowing through the load circuit 53. For example, the current suppression circuit 1 is connected in series with the load circuit 53 as the light source and the intermittent switch SW, and the current flowing through the load circuit 53 according to the reference value so as not to exceed the current setting value corresponding to the reference value. You may make it suppress. In this way, since the overshoot generated in the current flowing through the load circuit 53 that is the light source can be reduced at the moment when the intermittent switch SW is turned on from the off state, the reception error in the receiving device can be reduced.

  The current suppression circuit 1 includes a transistor 2 that is a MOSFET, a resistor 3 connected to a source, an amplifier 5, a reference source 4, and a control circuit 6.

  The reference source 4 outputs a reference value to the positive input terminal of the amplifier 5. The reference value defines the upper limit (current setting value) of the current flowing through the load circuit 53 that is a light source. For example, the reference value is proportional to the current setting value. The reference source 4 may output the reference value as a fixed value, or may output a variable reference value according to the arrangement pattern (for example, bit pattern) of communication signals generated by the signal generation circuit SG. .

  The transistor 2 is connected in series to the load circuit 53 that is a light source and the intermittent switch SW, and suppresses the current flowing through the load circuit 53 based on the reference value.

  The resistor 3 is a source resistor for detecting the magnitude of the current flowing through the load circuit 53. The source side terminal of the resistor 3 is connected to the negative input terminal of the amplifier 5.

  The amplifier 5 has a positive input terminal connected to the reference source 4 and a negative input terminal connected to the source of the transistor 2. The amplifier 5 amplifies the difference between the current value detected by the reference value and the resistor 3, and outputs the amplified signal to the gate of the transistor 2.

  The control circuit 6 performs control to change the reference value of the reference source 4 in accordance with the arrangement pattern of the communication signal in order to output a variable reference value from the reference source 4. For example, the control circuit 6 calculates a partial on-duty ratio of the communication signal. When the calculated partial on-duty ratio is the first ratio, the control circuit 6 sets the reference value to the first value, When the on-duty ratio is a second ratio larger than the first ratio, the reference value is set to a second value smaller than the first value. At this time, the control circuit 6 may change the reference value so as to be inversely proportional to the partial on-duty ratio of the communication signal. The “partial on-duty ratio” is, for example, the ratio of the on-period to the total of the off-period immediately before and the on-period immediately before the off-period. Alternatively, the “partial on-duty ratio” may be substituted with the latest n-bit moving average value of the communication signal. In this way, when the magnitude of the overshoot generated in the current flowing through the load circuit 53 depends on the partial on-duty ratio, the overshoot can be suppressed more appropriately.

[1.3 Modification of Current Suppression Circuit 1]
Next, first to third modifications of the current suppression circuit 1 will be described.

  The current suppression circuit 1 in FIG. 1A is not limited to this configuration, and may be configured as shown in FIGS.

  FIG. 2 is a circuit diagram showing a first modification of the current suppression circuit 1 in FIG. 1A. The current suppression circuit 1 shown in FIG. 2 includes bipolar transistors 11 and 12, a reference source 4, a resistor 14, and a control circuit 6. Bipolar transistors 11 and 12 constitute a current mirror circuit. The current flowing through the bipolar transistor 12 is determined by the reference source 4 and the resistor 14. The bipolar transistor 11 can pass a current within a range that does not exceed a current (that is, a current set value) that is twice the mirror ratio of this current. The control circuit 6 changes the reference source 4 or the resistor 14 in accordance with the signal arrangement of the communication signal output from the signal generation circuit SG.

  FIG. 3 is a circuit diagram showing a second modification of the current suppression circuit in FIG. 1A. The current suppression circuit 1 shown in FIG. 3 includes a bipolar transistor 21, an emitter resistor 22r, a bias resistor 23, a Zener diode 24, and a control circuit 6.

  The bipolar transistor 21 is connected in series with the load circuit 53 and suppresses the current flowing through the load circuit 53 according to the base voltage (reference value) of the bipolar transistor 21.

  The emitter resistor 22r is a resistor for detecting the magnitude of the current flowing through the load circuit 53 (that is, the current flowing through the emitter resistor 22r).

  The bias resistor 23 is a resistor for biasing the base voltage of the bipolar transistor 21.

  The Zener diode 24 outputs a reference value to the base of the bipolar transistor 21.

  The control circuit 6 changes the reference value of the Zener diode 24 according to the signal arrangement of the communication signal.

  FIG. 4 is a circuit diagram showing a third modification of the current suppression circuit in FIG. 1A. The current suppression circuit 1 shown in FIG. 4 includes a three-terminal regulator 25a, a detection resistor 26, and a control circuit 6.

  In the three-terminal regulator 25a, an input terminal IN and an output terminal OUT are connected in series with the load circuit 53, and a current flowing between the input terminal IN and the output terminal OUT according to a voltage input to the adjustment terminal ADJ. Suppress.

  The detection resistor 26 is a resistor for detecting the magnitude of the current flowing through the load circuit 53 (that is, the current flowing through the detection resistor 26). The detection resistor 26 is a variable resistor, and its resistance value is a reference value. The terminal on the intermittent switch SW side of the detection resistor 26 is connected to the adjustment terminal ADJ of the three-terminal regulator 25a.

  The control circuit 6 changes the resistance value of the detection resistor 26 according to the signal arrangement of the communication signal.

  As described above, even in the modified example of the current suppression circuit 1, when the magnitude of the overshoot depends on the partial on-duty ratio (or the partial signal arrangement), the suppression of the overshoot is made more appropriate. Can do.

  In FIG. 1A and FIGS. 2 to 4, when the reference source 4 outputs a fixed reference value, the current suppression circuit 1 may not include the control circuit 6.

[1.4 Operation of illumination light communication device]
The operation of the illumination light communication apparatus configured as described above will be described using simulation results.

  5 to 14 show the simulation results of the current suppression circuit 1 of FIG.

  FIG. 5 is a diagram showing a first simulation result for the circuit example of FIG. In FIG. 5, the capacitance value of the smoothing capacitor 65 is set to 20 uF, and the frequency and on-duty ratio of the communication signal from the signal generation circuit SG are set to 2.4 kHz and 75%. FIG. 5 shows the LED current and the voltage waveform applied to the current suppression circuit 1 when the current setting value of the current suppression circuit 1 is varied in four ways under this setting. There are four current setting values: 423 mA, 373 mA, 332 mA, and 318 mA. Incidentally, the operating frequency of the DC-DC converter is set to 65 kHz, and the average value of the load current (LED current) when not intermittent is set to 240 mA.

  In FIG. 5, when the current setting value of the current suppression circuit 1 is set to 423 mA, a large overshoot occurs in the LED current waveform, the applied voltage is extremely low, and the current suppression circuit 1 substantially functions. Not.

  When the current set value of the current suppression circuit 1 is gradually lowered to 373 mA, 332 mA, and 318 mA, the LED current overshoot is cut, and when the current set value is 318 mA, the LED current waveform overshoot disappears. Is a square wave. Along with this, the applied voltage of the current suppression circuit 1 gradually increases, and when the current set value is lowered, the current suppression circuit 1 starts to work, and at the current set value 318 mA, the current of the current suppression circuit 1 in the entire ON period. It can be seen that the suppression is functioning effectively.

  FIG. 6 is a diagram illustrating a second simulation result for the circuit example of FIG. FIG. 6 shows the LED current and the voltage waveform applied to the current suppression circuit 1 when the current setting value of the current suppression circuit 1 is further gradually decreased from 318 mA to 309 mA, 299 mA, and 289 mA in the simulation of FIG. Show. As the current set value decreases, the peak value of the LED current decreases, but a rectangular waveform without overshoot is maintained. Further, the applied voltage waveform rapidly increases as the current set value decreases.

  FIG. 7 and FIG. 8 show the above results in a diagram. FIG. 7 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 7 shows the relationship between the current setting value of the current suppression circuit 1 and the LED current. With the current setting value 318 mA as a boundary, when the setting value is large, the average value of the LED current is kept constant, but the fluctuation range (overshoot) becomes large, and when the setting value is small, the fluctuation range of the LED current (overshoot). ) Disappears, but the average value decreases. FIG. 8 is a diagram showing a fourth simulation result for the circuit example of FIG. FIG. 8 shows the relationship between the current setting value of the current suppression circuit 1 and the circuit loss that occurs in the current suppression circuit 1 (that is, the power consumption of the current suppression circuit 1). It can be seen that with the current setting value 318 mA as a boundary, the loss is suppressed to a small value when the setting value is large, and the loss increases rapidly when the setting value is small. From these results, under the simulation conditions of FIG. 5 for the circuit example of FIG. 2, if the current setting value of the current suppression circuit 1 is set to 318 mA, the overshoot of the LED current can be suppressed and the average value is not intermittent. In this case, the circuit loss of the current suppression circuit 1 can be suppressed to a low value.

  FIG. 9 is a diagram illustrating a fifth simulation result for the circuit example of FIG. FIG. 9 is a circuit diagram of FIG. 2, in which the current set value of the current suppression circuit 1 is set to 318 mA which is the optimum value under the above conditions (FIGS. 5 and 6), and the modulation from the signal generator SG is performed. The voltage waveform applied to the LED current and current suppression circuit 1 when the on-duty ratio of the signal is varied in three ways is shown. There are three on-duty ratios: 70%, 75%, and 80%. Other conditions are the same (capacitance value 20 uF of the smoothing capacitor 65, modulation signal frequency 2.4 kHz from the signal generation circuit SG, operating frequency of the DC-DC converter 65 kHz, average load current (LED current) when not intermittent Value 240 mA).

  At an on-duty ratio of 75%, no overshoot is observed in the LED current waveform, and the voltage applied to the current suppression circuit 1 is low (this is the optimum condition).

  When the on-duty ratio is 80%, the overshoot is not completely removed from the LED current waveform, causing a slope in the second half of the on-period, and the applied voltage is extremely low. It can be seen that the current suppression circuit 1 is not functioning.

  When the on-duty ratio is 70%, the LED current waveform overshoot is completely removed to form a rectangular wave, but the applied voltage increases and the loss increases.

  FIG. 10 shows the relationship between the on-duty ratio of the modulation signal from the signal generator and the LED current. FIG. 10 is a diagram illustrating a sixth simulation result for the circuit example of FIG. When the current setting value of the current suppression circuit 1 is set to 318 mA, the average value of the LED current is maintained constant when the on-duty ratio is large with the on-duty ratio of 75% as a boundary. ) Increases and the on-duty ratio is small, the fluctuation range (overshoot) of the LED current disappears, but the average value decreases.

  FIG. 11 is a diagram showing a seventh simulation result for the circuit example of FIG. FIG. 11 is a diagram showing the LED current overshoot as a ripple rate. FIG. 12 is a diagram showing an eighth simulation result for the circuit example of FIG. FIG. 12 shows the relationship between the on-duty ratio and the circuit loss of the current suppression circuit 1. From these results, it can be inferred that the optimum current setting value of the current suppression circuit 1 depends on the on-duty ratio of the communication signal from the signal generator SG.

  FIG. 13 shows the result of obtaining the optimum current setting value of the current suppression circuit 1 in accordance with the on-duty ratio of the modulation signal from the signal generator SG. FIG. 13 is a diagram illustrating a ninth simulation result for the circuit example in FIG. 2. In FIG. 13, if the current set value is varied as illustrated in accordance with the on-duty ratio of the horizontal axis, the fluctuation value (overshoot) of the LED current is suppressed, and the average value is a value when it is not intermittent. Can be maintained. The circuit loss of the current suppression circuit 1 in that case is shown in FIG. FIG. 14 is a diagram illustrating a tenth simulation result for the circuit example of FIG. In FIG. 14, it can be seen that the circuit loss is kept at a low value when the on-duty ratio is 50% to 90%.

  FIG. 15 is an explanatory diagram showing a modulation method of a communication signal. FIG. 15 shows an example of a modulation signal form used in the illumination light communication apparatus. This figure is based on the 1-4PPM transmission system defined in JEITA-CP1223. For example, a 4PPM signal of 2-bit data “00” is modulated to “1000” in one symbol period consisting of 4 slots. That is, a pulse appears in one of the four slots. In visible light communication, an inverted 4PPM signal is often used in order to ensure lighting time by lighting three of the four slots. The communication signal in the figure is a signal modulated into an inverted 4PPM signal. In this case, the high level of the communication signal turns on the intermittent switch SW and turns on the load circuit 53 as a light source. The low level of the communication signal turns off the intermittent switch SW and turns off the load circuit 53 as a light source. For example, one slot is 104.167 usec (= 1 / 9.6 kHz), and one symbol is formed by four slots (416 usec) (here, one symbol is 2 bits). The 1-4PPM signal is composed of binary values of logical values 0 and 1, and has a data array in which a logical value 1 stands in one of four slots. The communication signal generated by the signal generation circuit SG is an inverted 4PPM signal obtained by inverting this logical value. The inverted 4PPM signal modulates data depending on where a negative pulse occurs in 4 slots, and the on-duty ratio is 75% as far as 4 slots of 1 symbol are seen. However, if the symbol delimiters are ignored, the signal arrangement patterns are diversified and the partial on-duty ratios are also diversified. FIG. 16 shows an example.

  FIG. 16 is a diagram illustrating examples (1) to (4) of communication signals. Among the data for 4 symbols in the figure, a circle is added to the off period and the on period immediately before the rising of the communication signal from the low level to the high level. If you look at the partial data enclosed in the circles, the partial on-duty ratio is, for example, in the period (the latest one cycle) that combines the most recent off period and the on period just before the off period. It can be defined as the ratio of the on period. In the case (1) of FIG. 16, the frequency of the latest one cycle is 1.2 kHz, and the partial on-duty ratio is 75%. In the case (2), the frequency is 4.8 kHz and 50%, in the case (3), the frequency is 3.2 kHz and 66.7%, and in the case (4), the frequency is 2.4 kHz and 75%. That is, in the first embodiment, it has been disclosed that the optimum current setting value of the current suppression circuit 1 is varied according to the on-duty ratio. However, in applications where the partial on-duty ratio changes every moment. , It may be dynamic.

  Furthermore, as a simulation result of the circuit example shown in FIG. 2, the trend of the waveform of the LED current waveform and the voltage applied to the current suppression circuit 1 in the four cases shown in the cases (1) to (4) of FIG. The results of examining are shown in FIGS.

  FIG. 17 is a diagram showing a simulation result (part 1) of the case (2) of FIG. 16 (1.2 kHz, partial on-duty ratio 75%). FIG. 18 is a diagram showing a simulation result (part 2) of the case (1) of FIG.

  In FIG. 17, when the current setting value of the current suppression circuit 1 is 676 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 318 mA, the LED current overshoot disappears and the applied voltage of the current suppression circuit 1 rises to a peak of about 3V.

  FIG. 18 shows the result when the current set value is further lowered with respect to FIG. The LED current maintains a rectangular wave, but the current value gradually decreases. Further, when the current set value is further lowered, the voltage applied to the current suppression circuit 1 rapidly increases, and the current set value exceeds 20 V at 289 mA.

  FIG. 19 is a diagram showing a simulation result (part 1) of the case (2) of FIG. 16 (4.8 kHz, on-duty ratio 50%). FIG. 20 is a diagram showing a simulation result (part 2) of the case (2) of FIG.

  In FIG. 19, when the current setting value of the current suppression circuit 1 is 558 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 475 mA, the LED current overshoot disappears and the applied voltage of the current suppression circuit 1 rises to a peak of about 1.2V.

  FIG. 20 shows the result when the current set value is further lowered with respect to FIG. The LED current maintains a rectangular wave, but the current value gradually decreases. In addition, the voltage applied to the current suppression circuit 1 rises rapidly, and the current set value exceeds 30 V at 407 mA.

  FIG. 21 is a diagram showing a simulation result (part 1) of the case (3) in FIG. 16 (3.2 kHz, on-duty ratio 66.7%). FIG. 22 is a diagram showing a simulation result (part 2) of the case (3) of FIG.

  In FIG. 21, when the current setting value of the current suppression circuit 1 is 463 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current setting value is lowered to 357 mA, the LED current overshoot disappears, and the applied voltage of the current suppression circuit 1 rises to a peak of about 1.4V. The result when the current set value is further lowered is shown in FIG. The LED current maintains a rectangular wave, but the current value gradually decreases. Further, the voltage applied to the current suppression circuit 1 rises rapidly, and the current set value exceeds 22 V at 320 mA.

  FIG. 23 is a diagram showing a simulation result (part 1) of the case (4) in FIG. 16 (2.4 kHz, on-duty ratio 75%). FIG. 24 is a diagram showing a simulation result (part 2) of the case (4) in FIG.

  In FIG. 23, when the current setting value of the current suppression circuit 1 is 429 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 318 mA, the LED current overshoot disappears, and the applied voltage of the current suppression circuit 1 rises to a peak of about 1.4V. The result when the current set value is further lowered is shown in FIG. The LED current maintains a rectangular wave, but the current value gradually decreases. Further, the voltage applied to the current suppression circuit 1 rises rapidly, and the current setting value exceeds 20 V at 289 mA.

  FIGS. 25A to 25C, FIGS. 26A to 26C, FIGS. 27A to 27C, and FIGS. 28A to 28C are diagrams in which the results described with reference to FIGS. 17 to 24 are summarized.

  FIG. 25A, FIG. 26A, FIG. 27A, and FIG. 28A show the current setting value and the LED current (average value and fluctuation value) as simulation results of the cases (1), (2), (3), and (4) in FIG. It is a figure which shows the relationship.

  FIG. 25B, FIG. 26B, FIG. 27B, and FIG. 28B show the relationship between the current setting value and the ripple rate of the LED current as simulation results of the cases (1), (2), (3), and (4) in FIG. FIG.

  25C, FIG. 26C, FIG. 27C, and FIG. 28C are diagrams showing the relationship between the current set value and the circuit loss as simulation results of the cases (1), (2), (3), and (4) in FIG. is there.

  These figures show the relationship between (A) the current setting value and the average value and fluctuation value of the LED current, (B) the current setting value and the LED current ripple rate, and (C) the current setting value and the loss of the current suppression circuit 1. ing. From these results, the optimum current setting value of the current suppression circuit 1 is about 475 mA when the on-duty ratio is 50%, about 357 mA when the on-duty ratio is 66.7%, and when the on-duty ratio is 75%. Is found to be about 318 mA.

  Next, the optimum current setting value of the current suppression circuit 1 will be described according to the partial on-duty ratio of the communication signal from the signal generator SG. The power supply circuit 52a which is the premise of the illumination light communication apparatus in the present embodiment has a constant current feedback function as already described. A typical example is a constant current feedback circuit 67 using an amplifier as shown in FIG. Usually, a phase compensation circuit for ensuring the stability of the feedback system is added. In such a phase compensation circuit, a compensation circuit including an integration element is used in order to adjust the gain and phase in the round transfer function, which is known as PI control or PID control. In other words, such a phase compensation circuit is a means for controlling the average value of the output to be constant. Based on this point, FIG. 29A is an explanatory diagram showing an ideal waveform of the intermittent LED current. Looking at the intermittent waveform of the LED current shown in FIG. 29A, the average value Iave of this waveform is expressed by the following equation (1).

    Iave = Iop × ONd (1)

  Here, Iop is the peak value of the LED current. ONd is an on-duty ratio and is represented by 100 × Ton / T (%).

  The average value Iave is controlled by the constant current feedback function so as to be the same as the average current when not interrupted, and is controlled to be a constant value even if the on-duty ratio is changed. That is, as the on-duty ratio decreases, the peak value Iop increases so that Iave becomes a constant value. If this peak value Iop is set as the current setting value of the current suppression circuit 1, the LED current waveform becomes a rectangular wave, so that an overshoot can be removed and a so-called optimum value can be obtained that can also suppress the loss of the current suppression circuit 1 ( (See equation (2)).

  Optimum current setting value = Iave / ONd (2)

  Here, Iave is the average LED current when no interruption is applied.

  FIG. 29B shows the optimum current setting value for each partial on-duty ratio using equation (2) under the condition that the average LED current when not intermittent is 240 mA. It can be seen that this agrees well with the optimum current setting value for each partial on-duty ratio shown in the above discussion.

  According to this, the brightness of the illumination light when the LED light overshoot is suppressed and the illumination light is not modulated, and the brightness of the illumination light when the illumination light is modulated are apparent to humans. It can be made almost equivalent.

[1.5 Configuration Example of Communication Module 10]
Next, the configuration of the removable communication module 10 will be described.

  FIG. 1B is a circuit diagram showing a configuration of a lighting device to which communication module 10 is not added in the first embodiment. That is, FIG. 1B shows a configuration in which the communication module 10 is deleted and the short line S10 is added in the illumination light communication apparatus of FIG. 1A. The illumination light communication apparatus in FIG. 1A represents an illumination apparatus having a visible light communication function. FIG. 1B shows a lighting device that does not have a visible light communication function.

  The communication module 10 or the short line S10 is connected to the terminals T1 and T2 in FIGS. 1A and 1B. The terminals T1 and T2 may be terminal blocks or connectors, or portions of the wiring in the existing lighting device where the wiring material corresponding to the short line S10 in FIG. 1B is cut may be used as the terminals T1 and T2.

  According to the configuration as shown in FIGS. 1A and 1B, a simple circuit portion (that is, the communication module 10) is retrofitted using the power supply circuit and the LED light source mounted in an existing lighting fixture without an optical communication function. An optical communication function can be added by adding in.

[1.6 Modification of Illumination Optical Communication Device]
Next, a modification of the illumination light communication device will be described.

  FIG. 30A is a circuit diagram showing a modification of the illumination light communication apparatus in the first embodiment. The illumination light communication apparatus of the figure is different from that of FIG. 1A in the circuit configuration inside the power supply circuit 52a. Hereinafter, different points will be mainly described.

  In the power supply circuit 52a in FIG. 1A, feedback control is performed to make the average value of the output current constant by the constant current feedback circuit 67, whereas in the power supply circuit 52a in FIG. 30A, switching current threshold control is performed. Configured to do.

  30A includes a rectifier bridge 62, a capacitor 63, and a DC-DC converter 64. The DC-DC converter 64 includes an inductor 80, a switch element 81, a diode 66d, a resistor 82, a signal source 83, a flip-flop 84, a comparator 85, a constant voltage source 86, a capacitor 87, a resistor 88, a diode 89, a driver 90, and a gate resistor. 91 is provided.

  The inductor 80, the switch element 81, and the diode 66d are basic circuit elements that constitute the DC-DC converter 64 as a buck converter.

  Control for turning on and off the switch element 81 is performed by the signal source 83, the flip-flop 84, the comparator 85, and peripheral circuits, and threshold control of the switching current of the switch element 81 is performed. That is, the switching current is also a current through the load circuit 53 (light emitting diode), and an alternative function of constant current feedback can be obtained by threshold control. The operation of such a DC-DC converter 64 will be described with reference to FIG. 30B.

  FIG. 30B is a waveform diagram showing threshold control of the switching current in the power supply circuit 52a of FIG. 30A. However, FIG. 30B shows a case where the terminals T1 and T2 are short-circuited in FIG. 30A, or when the communication module 10 is connected to the terminals T1 and T2 and the intermittent switch SW is kept on. The waveform is shown.

  In FIG. 30B, the set signal S is a signal input from the signal source 83 to the set input terminal S of the flip-flop 84. The positive input signal is a signal input to the positive input terminal of the comparator 85 and indicates the voltage drop of the resistor 82, that is, the magnitude of the current flowing through the switch element 81. The reset signal R is a signal input to the reset input terminal of the flip-flop 84. The output signal Q is a signal output from the output terminal Q of the flip-flop 84. The output signal Q becomes a gate signal of the switch element 81 through the driver 90 and the resistor 91. The switching current is a current flowing through the switch element 81 and is detected as a voltage drop of the resistor 82.

  The set signal is generated by the signal source 83 and periodically goes high. When the set signal S goes high, the output signal Q of the RS flip-flop 84 goes high. The output signal Q is input to the gate of the switch element 81 (MOSFET) via the driver circuit 90 and the gate resistor 91. The switch element 81 is turned on when the output signal Q becomes high.

  The magnitude of the switching current (current flowing through the switch element 81) is detected as a voltage drop of the resistor 82, input to the positive input terminal of the comparator 85, and compared with the reference voltage Vref applied to the negative input terminal of the comparator 85. The When the voltage drop reaches the reference voltage Vref, the output of the comparator 85 becomes high, is converted into a pulse by a differentiation circuit composed of a capacitor 87 and a resistor 88, and is input to the reset input terminal of the RS flip-flop 84. At this time, the output signal Q of the flip-flop 84 becomes low and the switch element 81 is turned off. The detection of the magnitude of the current flowing through the switch element 81 as the switching current is an alternative to detecting the magnitude of the current flowing through the load circuit 53.

  Such switching current threshold control substitutes for the constant current feedback control of FIG. 1A and works to make the average of the output current constant. Accordingly, also in FIG. 30A, as in FIG. 1A, if there is no current suppression circuit 1, the problem of overshoot described in the problem column occurs. However, in the configuration of FIG. 30A, the overshoot can be reduced by providing the current suppression circuit 1 as in FIG. 1A.

  Note that the power supply circuit 52a may perform the constant current feedback control of FIG. 1A or the switching current threshold control of FIG. 30A. Moreover, since the current suppression circuit 1 has a function of reducing overshoot, it is effective if it is a power supply circuit that can cause overshoot by turning on / off the intermittent switch SW.

(Embodiment 2)
In the second embodiment, a configuration in which the reference value (and thus the current set value) is made variable in an analog circuit manner in the current suppression circuit 1 will be described. In the first embodiment, the reference value is changed according to the on-duty ratio. In the second embodiment, the reference value is changed according to the voltage applied to the current suppression circuit 1 immediately before the intermittent switch SW is turned on. The point to be different is. That is, a voltage applied to the current suppression circuit 1 is used instead of the on-duty ratio. The LED current overshoot increases as the on-duty ratio increases. Further, as shown in FIG. 51, the LED current overshoot increases as the output voltage (corresponding to the voltage applied to the current suppression circuit 1) increases. Therefore, in the second embodiment, the voltage applied to the current suppression circuit 1 is substituted for the on-duty ratio.

  The illumination light communication apparatus according to the second embodiment has substantially the same configuration as that in FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, different points will be mainly described.

  A configuration example of the current suppression circuit 1 in the second embodiment is shown in FIGS. 31A and 31B.

  The current suppression circuit 1 shown in FIG. 31A includes a transistor 2 that is a MOSFET 2, a resistor 3 connected to the source, a constant voltage source 4a, voltage dividing resistors R1 and R2, a capacitor C1, and a diode D. The In addition, the current suppression circuit 1 shown in FIG. 31B includes bipolar transistors 11 and 12, a constant voltage source 13, voltage dividing resistors R1 and R2, a noise preventing capacitor C1, and a current limiting resistor 14. It is composed of a diode D.

  In FIG. 31A, the voltage of the constant voltage source 4 is divided by resistors R1 and R2, and connected to a point via the gate terminal of the transistor 2 and the resistor 3 via the capacitor C1. A diode D is connected from the drain terminal of the transistor 2 toward the voltage dividing point by the resistors R1 and R2. In FIG. 31B, the bipolar transistors 11 and 12 form a current mirror, the voltage of the constant voltage source 13 is divided by the resistors R1 and R2, and the collector terminal and the base terminal are short-circuited through the capacitor C1 and the resistor 14. A reference current is passed through the bipolar transistor 12. A diode D is connected from the collector terminal of the bipolar transistor 11 toward the voltage dividing point of the resistors R1 and R2. In these configurations, when the optimum current set value of the current suppressing circuit 1 is obtained according to the on-duty ratio of the modulation signal from the signal generator SG, the current source is not directly controlled but the current set value is set. Is fed back to the voltage dividing point of the reference source using the voltage applied to the current suppressing circuit 1 generated when the current is inappropriate.

  The resistors R1 and R2 and the diode D in FIGS. 31A and 31B correspond to the control circuit 6 that changes the reference value in FIG. 1A.

  The operation of FIG. 31A in Embodiment 2 of the present invention will be described using simulation results. The main setting conditions in the simulation are: the capacitance value of the smoothing capacitor is 20 uF, the modulation signal frequency from the signal generation circuit is 2.4 kHz, the operating frequency of the DC-DC converter is 65 kHz, and the load current (LED current) when not intermittent The average value is set to 240 mA.

  32A, 32B, 33A, 33B, and 34 show the simulation results. FIGS. 32A and 32B show simulation results when the diode D as a feedback circuit is removed in order to see the feedback effect by the diode D shown in FIGS. 31A and 31B. Since the current suppression circuit 1 is set to function at an on-duty ratio of 90% or less when the on-duty ratio of the modulation signal from the signal generator SG is in the range of 50% to 90%, fluctuations in the LED current The value (overshoot) is removed over the entire on-duty ratio (see FIG. 32B), but the average value of the LED current decreases as the on-duty ratio decreases. Furthermore, as shown in FIG. 34, the current suppression circuit 1 loss increases remarkably as the on-duty ratio decreases (see the diagram without a diode). 33A and 33B show results when a feedback circuit using a diode D is added. When the on-duty ratio is 50% to 90%, the fluctuation value (overshoot) of the LED current is suppressed to a small value, and the average value is maintained at a value when it is not intermittent. Further, as shown in FIG. 34 (with a diode), it can be seen that the loss of the current suppression circuit 1 is significantly reduced as compared with the case where there is no feedback circuit by the diode D.

(Embodiment 3)
Also in the third embodiment, a configuration in which the reference value (and thus the current set value) is made variable in an analog circuit manner in the current suppression circuit 1 as in the second embodiment will be described.

  The illumination light communication apparatus according to Embodiment 3 has substantially the same configuration as that in FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, different points will be mainly described.

  FIG. 35A is a diagram illustrating a configuration example of the current suppression circuit 1 in the third embodiment. The current suppression circuit 1 shown in FIG. 35A includes a bipolar transistor 2, a resistor 3 connected to an emitter, a reference source 4, voltage dividing resistors R1 and R2, a capacitor C1, and an amplifier as a voltage follower circuit. 5, a base resistor Rb, a diode D, and a resistor R3.

  In FIG. 35A, the constant voltage source 4a is divided by resistors R1 and R2, and connected to the positive input terminal of the voltage follower using the amplifier 5 via the capacitor C1. The output terminal of the amplifier 5 is connected to the negative input terminal, and is connected to the base terminal of the transistor 2 through the base resistor Rb, and supplies a drive voltage to the point through the base terminal and the resistor 3. A diode D is connected from the collector terminal of the transistor 2 toward the voltage dividing point by the resistors R1 and R2. In this configuration, when the optimum current setting value of the current suppression circuit 1 is obtained according to the on-duty ratio of the modulation signal from the signal generator, the reference source is not directly controlled, but the current setting value is not valid. The applied voltage of the current suppressing circuit 1 generated when appropriate is fed back to the voltage dividing point of the reference source. The difference from FIGS. 31A and 31B showing the second embodiment is that the amplifier 5 is used. The voltage follower was added.

  Note that the resistors R1, R2, and R3 and the diode D in FIG. 35A correspond to the control circuit 6 that changes the reference value in FIG. 1A.

  36 to 38 are diagrams showing simulation results for verifying the operation of the current suppression circuit 1 of FIG. 35A. As the main setting conditions for the simulation, the capacitance value of the smoothing capacitor 65 is 20 uF, the modulation signal frequency from the signal generation circuit SG is 2.4 kHz, the operating frequency of the DC-DC converter is 65 kHz, and the load current (LED current when not intermittent) ) Is set to 240 mA. FIG. 36 shows the peak value, average value, and fluctuation value of the LED current when the on-duty ratio of the intermittent switch SW is changed in the range of 50% to 90%. The fluctuation value (overshoot) of the LED current is almost eliminated, and the average value is maintained at a value when it is not intermittent. FIG. 37 shows the fluctuation value (overshoot) of the LED current as a ripple rate, and it can be seen that the overshoot is also removed from here. FIG. 38 shows the relationship between the on-duty ratio and the current suppression circuit 1 loss. The circuit loss is maintained at a low value with respect to the change of the on-duty ratio.

(Embodiment 4)
In the fourth embodiment, a configuration in which the reference value (and thus the current set value) is made variable in an analog circuit manner in the current suppression circuit 1 as in the second embodiment will be described.

  The illumination light communication apparatus according to the fourth embodiment has substantially the same configuration as that in FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, different points will be mainly described.

  FIG. 35B is a diagram illustrating a first configuration example of the current suppression circuit 1 in the fourth embodiment. The current suppression circuit 1 shown in FIG. 35B includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a constant voltage source 4a, voltage dividing resistors R1 and R2, a capacitor C1, an amplifier 5, and a diode. D and resistor R3.

  In FIG. 35B, the constant voltage source 4a is divided by resistors R1 and R2, and is connected to the plus input terminal of the amplifier 5 via the capacitor C1. The negative input terminal of the amplifier 5 is connected to the connection point between the transistor 2 and the resistor 3, the output terminal of the amplifier 5 is connected to the gate terminal of the transistor 2, and the drive voltage is connected between the gate terminal and the point through the resistor 3. Is supplied. Further, a diode D is connected from the drain terminal of the transistor 2 toward the voltage dividing point by the resistors R1 and R2 via the adjusting resistor R3. These configurations do not directly control the reference source when obtaining the optimum current setting value of the current suppression circuit 1 according to the on-duty ratio of the modulation signal from the signal generator. The applied voltage of the current suppression circuit 1 generated when it is inappropriate is fed back to the voltage dividing point of the reference voltage. The difference from FIG. 31A in the second embodiment is that the amplifier 5 is added. is there.

  39 to 41 are diagrams showing simulation results for verifying the operation of FIG. 35B. The main setting conditions for the simulation are a capacitance value of the smoothing capacitor of 20 uF, a modulation signal frequency from the signal generation circuit of 2.4 kHz, an operating frequency of the DC-DC converter of 65 kHz, and a load current (LED current) when not intermittent The average value is set to 240 mA. 39 to 41 show simulation results. FIG. 39 shows the peak value, average value, and fluctuation value of the LED current when the on-duty ratio of the intermittent switch SW is changed in the range of 50% to 90%. The fluctuation value (overshoot) of the LED current is almost eliminated, and the average value is maintained at a value when it is not intermittent. FIG. 40 shows the fluctuation value (overshoot) of the LED current as a ripple rate, and it can be seen that the overshoot is substantially removed from this. FIG. 41 shows the relationship between the on-duty ratio and the current suppression circuit 1 loss. The circuit loss is maintained at a low value with respect to the change of the on-duty ratio.

  39 to 41, the LED current ripple is slightly larger than that of the simulation results of the third embodiment (FIGS. 36 to 38), and somewhat unstable operation was observed.

  An example for achieving a more stable operation accompanying the third and fourth embodiments is shown in FIGS. 35C and 35D. FIG. 35C is a diagram illustrating a second configuration example of the current suppression circuit in the fourth embodiment. In FIG. 35C, an amplifier 5a having a voltage follower and a diode Da are added between the voltage dividing points of the resistors R1 and R2 and the positive input terminal of the amplifier 5, and the filter circuit formed by the capacitor C1 and the resistor R4 is added to the filter circuit. An impedance conversion circuit is added so as not to be affected by the resistors R1, R2, R3 and the like.

  FIG. 35D is a diagram illustrating a third configuration example of the current suppression circuit in the fourth embodiment. In FIG. 35D, a ripple filter formed by a transistor Tr, a resistor R5, and a capacitor C3 is added between the voltage dividing points of the resistors R1 and R2 and the plus input terminal of the amplifier 5, thereby suppressing the pulsating voltage of the plus input terminal of the amplifier 5. It is a thing.

(Embodiment 5)
Also in the fifth embodiment, a configuration in which the reference value (and thus the current set value) is made variable in an analog circuit manner in the current suppression circuit 1 as in the second embodiment will be described.

  The illumination light communication apparatus of the fifth embodiment has substantially the same configuration as FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, different points will be mainly described.

  FIG. 35E is a diagram illustrating a configuration example of the current suppression circuit in the fifth embodiment. 35E includes a transistor 2 that is a MOSFET, a resistor 3 connected to a source, a reference source 4, voltage dividing resistors R1 and R2, a capacitor C1, an amplifier 5, and the amplifier. 5, a resistor Rg, a capacitor Cp, a resistor Rp, a diode D, and a resistor R3, which are provided between the output terminal 5 and the positive input terminal.

  In FIG. 35E, the reference source 4 is divided by resistors R1 and R2, and is connected to the positive input terminal of the amplifier 5 via the capacitor C1. The negative input terminal of the amplifier 5 is connected to the connection point between the transistor 2 and the resistor 3, and the output terminal of the amplifier 5 is connected to the gate terminal of the transistor 2, and between the gate terminal and the point through the resistor 3. A drive voltage is supplied. A diode D is connected from the drain terminal of the MOSFET toward the voltage dividing point by the resistors R1 and R2 via the adjusting resistor R3. Further, a resistor Rg for gain adjustment is connected between the output terminal and the negative input terminal of the operational amplifier, and a phase compensation circuit including a capacitor Cp and a resistor Rp is added in parallel with the resistor Rg.

  42 to 44 are diagrams showing simulation results for verifying the operation of the current suppression circuit 1 of FIG. 35E. The main setting conditions for the simulation are a capacitance value of the smoothing capacitor of 20 uF, a modulation signal frequency from the signal generation circuit of 2.4 kHz, an operating frequency of the DC-DC converter of 65 kHz, and a load current (LED current) when not intermittent The average value is set to 240 mA. FIG. 42 shows the peak value, average value, and fluctuation value of the LED current when the on-duty ratio of the intermittent switch SW is changed in the range of 50% to 90%. The fluctuation value (overshoot) of the LED current is almost eliminated, and the average value is maintained at a value when it is not intermittent. FIG. 43 shows the fluctuation value (overshoot) of the LED current as a ripple rate, and it can be seen that the overshoot is almost removed from this. FIG. 44 shows the relationship between the on-duty ratio and the current suppression circuit 1 loss. The circuit loss is maintained at a low value with respect to the change of the on-duty ratio.

  42 to 44, the LED current ripple rate is improved and a more stable operation is obtained as compared with the simulation results of the fourth embodiment (FIGS. 39 to 41).

(Embodiment 6)
The current suppression circuit 1 according to the second to fifth embodiments is configured to make the reference value (and thus the current set value) variable in an analog circuit, whereas in the sixth embodiment, the reference value (in a digital circuit) Next, the current suppression circuit 1 that makes the current setting value) variable will be described.

  The illumination light communication apparatus of the fifth embodiment has substantially the same configuration as FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, different points will be mainly described.

  FIG. 35F is a diagram illustrating a configuration example of a current suppression circuit in the sixth embodiment. 35F includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 4, a microcomputer (that is, a CPU 7c), voltage dividing resistors R1, R6, R7, and R8. The switches S01 to S03 for switching the voltage dividing ratio, the amplifier 5, and the resistor R3.

  In FIG. 35F, the voltage applied to the current suppression circuit 1 (transistor 2 and resistor 3) is input to the microcomputer (CPU 7c) via the resistor R3. The constant voltage source 4a is connected to the plus input terminal of the amplifier 5 via the resistor R1, and the voltage dividing resistors R6 to R8 and the changeover switches S01 to S03 are connected between the connection point and the minus end of the reference voltage. . The microcomputer calculates an appropriate reference voltage value according to the voltage between the current suppression circuits 1 or selects it from a correspondence table constructed in advance, and switches the changeover switches S01 to S03. These configurations can be said to be methods in which a part of the above-described Embodiments 3 to 5 is digitized.

  Note that the resistors R1 and R3, the diodes D, R6 to R8, the switches S01 to S03, and the CPU 7c in FIG. 35F correspond to the control circuit 6 that changes the reference value in FIG. 1A.

(Comparative reference example)
Subsequently, in order to confirm the effect of the current suppression circuit 1 in each embodiment, a comparative reference example without the current suppression circuit 1 will be described.

  FIG. 45 is a diagram showing an illumination light communication device as a comparative reference example in which the current suppression circuit 1 is deleted from FIG. 1A. The illumination light communication apparatus shown in the figure is different from that shown in FIG. 1A in that the current suppression circuit 1 is not provided and the load circuit 53 that is a light source and the intermittent switch SW are directly connected. Since the illumination light communication apparatus of the comparative reference example does not include the current suppression circuit 1, it does not have a function of suppressing the current flowing through the light source so as not to exceed the current set value.

  The simulation results of the comparative reference example shown in FIG. 45 will be described with reference to FIGS. 46 to 49B.

  FIG. 46 is a diagram showing LED current and output voltage waveforms when the on-duty ratio is 60%, 75%, 90%, and 100%, as a simulation result of the comparative reference circuit of FIG. In this simulation, the capacity of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal for driving the intermittent switch SW is 2.4 kHz. As shown in the figure, the LED current overshoot increases as the on-duty ratio decreases. In addition, the voltage waveform also fluctuates but is not as severe as the current fluctuation, indicating that the operating resistance of the LED load is low.

FIG. 47 is a simulation result of the LED current waveform and the output voltage waveform when the frequency of the modulation signal is 2.4 kHz, the ON-Duty is 75%, and the capacitance of the output smoothing capacitor is changed from 10 to 30 uF. It can be seen that the LED current overshoot increases as the smoothing capacitor capacity decreases. FIG. 48A, FIG. 48B, FIG. 49A, and FIG. 49B represent the above simulation results in a diagram. Even if the horizontal axis ON-Duty changes, the average value of the LED current does not change and the constant current feedback control (averaging control) functions. However, the peak value becomes larger as the ON-Duty is smaller. The fluctuation range in the figure represents the magnitude of the overshoot of the LED current, and is also indicated by the ripple rate. For example, comparing FIGS. 10 to 14 of the first embodiment with FIGS. 48A, 48B, 49A, and 49B of the comparative reference examples, the LED current overshoot is well reduced in the embodiment. I understand.

  As described above, the illumination light communication apparatus according to Embodiments 1 to 6 includes the light source 53 that emits illumination light, the switch SW that is connected in series with the light source, and that interrupts the current flowing through the light source, and the illumination light. A signal generation circuit SG for generating a binary communication signal for controlling on and off of the switch SW for modulation, and the light source and the switch are connected in series so as not to exceed a variable current set value. And a current suppression circuit 1 that suppresses a current flowing through the light source.

  According to this, it is possible to reduce the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the intermittent switch SW is turned on from the off state, thereby reducing the reception error in the receiving device. .

  Here, the current suppression circuit 1 is connected in series with a reference source 4 that outputs a variable reference value corresponding to the current set value, the light source and the switch, and the current flowing through the light source is set to the reference value. The transistor 2 to be suppressed based on the calculated partial on-duty ratio of the communication signal, and when the calculated partial on-duty ratio is the first ratio, the reference value is set to the first value, And a control circuit 6 that sets the reference value to a second value smaller than the first value when a typical on-duty ratio is a second ratio larger than the first ratio, The corresponding current set value may be smaller than the current set value corresponding to the first value.

  According to this, when the magnitude of the overshoot depends on the partial on-duty ratio, it is possible to appropriately suppress the overshoot.

  Here, the control circuit 6 may change the reference value so that the current set value is inversely proportional to the partial on-duty ratio.

  Here, the control circuit 6 may change the reference value so as to satisfy the following expression.

      I1 = (Iave / ONd) × 100

  Here, I1 is the current setting value, Iave is an average current flowing through the light source when the illumination light is not modulated by the switching of the switch, and ONd is a partial on-duty ratio ( The unit is%).

  According to this, the brightness of the illumination light when the overshoot is suppressed and the illumination light is not modulated is substantially equal to the brightness of the illumination light when the illumination light is modulated. Can be.

  Here, the control circuit 6 may change the reference value so as to satisfy the following expression.

  (Iave / ONd) × 100 ≦ I1 <Ip

  Here, Iave is an average current flowing through the light source when illumination light is not modulated by the on / off of the switch, ONd is a partial on-duty ratio of the communication signal, and I1 is the current set value. Yes, Ip is the peak value of the current flowing through the light source when the current suppression circuit does not suppress.

  Here, the current suppression circuit 1 is connected in series with a reference source 4 that outputs a variable reference value corresponding to the current set value, the light source and the switch, and the current flowing through the reference source 4 and the light source is supplied to the reference source. The reference source 4 includes a constant voltage source 4a that generates a constant voltage, two resistors (R1 and R2) that divide the constant voltage, and the current suppression circuit 1. A diode (D) that feeds back the voltage applied to the connection point between the two resistors, and a capacitive element (C1) that holds the potential at the connection point as the reference value. May be configured to indicate the reference value.

  According to this, since the overshoot generated in the current flowing through the light source is reduced at the moment when the switch is turned on from the off state, the reception error in the receiving device can be reduced. This is because when the power supply circuit of the illumination light communication device is a current feedback type, the magnitude of the overshoot depends on the partial on-duty ratio, and the output voltage gradually increases during the off period. Yes. Due to the feedback of the diode, the reference value also increases in accordance with the output voltage that gradually increases during the off period, so that overshoot can be appropriately reduced.

  Here, the transistor 2 is a field effect transistor, and the current suppression circuit 1 is connected to the source of the transistor 2 and has a source resistance connected in series with the transistor 2 and the switch SW, an output terminal, and a minus An amplifier 5 having an input terminal and a positive input terminal, the output terminal being connected to the gate of the transistor 2, the negative input terminal being connected to a connection point between the transistor 2 and the source resistor, The input terminal may be connected to a connection point between the two resistors and the capacitive element.

  Here, the transistor 2 is a bipolar transistor, and the current suppression circuit 1 is connected to an emitter of the transistor 2, an emitter resistor connected in series with the transistor and the switch, an output terminal, a negative input terminal, and An amplifier 5 having a positive input terminal, wherein the output terminal is connected to a base of the transistor, the negative input terminal is connected to a connection point between the transistor and the emitter resistor and the capacitive element, and the positive input terminal May be connected to a connection point between the two resistors.

  Here, the current suppression circuit 1 may include a gain adjustment circuit added to the amplifier 5 and a phase compensation circuit added to the amplifier 5.

  Here, the current suppression circuit 1 may further include a voltage follower circuit inserted between a connection point between the two resistors and the positive input terminal.

  Here, the control circuit 6 may include a detection unit that detects a voltage applied to the current suppression circuit 1 and a CPU that determines the reference value according to the detected voltage.

  Here, the illumination light communication apparatus includes a power supply circuit 52a that supplies current to the light source, the switch, and the current suppression circuit 1 connected in series, and the power supply circuit 52a calculates an average value of the supplied current. You may perform feedback control for making it constant.

  Here, the power supply circuit 52a includes a DC-DC converter 64 having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switch element 81, and according to the difference between the detected value and a predetermined value. The switch element 81 may be turned on and off.

  In addition, the communication module according to Embodiments 1 to 6 is a communication module 10 that modulates illumination light that can be attached to and detached from the illumination device, the switch SW connected in series with the light source of the illumination device, and the illumination A signal generation circuit SG for generating a binary communication signal for controlling on and off of the switch to modulate light, and the light source and the switch are connected in series so as not to exceed a variable current set value. And a current suppression circuit 1 that suppresses a current flowing through the light source.

  According to this, the communication module can be added to an existing lighting fixture. In other words, the existing lighting fixture can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than the case of installing a new optical communication lighting fixture. Further, since the overshoot generated in the current flowing through the light source is reduced at the moment when the switch is turned on from the off state, the reception error in the receiving device can be reduced.

(Embodiment 7)
In the seventh embodiment, an illumination optical communication device and a communication module that are less likely to cause a reception error of the reception device and are suitable for cost reduction even when performing 100% modulation optical communication using a constant current feedback type power supply. provide.

  One form of the illumination light communication apparatus according to the present embodiment is an illumination light communication apparatus that modulates illumination light according to a communication signal, a light source that emits the illumination light, a transistor connected in series with the light source, A signal generation circuit that generates the binary communication signal; and a dual control circuit that causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source. The dual-purpose control circuit is also a modification of the current suppression circuit already described.

  One embodiment of a communication module according to the present embodiment is a communication module that modulates illumination light that can be attached to and detached from the illumination device, and includes a transistor that is connected in series with the light source of the illumination device, a binary A signal generation circuit that generates the communication signal; and a dual-purpose control circuit that causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

  According to the illumination optical communication device and the communication module according to the present embodiment, there is an effect that it is difficult to cause a reception error of the receiving device even when optical communication with 100% modulation is performed using a constant current feedback power source. . In addition, since the transistor is also used as a switching element that performs the modulation operation and a current suppression element that performs the suppression operation, an increase in circuit elements can be suppressed, which is suitable for cost reduction. .

[7.1 Configuration of Illumination Optical Communication Device]
First, the configuration of the illumination light communication apparatus according to the seventh embodiment will be described.

  FIG. 50A is a circuit diagram showing a configuration example of the illumination light communication apparatus in the seventh embodiment. The illumination light communication device includes a power supply circuit 52 a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and the communication module 10. The communication module 10 includes a transistor 2 and a dual control circuit 1b.

  The power supply circuit 52 a includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64, a detection resistor 66, and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

The power supply circuit 52a performs full-wave rectification on a commercial power supply (for example, AC 100V) with a rectifier bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected across the output of the DC-DC converter 64. In parallel with the smoothing capacitor 65, a load circuit 53, a dual-purpose control circuit 1b, and a series circuit of the transistor 2 are connected.

  The power supply circuit 52a has a function of detecting the current flowing through the load circuit 53 directly or indirectly and controlling the current value to be constant. This function is based on the detection resistor 66 and the constant current feedback circuit 67 for directly detecting the current of the load circuit 53 in FIG. 50A. The constant current feedback circuit 67 includes an amplifier 69, a reference voltage source 72 connected to the positive input terminal of the amplifier 69, an input resistor 68 connected to the negative input terminal of the amplifier 69, an output terminal of the amplifier 69, and the amplifier 69. Gain adjustment resistor 71 and phase compensation capacitor 70 connected between the negative input terminals. The constant current feedback circuit 67 compares the voltage drop of the detection resistor 66 with the voltage of the reference voltage source 72 by the amplifier 69, amplifies the difference, and feeds back to the control unit of the DC-DC converter 64. That is, negative feedback control is applied to the DC-DC converter 64 so that the voltage drop of the detection resistor 66 matches the reference voltage. Further, the gain is set by the voltage dividing ratio of the resistor 71 connected between the inverting input terminal and the output terminal of the amplifier 69 and the input resistor 68, and the capacitor 70 provided in parallel with the resistor 71 is integrated for phase compensation. Acts as an element.

  The smoothing capacitor 65 is connected between the outputs of the power supply circuit 52a and smoothes the output of the power supply circuit 52a.

  The load circuit 53 includes a plurality of light emitting diodes connected in series between the outputs of the power supply circuit 52a, and the output of the power supply circuit is supplied. The plurality of light emitting diodes are light sources that emit illumination light.

The transistor 2 is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect
Transistor) and is connected in series with the load circuit 53. This transistor 2 is used for the operation of modulating the illumination light and the operation of suppressing the current flowing through the light source (that is, the load circuit 53). Here, the modulation operation is modulation of illumination light, and is based on intermittent current supplied from the power supply circuit 52 a to the load circuit 53 in the transistor 2. The suppression operation refers to suppressing the current flowing through the light source and the transistor 2 so as not to exceed the current set value.

  The dual-purpose control circuit 1b allows the transistor 2 to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source. Therefore, the dual-purpose control circuit 1b includes a signal generation circuit SG, a switch SW, a reference source 4, a control circuit 6, a resistor R5, a resistor R6, and an amplifier 7.

  The signal generation circuit SG generates a binary communication signal for controlling on and off of the transistor 2 in order to modulate the illumination light. The communication signal is not directly input to the gate of the transistor 2 but is indirectly input to the control terminal of the transistor 2 via the switch SW and the amplifier 7 to indirectly turn on and off the transistor 2. The communication signal modulation method may be the same as that in FIG.

  The switch SW is, for example, a switching transistor. A binary communication signal from the signal generation circuit SG is input to the gate or base of the switch SW, and the switch SW is turned on and off according to the communication signal. The switch SW and the signal generation circuit SG in the shared control circuit 1b function as a modulation control circuit that controls the modulation operation of the illumination light. The switch SW may be a switching element such as a thyristor.

  Further, the illumination light modulation operation will be described with reference to FIG. 50B. FIG. 50B is a diagram illustrating a truth table representing the communication signals of the signal generation circuit SG in FIG. 50A and the operating states of the switch SW and the transistor 2. “SG” indicates the logical value (high level or low level) of the communication signal, “SW” indicates the state of the switch SW (on or off), and “2” indicates the state of the transistor 2 (on or off). Here, it is assumed that the communication signal is the inverted 4PPM signal of FIG.

  When the communication signal is L (low level), the switch SW is on, the transistor 2 is off, no current flows through the light source, and the light is extinguished.

  When the communication signal is H (high level), the switch SW is off, the transistor 2 is on, and a current flows through the light source to light it. Thus, the illumination light is modulated by turning on and off the transistor 2 by the binary communication signal.

  Subsequently, the operation of suppressing the current flowing through the light source will be described. The notation “* ON” in FIG. 50B has the following meaning. That is, the transistor 2 is not necessarily in a completely on state, but is dynamically in a completely on or incomplete on state depending on an error between the plus input terminal and the minus input terminal of the amplifier 7. The degree of incomplete ON (that is, the magnitude of the source-drain resistance of the transistor 2) is determined according to the above error. Thereby, the current flowing through the transistor 2 (that is, the current flowing through the light source) is suppressed so as not to exceed the current set value. This current set value is determined according to a reference value input to the positive input terminal of the amplifier 7.

  This suppression operation is performed by a circuit portion of the shared control circuit 1b excluding the signal generation circuit SG and the switch SW. That is, the reference source 4, the control circuit 6, the resistor R5, the resistor R6, and the amplifier 7 in the shared control circuit 1b function as a current suppressing circuit that causes the transistor 2 to perform a suppressing operation.

The reference source 4 outputs a reference value to the positive input terminal of the amplifier 7. The reference value defines the upper limit (current setting value) of the current flowing through the load circuit 53 that is a light source. For example, the reference value is proportional to the current setting value. The reference source 4 may output the reference value as a fixed value, or may output a variable reference value according to the arrangement pattern (for example, bit pattern) of communication signals generated by the signal generation circuit SG. .

  The resistor R3 is a source resistor for detecting the magnitude of the current flowing through the load circuit 53. The source side terminal of the resistor R3 is connected to the negative input terminal of the amplifier 5.

  In the amplifier 7, the reference source 4 is connected to the plus input terminal via the voltage dividing resistors R5 and R6, and the source of the transistor 2 is connected to the minus input terminal. The amplifier 7 determines the level of the gate signal or the base signal to the transistor 2 so that the current flowing through the light source does not exceed the current set value when the communication signal instructs to turn on or off. Specifically, the amplifier 7 amplifies the difference between the reference value and the current value detected by the resistor R3, and outputs the amplified signal to the gate of the transistor 2.

  The control circuit 6 performs control to change the reference value of the reference source 4 in accordance with the arrangement pattern of the communication signal in order to output a variable reference value from the reference source 4. For example, the control circuit 6 calculates a partial on-duty ratio of the communication signal. When the calculated partial on-duty ratio is the first ratio, the control circuit 6 sets the reference value to the first value, When the on-duty ratio is a second ratio larger than the first ratio, the reference value is set to a second value smaller than the first value. At this time, the control circuit 6 may change the reference value so as to be inversely proportional to the partial on-duty ratio of the communication signal. The “partial on-duty ratio” is, for example, the ratio of the on-period to the total of the off-period immediately before and the on-period immediately before the off-period. Alternatively, the “partial on-duty ratio” may be substituted with the latest n-bit moving average value of the communication signal. In this way, when the magnitude of the overshoot generated in the current flowing through the load circuit 53 depends on the partial on-duty ratio, the overshoot can be suppressed more appropriately.

  50A, when the reference source 4 outputs a fixed reference value, the shared control circuit 1b may not include the control circuit 6.

[7.2 Operation of Illumination Optical Communication Device]
The operation of the illumination light communication apparatus configured as described above will be described using simulation results.

  51 to 54 show the simulation results of the dual-purpose control circuit 1b shown in FIG. 50A.

  FIG. 51 is a diagram showing a first simulation result for the circuit example of FIG. 50A. FIG. 51 shows the LED current and output voltage waveforms when the on-duty ratio is 60%, 75%, 90%, and 100%. In this simulation, the capacity of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal (that is, the communication signal) that drives the switch SW is 2.4 kHz. As shown in the figure, it can be seen that the LED current overshoot is suppressed regardless of the on-duty ratio. In addition, the voltage waveform also fluctuates but is not as severe as the current fluctuation, indicating that the operating resistance of the LED load is low.

FIG. 52 shows the result of obtaining the optimum current setting value of the shared control circuit 1b according to the on-duty ratio of the modulation signal from the signal generator SG. FIG. 52 is a diagram showing a second simulation result for the circuit example of FIG. 50A. Also in this simulation, the capacity of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal for driving the switch SW is 2.4 kHz. In FIG. 52, if the current setting value is varied as illustrated in accordance with the on-duty ratio on the horizontal axis, the fluctuation value of the LED current due to overshoot is suppressed, and the average value is the case where the transistor 2 is not intermittently connected. Value can be maintained. Note that the fluctuation range in the figure represents the overshoot of the modulated rectangular waveform LED current waveform. Since the average value of the LED current is substantially constant regardless of the on-duty, the brightness of the illumination light is also maintained substantially constant regardless of the on-duty. In addition, since the fluctuation range is small, overshoot of the LED current waveform is suppressed and becomes a substantially rectangular wave, so that a reception error of the receiving device can be prevented. Note that some fluctuation is observed when the on-duty is 100% (no modulation), but this is due to the high-frequency ripple existing in the original waveform without modulation.

  FIG. 53 is a diagram showing a third simulation result for the circuit example of FIG. 50A. Also in this simulation, the capacity of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal for driving the switch SW is 2.4 kHz. In FIG. 53, according to the on-duty ratio on the horizontal axis, the peak value and the average value of the output voltage have almost the same value, and the fluctuation range is small and within the range.

  Furthermore, the circuit loss of the shared control circuit 1b is shown in FIG. FIG. 54 is a diagram showing a fourth simulation result for the circuit example of FIG. 50A. The simulation conditions are the same as those in FIGS. The vertical axis represents the circuit loss in the shared control circuit 1b. In FIG. 54, it can be seen that the circuit loss is kept at a low value at the on-duty ratio of 50% to 90%, that is, when the modulation operation is performed.

[7.3 Configuration Example of Communication Module 10]
Next, the removable communication module 10 will be described.

  In FIG. 50A, the communication module 10 is connected to one end of the load circuit 53 and one end of the power supply circuit 52a via terminals T1 and T2. Terminals T1 and T2 may be terminal blocks or connectors. Thus, the communication module 10 is detachable from the terminals T1 and T2.

  Instead of the communication module 10, a short line can be connected to the terminals T1 and T2. In FIG. 50A, a device in which a short line is connected to terminals T1 and T2 instead of the communication module 10 functions as an illumination device that does not have a visible light communication function.

  According to the configuration as shown in FIG. 50A, a simple circuit portion (that is, the communication module 10) is added later by using a power supply circuit and an LED light source mounted on an existing lighting fixture that does not have an optical communication function. Thus, an optical communication function can be added.

  As described above, the dual-purpose control circuit 1b in the illumination light communication apparatus according to the seventh embodiment controls the transistor 2 to share the illumination light modulation operation and the current suppression operation of the light source.

  According to this, since the overshoot that occurs at the rise of the current waveform due to the suppression operation is suppressed, there is an effect that it is difficult to cause a reception error of the reception device. In addition, since the transistor 2 is also used as a switch element that performs the above-described modulation operation and a current suppression element that performs a suppression operation, an increase in circuit elements can be suppressed.

  The dual-purpose control circuit 1b generates a gate signal or base signal input to the gate or base of the transistor 2 in accordance with the communication signal, thereby causing the transistor 2 to perform a modulation operation, and the communication signal is turned on and off. May be determined such that the current flowing through the light source does not exceed the current set value.

  The dual control circuit 1b includes a current detection circuit (that is, a resistor R3) that detects the magnitude of the current flowing through the light source, a reference source 4 that outputs a reference value corresponding to a current setting value, and the magnitude of the current. An amplifier 7 having two input terminals to which the reference value is input, amplifying an error between the two input terminals, and outputting the amplified signal as a gate signal or a base signal, and at least two input terminals A switch circuit (for example, a switch SW) that is coupled to one side and that makes the error substantially zero when the communication signal instructs to turn off may be provided. Here, making the error substantially zero means a value at which the error makes the output of the amplifier 7 low level. For example, the minus input terminal and the plus input terminal may be at the same potential, or the minus input terminal may be at a higher potential than the plus input terminal.

  The switch circuit includes a switch transistor (for example, a switch SW), and the switch transistor is turned on when the communication signal instructs to turn off, so that the reference value of the two input terminals is set. The level of the corresponding input terminal may be substantially the ground level. Here, the substantially ground level means a level that makes the above error substantially zero, in other words, a level that makes the output of the amplifier 7 low. For example, the substantially ground level may be the ground level (that is, 0 V), or may be the same level as or lower than the negative input terminal even if it is not the ground level.

  Here, one end of the switch transistor (for example, the switch SW) is connected to an input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor is a wiring that is substantially at ground potential. (See FIG. 50A).

  Here, the dual control circuit 1b further includes a resistance element (for example, a resistor 17) connected between the input terminal corresponding to the reference value and the wiring that is substantially at the ground potential, and a switch transistor (for example, a valve). One end of B2) may be connected to an input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor may be connected to a reference source (see FIG. 57C).

(Embodiment 8)
In the seventh embodiment, the circuit example of the dual-purpose control circuit 1b in which the switch SW is connected to the plus input terminal of the amplifier 7 is shown. On the other hand, in the eighth embodiment, a circuit example of the dual control circuit 1b in which the switch SW is connected to the negative input terminal of the amplifier 7 will be described.

  The configuration of the illumination light communication apparatus according to Embodiment 8 is the same except for the communication module 10 in FIG. 50A. Hereinafter, different points will be mainly described.

  FIG. 55 is a diagram illustrating a configuration example of the communication module 10 having the dual-purpose control circuit 1b according to the eighth embodiment. The figure mainly differs from FIG. 50A in that the switch SW is connected to the negative input terminal and that a resistor R8 is added. Hereinafter, different points will be mainly described.

  The switch SW includes an input terminal (that is, a negative input terminal) corresponding to the magnitude of the current detected by the resistor R3, and a wiring having a substantially reference level (that is, the input terminal). Connected to the plus side wiring of the reference source 4). The communication signal of the signal generation circuit SG of FIG. 55, the operation state of the switch SW and the transistor 2 are the same as the truth table shown in FIG. 50B.

  The resistor R8 is a resistor for limiting a current flowing from the reference source 4 to the ground line (wiring connected to the terminal T2) via the resistor R8 and the resistor R3 when the switch SW is on.

  The switch SW in FIG. 55 conducts when the communication signal instructs to turn off, thereby substantially reducing the level of the negative input terminal corresponding to the magnitude of the current of the two input terminals to the reference value. To level. Here, the level substantially equal to the reference value refers to a level at which the above error is substantially zero, in other words, a level at which the output of the amplifier 7 is at a low level. For example, the level of the reference value may be substantially the same level as the reference value or may be a level higher than that of the plus input terminal.

  Thus, the dual control circuit 1b of FIG. 55 substantially sets the negative input terminal corresponding to the magnitude of the current flowing through the light source to the level of the reference value when the communication signal instructs to turn off. Transistor 2 is turned off. The dual control circuit 1b turns on the transistor 2 when the communication signal instructs lighting.

  Thereby, the dual-purpose control circuit 1b can cause the transistor 2 to perform a modulation operation.

  The operation of the illumination light communication apparatus according to the eighth embodiment configured as described above will be described using simulation results.

  FIG. 56 is a diagram showing a first simulation result for the circuit example of FIG. FIG. 56 shows LED current and output voltage waveforms when the on-duty ratio is 60%, 75%, 90%, and 100%. In this simulation, the capacity of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal (that is, the communication signal) that drives the switch SW is 2.4 kHz. This figure shows a result similar to FIG. 51, and it can be seen that the LED current overshoot is suppressed regardless of the on-duty ratio. In addition, the voltage waveform also fluctuates but is not as severe as the current fluctuation, indicating that the operating resistance of the LED load is low.

  As described above, the dual-purpose control circuit 1b in the illumination light communication apparatus according to the eighth embodiment performs control for causing the transistor 2 to share the illumination light modulation operation and the suppression operation of the current flowing through the light source.

  The switch circuit (that is, the switch SW that is a switching transistor) conducts when the communication signal instructs to turn off, thereby substantially setting the level of the input terminal corresponding to the magnitude of the current of the two input terminals. Therefore, the level is set to the reference value.

  According to this, the dual-purpose control circuit 1b turns off the transistor 2 when the communication signal instructs to turn off. As a result, the dual control circuit 1b can cause the transistor 2 to perform a modulation operation.

  One end of the switch transistor (switch SW in FIG. 55 or valve B2 in FIG. 57A) is connected to an input terminal corresponding to the magnitude of the current among the two input terminals, and the other end of the switch transistor is It may be connected to a wiring having a substantially reference level.

(Embodiment 9)
In the ninth embodiment, several configuration examples of the dual-purpose control circuit 1b will be described.

  The configuration of the illumination light communication apparatus according to Embodiment 9 is the same except for the communication module 10 in FIG. 50A. Hereinafter, different points will be mainly described.

  FIG. 57A is a diagram illustrating a configuration example of a communication module including the dual control circuit 1b according to the ninth embodiment.

  The communication module 10 of FIG. 57A includes a transistor 2 and a dual control circuit 1b. The shared control circuit 1b includes a signal generation circuit SG, a valve B1, a valve B2, a resistor R3, a resistor R8, an amplifier 7, a resistor 9a, a resistor 11r, a capacitor 12c, an amplifier 13a, a resistor 14, a capacitor 15, and an inverter 16.

  The circuit portion including the signal generation circuit SG, the valve B1, the valve B2, and the inverter 16 in the shared control circuit 1b functions as a modulation control circuit that causes the transistor 2 to perform a modulation operation.

  Since the signal generation circuit SG has already been described, a description thereof will be omitted.

  The valve B1 may be, for example, a switching element such as a switching transistor or a thyristor, and is opened or closed according to a control signal input to the control terminal, that is, non-conductive or conductive. A communication signal from the signal generation circuit SG is input to the control terminal of the valve B1.

  The valve B2 may be the same element as the valve B1. An inverted communication signal is input from the signal generation circuit SG via the inverter 16 to the control terminal of the valve B2. The bulb B2 is a negative input terminal corresponding to the magnitude of the current flowing through the light source, and a wiring having a substantially reference level (that is, a positive-side wiring of the constant voltage source 4a). ) And connected.

  Here, operation states of the valve B1, the valve B2, and the transistor 2 will be described with reference to FIG. 57B. FIG. 57B is a diagram showing a truth table representing the communication signals from the signal generation circuit SG in FIG. 57A and the operating states of the valves B 1 and B 2 and the transistor 2. “SG” indicates the logical value (high level or low level) of the communication signal, “B1” indicates the state of the valve B1 (on or off), “B2” indicates the state of the valve B2 (on or off), “2” "Indicates the state of transistor 2 (on or off). When the communication signal is L (low level), the bulb B1, the bulb B2, and the transistor 2 are off, on, and off, respectively, and the light source does not flow and is turned off. That is, the valve B2 conducts when the communication signal instructs to turn off, so that the level of the minus input terminal corresponding to the magnitude of the current of the two input terminals is substantially equal to the reference value level. To. As a result, the output signal of the amplifier 7 becomes low level and the transistor 2 is turned off.

  When the communication signal is H (high level), the bulb B1, the bulb B2, and the transistor 2 are on, off, and on, respectively, and a current flows through the light source to light it.

  Thus, the illumination light is modulated by turning on and off the transistor 2 in accordance with the binary communication signal.

  In addition, the circuit portion of the shared control circuit 1b excluding the partial signal generation circuit SG, the valve B1, the valve B2, and the inverter 16 functions as a current suppression circuit that suppresses the current flowing through the light source in the transistor 2.

  The resistor R3 is a resistor for detecting the magnitude of the current flowing through the transistor 2, that is, the current flowing through the load circuit 53 that is a light source.

  The resistor R8 is a resistor for limiting the current flowing from the constant voltage source 4a to the ground line via the resistor R8 and the resistor R3 when the valve B2 is on.

The resistor 9a and the resistor 11r are circuits that function as variable reference sources. That is, the resistor 9a and the resistor 11r detect the magnitude of the voltage applied to the shared control circuit 1b when the valve B1 is on. That is, the voltage at the connection point between the valve B1 and the resistor 11r indicates the magnitude of the voltage applied to the shared control circuit 1b, and the positive input of the amplifier 7 through the amplifier 13a (here, the amplifier 13a functions as a buffer). Input to the terminal as a reference value. The voltage applied to the shared control circuit 1b changes according to the on-duty as in the output voltage of FIG. 51 or FIG. In FIG. 57A, the voltage applied to the shared control circuit 1b is input to the plus input terminal of the amplifier 7 as a variable reference value. With this variable reference value, the current setting value indicating the upper limit of the current flowing through the transistor 2 can be set to an appropriate value according to the output voltage and the on-duty.

  The constant voltage source 4a generates a constant voltage that is equal to or higher than a reference value.

  The resistor 11r and the capacitor 12c function as a filter, and the amplifier 13a functions as an impedance matching buffer. The resistor 14 and the capacitor 15 function as a noise cut filter.

  As described above, in the dual control circuit 1b of FIG. 57A, the valve B2 (for example, the switch transistor) has a large current flowing through the light source when the communication signal instructs to turn off (when the communication signal is L). The transistor is turned off by setting the negative input terminal corresponding to the reference level substantially to the reference value level. As a result, the dual control circuit 1b can cause the transistor 2 to perform a modulation operation.

  Next, a modified example of the shared control circuit 1b will be described.

  FIG. 57C is a diagram showing a modification of the communication module including the dual control circuit 1b according to the ninth embodiment. FIG. 57D is a diagram showing a truth table showing communication signals from the signal generation circuit SG in FIG. 57C, and the states of the valves B1 and B2 and the transistor 2.

  The dual-purpose control circuit 1b of FIG. 57C is different from FIG. 57A in that the connection position of the valve B2 is different, that a resistor 17 is added, and that the constant voltage source 4a, the inverter 16 and the resistor R8 are omitted. Is different. Hereinafter, different points will be mainly described.

  The valve B2 is connected to the plus input terminal corresponding to the reference value of the two input terminals of the amplifier 7 and the output terminal of the amplifier 13a, and when the communication signal instructs to turn off (the communication signal is L). Is off), the level of the positive input terminal corresponding to the reference value of the two input terminals is substantially brought to the ground level via the resistor 17. That is, when the communication signal instructs to turn off (when the communication signal is L), the error between the two input terminals is substantially zero, and the transistor 2 is turned off.

  On the other hand, when the communication signal instructs lighting (when the communication signal is H), the transistor 2 is conductive and functions as a current suppressing element, as in FIG. 57A.

  Next, another modification of the dual-purpose control circuit 1b will be described.

  FIG. 57E is a diagram showing another modification of the communication module including the dual control circuit 1b in the ninth embodiment. FIG. 57F is a diagram showing a truth table showing communication signals from the signal generation circuit SG in FIG. 57E, the states of the valves B1, B2, the transistor 22, and the bipolar transistor 20.

  57E is different from FIG. 57A in that bipolar transistors 20, 21, transistor 22, buffer 23b, buffer 24b, and resistor 26 are provided instead of resistors R3 and R8, transistor 2, and amplifier 7. Hereinafter, different points will be mainly described.

  Bipolar transistors 20 and 21 form a current mirror circuit and perform the same function as transistor 2 in FIG. 57A or 57B. That is, when the communication signal instructs to turn off (when the communication signal is L), the transistor 22 is turned off, and the base signal of the transistor 21 on the mirror side of the current mirror becomes substantially 0 V (or 0 A), The bipolar transistor 20 is turned off. At this time, the valves B1 and B2 are open (off), and no wasteful current flows. Further, when the communication signal instructs lighting (the communication signal is H), the valves B1 and B2 are closed (ON), and the transistor 22 is also ON. At this time, the reference value from the output terminal of the amplifier 13a is supplied as a base signal to the base of the bipolar transistor 20 via the valve B2 and the resistor 25. Thereby, the bipolar transistor 20 suppresses the current flowing through the bipolar transistor 20 so as not to exceed the current set value corresponding to the reference value.

  Next, the simulation result of the dual control circuit 1b of FIG. 57C will be described with reference to FIGS.

  FIG. 58 is a diagram showing a first simulation result for the circuit example of FIG. 57C. 58 shows the peak value, average value, and fluctuation value (the same as the LED current) of the current flowing through the dual-purpose control circuit 1b in accordance with the on-duty ratio of the modulation signal (that is, communication signal) from the signal generator SG. That is, the fluctuation range). In this simulation, the capacity of the smoothing capacitor 65 is 20 uF, the frequency of the modulation signal is 2.4 kHz, and the on-duty ratio is changed from 50% to 90%. The peak value of the LED current is almost the same as the current setting value corresponding to the reference value shown in FIG. 52, indicating that overshoot is suppressed. The average value of the LED current is almost constant regardless of the on-duty ratio, that is, the brightness is apparently constant for humans. The fluctuation value of the LED current is almost 0, and the overshoot is almost eliminated.

  FIG. 59 is a diagram showing a second simulation result for the circuit example of FIG. 57C. FIG. 59 shows the ripple rate (variation rate) of the LED current when the on-duty ratio is changed. The simulation conditions are the same as in FIG. As shown in the figure, the ripple rate is smaller than 2%. The ripple rate described here is defined as follows, which is obtained by dividing the fluctuation amount of the rectangular-wave LED current that flows during the on-period of the transistor 2 by the average current value.

  Ripple rate = (current peak value-current bottom value) / (2 x average current value)

  FIG. 60 is a diagram illustrating a third simulation result for the circuit example in FIG. 57C. FIG. 60 shows the circuit loss (that is, power consumption) of the shared control circuit 1b when the on-duty ratio is changed. The simulation conditions are the same as in FIG. As shown in the figure, the circuit loss is suppressed to be lower than 0.5W. This is an effect obtained by controlling the current flowing through the transistor 2 to substantially the target current setting value, thereby suppressing the occurrence of excessive power loss in the shared control circuit 1b.

  Next, a simulation result of the dual control circuit 1b shown in FIG. 57E will be described with reference to FIGS.

  FIG. 61 is a diagram showing a first simulation result for the circuit example of FIG. 57E. FIG. 61 shows the peak value, average value, and fluctuation value (that is, fluctuation width) of the current (that is, the same as the LED current) flowing through the dual-purpose control circuit 1b in accordance with the ON duty ratio of the modulation signal from the signal generator SG. Show. In this simulation, the capacity of the smoothing capacitor 65 is 20 uF, the frequency of the modulation signal is 2.4 kHz, and the on-duty ratio is changed from 50% to 100%. The peak value of the LED current is almost the same as the current setting value corresponding to the reference value shown in FIG. 52, indicating that overshoot is suppressed. The average value of the LED current is almost constant regardless of the on-duty ratio, that is, the brightness is apparently constant for humans. The fluctuation value of the LED current is almost 0, and the overshoot is almost eliminated.

  FIG. 62 is a diagram showing a second simulation result for the circuit example of FIG. 57E. FIG. 62 shows the ripple rate (variation rate) of the LED current when the on-duty ratio is changed. The simulation conditions are the same as in FIG. As shown in the figure, the ripple rate is 1.5% or less. The ripple rate described here is also the same as in the case of FIG.

  FIG. 63 is a diagram showing a third simulation result for the circuit example of FIG. 57E. FIG. 60 shows the circuit loss (that is, power consumption) of the shared control circuit 1b when the on-duty ratio is changed. The simulation conditions are the same as in FIG. As shown in the figure, the circuit loss is kept lower than 0.7W. This is an effect obtained by controlling the current flowing through the transistor 2 to substantially the target current setting value, thereby suppressing the occurrence of excessive power loss in the shared control circuit 1b.

  Next, a modification of the dual-purpose control circuit 1b shown in FIG. 57A will be described.

FIG. 57G is a diagram illustrating a configuration example of the communication module 10 including a modification of the dual control circuit 1b of FIG. 57A. The dual-purpose control circuit 1b in FIG. 57G has a configuration suitable for practical use for simplification based on FIG. 57A. FIG. 57G is different from FIG. 57A in the following points. That is, the impedance matching circuit (amplifier 13a, resistor 11r, capacitor 12c) is omitted, the valve element B1 is replaced with a MOSFET, and a gate resistor Rg1 and a gate protection resistor Rg2 are added.

  Further, in order to reliably prevent the applied voltage during the period when the transistor 2 is turned off (the voltage applied to the dual-purpose control circuit 1b gradually increases during the off period) from entering the positive input terminal of the amplifier 7, it is possible to generate a signal. A delay circuit Dy for delaying the rise of the signal of the circuit SG is provided, and its output is connected to the gate resistance Rg1 of the MOSFET (B1).

  Further, in FIG. 57G, the valve B2 in FIG. 57A is omitted, and the output terminal of the inverter 16 is connected to the negative input terminal of the amplifier 7 via the resistor 10, and the gain is connected between the output terminal of the amplifier 7 and the negative input terminal. By connecting the adjustment resistor Rf and the capacitor Cf as an integral element, the transient characteristics associated with the on / off of the transistor 2 can be adjusted. In particular, since the capacitor Cf can change the rise time of the modulated rectangular wave LED current waveform by changing its capacitance value, it is convenient for making an appropriate adjustment according to the reception sensitivity of the receiving device.

  Note that the capacitor Co provided between the terminals T1 and T2 suppresses the parasitic vibration that may be caused by the off operation of the transistor 2, and is effective in reducing noise and preventing malfunction.

(Modification)
Next, a modification of the illumination light communication device will be described.

  FIG. 64 is a circuit diagram showing a modification of the illumination light communication apparatus in the seventh embodiment. The illumination light communication apparatus of the same figure differs in the circuit configuration inside the power supply circuit 52a compared with FIG. 50A. Hereinafter, different points will be mainly described.

  In the power supply circuit 52a of FIG. 50A, feedback control is performed to make the average value of the output current constant by the constant current feedback circuit 67, whereas in the power supply circuit 52a of FIG. 64, threshold value control of the switching current is performed. Is configured to do.

  64 includes a rectifier bridge 62, a capacitor 63, and a DC-DC converter 64. The DC-DC converter 64 includes an inductor 80, a switch element 81, a diode 66d, a resistor 82, a signal source 83, a flip-flop 84, a comparator 85, a constant voltage source 86, a capacitor 87, a resistor 88, a diode 89, a driver 90, and a gate resistor. 91 is provided.

  The inductor 80, the switch element 81, and the diode 66d are basic circuit elements that constitute the DC-DC converter 64 as a buck converter.

  Control for turning on and off the switch element 81 is performed by the signal source 83, the flip-flop 84, the comparator 85, and peripheral circuits, and threshold control of the switching current of the switch element 81 is performed. That is, the switching current is also a current through the load circuit 53 (light emitting diode), and an alternative function of constant current feedback can be obtained by threshold control. Such an operation of the DC-DC converter 64 is as already described with reference to the waveform diagram of FIG. 30B.

  The threshold current control of the switching current in FIGS. 64 and 30B substitutes for the constant current feedback control of FIG. 50A and works to make the average of the output current constant. As a result, in FIG. 64 as well as in FIG. 50A, if there is no dual control circuit 1b, an overshoot problem occurs. However, in the configuration of FIG. 64, overshoot can be reduced by providing the dual-purpose control circuit 1b as in FIG. 50A.

  As described above, the illumination light communication apparatus according to the seventh to ninth embodiments is an illumination light communication apparatus that modulates illumination light according to a communication signal, and includes a light source that emits illumination light, and a transistor connected in series with the light source. 2, a signal generation circuit SG that generates the binary communication signal, and a dual-purpose control circuit 1 b that allows the transistor 2 to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

  According to this, since the transistor 2 is also used as the switch element that performs the above-described modulation operation and the current suppression element that performs the above-described suppression operation, an increase in circuit elements can be suppressed. In the suppression operation, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the transistor 2 is turned on can be reduced, thereby reducing the reception error in the receiving device.

  Here, the dual-purpose control circuit 1b generates the gate signal or base signal input to the gate or base of the transistor 2 in accordance with the communication signal, thereby causing the transistor 2 to execute the modulation operation, and the communication signal When is instructed to turn on or off, the level of the gate signal or base signal may be determined so that the current flowing through the light source does not exceed the current set value in the suppression operation.

  According to this configuration, the transistor can suppress a current flowing through the light source according to the level of the gate signal or the base signal.

  The dual-purpose control circuit 1b includes a current detection circuit R3 that detects the magnitude of the current flowing through the light source, a reference source 4 that outputs a reference value corresponding to the current set value, the magnitude of the current, and the reference And an amplifier 7 for amplifying an error between the two input terminals and outputting the amplified signal as the gate signal or the base signal, and the two input terminals And a switch circuit that is coupled to at least one and sets the error to substantially zero when the communication signal instructs to turn off.

  According to this configuration, the modulation operation is enabled by substantially reducing the error between the two input terminals when the communication signal instructs to turn off.

  Here, the switch circuit includes a switch transistor, and the switch transistor is turned on when the communication signal instructs to turn off, thereby corresponding to the reference value of the two input terminals. The level of the input terminal may be substantially the ground level.

  According to this configuration, the modulation operation can be performed by setting the input terminal corresponding to the reference value substantially to the ground level when the communication signal instructs to turn off.

  Here, one end of the switch transistor is connected to an input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor is connected to a wiring that is substantially at ground potential. Also good.

  Here, the dual control circuit 1b further includes a resistance element 17 connected between the input terminal corresponding to the reference value and the wiring that is substantially at the ground potential, and one end of the switch transistor is One of the two input terminals may be connected to an input terminal corresponding to the reference value, and the other end of the switch transistor may be connected to the reference source.

  Here, the switch circuit includes a switch transistor, and the switch transistor is turned on when the communication signal instructs to turn off, so that the magnitude of the current of the two input terminals is increased. The level of the corresponding input terminal may be substantially the reference value level.

According to this configuration, when the communication signal instructs to turn off, the modulation operation can be performed by setting the input terminal corresponding to the magnitude of the current substantially to the level of the reference value.

  Here, one end of the switch transistor is connected to an input terminal corresponding to the magnitude of the current of the two input terminals, and the other end of the switch transistor is a wiring having a substantially reference level. You may connect to.

  The dual-purpose control circuit 1b further includes a feedback capacitor Cf connected between the output terminal of the amplifier and an input terminal corresponding to the magnitude of the current among the two input terminals, and the feedback capacitor. And a feedback resistance element Rf connected in parallel.

  According to this configuration, the gain can be adjusted by the feedback resistance element Rf, and the transient characteristic associated with the on / off of the transistor 2 can be adjusted by including the capacitor Cf as an integration element. In particular, since the feedback capacitor Cf can define the rise time of the modulated rectangular wave LED current waveform according to the capacitance value, it is convenient to make an appropriate adjustment according to the reception sensitivity of the receiving device.

  Here, the shared control circuit 1b may further include a capacitor element Co connected between a terminal on the power supply line side of the transistor and a ground line.

  According to this configuration, it is possible to suppress parasitic noise that may occur with the off operation of the transistor, which is effective in reducing noise and preventing malfunction.

  Here, the switch circuit is connected to an input terminal to which the reference value is input out of the two input terminals, and is turned on and off according to the communication signal, and of the two input terminals An inverter that outputs a resistance element R10 connected to an input terminal corresponding to the magnitude of the current and an inverted signal obtained by inverting the communication signal to the input terminal corresponding to the magnitude of the current via the resistance element. The dual-purpose control circuit 1b may further include a delay circuit Dy inserted in a signal line that transmits the communication signal from the signal generation circuit to the switch element.

  According to this configuration, the delay circuit that delays the communication signal or the inverted signal of the signal generation circuit SG is provided, and the delayed communication signal is output to the control terminal of the switch element B1. As a result, it is possible to reliably prevent the voltage applied to the dual-purpose control circuit 1b during the period in which the transistor 2 is turned off (this voltage rises to the exclusion during the off period) from flowing into the positive input terminal of the amplifier. It is possible to prevent garbling.

  Here, the reference source may output the variable reference value according to the on-duty ratio of the communication signal or the voltage applied to the dual control circuit 1b.

  According to this configuration, the reference value can be dynamically optimized, so that the current suppression operation can also be optimized.

  Here, the illumination light communication device includes a power supply circuit that supplies current to the light sources and the transistors connected in series, and the power supply circuit performs feedback control to make an average value of supplied current constant. You may go.

  Here, the power supply circuit includes a DC-DC converter 64 which is a buck converter having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switching element, and the difference between the detected value and a predetermined value The switching element may be controlled to be turned on and off according to the above.

  According to this configuration, even when a DC-DC converter that performs threshold current control of the switching current is provided as a power supply circuit, overshoot can be effectively reduced.

  In addition, the communication module according to each embodiment is a communication module that modulates illumination light that can be attached to and detached from the illumination device, the transistor connected in series with the light source of the illumination device, and the binary communication signal And a dual-purpose control circuit 1b that causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

  According to this, the communication module can be added to an existing lighting fixture. In other words, the existing lighting fixture can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than the case of installing a new optical communication lighting fixture. Further, since the overshoot generated in the current flowing through the light source is reduced at the moment when the switch is turned on from the off state, the reception error in the receiving device can be reduced. In addition, since the transistor has both functions of a switch element that performs a modulation operation and a current suppression element that performs a suppression operation, an increase in circuit elements can be suppressed.

(Embodiment 10)
Embodiment 10 provides an illumination light communication device or a communication module that can reduce a reception error in visible light communication and can realize a stable circuit operation.

  An illumination light communication apparatus according to a tenth embodiment includes a light source that emits illumination light, a switch that is connected in series with the light source and that interrupts a current flowing through the light source, and that the switch is turned on to modulate the illumination light. And a modulation signal generation unit that generates a modulation signal for controlling off, a current suppression circuit that is connected in series with the light source and the switch, and suppresses a current flowing through the light source so as not to exceed a current setting value, and the current A control unit that changes a set value, and the light source, the switch, and the current suppression circuit are connected in series in this order. The current suppression circuit is connected to the ground potential.

  In addition, the communication module according to Embodiment 10 is a communication module that modulates illumination light that can be attached to and detached from the illumination device, and is connected in series with the light source included in the illumination device, and intermittently passes the current flowing through the light source. A switch, a modulation signal generation unit that generates a modulation signal for controlling on / off of the switch to modulate the illumination light, and the light source and the switch are connected in series so as not to exceed a current setting value. A current suppression circuit that suppresses a current flowing through the light source, and the light source, the switch, and the current suppression circuit are connected in series in this order. The current suppression circuit is connected to the ground potential.

  Embodiment 10 According to the illumination light communication device and the communication module, it is possible to reduce reception errors in visible light communication and to realize stable circuit operation.

[10.1 Configuration of Illumination Optical Communication Device]
First, the configuration of the illumination light communication apparatus according to Embodiment 10 will be described. FIG. 65 is a block diagram showing a configuration of illumination light communication apparatus 100 according to the tenth embodiment.

  The illumination light communication apparatus 100 illustrated in FIG. 65 functions as a visible light communication transmitter that transmits a signal by modulating the intensity of illumination light. The illumination light communication apparatus 100 includes a light source 101, a power supply circuit 102, a communication module 103, and a dimming control unit 104.

  The light source 101 includes one or more light emitting elements (for example, LEDs) and emits illumination light.

  The power supply circuit 102 supplies power to the light source 101. The power supply circuit 102 includes a power supply 111, a DC-DC converter 112, a capacitor 113, a detection resistor 114, and a constant current feedback circuit 115.

  The power supply 111 outputs a DC voltage to the DC-DC converter 112. The DC-DC converter 112 converts the DC voltage supplied from the power supply 111 into a desired voltage V0 and outputs the voltage V0 to the light source 101. The capacitor 113 is connected between the output terminals of the DC-DC converter 112.

  The detection resistor 114 is used for detecting a current flowing through the light source 101. The constant current feedback circuit 115 controls the output voltage V0 of the DC-DC converter 112 so that the current flowing through the detection resistor 114, that is, the current flowing through the light source 101 is constant.

  The DC-DC converter 112 controls the output voltage V0 based on the dimming signal S3 output from the dimming control unit 104.

  The communication module 103 can be attached to and detached from a lighting device including the light source 101 and the power supply circuit 102. In a state where the communication module 103 is not attached to the lighting device, the cathode of the light source 101 and the GND terminal of the power supply circuit 102 are short-circuited. That is, by attaching the communication module 103 to an illumination device that does not support visible light communication, the visible light communication function can be realized by the illumination device.

  The communication module 103 includes a modulation switch 121, a current suppression circuit 122, a modulation signal generation unit 123, an external synchronization signal input unit 124, a control unit 125, a control power supply 126, a voltage detection circuit 127, and a drive circuit 128. With.

  The modulation signal generation unit 123 generates a modulation signal based on a communication signal transmitted by visible light communication. The modulation signal generation unit 123 may repeatedly generate a modulation signal indicating an ID unique to the illumination light communication apparatus 100, or may generate a modulation signal in accordance with a communication signal input from an external apparatus. Good.

  The external synchronization signal input unit 124 supplies the modulation signal generated by the modulation signal generation unit 123 to the control unit 125.

  The control unit 125 is configured by a microcomputer (for example, a CPU), generates a binary modulation signal S1 based on the modulation signal supplied from the external synchronization signal input unit 124, and sends the generated modulation signal S1 via the drive circuit 128. To the control terminal (gate terminal) of the modulation switch 121.

  The control power supply 126 generates a power supply voltage of the control unit 125 from the voltage V0 output from the power supply circuit 102, and supplies the generated power supply voltage to the control unit 125. The voltage detection circuit 127 detects the output voltage V 0 of the power supply circuit 102.

  The modulation switch 121 is connected in series with the light source 101, and interrupts the current supplied from the power supply circuit 102 to the light source 101. The modulation switch 121 is, for example, a transistor (for example, a MOSFET).

  The current suppression circuit 122 is connected in series with the light source 101 and the modulation switch 121 and suppresses the current flowing through the light source 101. Specifically, the current suppression circuit 122 suppresses (clips) the current flowing through the light source 101 so as not to exceed the current set value Is.

  The current suppression circuit 122 includes a transistor 131 that is a MOSFET, a current setting circuit 132, an amplifier 133, and a current detection circuit 134 that is a resistor connected to the source of the transistor 131.

  The current setting circuit 132 outputs a reference value to the plus input terminal of the amplifier 133. The reference value defines the upper limit (current setting value Is) of the current flowing through the light source 101. For example, the reference value is proportional to the current setting value. The current setting circuit 132 outputs a variable reference value corresponding to the current command value S2 generated by the control unit 125. Note that the current setting circuit 132 may output the reference value as a fixed value.

  The transistor 131 is connected in series to the light source 101 and the modulation switch 121, and suppresses (clips) the current flowing through the light source 101 based on a reference value.

  The current detection circuit 134 is a source resistance for detecting the magnitude of the current flowing through the light source 101. The terminal on the transistor 131 side of the current detection circuit 134 is connected to the negative input terminal of the amplifier 133.

  The positive input terminal of the amplifier 133 is connected to the current setting circuit 132, and the negative input terminal of the amplifier 133 is connected to the source terminal of the transistor 131. The amplifier 133 amplifies the difference between the reference value output from the current setting circuit 132 and the current value detected by the current detection circuit 134, and outputs the amplified signal to the gate of the transistor 131.

  The circuit configuration illustrated in FIG. 65 is an example, and the illumination light communication apparatus 100 does not have to include all the components illustrated in FIG. For example, the illumination light communication apparatus 100 may not include at least one of the dimming control unit 104 and the voltage detection circuit 127.

  The configuration of the power supply circuit 102 is also an example, and the present invention is not limited to this configuration. For example, the power supply circuit 102 may not include the detection resistor 114 and the constant current feedback circuit 115. Further, the DC-DC converter 112 may perform constant current control. For example, the DC-DC converter 112 may perform switching current threshold control. Alternatively, the power supply circuit 102 may perform constant voltage control instead of constant current control. For example, the power supply circuit 102 may include a constant voltage feedback circuit instead of the detection resistor 114 and the constant current feedback circuit 115, or the DC-DC converter 112 may perform constant voltage control.

  The configuration of the current suppression circuit 122 is also an example, and the configuration is not limited to this as long as the current flowing through the light source 101 can be suppressed (clipped). For example, instead of the current suppression circuit 122, current suppression circuits 122A, 122B, or 122C shown in FIGS. 66 to 68 may be used. 66 to 68 are connected to the modulation switch 121, and the terminal T2 is connected to the GND terminal of the power supply circuit 102.

  A current suppression circuit 122A illustrated in FIG. 66 includes bipolar transistors 141 and 142, a current setting circuit 132A that is a variable voltage source, and a resistor 143. Bipolar transistors 141 and 142 constitute a current mirror circuit. The current flowing through the bipolar transistor 142 is determined by the voltage output from the current setting circuit 132A and the resistance value of the resistor 143. The bipolar transistor 141 can pass a current within a range that does not exceed a current (that is, a current set value Is) that is twice the mirror ratio of this current. The current setting circuit 132A changes the output voltage according to the current command value S2 output from the control unit 125.

  A current suppression circuit 122B illustrated in FIG. 67 includes a bipolar transistor 151, an emitter resistor 152, a bias resistor 153, and a current setting circuit 132B that is a Zener diode.

  The bipolar transistor 151 is connected in series with the light source 101 and the modulation switch 121. The current flowing through the light source 101 is suppressed according to the base voltage (reference value) of the bipolar transistor 151.

  The emitter resistor 152 is a resistor for detecting the magnitude of the current flowing through the light source 101 (that is, the current flowing through the emitter resistor 152).

  The bias resistor 153 is a resistor for biasing the base voltage of the bipolar transistor 151.

  The current setting circuit 132B outputs a reference value corresponding to the current command value S2 output from the control unit 125 to the base of the bipolar transistor 151.

  The current suppression circuit 122C illustrated in FIG. 68 includes a three-terminal regulator 161 and a current setting circuit 132C that is a detection resistor.

  In the three-terminal regulator 161, an input terminal IN and an output terminal OUT are connected in series with the light source 101 and the modulation switch 121, and the input terminal IN and the output terminal OUT are connected between the input terminal IN and the output terminal OUT according to the voltage input to the adjustment terminal ADJ. Suppresses the flowing current.

  The current setting circuit 132C is a resistor for detecting the magnitude of the current flowing through the light source 101 (that is, the current flowing through the current setting circuit 132C). The current setting circuit 132C is a variable resistor, and its resistance value is changed according to the current command value S2 output from the control unit 125. The current setting circuit 132C is connected between the output terminal OUT of the three-terminal regulator 161 and the terminal T2, and the terminal T2 is connected to the adjustment terminal ADJ of the three-terminal regulator 161.

[10.2 Basic operation]
Hereinafter, the basic operation of the illumination light communication apparatus 100 will be described. FIG. 69 is a diagram illustrating a basic operation of the illumination light communication apparatus 100. As shown in FIG. 69, the modulation switch 121 is turned on / off according to the modulation signal S1. The modulation method used here conforms to, for example, the 1-4PPM transmission method defined in JEITA-CP1223. Specifically, 2-bit data is converted into a 4-slot pulse. At all times, three of these four slots are high level (on) and one slot is low level (off).

  In the example of FIG. 69, the current command value S2 is constant, and the current set value Is is constant.

  Here, when the modulation for visible light communication is performed, immediately after the modulation switch 121 is turned on, as indicated by the dotted line in FIG. A shoot occurs. Due to the occurrence of this overshoot, there is a problem that a signal cannot be received correctly in the visible light receiver.

  On the other hand, in the illumination light communication apparatus 100 according to the tenth embodiment, the maximum value of the LED current is limited to the current set value Is by providing the current suppression circuit 122. This suppresses the occurrence of overshoot as shown in FIG. Thereby, the reception error in visible light communication can be reduced.

  Note that the constant current feedback circuit 115 shown in FIG. 65 also has a function of making the LED current constant, but the constant current control by the constant current feedback circuit 115 is a control with a relatively large time constant. That is, this constant current control is a control that keeps the average current constant during a predetermined period, and it is not possible to suppress the instantaneous overshoot as shown in FIG.

  Furthermore, in the tenth embodiment, as shown in FIG. 70, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order between the power supply terminal and the GND terminal of the power supply circuit 102. On the other hand, as a connection form of the light source 101, the modulation switch 121, and the current suppression circuit 122, the light source 101, the current suppression circuit 122, and the modulation switch 121 may be connected in this order as in the illumination light communication device 100A illustrated in FIG. Conceivable.

  However, in the connection form of FIG. 71, the current suppression circuit 122 is not connected to the GND terminal of the power supply circuit 102, which causes a problem that the operation becomes unstable. Specifically, when the modulation switch 121 is in the OFF state, GND (V1) of the current suppression circuit 122 is in a floating state (floating), so that the potential fluctuation of GND increases. On the other hand, in the tenth embodiment, by using the connection form shown in FIG. 70, the current suppression circuit 122 is always connected to the GND terminal, so that stable operation can be improved regardless of the state of the modulation switch 121.

  In particular, when the variable current set value Is is used, the minute current cannot be controlled with high accuracy in the connection form of FIG. 71, and it is difficult to control the current set value Is with high accuracy. On the other hand, since the minute current can be controlled with high accuracy by using the connection form shown in FIG. 70, the current set value Is can be controlled with high accuracy. Furthermore, in the tenth embodiment, since the GND of the control unit 125 (GND of the control power supply 126), which is a microcomputer that generates the current command value S2, and the GND of the current suppression circuit 122 become common, the current set value Is Can be controlled with higher accuracy.

  The signal generation circuit 129 shown in FIGS. 70 and 71 is a circuit that generates a binary modulation signal S1 for controlling the on / off of the modulation switch 121 to modulate the illumination light, and the modulation shown in FIG. A signal generation unit 123, an external synchronization signal input unit 124, a control unit 125, and a drive circuit 128 are included.

  In the above description, a 100% modulation method that completely cuts off the LED current in the off period is used as the modulation method. However, a method in which the LED current is lower than the on period in the off period may be used. However, in the 100% modulation method, the above-described overshoot becomes particularly significant. Therefore, the method of the tenth embodiment is particularly effective when the 100% modulation method is used.

  As described above, the illumination light communication apparatus 100 according to the tenth embodiment includes the light source 101 that emits the illumination light, the modulation switch 121 that is connected in series with the light source 101 and that interrupts the current flowing through the light source 101, and modulates the illumination light. For this purpose, the modulation signal generator 123 for generating the modulation signal S1 for controlling the on / off of the modulation switch 121, and the light source 101 and the modulation switch 121 are connected in series, and the light source 101 is set so as not to exceed the current set value Is A current suppression circuit 122 that suppresses the flowing current and a control unit 125 that changes the current set value Is are provided, and the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order.

  Thereby, since generation | occurrence | production of an overshoot can be suppressed by the current suppression circuit 122, the reception error in visible light communication can be reduced. Further, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order, so that the GND potential is supplied to the current suppression circuit 122 regardless of the state of the modulation switch 121. Therefore, stable circuit operation can be realized.

  Moreover, the illumination light communication apparatus 100 can set the current setting value Is appropriate for each state by changing the current setting value Is. Furthermore, by supplying the GND potential to the current suppression circuit 122 regardless of the state of the modulation switch 121, it is possible to stably control the current set value Is that requires high-precision control.

  The communication module 103 according to the tenth embodiment is a communication module 103 that modulates illumination light, which can be attached to and detached from the illumination device. The communication module 103 is connected in series with the light source 101 included in the illumination device, and receives a current flowing through the light source 101. The modulation switch 121 that is intermittently connected, the modulation signal generation unit 123 that generates the modulation signal S1 that controls the on / off of the modulation switch 121 to modulate the illumination light, the light source 101 and the modulation switch 121 are connected in series, and A current suppression circuit 122 that suppresses the current flowing through the light source 101 so as not to exceed the set value Is, and the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order.

  Thereby, since generation | occurrence | production of an overshoot can be suppressed by the current suppression circuit 122, the reception error in visible light communication can be reduced. Further, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order, so that the GND potential is supplied to the current suppression circuit 122 regardless of the state of the modulation switch 121. Therefore, stable circuit operation can be realized.

[10.3 First Control Example of Current Set Value]
Hereinafter, a control example of the current set value Is will be described. In the following, a plurality of methods for controlling the current set value Is will be described, but only one of the following methods may be used, or a plurality of methods may be used in combination.

  FIG. 72 is a diagram illustrating a first control example of the current set value Is. In the first control example, the control unit 125 changes the current command value S2 (current set value Is) according to the length of the off-period of the modulation switch 121 (low period of the modulation signal S1). Specifically, the control unit 125 sets the current set value Is higher as the off period is longer. That is, the control unit 125 sets the current setting value Is to the first value when the off period is the first length, and sets the current setting when the off period is the second length longer than the first length. The value Is is set to a second value that is higher than the first value. For example, in the case of using 4PPM, when the period corresponding to 1 slot is T0 and the period corresponding to 2 slots is T1, the control unit 125 is shorter than the threshold longer than T0 and shorter than T1, When the current set value Is is set to the first value and the off period is longer than the threshold, the current set value Is is set to a second value higher than the first value.

  Alternatively, the control unit 125 may calculate a partial on-duty ratio of the modulation signal S1, and change the current command value S2 (current set value Is) according to the calculated partial on-duty ratio. . Specifically, the control unit 125 sets the current set value Is lower as the partial on-duty ratio is higher. That is, the control unit 125 may set the current set value Is so as to be inversely proportional to the partial on-duty ratio. In other words, the control unit 125 sets the current setting value Is to the first value when the partial on-duty ratio is the first ratio, and the partial on-duty ratio is larger than the first ratio. When the ratio is 2, the current set value Is is set to a second value smaller than the first value.

  Here, the “partial on-duty ratio” is a ratio of the on (high) period of the modulation signal S1 in a predetermined period. For example, the “partial on-duty ratio” is a ratio of the on-period to a period obtained by combining the latest off-period and the on-period immediately before the off-period. Alternatively, the “partial on-duty ratio” may be the nearest n-bit moving average value of the modulation signal S1.

  Here, the magnitude of the overshoot depends on the length of the off period (partial on-duty ratio). Therefore, overshoot can be more appropriately suppressed by changing the current set value Is according to the length of the off period (partial on-duty ratio).

  In addition, when the length of the off period (partial on-duty ratio) is variable, the longer the off period, the lower the average luminance value. Therefore, in order to make the average luminance value constant, the off period When is long, it is necessary to increase the luminance value in the on period. By controlling the current set value Is described above, the current set value Is can be appropriately changed even when such brightness value control is performed.

[10.4 Second Control Example of Current Set Value]
FIG. 73 is a diagram illustrating a second control example of the current set value Is. In the second control example, the control unit 125 changes the current command value S2 (current setting value Is) according to the dimming signal S3. For example, the dimming signal S3 is generated by the dimming control unit 104 when a dimming (brightness change) operation is performed by the user. The power supply circuit 102 changes the current flowing through the light source 101 by changing the output voltage V0 according to the dimming signal S3. Thereby, the brightness of the illumination light is changed.

  FIG. 73 shows an example when a dimming operation is performed. The control unit 125 decreases the current command value S2 (current setting value Is) when dimming is instructed by the dimming signal S3. That is, the control unit 125 sets the current set value Is according to the dimming level of the light source 101. Specifically, the control unit 125 sets the current set value Is higher as the dimming level is higher (brighter). That is, the control unit 125 sets the current setting value Is to the first value when the dimming level is the first level, and sets the current setting when the dimming level is the second level higher than the first level. The value Is is set to a second value that is higher than the first value.

  By controlling the current set value Is as described above, the current set value Is can be appropriately changed according to the dimming level.

  Further, as shown in FIG. 73, the control unit 125 gradually decreases the current command value S2 from the timing when dimming is instructed by the dimming signal S3. As a result, the current command value S2 can be decreased following the change in the light control level (brightness), and therefore an increase in loss due to the sudden decrease in the current command value S2 can be suppressed.

[10.5 Third Control Example of Current Set Value]
FIG. 74 is a diagram illustrating a third control example of the current set value Is. In the third control example, the control unit 125 determines the current command value S2 (current setting value) according to the LED current detection value S4 that is the detection result of the LED current (current flowing through the light source 101) detected by the current detection circuit 134. Is) is changed. Specifically, the control unit 125 sets the current set value Is lower as the LED current is smaller. That is, the control unit 125 sets the current setting value Is to the first value when the LED current is the first current value, and the current when the LED current is the second current value smaller than the first current value. The set value Is is set to a second value lower than the first value.

  Thereby, for example, when the dimming level is changed as shown in FIG. 74, the current set value Is can be appropriately changed according to the dimming level. In addition, as described with reference to FIG. 72, even when the luminance value (LED current) is changed according to the length of the off period (partial on-duty ratio), the current set value Is can be changed appropriately. Thereby, the increase in loss at the time of light control etc. can be suppressed.

  As shown in FIG. 74, the timing for detecting the LED current is preferably a timing at which no overshoot occurs and the current value is stable. For example, as shown in FIG. 75, the current detection circuit 134 detects the LED current at a timing after a predetermined delay time Td has elapsed from the rising edge of the modulation signal S1 (timing when the modulation switch 121 is turned on). To do. Thereby, the LED current can be detected with high accuracy.

  In FIG. 65, the current detection circuit 134 in the current suppression circuit 122 is also used for LED current detection, but a current detection circuit is provided separately from the current detection circuit 134 in the current suppression circuit 122. The detection result by the current detection circuit may be used for the control.

[10.6 Fourth Control Example of Current Set Value]
FIG. 76 is a diagram illustrating a fourth control example of the current set value Is. In the fourth control example, the control unit 125 changes the current command value S2 (current setting value Is) according to the LED voltage detection value S5 that is the detection result of the voltage V0 detected by the voltage detection circuit 127. Here, the voltage V 0 is a voltage applied to the light source 101. Specifically, the control unit 125 sets the current set value Is lower as the voltage V0 is smaller. That is, the control unit 125 sets the current set value Is to the first value when the voltage V0 is the first voltage value, and the current when the voltage V0 is the second voltage value smaller than the first voltage value. The set value Is is set to a second value lower than the first value.

  Here, the voltage V0 changes with the same tendency as the LED current. Therefore, the same effect as in the third control example can be realized by the above control.

  Note that the voltage detection timing may be controlled in the same manner as the LED current detection. That is, as in the case of FIG. 75, the voltage detection circuit 127 detects the voltage V0 at a timing after a predetermined delay time Td has elapsed from the rising edge of the modulation signal S1 (timing when the modulation switch 121 is turned on). May be.

[10.7 Usage example of illumination light communication device]
Hereinafter, usage examples of the illumination light communication apparatus 100 will be described. FIG. 77 is a diagram illustrating a usage example of the illumination light communication apparatus 100. For example, as shown in FIG. 77, the illumination light communication apparatus 100 is an RGB projector. The visible light receiver receives a visible light signal when the user captures the light emitted by the illumination light communication device 100 with a visible light receiver such as a smartphone.

  FIG. 78 is a diagram showing an appearance of the illumination light communication apparatus 100 that is an RGB projector.

  FIG. 79 is a diagram showing another example of use of the illumination light communication apparatus 100. For example, as shown in FIG. 79, the illumination light communication apparatus 100 is an RGB spotlight. The visible light receiver receives a visible light signal when the user captures the light emitted by the illumination light communication device 100 with a visible light receiver such as a smartphone.

(Embodiment 11)
The control circuit 6 in the current suppression circuit 1 in FIG. 1A or the like can be configured as an analog circuit or a digital circuit. In the eleventh embodiment, an example in which the control circuit 6 is configured as a digital circuit will be described.

  One form of the illumination light communication apparatus according to Embodiment 11 includes a light source that emits illumination light, a switch that is connected in series with the light source and that interrupts the current flowing through the light source, and the light source for modulating the illumination light. A signal generation circuit for generating a binary communication signal for controlling on and off of the switch, and the light source connected in series with the light source and the switch, and flowing through the light source so as not to exceed a current set value corresponding to a reference value A current suppression circuit that suppresses a current, the current suppression circuit being connected in series with a reference source that outputs the reference value, the light source and the switch, and a current flowing through the light source based on the reference value And a control circuit having a shift register for shifting and holding n (n is an integer of 2 or more) bit data of the communication signal Road, the calculated partial on-duty ratio of the communication signal on the basis of n-bit data, determines the reference value in accordance with the calculated partial on-duty ratio.

[11.1 Configuration of Illumination Optical Communication Device]
The overall configuration of the illumination light communication apparatus according to Embodiment 11 may be the same as that of the illumination light communication apparatus illustrated in FIG. 1A or may be the same as that of the illumination light communication apparatus illustrated in FIG.

  FIG. 80 is a circuit diagram showing a modification of the illumination light communication apparatus in the eleventh embodiment. 80 differs from FIG. 64 in the internal configuration of the communication module 10, but the power supply circuit 52a is the same. The communication module of FIG. 80 is as already described in FIG. 1A. The power supply circuit 52a is as already described with reference to FIG.

[11.2 Modification of Current Suppression Circuit 1]
Next, first to third modifications of the current suppression circuit 1 will be described.

  The current suppression circuit 1 in FIG. 1A or FIG. 80 is not limited to this configuration, and may be configured as in the first to third modifications shown in FIG. 2 to FIG. You may comprise like 82.

  FIG. 81 is a circuit diagram showing a fourth modification of current suppression circuit 1 in FIG. 1A or FIG. The current suppression circuit 1 shown in FIG. 81 includes a transistor 2 that is a MOSFET, a resistor 3 connected to a source, a reference source 4, and a control circuit 6. The reference source 4 includes a constant voltage source 4a, voltage dividing resistors R1, R6, R7, and R8, and switch elements S01 to S03 for switching the voltage dividing ratio.

  The control circuit 6 calculates an appropriate reference voltage value according to the signal arrangement of the communication signals, or selects an appropriate reference voltage value from a correspondence table constructed in advance, and switches the switch elements S01 to S03. May be. As the number of resistors and switch elements in the voltage dividing circuit increases, the reference voltage can be switched more finely.

  FIG. 82 is a circuit diagram showing a fifth modification of current suppression circuit 1 in FIG. 1A or FIG. 82 includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 4 and a control circuit 6. The reference source 4 includes a constant voltage source 4a, voltage dividing resistors R11, R12, R13, and R14, and switch elements S01 and S02 for switching the voltage dividing ratio.

  The positive potential side of the reference source 4 is connected to the positive input terminal of the error amplifier via the resistor R11. A series circuit of resistors R12, R13, and R14 is provided between the connection point and the negative potential side of the reference voltage, and switch elements S01 and S02 that short-circuit one or two of them are connected. The

  The control circuit 6 in FIG. 82 may be the same as that in FIG.

[11.3 Configuration Example of Control Circuit 6]
Next, the configuration of the control circuit 6 that performs control to change the reference value of the reference source 4 according to the signal arrangement of the communication signal will be described in more detail with reference to FIGS. 83 and 84A to 84C. That is, the control circuit 6 has a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting, and based on the n-bit data, a partial on / A configuration example will be described in which the duty ratio is calculated and the reference value is determined according to the calculated partial on-duty ratio.

  FIG. 83 is a block diagram showing a configuration example of the control circuit 6 and the signal generation circuit SG in FIG. 1A or FIG. In the figure, the control circuit 6 includes a shift register 6a, a calculation unit 6b, a correction unit 6c, a conversion unit 6d, and a reference value setting unit 6e.

  The shift register 6a shifts and holds n (n is an integer of 2 or more) bit data of the communication signal generated by the signal generation circuit SG.

  The calculation unit 6b calculates a partial on-duty ratio of the communication signal based on the n-bit data held in the shift register 6a. The partial on-duty ratio is, for example, for (i) a period obtained by combining the most recent off period (period in which bit 0 continues) and the on period immediately before the off period (period in which bit 1 continues). The ratio of the on period may be sufficient. Alternatively, “partial on-duty ratio” may be (ii) a moving average value of the most recent n bits in the communication signal, or a moving average value of a predetermined number of bits in n bits.

  When calculating the moving average value as a partial on-duty ratio, the arithmetic unit 6b simply calculates the addition average for the n bits of the shift register 6a.

  The correction unit 6c corrects the partial on-duty ratio calculated by the calculation unit 6b. If the calculation methods such as (i) and (ii) above are different, the calculation results are also different, and correction is performed by the correction unit 6c.

  The conversion unit 6d converts the corrected partial on-duty ratio into a corresponding appropriate reference value. That is, the conversion unit 6d determines an appropriate reference value according to the corrected partial on-duty ratio.

  The reference value setting unit 6e sets the determined reference value in the reference source 4. That is, the reference value setting unit 6e controls the reference source 4 so that the reference source 4 outputs the determined reference value.

  Next, a configuration example of the signal generation circuit SG will be described.

  83, the signal generation circuit SG includes a signal source 6f, a determination unit 6g, a standby control unit 6h, and a drive unit 6i.

The signal source 6f generates a communication signal. For example, the signal source 6f may repeatedly generate a communication signal including the ID of the illumination light communication device, or may generate a communication signal that includes the ID of the illumination light communication device and modulates information from the outside. Good.

  The determination unit 6g determines whether or not the latest bit output from the signal source 6f is “1”. If the bit immediately before the latest bit is 0, the latest bit output from the signal source 6f causes a rising edge in the current waveform of the load circuit 53 that is a light source. If the bit immediately before the latest bit is 1, the conduction state of the load circuit 53, which is the light source, continues in the interval of the latest bit output from the signal source 6f.

  When the determination unit 6g determines that the latest bit is “1”, the standby control unit 6h drives the switch SW by the latest bit, that is, outputs the latest bit to the gate of the switch SW. 6 is made to wait until a ready signal is received. In this standby, before the rising edge occurs in the current waveform of the load circuit 53 that is a light source, the setting of the reference value according to the partial on-duty ratio immediately before the rising edge is completed in the current suppression circuit 1. This is to make it happen.

  The drive unit 6 i outputs the latest bit “1” to the gate of the switch SW at the timing when the ready signal is received from the control circuit 6.

  Instead of determining whether or not the latest bit output from the signal source 6f is “1”, the determination unit 6g determines whether or not the latest two bits output from the signal source 6f are “01”. In other words, it may be determined whether the latest bit is 1 and the immediately preceding bit is 0. In this way, the determination unit 6g determines whether or not a rising edge occurs in the current waveform of the load circuit 53, which is a light source, based on the latest bit output from the signal source 6f.

  Subsequently, an operation example of the control circuit 6 will be described in more detail.

  FIG. 84A is a flowchart illustrating a processing example of the control circuit in FIG. 1A. In FIG. 84A, at the start of visible light communication in the illumination light communication apparatus (for example, when the illumination light communication apparatus is powered on), the control circuit 6 first initializes (for example, resets) the shift register 6a (S40). The initial value of the reference value is set in the reference source 4 (S41). This initial value may be a reference value corresponding to an average on-duty ratio of 75% of the communication signal, for example.

  When the control circuit 6 inputs 1 bit of the communication signal generated serially by the signal source 6f of the signal generation circuit SG to the shift register 6a (S42), the control circuit 6 determines whether or not the input 1 bit is 1 (S42). S43).

  When it is determined that the input 1 bit is 1, the control circuit 6 obtains the average value of the n-bit data held by the shift register 6a as a partial on-duty ratio (S44). This average value is a moving average value obtained by shifting n bits of the communication signal as serial data for each loop process (S42 to S47) in FIG. 84A. Furthermore, the control circuit 6 corrects the moving average value (S45), obtains a reference value from the correction result, sets the reference value in the reference source 4 (S46), and outputs a ready signal to the signal generation circuit SG (S46). S47). As a result of the ready signal being output, one bit input in step S42 is output to the gate of the switch SW. In step S46, the current setting value and the reference value of the current suppression circuit 1 are obtained from the corrected moving average value by calculating using the relational expression (2) described later, or by previously storing a numerical value table. It may be prepared. This numerical value table may be, for example, a table in which the corrected moving average value is associated with the reference value.

  Next, a configuration example of the shift register 6a will be described. FIG. 84B is an explanatory diagram showing a configuration example of the shift register 6 a in the control circuit 6. FIG. 84B illustrates an 8-bit shift register 6a. The shift register 6a has a serial-in terminal for inputting 1-bit data, a parallel-out terminal for outputting 8-bit data, and a serial-out terminal for outputting 1-bit data. In the retained 8-bit data, they are called bits b1, b2,..., B8 in order from the serial-in terminal side. Bit b1 is the latest bit output from the signal source 6f. At the timing when the latest bit is input to the bit b1 from the serial-in terminal, the bit b2 is input to the gate of the switch SW. The bit b1 is output to the gate of the switch SW at the timing when the ready signal in step S47 of FIG. 84A is output.

  Next, a specific example of correction in step S45 of FIG. 84A will be described.

  FIG. 84C is a flowchart showing an example of correction in step S45 of FIG. 84A. When the moving average value is obtained in step S44, the latest bit b1 of the shift register 6a is 1 as determined in step S43. In FIG. 84C, the control circuit 6 first multiplies the moving average value by the coefficient k1 (S12) if the bit b2 immediately before the latest bit b1 is 0 (S11: yes), and further determines the bit b3 immediately before the bit b2. If 0 (S13: yes), the coefficient k1 is multiplied again (S14). That is, when the first bit b1 from the end of the shift register 6a is 1 and the second bit b2 and subsequent bits are 0 that continues for 1 bit or more, the control circuit 6 sets a coefficient k1 smaller than 1 to the moving average value. The power is the same as the number of consecutive 0 bits. Here, the coefficient k1 may be 0.9, for example.

  Next, in the case of no in step S11, if the bit b3 is 1 (S15: yes), the control circuit 6 multiplies the moving average value by the coefficient k2 (S16), and if the bit b4 is 1 (S17). : Yes), the coefficient k2 is multiplied again (S18). That is, the control circuit 6 sets the moving average value to 1 when the first bit b1 from the end of the shift register 6a is 1 and is 1 that continues for 1 bit or more after the second bit b2 or the third bit b3. The larger coefficient k2 is raised to the same number as the number of consecutive 1 bits after bit b2 or b3. Here, the coefficient k2 may be 1.03, for example.

  By such correction, it is possible to keep the moving average value in all assumed data arrays in a range of approximately 0.5 to 0.9. The above correction method is merely an example, and selection according to necessary dynamics is necessary. In particular, the coefficient to be multiplied varies depending on the data transmission format used and the power supply circuit conditions. Therefore, it is necessary to examine the validity under actual conditions.

  With such a configuration, it is possible to more appropriately suppress overshoot that occurs in the current flowing through the load circuit 53.

[11.4 Operation of Illumination Optical Communication Device]
About the operation | movement of the illumination light communication apparatus comprised as mentioned above, the simulation result shown, for example in FIGS. 5-14 corresponds. The same operation as in the first embodiment is performed.

  As described above, the illumination light communication apparatus according to Embodiment 11 modulates the illumination light, the light source 53 that emits illumination light, the switch SW that is connected in series with the light source, and that interrupts the current flowing through the light source. Therefore, a signal generation circuit SG for generating a binary communication signal for controlling on and off of the switch, and the light source and the switch SW are connected in series so as not to exceed a current set value corresponding to a reference value. A current suppression circuit 1 that suppresses a current flowing through the light source, and the current suppression circuit 1 is connected in series to the reference source 4 that outputs the reference value, the light source, and the switch, and flows to the light source. A transistor 2 that suppresses current based on the reference value, and a shift register 6a that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting. And a control circuit 6 for calculating a partial on-duty ratio of the communication signal based on the n-bit data, and the reference according to the calculated partial on-duty ratio. Determine the value.

  According to this, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the switch SW is turned on can be reduced, thereby reducing the reception error in the receiving apparatus. In addition, a partial on-duty ratio is calculated using a shift register, and the reference value is determined according to the calculated partial on-duty ratio. Therefore, the reference value is more dynamically changed to an appropriate value. be able to.

  Here, the control circuit 6 sets the reference value to a first value when the partial on-duty ratio is a first ratio, and the partial on-duty ratio is larger than the first ratio. When the ratio is 2, the reference value is set to a second value smaller than the first value, and the current setting value corresponding to the second value is smaller than the current setting value corresponding to the first value. May be.

  According to this, when the magnitude of the overshoot depends on the partial on-duty ratio, it is possible to appropriately suppress the overshoot.

  Here, the control circuit 6 may change the reference value so that the current set value is inversely proportional to the partial on-duty ratio.

  Here, the control circuit may change the reference value so as to satisfy the following expression.

  I1 = (Iave / ONd) × 100

  Here, I1 is the current setting value, Iave is an average current flowing through the light source when the illumination light is not modulated by the switching of the switch, and ONd is a partial on-duty ratio ( The unit is%).

  According to this, the brightness of the illumination light when the overshoot is suppressed and the illumination light is not modulated is substantially equal to the brightness of the illumination light when the illumination light is modulated. Can be.

  Here, the control circuit may change the reference value so as to satisfy the following expression.

  (Iave / ONd) × 100 ≦ I1 <Ip

  Here, Iave is an average current flowing through the light source when illumination light is not modulated by the on / off of the switch, ONd is a partial on-duty ratio of the communication signal, and I1 is the current set value. Yes, Ip is the peak value of the current flowing through the light source when the current suppression circuit does not suppress.

  Here, the control circuit 6 calculates a moving average value as a partial on-duty ratio with respect to data of a predetermined number of bits from the end of the shift register 6a, and the n-bit data held in the shift register. The moving average value may be corrected based on the bit pattern, and a reference value corresponding to the corrected moving average value may be determined.

  According to this, since the overshoot generated in the current flowing through the light source at the moment when the switch is turned on from the off state is reduced, the reception error in the receiving device can be reduced. This is because when the power supply circuit of the illumination light communication device is a current feedback type, the magnitude of the overshoot depends on the partial on-duty ratio, and the output voltage gradually increases during the off period. Yes. Due to the feedback of the diode, the reference value also increases in accordance with the output voltage that gradually increases during the off period, so that overshoot can be appropriately reduced.

  Here, in the correction of the moving average value, when the first bit from the end of the shift register is 1, and the second and subsequent bits are 0s in which the control bit 6 is 1 or more consecutive bits, the control circuit 6 performs the moving A coefficient smaller than 1 may be raised to the average value by the same number as the number of consecutive 0 bits.

  Here, in the correction of the moving average value, the control circuit 6 is 1 in which the first bit from the end of the shift register 6a is 1, and the second bit or the third bit and thereafter is 1 in which 1 bit or more continues. In some cases, a coefficient greater than 1 may be raised to the moving average value by the same number as the number of consecutive 1 bits.

  Here, instead of calculating the moving average value as a partial on-duty ratio, the control circuit 6 does not calculate the moving average value, but N (N is an integer greater than or equal to 2) value pulse position modulated average of the communication signal. The on-duty ratio (1- (1 / N)) × 100 (%) may be used.

  Here, the communication signal is N (N is an integer of 4 or more) value pulse position modulation, and the number of bits of the shift register 6a and the number of bits targeted for the moving average value are N bits or more. Also good.

  Here, the reference source 4 includes a constant voltage source 4a that generates a fixed voltage, a plurality of resistor elements that divide the constant voltage source (for example, some of R1, R6 to R7, and R11 to R14), and the resistor One or more switch elements (for example, some of S01 to S03) connected in series or in parallel with the elements, and the control circuit 6 turns on and off the one or more switch elements according to the corrected value. You may control off.

  Here, the illumination light communication device includes a power supply circuit 52a that supplies current to the light source, the switch, and the current suppression circuit that are connected in series, and the power supply circuit 52a has a constant average value of the supplied current. Feedback control may be performed to achieve the above.

  Here, the power supply circuit 52a includes a DC-DC converter 64 having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switch element 81, and according to the difference between the detected value and a predetermined value. The switch element 81 may be turned on and off.

  The communication module according to the eleventh embodiment is a communication module 10 that modulates illumination light that can be attached to and detached from the illumination device, the switch SW connected in series with the light source of the illumination device, and the illumination light. A signal generation circuit SG for generating a binary communication signal for controlling on and off of the switch for modulation, and a current suppression circuit connected in series with the light source and the switch SW to suppress a current flowing through the light source The current suppression circuit 1 is connected in series with a reference source 4 that outputs the reference value, the light source and the switch, and a transistor 2 that suppresses a current flowing through the light source based on the reference value. A control circuit 6 having a shift register 6a for holding the first n (n is an integer of 2 or more) bit data of the communication signal while shifting, Serial control circuit 6, the calculated partial on-duty ratio of the communication signal on the basis of n-bit data, determines the reference value in accordance with the calculated partial on-duty ratio.

  According to this, the communication module can be added to an existing lighting fixture. In other words, the existing lighting fixture can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than the case of installing a new optical communication lighting fixture. Further, since the overshoot generated in the current flowing through the light source is reduced at the moment when the switch is turned on from the off state, the reception error in the receiving device can be reduced.

(Embodiment 12)
In the twelfth embodiment, an illumination light communication device and a communication module that prevent malfunction of an overvoltage protection circuit when power is turned on even when optical communication with 100% modulation is performed will be described.

  Generally, the output voltage of the power supply circuit is high in a no-load state. The power supply circuit often includes an overvoltage protection circuit that stops operation when the output voltage exceeds the overvoltage protection level. When 100% modulation is performed in visible light communication, the switch element is turned off (that is, in the no-load state) until the modulation operation starts at the start-up time until the output voltage or output current of the power supply circuit rises when the power is turned on. The output voltage rises and exceeds the overvoltage protection level, and the power supply circuit may stop. In other words, there is a possibility that the overvoltage protection circuit malfunctions due to the no-load state and the power supply is stopped.

  For example, when a communication module that performs visible light communication is retrofitted to an existing lighting fixture, an overvoltage protection circuit in the power supply circuit may operate. Further, when designing a power supply circuit, there is a problem that it becomes difficult to design a margin of the overvoltage protection circuit.

  Therefore, one form of the illumination light communication apparatus according to the twelfth embodiment is an illumination light communication apparatus that modulates the two states of illumination light on and off to correspond to binary communication signals, and includes an overvoltage protection circuit. A power supply circuit having a light source connected to the power supply circuit for emitting the illumination light; a first switch element connected in series with the light source; a signal generation circuit for generating the binary communication signal; Bias for supplying a bias voltage for turning on the first switch element to the control terminal of the first switch element during the period until the signal generation circuit starts the operation of generating the communication signal A circuit and a second switch element connected to a control terminal of the first switch element and turned on and off according to the communication signal. The bias circuit is also a modification of the current suppression circuit already described.

  In addition, one form of the communication module according to Embodiment 12 is a communication module that performs modulation so that two states of illumination light emitted from the illumination device are turned on and off in correspondence with a binary communication signal, and is detachable from the illumination device. A light source that is connected in series to the light source of the illumination device and emits the illumination light, a first switch element connected in series with the light source, a signal generation circuit that generates the binary communication signal, and a power source A bias circuit that supplies a bias voltage for turning on the first switch element to a control terminal of the first switch element after being turned on and until the signal generation circuit starts an operation of generating the communication signal; A second switch element connected to a control terminal of the first switch element, wherein the second switch element is turned on and off in accordance with the communication signal after the signal generating circuit starts operating. Provided with a door.

  According to the illumination light communication device and the communication module according to the present embodiment, it is possible to prevent malfunction of the overvoltage protection circuit when the power is turned on.

[12.1 Configuration Example of Illumination Optical Communication Device]
First, an example of the circuit configuration of the illumination light communication apparatus according to the twelfth embodiment will be described.

  FIG. 85 is a circuit diagram showing a configuration example of the illumination light communication apparatus in the twelfth embodiment. The illumination light communication apparatus includes a power supply circuit 51 a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and the communication module 10.

  The power supply circuit 51a includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64, a detection resistor 66, and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

  The power supply circuit 51 a performs full-wave rectification on a commercial power supply (for example, AC 100 V) with a rectifier bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected across the output of the DC-DC converter 64. That is, the smoothing capacitor 65 is connected between the power supply line of the power supply circuit 51a and the ground line. The load circuit 53 and the first switch element 2a are connected in series between the power supply line of the power supply circuit 51a and the ground line.

  The power supply circuit 51a has a function of detecting the current flowing through the load circuit 53 directly or indirectly and controlling the current value to be constant. In FIG. 85, this function is based on the detection resistor 66 and the constant current feedback circuit 67 for directly detecting the current of the load circuit 53. The constant current feedback circuit 67 includes an amplifier 69, a reference voltage source 72 connected to the positive input terminal of the amplifier 69, an input resistor 68 connected to the negative input terminal of the amplifier 69, an output terminal of the amplifier 69, and the amplifier 69. Gain adjustment resistor 71 and phase compensation capacitor 70 connected between the negative input terminals. The constant current feedback circuit 67 compares the voltage drop of the detection resistor 66 with the voltage of the reference voltage source 72 by the amplifier 69, amplifies the difference, and feeds back to the control unit of the DC-DC converter 64. That is, negative feedback control is applied to the DC-DC converter 64 so that the voltage drop of the detection resistor 66 matches the reference voltage. Further, the gain is set by the voltage dividing ratio of the resistor 71 connected between the negative input terminal and the output terminal of the amplifier 69 and the input resistor 68, and the capacitor 70 provided in parallel with the resistor 71 has an integral for phase compensation. Acts as an element.

  The smoothing capacitor 65 is connected between the power supply line of the power supply circuit 51a and the ground line, and smoothes the output of the power supply circuit 51a.

  Load circuit 53 includes a plurality of light emitting diodes connected in series. The plurality of light emitting diodes are light sources that emit illumination light. This illumination light is modulated by a binary communication signal.

  The communication module 10 includes a bias circuit 1c, a first switch element 2a, a second switch element 3a, an inverter 5a, and a signal generation circuit SG.

  The first switch element 2a is connected in series with a load circuit 53 that is a light source, and modulates illumination light emitted from the light source by 100% by turning on and off. The 100% modulation here means that the illumination light is modulated in two states, a lighting state and a light-off state. The first switch element 2a in FIG. 85 is a normally-off type switch transistor. That is, when a voltage higher than the threshold is not applied between the source and gate of the first switch element 2a, the first switch element 2a is turned off. One end of the first switch element 2 a is connected to the load circuit 53. The other end of the first switch element 2a is connected to a ground line. The control terminal of the first switch element 2a is connected to the second switch element 3a and receives a bias voltage from the bias circuit 1c.

  The bias circuit 1c has a bias voltage for turning on the first switch element 2a in a period after the illumination light communication device is turned on until the signal generation circuit SG starts an operation of generating a communication signal. This is supplied to the control terminal of the first switch element 2a. This bias voltage prevents the power supply circuit 51a from being in a no-load state during this period, and prevents the output voltage of the power supply circuit 51a from rising and exceeding the overvoltage protection level.

  The second switch element 3a is turned on and off according to the communication signal. Specifically, the second switch element 3a is a normally-off transistor. One end of the second switch element 3a is connected to the control terminal of the first switch element 2a. The other end of the second switch element 3a is connected to a ground line. The control terminal of the second switch element 3a is connected to the signal generation circuit SG via the inverter 5a, and an inverted communication signal is input.

  Thus, when the communication signal is at a low level, the second switch element 3a is on, and the control terminal of the first switch element 2a is at a low level. As a result, the first switch element 2a is off.

  When the communication signal is at a high level, the second switch element 3a is off, and the bias voltage level is maintained at the control terminal of the first switch element 2a. As a result, the first switch element 2a is on.

  In the period after the power is turned on, since the output level of the inverter 5a is low, the second switch element 3a is off, and the control terminal of the first switch element 2a is at the bias voltage level. Since the bias voltage increases as the output voltage rises from power-on, the first switch element 2a is turned on before the operation of the signal generation circuit SG is started. As a result, the first switch element 2a is on during the period when the power is turned on.

  Thus, although the first switch element 2a is a normally-off type switch due to the bias voltage, it apparently behaves as normally-on during the above period, so that the no-load state when the power is turned on is eliminated. As a result, it is possible to prevent malfunction of the overvoltage protection circuit when the power is turned on. In addition, the margin of the overvoltage protection level and the degree of freedom in designing the margin can be increased.

  The signal generation circuit SG generates a binary communication signal. This communication signal may be, for example, an inverted 4PPM signal defined by JEITA-CP1223.

[12.2 Configuration Example of Bias Circuit 1c]
As shown in FIG. 85, the bias circuit 1c includes a first resistance element 6r, a second resistance element 7r, a capacitor 8, and a resistance 4r.

  The first resistance element 6r and the second resistance element 7r are connected in series between the power supply line of the power supply circuit 51a and the ground line. The connection point between the first resistance element 6r and the second resistance element 7r is electrically coupled to the control terminal of the first switch element 2a, that is, connected via the input resistance 4r. The bias voltage can be easily generated as a divided value of a voltage dividing circuit including the first resistance element 6r and the second resistance element 7r.

  In addition, power is supplied from the power supply line of the power supply circuit 51a to the signal generating circuit SG and the inverter 5a through a connection point between the first resistance element 6r and the second resistance element 7r. That is, the connection point between the first resistance element 6r and the second resistance element 7r is that the capacitor 8 for supplying the power supply voltage to the signal generation circuit SG and the inverter 5a is connected in parallel to the second resistance element 7r, and the connection point (The power supply voltage of the signal generation circuit SG and the inverter 5a) is stabilized. As described above, the divided voltage value of the voltage dividing circuit including the first resistance element 6r and the second resistance element 7r can be used as the power supply voltage of the signal generation circuit SG and the inverter 5a.

[12.3 Configuration Example of DC-DC Converter]
Next, a configuration example of the power supply circuit 51a having an overvoltage protection circuit will be described.

  FIG. 86 is a diagram illustrating a circuit example of the DC-DC converter 64 having the overvoltage protection circuit 64a according to the twelfth embodiment. The DC-DC converter 64 shown in the figure includes input terminals i1, i2, output terminals o1, o2, feedback input terminal FB, transformer TR1, switch SW1, diode D1, capacitor C1, buffer b1, error amplifier A1, resistors R1, R2. , A triangular wave generation circuit GN, and an overvoltage protection circuit 64a.

  The input terminals i1 and i2 are connected to the two output terminals of the rectifier bridge 62 in FIG. 85 and both ends of the capacitor 63, and a rectified and smoothed DC voltage is applied thereto.

  The output terminals o1 and o2 are connected to both ends of the smoothing capacitor 65 in FIG. The output terminal o1 is connected to the power supply line, and the output terminal o2 is connected to the ground line.

  The feedback input terminal FB is connected to the constant current feedback circuit 67 of FIG. 85, and receives a feedback signal from the amplifier 69. This feedback signal indicates the magnitude of the output current of the power supply circuit 51a.

  The DC-DC converter 64 is a so-called flyback converter, and transmits electric energy to the secondary side by the switching operation of the switch SW1 connected in series to the primary winding of the transformer TR1, and is transmitted by the diode D1 and the capacitor C1. A DC voltage is output between the output terminals o1 and o2.

  The switch SW1 performs a switching operation according to the triangular wave signal generated by the triangular wave generation circuit GN and the feedback signal. That is, when the level of the triangular wave signal generated by the triangular wave generation circuit GN does not reach the level of the feedback signal, the switch SW1 is in the off state, and when the level of the triangular wave signal exceeds the level of the feedback signal, the switch SW1 is on. State. For example, when the triangular wave signal repeats the same triangular wave at a constant frequency, the output signal of the error amplifier A1 (comparator) is a PWM-modulated pulse signal whose pulse width is determined according to the level of the feedback signal at the positive input terminal of the error amplifier A1. become.

  In the overvoltage protection circuit 64a, the error amplifier A2 (comparator) compares the output voltage of the output terminal o1 with the overvoltage protection level defined by the constant voltage source Vr. The output signal of the error amplifier A2 is inverted from the low level to the high level when the output voltage of the output terminal o1 exceeds the overvoltage protection level. The latch circuit La latches and outputs the high level when the output signal of the error amplifier A2 is inverted. When the latch circuit La outputs a high level, the AND circuit G1 forcibly sets the input signal of the buffer b1 to the low level by killing the pulse signal of the error amplifier A1. When the input signal of the buffer b1 is forcibly set to the low level, the output signal of the buffer b1 is also forcibly set to the low level. As a result, the switching operation of the switch SW1 is stopped while the switch SW1 is off.

  In this way, the overvoltage protection circuit 64a stops the power supply operation of the power supply circuit 51a when the output voltage of the power supply circuit 51a becomes overvoltage, that is, exceeds the overvoltage protection level.

[12.4 Operation]
The operation of the illumination light communication apparatus in the twelfth embodiment configured as described above will be described.

  FIG. 87 is a time chart of each part potential of the illumination light communication apparatus according to the twelfth embodiment. In FIG. 8, (a) converter oscillation output indicates the time course of the potential at the output terminal of the error amplifier A1 or the control terminal of the switch SW1 in FIG. (B) The modulation control power supply voltage indicates the passage of time of the power supply voltage supplied to the signal generation circuit SG from the connection point between the first resistance element 6r and the second resistance element 7r in FIG. 85, and the first switch element. 2B shows the time lapse of the bias voltage input to the control terminal 2a. (C) The modulation signal output indicates the time history of the output signal of the signal generation circuit SG, that is, the communication signal. (D) The LED current indicates the time course of the current flowing through the light source, that is, the load circuit 53. (E) The output voltage with modulation indicates the time course of the output voltage of the power supply circuit 51a. L1 in the figure indicates the modulation control operation level, that is, the level of the power supply voltage at which the signal generation circuit SG starts operating. L2 indicates the overvoltage protection level of the overvoltage protection circuit 64a and corresponds to the reference level of the constant voltage source Vr in FIG.

  Time T1 in the figure indicates the power-on timing of the power supply circuit 51a. From time T1, (a) the converter oscillation output starts to be output effectively, and (e) the output voltage with modulation begins to rise.

  At time T2, (d) the LED current starts to flow. That is, the period from the time T2 to the time T3 is a period in which the first switch element 2a is turned on by the bias voltage, and is a period after the power is turned on until the signal generation circuit SG starts the operation of generating the communication signal. It is a period. At time T2, (e) the output voltage with modulation decreases slightly because the LED current starts to flow. As (e) the output voltage with modulation decreases, (b) the modulation control voltage also decreases slightly.

  During the period from time T2 to T3, since the first switch element 2a is turned on by the bias voltage, the no-load state is canceled and the LED current flows. Therefore, (e) the output voltage with modulation exceeds the overvoltage protection level L2, That is, the malfunction of the overvoltage protection circuit 64a is prevented.

  At time T3, (b) the modulation control voltage exceeds the modulation control operation level, (c) the modulation signal output becomes valid, and (d) the LED current is switched.

  After time T3, the illumination light communication apparatus is in a steady operation state.

  As described above, the illumination light communication apparatus according to the twelfth embodiment is an illumination light communication apparatus that performs modulation to make the two states of illumination light on and off correspond to binary communication signals, and an overvoltage protection circuit. A power circuit 51a having a power source, a load circuit 53 that is connected to the power circuit 51a and emits the illumination light, a first switch element 2a connected in series with the light source, and a binary communication signal. And a bias voltage for turning on the first switch element 2a in a period after the power is turned on and until the signal generation circuit starts an operation of generating the communication signal. A bias circuit 1c for supplying a control terminal of the first switch element 2a, and a second switch element 3 connected to the control terminal of the first switch element 2a and turned on and off according to the communication signal Provided with a door.

  According to this configuration, even if the first switch element 2a is a normally-off type switch due to the bias voltage, it apparently behaves as normally-on, so that the no-load state at the time of power-on is eliminated. As a result, it is possible to prevent malfunction of the overvoltage protection circuit when the power is turned on. In addition, the margin of the overvoltage protection level and the degree of freedom in designing the margin can be increased.

  Here, the overvoltage protection circuit 64a may stop the power supply operation when the output voltage becomes an overvoltage.

  According to this configuration, it is possible to prevent the power supply circuit from being stopped due to malfunction of the overvoltage protection circuit when the power is turned on.

  Here, the first switch element 2a is a normally-off type switch transistor, the bias circuit 1c includes a first resistor element 6r, and one end of the first resistor element 6r is connected to the power line of the power circuit 51a. The other end of the first resistance element 6r is connected directly or indirectly to the control terminal of the first switch element 2a, and one end of the second switch element is connected to the first switch element 2a. And the other end of the second switch element may be connected to a ground line.

  According to this configuration, a bias voltage is supplied from the other end of the resistance element to the control terminal of the first switch element 2a. The bias circuit 1c for supplying the bias voltage can be configured by a simple resistance element. The first switch element 2a behaves as if it is normally on due to the bias voltage.

  Here, the first switch element 2a is a normally-off type switch transistor, and the bias circuit 1c includes a first resistor element 6r and a first resistor element 6r connected in series between a power supply line and a ground line of the power supply circuit. A connection point between the first resistance element 6r and the second resistance element 7r is electrically coupled to a control terminal of the first switch element 2a, and from the power line of the power circuit, Electric power may be supplied to the signal generation circuit via a connection point between the first resistance element 6r and the second resistance element 7r.

  According to this configuration, the first switch element 2a behaves as if it is normally on due to the bias voltage. Further, the bias circuit 1c can be configured by a simple voltage dividing circuit including a first resistance element and a second resistance element. Further, the bias voltage can be easily generated as a divided value of the voltage dividing circuit.

  Here, the bias circuit 1c includes a capacitive element 8 connected in parallel to the second resistance element, and a connection point between the first resistance element 6r and the second resistance element 7r from the power supply line of the power supply circuit. Power may be supplied to the signal generation circuit via

  According to this configuration, the divided voltage value of the voltage dividing circuit including the first resistance element and the second resistance element can be used as the power supply voltage of the signal generation circuit.

  The communication module according to the twelfth embodiment is a communication module that performs modulation so that two states of turning on and off the illumination light emitted from the lighting device correspond to a binary communication signal, and is detachable from the lighting device. A load circuit 53 that is a light source that is connected in series to the light source of the illumination device and emits the illumination light, a first switch element 2a that is connected in series with the light source, and a signal generation circuit SG that generates the binary communication signal. A bias voltage for turning on the first switch element 2a is supplied to the control terminal of the first switch element 2a after the power is turned on and until the signal generation circuit starts an operation of generating the communication signal. A bias circuit 1c and a second switch element 3a connected to a control terminal of the first switch element 2a, and after the signal generation circuit SG starts operating, And a second switching element 3a for turning on and off according to Patent.

  According to this configuration, the communication module can be added to an existing lighting fixture. In other words, the existing lighting fixture can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than the case of installing a new optical communication lighting fixture. Further, it is possible to prevent malfunction of the overvoltage protection circuit when the existing lighting fixture equipped with the communication module is turned on.

(Embodiment 13)
Next, the illumination light communication apparatus in the thirteenth embodiment will be described. In the twelfth embodiment, the example in which the first switch element 2a is a normally-off type switch transistor has been described. On the other hand, in the thirteenth embodiment, an example in which the first switch element is a normally-on type switch transistor will be described.

  FIG. 88 is a circuit diagram showing a configuration example of the illumination light communication apparatus in the thirteenth embodiment. This figure differs from FIG. 85 in the circuit configuration of the communication module 10. Hereinafter, different points will be mainly described.

  The communication module 10 of FIG. 88 is different from that of FIG. 85 in that the first switch element 2b is provided instead of the first switch element 2a and the circuit configuration of the bias circuit 1c is different.

  The first switch element 2b is not a normally-off type but a normally-on type switch transistor.

  The bias circuit 1c supplies a forward bias voltage to the control terminal of the first switch element 2b when the second switch element 3a is turned off after the power is turned on, and first when the second switch element 3a is turned on after the power is turned on. A bias voltage that is a reverse bias is supplied to the control terminal of the switch element 2b. Specifically, the bias circuit 1c includes a first resistance element 6r, a second resistance element 7r, a capacitor 8, a third resistance element 9, a fourth resistance element 9a, and a diode 11d.

  The first resistance element 6r and the second resistance element 7r are connected in series between the power supply line of the power supply circuit 51a and the ground line.

  The third resistance element 9 and the fourth resistance element 9a are connected in series. The third resistance element 9 and the fourth resistance element 9a connected in series are electrically coupled between the power supply line of the power supply circuit and the connection point between the first resistance element 6r and the second resistance element 7r. The Here, being electrically coupled includes a case where they are directly connected and a case where they are indirectly connected. For example, one end of the fourth resistance element 9a in FIG. 88 is indirectly connected to a connection point between the first resistance element 6r and the second resistance element 7r via the diode 11d.

  One end of the first switch element 2b is connected to the power supply line, and the other end of the first switch element 2b is electrically coupled to a connection point between the first resistance element 6r and the second resistance element 7r. The control terminal of the first switch element 2b is connected to a connection point between the third resistance element 9 and the fourth resistance element 9a.

  One end of the second switch element 3a is connected to the control terminal of the first switch element 2b, and the other end of the second switch element 3a is connected to the ground line.

  As described above, the bias circuit 1c includes a two-stage voltage dividing circuit including a voltage dividing circuit including the first and second resistance elements 6r and 7r and a voltage dividing circuit including the third and fourth resistance elements 9 and 9a. Since the bias voltage becomes reverse bias when the second switch element 3a is on, the first switch element 2b is turned off. Since the second switch element 3a is off during the period after the power is turned on and before the signal generation circuit SG starts the operation of generating the communication signal, the first switch element 2b is turned on and the no-load state is established. It will be resolved.

  The power supply voltage of the signal generation circuit SG is supplied from the power supply line of the power supply circuit 51a to the signal generation circuit SG through a connection point between the first resistance element 6r and the second resistance element 7r. For this reason, the bias circuit 1c includes a capacitor 8 connected in parallel to the second resistance element in order to stabilize the power supply voltage supplied to the signal generation circuit SG.

  As described above, the illumination light communication apparatus according to the thirteenth embodiment is an illumination light communication apparatus that performs modulation to make the two states of illumination light on and off correspond to binary communication signals, and an overvoltage protection circuit. A power circuit 51a having a power source, a load circuit 53 that is connected to the power circuit 51a and emits the illumination light, a first switch element 2b connected in series with the light source, and a binary communication signal. A bias voltage for turning on the first switch element 2b in a period after the power is turned on and before the signal generation circuit starts an operation of generating the communication signal. A bias circuit 1c for supplying a control terminal of the first switch element 2b, and a second switch element 3 connected to the control terminal of the first switch element 2b and turned on and off in accordance with the communication signal Provided with a door.

  Here, the first switch element 2b is a normally-on type switch transistor, and the second switch element is connected between a control terminal of the first switch element 2b and a ground line, and the bias circuit 1c. Supplies a bias voltage for forward bias to the control terminal of the first switch element 2b when the second switch element is off after power-on, and the first switch when the second switch element is on after power-on. You may supply the bias voltage used as a reverse bias to the control terminal of the element 2b.

  According to this configuration, since the normally-on type switch transistor is used, the no-load state at the time of turning on the power is eliminated, and the malfunction of the overvoltage protection circuit can be prevented.

  Here, the bias circuit 1c includes a first resistance element 6r and a second resistance element 7r connected in series between a power supply line and a ground line of the power supply circuit, and a third resistance element 9 connected in series. And the fourth resistance element 9a, and the third resistance element 9 and the fourth resistance element 9a are connected to the power supply line of the power supply circuit and the first resistance element 6r and the second resistance element 7r. And one end of the first switch element 2b is connected to the power line, and the other end of the first switch element 2b is connected to the first resistance element 6r and the second resistance. Electrically coupled to a connection point with the element 7r, a control terminal of the first switch element 2b is connected to a connection point between the third resistance element 9 and the fourth resistance element 9a, and the second switch element One end of 3a is the control of the first switch element 2b Is connected to the child, the other end of the second switching element 3a may be connected to the ground line.

  According to this configuration, the bias circuit 1c includes a two-stage voltage dividing circuit including a voltage dividing circuit including first and second resistance elements and a voltage dividing circuit including third and fourth resistance elements. Since the bias voltage becomes reverse bias when the second switch element is on, the first switch element 2b is turned off.

  Here, the bias circuit 1c includes a capacitive element 8 connected in parallel to the second resistance element, and a connection point between the first resistance element 6r and the second resistance element 7r from the power supply line of the power supply circuit. Power may be supplied to the signal generation circuit via

  According to this configuration, the divided voltage value of the voltage dividing circuit including the first resistance element and the second resistance element can be used as the power supply voltage of the signal generation circuit.

(Comparative reference example)
Subsequently, an illumination light communication apparatus that does not include the bias circuit 1c is assumed as a comparative reference example, and will be described in comparison with the twelfth embodiment.

  FIG. 89 is a circuit diagram illustrating a configuration example of the illumination light communication apparatus in the comparative reference example. This figure differs from FIG. 85 or FIG. 88 in that the communication module 10 does not include the bias circuit 1c. That is, the communication module 10 includes a first switch element 73, a buffer 74, a signal generation circuit SG, and a capacitor 76c. The communication module 10 has a function of modulating illumination light by 100% with a communication signal, but does not have a function of the bias circuit 1c, so that the power supply circuit 51a is unloaded during the rising period when the power is turned on. Thus, the overvoltage protection circuit may malfunction.

  FIG. 90 is a time chart of potentials of respective parts of the illumination light communication apparatus in the comparative reference example of FIG. Here, the DC-DC converter 64 of FIG. 89 is assumed to be FIG.

  In FIG. 90, (a), (b), and (c) show the time history of each part voltage and current when the overvoltage protection circuit 64a does not malfunction. (A) The error amplifier oscillation output indicates the time history of the voltage at the output terminal of the error amplifier A1 or the control terminal of the switch SW1 in FIG. (B) The LED current indicates the time course of the current flowing through the light source, that is, the load circuit 53. (C) The normal output voltage indicates the time course of the output voltage of the power supply circuit 51a when the overvoltage protection circuit 64a is not malfunctioning.

  At time T1, power is turned on, (a) the converter oscillation output starts to be output effectively, and (b) LED current starts to flow at time T2. At time T2, (c) the normal output voltage does not reach the overvoltage protection level, and (b) the LED current starts to flow and the no-load state is eliminated. That is, the period from time T1 to time T2 is a no-load state, but the period from time T2 to time T3 is canceled. (C) Since the no-load state is eliminated while the normal output voltage has not reached the overvoltage protection level, the malfunction of the overvoltage protection circuit 64a does not occur.

  On the other hand, (d), (e), and (f) in FIG. 90 show the time course of the potential of each part when the overvoltage protection circuit 64a malfunctions. (D) The no-load output voltage indicates the time course of the output voltage of the power supply circuit 51a when the overvoltage protection circuit malfunctions. (E) The output of the latch circuit La indicates the time course of the output voltage of the latch circuit La of FIG. 86 when the overvoltage protection circuit malfunctions. (F) Oscillation output at latch indicates the time course of the voltage at the output terminal of the error amplifier A1 or the control terminal of the switch SW1 when the overvoltage protection circuit malfunctions. In (d), (e), and (f) of FIG. 90, the signal generation circuit SG rises slowly, and at time T3, the signal generation circuit SG does not start operation, that is, the LED current does not flow. It has become. Therefore, (d) the no-load output voltage exceeds the overvoltage protection level L1 at time T3, (e) the output of the latch circuit La becomes high level, and (f) the latched oscillation output stops. That is, at time T3, the overvoltage protection circuit 64a malfunctions and stops supplying power.

  As described above, if the period after the power is turned on and before the signal generation circuit SG starts the operation of generating the communication signal is in a no-load state, the overvoltage protection circuit 64a may malfunction.

(Modification)
Next, a modification of the illumination light communication device will be described.

  FIG. 91 is a circuit diagram showing a modification of the illumination light communication apparatus according to the twelfth or thirteenth embodiment. The illumination light communication apparatus shown in the figure is different from that shown in FIG. 85 or 88 in the circuit configuration inside the power supply circuit 51a. Hereinafter, different points will be mainly described.

  In the power supply circuit 51a of FIG. 85 or 88, the constant current feedback circuit 67 performs feedback control to make the average value of the output current constant, whereas the power supply circuit 51a of FIG. It is configured to perform threshold control.

  The power supply circuit 51a of FIG. 91 includes a rectifier bridge 62, a capacitor 63, and a DC-DC converter 64. The DC-DC converter 64 includes an inductor 80, a switch element 81, a diode 66d, a resistor 82, a signal source 83, a flip-flop 84, a comparator 85, a constant voltage source 86, a capacitor 87, a resistor 88, a diode 89, a driver 90, and a gate resistor. 91 is provided.

  The inductor 80, the switch element 81, and the diode 66d are basic circuit elements that constitute the DC-DC converter 64 as a buck converter.

  Control for turning on and off the switch element 81 is performed by the signal source 83, the flip-flop 84, the comparator 85, and peripheral circuits, and threshold control of the switching current of the switch element 81 is performed. That is, the switching current is also a current through the load circuit 53 (light emitting diode), and an alternative function of constant current feedback can be obtained by threshold control. The operation of such a DC-DC converter 64 will be described with reference to FIG.

  FIG. 92 is a waveform diagram showing threshold control of the switching current in the power supply circuit 51a of FIG. However, FIG. 92 shows waveforms when the terminals T1 and T2 are short-circuited in FIG. 91, or when the communication module 10 is connected to the terminals T1 and T2 and the transistor 2 is kept on. Is shown.

  In FIG. 92, the set signal S is a signal input from the signal source 83 to the set input terminal S of the flip-flop 84. The positive input signal is a signal input to the positive input terminal of the comparator 85 and indicates the voltage drop of the resistor 82, that is, the magnitude of the current flowing through the switch element 81. The reset signal R is a signal input to the reset input terminal of the flip-flop 84. The output signal Q is a signal output from the output terminal Q of the flip-flop 84. The output signal Q becomes a gate signal of the switch element 81 through the driver 90 and the resistor 91. The switching current is a current flowing through the switch element 81 and is detected as a voltage drop of the resistor 82.

  The set signal is generated by the signal source 83 and periodically goes high. When the set signal S goes high, the output signal Q of the RS flip-flop 84 goes high. The output signal Q is input to the gate of the switch element 81 (MOSFET) via the driver circuit 90 and the gate resistor 91. The switch element 81 is turned on when the output signal Q becomes high.

  The magnitude of the switching current (current flowing through the switch element 81) is detected as a voltage drop of the resistor 82, input to the positive input terminal of the comparator 85, and compared with the reference voltage Vref applied to the negative input terminal of the comparator 85. The When the voltage drop reaches the reference voltage Vref, the output of the comparator 85 becomes high, is converted into a pulse by a differentiation circuit composed of a capacitor 87 and a resistor 88, and is input to the reset input terminal of the RS flip-flop 84. At this time, the output signal Q of the flip-flop 84 becomes low and the switch element 81 is turned off. The detection of the magnitude of the current flowing through the switch element 81 as the switching current is an alternative to detecting the magnitude of the current flowing through the load circuit 53.

  Such switching current threshold control substitutes for the constant current feedback control of FIGS. 85 and 88, and works to make the average of the output current constant.

  Note that the power supply circuit 51a may perform the constant current feedback control of FIGS. 85 and 88, or may perform the switching current threshold control of FIG.

  Note that the power supply circuit 51a of FIG. 91 may include an overvoltage protection circuit 64a. 91 includes the overvoltage protection circuit 64a shown in FIG. 86, and the non-inverting input terminal of the AND circuit G1 is connected to the output terminal Q of the flip-flop 84.

  The power supply circuit 51a may perform feedback control for making the average value of the supplied current constant as shown in FIGS.

  Further, as shown in FIG. 91, the power supply circuit 51a includes a buck converter (that is, a DC-DC converter 64) having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switch element 81, and detects the detected value. The switch element 81 may be turned on and off according to the difference between the value and the predetermined value.

  The bias voltage may be a bias voltage having a biased voltage value when the first switch element 2a or 2b is a voltage drive type, or the first switch element 2a or 2b may be a current drive type. For example, a bias current having a biased current value may be used.

(Embodiment 14)
In Embodiments 14 to 18, a configuration in which the power supply circuit of the illumination light communication apparatus includes a constant voltage feedback circuit instead of the constant current feedback circuit will be described.

  When a constant voltage feedback type power supply is provided instead of the constant current feedback type power supply (for example, FIG. 50C or FIG. 1 of Patent Document 3), the LED current is unlikely to cause a large overshoot, and the above-described overshoot problem is avoided. It can be reduced. However, when 100% modulation visible light communication is performed when a constant voltage feedback type power supply is provided, there arises a problem that the brightness of illumination light decreases due to a decrease in average current due to the intermittent switching.

  In this embodiment, even when optical communication with 100% modulation is performed using a constant voltage feedback power supply, illumination light that suppresses a decrease in brightness due to intermittent switching and does not easily cause a reception error of the receiving device. A communication device and a communication module will be described.

  In order to modulate the illumination light, one form of the illumination light communication apparatus according to the present embodiment includes a light source that emits illumination light, a switch that is connected in series with the light source, and that interrupts the current flowing through the light source. A signal generation circuit for generating a binary communication signal for controlling on and off of the switch; and the light source connected in series with the light source and the switch so as not to exceed a current set value corresponding to a reference value. A current suppression circuit that suppresses a flowing current, a DC power supply circuit that applies a DC voltage to the light source, the switch, and the current suppression circuit connected in series, and an average value of the voltage applied to the current suppression circuit is constant. A constant voltage feedback circuit for controlling the DC power supply circuit.

  One embodiment of the communication module according to the present embodiment is a communication module that modulates illumination light that can be attached to and detached from the illumination device, the switch being connected in series with the light source of the illumination device, and the illumination light A signal generation circuit that generates a binary communication signal for controlling on and off of the switch to modulate the switch, and a current suppression circuit that is connected in series with the light source and the switch and suppresses a current flowing through the light source. , Comprising first, second and third terminals for attaching to and detaching from the lighting device, wherein the first terminal is connected to one end on the switch side of a series circuit comprising the switch and the current suppressing circuit, The second terminal is connected to a connection point between the switch and the current suppression circuit in the series circuit, and the third terminal is connected to the other end of the series circuit on the current suppression circuit side.

  According to the illumination light communication apparatus and the communication module according to the present embodiment, even when optical communication with 100% modulation is performed using a constant voltage feedback power supply, a decrease in brightness due to intermittent switching is suppressed, and There is an effect that it is difficult to cause a reception error of the receiving device.

[14.1 Configuration of Illumination Optical Communication Device]
First, the configuration of the illumination light communication apparatus according to the fourteenth embodiment will be described.

  FIG. 93A is a circuit diagram showing a configuration of the illumination light communication apparatus in the fourteenth embodiment. This illumination light communication device includes a power supply circuit 52b having a function of making the output constant voltage, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, a switch SW, a signal generation circuit SG, and a current suppression circuit 73. With.

  The power supply circuit 52b includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64 that is a DC power supply circuit, and a constant voltage feedback circuit 67a. The constant voltage feedback circuit 67a includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

  The power supply circuit 52b performs full-wave rectification on a commercial power supply (for example, AC 100V) with a rectifier bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected across the output of the DC-DC converter 64. A load circuit 53, a current suppression circuit 73, and a series circuit of switches SW are connected in parallel with the smoothing capacitor 65.

  The power supply circuit 52b feeds back the voltage applied to both ends of the current suppression circuit 73 to the DC-DC converter 64 of the power supply circuit 52b via the constant voltage feedback circuit 67a, and supplies the voltage applied to the current suppression circuit 73. It forms a kind of constant voltage power supply that is controlled constant.

  The smoothing capacitor 65 is connected between the outputs of the power supply circuit 52b and smoothes the output of the power supply circuit 52b.

  The load circuit 53 includes a plurality of light emitting diodes connected in series between the outputs of the power supply circuit 52b, and the output of the power supply circuit is supplied. The plurality of light emitting diodes are light sources that emit illumination light.

  The switch SW is added in series with the load circuit 53, and interrupts the current supplied from the power supply circuit 52b to the load circuit 53.

  The signal generation circuit SG generates a binary communication signal for controlling on and off of the switch SW in order to modulate the illumination light. The communication signal is input to the control terminal of the switch SW, and turns on and off the switch SW. Note that the signal generation circuit SG may repeatedly generate a communication signal indicating an ID unique to the illumination light communication device, or may generate a communication signal in accordance with a transmission signal input from an external device.

[14.2 Configuration of Current Suppression Circuit 73]
Next, a configuration example of the current suppression circuit 73 will be described.

  The current suppression circuit 73 is added in series with the load circuit 53 and the switch SW, and suppresses the magnitude of the current flowing through the load circuit 53. For example, the current suppression circuit 73 is connected in series with the load circuit 53 as the light source and the switch SW, and suppresses the current flowing through the load circuit 53 according to the reference value so as not to exceed the current setting value corresponding to the reference value. You may make it do. In this way, even when optical communication with 100% modulation is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. Furthermore, since the overshoot generated in the current flowing through the load circuit 53 that is the light source can be reduced at the moment when the switch SW is turned on from the off state, reception errors in the receiving device can be reduced.

  The current suppression circuit 73 includes a transistor 74 that is a MOSFET, a resistor 75 connected to the source, an error amplifier 77, a reference source 76, and a control circuit 6.

  The reference source 76 outputs a reference value to the plus input terminal of the error amplifier 77. The reference value defines the upper limit (current setting value) of the current flowing through the load circuit 53 that is a light source. For example, the reference value is proportional to the current setting value. The reference source 76 may output the reference value as a fixed value, or may output a variable reference value according to the arrangement pattern (for example, bit pattern) of communication signals generated by the signal generation circuit SG. .

  The transistor 74 is connected in series to the load circuit 53 that is a light source and the switch SW, and suppresses the current flowing through the load circuit 53 based on the reference value.

  The resistor 75 is a source resistor for detecting the magnitude of the current flowing through the load circuit 53. The source side terminal of the resistor 75 is connected to the negative input terminal of the error amplifier 77.

  In the error amplifier 77, the reference source 76 is connected to the plus input terminal, and the source of the transistor 74 is connected to the minus input terminal. The error amplifier 77 amplifies the difference between the reference value and the current value detected by the resistor 75, and outputs the amplified signal to the gate of the transistor 74.

  The control circuit 6 performs control to change the reference value of the reference source 76 in accordance with the arrangement pattern of the communication signals in order to output a variable reference value from the reference source 76. For example, the control circuit 6 calculates a partial on-duty ratio of the communication signal. When the calculated partial on-duty ratio is the first ratio, the control circuit 6 sets the reference value to the first value, When the on-duty ratio is a second ratio larger than the first ratio, the reference value is set to a second value smaller than the first value. At this time, the control circuit 6 may change the reference value so as to be inversely proportional to the partial on-duty ratio of the communication signal. The “partial on-duty ratio” is, for example, the ratio of the on-period to the total of the off-period immediately before and the on-period immediately before the off-period. Alternatively, the “partial on-duty ratio” may be substituted with the latest n-bit moving average value of the communication signal. In this way, when the magnitude of the overshoot generated in the current flowing through the load circuit 53 depends on the partial on-duty ratio, the overshoot can be suppressed more appropriately.

[14.3 Modification of Current Suppression Circuit 73]
Next, first to third modifications of the current suppression circuit 73 will be described.

  The current suppression circuit 73 in FIG. 93A is not limited to this configuration. . For example, the internal configuration of the current suppression circuit 73 may be the same as the first to third modifications of the current suppression circuit 1 illustrated in FIGS.

  93A is good also as the communication module 10 which can attach or detach the part containing the current suppression circuit 73, as shown to FIG. 93B.

  The communication module 10 includes a current suppression circuit 73, a switch SW, and a capacitor 65. The communication module 10 illustrated in FIG. 1A does not include the capacitor 65, but the communication module 10 illustrated in FIG. 93B includes the capacitor 65. The capacitor 65 is a relatively large capacity capacitor that smoothes the output voltage from the DC-DC converter 64. The communication module 10 can include an internal power supply circuit that generates the power supply voltage of the communication module 10 itself from the voltage across the capacitor 65. The internal power supply circuit may be the same as the control power supply 126 of FIG. 65, for example, and may be a three-terminal regulator. Thereby, even if the switch SW is off, the power supply voltage inside the communication module 10 can be continuously supplied stably, and it becomes easy to secure necessary power.

  Other communication modules 10 such as FIG. 1A and FIG. 30A may also include a capacitor 65 and an internal power supply circuit as shown in FIG. 93B.

[14.4 Operation of Illumination Optical Communication Device]
The operation of the illumination light communication apparatus configured as described above will be described using simulation results.

  94A, 94B, 97A, and 97B show simulation results using the current suppression circuit 1 of FIG. 2 instead of the current suppression circuit 73 in FIG. 93A. 94A is a diagram showing a first simulation result using the current suppression circuit 1 in FIG. 2 instead of the current suppression circuit 73 in FIG. 93A. In FIG. 94A, the capacitance value of the smoothing capacitor 65 is set to 20 uF, the frequency of the communication signal (modulation signal) from the signal generation circuit SG is set to 2.4 kHz, and the ON duty ratio of the switch SW is set to 60% and 75%. The LED current and the output voltage waveform are shown in the case of four variable values of 90% and 100%. Incidentally, the operating frequency of the DC-DC converter 64 is 65 kHz, and the average value of the load current (LED current) when not intermittent is set to 240 mA. In each of the on-duty ratios, the LED current waveform changes the clamp current value (peak value) while maintaining a rectangular wave, but the average value of the LED current is constant regardless of the on-duty ratio value ( 240 mA), the voltage source of the current suppression circuit 73 is varied. Note that the pulsation component of the output voltage increases as the on-duty ratio decreases.

  94B is a diagram showing a second simulation result using the current suppression circuit 1 of FIG. 2 instead of the current suppression circuit 73 in FIG. 93A. As shown in FIG. 94B, the voltage applied to the current suppression circuit 73 tends to have a higher peak value as the on-duty ratio is smaller. With this tendency, the brightness of the LED that is the load circuit 53 can be kept substantially constant regardless of whether the on-duty ratio is large or small.

  The relationship between the on-duty ratio and the brightness of the LED will be described with reference to FIGS. 95 and 96 showing comparative examples. FIG. 95 is a schematic diagram showing the relationship between two communication signals having different on-duty ratios and the LED current. However, FIG. 95 shows a case where the current suppression circuit 73 does not exist, or a case where the current setting value of the current suppression circuit 73 is fixed.

  The communication signal (1) shows a case where the on-duty ratio is relatively large, and the communication signal (2) shows a case where the on-duty ratio is relatively small. In either case of the communication signals (1) and (2), the average value (level II) of the LED current when the switch SW is intermittent is smaller than the average value (level I) when the switch SW is not intermittent. The level II of the communication signal (2) having a smaller on-duty ratio is smaller than the level II of the communication signal (1). That is, the value of the average current in the case of interruption is lower than the current value in the case of no interruption in proportion to the off-duty ratio. This indicates that if the current setting value is not controlled by the current suppression circuit 73, the brightness may change if the LED load is interrupted for optical communication.

  FIG. 96 is a diagram showing the relationship between the on-duty ratio and the LED current when the current set value is fixed or when the current suppression circuit 73 is not present. From the figure, even if the on-duty ratio on the horizontal axis changes, the LED current peak value (level I in FIG. 95) does not change, and the average value (level II in FIG. 95) has a small on-duty ratio. It has fallen so much. That is, the smaller the on-duty ratio, the darker the illumination light. That is, the brightness is reduced due to visible light communication.

  95 and 96, in the illumination light communication apparatus according to the fourteenth embodiment as shown in FIG. 94A, the LED current peak value (that is, the current set value) increases as the on-duty ratio decreases. As a result, the average value of the LED current can be made constant regardless of whether the on-duty ratio is small or large, and the illumination light is controlled regardless of whether the switch SW is on or off and regardless of the on-duty ratio. The brightness can be kept constant.

  97A is a diagram showing a third simulation result using the current suppression circuit 1 in FIG. 2 instead of the current suppression circuit 73 in FIG. 93A. FIG. 97A shows the optimum current setting value of the current suppression circuit 73 for each on-duty ratio. F As shown in the figure, by changing the current setting value for each on-duty ratio, the average value of the LED current can be made constant to a value when it is not intermittent. That is, a decrease in brightness due to the switch SW is suppressed. In addition, as shown in FIG. 97B, the loss of the current suppression circuit 73 (that is, the power consumption of the current suppression circuit 73 itself) can be maintained at a low value.

  FIG. 98 is a diagram showing LED current, output voltage, SW voltage, and current suppression circuit voltage in FIG. 93A. FIG. 8F is an explanatory diagram for calculating the optimum current setting value of the current suppression circuit 73 in accordance with the on-duty ratio of the modulation signal from the signal generation circuit SG. The power supply circuit 52b which is a premise of the illumination light communication apparatus of the fourteenth embodiment is a constant voltage power supply and has a constant voltage feedback function as already described. As a typical example, a constant voltage feedback circuit 67a using an error amplifier as shown in FIG. 93A is provided. Usually, a phase compensation circuit for ensuring the stability of the feedback system is added. In such a phase compensation circuit, a compensation circuit including an integration element is used in order to adjust the gain and phase in the round transfer function, which is known as PI control or PID control. In other words, such a phase compensation circuit can be said to be a means for controlling the average value of the voltage applied to the current suppression circuit 73 to be constant.

  Based on this point, when looking at the various waveforms shown in FIG. 98, first, the LED current that flows when the switch SW is on is maintained in a rectangular wave shape by the current suppression circuit 73. Since the load current is cut off while the switch SW is off, the output voltage rises and this voltage is applied to the switch SW. Next, when the switch SW is on, the LED current flows, so the output voltage drops and this voltage is applied to the load circuit 53 and the current suppression circuit 73 which are light sources. Since the current of the load circuit 53 is a rectangular wave, the variation ΔVo of the output voltage is applied to the current suppression circuit 73, and the average value Vave of this voltage waveform is constant by the constant voltage feedback circuit 67a (in the example shown in FIG. 98, about 1V). That is, if the reference voltage source 72 of the constant voltage feedback circuit 67a is appropriately set in consideration of the current value of the load circuit 53, the capacitance value of the smoothing capacitor 65, the variable range of the on-duty ratio, and the like, the LED current waveform is changed. While maintaining the rectangular wave, the loss of the current suppression circuit 73 can be generally suppressed to a desired range. Also, by changing the peak cut value Iop of the LED current to the value represented by the equation (1) according to the on-duty ratio, the average value of the LED current is made constant regardless of the value of the on-duty ratio. Value can be maintained.

  Optimum current setting value = Iop = 100 × Iave / ONd (%) (1)

  Here, Iop is a peak cut value of the LED current, that is, an optimum current setting value of the current suppression circuit 73. Iave is an average value of the LED current when not intermittently. ONd is the ON duty ratio (%) of the switch SW.

  The relationship between the partial on-duty ratio of the communication signal and the optimum current setting value is as shown in FIG. 29B. FIG. 29B shows the result of obtaining the optimum current setting value for each on-duty ratio using the equation (1). In the figure, the on-duty ratio ONd and the current set value are in an inversely proportional relationship.

  As described above, according to the illumination light communication apparatus in the fourteenth embodiment, it is possible to suppress overshoot of the LED current, reduce malfunction of the reception apparatus, and illumination light when the illumination light is not modulated The brightness of the illumination light and the brightness of the illumination light when the illumination light is modulated can be made substantially equal to each other in appearance.

(Embodiment 15)
The illumination light communication apparatus according to the fifteenth embodiment will be described with reference to FIGS. 99A to 99C.

  FIG. 99A is a circuit diagram showing a configuration of the illumination light communication apparatus in the fifteenth embodiment. This figure is different from FIG. 93A in that a first current suppression circuit 73a and a second current suppression circuit 73b are provided instead of the current suppression circuit 73. Further, the switch SW, the signal generation circuit SG, and the second current suppression circuit 73b are different from each other in that the communication module 10 is detachable at the first to third terminals T1 to T3. Hereinafter, different points will be mainly described.

  The first current suppression circuit 73a is connected in series with the load circuit 53, which is a light source, and the switch SW, and suppresses a current flowing through itself so as not to exceed a first current set value corresponding to the first reference value. Specifically, the first current suppression circuit 73a includes a transistor 74 that is a MOSFET, a resistor 75 connected to the source, an error amplifier 77, and a reference source 76. The reference source 76 outputs the first reference value to the plus input terminal of the error amplifier 77. The first reference value defines a first current setting value in the current flowing through the load circuit 53 that is a light source. For example, the first reference value is proportional to the first current set value. The reference source 76 outputs the first reference value as a fixed value.

  The second current suppression circuit 73b is connected in parallel with the first current suppression circuit 73a, and suppresses the current flowing through itself so as not to exceed the second current set value corresponding to the second reference value.

  FIG. 99C is a circuit diagram showing a specific configuration example of communication module 10 and second current suppression circuit 73b in the fifteenth embodiment. The second current suppression circuit 73b in the same figure has the same configuration as the current suppression circuit 73 shown in FIG. 93A and operates in the same manner. The output of the reference source 76 in the figure is called a second reference value. The upper limit of the current flowing through the second current suppression circuit 73b according to the second reference value is referred to as a second current set value. Moreover, it can be said that the communication module 10 which can be attached or detached by the 1st-3rd terminal part is a structure suitable for adding an illumination light communication function in the form retrofitted to the existing LED lighting fixture. FIG. 99B is a circuit diagram showing a configuration of an illumination light communication apparatus to which communication module 10 in Embodiment 15 is not added. When the illumination light communication device (ordinary illumination device) does not include the communication module 10 as shown in the figure, the short line S10 that connects the first and second terminals T1 and T2 may be provided.

  99A and 99C will be described using simulation results. FIG. 100 is a diagram showing simulation results for the circuit examples of FIGS. 99A and 99C. The main setting conditions for the simulation are a load when the capacitance value of the smoothing capacitor 65 is 20 uF, the modulation signal frequency from the signal generation circuit SG is 2.4 kHz, the operating frequency of the DC-DC converter 64 is 65 kHz, and the switch SW is not intermittently connected. The average value of current (LED current) is set to 240 mA.

  As shown in FIG. 100, the first current set value based on the first reference value of the reference source 76a of the first current suppressing circuit 73a is set to a current value (240 mA) when the switch element SW is not intermittently connected (in FIG. 100). Existing current value). The second current set value based on the second reference value of the second current suppression circuit 73b is increased as the “additional current value” in the figure as the on-duty ratio of the switch SW decreases. The ideal set value in the figure is the sum of the first current set value and the second current set value. As a result, the average current value of the LED load can be made constant regardless of the on-duty ratio.

  Next, FIG. 101 calculates the optimum second current set value of the added second current suppression circuit 73b according to the on-duty ratio of the modulation signal from the signal generation circuit SG in the fifteenth embodiment. It is explanatory drawing for. Please also refer to the explanatory diagram showing the waveform of the intermittent LED current shown in FIG. 29A. As already described with reference to FIG. 98, the first and second current setting values of the first current suppression circuit 73a and the second current suppression circuit 73b each set the peak cut value (Iop) of the LED current. In the fifteenth embodiment, the first set current value is set as a fixed value to the LED current 240 mA when the first current suppression circuit 73a has not been intermittently connected. It is optimal to set the 2 current set value (additional current set value) to a value represented by the following equation (2).

  Iop2 = Iave × [100 / ONd (%) − 1] (2)

  Here, Iop2 is the current peak cut value of the second current suppression circuit 73b, that is, the optimum additional current setting value. Iave is an average value of the LED current when not intermittently. ONd is the ON duty ratio (%) of the switch SW.

  FIG. 101 is a diagram showing a current setting value according to the on-duty ratio. This figure shows the result of obtaining the optimum current set value for each on-duty ratio using the equation (2). The total current set value in the figure shows the sum of the first current set value and the second current set value. The additional current set value indicates the second current set value. In this example, the first current set value is a fixed value of 240 mA, and the second current set value is a variable value of 0 to 240 mA.

  As described above, the first current suppressing circuit 73a and the current suppressing circuit 73b suppress the current flowing through the switch SW so as not to exceed the sum of the first current set value and the second current set value. By fixing the first current set value and making the second current set value variable, the system operation system can be improved, and the suppression of the decrease in the brightness of the illumination light due to the on / off of the switch SW is more appropriate. Can be improved. Furthermore, the overshoot generated in the LED current can be reduced, and malfunction of the receiving device can be reduced. Further, by making the second current suppression circuit 73b detachable as a part of the communication module 10, it can be easily added to an existing lighting device.

  99A and 99C does not include the switch SW and the signal generation circuit SG, and may include only the circuit portion of the current suppression circuit 73b and the second and third terminals T2 and T3. In this case, in FIG. 99B, a switch SW and a signal generation circuit SG are provided instead of the short line S10, and the switch SW is connected between the first and second terminals.

(Embodiment 16)
An illumination light communication apparatus according to the sixteenth embodiment will be described with reference to FIG. Here, the circuit portion symbols are the same as those in FIG. 93A, and the added / changed circuit portion will be mainly described. In the sixteenth embodiment, a constant current feedback circuit 167 is provided in place of the control circuit 6 in FIG. 93A, so that the value of the reference source can be varied according to the on-duty ratio described in the fourteenth embodiment. The configuration will be described.

  FIG. 102 is a circuit diagram showing a configuration of the illumination light communication apparatus in the sixteenth embodiment. Compared to the fourteenth embodiment (FIG. 93A), FIG. 102 shows a new resistor 66 for detecting LED current, a constant current feedback circuit, instead of the control circuit 6 that changes the reference source 76 of the current suppression circuit 73. 167 and a level shifter 78 are added to constitute a feedback system. The constant current feedback circuit 167 is connected to the negative input terminal of the error amplifier 169 via the input resistor 168, and the constant voltage source 72c is connected to the positive terminal of the error amplifier 169. A gain adjusting resistor 71r and a phase compensating capacitor 170 are connected between the output terminal of the error amplifier 169 and the negative input terminal of the error amplifier 169.

  The constant current feedback circuit 167 controls the voltage at the positive input terminal of the error amplifier 77 of the current suppression circuit 73 so that the voltage drop of the resistor 66 for detecting the LED current matches the value of the constant voltage source 72c. The level shifter 78 is required when the operation reference point of the current suppression circuit 73 and the operation reference point of the constant current feedback circuit 167 are different.

  104 to 106 show simulation results for verifying the operation of the sixteenth embodiment (FIG. 102). The main setting conditions for the simulation are a load when the capacitance value of the smoothing capacitor 65 is 20 uF, the modulation signal frequency from the signal generation circuit SG is 2.4 kHz, the operating frequency of the DC-DC converter 64 is 65 kHz, and the switch SW is not intermittently connected. The average value of current (LED current) is set to 240 mA.

  FIG. 104 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 104 shows the average value, peak value (peak cut value), and fluctuation value (change in peak value) of the LED current with the horizontal axis being the on-duty ratio, and the LED current does not depend on the on-duty ratio. The average value is kept constant. Moreover, the fluctuation range is small, and it can be seen that the LED current maintains a rectangular wave.

  FIG. 105 is a diagram showing a second simulation result for the circuit example of FIG. FIG. 105 shows the fluctuation range in terms of ripple rate, and some fluctuations are observed, but these include high-frequency ripples.

  FIG. 106 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 106 shows the circuit loss generated in the current suppression circuit 73 with the horizontal axis as the on-duty ratio. It can be seen that the loss is kept low regardless of the on-duty ratio.

  According to the illumination light communication apparatus of the sixteenth embodiment shown in FIG. 102, when performing optical communication with the switch SW intermittently, the average value of the LED current is kept constant regardless of the on-duty ratio of the switch SW. Since it can be maintained, it is possible to prevent a change in brightness or flicker as illumination during communication. Further, since the current suppression circuit 73 is connected, the LED current waveform is maintained as a rectangular wave, and an overshoot that causes a malfunction on the reception side is also suppressed. Furthermore, since the voltage applied to the current suppression circuit 73 is controlled to a desired average value by the constant voltage feedback circuit 67a, the circuit loss in the current suppression circuit 73 can be reduced.

(Embodiment 17)
An illumination light communication apparatus according to the seventeenth embodiment will be described with reference to FIG. Here, this figure is combined with the symbol of the circuit portion common to FIG. 99, and the explanation will focus on the added / changed circuit portion. In the seventeenth embodiment, a specific configuration described in the fifteenth embodiment for changing the value of the second reference value according to the on-duty ratio will be described.

  103 shows a method of changing the reference source 76 of the second current suppression circuit 73b in the fifteenth embodiment (FIGS. 99A and 99C), a resistor 66 for newly detecting the LED current, and a constant current feedback circuit 167. A level shifter 78 is added to form a feedback system. The constant current feedback circuit 167 is connected to the negative input terminal of the error amplifier 169 via the input resistor 168, and the constant voltage source 72c is connected to the positive terminal of the error amplifier 169. A gain adjusting resistor 71r and a phase compensating capacitor 170 are connected between the output terminal of the error amplifier 169 and the negative input terminal of the error amplifier 169.

  The constant current feedback circuit 167 controls the voltage at the positive input terminal of the error amplifier 77 of the second current suppression circuit 73b so that the voltage drop of the LED current detection resistor 66 matches the value of the constant voltage source 72c. The level shifter 78 is required when the operation reference point of the second current suppression circuit 73b is different from the operation reference point of the constant current feedback circuit 167.

  107 to 109 show simulation results for verifying the operation of the seventeenth embodiment (FIG. 103). The main setting conditions for the simulation are a load when the capacitance value of the smoothing capacitor 65 is 20 uF, the modulation signal frequency from the signal generation circuit SG is 2.4 kHz, the operating frequency of the DC-DC converter 64 is 65 kHz, and the switch SW is not intermittently connected. The average value of current (LED current) is set to 240 mA.

  FIG. 107 is a diagram showing a first simulation result for the circuit example of FIG. 103. FIG. 107 shows the average value, peak value (peak cut value), and fluctuation value (change in peak value) of the LED current with the horizontal axis being the on-duty ratio, and the LED current does not depend on the on-duty ratio. The average value is kept constant. Moreover, the fluctuation range is small, and it can be seen that the LED current maintains a rectangular wave.

  FIG. 108 is a diagram illustrating a second simulation result for the circuit example of FIG. 103. FIG. 108 shows the fluctuation range in terms of a ripple rate, and some fluctuations are observed, but these include high-frequency ripples.

  FIG. 109 is a diagram illustrating a third simulation result for the circuit example of FIG. 103. FIG. 109 shows circuit loss that occurs in the first current suppression circuit 73a and the second current suppression circuit 73b, with the horizontal axis being the on-duty ratio. It can be seen that the loss is kept low regardless of the on-duty ratio.

  According to the seventeenth embodiment shown in FIG. 103, when optical communication is performed with the switch SW intermittently, the average value of the LED current can be kept constant regardless of the on-duty ratio of the switch SW. As a result, it is possible to prevent changes in brightness and flickering during communication. In addition, since the first current suppression circuit 73a and the second current suppression circuit 73b are connected, the LED current waveform maintains a rectangular wave, and an overshoot that causes a malfunction on the reception side is also suppressed. Furthermore, since the voltage applied to the first current suppression circuit 73a and the second current suppression circuit 73b is controlled to a desired average value by the constant voltage feedback circuit 67a, the first current suppression circuit 73a and the second current suppression circuit are controlled. It is also possible to reduce circuit loss in the circuit 73b.

  In addition, if the second current suppression circuit 73b, the constant current feedback circuit 167, the level shifter 78, and the switch SW in FIG. 103 are configured as a communication module that is retrofitted to an existing LED lighting apparatus, an illumination light communication function can be easily added. Has features that can be. The communication module may be a circuit portion of the second current suppression circuit 73b, the constant current feedback circuit 167, and the level shifter 78 of FIG. 103 that does not include the switch SW.

(Embodiment 18)
Illumination light communication apparatuses according to the eighteenth embodiment are shown in FIGS. The basic main circuit configuration of these drawings is the same as that of FIGS. 93A and 99A, and the same symbols are added. 110 and 111 differ from FIGS. 93A and 99A in that a specific configuration example of the control circuit 6 and a specific configuration example of the signal generation circuit SG are described as block diagrams. Hereinafter, different points will be mainly described.

  110 and 111 are the same as control circuit 6 and signal generation circuit SG in FIG. 83, and have already been described.

  Here, FIG. 112A and FIG. 112B show circuit examples of the reference source 76 for switching the reference value or the second reference value.

  FIG. 112A is a circuit diagram showing a current suppression circuit including a first modification of reference source 76 in the eighteenth embodiment. The current suppression circuit 73 illustrated in FIG. 112A includes a transistor 2 that is a MOSFET, a resistor 3 connected to a source, a reference source 76, and a control circuit 6. The reference source 76 includes a constant voltage source 4a, voltage dividing resistors R1, R6, R7, and R8, and switch elements S01 to S03 for switching the voltage dividing ratio.

  The control circuit 6 calculates an appropriate reference voltage value according to the signal arrangement of the communication signals, or selects an appropriate reference voltage value from a correspondence table constructed in advance, and switches the switch elements S01 to S03. May be. As the number of resistors and switch elements in the voltage dividing circuit increases, the reference voltage can be switched more finely.

  FIG. 112B is a circuit diagram showing a current suppression circuit including a second modification of reference source 76 in the eighteenth embodiment. 112B includes a transistor 2 that is a MOSFET, a resistor 3 connected to a source, a reference source 76, and a control circuit 6. The reference source 76 includes a constant voltage source 4a, voltage dividing resistors R11, R12, R13, and R14, and switch elements S01 and S02 for switching the voltage dividing ratio.

  The positive potential side of the constant voltage source 4a is connected to the positive input terminal of the error amplifier 5 through the resistor R11. A series circuit of resistors R12, R13, and R14 is provided between the connection point and the negative potential side of the constant voltage source 4a, and switch elements S01 and S02 that short-circuit one or two of them are connected. Composed.

  Note that, as the number of resistors and changeover switches in the voltage dividing circuit in FIGS. 112A and 112B increases, the reference voltage can be finely switched.

  The operation example of the control circuit 6 shown in FIGS. 110 and 111 has already been described using the flowchart shown in FIG. 84A, the explanatory diagram of the shift register 6a shown in FIG. 84B, and the flowchart of the correction example shown in FIG. 84C. That's right.

  As described above, according to the eighteenth embodiment, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the switch SW is turned on is reduced, thereby receiving errors in the receiving apparatus. Can be reduced. In addition, a partial on-duty ratio is calculated using a shift register, and the reference value is determined according to the calculated partial on-duty ratio. Therefore, the reference value is more dynamically changed to an appropriate value. be able to.

  As described above, the illumination light communication apparatuses according to the fourteenth to eighteenth embodiments modulate the illumination light, the light source that emits illumination light, the switch SW that is connected in series with the light source and interrupts the current flowing through the light source. A signal generation circuit SG for generating a binary communication signal for controlling on and off of the switch SW, and the light source and the switch SW are connected in series and do not exceed a current set value corresponding to a reference value As described above, the current suppression circuit 73 that suppresses the current flowing through the light source, the DC-DC converter 64 that applies a DC voltage to the light source, the switch, and the current suppression circuit connected in series, and the current suppression circuit are applied. And a constant voltage feedback circuit 67a for controlling the DC power supply circuit so that the average value of the voltage is constant.

  According to this, even when 100% modulation optical communication is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. In addition, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the switch SW is turned on can be reduced, thereby reducing the reception error in the receiving apparatus.

  Here, the current suppression circuit 73 includes a reference source 76 that outputs the reference value, a transistor 74 that is connected in series with the light source and the switch SW, and suppresses a current flowing through the light source based on the reference value. , Measuring a partial on-duty ratio of the communication signal, and setting the reference value to a first value when the partial on-duty ratio is a first ratio; A control circuit 6 for setting the reference value to a second value smaller than the first value when the second ratio is larger than a ratio of 1, and the current setting value corresponding to the second value is You may make smaller than the electric current setting value corresponding to a 1st value.

  According to this, when the magnitude of the overshoot depends on the partial on-duty ratio, it is possible to appropriately suppress the overshoot.

  Here, the control circuit 6 may change the reference value so that the current set value is inversely proportional to the partial on-duty ratio.

  Here, the control circuit 6 may change the reference value so as to satisfy the following expression.

      I1 = (Iave / ONd) × 100

  Here, I1 is the current setting value, Iave is an average current flowing through the light source when the illumination light is not modulated by the switching of the switch, and ONd is a partial on-duty ratio ( The unit is%).

  According to this, the brightness of the illumination light when the overshoot is suppressed and the illumination light is not modulated is substantially equal to the brightness of the illumination light when the illumination light is modulated. Can be.

  Here, the control circuit 6 detects the magnitude of the current flowing through the light source, and the magnitude of the current detected by the detection section so as to keep the average value of the current flowing through the light source constant. A constant current feedback circuit 167 that performs feedback control to change the reference value according to the reference value may be provided.

  Moreover, the illumination light communication apparatus according to Embodiments 14 to 18 modulates the illumination light, a light source 53 that emits illumination light, a switch SW that is connected in series with the light source, and that interrupts current flowing through the light source, and the illumination light. Therefore, a signal generation circuit SG for generating a binary communication signal for controlling on and off of the switch, and connected in series with the light source and the switch, the first current set value corresponding to the first reference value is exceeded. The first current suppression circuit 73 that suppresses the current flowing through itself and the first current suppression circuit that is connected in parallel with the first current suppression circuit so as not to exceed the second current set value corresponding to the second reference value A second current suppressing circuit 73b for suppressing a current flowing through the power source, a DC-DC converter 64 for applying a DC voltage to the light source, the switch and the first current suppressing circuit connected in series, and an output of the DC power supply circuit. And a constant voltage feedback circuit 67a for controlling the DC power supply circuit so that the voltage is constant.

  According to this, even when 100% modulation optical communication is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. Moreover, the current flowing through the switch is suppressed by the first current suppression circuit and the second current suppression circuit so as not to exceed the sum of the first current set value and the second current set value. By fixing the first current set value and making the second current set value variable, the system operation system can be improved, the overshoot generated in the LED current can be reduced, and the malfunction of the receiver can be reduced. Can do.

  Here, the second current suppression circuit may change the second reference value so as to satisfy the following expression.

      I2 = (Iave / ONd) × 100

  Here, I2 is the second current setting value, Iave is an average current flowing through the light source when the illumination light is not modulated by the switching of the switch, and ONd is a partial on-duty of the communication signal. Ratio (unit:%).

  Here, the second current suppression circuit includes a detection unit that detects the magnitude of the current flowing through the light source, and the current detected by the detection unit so that an average value of the current flowing through the light source is constant. A constant current feedback circuit 167 that performs feedback control to change the reference value according to the magnitude may be provided.

  Here, the control circuit 6 has a shift register 6a that holds the first n (n is an integer of 2 or more) bit data of the communication signal while shifting, and data of a predetermined number of bits from the end of the shift register 6a. The moving average value is calculated as a partial on-duty ratio, the moving average value is corrected based on the bit pattern of the n-bit data held in the shift register, and the reference corresponding to the corrected value The value may be determined.

  Here, the second current suppression circuit includes a control circuit 6 having a shift register 6a that holds the first n (n is an integer of 2 or more) bit data of the communication signal while shifting, and the control circuit 6 includes: A moving average value is calculated as a partial on-duty ratio for data of a predetermined number of bits from the end of the shift register 6a, and the moving average is calculated based on a bit pattern of n-bit data held in the shift register. The value may be corrected, and a reference value corresponding to the corrected value may be determined.

  Here, in the correction of the moving average value, the control circuit 6 determines that the moving average value is 1 when the first bit from the end of the shift register is 1 and the second and subsequent bits are 0. Small coefficients may be raised to the same number as the number of consecutive zero bits.

  Here, in the correction of the moving average value, when the first bit from the first bit of the n-bit data is 1 and the second bit or the third bit is 1 in the correction of the moving average value, the control circuit A coefficient greater than 1 may be raised to the value by the same number as the number of consecutive 1 bits.

  Here, instead of calculating the moving average value as a partial on-duty ratio, the control circuit does not calculate the moving average value, but the average on-state of the communication signal subjected to N (N is an integer of 2 or more) value pulse position modulation. A duty ratio (1- (1 / N)) × 100 (%) may be used.

  Here, the communication signal may be N-value pulse position modulated, and the number of bits of the shift register and the number of bits of the moving average may be at least N bits.

  Here, the reference source includes a constant voltage source that generates a fixed voltage, a plurality of resistance elements that divide the constant voltage source, and one or more changeover switches connected in series or in parallel with the resistance elements. The control circuit may control on and off of the one or more changeover switches according to the corrected value.

  Here, the second current suppression circuit may be configured to be detachable from the illumination light communication device.

  The communication modules according to the fourteenth to eighteenth embodiments are the communication module 10 that modulates the illumination light that can be attached to and detached from the illumination device, the switch SW connected in series with the light source of the illumination device, and the illumination A signal generation circuit SG that generates a binary communication signal for controlling on and off of the switch to modulate light, and a current suppression that is connected in series with the light source and the switch and suppresses a current flowing through the light source. A circuit 73; and first, second and third terminals T1 to T3 for attaching to and detaching from the lighting device, wherein the first terminal T1 is on the switch side of the series circuit including the switch and the current suppressing circuit. The second terminal T2 is connected to a connection point between the switch and the current suppression circuit in the series circuit, and the third terminal T3 is connected to the front of the series circuit. It is connected to the other end of the current suppressing circuit side.

  According to this, the communication module can be added to an existing lighting fixture. In other words, the existing lighting fixture can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than the case of installing a new optical communication lighting fixture. Further, even when optical communication with 100% modulation is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. In addition, since the overshoot generated in the current flowing through the light source is reduced at the moment when the switch is turned on, the reception error in the receiving device can be reduced.

(Embodiment 19)
In general, when an attempt is made to realize visible light communication in an illumination device that performs dimming by PWM (pulse width modulation), color balance may be lost due to the mixture of PWM control and modulation for visible light communication. is there.

  In the nineteenth embodiment, an illumination light communication device that can prevent color balance from being lost will be described.

  An illumination light communication apparatus according to an aspect of the present embodiment includes a plurality of illumination units that emit light of different colors, a dimming control unit that controls a dimming level of each of the plurality of illumination units, and the plurality A modulation control unit that superimposes a signal on the light emitted by the plurality of illumination units by modulation that temporally switches between light emission and non-light emission of each of the illumination units, and each of the plurality of illumination units emits the light A light source; a switch connected in series with the light source; and a power supply circuit for supplying power to the light source; and a dimming control unit for each of the plurality of illumination units. On the other hand, by controlling the power supply circuit, when the dimming level is higher than a reference level, amplitude dimming is performed to control the intensity of light emitted from the illumination unit, and the dimming level is higher than the reference level. Low and the modulation is performed When the modulation unit performs the modulation, the modulation control unit performs the PWM dimming that controls the on-duty, which is the ratio of the light emission time in the light emission and non-light emission repetition periods of the illumination unit. For each, when the dimming level is higher than the reference level, modulation is performed by controlling the switch, and when the dimming level is lower than the reference level, (1) the PWM dimming by the power supply circuit (2) By controlling the switch, the modulation and the PWM dimming are performed at the same time, and the modulation is performed so that the light emission start timing is synchronized with the other illumination units. Take control.

  In addition, the receiving device according to one aspect of the present embodiment includes: a light receiving unit that receives a plurality of lights of different colors, on which signals are superimposed by modulation that temporally switches between light emission and non-light emission; When the ratio of the brightness of each of the plurality of lights received by the light receiving unit to the brightness of each other is greater than a predetermined value, the signals are demodulated using the plurality of lights, (2) When one of the plurality of ratios is smaller than the predetermined value, the signal is demodulated using light other than light having the ratio smaller than the predetermined value among the plurality of lights. And a demodulator.

  According to the illumination light communication apparatus and the receiving apparatus according to the present embodiment, it is possible to suppress the color balance from being lost.

[19.1 Configuration of Illumination Optical Communication Device]
First, the configuration of the illumination light communication apparatus according to the nineteenth embodiment will be described. FIG. 113 is a block diagram showing a configuration of illumination light communication apparatus 100 according to the nineteenth embodiment.

  The illumination light communication apparatus 100 illustrated in FIG. 113 functions as a visible light communication transmitter that transmits a signal by modulating the intensity of illumination light. The illumination light communication apparatus 100 is, for example, an RGB projector that projects color light. The illumination light communication apparatus 100 includes illumination units 201R, 201G, and 201B, a dimming control unit 202, and a modulation control unit 203.

  The illumination unit 201R emits red light, the illumination unit 201G emits green light, and the illumination unit 201B emits blue light.

  The dimming control unit 202 controls the dimming level (brightness) of each of the illumination units 201R, 201G, and 201B. Specifically, the dimming control unit 202 controls dimming signals S1R, S2R, and the like for controlling the dimming levels of the illumination units 201R, 201G, and 201B according to the hue and brightness of the light to be projected. S3R is generated.

  The modulation control unit 203 superimposes a communication signal (visible light signal) on light emitted from the illumination units 201R, 201G, and 201B by modulation that temporally switches light emission and non-emission of the illumination units 201R, 201G, and 201B. Specifically, the modulation control unit 203 generates binary modulation signals S2R, S2G, and S2B based on a communication signal transmitted by visible light communication. The modulation signal generation unit 123 may repeatedly generate the modulation signals S2R, S2G, and S2B indicating the ID unique to the illumination light communication apparatus 100, or may generate a modulation signal in accordance with a communication signal input from an external apparatus. S2R, S2G and S2B may be generated.

  In the following, modulation for superimposing a visible light signal (communication signal) on illumination light is simply referred to as “modulation”, and modulation using PWM for dimming is referred to as “PWM dimming”. Details of PWM dimming will be described later.

  In addition, here, an example in which the illumination light communication device 100 includes three RGB color illumination units will be described, but the color emitted by the illumination unit and the number of illumination units are not limited thereto, and for example, the illumination light communication device 100 May have illumination parts of four or more colors.

[19.2 Configuration of Lighting Unit]
Hereinafter, the configuration of the illumination units 201R, 201G, and 201B will be described. Since the configurations of the illumination units 201R, 201G, and 201B are the same, only the configuration of the illumination unit 201R will be described below.

  FIG. 114 is a diagram illustrating a configuration of the illumination unit 201R. As shown in FIG. 114, the illumination unit 201R includes a light source 101, a power supply circuit 102, a dimming signal receiving unit 104, a modulation switch 121, a current suppression circuit 122, a control power supply 126, and a drive circuit 128. .

  The light source 101 includes one or more light emitting elements (for example, LEDs) and emits illumination light.

  The dimming signal receiving unit 104 receives the dimming signal S1R generated by the dimming control unit 202.

  The power supply circuit 102 supplies power to the light source 101. The power supply circuit 102 includes a power supply 111, a DC-DC converter 112, a capacitor 113, a detection resistor 114, and a constant current feedback circuit 115.

  The power supply 111 outputs a DC voltage to the DC-DC converter 112. The DC-DC converter 112 converts the DC voltage supplied from the power supply 111 into a desired voltage V0 and outputs the voltage V0 to the light source 101. The capacitor 113 is connected between the output terminals of the DC-DC converter 112.

  The detection resistor 114 is used for detecting a current flowing through the light source 101. The constant current feedback circuit 115 controls the output voltage V0 of the DC-DC converter 112 so that the current flowing through the detection resistor 114, that is, the current flowing through the light source 101 is constant.

  Further, the DC-DC converter 112 controls the output voltage V0 based on the dimming signal S1R received by the dimming signal receiving unit 104. Specifically, the DC-DC converter 112 controls amplitude dimming for controlling the intensity of light emitted from the light source 101 and on-duty, which is a ratio of the light emission time in the light emission and non-light emission repetition cycle of the light source 101. PWM dimming is performed.

  The control power supply 126 generates a power supply voltage for the current suppression circuit 122 and the like from the voltage V0 output from the power supply circuit 102, and supplies the generated power supply voltage to the current suppression circuit 122 and the like. The control power supply 126 includes a PWM detection circuit 127a that detects that PWM dimming is performed based on the voltage V0.

  The modulation switch 121 is connected in series with the light source 101, and interrupts the current supplied from the power supply circuit 102 to the light source 101. The modulation switch 121 is, for example, a transistor (for example, a MOSFET).

  The drive circuit 128 generates a signal to be supplied to the control terminal (gate) of the modulation switch 121 based on the modulation signal S2R generated by the modulation control unit 203.

  The current suppression circuit 122 is connected in series with the light source 101 and the modulation switch 121 and suppresses the current flowing through the light source 101. Specifically, the current suppression circuit 122 suppresses (clips) the current flowing through the light source 101 so as not to exceed the current set value Is.

  The current suppression circuit 122 includes a transistor 131 that is a MOSFET, a current setting circuit 132, an amplifier 133, and a current detection circuit 134 that is a resistor connected to the source of the transistor 131.

  The current setting circuit 132 outputs a reference value to the plus input terminal of the amplifier 133. The reference value defines the upper limit (current setting value Is) of the current flowing through the light source 101. For example, the reference value is proportional to the current setting value. The current setting circuit 132 outputs a variable reference value. Note that the current setting circuit 132 may output the reference value as a fixed value.

  The transistor 131 is connected in series to the light source 101 and the modulation switch 121, and suppresses (clips) the current flowing through the light source 101 based on a reference value.

  The current detection circuit 134 is a source resistance for detecting the magnitude of the current flowing through the light source 101. The terminal on the transistor 131 side of the current detection circuit 134 is connected to the negative input terminal of the amplifier 133.

  The positive input terminal of the amplifier 133 is connected to the current setting circuit 132, and the negative input terminal of the amplifier 133 is connected to the source terminal of the transistor 131. The amplifier 133 amplifies the difference between the reference value output from the current setting circuit 132 and the current value detected by the current detection circuit 134, and outputs the amplified signal to the gate of the transistor 131.

  Note that the circuit configuration illustrated in FIG. 114 is an example, and the illumination unit 201R does not have to include all the components illustrated in FIG. For example, the illumination unit 201R may not include at least one of the current suppression circuit 122 and the control power supply 126.

  The configuration of the power supply circuit 102 is also an example, and the present invention is not limited to this configuration. For example, the power supply circuit 102 may not include the detection resistor 114 and the constant current feedback circuit 115. Further, the DC-DC converter 112 may perform constant current control. For example, the DC-DC converter 112 may perform switching current threshold control. Alternatively, the power supply circuit 102 may perform constant voltage control instead of constant current control. For example, the power supply circuit 102 may include a constant voltage feedback circuit instead of the detection resistor 114 and the constant current feedback circuit 115, or the DC-DC converter 112 may perform constant voltage control.

  The configuration of the current suppression circuit 122 is also an example, and the configuration is not limited to this as long as the current flowing through the light source 101 can be suppressed (clipped).

[19.3 Modulation operation]
Hereinafter, the modulation operation by the illumination light communication apparatus 100 will be described. 115 is a diagram for explaining the modulation operation by the illumination light communication apparatus 100. FIG. As shown in FIG. 115, the modulation switch 121 is turned on / off according to the modulation signal S2R. The modulation method used here conforms to, for example, the 1-4PPM transmission method defined in JEITA-CP1223. Specifically, 2-bit data is converted into a 4-slot pulse. At all times, three of these four slots are high level (on) and one slot is low level (off).

  In the example of FIG. 115, the current set value Is is constant.

  Here, when the modulation for visible light communication is performed, immediately after the modulation switch 121 is turned on, the LED current that is the current flowing through the light source 101 increases instantaneously as shown by the dotted line in FIG. A shoot occurs. Due to the occurrence of this overshoot, there is a problem that a signal cannot be received correctly in the visible light receiver.

  On the other hand, in illumination light communication apparatus 100 according to Embodiment 19, by providing current suppression circuit 122, the maximum value of LED current is limited to current set value Is. Thereby, the occurrence of overshoot is suppressed as shown in FIG. Thereby, the reception error in visible light communication can be reduced.

  Note that the constant current feedback circuit 115 shown in FIG. 114 also has a function of keeping the LED current constant, but the constant current control by the constant current feedback circuit 115 is a control with a relatively large time constant. That is, this constant current control is a control that keeps the average current constant for a predetermined period, and it is not possible to suppress the instantaneous overshoot as shown in FIG.

  Further, in the nineteenth embodiment, as shown in FIG. 114, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order between the power supply terminal and the GND terminal of the power supply circuit 102. On the other hand, as a connection form of the light source 101, the modulation switch 121, and the current suppression circuit 122, it is conceivable that the light source 101, the current suppression circuit 122, and the modulation switch 121 are connected in this order.

  However, in such a connection form, since the current suppression circuit 122 is not connected to the GND terminal of the power supply circuit 102, there is a problem that the operation becomes unstable. Specifically, when the modulation switch 121 is in the OFF state, the GND of the current suppression circuit 122 is in a floating state, so that the potential fluctuation of the GND increases. On the other hand, in the nineteenth embodiment, by using the connection form shown in FIG. 114, the current suppression circuit 122 is always connected to the GND terminal, so that stable operation can be improved regardless of the state of the modulation switch 121.

  In the above description, a 100% modulation method that completely cuts off the LED current in the off period is used as the modulation method. However, a method in which the LED current is lower than the on period in the off period may be used.

  In FIG. 114, the example in which the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order is described. However, the order of the serial connection of the light source 101, the modulation switch 121, and the current suppression circuit 122 is as follows. Not limited to.

[19.4 Dimming operation]
Hereinafter, the dimming operation by the illumination light communication apparatus 100 will be described. FIG. 116 is a diagram for explaining the dimming operation by the illumination light communication apparatus 100. FIG.

  As shown in FIG. 116, when the dimming level is higher than the reference level (the dimming level 5 to 3 in FIG. 116), the dimming control unit 202 controls the amplitude for controlling the intensity of light emitted from the lighting unit 201R. Perform dimming. Specifically, the current value of the LED current flowing through the light source 101 is controlled by controlling the voltage or current output from the power supply circuit 102 in accordance with the dimming signal S1R. More specifically, the LED current is controlled to be smaller as the dimming level is lower.

  In addition, the dimming control unit 202 is the ratio of the light emission time in the repetition cycle of light emission and non-light emission of the illumination unit 201R when the light control level is lower than the reference level (light control levels 5 to 3 in FIG. 116). PWM dimming that controls on-duty is performed. Specifically, the on-duty of the voltage or current output from the power supply circuit 102 is controlled in accordance with the dimming signal S1R. More specifically, the on-duty is controlled to be smaller as the dimming level is lower.

[19.5 Issues]
Here, when the modulation operation and the dimming operation are simply combined, the following problems occur when the modulation operation and the dimming operation are not considered with each other. As shown in FIG. 117, when PWM dimming and modulation are performed simultaneously, the switches are individually turned off by each control, so that the average luminance decreases. As a result, as shown in FIG. 117, when only one color (red light in FIG. 117) is subjected to PWM dimming, there is a problem that the hue is shifted. Further, in the case of detecting the rising edge in the receiving apparatus, since the rising edge of red light is different from the rising edge of other colors in FIG. 117, the red light is detected as noise, and there is a problem that reception accuracy is lowered. .

[19.6 Overall operation]
FIG. 118 is a flowchart of the operation of the illumination light communication apparatus 100. The processing shown in FIG. 118 is sequentially performed for each color. Further, it is repeated when the light control level is changed or at a predetermined time interval.

  When modulation is not performed (No in S101), the dimming control unit 202 performs normal dimming control as shown in FIG. Specifically, the dimming control unit 202 performs normal amplitude dimming (S103) when PMW modulation is not performed, that is, when the dimming level is higher than the reference level (No in S102), and performs PMW modulation. When performing, that is, when the dimming level is lower than the reference level (Yes in S102), normal PWM dimming is performed (S104).

  On the other hand, when modulation is performed and PWM dimming is not performed (Yes in S101 and No in S105), the dimming control unit 202 performs amplitude dimming, and the modulation control unit 203 is as illustrated in FIG. Normal modulation is performed (S106). In this case, the modulated signals S2R, S2G, and S2B supplied to the illumination units 201R, 201G, and 201B are the same signal, and the light emission and non-light emission of the illumination units 201R, 201G, and 201B are switched at the same timing. .

  In addition, the dimming control unit 202 may use the same amplitude dimming method for the case where the modulation is performed or not, or may use a different method. For example, the dimming control unit 202 may perform amplitude dimming so that the average luminance (the average value of the LED current) is the same between when the modulation is performed and when the modulation is not performed. Specifically, when 4PPM is used, the luminance value decreases to 75%. Therefore, when modulation is performed, the luminance value (LED current) may be increased so as to offset this decrease. In other words, when the specified dimming level is the same, the current value of the LED current when the modulation is performed (current value in the ON section) may be higher than the current value of the LED current when the modulation is not performed.

  On the other hand, when modulation is performed and PWM dimming is performed (Yes in S101 and Yes in S105), the illumination light communication apparatus 100 determines that the dimming level of the target color is the dimming level of all other colors. It is determined whether it is sufficiently lower (S107). Specifically, the illumination light communication apparatus 100 calculates the ratio of the dimming level of the target color (for example, red) to each of the dimming levels (green and blue) of the other colors. The illumination light communication apparatus 100 determines that the dimming level of the target color is sufficiently lower than the dimming levels of all other colors when all the calculated ratios are lower than a predetermined value. The illumination light communication apparatus 100 calculates the difference between the light control level (for example, red) of the target color and each of the light control levels (green and blue) of the other colors, and all the calculated differences are determined in advance. If it is greater than the given value, it may be determined that the dimming level of the target color is sufficiently lower than the dimming levels of all other colors.

  When the above condition is not satisfied, that is, when at least one of the calculated ratios is higher than a predetermined value (No in S107), the dimming control unit 202 does not perform PWM dimming, and the modulation control unit 203 (S108). Details of this process will be described later.

  When the above condition is satisfied, that is, when all of the calculated ratios are lower than a predetermined value (Yes in S107), the modulation control unit 203 does not perform modulation, and the dimming control unit 202 sets the modulation on-duty. Considering PWM dimming is performed (S109). Details of this process will be described later.

[19.7 First Operation Example]
Hereinafter, details of the first operation example (S108 in FIG. 118) in which the dimming control unit 202 does not perform PWM dimming and the modulation control unit 203 performs modulation in consideration of PWM will be described. FIG. 119 is a diagram for explaining the first operation example.

  The example shown in FIG. 119 is an example where only the light control level of the illumination unit 201R is lower than the reference level. The relative intensity (R) of red light is 0.1, the relative intensity (G) of green light is 1.0, and the relative intensity (B) of blue light is 0.2. Here, the relative intensity is the ratio of the signal intensity of each signal to the highest signal intensity when the highest signal intensity among the signal intensities of a plurality of colors is 1.0.

  As shown in FIG. 119, the modulation control unit 203 controls the illumination unit 201R so that the light emission start timing of the illumination unit 201R is the same as the light emission start timing of the illumination units 201G and 201B. In other words, the modulation control unit 203 is a case where modulation is performed, and when the dimming level is lower than the reference level, the modulation (S106 in FIG. 118) and the light emission start timing when the dimming level is higher than the reference level. The illumination unit 201R is controlled to be the same.

  Further, the modulation control unit 203 sets an on-duty considering PWM dimming. Specifically, the on-duty when the modulation is performed and the dimming level is higher than the reference level (S106 in FIG. 118), and the PWM performed when the modulation is not performed and the dimming level is lower than the reference level. Dimming is performed so that the on-duty is equal to the product of the on-duty when dimming is performed (S104 in FIG. 118). For example, when modulation by 4PPM is performed, the on-duty when modulation is performed is 75%. Therefore, when the on-duty when the PWM dimming is performed is 50%, the modulation control unit 203 performs modulation so that the on-duty is 32.25%.

  Here, when the on-duty is equal to or greater than a predetermined threshold (for example, 75%), there is a possibility that the receiving apparatus cannot receive a signal correctly because the off section (dark section) becomes too small. Therefore, in the nineteenth embodiment, control is performed so that the on-duty does not exceed a predetermined threshold. That is, in such a case, adjustment is performed by amplitude dimming instead of changing the on-duty.

  As described above, the illumination light communication apparatus 100 according to Embodiment 19 includes a plurality of illumination units 201R, 201G, and 201B that emit light of different colors, and a dimming level of each of the plurality of illumination units 201R, 201G, and 201B. A signal is superimposed on the light emitted from the plurality of illumination units 201R, 201G, and 201B by modulation that temporally switches between light emission and non-emission of each of the plurality of illumination units 201R, 201G, and 201B. A modulation control unit 203. Each of the plurality of illumination units 201R, 201G, and 201B includes a light source 101 that emits light, a modulation switch 121 that is connected in series with the light source 101, and that interrupts the current flowing through the light source 101, and a power supply circuit that supplies power to the light source 101 102. The dimming control unit 202 controls the power supply circuit 102 for each of the plurality of lighting units 201R, 201G, and 201B, so that when the dimming level is higher than the reference level, the intensity of light emitted from the lighting unit is increased. When the amplitude dimming to be controlled is performed (S103 and S106 in FIG. 118), and the dimming level is lower than the reference level and no modulation is performed, the ratio of the light emission time in the light emission and non-light emission repetition period of the illumination unit PWM dimming for controlling a certain on-duty is performed (S104 in FIG. 118). When performing modulation, the modulation control unit 203 controls the modulation switch 121 when the dimming level is higher than the reference level for each of the plurality of illumination units 201R, 201G, and 201B (S106 in FIG. 118). When modulation is performed and the dimming level is lower than the reference level, (1) PWM dimming by the power supply circuit 102 is not performed (the PWM modulation function is stopped), and (2) modulation is performed by controlling the modulation switch 121. First control (first operation) in which PWM dimming is performed at the same time, and modulation is performed so that the light emission start timing is synchronized with other illumination units (so that the rise of the modulation signal is synchronized with other illumination units) Example) is performed (S108 in FIG. 118).

  Thereby, the illumination light communication apparatus 100 can suppress the shift of the phase (rise timing, etc.) of the signals of each color when PWM dimming and modulation are performed at the same time, and with on-duty in consideration of PWM dimming. Modulation can be performed. Thereby, it can suppress that a color balance collapses.

  Furthermore, when PWM dimming and modulation are performed at the same time, all the control can be performed by the modulation control unit 203, so that the processing can be prevented from becoming complicated.

[19.8 Second Operation Example]
Hereinafter, the details of the second operation example (S109 in FIG. 118) in which the modulation control unit 203 performs no modulation and the dimming control unit 202 performs PWM dimming in consideration of the on-duty of the modulation will be described. FIG. 120 is a diagram for explaining the second operation example.

  The example shown in FIG. 120 is an example where only the light control level of the illumination unit 201R is lower than the reference level. The relative intensity (R) of red light is 0.1, the relative intensity (G) of green light is 1.0, and the relative intensity (B) of blue light is 1.0. That is, this is the case where the dimming level of red light is sufficiently lower than the dimming levels of all other colors.

As shown in FIG. 120, modulation is not performed and only PWM dimming is performed. Further, control in consideration of on-duty during modulation is performed as PWM dimming. Specifically, the dimming control unit 202 performs the on-duty when the modulation is performed and the dimming level is higher than the reference level (S106 in FIG. 118), the modulation is not performed, and the dimming level is the reference level. The PWM dimming is performed on the illuminating unit 201R so that the on-duty is equal to the product of the on-duty when the PWM dimming performed when it is lower (S104 in FIG. 118).

  For example, when modulation by 4PPM is performed, the on-duty when modulation is performed is 75%. Therefore, when the on-duty when the PWM dimming is performed is 50%, the dimming control unit 202 performs modulation so that the on-duty is 32.25%.

  Further, unlike the first operation example, in the second operation example, the rise of red light does not coincide with the rise of light of other colors.

  In this case, when modulation is performed using light of all colors in the reception device, red light is recognized as noise, and reception accuracy decreases. On the other hand, when the intensity of only one color is low, it is easy for the receiving device to determine a color with low intensity. Therefore, the receiving apparatus can demodulate the signal only from the signals of other colors without using the low-intensity color signal, so that it is possible to suppress a decrease in reception accuracy in the receiving apparatus.

  Further, as a technique for realizing the function of the illumination light communication apparatus 100, there is a technique for mounting a communication module for realizing an extension of the visible light communication function to an illumination apparatus that does not support visible light communication. For example, a lighting device that does not support visible light communication includes the light source 101 and the power supply circuit 102 illustrated in FIG. When the communication module is not mounted on the lighting device, the cathode of the light source 101 and the GND terminal of the power supply circuit 102 are short-circuited.

  In addition, the communication module includes a modulation switch 121, a current suppression circuit 122, a control power supply 126, a drive circuit 128, and the like shown in FIG. 114, a dimming control unit 202, a modulation control unit 203, and the like shown in FIG. Note that the lighting device has a normal light control function. Therefore, the communication module may include all the functions of the dimming control unit 202 and replace the dimming control function of the lighting device, or the function of the dimming control unit 202 extended in the nineteenth embodiment. May be included in the communication module, and the extended function may be added to the dimming control function of the lighting device. Specifically, the extended function includes a function of controlling so as not to perform PWM dimming in step S108, a function of controlling so as to perform PWM dimming in consideration of the on-duty of modulation in step S109, and the like. It is.

  Here, when such a retrofitted communication module is used, as shown in FIG. 114, a control power supply 126 that generates a power supply for the communication module from the output voltage V0 of the power supply circuit 102 is used. However, when PWM control is performed, the voltage V0 fluctuates, making it difficult for the control power supply 126 to stably generate a power supply for the communication module. Therefore, when PWM dimming is performed as in the second operation example, control is performed so that modulation is not performed, and when PWM dimming is performed, the operation of the communication module can be stopped. As a result, stable operation can be realized.

  For example, when the PWM detection circuit 127a shown in FIG. 114 detects PWM control of the power supply circuit 102, the function (modulation function) of the communication module can be stopped.

  In this way, when the modulation is performed, the dimming level is lower than the reference level, and the ratios of the dimming level of the target lighting unit to the dimming levels of the other lighting units are all predetermined. If the value is greater than the predetermined value (No in S107 in FIG. 118), the modulation control unit 203 performs first control (first operation example) on the target illumination unit (S108).

  When the modulation is performed and the dimming level is lower than the reference level and the ratio is smaller than a predetermined value (Yes in S107), the dimming control unit 202 controls the power supply circuit 102. Thus, the first on-duty when the modulation is performed and the dimming level is higher than the reference level, and the PWM dimming that is performed when the modulation is not performed and the dimming level is lower than the reference level are performed. In this case, PWM dimming is performed on the target illumination unit in which the product of the second on-duty and the on-duty are equal, and the modulation control unit 203 does not modulate the target illumination unit by the modulation switch 121. (Second operation example) is performed (S109).

  Thereby, the illumination light communication apparatus 100 can perform PWM control with on-duty in consideration of modulation when PWM dimming and modulation are performed simultaneously. Thereby, it can suppress that a color balance collapses.

  Furthermore, when PWM dimming and modulation are performed simultaneously, all the control can be performed by the dimming control unit 202, so that the processing can be prevented from becoming complicated.

  Furthermore, since the modulation operation can be stopped when the PWM control is performed, a stable operation can be realized, for example, when a retrofitted communication module is used.

[19.9 Modification]
In the above description, the illumination light communication apparatus 100 selectively performs the first operation example and the second operation example. However, the illumination light communication apparatus 100 includes the first operation example and the second operation example. You may have the function to perform only one of the operation examples. That is, the illumination light communication apparatus 100 performs the first operation example (S108) and the second operation example (S109) when modulation is performed and PWM dimming is performed (Yes in S105 of FIG. 118). One may always be done.

[19.10 Receiver]
Hereinafter, a receiving apparatus that receives a visible light signal transmitted by the illumination light communication apparatus 100 described above will be described. FIG. 121 is a block diagram of receiving apparatus 300 according to Embodiment 19. In FIG. As illustrated in FIG. 121, the reception device 300 includes a light receiving unit 301 and a demodulation unit 302.

  The light receiving unit 301 receives illumination light emitted from the illumination light communication apparatus 100. The light receiving unit 301 includes a red light receiving element that receives red light, a green light receiving element that receives green light, and a blue light receiving element that receives blue light, and a light reception signal based on light received by each light receiving element. S3R, S3G, and S3B are generated.

  The demodulator 302 demodulates the signal superimposed on the illumination light from the received light signals S3R, S3G, and S3B.

  FIG. 122 is a flowchart showing the operation of the receiving apparatus 300. First, the demodulator 302 determines whether the intensity of one of the received light signals S3R, S3G, and S3B is sufficiently lower than the intensity of the other two signals (S201). Specifically, the demodulation unit 302 calculates the ratio of the signal strength of the reception signal of the target color to each of the signal strengths of the reception signals of other colors. When all the calculated ratios are lower than a predetermined value, the demodulator 302 determines that the signal intensity of the target color is sufficiently lower than the signal intensity of all other colors. Note that the demodulator 302 calculates the difference between the signal intensity of the target color and each of the signal intensities of the other colors, and if all the calculated differences are larger than a predetermined value, the signal of the target color It may be determined that the intensity is sufficiently lower than the signal intensity of all other colors.

  When the above condition is not satisfied, that is, when at least one of the calculated ratios is higher than a predetermined value (No in S201), the demodulator 302 uses all of the received light signals S3R, S3G, and S3B to make visible The optical signal is demodulated (S202). That is, the demodulation unit 302 performs normal demodulation processing.

  On the other hand, when the above condition is satisfied, that is, when all of the calculated ratios are lower than a predetermined value (No in S201), the demodulation unit 302 has a sufficient signal strength among the received light signals S3R, S3G, and S3B. The visible light signal is demodulated using the received light signal other than the received light signal of the color determined to be low (S203). For example, when the signal intensity of the light reception signal S3R is low, the demodulation unit 302 demodulates the visible light signal from the light reception signals S3G and S3B.

  With the above operation, the receiving device 300 can stably demodulate the visible light signal from the illumination light emitted by the second operation in the illumination light communication device 100 described above.

  In the above description, the light receiving unit 301 includes a plurality of light receiving elements that receive each color. However, the light receiving unit 301 may include a single light receiving element that receives light including all colors. . In this case, the demodulation unit 302 may remove a signal component having an intensity lower than a threshold value from the signal obtained by the light receiving unit 301 and perform demodulation processing using the signal obtained thereby. Also in this case, similarly to the above, the demodulating unit 302 can perform the demodulation process using only the color signal having a high modulated signal strength without using the color signal having a low signal strength that is not modulated. it can.

  As described above, the receiving apparatus 300 according to the nineteenth embodiment includes a light receiving unit 301 that receives a plurality of lights of different colors, on which signals are superimposed by modulation that temporally switches between light emission and non-light emission, and (1) When the ratio of the brightness of each of the plurality of lights received by the light receiving unit 301 to the brightness of each other light is greater than a predetermined value, the signal is demodulated using the plurality of lights (2 ) When one of the plurality of ratios is smaller than a predetermined value, the demodulator 302 includes a demodulator 302 that demodulates the signal using light other than the light whose ratio is smaller than the predetermined value.

  As a result, the receiving apparatus 300 excludes light of low intensity that is not modulated from the illumination light irradiated by the second operation in the illumination light communication apparatus 100 described above, and generates a visible light signal from the remaining light. Can be demodulated. Therefore, the receiving apparatus 300 can stably demodulate the visible light signal.

[19.11 Example of use of illumination light communication device]
Hereinafter, usage examples of the illumination light communication apparatus 100 will be described. 77 and 78, the usage example of the illumination light communication apparatus 100 as an RGB projector, the usage example of the illumination light communication apparatus as an RGB spotlight shown in FIG. 79, and the like.

(Embodiment 20)
In the present embodiment, a modification of the tenth embodiment will be described.

  In visible light communication, the required amount of change in illumination light varies depending on the installation of the illumination light communication device. For example, when the illumination light communication device is installed outdoors during the daytime, there is a possibility that the illumination light emitted from the illumination light communication device cannot be correctly detected by the reception device because the surroundings are bright. In this embodiment, an illumination light communication device that can reduce reception errors in visible light communication due to the influence of ambient ambient light and can suppress an increase in power consumption will be described.

  First, the configuration of the illumination light communication apparatus according to the present embodiment will be described. FIG. 123 is a block diagram showing a configuration of illumination light communication apparatus 100B according to the present embodiment. The illumination light communication apparatus 100B illustrated in FIG. 123 is different from the illumination light communication apparatus 100 illustrated in FIG. 65 in that a communication module 103B is provided instead of the communication module 103. The communication module 103B is different from the communication module 103 of FIG. 65 in that it further includes a mode switching unit 171 and an illuminance sensor 172. In addition, functions are added to the external synchronization signal input unit 124 and the control unit 125.

  Illumination light communication apparatus 100B is a signboard illumination apparatus used for, for example, road guidance.

  The illuminance sensor 172 detects the illuminance (brightness) around the illumination light communication device 100B.

  The mode switching unit 171 selects one of the normal mode (first operation mode) and the outdoor mode (second operation mode) based on the detection result of the illuminance sensor 172, and a mode switching signal indicating the selected operation mode S6 is generated. The mode switching signal S6 is sent to the control unit 125 via the external synchronization signal input unit 124.

  Specifically, when the illuminance around the illumination light communication device 100B is lower than a predetermined threshold, the mode switching unit 171 selects the normal mode, and the illuminance around the illumination light communication device 100B is predetermined. If it is higher than the threshold, the outdoor mode is selected. That is, when the illumination light communication apparatus 100B is installed indoors, the normal mode is selected. Further, when the illumination light communication device 100B is installed indoors, the normal mode is selected when the surroundings are dark (for example, at night or on a cloudy day). In addition, when the illumination light communication device 100B is installed indoors, the outdoor mode is selected when the surroundings are bright (for example, on a sunny day).

  Note that the mode switching unit 171 may use the amount of disturbance light having the same frequency as the modulated illumination light (light intensity or illuminance) as the ambient illuminance.

  The control unit 125 switches the on-duty and the like of the modulation signal S1 according to the operation mode indicated by the mode switching signal S6.

  Next, the operation of the illumination light communication apparatus 100B will be described. FIG. 124 is a diagram showing operations of the illumination light communication apparatus 100B in the normal mode and the outdoor mode.

  As shown in FIG. 124, the operation in the normal mode is the same as the operation in the tenth embodiment described above.

  In the outdoor mode, the control unit 125 lowers the on-duty of the modulation signal S1, that is, the on-duty of the modulation switch 121, as compared with the normal mode, and increases the current command value S2 as compared with the normal mode. For example, when 4PPM is used, the on-duty in the normal mode is 75%, and the on-duty in the outdoor mode is 25%.

  Here, the modulation scheme used in the twentieth embodiment is 4PPM, for example, and is a modulation scheme with a constant on-duty regardless of the logical value of the communication signal.

  In addition, when the on-duty is changed, the constant current feedback operation in the power supply circuit 102 is controlled so that the average current per unit time becomes constant. Thereby, the current value in the on section in the outdoor mode is higher than the current value in the on section in the normal mode. The control unit 125 increases the current set value Is so as to follow the increase in the current value.

  When the power supply circuit 102 does not have a constant current control function, the output current or output voltage of the power supply circuit 102 may be controlled based on an instruction from the control unit 125. For example, the product of the on-duty and the current value is controlled to be substantially equal between the outdoor mode and the normal mode. That is, control is performed so that the product of the on-duty and the current setting value Is is approximately equal in the outdoor mode and the normal mode.

  As described above, in the outdoor mode, the illuminance of the illumination light is increased by setting the current value in the ON section higher than in the normal mode. Thereby, a visible light signal can be correctly detected in the receiving device even during the daytime outdoors. Furthermore, in the outdoor mode, the on-duty is set lower than in the normal mode. Thereby, an increase in current consumption can be suppressed. Further, since it is not necessary for the power supply circuit to support high output, for example, it is possible to easily add a visible light communication function using a post-installation communication module 103B.

  As described above, the illumination light communication apparatus 100B according to the twentieth embodiment includes the light source 101 that emits illumination light, the modulation switch 121 that is connected in series with the light source 101, and that interrupts the current flowing through the light source 101, and the modulation switch 121. A control unit 125 that controls the value of the current flowing in the light source 101 while superimposing a signal on the illumination light by modulating the illumination light by controlling on and off. In the normal mode (first operation mode), the control unit 125 sets the on-duty, which is the ratio of time during which the modulation switch 121 is turned on, in the repetition cycle of turning on and off the modulation switch 121 to the first ratio, The current value of the current flowing through the light source 101 during the period in which the modulation switch 121 is on is set to the first current value, and the on-duty is lower than the first ratio in the outdoor mode (second operation mode). The current value is set to a second current value higher than the first current value.

  Thereby, the illumination light communication apparatus 100B can reduce a reception error in visible light communication due to the influence of ambient ambient light, and can suppress an increase in power consumption of the entire illumination light communication apparatus 100B in the outdoor mode.

  The illumination light communication apparatus 100B further includes an illuminance sensor 172 that detects the illuminance around the illumination light communication apparatus 100B. The controller 125 operates in the normal mode when the illuminance detected by the illuminance sensor 172 is lower than a predetermined threshold, and operates in the outdoor mode when the illuminance detected by the illuminance sensor 172 is higher than the threshold.

  Thereby, the illumination light communication apparatus 100B can select an appropriate operation mode in accordance with the surrounding illuminance.

  The illumination light communication device 100B further includes a current suppression circuit 122 that is connected in series with the light source 101 and the modulation switch 121 and suppresses the current flowing through the light source 101 so as not to exceed the current set value Is. The controller 125 sets the current set value Is higher in the outdoor mode than in the normal mode.

  Thereby, the illumination light communication apparatus 100B can appropriately control the current value according to the operation mode.

  The communication module 103B according to the twentieth embodiment is a communication module 103B that modulates illumination light that can be attached to and detached from the illumination device. The communication module 103B is connected in series with the light source 101 included in the illumination device, and the current flowing through the light source 101 is An intermittent modulation switch 121 and a control unit 125 that controls the value of the current flowing in the light source 101 while superimposing a signal on the illumination light by modulating the illumination light by controlling on and off of the modulation switch 121. . In the normal mode (first operation mode), the control unit 125 sets the on-duty, which is the ratio of time during which the modulation switch 121 is turned on, in the repetition cycle of turning on and off the modulation switch 121 to the first ratio, The current value of the current flowing through the light source 101 during the period in which the modulation switch 121 is on is set to the first current value, and the on-duty is lower than the first ratio in the outdoor mode (second operation mode). The current value is set to a second current value higher than the first current value.

  In the above description, an example has been described in which the mode switching unit 171 switches the operation mode according to the ambient illuminance, but the operation mode is switched according to the time as in the illumination light communication device 100C illustrated in FIG. 125. Also good. 125C differs from the illumination light communication apparatus 100B shown in FIG. 123 in that the communication module 103C includes a timer 173 that detects time instead of the illuminance sensor 172.

  The control unit 125 operates in the normal mode when the time detected by the timer 173 is within a predetermined setting period, and operates in the outdoor mode when the time detected by the timer 173 is outside the setting period. . For example, the set period is a bright time zone during the day.

  Thus, the operation mode can be switched with a simpler configuration than when the illuminance sensor 172 is used.

  The setting period may be set by the user. The operation mode may be switched based on a user operation or an instruction from an external device. Furthermore, you may combine these some control. For example, when the user sets indoor and outdoor, the normal mode is always selected when the indoor setting is performed, and when the outdoor setting is performed, the illuminance sensor 172 or the timer 173 Switching of the operation mode based on the detection result may be performed.

  In the twentieth embodiment, as in the tenth embodiment, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order. However, the light source 101, the modulation switch 121, and the current are connected in series. The order of the series connection of the suppression circuit 122 is not limited to this.

  Hereinafter, a usage example of the illumination light communication device 100B (100C) will be described. FIG. 126 is a diagram illustrating a usage example of the illumination light communication device 100B. For example, as shown in FIG. 126, the illumination light communication device 100B is a signboard illumination device used for road guidance and the like. The visible light receiver receives a visible light signal when the user captures the light emitted by the illumination light communication device 100B with a visible light receiver such as a smartphone.

(Embodiment 21)
In the twenty-first embodiment, an illumination light communication device and a communication module that suppress deterioration of a reception error rate caused by a ripple even when the power supply current has a ripple will be described.
Furthermore, an illumination optical communication device and a communication module that suppress an increase in power loss due to current suppression of the current suppression circuit even when there is a ripple in the power supply current will be described.

  In general, the output current of a power supply circuit often includes a ripple having a frequency twice the commercial power supply frequency. In addition, the magnitude (variation range) of the ripple is not constant but varies depending on the magnitude of the load.

  The ripple of the power supply current of the illumination light communication device appears in the fluctuation of the brightness of the illumination light. There is a problem that fluctuations in brightness may cause reception errors in visible light communication. In addition, since the current suppression circuit suppresses the current flowing through the light source so as not to exceed the current set value, there is a problem that power loss due to current suppression can increase if there is a ripple in the power supply current.

  Therefore, the illumination light communication apparatus according to Embodiment 21 is, for example, the illumination light communication apparatus according to Embodiment 1, and includes a current detection unit that detects a current flowing through the light source, and the current suppression circuit includes: A reference source that outputs a variable reference value corresponding to the current setting value; a transistor that is connected in series with the light source and the switch and that suppresses a current flowing through the light source based on the reference value; and the current detection unit And a control circuit for determining the reference value according to the current value detected in step (b), wherein the reference value is determined according to a value determined by a minimum value and a maximum value of a ripple of the current value detected by the current detection unit. Is done. The value determined by the minimum value and the maximum value may be, for example, the minimum value, the maximum value, or the average value. The reference value is determined so that the current setting value is determined by the minimum value and the maximum value.

  Next, the configuration of the illumination light communication apparatus according to Embodiment 21 will be described.

  FIG. 127 is a block diagram illustrating a configuration example of the illumination light communication apparatus according to the present embodiment. The illumination light communication apparatus shown in FIG. 127 includes a control circuit 6k instead of the control circuit 6 and a signal generation circuit SGa instead of the signal generation circuit SG, as compared with the illumination light communication apparatus shown in FIG. 1A or 30A. The point is different. Hereinafter, different points will be mainly described.

  The control circuit 6k determines the reference value according to the current value detected by the current detector. The current detector is, for example, a detection resistor 66. The power supply current is detected by the potential at the terminal of the detection resistor 66 on the current suppression circuit 1 side. The control circuit 6k detects the maximum value and the minimum value of the ripple in a certain period of the power supply current from the current value detected by the current detector, and the current setting value of the current suppression circuit 1 is a value determined by the minimum value and the maximum value ( For example, the reference value is determined so as to be a minimum value.

  The signal generation circuit SGa may be equivalent to the signal generation circuit SG in first to third operation examples described later. Further, in the fourth to eighth operation examples described later, the signal generation circuit SGa further generates a PWM signal having a frequency five times higher than that of the communication signal, and superimposes the PWM signal on the OFF period of the communication signal. .

  Hereinafter, operation examples of the first to eighth operation examples in the twenty-first embodiment will be described.

(First operation example)
Next, a first operation example in Embodiment 21 will be described.

  FIG. 128 is a waveform diagram showing a first operation example of the illumination light communication apparatus according to the twenty-first embodiment. The upper part of the figure shows the detected current value detected by the current detector and control circuit 6k. The detected current value has, for example, a ripple having a frequency twice that of the commercial power supply frequency. The lower part of the figure shows the LED current (current flowing through the load circuit 53). In this example, the control circuit 6k performs control to change the reference value of the reference source 4 according to the minimum value of the ripple current in order to output a variable reference value from the reference source 4. Specifically, the control circuit 6k determines the reference value so that the current setting value of the current suppression circuit 1 becomes the minimum ripple value. The current suppression circuit 1 suppresses the current flowing through the light source (the load circuit 53 which is an LED) so as not to exceed the current set value (here, the ripple minimum value).

  As shown in the lower part of FIG. 128, according to the first operation example, the fluctuation portion of the LED current indicated by the thin solid line and the broken line, that is, the portion exceeding the current set value (here, the ripple minimum value) is suppressed. In this way, the LED current can be shaped into a collection of rectangular waves having the same amplitude over the entire section in which the illumination light is modulated by the communication signal. Thereby, even if there is a ripple in the power supply current, fluctuations in illumination light can be suppressed and occurrence of reception errors in the receiving apparatus can be suppressed.

(Second operation example)
Subsequently, a second operation example according to the twenty-first embodiment will be described.

    FIG. 129A is a waveform diagram illustrating a second operation example of the illumination light communication apparatus according to the twenty-first embodiment. The lower part of the figure shows the LED current (current flowing through the load circuit 53). In this example, the control circuit 6k determines the reference value so as to be a predetermined value that is larger than the minimum value of the ripple current and smaller than the maximum value.

  According to the second operation example, the portion of the LED current indicated by the thin solid line and the broken line, that is, the portion exceeding the current set value (here, the predetermined value) is suppressed. In both FIG. 128 and FIG. 129A, the portion of the LED current indicated by the thin solid line and the broken line is suppressed by the current suppression circuit 1 and becomes a power loss. FIG. 129A can reduce the power loss due to the suppression of the current suppression circuit 1 compared to FIG. 128. Moreover, even if there is a ripple in the power supply current, fluctuations in illumination light can be suppressed, and occurrence of reception errors in the receiving device can be suppressed.

  FIG. 129B is a waveform diagram illustrating a second operation example of the illumination light communication apparatus according to Embodiment 21. In the figure, the predetermined value in FIG. 129A is specifically set as the average value of the ripple current.

  Note that the predetermined value in FIG. 129A is not limited to the average value. In FIG. 129A, the time width of the portion where the LED current becomes a rectangular wave (the portion corresponding to the thin solid line and the broken line) may be equal to or larger than the width including the portion (for example, communication ID) that is meaningful as the transmission data of illumination light communication.

(Third operation example)
FIG. 130 is a waveform diagram showing a third operation example of the illumination light communication apparatus according to the twenty-first embodiment. The figure shows the detected current value, the current set value or reference value, and the LED current. The current set value is set to the same value as the detected current value. That is, the control circuit 6k sets the reference value so that the current setting value varies with the same cycle as the detected current value.

  In the LED current shown in the figure, the peak of the rectangular wave varies according to the detected current value, but only the overshoot of each rectangular wave (each pulse) is suppressed as shown in the enlarged view in the broken line frame. Therefore, the power loss in the current suppression circuit 1 can be minimized, and the rectangular wave can be formed over the entire section in which the illumination light is modulated by the communication signal, so that it is difficult to cause a reception error of the receiving device.

(Fourth operation example)
FIG. 131 is a waveform diagram showing a fourth operation example of the illumination light communication apparatus according to the twenty-first embodiment. In the figure, the current set value is the same as the third operation example in that it is the same value that fluctuates in the same cycle as the detected current value.

  The signal generation circuit SGa generates a PWM signal having a frequency five times that of the communication signal, and superimposes the PWM signal on the low level section of the communication signal.

  The on section in the figure corresponds to the high level section of the communication signal, and the transistor 2 is in the on state. The off section in the figure corresponds to the low level section of the communication signal, and the PWM signal is superimposed. All of the off intervals in the figure are intervals in which the transistor 2 is not turned off but is switched at high speed by the PWM signal.

  In the enlarged view of the broken line portion of the figure, Ion indicates the LED current in the ON section (here, the same value as the current set value). Ioff_max indicates the maximum value of the LED current in the off section. Ioff_ave indicates an average value of the LED current values in the off section, and is represented by (Ioff_max) × (on-duty ratio of PWM signal). Ioff_min represents the minimum value (here, 0) of the LED current value in the off section.

  The average value Ioff_ave is set to be (immediately before Ion) − (ripple minimum value), in other words, (current setting value) − (ripple minimum value). That is, the difference between Ion and Ioff_ave is set to be constant for any rectangular wave. Thereby, the brightness difference between the ON section and the OFF section of the communication signal is kept constant.

  As described above, similarly to the third operation example, the control circuit 6k performs control to change the reference value of the reference source 4 so that the current set value becomes the same value as the detected current value.

  The signal generation circuit SGa generates a PWM signal so that the average current value Ioff_ave = (immediately before Ion) − (ripple minimum value) in the off period in order to make the contrast between the on period and the off period constant. The PWM signal is superimposed on the off interval of the communication signal.

  Thereby, an overshoot can be suppressed from the rectangular wave in the ON section of the communication signal, and the power loss in the current suppression circuit 1 can be minimized. Even if the LED current (I_on) increases due to the ripple, an increase in power loss in the current suppression circuit 1 is suppressed. Since the difference in brightness between the ON section and the OFF section of the communication signal is constant, it is possible to make it difficult for a receiving device to receive a reception error.

(Fifth operation example)
FIG. 132 is a waveform diagram showing a fifth operation example of the illumination light communication apparatus according to the twenty-first embodiment. The fifth operation example shown in the figure is different from the fourth operation example in that the modulation depth by the communication signal is suppressed when the LED current (or the current set value) is equal to or smaller than the threshold value. Hereinafter, different points will be mainly described. Here, the modulation depth refers to Ion-Ioff_ave or a difference in brightness of illumination light between the on section and the off section.

  The signal generation circuit SGa changes the modulation depth in the section A and the section B in the figure, in other words, suppresses the modulation depth in the section B. Section A is a section in which the current set value (or LED current) exceeds the threshold value. Section B is a section in which the current set value (or LED current) is equal to or less than the threshold value.

  In the section A, the signal generation circuit SGa generates the PWM signal so that the average current value Ioff_ave = (immediately before Ion) − (ripple minimum value) in the off section. In the section B, the signal generation circuit SGa generates the PWM signal so that the current average value Ioff_ave = (previous Ion) − (ripple minimum value) −α1 in the off section, that is, the modulation depth is suppressed by α1. To do. α1 may satisfy 0 <α1 <(ripple minimum value).

  According to the fifth operation example, by suppressing the current change amount by suppressing the modulation depth in the section B, it is possible to reduce the power loss as compared with the fourth operation example.

(Sixth operation example)
FIG. 133 is a waveform diagram showing a sixth operation example of the illumination light communication apparatus according to the twenty-first embodiment. The figure differs from the fifth operation example shown in FIG. 132 in that neither modulation by a communication signal nor high-speed switching is performed in the section B. Hereinafter, different points will be mainly described.

  In the section B, the signal generation circuit SG does not generate a communication signal nor a PWM signal for high-speed switching. In other words, the modulation depth is suppressed to 0 (zero).

  In this case, the section A may be longer than the time including a portion (for example, communication ID) that is meaningful as transmission data for illumination light communication.

  According to the sixth operation example, it is possible to further suppress loss due to the current suppression circuit 1 while suppressing occurrence of a reception error in the reception device.

(Seventh operation example)
FIG. 134 is a waveform diagram showing a seventh operation example of the illumination light communication apparatus according to the twenty-first embodiment. The figure is different from the fifth operation example shown in FIG. 132 in that the section in which the modulation depth is suppressed is not the section B but the section A. Hereinafter, different points will be mainly described.

  In the section A, the signal generation circuit SGa generates the PWM signal so that the average current value Ioff_ave = (Ion immediately before) − (ripple minimum value) −α1 in the off section. In the section B, the signal generation circuit SGa generates the PWM signal so that the average current value Ioff_ave = (immediately before Ion) − (ripple minimum value) in the off section.

    According to the seventh operation example, by suppressing the modulation depth in the section A in which the current change is larger than that in the section B, it is possible to further suppress the loss due to the current suppression circuit 1 compared to the fifth operation example.

(Eighth operation example)
FIG. 135 is a waveform diagram showing an eighth operation example of the illumination light communication apparatus according to the twenty-first embodiment. The figure differs from the sixth operation example shown in FIG. 134 in that neither modulation by a communication signal nor high-speed switching is performed in the section A. Hereinafter, different points will be mainly described.

  In the section A, the signal generation circuit SG does not generate a communication signal nor a PWM signal for high speed switching. In other words, the modulation depth is suppressed to 0 (zero).

  In this case, the section B should just be more than the time which contains a part (for example, communication ID) meaningful as transmission data of illumination light communication.

  According to the eighth operation example, it is possible to further suppress loss due to the current suppression circuit 1 while suppressing occurrence of a reception error in the reception device.

(Embodiment 22)
In the twenty-second embodiment, when the reference power source of the current suppression circuit 1 or the dual-purpose control circuit 1b constituting the illumination light communication device becomes an inappropriate value and may cause an excessive power loss, the situation can be quickly resolved by a simple method. A highly reliable illumination optical communication device will be described that detects the current and shifts to the protection mode.

  FIG. 136 is a diagram illustrating a configuration example of the modulation circuit 70b which is a premise of the twenty-second embodiment. The modulation circuit 70b is a specific example of the dual-purpose control circuit 1b shown in FIG. 50A of Embodiment 7, for example, and is a part of the illumination light communication device or the communication module 10. FIG. 136 shows an example in which an optimum current setting value is indirectly obtained by feeding back the voltage applied to the modulation circuit 70b to the reference power source only during the period when the modulation circuit 70b is energized. In FIG. 136, the MOSFET n71 and the source resistor n72 constitute a constant current main circuit, and the voltage drop of the source resistor n72 is input to the negative terminal of the operational amplifier n73 via the resistor n76. A parallel circuit of a capacitor n80 and a resistor n81 is connected to the plus terminal of the operational amplifier n73, and charges are accumulated in the capacitor n80 via a resistor n82 and a MOSFET n83. A communication signal (for example, an ID signal) is input to the negative terminal of the operational amplifier n73 via the inverter n86 and the resistor n77, and the MOSFET n71 is intermittently connected and the MOSFET n83 is turned on and off via the resistor n84. Thus, both the MOSFET n71 and the MOSFET n83 are turned on while the communication signal is on, and the capacitor n80 is charged by the voltage drop of the MOSFET n71 and the resistor n72 that occurs during the energization period of the modulation circuit 70b. The resistors n78 and n85 are gate resistors, the resistor n81 is a discharge resistor, and the capacitor n79 is a speed-up capacitor.

  In the method of generating the reference power supply as shown in FIG. 136 using its own voltage drop, an extreme increase in circuit loss due to a small constant current set value is unlikely to occur as shown in FIG. Since the average value of the LED current is controlled to be substantially constant by the LED power supply, a large loss in the modulation circuit 70b means that the voltage drop is large, but if the voltage drop is increased, the reference power supply rises. This is because the feedback that reduces the voltage drop functions. Further, it is difficult to consider an increase in loss when the ON-Duty is extremely small as shown in FIG. This is because the target communication signal is 4 PPM, the average ON-Duty is 75%, and even if there is a local fluctuation, it is transient and does not greatly affect the average power loss.

  However, as an extreme case, the loss of the constant current main circuit increases and overheats in the event of a failure such as a circuit portion for generating a reference potential in the capacitor n80 or a short circuit of the capacitor n80 or the resistor n81. A conceivable situation is possible.

  In order to solve such a situation, the illumination light communication apparatus according to the twenty-second embodiment includes a detection circuit that detects whether or not a current flowing through the light source and the current suppression circuit exceeds a predetermined amount. When it is detected that the fixed amount has been exceeded, the current suppression circuit is controlled to suppress the current.

  The illumination light communication apparatus according to the twenty-second embodiment also includes a power supply circuit, a smoothing circuit and a load circuit, an intermittent switch, a modulation circuit 70b provided in series with the load circuit and the intermittent switch, and both ends of the modulation circuit 70b. A detection circuit configured in parallel with the modulation circuit 70b to detect a voltage drop during a period in which the intermittent switch is ON, and a detection circuit that includes a feedback circuit that generates a constant current value using voltage. It is good also as a structure provided with the protection circuit which discriminate | determines the output and transfers to protection mode. The detection circuit may be an overpower detection circuit or an overvoltage detection circuit.

  The detection circuit in the illumination light communication apparatus includes a voltage dividing resistor that divides a voltage applied during the period when the intermittent switch is OFF, a means that clamps the divided voltage, and an integration that is charged via the voltage dividing resistor. A capacitor, a discharge circuit comprising a diode and a discharge resistor for discharging the charge of the integration capacitor to the modulation circuit 70b including the intermittent switch while the intermittent switch is ON, a comparator for determining the voltage value of the integral capacitor, and a threshold value A voltage source is preferable.

  In the detection circuit, it is also preferable to charge the control power supply or the capacitor instead of the voltage dividing resistor and the clamping means.

  The detection circuit in the illumination light communication apparatus preferably has a second charging path for the integrating capacitor, and the second charging path is preferably configured by providing a Zener die auto in the discharging circuit.

  The detection circuit in the illumination light communication apparatus includes an integration capacitor of a second charging path configured by providing a Zener diode in the discharge circuit, and is connected to the potential of the first integration capacitor by a wired OR. It is also preferable that the integration capacitor is set to the first integration capacitor.

  When the output (comparator output) of the detection circuit in this illumination light communication apparatus becomes High, it is also preferable to have a latch circuit that holds the state and a short-circuit switch that short-circuits the modulation circuit 70b with the output of the latch circuit.

  Next, the illumination light communication apparatus according to the twenty-second embodiment will be described with reference to FIG. As shown in FIG. 1 and FIG. 50A, the illumination light communication device includes a power supply circuit 52a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53 that is an LED, and an intermittent connection. On the premise of the modulation circuit 70b having a function and composed of a constant current circuit, an overpower detection circuit 90a is provided in parallel with the modulation circuit 70b.

  The overpower detection circuit 90a includes a P-type MOSFET n90, its gate protection resistor n91, an N-type MOSFET n92 provided between the gate terminal of the P-type MOSFET n90 and circuit ground, its gate protection resistor n93, and gate resistor n94. An integration circuit comprising a diode n95, a resistor n96, a capacitor n97 and a discharge resistor n98 provided between the drain terminal of the P-type MOSFET n90 and the circuit ground, and the potential of the capacitor n97 reaches a predetermined value. Comparator n100 and the threshold power supply n99 for determining whether or not The switch circuit is driven by a communication signal, the P-type MOSFET n90 is turned ON while the communication signal is High, and the drain voltage when the modulation intermittent switch (MOSFET n71) is energized is applied to the anode side of the diode n95. . The applied voltage charges the capacitor n97 through the resistor n96, and when the potential becomes equal to or higher than the threshold value of the reference power source n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistor.

  Since the average value of the current flowing through the main circuit (MOSFET n71 and resistor n72) of the modulation circuit 70b is substantially constant by the constant current control function of the power supply circuit 52a, the voltage drop during energization of this main circuit is proportional to the power loss. . Therefore, detecting a state in which this voltage drop is excessive means detecting an overpower.

  FIG. 138 shows the waveform of each part during normal operation. During the period when the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows. As a result, the voltage drop generated at both ends of the MOSFET n71 and the resistor n72 during the energization period is as shown in (c). The product of the LED current (b) and the voltage drop (c) is the power loss shown in (d). These are integrated by the resistor n96 and the capacitor n97, and a substantially DC detection potential is generated in the capacitor n97. However, the threshold value of the reference power source n99 is not reached, and the comparator output is kept low.

  FIG. 139 shows respective waveforms when a normal reference power supply is not generated at the operational amplifier plus terminal of the modulation circuit 70b for some reason and the loss of the modulation circuit 70b becomes excessive. While the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows. The voltage waveform generated at both ends of the MOSFET n71 and the resistor n72 during the energization period is (c). As shown by, the value is larger than normal. Therefore, as shown in (d), the power loss of the constant current main circuit increases, the detection voltage generated in the capacitor n97 also rises and exceeds the threshold value of the reference power supply n99, and the comparator output becomes High.

  FIG. 140 is a diagram showing main circuit loss and overpower detection level in six models with different LED loads. This is a result of measuring the loss of the modulation circuit 70b for each model when normal modulation by a communication signal is performed using six types of LED loads having different load capacities. In any case, the resistor n81 is adjusted so as to set the optimum operating point at which the circuit loss is minimized within a range in which the LED current waveform can be maintained in a substantially rectangular wave. The magnitude of the main circuit loss is proportional to the LED current value. When the resistance value is gradually decreased from the value of the resistance n81 that is the optimum operating point in each model, the main circuit loss increases, and the detection voltage (capacitor n97) increases and eventually reaches the threshold value of the reference power supply n99. As a result, the output of the comparator n100 becomes High and the operation proceeds to the power protection operation. In this embodiment, the power protection operating point is a substantially constant value regardless of the model.

(Embodiment 23)
An illumination light communication apparatus according to the twenty-third embodiment will be described with reference to FIG. As shown in FIGS. 1 and 50A, the illumination light communication device also includes a power supply circuit 52a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53 that is an LED, and an intermittent connection. On the premise of the modulation circuit 70b having a function and configured by a constant current circuit, an overpower detection circuit 90b is provided in parallel with the modulation circuit 70b.

  The overpower detection circuit 90b includes an integration circuit composed of a resistor n101, a resistor n103, and a capacitor n97, a Zener diode n102 that clamps the potential at the connection point of these resistors n101 and n103 to a constant value, a MOSFET n71 and a resistor of the modulation circuit 70b. a discharge circuit composed of a diode n105 and a resistor n104 for discharging the charge of the capacitor via n72; a comparator n100 for determining that the potential of the capacitor n97 has reached a predetermined value; and a threshold power supply n99 thereof. Yes. When the potential of the capacitor n97 becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistor.

  In the present embodiment, the charging circuit for charging the capacitor n97 is an applied voltage mainly during the period when the MOSFET n71 of the modulation circuit 70b is OFF. This applied voltage varies greatly depending on the target LED load and its power supply characteristics, but the difference between models can be eliminated by the clamping action of the Zener diode n102. That is, the difference in charging voltage can be ignored by clamping below the voltage of the model with the smallest applied voltage among the target models.

  The charge charged in the capacitor n97 is discharged through the diode n105, the resistor n104, and the MOSFET n71 of the modulation circuit 70b through the MOSFET n71 and the resistor n72, and the discharge amount is a voltage drop during the ON period. Dependent. If this voltage drop is large, the electric charge of the capacitor n97 is difficult to discharge, and if the amount of charge is constant, the potential of the capacitor n97 rises. Since a large voltage drop results in a large power loss, overpower can be detected.

  FIG. 142 shows the waveform of each part during normal operation. During the period when the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows. As a result, the voltage drop generated at both ends of the MOSFET n71 and the resistor n72 during the energization period is as shown in (c). The product of the LED current (b) and the voltage drop (c) is the power loss shown in (d). Since the capacitor n97 is charged with the clamped charging voltage, the charging curve is the same every cycle as shown in (e), but the discharging curve depends on the waveform of (c) or (d). That is, it is difficult to discharge in a period when the voltage drop of the main circuit is large, and it is easy to discharge in a small period. During normal operation, the charge and discharge are balanced, and the potential of the capacitor n97 does not reach the threshold value of the reference power supply n99, and the comparator output remains low.

  FIG. 143 shows respective waveforms when a normal reference power supply is not generated at the operational amplifier plus terminal of the modulation circuit 70b for some reason and the loss of the modulation circuit 70b becomes excessive. While the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows. The voltage waveform generated at both ends of the MOSFET n71 and the resistor n72 during the energization period is (c). As shown by, the value is larger than normal. Therefore, as shown in (d), the power loss of the constant current main circuit becomes large, and it becomes difficult to discharge the capacitor n97. As a result, the potential of the capacitor n97 rises and exceeds the threshold value of the reference power supply n99, and the comparator output becomes High. Become.

  FIG. 144 shows a result of measuring the loss of the modulation circuit 70b for each model when normal modulation by a communication signal is performed using six types of LED loads having different load capacities. In any case, the resistor n81 is adjusted so as to set the optimum operating point at which the circuit loss is minimized within a range in which the LED current waveform can be maintained in a substantially rectangular wave. The magnitude of the main circuit loss is proportional to the LED current value. When the resistance value is gradually decreased from the value of the resistance n81 that is the optimum operating point in each model, the main circuit loss increases, and the detection voltage (capacitor n97) increases and eventually reaches the threshold value of the reference power supply n99. As a result, the output of the comparator n100 becomes High and the operation proceeds to the power protection operation. According to this embodiment, the power protection operating point varies depending on the model, and a value approximately proportional to the main circuit loss during normal operation can be obtained.

  This characteristic is effective when the same modulator is used for a plurality of models. That is, since the power protection operating point is determined according to the main circuit loss during normal operation, it is possible to alleviate the inconvenience that the margin of detection is reduced or increased in a specific model.

(Embodiment 24)
The illumination light communication apparatus according to the twenty-fourth embodiment will be described with reference to FIGS. 145 and 145. As shown in FIGS. 1 and 50A, the illumination light communication device also has a power supply circuit 52a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of the modulation circuit 70b configured by a constant current circuit, an overpower detection circuit 90c is provided in parallel with the modulation circuit 70b.

  The overpower detection circuit 90c constitutes an integration circuit so as to charge the capacitor n97 from the control power supply via the resistor n101, and a diode n105 for discharging the charge of the capacitor via the MOSFET n71 and the resistor n72 of the modulation circuit 70b. , A discharge circuit including a resistor n104, a comparator n100 for determining that the potential of the capacitor n97 has reached a predetermined value, and a threshold power supply n99 thereof. When the potential of the capacitor n97 becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistor.

  In this embodiment, the capacitor n97 is charged from the control power supply voltage via the resistor n101, so that the circuit configuration can be simplified. Main operations and features are the same as those in the second embodiment. Compared with the second embodiment, since the charging power is generated even during discharging, the control circuit power slightly increases.

(Embodiment 25)
An illumination light communication apparatus according to the twenty-fifth embodiment will be described with reference to FIG. As shown in FIGS. 1 and 50A, the illumination light communication device also has a power supply circuit 52a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of the modulation circuit 70b configured by a constant current circuit, an overpower detection circuit 90d is provided in parallel with the modulation circuit 70b.

  The overpower detection circuit 90d is almost the same as FIG. 141 showing the twenty-third embodiment, but is configured by replacing the diode n105 of the discharge circuit in FIG. 141 with a Zener diode n106. The charge / discharge operation is the same, but an overvoltage protection function can be added in addition to overpower protection with almost the same configuration. The main purpose of overpower protection is to prevent overheating of the element, and since the thermal time constant is relatively large, instantaneousness is not required in the detection response time. However, when overvoltage is applied to the MOSFET n71 of the modulation circuit 70b, the breakdown voltage is reduced. Prompt detection protection is required before reaching. Since the discharge time constant of the capacitor n97 in the present invention is set to a sufficiently small value with respect to the charge time constant, if a Zener diode having an appropriate value is used in the discharge circuit, the capacitor n97 is charged exceeding the Zener voltage. Since the time constant is small, responsiveness to overvoltage can be obtained.

(Embodiment 26)
An illumination light communication apparatus according to the twenty-sixth embodiment will be described with reference to FIG. As shown in FIGS. 1 and 50A, this illumination light communication device also has a power supply circuit 52a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of the modulation circuit 70b composed of a constant current circuit, an overpower detection circuit 90e is provided in parallel with the modulation circuit 70b.

  The overpower detection circuit 90e is configured by combining the twenty-third embodiment and the twenty-sixth embodiment. A first integration circuit that charges a capacitor n97 via a resistor n101 and a resistor n103, a Zener diode n102 that clamps a connection point potential between the resistor n101 and the resistor n102, and a capacitor n108 that is charged via a resistor n104 and a Zener diode n106 A second integration circuit, a diode n107 connected from the capacitor n97 to the capacitor n108, a comparator n100 for determining that the potential of the capacitor n108 has reached a predetermined value, and a threshold power supply n99 thereof. Yes. When the potential of the capacitor n108 becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistor. The time constant of the second integration circuit is set to be sufficiently small with respect to the first integration circuit time constant.

  The operation of the first integrating circuit is the same as that in the twenty-third embodiment. The discharge circuit of the capacitor n97 is composed of a diode n107, a Zener diode n106, and a resistor n104, which is the same as that in the twenty-third embodiment. Therefore, the charging path of the second integrating circuit is shared with the discharging path of the capacitor n97.

  By setting the capacitance value of the capacitor n108 to be very small, the second integration circuit time constant can also be made very small, so that the responsiveness as overvoltage protection is remarkably improved.

(Embodiment 27)
An illumination light communication apparatus according to the twenty-seventh embodiment will be described with reference to FIG. As shown in FIGS. 1 and 50A, this illumination light communication device also has a power supply circuit 52a having a function of making the output constant, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of the modulation circuit 70b formed of a constant current circuit, an overpower detection circuit 90 is provided in parallel with the modulation circuit 70b, the output is held by the holding circuit 110, and both ends of the modulation circuit 70b are short-circuited. The MOSFET 111 is configured to be driven. The overpower detection circuit 90 is any one of the overpower detection circuits 90a to 90e.

  The state in which the outputs of the overpower detection circuits 90a to 90e are in a high state is that a situation in which a normal modulation operation cannot be performed for some reason occurs, so that the modulation circuit is quickly short-circuited so that the modulation circuit does not intervene. In this case, the function as the optical communication device is lost, but the function as the main illumination is maintained.

  Such measures minimize the influence of the modulation circuit on the LED power supply, and can contribute to the improvement of the system reliability.

(Embodiment 28)
In the twenty-eighth embodiment, the current suppression circuit 1 or the dual-purpose control circuit 1b constituting the illumination light communication apparatus can perform appropriate power loss feedback control regardless of the characteristics of the elements used, and can be used for a plurality of models. An inexpensive and highly reliable illumination optical communication device that contributes to the realization of the system will be described.

  FIG. 149 is a diagram illustrating a configuration example of the modulation circuit 70b which is a premise of the twenty-eighth embodiment. The modulation circuit 70b is a specific example of the dual-purpose control circuit 1b shown in FIG. 50A of Embodiment 7, for example, and is a part of the illumination light communication device or the communication module 10. FIG. 149 shows an example in which an optimum current setting value is indirectly obtained by feeding back the voltage applied to the modulation circuit 70b to the reference power source only during the period in which the modulation circuit 70b is energized. In FIG. 149, the MOSFET n71 and the source resistor n72 constitute a constant current main circuit, and the voltage drop of the source resistor n72 is input to the negative terminal of the operational amplifier n73 via the resistor n76. A parallel circuit of a capacitor n80 and a resistor n81 is connected to the plus terminal of the operational amplifier n73, and charges are accumulated in the capacitor n80 via a resistor n82 and a MOSFET n83. The communication signal is input to the negative terminal of the operational amplifier n73 via the inverter n86 and the resistor n77, and the MOSFET n71 is intermittently turned on and the MOSFET n83 is turned on and off via the resistor n84. Thus, both the MOSFET n71 and the MOSFET n83 are turned on while the communication signal is on, and the capacitor n80 is charged by the voltage drop of the MOSFET n71 and the resistor n72 that occurs during the energization period of the modulation circuit 70b. The resistors n78 and n85 are gate resistors, the resistor n81 is a discharge resistor, and the capacitor n79 is a speed-up capacitor.

  The circuit operation of FIG. 149 will be described with reference to the operation waveforms shown in FIG. The inverted communication signal is input to the negative terminal of the operational amplifier n73 via the resistor n77. By setting the negative input terminal potential to be higher than the positive terminal potential during the period when the inverted communication signal is High, the output of the operational amplifier n73 becomes Low and the MOSFET n71 is turned OFF. Further, when the communication signal is low, if the positive terminal of the operational amplifier n73 is set to be higher, the output from the operational amplifier n73 is High, the MOSFET n71 is turned on, and the LED current flows. These situations are as shown in FIGS. 150 (a) to (c). The voltage drop generated in the resistor n72 by the LED current is divided by the resistors n76 and n77 and applied to the negative terminal of the operational amplifier n73, and the output of the operational amplifier n73 is set so that the negative terminal potential is substantially equal to the positive terminal. Is controlled.

  At this time, the gate voltage of the MOSFET n71 is approximately a value obtained by adding the voltage drop of the resistor n72 to the gate threshold value Vth.

  FIG. 150 (d) shows a voltage waveform applied to the constant current main circuit (MOSFET n71 and resistor n72) during the modulation operation. Since the MOSFET n71 is OFF during the period when the inverted communication signal is High, the voltage value is approximately obtained by subtracting the LED load cutoff voltage from the LED power supply output voltage. Further, since the MOSFET n71 is turned on and the constant current operation is performed while the inverted communication signal is Low, the MOSFET n71 operates in the amplification region with a voltage drop and a voltage drop of the resistor n72. FIG. 150 (e) shows only the voltage drop, and since the LED current flows during this period, these are also diagrams of power loss.

  The MOSFET n71 is turned on and off by the inverted communication signal, and the MOSFET n83 is also turned on and off. The inverted communication signal is inverted (ie, non-inverted communication signal) by the inverter n86 and applied to the gate terminal of the MOSFET n83 via the resistor n84, so that the ON-OFF operation opposite to the MOSFET n71 is performed. That is, since the inverted communication signal is ON during the Low period, the capacitor n80 is charged via the resistor n82 due to the voltage drop shown in FIG. As a result, a reference potential as indicated by a broken line in FIG. 150E is generated, and the current value of the modulation circuit 70b is set by this potential. The reference potential can be adjusted by the resistor n82 and the resistor n81, and a power loss feedback function is achieved by an appropriate setting. That is, if the voltage drop of the modulation circuit 70b increases for some reason, the charge amount of the capacitor n80 also increases, the gate voltage of the MOSFET n71 rises and current flows easily, and the voltage drop of the modulation circuit 70b is reduced.

  These are switching operations using an operational amplifier and depend greatly on the characteristics of the operational amplifier. FIG. 151 shows the result of simulating the rising waveform of the gate voltage of the MOSFET n71 and the LED current when the inverted communication signal falls. 151 shows the waveform of the falling edge of the inverted communication signal and the waveform of the rising edge of the LED current. In the lower part of FIG. 151, the waveform of the rising edge of the gate voltage is shown.

  FIG. 152 shows the result of simulating the gate voltage of the MOSFET n71 and the falling waveform of the LED current when the inverted communication signal rises. The upper stage of FIG. 152 shows the waveform of the rising edge of the inverted communication signal and the waveform of the falling edge of the LED current. In the lower part of FIG. 152, the waveform of the falling edge of the gate voltage is shown.

  As described above, when the inverted communication signal is inverted from High to Low, the output of the operational amplifier, that is, the gate voltage of the MOSFET n71 becomes High, but its rise has a slope. The degree of the inclination greatly depends on the output characteristic of the operational amplifier and is presented as a slew rate characteristic. In addition, the capacitance component present around the operational amplifier n73 is also affected, and in particular, the capacitance of the capacitor provided between the output terminal and the negative input terminal, the gate capacitance (Ciss) of the MOSFET, and the like are large.

  By using an operational amplifier with a large slew rate and a MOSFET with a small gate capacitance, the capacitor capacitance connected to the operational amplifier output such as the capacitor n79 can be made as small as possible, so that the rising and falling slopes of the gate voltage can be made steep. .

  In FIG. 151, the gate voltage of the MOSFET n71 rises with a slope from the falling point of the inverted communication signal, and when the voltage reaches the gate threshold value (Vth) of the MOSFET n71, the LED current starts to flow. The gate voltage rises to a value obtained by adding the voltage drop generated in the resistor n72 by the LED current, and the LED current becomes flat.

  The time from when the inverted communication signal falls until the LED current reaches 10% of the flat portion is defined as the rise delay time.

  In FIG. 152, the gate voltage of MOSFET n71 falls with a slope from the rise of the inverted communication signal, and the LED current is cut off when the voltage reaches the gate threshold (Vth) of MOSFET n71. The time from when the inverted communication signal rises until the LED current reaches 90% of the flat portion is defined as a fall delay time. When the delay time of the rise and fall is compared, it can be seen that the rise delay time is much longer.

  FIG. 153 shows a modulation operation waveform with a rise delay time. In response to the inverted communication signal (a), the gate voltage of the MOSFET n71 is intermittently interrupted (b), so that a delay occurs in the rise of the LED current waveform (c).

  As a result, a delay also occurs in the fall of the main circuit applied voltage (d), so that a voltage other than the voltage drop is superimposed on the waveform (e) to be captured as a voltage drop while the inverted communication signal is Low. As a result, there is a problem that the reference potential generated in the capacitor n80 is level 2 (indicated by a one-dot chain line) which is higher than originally expected level 1 (indicated by a dashed line), and an expected power loss feedback function cannot be obtained.

  In order to solve this problem, the current suppression circuit of the illumination light communication apparatus according to the twenty-eighth embodiment has a variable reference value corresponding to the current set value according to the current value flowing through the switch and the current suppression circuit. A dynamically generating reference source; and a delay circuit that delays the generated reference value by a predetermined time length, wherein the current suppression circuit is configured to reduce a current flowing through the light source based on the delayed reference value. Suppress.

  The illumination light communication apparatus according to the twenty-eighth embodiment includes a power supply circuit, a smoothing circuit and a load circuit, an intermittent switch, a modulation circuit 70b provided in series with the load circuit and the modulation intermittent switch, and the modulation circuit 70b. And a delay circuit that delays the timing at which a feedback switch that performs an operation opposite to that of the intermittent switch is turned on is provided in the feedback circuit. It may be.

  It is also preferable that the feedback circuit in the illumination light communication device includes voltage clamping means.

  It is preferable that the delay time set by the delay means of the feedback circuit in this illumination light communication apparatus is sufficiently longer than at least the rise delay time of the modulation intermittent switch.

  The delay time set by the delay means of the feedback circuit in this illumination light communication apparatus is preferably larger than the rise delay time of the modulation intermittent switch and smaller than the minimum pulse width included in the communication signal.

  It is also preferable that the feedback switch in this illumination light communication apparatus has a capacitor element at least between its control terminal and circuit ground.

  An illumination light communication apparatus according to the twenty-eighth embodiment will be described with reference to FIG. As shown in FIGS. 1A and 50A, this illumination light communication apparatus has a power supply circuit 52a having a function of making the output constant current, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of a modulation circuit composed of a constant current circuit, the configuration of the modulation circuit is improved. Specifically, a gate drive circuit of a second switch (feedback switch: MOSFET n83) that is turned on and off in synchronization with a constant current switch (modulation intermittent switch: MOSFET n71) that also functions to be interrupted according to an inverted communication signal Further, a delay circuit for delaying the ON timing is added.

  The added delay circuit includes an inverter n86 that inverts (that is, non-inverts) the inverted communication signal, an integration circuit that includes a resistor n90 and a capacitor n89, a drawing circuit that includes a diode n92 and a resistor n93, and a waveform shaping buffer element n88. Consists of. After the inverted communication signal is inverted by the inverter n86, the rise is blunted by the integration circuit described above, and the rise delay time is generated using the input threshold value of the buffer element n88. When the inverted communication signal is switched to High, the charge of the capacitor n89 is quickly discharged through the extraction circuit.

  The operation of FIG. 154 showing the twenty-eighth embodiment will be described with reference to FIG. In response to the inverted communication signal (a), the gate voltage of the modulation intermittent switch MOSFET n71 is intermittently inclined ((b)), so that a delay occurs in the rise of the LED current waveform (c). As a result, the fall of the main circuit applied voltage ((d)) is also delayed, but the rise of the gate voltage of the feedback switch MOSFET n83 is also delayed by the delay circuit of the present invention ((e)). Voltage components other than the voltage drop are removed, and the reference potential can be generated in the capacitor n80 only by the voltage drop as shown in (f). The obtained reference potential is close to the originally expected level 1 (indicated by a broken line), and an appropriate power loss feedback function can be obtained.

  In the modulation circuit 70c of FIG. 154, a Zener diode z94 is added between the drain terminal of the MOSFET n83 and the circuit ground. Its main purpose is to reduce the breakdown voltage of the feedback switch MOSFET n83. The feedback circuit is intended only for a voltage drop during the period when the modulation intermittent switch MOSFET n71 is ON, and does not require a voltage to be applied during the period when the MOSFET n71 is OFF.

  Therefore, even if the voltage is clamped by the zener diode z94, the feedback performance is not adversely affected. Rather, by using a low-breakdown-voltage and small-capacitance element as the MOSFET n83, parasitic capacitance can be reduced, so that more accurate feedback performance can be obtained.

  A main effect of the twenty-eighth embodiment is a so-called MT effect that can add an optical communication function to a plurality of LED lighting fixtures using one modulator. Compared to the case where each modulator corresponding to a plurality of LED lighting fixtures is required, in addition to the cost effect due to the reduction of the product type, a great effect can be expected in promoting the spread of visible light communication.

  156 to 159 show various characteristics when a gate voltage rising delay circuit of MOSFET n83 based on the present invention is added to a plurality of models having different LED currents and load capacities. FIG. 156 shows the results of actual measurement of the relationship between the LED current and the constant current main circuit loss of three types of LED lighting fixtures having different LED current ratings. It can be seen that the main circuit loss increases almost in proportion to the value of the LED current, and hardly depends on the delay time of the rise of the gate voltage of the MOSFET n83. FIG. 157 is a result of actually measuring the relationship between the LED load power and the constant current main circuit loss, and hardly depends on the delay time of the rise of the gate voltage of the MOSFET n83. Compared with the result of FIG. 156, it becomes clearer that the constant current main circuit loss depends on the LED current rather than the load power. These results are obtained by adjusting the resistance n81 (reference resistance) provided in parallel with the capacitor n80 each time, and measuring the constant current main circuit power loss at the point (optimum resistance value) at which the LED current waveform becomes a substantially rectangular wave. ing.

  FIG. 158 shows the results of actual measurement of the relationship between the LED current and the optimum resistance value (resistance 81) of three types of LED lighting fixtures having different LED current ratings. As the delay time of the rise of the gate voltage of the MOSFET n83 is increased, the optimum resistance value of the resistor n81 is shifted to the larger one for all three models. When the delay time is lengthened, the period for taking in the voltage drop of the modulation circuit 70b is shortened, and as a result, the voltage formed in the capacitor n80 is lowered, so that the constant current main circuit loss is increased (the LED current waveform is a rectangular wave). Maintenance). Since the optimum adjustment point can be found by increasing the value of the reference resistor n81, the optimum adjustment resistance value of the resistor n81 increases with the delay time. In this case, the rise delay time of the modulation intermittent switch (MOSFET n71) was approximately 5 usec. Further, the large difference between the optimum resistance values without delay and with delay is considered to be due to the fact that voltages other than the main circuit voltage drop were taken in without delay. FIG. 159 shows the results of actual measurement of the relationship between the LED load power (load capacity) and the optimum resistance value (resistance n81) in the above three types of LED lighting fixtures. As in the case of FIG. 158, the optimum resistance value of the resistor n81 is shifted to the larger one as the delay time of the rise of the gate voltage of the MOSFET 83 is increased. The reason is also the same as in the case of FIG.

  Considering the results of FIGS. 158 and 159 from the viewpoint of so-called MT which can add an optical communication function to a plurality of LED lighting fixtures using a single modulator, the optimum resistance value is fixed to one so that the current It is desirable that three resistance values (resistors 81) in the difference or load power difference are close to each other. Therefore, it can be seen that the presence of a delay is preferable to the case where there is no delay, and that the longer the delay time is, the more preferable the delay time is in the range of 9 to 24 usec. Note that when the delay time is 50 usec, the characteristics of the delay time of 24 usec are translated, and even if the delay time is increased more than necessary, only the optimum resistance value is increased and three optimum values are obtained. The resistance value does not approach. Moreover, when the optimum resistance value increases, it is necessary to pay attention to the input bias current characteristics of the operational amplifier n73. In the present invention, the voltage drop due to the current flowing through the modulation circuit 70b is fed back to the plus terminal of the operational amplifier to obtain the reference potential. However, when the optimum resistance value increases, the input bias current cannot be ignored. That is, ideally, all the reference potentials generated in the capacitor n80 should be generated by a current obtained by feeding back the voltage drop of the modulation circuit 70b, but there is a current flowing from the internal circuit of the operational amplifier n73 to the input plus terminal. Then, ideal feedback control is inhibited. As a result, it is necessary to use an operational amplifier with a small input bias current, which is generally expensive. Considering this point, it can be said that the delay time of MOSFET n83 is preferably 24 usec rather than 50 usec.

  According to JEITA-CP1223, which is a standard for visible light communication, one slot of the 1-4PPM transmission system is 104.167 usec. Therefore, if the gate voltage rise delay time of the MOSFET 83 is increased to 104 usec, the voltage drop for one slot is reduced. It becomes impossible to take in at all. Therefore, the delay time needs to be less than that. The delay time 50 usec used in the actual measurement in FIGS. 156 to 159 is about 50% of the one slot period. From these results, the gate voltage rise delay time of the MOSFET n83 is set to a range that is larger than the rise delay time of the modulation intermittent switch (MOSFET n71) and smaller than the shortest pulse width included in the communication signal. It can be said that the gate voltage rise delay time is most preferably set in the range of at least twice the rise delay time of the modulation intermittent switch (MOSFET n71) and not more than ½ of the shortest pulse width included in the communication signal.

(Embodiment 29)
FIG. 160 shows only the feedback circuit section of FIG. 154, and naturally shows that the gate capacitance Ciss exists in the feedback switch MOSFET n83. How the gate capacitance affects the reference potential generated in the capacitor n80 will be described with reference to FIG. Since the falling edge of the inverted communication signal is inverted by the inverter n86, a rising waveform is obtained as shown in FIG. 161 (a). The capacitor n89 is charged through the resistor n90, and an integrated waveform as shown in (b) is obtained. When this voltage reaches the input threshold value Vth of the buffer element n88, the output is delayed by the delay time T as shown in (c) and supplied to the gate terminal of the MOSFET n83 via the resistor n84. Since the gate capacitance Ciss exists in the MOSFET n83 as described above, a differential waveform current flows through the gate capacitance when the gate voltage rises as shown in FIG. As a result, as shown in (e), the potential of the capacitor n80 rises and pulsation occurs in the reference potential of the modulation circuit 70b. Originally, it is desirable that the reference potential of the capacitor n80 be generated by a current obtained by feeding back the voltage drop of the modulation circuit 70b. However, the current from the gate circuit of the MOSFET n83 is circulated.

  Embodiment 29 of the present invention has been made in view of the above problems, and FIG. 162 shows a specific circuit configuration. The delay circuit of the twenty-ninth embodiment includes an inverter n86 to which an inverted communication signal is input, a resistor n90 and a capacitor n89 that form an integrating circuit via a diode n92, and a drawing circuit including a transistor n96 and a resistor n85. . FIG. 163 is a diagram for explaining the operation. The capacitor n89 is charged through the resistor n90 and the diode n92 at the fall of the inverted communication signal, that is, the rise voltage (a) of the output of the inverter n86. The integrated voltage waveform of the capacitor n89 is directly applied to the gate terminal of the MOSFET n83, but the voltage of the capacitor n89 becomes an integrated waveform as shown in (b), and the rising slope of the voltage is gentle. Therefore, the current through the gate capacitance Ciss of the MOSFET n83 is also weak as shown in (d), and the influence on the reference potential generated in the capacitor n80 can be reduced. The MOSFET n83 is turned on with a delay of the delay time T when the gate voltage reaches the gate threshold value Vth. Although the fall of the communication signal is not shown, when the output of the inverter n86 becomes Low, a current flows into the inverter n86 via the resistor n90 due to the voltage of the capacitor n89.

  Since this current becomes the base current of the transistor n96, the transistor n96 is turned on, and the charge of the capacitor n89 disappears with the low resistance n85. These form a drawing circuit for the capacitor n89 and quickly turn off the MOSFET 83.

  According to the twenty-ninth embodiment, the MOSFET n83 gate voltage rise delay time of the feedback circuit can be set, and the current flowing from the gate circuit to the capacitor n80 where the reference potential of the modulation circuit 70b is generated can be suppressed and suppressed. Enables highly accurate feedback control. This contributes to further increasing the possibility of so-called MT, in which an optical communication function can be added to a plurality of LED lighting fixtures using a single modulator.

  The illumination light communication device and the communication module according to the present invention have been described based on the embodiments. However, the present invention is not limited to the embodiments. Without departing from the gist of the present invention, various modifications conceived by those skilled in the art have been made in this embodiment, and other forms constructed by arbitrarily combining some components in the embodiments and modifications are also possible. Are included within the scope of the present invention.

  Although the illumination light communication apparatus according to a plurality of embodiments has been described above, the present invention is not limited to these embodiments.

  For example, some or all of the processing units included in the illumination light communication apparatus according to the above embodiment may be realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  Further, the circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  That is, in each of the above embodiments, each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

  The circuit configuration shown in the circuit diagram is an example, and the present invention is not limited to the circuit configuration. That is, like the above circuit configuration, a circuit that can realize a characteristic function of the present invention is also included in the present invention. For example, the present invention includes a device in which a device such as a switching device (transistor), a resistor, or a capacitor is connected in series or in parallel to a certain device within a range in which a function similar to the above circuit configuration can be realized. It is. In other words, the term “connected” in the above embodiment is not limited to the case where two terminals (nodes) are directly connected, and the two terminals ( Node) is connected through an element.

  In addition, the logic level represented by high / low or the switching state represented by on / off is exemplified to specifically describe the present invention, and different combinations of the illustrated logic level or switching state. Therefore, it is possible to obtain an equivalent result.

  In addition, division of functional blocks in the block diagram is an example, and a plurality of functional blocks can be realized as one functional block, a single functional block can be divided into a plurality of functions, or some functions can be transferred to other functional blocks. May be. In addition, functions of a plurality of functional blocks having similar functions may be processed in parallel or time-division by a single hardware or software.

  As mentioned above, although the illumination light communication apparatus which concerns on one or several aspects was demonstrated based on embodiment, this invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, various modifications conceived by those skilled in the art have been made in this embodiment, and forms constructed by combining components in different embodiments are also within the scope of one or more aspects. May be included.

DESCRIPTION OF SYMBOLS 1 Current suppression circuit 1c Bias circuit 2 Transistor (switch)
2a, 2b First switch element 3a Second switch element 4 Reference source 6, 6k Control circuit 6a Shift register 10 Communication module 53 Load circuit (light source)
52a Power supply circuit 64a Overvoltage protection circuit 90, 90a to 90e Overpower detection circuit (detection circuit)
101 Light source 121 Modulation switch (switch)
172 Illuminance sensor 173 Timers 201R, 201G, 201B Illumination unit 202 Dimming control unit 203 Modulation control unit SG Signal generation circuit

Claims (16)

A light source that emits illumination light;
A power supply circuit for supplying a current to the light source and making the current constant;
A switch connected in series with the light source and for interrupting a current flowing through the light source;
A signal generation circuit for generating a binary communication signal for controlling on and off of the switch to modulate the illumination light;
An illumination optical communication apparatus comprising: a current suppression circuit that is connected in series with the light source and the switch and suppresses a current flowing through the light source so as not to exceed a variable current set value. The current suppression circuit is:
A reference source for outputting a variable reference value corresponding to the current set value;
A transistor connected in series with the light source and the switch to suppress a current flowing through the light source based on the reference value;
A partial on-duty ratio of the communication signal is calculated, and when the calculated partial on-duty ratio is a first ratio, the reference value is set to a first value, and a partial on-duty ratio is A control circuit that sets the reference value to a second value smaller than the first value when the second ratio is greater than the first ratio;
The illumination light communication apparatus according to claim 1, wherein the current setting value corresponding to the second value is smaller than a current setting value corresponding to the first value. The illumination light communication apparatus according to claim 1, wherein the power supply circuit performs feedback control for making an average value of supplied current constant. The switch is a transistor;
4. The illumination light communication apparatus according to claim 1, wherein the current suppressing circuit causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source. 5. The light source, the switch, and the current suppression circuit are connected in series in this order,
The illumination light communication apparatus according to claim 1, wherein the current suppression circuit is connected to a ground potential. The current suppression circuit is:
A reference source for outputting the reference value;
A transistor connected in series with the light source and the switch to suppress a current flowing through the light source based on the reference value;
A control circuit having a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting.
The control circuit calculates a partial on-duty ratio of the communication signal based on the n-bit data, and determines the reference value according to the calculated partial on-duty ratio. The illumination light communication apparatus according to 1. A plurality of illumination units that emit light of different colors;
A dimming control unit for controlling the dimming level of each of the plurality of illumination units;
A modulation control unit that superimposes a signal on the light emitted by the plurality of illumination units by temporal switching between light emission and non-emission of each of the plurality of illumination units;
Each of the plurality of illumination units is
The light source;
The switch;
The power supply circuit;
Comprising the current suppression circuit,
The dimming control unit controls the power supply circuit for each of the plurality of illumination units,
When the dimming level is higher than a reference level, amplitude dimming for controlling the intensity of light emitted by the illumination unit is performed,
When the dimming level is lower than the reference level and the modulation is not performed, PWM dimming that controls an on-duty that is a ratio of a light emission time in a light emission and non-light emission repetition period of the illumination unit is performed,
When performing the modulation, the modulation control unit, for each of the plurality of illumination units,
If the dimming level is higher than the reference level, modulation is performed by controlling the switch,
When the dimming level is lower than the reference level, (1) the PWM dimming by the power supply circuit is not performed, and (2) the modulation and the PWM dimming are performed simultaneously by controlling the switch. And the illumination light communication apparatus of any one of Claim 1 to 6 which performs 1st control which modulates so that another illumination part and light emission start timing may synchronize. The illumination light communication device further includes a control unit that superimposes a signal on the illumination light by modulating the illumination light by controlling on and off of the switch, and controls a current value flowing through the light source, Prepared,
The controller is
In the first operation mode, an on-duty, which is a ratio of a time during which the switch is turned on in a repetition cycle of turning on and off the switch, is set to a first ratio, and the light source is turned on during the period when the switch is on. Set the current value of the current flowing through the first current value,
In the second operation mode, the on-duty is set to a second ratio lower than the first ratio, the current value is set to a second current value higher than the first current value,
The illumination light communication device further includes:
With either an illuminance sensor that detects the illuminance around the illumination light communication device and a timer that detects time,
The controller performs any of the operations (i) and (ii). (I) When the illuminance detected by the illuminance sensor is lower than a predetermined threshold, the controller operates in the first operation mode, When the illuminance detected by the illuminance sensor is higher than the threshold value, the operation is performed in the second operation mode. (Ii) When the time detected by the timer is within a predetermined period, the first operation mode The illumination light communication apparatus according to claim 1, wherein the illumination light communication apparatus operates in the second operation mode when the time detected by the timer is outside the period. The illuminating light communication device performs modulation to make two states of lighting light on and off corresponding to a binary communication signal,
The power supply circuit has an overvoltage protection circuit that stops the power supply operation when the output voltage becomes an overvoltage,
The illumination light communication device is:
A first switch element which is the switch;
A bias voltage for turning on the first switch element is applied to the control terminal of the first switch element during a period after the power is turned on and before the signal generation circuit starts an operation of generating the communication signal. A bias circuit to be supplied;
The illumination light communication apparatus according to claim 1, further comprising: a second switch element connected to a control terminal of the first switch element and turned on and off according to the communication signal. The illumination light communication device further includes a current detection unit that detects a current flowing through the light source,
The current suppression circuit is:
A reference source for outputting a variable reference value corresponding to the current set value;
A transistor connected in series with the light source and the switch to suppress a current flowing through the light source based on the reference value;
A control circuit for determining the reference value according to the current value detected by the current detection unit,
The illumination light communication apparatus according to any one of claims 1 to 9, wherein the reference value is determined according to a value determined by a minimum value and a maximum value of a ripple of a current value detected by the current detection unit. The illumination light communication device further includes:
A detection circuit for detecting whether a current flowing through the light source and the current suppression circuit exceeds a predetermined amount;
The illumination light communication apparatus according to claim 1, wherein when the current exceeds a predetermined amount, the current suppression circuit is controlled to suppress the current. The current suppression circuit is:
A reference source that dynamically generates a variable reference value corresponding to the current set value in accordance with a current value flowing through the switch and the current suppression circuit;
A delay circuit for delaying the generated reference value by a predetermined time length,
The illumination light communication apparatus according to claim 1, wherein the current suppression circuit suppresses a current flowing through the light source based on the delayed reference value. A communication module that modulates illumination light, detachable from an illumination device,
A switch connected in series with the light source of the lighting device;
A signal generation circuit for generating a binary communication signal for controlling on and off of the switch to modulate the illumination light;
A communication module comprising a current suppression circuit that is connected in series with the light source and the switch and suppresses a current flowing through the light source so as not to exceed a variable current set value. The switch is a transistor;
The communication module according to claim 13, wherein the current suppression circuit causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source. The light source, the switch, and the current suppression circuit are connected in series in this order,
The communication module according to claim 13 or 14, wherein the current suppression circuit is connected to a ground potential. The current suppression circuit is:
A reference source for outputting the reference value;
A transistor connected in series with the light source and the switch to suppress a current flowing through the light source based on the reference value;
A control circuit having a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting.
16. The control circuit calculates a partial on-duty ratio of the communication signal based on the n-bit data, and determines the reference value according to the calculated partial on-duty ratio. The communication module according to any one of the above.