JP3127538B2 - Discharge lamp lighting device and lighting equipment - Google Patents

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 lighting multiple discharge lamps using an inverter, and a lighting fixture equipped with the same.

[0002]

2. Description of the Related Art In recent years, many lighting circuits for discharge lamps use a high-frequency inverter.

[0003] The reason for this is that high-frequency lighting can improve the luminous efficiency of the lamp, that there is little flicker in the lamp output, that the starting time of the lamp can be shortened, and that when multiple lamps are lit (without thinning-out lighting), the entire lamp is lit. This is because the dimmable lighting for controlling the light output can be relatively easily performed, and the lighting circuit can be reduced in size and weight.

[0004] Conventionally, when a discharge lamp is turned on using a transistor inverter, a constant power control of the lamp output is performed by controlling the frequency of an oscillator for switching the transistor. Specifically, the current flowing through the transistor inverter is detected (ie,
By controlling the switching frequency (by detecting a change in the lamp output), control is performed to maintain a constant power of the lamp output. When the lamp output decreases, the switching frequency is controlled to decrease to increase the lamp output. When the lamp output increases, the switching frequency is increased to control to decrease the lamp output (having a series resonance circuit.
Differential in the lag region).

In the above-described discharge lamp lighting device, when multiple lamps are lit, thinning-out lighting may be considered at the time of lamp replacement or the like. In this case, in the above-described constant power control technique, when the thinning-out operation is performed, the transistor inverter operates to maintain the constant power (that is, to maintain the current flowing through the inverter). There is a problem that an overcurrent flows.

[0006]

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

In view of the above-mentioned problems, the present invention provides a discharge lamp lighting device and a lighting fixture equipped with the same, in which an overcurrent does not flow through the discharge lamp even when thinning is performed in the case of multiple lamp lighting. It is intended to provide.

[0008]

A discharge lamp lighting device according to the present invention includes switching control means capable of changing an output frequency, and an inverter which switches a DC voltage at an output of the switching control means and converts the DC voltage into a high frequency voltage. And a plurality of discharge lamps provided in parallel with each other, a plurality of ballast coils connected to each of the discharge lamps, and a starting capacitor, wherein the plurality of discharge lamps are driven by a high-frequency voltage from the inverter. and lighting circuit, a detection means for detecting the combined value of the lamp current flowing through the plurality of discharge lamps, said analyzing
When it is determined that all light is turned on according to the output of the output means
Of the inverter so that the light output is almost constant.
Turn on the discharge lamp by changing the switching frequency
If it is determined that the lighting is
It is configured to turn on the discharge lamp at a constant frequency.
Control means .

[0009]

According to the present invention, when a plurality of discharge lamps are illuminated with all light, the remaining discharge lamps operate at the same frequency even if the discharge lamps are thinned, thereby preventing an overcurrent from flowing. Also,
When dimming the lamp, when the discharge lamps are thinned out, the remaining discharge lamps receive the lamp output (wattage) of the removed discharge lamps, but do not flow more than the maximum lamp current (all-light lamp current). .

[0010]

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

In FIG. 1, reference numeral 1 denotes a commercial AC power supply. The output of the 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 adding a rectified half cycle of the AC positive electrode side and a rectified half cycle of the negative electrode side. Are connected in the forward direction, while the diode 22 is connected in the reverse direction, and a capacitor 23 and a capacitor 23 are 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 configured to connect to connection points 3 and 24. Also,
The transistor inverter 3 connects the drain / source paths of two field effect transistors (hereinafter abbreviated as FETs) 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 each of the gates 2.
By turning on T31 and T32 alternately, 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 is used. TA76494 is an oscillator whose oscillation frequency changes in proportion to the magnitude of the current I flowing out of the control terminal 34. A current detecting resistor 4 as lamp output detecting means is connected between the source of the FET 32 and the negative terminal of the voltage doubler rectifier circuit 2.

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

The detected voltage of the current detecting resistor 4 is supplied to a control voltage generating circuit 7 using two operational amplifiers.
The control voltage generation circuit 7 converts the voltage of the detection resistor 4 through a smoothing circuit including a resistor 71 and a capacitor 72,
A non-inverting input terminal of a non-inverting amplifier circuit composed of an operational amplifier 73 and resistors 74 and 75 is input to the
6 and the operational amplifier 77 and the resistor 7
The inverting input terminal of the inverting amplifier circuit composed of the variable reference voltage source 80 and the variable reference voltage source 80 is supplied to the inverting output terminal V1 and supplied to the control current generating circuit 9 in the next stage. The control current generating circuit 9 connects the output terminal of the operational amplifier 77 to a resistor 91.
, The anode of the diode 92 is connected to the oscillation frequency control terminal 34 of the switching control circuit 33, and the control terminal 34 is connected to a reference potential via a series circuit of a resistor 93 and a variable resistor 94. Connected to a point.

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

The output of the commercial AC power supply 1 is a voltage doubler rectifier circuit 2
And the rectified voltage is applied to 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.
Is off, only while FET 31 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 an FET 31
Is turned on, the current is split and flows to the ballast coils 52 to 55 and the discharge lamps 56 to 59 through the capacitor 51, merges again, and flows 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 detection resistor 4, and the discharge lamps 56 to 59. Then, when the FET 31 is turned on and the FET 32 is turned off again, each of the ballast coils 52 to
A current is supplied to the discharge lamp 55 and the discharge lamps 56 to 59. The voltage detected by the current detection resistor 4 is the discharge lamps 56 to 5
9 is proportional to the sum of each lamp output (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 non-inverts and amplifies the detection voltage after smoothing the detection voltage, and further inverts and amplifies and outputs it. The output voltage V1 is small if the lamp output detected by the resistor 4 is large, and large if 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 higher than the input voltage supplied to the inverting input terminal. The output voltage V1 is varied by varying the set voltage E, and the discharge lamp 56
It is possible to control the light by changing the lamp combined current 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 resistor 93 and a variable resistor 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 of the control terminal 34 is 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 resistor 93 and the variable resistor 94. Accordingly, the outflow current I can be changed by changing the variable resistor 94 to change 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 are in a linear relationship, if the outflow current I is changed by changing the variable resistor 94, it is possible to switch the FETs 31 and 32. 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 decreases, and the lamp output can be reduced. If the switching frequency of the FETs 31 and 32 is reduced, the lamp combined current of the discharge lamps 56 to 59 increases, and the lamp output can be increased. Therefore, the diode 92
Is turned off, and the variable resistor 94 is varied,
Discharge lamps 56 to 59 are all-light-on (100% dimming)
It is possible to set the outflow current I (= I1) such that The variable resistor 94 is set so that the discharge lamps 56 to 59 are turned on in the all-light state when the diode 92 is off.

In order to turn off the diode 92 (the current I2 flowing through the resistor R2 = 0), it suffices that V2 -VF≤V1. Therefore, when the discharge lamps 56 to 59 are all lighted, the output voltage V1 of the operational amplifier 77 is turned on. The voltage of the variable reference voltage source 80 may be set so that V1 = V2−VF. VF is the forward voltage of the 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 due to the thinned-out lighting, and V1 is compared with the full lamp. When it rises, the diode 92 turns off, and the switching frequency f of the inverter 3 is fixed to the frequency at the time of all light. Therefore,
At the time of all-light lighting, even if the discharge lamps are thinned out, the remaining discharge lamps operate at the same frequency, thereby preventing an overcurrent from flowing.

On the other hand, at the time of dimming, if the voltage E of the dimming variable reference voltage source 80 is adjusted in a direction lower than the set voltage at the time of all light, the lamp current detected by the detecting 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 current I2 is supplied to the resistor 91.
Flows. Here, I2 = (V2-VF-V1) / R2, and I2 increases as V1 decreases. R2 is the resistance value of the resistor 91. Therefore, at the time of 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 at the time of dimming increases by I2, whereby the switching frequency f
Increases, the lamp output decreases, and dimming can be performed.
As described above, since the dimming is performed by lowering the variable reference voltage source 80, the diode 92 is turned on at the time of 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, with regard to such thinning-out lighting at the time of dimming, at the time of thinning-out, the value (lamp output) before the thinning-out of the detection voltage (ie, lamp output) of the detection resistor 4 is maintained by constant power control. The operation is performed in such a manner that the switching frequency f is lowered in order to increase the lamp output per remaining discharge lamp, but the frequency f does not lower the switching frequency in all light. This is because the diode 92 that turns off the output voltage V1 of the operational amplifier 77 to exceed V2 is turned off, and the outflow current I is set to a value corresponding to all light. Therefore, even at the time of dimming, the switching frequency f does not become lower than the frequency at full light, and each lamp current of the discharge lamp is regulated with the upper limit of the lamp current at full light.

FIG. 2 shows the output voltage V1 of the control voltage generation circuit 7.
5 shows a change in the switching frequency f with respect to the period.

In FIG. 2, when the lamp output decreases,
The voltage V1 increases. In the range of V1≥V2-VF, the switching control circuit 33 does not operate, and the switching frequency f
Is set to the all-light frequency and is constant. When the dimming variable reference voltage source 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 apparatus equipped with the discharge lamp lighting device of FIG. FIG. 3 schematically shows a state where the lighting fixture is viewed from below. In practice, a diffusive cover is mounted over the discharge lamp. Reference numeral 100 denotes a lighting fixture main body, on which a lighting device 101 as shown in FIG. 1 is mounted. 102 is a socket for holding 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 through the discharge lamp even when performing the thinning-out operation in the case of multiple lamp lighting.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to one 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. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply 2 ... Double voltage rectifier 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 ... operational amplifier 80 ... dimming variable reference voltage source 92 ... diode 94 ... all-light frequency setting variable resistor 100 ... lighting equipment body

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H05B41 / 24 H05B41 / 24L (56) References JP-A-63-86399 (JP, A) JP-A-4-301398 ( JP, A) JP-A-4-209499 (JP, A) JP-A-3-2833397 (JP, A) JP-A-2-215095 (JP, A) JP-A-5-21190 (JP, A) Hei 1-145096 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 41/42 H05B 41/16 H05B 41/24

Claims (2)

(57) [Claims] An inverter including switching control means capable of changing an output frequency, for switching a DC voltage at the output of the switching control means to convert the DC voltage into a high-frequency voltage, and a plurality of discharge lamps provided in parallel with each other And a discharge lamp circuit including a plurality of ballast coils and a starting capacitor connected to each discharge lamp, the plurality of discharge lamps being driven by a high-frequency voltage from the inverter, and a lamp current flowing through the plurality of discharge lamps. Detecting means for detecting the combined value of the signals, and a case where it is determined that all light is turned on according to the output of the detecting means.
In such a case, the inverter is controlled so that the light output becomes almost constant.
Discharge lamp by changing the switching frequency of
Switch on if it is determined that the
To turn on the discharge lamp with a constant switching frequency
The discharge lamp lighting device being characterized in that and a control means which is. 2. A lighting device equipped with the discharge lamp lighting device according to claim 1.