JP2016063703A - Power supply device and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device and a lighting device providing the same, capable of suppressing undesired rise or fluctuation of an output voltage in a case of a high input voltage or a light load condition at a step-up chopper circuit.SOLUTION: A step-up chopper circuit 16 includes a switching element Q1, and a driver 24 for switching the switching element Q1 according to increase or decrease of a current I flowing the switching element Q1. A current detection part 27 detects a current, proportioning to the current I flowing the switching element Q1 of the step-up chopper circuit 16, and provides the detected current to the driver 24. A microcomputer 33 outputs a signal if at least either a voltage, proportioning to an input voltage Vin of the step-up chopper circuit 16, is equal to a predetermined voltage or more, or a light control signal of the light source 12 is equal to a predetermined light control level or less. Superimpose means 31 superimposes an offset current to the current, detected by the current detection part 27 and provided to the driver 24, if the signal is outputted by the microcomputer 33.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a power supply device having a boost chopper circuit that improves the power factor of an input from a DC power supply unit by switching of a switching element, and an illumination device including the power supply device.

  In conventional boost chopper circuits that control semiconductor switching elements to improve power factor, when the input voltage is high or the load is light, the ON width cannot be narrowed down due to the narrowing limit of the ON width of the switching element, and the control limit As a result, the output voltage may increase. In this regard, for example, it is conceivable to use an overvoltage detecting means or the like to stop the oscillation of the switching element when an overvoltage is detected to suppress an increase in output voltage. However, since the overvoltage detected by such an overvoltage detection means is normally set as a threshold value obtained by increasing the regulation voltage by about 10%, the output voltage of the boost chopper circuit is always 10 at light load. The state of operating at an increase of% is not preferable because the load is large for the load side circuit and the output electrolytic capacitor of the step-up chopper circuit.

US Pat. No. 6,946,819

  The problem to be solved by the present invention is to provide a power supply device that can suppress an undesired increase or fluctuation in output voltage when the input voltage of the boost chopper circuit is high or the load is light, and a lighting device including the power supply device. That is.

  The power supply apparatus according to the embodiment includes a step-up chopper circuit, a step-down unit, a current detection unit, a signal output unit, and a superimposing unit. The step-up chopper circuit includes a switching element and control means for switching the switching element in accordance with increase / decrease of the current flowing through the switching element, and boosts an input voltage from an external power source by switching the switching element. The step-down means steps down the voltage boosted by the step-up chopper circuit and supplies it to the light source. The current detector detects a current proportional to the current flowing through the switching element of the boost chopper circuit and supplies the detected current to the control means. When the voltage proportional to the input voltage of the step-up chopper circuit is equal to or higher than a predetermined voltage value, the signal output means is equal to or lower than the predetermined dimming level set in advance. A signal is output at least at any time. When the signal is output from the signal output means, the superimposing means detects the current by the current detecting unit and superimposes the offset current on the current supplied to the control means.

  According to the present invention, when the voltage proportional to the input voltage of the step-up chopper circuit becomes equal to or higher than a predetermined voltage value set in advance, and the dimming signal of the light source becomes lower than the predetermined dimming level set in advance. In at least one of the cases, the superimposing unit superimposes the offset current on the current supplied from the current detection unit to the control unit by the signal output from the signal output unit, so that the control unit to which this current is supplied It can be expected to suppress irregular oscillation of the switching element and suppress an undesired increase or fluctuation in the output voltage of the boost chopper circuit.

It is a circuit diagram which shows the power supply device of one Embodiment.

  The configuration of one embodiment will be described below with reference to the drawings.

  In FIG. 1, reference numeral 10 denotes an illuminating device. The illuminating device 10 includes a power supply device 11 and a light source 12 that is a light emitting element such as an LED as a load.

  That is, the power supply device 11 is for a lighting device that turns on the light source 12. The power supply device 11 includes a power supply unit 15 connected to a commercial AC power source e that is an external power supply (AC power supply unit), and the power supply. A step-up chopper circuit 16 that outputs a DC voltage to the unit 15 and a step-down chopper circuit 17 that is a step-down means that is electrically connected to the step-up chopper circuit 16 and supplies power to the light source 12 are provided.

  The power supply unit 15 is an input capacitor of a step-up chopper circuit 16 such as a noise filter circuit (not shown) and a rectifying element 22 connected to the noise filter circuit and an electrolytic capacitor that is a smoothing element that smoothes the output from the rectifying element 22. And a smoothing capacitor C1.

  The noise filter circuit is a known line filter configured by, for example, a fuse, a capacitor, a common mode choke, and a capacitor.

  The rectifying element 22 is a full-wave rectifying element such as a bridge diode connected to the output side of the noise filter circuit.

  The step-up chopper circuit 16 is a current critical power factor correction circuit that converts the output voltage from the power supply unit 15 into a desired voltage, and converts the AC power of an AC sine wave or AC rectangular wave into DC. In the boost chopper circuit 16, a series circuit of an inductor L1 that is a boosting transformer (chopper choke) and a reverse blocking diode D1 is connected to the power supply unit 15, and the inductor L1 and the diode D1 are connected to each other. A switching element Q1 (for boosting chopping) such as a P-channel type MOSFET is connected to the connection point with the anode, and a smoothing capacitor C2 that is an output capacitor such as an electrolytic capacitor is connected to the cathode side of the diode D1 that is the output side. In addition, a driver 24 (for a boost chopper) is provided as control means for switching control of the switching element Q1.

  In the inductor L1, the primary winding L1a is connected between the output side of the rectifying element 22 and the anode of the diode D1, and the secondary winding (auxiliary winding) L1b is connected to the driver 24.

  In the switching element Q1, the drain terminal is connected to the connection point between the inductor L1 (primary winding L1a) and the anode of the diode D1, and the source terminal on the output side is connected to the ground potential via the current detection resistor R1. It is connected to the. Further, the gate terminal which is the control terminal of the switching element Q1 is connected to the driver 24.

  The driver 24 includes an input voltage detection unit 25 that detects the input voltage Vin of the boost chopper circuit 16, an output voltage detection unit 26 that detects the output voltage Vout of the boost chopper circuit 16, and a current (source current) that flows through the switching element Q1. It is electrically connected to a current detector 27 that detects I. The driver 24 detects the input voltage Vin of the boost chopper circuit 16 detected by the input voltage detection unit 25, the output voltage Vout detected by the output voltage detection unit 26, the current flowing through the inductor L1, and the current detection unit 27. Is a control IC for turning on / off the switching element Q1 at a predetermined switching frequency based on the current I and controlling the on width (duty) of the switching element Q1 (setting the on-time and off-time), and at least the switching element When the current I flowing through Q1 increases (decreases), the ON width of the switching element Q1 increases (decreases). That is, the driver 24 switches the switching element Q1 according to the increase / decrease of the current I.

  The input voltage detection unit 25 is connected between the power supply unit 15 (rectifier element 22) and the boost chopper circuit 16 (smoothing capacitor C1). The input voltage detection unit 25 is configured by connecting a plurality of (input voltage) detection resistors R2 and R3 in series, and corresponds to the input voltage Vin of the boost chopper circuit 16 by dividing the detection resistors R2 and R3 (proportional ) To detect the input voltage Vin of the boost chopper circuit 16 (the output voltage of the power supply unit 15). A connection point (middle point) between the detection resistors R2 and R3 is connected to the driver 24.

  The output voltage detection unit 26 is connected between the step-up chopper circuit 16 (smoothing capacitor C2) and the step-down chopper circuit 17. The output voltage detection unit 26 is configured by connecting a plurality of (output voltage) detection resistors R4 and R5 in series, and corresponds to the output voltage Vout of the boost chopper circuit 16 by dividing the detection resistors R4 and R5 (proportional) ) To detect the output voltage Vout of the step-up chopper circuit 16 (the input voltage of the step-down chopper circuit 17). The connection point (midpoint) of the detection resistors R4 and R5 is connected to the driver 24.

  In addition to the resistor R1, the current detection unit 27 includes a resistor R6 that is a detection element connected between a connection point between the resistor R1 and the source terminal of the switching element Q1 and the driver 24, and a capacitor that grounds the resistor R6. C3 is provided, and a current proportional to the current I flowing through the switching element Q1 is detected as a voltage. The current detector 27 is connected to superimposing means 31 for superimposing a predetermined direct current on the current detected by the current detector 27.

  The superimposing means 31 includes two (one and the other) switching elements Q2 and Q3. The switching element Q2 is, for example, an NPN bipolar transistor, and the switching element Q3 is, for example, a PNP bipolar transistor. The emitter terminal of the switching element Q2 is grounded, and the collector terminal is a base terminal that is the control terminal of the switching element Q3. The base terminal, which is a control terminal, is connected via a resistor R7, and is connected to the microcomputer 33, which is a signal output means. Therefore, on / off of the switching element Q2 is controlled by the microcomputer 33, and on / off of the switching element Q3 is controlled by the switching element Q2. The emitter terminal of the switching element Q3 is connected to a predetermined voltage source VD via a pull-up resistor R8, and the collector terminal is connected to a connection point between the resistor R6 and the driver 24.

  The microcomputer 33 is connected to the connection point (midpoint) of the dimming signal receiving means 35 and the detection resistors R2 and R3 of the input voltage detection unit 25, and is grounded.

  Here, the dimming signal receiving means 35 includes a rectifying element 38 connected to a signal source 37 to which a dimming signal which is a PWM signal is input manually, for example, and a photocoupler 39 connected to the rectifying element 38. And a pull-up resistor R9 connected to the photocoupler 39. The rectifier element 38 is a full-wave rectifier element such as a bridge diode that rectifies a dimming signal that is a PWM signal and supplies the rectified signal to the photocoupler 39. The photocoupler 39 includes a photodiode PD and a phototransistor PT, and the photodiode PD connected to the rectifying element 38 is turned on in response to the dimming signal rectified by the rectifying element 38. The phototransistor PT is a switching element that is turned on and off in accordance with the light emission of the photodiode PD, the emitter terminal is grounded, and the collector terminal is connected to a predetermined voltage source V via the pull-up resistor R9. Together with the microcomputer 33. Therefore, the dimming signal receiving means 35 turns on the phototransistor PT when the dimming signal is at a high level and outputs a low level signal, and turns off the phototransistor PT when the dimming signal is at a low level. A level signal is output.

  Then, the microcomputer 33 determines that the dimming signal received from the signal source 37 by the dimming signal receiving means 35 is equal to or lower than a predetermined dimming level set in advance, that is, the light source 12 is set to a predetermined dimming depth or higher. When a dimming signal instructing dimming is received by the dimming signal receiving means 35 and a signal corresponding to the dimming signal is input from the dimming signal receiving means 35 (photocoupler 39), the input voltage This switching is performed by outputting a high-level signal to the base terminal of the switching element Q2 when the voltage proportional to the input voltage Vin detected by the detection unit 25 is at least a predetermined voltage or higher. The element Q2 is turned on.

  In the step-down chopper circuit 17, a series circuit of a switching element Q4 (for step-down chopping) such as a P-channel MOSFET and a diode D2 is connected to both ends of the smoothing capacitor C2. Further, the inductor L2 is connected to the cathode of the diode D2, the anode of the diode D2 is grounded, and the light source 12 is connected in parallel to the diode D2. A gate terminal which is a control terminal of the switching element Q4 is connected to a driver 41 (for a step-down chopper) which is a control IC as a step-down control means for setting an ON time and an OFF time of the switching element Q4. The driver 41 turns on and off the switching element Q4 at a predetermined switching frequency, and controls the ON width (duty) of the switching element Q4 according to the dimming signal received by, for example, the dimming signal receiving unit 35 (on time and By setting the off time), the light source 12 is controlled to flow a predetermined constant current.

  Next, the operation of the one embodiment will be described.

  When the power supply device 11 is activated, the commercial AC power source e is rectified by the rectifying element 22, smoothed by the smoothing capacitor C1, and input to the step-up chopper circuit 16. In the step-up chopper circuit 16, the switching element Q1 is switched by the driver 24, the power supply voltage rectified and smoothed by the rectifying element 22 and the smoothing capacitor C1 is boosted to a predetermined power supply voltage, and the voltage smoothed by the smoothing capacitor C2 is stepped down. Supply to the chopper circuit 17. In the step-down chopper circuit 17, the switching element Q4 is switched by the driver 41, the output voltage Vout of the step-up chopper circuit 16 is stepped down to a predetermined voltage, and supplied to the light source 12, whereby the light source 12 is turned on.

  The driver 24 detects the timing at which the voltage proportional to the induced voltage of the primary winding L1a induced in the secondary winding L1b of the inductor L1 starts to drop due to the discharge of all the energy stored in the inductor L1, thereby When the critical point of the current I flowing through L1 is detected by the current detection unit 27 and when it is detected that the current I of the inductor L1 has become zero, the switching element Q1 is turned on, whereby the output voltage of the boost chopper circuit 16 Feedback control is performed so that Vout approaches the target value.

  Further, in the driver 41, for example, according to the dimming signal received from the signal source 37 by the dimming signal receiving means 35, the on-time and off-time (duty) of the switching element Q4 is set to flow to the light source 12. The light source 12 is dimmed by feedback control so that the constant current approaches the target value.

  Here, when the power supply voltage (input voltage Vin) is high and the dimming level of the light source 12 is lower than a predetermined level (the dimming depth is higher than a predetermined level), or when the load is light, the current I flowing through the switching element Q1 decreases to a predetermined value or lower. In other words, the switching range of the switching element Q1 by the driver 24 becomes irregular due to the control range in which the switching element Q1 needs to be equal to or smaller than the minimum on-width, and the output voltage Vout of the step-up chopper circuit 16 increases undesirably or fluctuate. Therefore, in this embodiment, the voltage proportional to the input voltage Vin of the boost chopper circuit 16 detected by the input voltage detection unit 25 is equal to or higher than a predetermined voltage (the input voltage Vin of the boost chopper circuit 16 is set in advance). And a high level signal is output from the microcomputer 33 to the base terminal of the switching element Q2 of the superimposing means 31, the switching element Q2 is turned on, and the switching element Q2 is turned on. The switching element Q3 is turned on by this, and the DC voltage from the voltage source VD is applied to the connection point between the current detection unit 27 and the driver 24 (resistor R6), that is, the current detected by the current detection unit 27 by the superimposing means 31 (switching element Since the DC offset current is superimposed on the current I flowing in Q1 (current proportional to the current I)), the driver 24 supplied with this current causes the switching element Q1 to be irregular. Oscillation is suppressed, and switching control is performed regularly or substantially regularly with a minimum on-width in a wider power supply phase, so that the output voltage Vout of the boost chopper circuit 16 can be suppressed from undesirably rising or fluctuating.

  Similarly, when the dimming level of the light source 12 is equal to or lower than the predetermined level (the dimming depth is equal to or higher than the predetermined level), that is, the dimming signal for dimming the light source 12 is a signal that indicates the dimming level or lower. Since the output voltage Vout of the chopper circuit 16 easily rises or fluctuates undesirably, when this dimming signal is received by the dimming signal receiving means 35, a high level signal is sent from the microcomputer 33 to the switching element Q2 of the superimposing means 31. The switching element Q2 is turned on when the switching element Q2 is turned on, and the switching element Q3 is turned on when the switching element Q2 is turned on, so that the DC voltage from the voltage source VD is applied between the current detection unit 27 and the driver 24 (resistor R6). The DC offset current is superimposed on the current applied to the connection point, that is, the current detected by the current detector 27 by the superimposing means 31 (current I flowing through the switching element Q1 (current proportional to the current I)). The driver 24 to which the voltage is supplied suppresses irregular oscillation of the switching element Q1 and performs switching control regularly or substantially regularly with the minimum on-width in a wider power supply phase, so that the output voltage Vout of the boost chopper circuit 16 is undesirably The rise or fluctuation can be suppressed.

  When the output voltage Vout is controlled to a predetermined output voltage, a low-level signal is output from the microcomputer 33 to the base terminal of the switching element Q2, the switching elements Q2 and Q3 are turned off, and superimposing means 31 stops superimposing the offset current Is done.

  In the above embodiment, the microcomputer 33 is proportional to the input voltage Vin of the boost chopper circuit 16 detected by the input voltage detection unit 25, but is equal to or higher than a predetermined voltage, and the dimming signal receiving unit 35. When the dimming signal received by is a signal that indicates the dimming level or less, a high level signal may be output from the microcomputer 33 to the base terminal of the switching element Q2 of the superimposing means 31.

  Further, the step-up chopper circuit 16 may be a current continuous type or a current discontinuous type other than the current critical type.

  Furthermore, when the power supply device 11 supports a plurality of light sources 12 having different load voltages, it is possible to more effectively suppress the output voltage Vout of the boost chopper circuit 16 from being undesirably increased or fluctuated.

  Although one embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10 Lighting equipment
11 Power supply
12 Light source
16 Boost chopper circuit
17 Step-down chopper circuit as step-down means
24 Driver as control means
27 Current detector
31 Superimposing means
33 Microcomputer I Current as signal output means
Q1 Switching element

Claims (2)

A step-up chopper circuit that includes a switching element and a control unit that switches the switching element in accordance with an increase / decrease in current flowing through the switching element, and that boosts an input voltage from an external power source by switching the switching element;
Step-down means for stepping down the voltage stepped up by the step-up chopper circuit and supplying it to the light source;
A current detector for detecting a current proportional to the current flowing through the switching element of the step-up chopper circuit and supplying the detected current to the control means;
At least one of when the voltage proportional to the input voltage of the step-up chopper circuit becomes equal to or higher than a predetermined voltage value set in advance and when the dimming signal of the light source becomes lower than a predetermined dimming level set in advance. Signal output means for outputting a signal at any time;
Superimposing means for superimposing an offset current on the current supplied to the control means detected by the current detector when a signal is output from the signal output means;
A power supply device comprising: With a light source;
The power supply device according to claim 1 for supplying power to the light source;
An illumination device comprising:

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