JPH01294398A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To permit an accurate starting operation of a lamp as load voltage, especially referring to no-load secondary voltage, is not lowered even in a light adjusting state by adjusting feedback signals corresponding to load current, depending on light adjusting signals. CONSTITUTION:Signals corresponding to load current flowing through an electric discharge lamp 17 are detected by an amperometric transducer, and applied to one of the input of a calculating machine 19 via a variable impedance element 23. To the other input of the calculating machine 19, signals corresponding to load voltage in an inverter circuit is inputted from a secondary coil N4 of an inverter transducer 11. The calculating machine 19 adds these signals to input the same into a drive control circuit 21 as control signals, on the basis of which the switching frequencies of switching elements 3, 5 are provided with variation and others to adjust output in the inverter circuit. Thus, the output in the inverter circuit is controlled so that the summation of the load current and the load voltage can be constant, and a lighting device having a constant-power output characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a discharge lamp lighting device, and in particular to a discharge lamp lighting device that provides constant brightness despite changes in lamp temperature and that can be started accurately even in a dimmed state. The present invention relates to a discharge lamp lighting device capable of

(Prior Art) Conventionally, in a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp, signals corresponding to the load current and load voltage supplied to the discharge lamp from a high frequency inverter are detected, and these signals are It has been considered to perform feedback control of an inverter circuit using a control signal obtained by addition.

In such a discharge lamp lighting device, the output power is constant, so almost constant brightness can be obtained despite changes in lamp temperature. The desired brightness could be ensured even when the height was high. It has also been considered to control the dimming of the lamp by adjusting the magnitude or level of the control signal using an external dimming signal.

(Problem to be Solved by the Invention) However, in the above-mentioned discharge lamp lighting device, the magnitude of the control signal obtained by adding the signal corresponding to the load current and the signal corresponding to the load voltage is determined by the dimming signal. For example, as shown in Figure 6, the load curve of the device in the dimming state moves parallel to the load curve in the full light state, and the load voltage when the load current is 0, that is, the no-load 2 The next voltage V also decreases to 20 as the light is dimmed.

For this reason, there is an inconvenience that it becomes difficult or uncertain to start the discharge lamp during dimming. Furthermore, in the above-mentioned discharge lamp lighting device, the load curve and the lamp's V-1 curve become nearly parallel when dimming, making the operating point unstable and causing the lamp to sometimes go out. .

In view of the above-mentioned problems in the discharge lamp lighting device, an object of the present invention is to provide a discharge lamp lighting device that can maintain a substantially constant illuminance despite changes in lamp temperature, which can accurately start the lamp even during dimming. The object of the present invention is to stabilize the operation by ensuring that the operation is carried out properly and preventing failures such as fading.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the discharge lamp lighting device according to the present invention includes a high-frequency inverter circuit that generates high-frequency power for lighting the discharge lamp, and a load circuit from the high-frequency inverter circuit. A voltage detecting means and a current detecting means for respectively detecting the supplied voltage and current, an output adjusting means for changing the magnitude of the output of the current detecting means in accordance with a dimming signal, an output of the output adjusting means and the above. An adder circuit that adds the output of the voltage detection means and a control circuit that performs feedback control of the output of the high frequency inverter circuit based on the output of the adder circuit is used.

Further, in the discharge lamp lighting device according to another aspect of the present invention, a chopper circuit is used as the output adjustment means,
The operation of this chopper circuit is configured to be controlled by an external dimming signal.

(Function) In the above configuration, a control signal is generated by adding a signal corresponding to the load current and a signal corresponding to the load voltage, and the output of the high frequency inverter circuit is feedback-controlled by this control signal. Therefore, the output of the high frequency inverter circuit corresponds to the sum of the magnitude of the load current and the magnitude of the load voltage, and has approximately constant power characteristics such as when the load voltage decreases, the load current increases. It turns out.

Furthermore, since the output of the current detection means is adjusted by the output adjustment means during dimming, the load voltage does not decrease due to dimming. Therefore, the no-load secondary voltage does not drop even during dimming, and it is possible to accurately start the discharge lamp with dimming.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a discharge lamp lighting device according to an embodiment of the present invention. The device shown in the figure includes a rectifying and smoothing circuit 1 for converting AC power source AC into DC, a high frequency inverter circuit composed of switching transistors 3, 5, a capacitor 7.9, an inverter transformer 11, a resonance capacitor 13, etc. It includes a current transformer 15 that detects the current flowing through the lamp 17, an adder 19, a drive control circuit 21, and a variable impedance element 23 that adjusts the output of the current transformer 15 in accordance with a dimming signal.

The variable impedance element 23 may be a variable resistor whose impedance can be manually adjusted, or may be a transistor or other element whose internal impedance changes in response to a dimming signal.

In the device shown in Figure 1, an AC power supply A such as a commercial power supply is used.
C is rectified and smoothed in a rectifying and smoothing circuit 1 to generate a DC power source. Then, the switching transistors 3 and 5 are turned on and off alternately by the switching pulses supplied from the drive control circuit 21, whereby a high frequency current flows through the primary coil N1 of the inverter transformer 11. As a result, as is well known, the second part of the inverter transformer 11
A high frequency voltage is generated across the next coil N2, and the discharge lamp 17 is lit.

In such an operation, a signal corresponding to the load current flowing through the discharge lamp 17 is detected by the current transformer 15 and applied to one input of the adder 19 via the variable impedance element 23. Further, the other input of the adder 19 receives a signal corresponding to the load voltage of the inverter circuit from the secondary coil N4 of the inverter transformer 11. The adder 19 adds these signals and inputs the result to the drive control circuit 21 as a control signal. The drive control circuit 21 adjusts the output of the inverter circuit by changing the switching frequency of the switching element 3.5 based on this control signal. In this way, in the device shown in FIG. 1, the output of the inverter circuit is controlled so that the sum of the load current and the load voltage is constant, and a lighting device having pseudo-constant power output characteristics is realized.

Furthermore, in the device shown in FIG. 1, the impedance of the variable impedance element 23 can be adjusted by the dimming signal. Therefore, it is possible to change the magnitude of the output of the current transformer 15 according to the dimming signal,
The discharge lamp 17 can be dimmed. In this case, the second
As shown by the dotted line in the figure, the output voltage v2o when the no-load voltage, that is, the current is 0, does not decrease even in the dimming state.

Therefore, it becomes possible to start the discharge lamp 17 in a dimmed state, and starting is performed accurately regardless of the dimming level.

Further, even in the dimming state, since the angle at which the load curve intersects with the V-1 curve of the lamp is large, a stable lighting state is maintained, and inconveniences such as so-called turning off are eliminated.

FIG. 3 shows a schematic configuration of a discharge lamp lighting device according to another embodiment of the present invention. In the device shown in the figure, a chopper circuit constituted by a switch 25 such as an electronic switch and resistors 27, 29, 31, etc. is used in place of the variable impedance element 23 in the device shown in FIG. The other parts are the same as the apparatus of FIG. 1 and are designated by the same reference numerals and symbols.

In the device shown in FIG. 3, similarly to the device shown in FIG. 1, a high frequency voltage is generated in the secondary coil of the inverter transformer 11 by turning on and off the switching element 3.5, and the discharge lamp 17 is lit. In this case, if the switch 25 is in the OFF state, the output signal of the current transformer 15 is input to the adder 19 after being considerably attenuated by the resistor 29 and the like. Therefore,
The high frequency inverter circuit reaches its maximum output and the discharge lamp 17 is lit in full light. On the other hand, a dimming signal such as a PWM (pulse width modulation) signal causes the switch 2 to
By turning 5 on and off to perform chopper operation,
When the output signal of the current transformer 15 is in an all-optical state, it is input to the adder 19 without being significantly attenuated. Therefore, the output of the inverter circuit becomes smaller and the discharge lamp 17 is dimmed.

FIG. 4 shows a detailed circuit configuration around the chopper circuit and adder 19 in the device shown in FIG.

That is, as shown in FIG.
9.31, resistor 33 through a circuit including capacitor 39
．． 35 and one input of an adder having a variable resistor 37, ie one end of resistor 33. Further, a signal corresponding to the load voltage output from the secondary coil N4 of the inverter transformer 11 is passed through the diode bridge 45 and the smoothing capacitor 41 to the other end of the adder, that is, the resistor 35.
is applied to one end of .

In such a circuit configuration, for example, P
A WM signal is applied to the switch 25, and the switch 25 is turned on and off by the dimming signal.

Therefore, a signal whose magnitude changes depending on the duty cycle of the dimming signal is generated at both ends of the capacitor 39. Thereby, the discharge lamp 17 is dimmed in accordance with changes in the duty cycle of the dimming signal. Note that it is convenient to set the frequency of the dimming signal for operating the chopper circuit switch 25 to, for example, 15 KHz or higher, since it is possible to prevent the generation of humming noise and the like. In addition, by using a chopper circuit, it is no longer affected by level fluctuations or other effects of the dimming signal.
Therefore, it is possible to obtain a constant dimming state regardless of where the lighting equipment is installed.

FIG. 5 shows the configuration of a discharge lamp lighting device according to another embodiment of the present invention using a specific circuit. The device shown in this figure also uses a chopper circuit to perform dimming. That is, the circuit shown in FIG. 5 includes a rectifying and smoothing circuit composed of a diode bridge REI that rectifies an AC power supply, smoothing capacitors C2 and C3, and respective diodes DI and D2°C3, switching transistors Ql and Q2, and capacitors C6 and C3.
7, inverter transformer IVT and resonance capacitor C9
A high frequency inverter circuit consisting of a current transformer CT inserted in the load circuit, a diode bridge RE2. RE3, photocoupler PTI and resistor R11,R
12, an output adjustment circuit composed of RIO, a capacitor C11, etc., a voltage detection circuit composed of a diode bridge RE4 connected to one secondary coil N4 of the inverter transformer IVT, a capacitor C12, etc., and a diode D8. D9, an adder circuit composed of resistors R17, R18, etc., and a transistor Q4. Q5.0
6, a control integrated circuit HIC, a driver transformer DT, and the like.

In the circuit of FIG. 5, the alternating current power supply AC is rectified by the diode bridge REI, and the smoothing capacitor C2
, C3, diodes DI, and C2°C3, a DC power supply with less ripple is generated. Then, each transistor Ql is output from the secondary coil output terminals a, a', and b' of the driver transformer DT of the drive control circuit.

These transistors Ql and Q2 are alternately turned on and off by a switching signal applied to the gate of Q2. As a result, a high frequency current flows through the primary coil N1 of the inverter transformer IVT, and each secondary coil N2. N3.
..., a high frequency voltage is generated at N6. These high-frequency voltages heat the electrodes of the discharge lamps LPi and LP2 and turn them on.

Further, a signal corresponding to the load current is detected by the current transformer CT connected between the secondary coil N2 of the inverter transformer IVT and the electrode of the discharge lamp LPI, and this signal is applied to the chopper circuit via the diode bridge RE3. . The chopper circuit operates in the same manner as described above using a dimming signal such as a PWM signal, and its output is connected to a variable resistor V.
The signal is applied to the adder via a circuit including RI and the like. A signal obtained by rectifying and smoothing a signal corresponding to the load voltage detected from the other secondary coil N4 of the inverter transformer IVT by a diode bridge RE4, a capacitor C12, etc. is applied to the other input of this adder. As a result, a signal corresponding to the sum of the load current and the load voltage is transmitted to the transistor Q4. The signal is applied to the base of the transistor Q6 via a differential amplifier composed of Q5 and the like, and the impedance of the transistor Q6 changes, thereby changing the oscillation frequency of the oscillator O8C built in the control integrated circuit IC. This oscillator O8
A switching transistor inside the integrated circuit IC is turned on and off by a signal generated based on the output of the integrated circuit IC, and a switching current is supplied to the driver transformer DT. That is, in the circuit of FIG. 5, the output of the high frequency inverter circuit is adjusted so that the sum of the signal corresponding to the load current and the signal corresponding to the load voltage is constant.

In the above-described operation, a PWM signal, for example, is used as the dimming signal, and the larger the duty cycle of the dimming signal, the lower the illuminance, for example, and when the duty cycle is 0, a full light state is achieved.

(Effects of the Invention) As described above, according to the present invention, in a discharge lamp lighting device that controls the output characteristics to be constant power, the feedback signal corresponding to the load current is adjusted in accordance with the dimming signal. Therefore, the load voltage does not drop even in the dimming state, and in particular, the no-load secondary voltage does not drop, making it possible to accurately start the lamp even in the dimming state.

Further, the lighting state of the discharge lamp is stable even when dimming, and the lamp does not turn off or go out even when dimming is performed especially when the lamp temperature is low. In addition, since the discharge lamp lighting device according to the present invention has a constant power output characteristic, it is particularly suitable for high output type, for example, one that obtains 150% of the light output of normal lighting. Even when the lamp temperature increases when a lamp is mounted, the illuminance does not decrease and the desired brightness can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the configuration of a discharge lamp lighting device according to an embodiment of the present invention, FIG. 2 is a graph showing the output characteristics of the device in FIG. 1, and FIG. 3 is a graph showing the output characteristics of the device in FIG. A block circuit diagram showing the configuration of a discharge lamp lighting device according to another embodiment; FIG. 4 is an electric circuit diagram showing details of a part of the circuit in FIG. 3; FIG. 5 is a block circuit diagram showing the configuration of a discharge lamp lighting device according to another embodiment; FIG. An electric circuit diagram showing the circuit configuration of the discharge lamp lighting device according to the example, and FIG. 6 are graphs showing the output characteristics of the conventional discharge lamp lighting device. 1: Rectifier and smoothing circuit, 3.5 Niswitching transistor, 7.9: Capacitor, 11: Inverter transformer, 13: Resonant capacitor, 15: Current transformer, 17: Discharge lamp, 19: Adder,
21: Drive control circuit, 23: Variable impedance element, 25: Switch, 27.29, 31, 33, 35: Resistor, 37: Variable resistor, 39.41: Capacitor, 43.45 + diode bridge, Ql, Q2 ．． ..., Q6:) transistor, REI
, RE2. RE3. R4: Diode bridge, IVT: Inverter transformer, C9: Resonant capacitor, CT two-current transformer, LPI, LP2: Discharge lamp, PTI: Photocoupler, IC = Control integrated circuit, DT: Driver transformer.

Claims (1)

[Scope of Claims] 1. A high-frequency inverter circuit for generating high-frequency power for lighting a discharge lamp, voltage detection means for detecting voltage supplied from the high-frequency inverter circuit to a load circuit, and from the high-frequency inverter circuit. A current detection means for detecting the current supplied to the load circuit, an output adjustment means for changing the magnitude of the output of the current detection means in accordance with a dimming signal, and an output of the output adjustment means and the voltage detection means. A discharge lamp lighting device comprising: an adding circuit for adding outputs; and a control circuit for feedback controlling the output of the high frequency inverter circuit based on the output of the adding circuit. 2. A high-frequency inverter circuit for generating high-frequency power for lighting a discharge lamp, voltage detection means for detecting the voltage supplied from the high-frequency inverter circuit to a load circuit, and voltage detection means for detecting the voltage supplied from the high-frequency inverter circuit to the load circuit. A current detecting means for detecting current, a chopper circuit connected to the output of the current detecting means and changing the magnitude of the output of the current detecting means in accordance with a dimming signal, and an output of the chopper circuit and the voltage detecting means. 1. A discharge lamp lighting device comprising: an adder circuit for adding the outputs of the adder circuit; and a control circuit for feedback-controlling the output of the high-frequency inverter circuit based on the output of the adder circuit.