JPH05182783A - Discharge lamp lighting device and luminaire - Google Patents

Abstract

PURPOSE:To prevent excess current from flowing into discharge lamps even when not all the discharge lamps are lighted. CONSTITUTION:When a plurality of discharge lamps 56 through 59 is lighted by high frequency voltage obtained from an inverter 3 through switching DC voltage, the constant electric power control of each discharge lamp is executed based on controlled voltage V1 generated by a controlled voltage generating circuit 7 which is actuated on the basis of the detected voltage of lamp output by means of a resistor 4. Controlled voltage V1 is compared with the controlled terminal voltage V2 of a switching control circuit 33. When V1 is greater than V2, means 93 and 94 are provided, which set the controlled current I of the switching control circuit 33 to meet the frequency used when the whole lamps are lighted. Even if thinned-out lighting is done with controlled current set in such a way that V1 is roughly equal to V2, since switching frequency is restricted by the frequency used when the whole lamps are lighted, excess current is prevented from flowing to the remaining discharge lamps. If the thinned-out lighting is done at the time of dimming, lamp output equivalent to the reduced discharge lamps is applied to the remaining discharge lamps, lamp current however, is less than that when the whole lamps are lighted, because the switching frequency is restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device,
In particular, the present invention relates to a discharge lamp lighting device capable of controlling the discharge lamp output by constant power control when a plurality of discharge lamps are lit by using an inverter, and a lighting fixture equipped with the discharge lamp lighting device.

[0002]

2. Description of the Related Art In recent years, many discharge lamp lighting circuits use high-frequency inverters.

This is because the high-frequency lighting can improve the luminous efficiency of the lamp, the flicker of the lamp output can be reduced, the lamp starting time can be shortened, and when the multiple lamps are lit, the whole lamp is not lit. The reason is that the dimming and lighting for controlling the light output of is relatively easy, and the lighting circuit can be made smaller and lighter.

Conventionally, when multiple discharge lamps are lit using a transistor inverter, the lamp output is controlled to a constant power by controlling the frequency of an oscillator that switches the transistors. Specifically, the current flowing in the transistor inverter is detected (that is,
The constant power of the lamp output is controlled by detecting the change in the lamp output) and controlling the switching frequency. When the lamp output decreases, the switching frequency is lowered to increase the lamp output, and when the lamp output rises, the switching frequency is increased to decrease the lamp output (having a series resonance circuit,
When making differential in the lag area).

By the way, in the above discharge lamp lighting device, when multiple lights are turned on, thinning out can be considered when replacing the lamp. In this case, in the above-mentioned constant power control technique, when the thinned lighting is performed, the transistor inverter operates to maintain constant power (that is, to maintain the current flowing through the inverter), so that each of the thinned discharge lamps remains There was a problem that overcurrent would flow.

[0006]

As described above, in the conventional discharge lamp lighting device, in the case of multiple lighting, when the thinning lighting is performed, the inverter tries to maintain constant power, so that an overcurrent flows in the discharge lamp. There was a problem.

Therefore, in view of the above problems, the present invention provides a discharge lamp lighting device and an illuminating device equipped with the discharge lamp lighting device, in which overcurrent does not flow to the discharge lamp even when thinning lighting is performed in the case of multiple lighting. It is intended to be provided.

[0008]

A discharge lamp lighting device according to the present invention includes a switching control means capable of changing an output frequency, and an inverter for switching a DC voltage at an output of the switching control means to convert it into a high frequency voltage. A discharge lamp provided in parallel with each other, a plurality of ballast coils and a starting capacitor connected to each discharge lamp, and the discharge lamp is driven by the high frequency voltage from the inverter. An electric light circuit, a detection means for detecting a combined value of lamp currents flowing through the plurality of discharge lamps, a control voltage generation means for generating a control voltage based on a detection signal from the detection means, and a switching control means for the inverter. Of the control voltage generating circuit, including an all-optical frequency setting means for setting the output frequency of the inverter to a frequency corresponding to the all-optical frequency of the inverter. If the output voltage is higher than a preset predetermined value, the output frequency is set to a value corresponding to the all-light frequency of the inverter, and if the output voltage of the control voltage generating circuit is lower than the predetermined value, this output And a control current generating means for controlling the output frequency of the switching control means so that the voltage becomes constant.

[0009]

According to the present invention, when a plurality of discharge lamps are fully illuminated, even if the discharge lamps are thinned out, the remaining discharge lamps operate at the same frequency and an overcurrent can be prevented from flowing. Also,
When dimming the discharge lamp during dimming lighting, the lamp output (wattage) of the discharged discharge lamp is added to the remaining discharge lamps, but it does not flow above the maximum lamp current (lamp current at full light). ..

[0010]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention.

In this figure, reference numeral 1 is a commercial AC power supply, and the output of this AC power supply 1 is rectified and smoothed by a voltage doubler rectifier circuit 2 and supplied to a transistor inverter 3. The voltage doubler rectifier circuit 2 is for obtaining a voltage doubler rectified output obtained by rectifying a half cycle of the positive side of the AC and a half cycle of the negative side of the AC, and a diode 21 is provided at one end of the AC power source 1. Is connected in the forward direction, while the diode 22 is connected in the reverse direction, and the capacitor 23 is connected between the cathode of the diode 21 and the anode of the diode 22.
24 are connected in series, and the other end of the AC power supply 1 is connected to the capacitor 2
It is connected to the connection points of 3, 24. Also,
The transistor inverter 3 connects the drain and source paths of two field effect transistors (hereinafter abbreviated as FET) 31 and 32 in series, and applies the output voltage of the voltage doubler rectifier circuit 3 to both ends of the series circuit. , FET31,3
The switching control circuit 33 applies switching pulses of opposite phases to the respective gates of the two, and the rectified output from the voltage doubler rectifier circuit 2 is supplied to two FEs.
By alternately turning on T31 and T32, a high frequency output corresponding to the switching frequency is obtained. As the switching control circuit 33, for example, a control IC TA76494 manufactured by Texas Instruments Incorporated is used. The TA76494 is an oscillator whose oscillation frequency changes in proportion to the magnitude of the current I flowing out from the control terminal 34. A current detecting resistor 4 as a lamp output detecting means is connected between the source of the FET 32 and the negative terminal of the voltage doubler rectifying circuit 2.

A discharge lamp circuit 5 serving as a load is connected between the connection point of the FETs 31 and 32 and one end of the detection resistor 4 (the negative terminal of the voltage doubler rectifier circuit 2). In this discharge lamp circuit 5, a plurality (four in the figure) of ballast coils 52 to 55 are connected in parallel to a connection point of the FETs 31 and 32 via a capacitor 51.
The other ends of the discharge lamps 56 to 59 are connected to the other ends of the discharge lamps 56 to 59, and the other ends of the filaments of the discharge lamps 56 to 59 are connected to one end of the resistor 4 (the voltage doubler rectifier circuit 2).
Of the discharge lamps 56 to 59, and the starting capacitors 60 to 63 are connected between the filaments at both ends of the discharge lamps 56 to 59.

The detection voltage of the current detecting resistor 4 is supplied to a control voltage generating circuit 7 using two operational amplifiers.
The control voltage generating circuit 7 passes the voltage of the detection resistor 4 through a smoothing circuit including a resistor 71 and a capacitor 72,
It is input to the non-inverting input terminal of the non-inverting amplifier circuit including the operational amplifier 73 and the resistors 74 and 75, and the non-inverting output is input to the resistor 7
Take it out at both ends of 6, and add an operational amplifier 77 and a resistor 7.
It is configured such that it is input to the inverting input terminal of the inverting amplifier circuit composed of 8, 79 and the variable reference voltage source 80, and its inverting output V1 is supplied to the control current generating circuit 9 of the next stage. The control current generating circuit 9 connects the output terminal of the operational amplifier 77 to the resistor 91.
To the cathode of the diode 92, the anode of the diode 92 to the oscillation frequency control terminal 34 of the switching control circuit 33, and the control terminal 34 to the reference potential via the series circuit of the resistor 93 and the variable resistor 94. Connected to a point.

Next, the operation of the above device will be described. Here, the operation in the lighting state after the discharge lamp is started will be described.

The output of the commercial AC power supply 1 is the voltage doubler rectifier circuit 2
Is rectified by the transistor inverter 3
Are supplied to both ends of the FETs 31 and 32. In the transistor inverter 3, the FETs 31 and 32 are alternately turned on and off at a frequency controlled by the switching control circuit 33, and the FET 31 is turned on and the FET 32 is turned on.
When is off, only while FET31 is on,
A current is supplied from one end of the rectifier circuit 2 to the discharge lamp circuit 5 through the FET 31. The discharge lamp circuit 5 includes the FET 31
When is turned on, a current is shunted through the capacitor 51 to the ballast coils 52 to 55 and the discharge lamps 56 to 59, and then merges again to flow into the other end of the rectifier circuit 2. Next, when the FET 31 is turned off and the FET 32 is turned on, the energy stored in the ballast coils 52 to 55 flows through the capacitor 51, the FET 32, the current detecting resistor 4, and the discharge lamps 56 to 59. When the FET 31 is turned on and the FET 32 is turned off again, the ballast coils 52 through the rectifier circuit 2 through the FET 31.
Current is supplied to 55 and the discharge lamps 56 to 59. The voltage detected by the current detecting resistor 4 is the discharge lamps 56-5.
It is proportional to the sum of each lamp output of 9 (the wattage of each discharge lamp at full light). This detection voltage is supplied to the control voltage generation circuit 7. The control voltage generation circuit 7 smoothes the detected voltage, non-inverts it, then inverts it, and outputs it. The output voltage V1 is small when the lamp output detected by the resistor 4 is large, and is large when the lamp output is small. Here, the voltage E of the variable reference voltage source 80 connected to the non-inverting input terminal of the inverting amplifier circuit of the operational amplifier 77 is set to be larger than the input voltage supplied to the inverting input terminal. Yes, the output voltage V1 is changed by changing the set voltage E, and the discharge lamp 56
The dimming can be performed by changing the combined current of the lamps of ~ 59.

On the other hand, the frequency control terminal 34 of the switching control circuit 33 is connected to a reference potential point via a series circuit of a resistance 93 and a variable resistance 94, and a constant voltage V2 is always output to the control terminal 34. It has become so.
Here, when the diode 92 is off, the current I flowing out from the control terminal 34 becomes equal to the current I1 flowing in the series circuit of the resistor 93 and the variable resistor 94, so that I = I1 = V2 / R1. R1 is a combined resistance value of the resistance 93 and the variable resistance 94. Therefore, by changing the variable resistor 94, the outflow current I can be changed by changing the resistor R1.
Further, since the outflow current I of the control terminal 34 and the oscillation frequency f of the switching control circuit 33 have a linear relationship, if the outflow current I is changed by changing the variable resistor 94, the FETs 31 and 32 are switched. The oscillation frequency can be changed. If the switching frequency of the FETs 31 and 32 is increased, the lamp combined current of the discharge lamps 56 to 59 is decreased and the lamp output can be decreased. Further, if the switching frequency of the FETs 31 and 32 is lowered, the lamp combined current of the discharge lamps 56 to 59 rises and the lamp output can be raised. Therefore, the diode 92
By changing the variable resistor 94 with the off state,
Discharge lamps 56-59 are in full light (100% dimming)
The outflow current I (= I1) can be set so that The variable resistor 94 is set so that the discharge lamps 56 to 59 are in the full light lighting state when the diode 92 is off.

To turn off the diode 92 (current I2 flowing through the resistor R2 = 0), it is sufficient that V2-VF≤V1. Therefore, the output voltage V1 of the operational amplifier 77 when the discharge lamps 56 to 59 are all-lighted. The voltage of the variable reference voltage source 80 may be set so that V1 = V2-VF. VF is the forward voltage of diode 92. That is,
If the output voltage V1 of the operational amplifier 77 is set to be substantially equal to the voltage V2 at the frequency control terminal 34 of the switching control circuit 33, the lamp output (that is, the lamp current) is reduced by the thinning lighting, and V1 is lower than that at the time of full lighting. When it goes up, the diode 92 is turned off, and the switching frequency f of the inverter 3 is fixed to the frequency during full light. Therefore,
When all lights are turned on, even if the discharge lamps are thinned out, the remaining discharge lamps operate at the same frequency, and an overcurrent can be prevented from flowing.

On the other hand, during dimming, if the voltage E of the dimming variable reference voltage source 80 is adjusted to be lower than the set voltage during full light, the lamp current detected by the detection resistor 4 is constant. Since the output voltage V1 of the operational amplifier 77 is adjusted to be low, the diode 92 is turned on and the resistor 91 receives the current I2.
Flows. Here, I2 = (V2-VF-V1) / R2, and I2 increases as V1 decreases. R2 is the resistance value of the resistor 91. Therefore, during dimming, the outflow current I from the control terminal 34 is I = I1 + I2 = {V2 / R1} + {(V2-VF-V
1) / R2}. Since V2 is always constant, the outflow current I during dimming increases by I2, which causes the switching frequency f
As the lamp output also increases, the lamp output decreases and dimming can be performed.
As described above, since the variable reference voltage source 80 is lowered to perform the dimming, the diode 92 is turned on during the dimming, and the lamp output is controlled by the constant power control. The constant power control of the lamp output changes according to the dimming degree by the variable reference voltage source 80.

Next, looking at such thinning-out lighting during dimming, at the time of thinning-out, the constant voltage control maintains the value (lamp output) before thinning out the detection voltage of the detection resistor 4 (ie, lamp output). Thus, the switching frequency f is lowered so as to increase the lamp output per remaining discharge lamp, but the frequency f does not lower the switching frequency under full light. This is because the diode 92 that tries to exceed the output voltage V1 of the operational amplifier 77 from V2 is turned off, and the outflow current I is set to a value corresponding to all light. Therefore, even during dimming, the switching frequency f does not become lower than the frequency during full light, and each lamp current of the discharge lamp is regulated with the lamp current during full light as the upper limit.

FIG. 2 shows the output voltage V1 of the control voltage generating circuit 7.
It shows the change of the switching frequency f with respect to.

In FIG. 2, when the lamp output decreases,
The voltage V1 rises. In the range of V1≥V2-VF, the switching control circuit 33 does not work and the switching frequency f
Is set to the frequency at all light and becomes constant. When the variable reference voltage source for dimming 80 is adjusted so that V1 <V2-VF, the switching frequency f increases, the lamp output decreases, and dimming is performed.

FIG. 3 shows a lighting fixture equipped with the discharge lamp lighting device of FIG. FIG. 3 schematically shows the lighting fixture as viewed from below. In practice, a diffusive cover is mounted over the discharge lamp. Reference numeral 100 denotes a lighting fixture main body, and a lighting device 101 as shown in FIG. 1 is mounted on the lighting fixture main body 100. A socket 102 holds a plurality of discharge lamps 56 to 59.

[0023]

As described above, according to the present invention, it is possible to prevent an overcurrent from flowing in the discharge lamp even when thinning lighting is performed in the case of multiple lighting.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a graph illustrating the operation of FIG.

FIG. 3 is a plan view of a lighting fixture equipped with the discharge lamp lighting device of FIG.

[Explanation of symbols]

 1 ... Commercial AC power supply 2 ... Double voltage rectification circuit 3 ... Transistor inverter 4 ... Current detection resistor 5 ... Discharge lamp circuit 7 ... Control voltage generation circuit 9 ... Control current generation circuit 31, 32 ... FET 33 ... Switching control circuit 52 ... 55 ... Ballast coil 56-59 ... Discharge lamp 60-63 ... Starting capacitor 73, 77 ... Opamp 80 ... Dimming variable reference voltage source 92 ... Diode 94 ... Full-light frequency setting variable resistor 100 ... Lighting fixture body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H05B 41/24 L 7913-3K

Claims (2)

[Claims] 1. An inverter including switching control means capable of changing an output frequency, an inverter for switching a DC voltage at an output of the switching control means to convert it into a high frequency voltage, and a plurality of discharge lamps provided in parallel with each other. And a discharge lamp circuit that includes a plurality of ballast coils and a starting capacitor connected to each discharge lamp, and that drives the plurality of discharge lamps with a high-frequency voltage from the inverter, and a lamp current that flows through the plurality of discharge lamps. Detecting means for detecting the combined value of, a control voltage generating means for generating a control voltage based on a detection signal from the detecting means, and an output frequency of the switching control means of the inverter corresponding to the all-light frequency of the inverter. The output voltage of the control voltage generating circuit is larger than a preset predetermined value In this case, the output frequency is set to a value corresponding to the all-light frequency of the inverter, and when the output voltage of the control voltage generating circuit is smaller than a predetermined value, the switching control means is set so that the output voltage becomes constant. And a control current generating means for controlling the output frequency of the discharge lamp lighting device. 2. A lighting fixture equipped with the discharge lamp lighting device according to claim 1.