JP2000243587A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device with high reliability, capable of reducing stress to be applied to the whole discharge lamp lighting device by reducing the stress applied to a connecting part, etc., of a discharge lamp even when the load becomes light by removing one lamp. SOLUTION: The discharge lamp lighting device is constituted with a power source circuit 1 for outputting DC voltage by rectifying and filtering an AC power source Vac; a high frequency power source 2 for converting the output of the power source circuit 1 into AC high frequency voltage; two load circuits A, B to be connected in parallel across output terminals of the high frequency power source 2; and a control part 3 for controlling DC voltage output of the power source circuit 1 by receiving the detecting output of a discharge lamp lighting judging circuit 4. When the detecting output of the discharge lamp lighting judging circuit 4 becomes abnormal, output supply to a discharge lamp is reduced to a specified level from a usual state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a discharge lamp lighting device.

[0002]

2. Description of the Related Art Conventionally, in a discharge lamp lighting device in which a plurality of discharge lamps are lit in parallel by supplying a high-frequency voltage from one high-frequency power supply, for example, even if one lamp is removed, the other discharge lamps are lit and maintained. There is something.

[0003]

However, the above-described conventional example has the following problems.

In a discharge lamp lighting device in which a plurality of discharge lamps are turned on in parallel by outputting a high-frequency voltage from one high-frequency power supply, the plurality of discharge lamps are turned on until one lamp is removed (ie, in a normal state). Power is supplied to the load side, so if one lamp is removed and the load side is lightly loaded, a greater stress will be applied to the connection part of the discharge lamp than in normal times, and the discharge lamp will be turned on Large stress is applied to the entire device.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce a stress applied to a connection portion of a discharge lamp even when one load is removed and a light load is applied to a load side. An object of the present invention is to provide a highly reliable discharge lamp lighting device that can reduce stress applied to the entire discharge lamp lighting device by reducing the stress.

[0006]

According to the first aspect of the present invention, a plurality of discharge lamps are lit in parallel by supplying a high frequency voltage from a main circuit having a high frequency power supply. The discharge lamp lighting device includes a determination circuit for detecting a light load state of each discharge lamp, and when the detection output of the determination circuit becomes abnormal, the output supply to the discharge lamp is reduced to a predetermined level from the normal state. It is characterized by.

According to a second aspect of the present invention, when the detection output of the discrimination circuit becomes abnormal, the output supply to the discharge lamp is reduced to a level necessary for starting the discharge lamp.

According to a third aspect of the present invention, the output supply to the discharge lamp is gradually reduced each time each of the discharge lamps becomes a light load state.

According to a fourth aspect of the present invention, when at least one of the discharge lamps is in a light load state, the power supply to the discharge lamp is reduced to a predetermined level.

[0010]

(Embodiment 1) FIG. 1 is a circuit diagram of a first embodiment according to the present invention, and FIG. 2 is a voltage waveform diagram thereof.

This circuit comprises a power supply circuit 1 for rectifying and smoothing an AC power supply Vac to output a DC voltage, a high-frequency power supply 2 for converting the output of the power supply circuit 1 to an AC high-frequency voltage, and an output terminal of the high-frequency power supply 2. Load circuits A and B connected in parallel to
And a discharge lamp lighting determination circuit 4 for detecting a mounted state of the discharge lamp
And a control unit 3 that receives the detection output of the discharge lamp lighting determination circuit 4 and controls the DC voltage output of the power supply circuit 1. The load circuit A includes a series circuit of a coupling capacitor C1 and a primary winding n1 of the resonance choke T1 and the discharge lamp La1, and a resonance and preheating capacitor C2 connected between the non-power supply side terminal of the discharge lamp La1. Is composed of
A resonance circuit is configured by the resonance choke T1 and the capacitor C2. The load circuit B includes a coupling capacitor C3, a primary winding n1 of the resonance choke T2, and a discharge lamp L
A series circuit a2 and a capacitor C4 for resonance and preheating connected between the non-power-supply-side terminals of the discharge lamp La2 constitute a resonance circuit with the resonance choke T2 and the capacitor C4. Further, here, the discharge lamp lighting determination circuit 4 has a configuration for detecting the mounted state of the discharge lamp by detecting the voltage of the secondary winding n2 of the resonance chokes T1 and T2.

The operation will be briefly described below with reference to FIG. During normal times (when two lamps are turned on), as shown in FIG. 2, the output voltage value of the power supply circuit 1 is increased as the state of the discharge lamp changes from preheating to starting to lighting. Here, when the discharge lamp lighting discrimination circuit 4 detects that one of the discharge lamps has become lightly loaded due to turning off or removal of one of the discharge lamps when the two lamps are turned on, the discharge lamp lighting discrimination circuit 4 detects that fact. The control unit 3 having received the output controls the output voltage value of the power supply circuit 1 in a direction lower than when the two lamps are turned on, as shown in FIG. Here, the voltage is reduced to a voltage value higher than the voltage required for starting (starting voltage).

With the above configuration, even if one of the discharge lamps is turned off or removed and the load becomes light, the voltage between terminals of the discharge lamp and the ground voltage are reduced. It is possible to reduce the stress on the parts and the like, and it is possible to reduce the stress on the entire discharge lamp lighting device.

Although two discharge lamps are used, three or more discharge lamps may be used, and the configuration of the power supply circuit 1, the high-frequency power supply 2, the control unit 3, and the discharge lamp lighting determination circuit 4 may be anything. For example, the power supply circuit 1 includes a step-up chopper circuit, a step-down chopper circuit, a step-up / step-down chopper circuit, a smoothing circuit and a chopper circuit, the high-frequency power supply 2 includes an inverter circuit, and the control section 3 detects a voltage between both ends of the discharge lamp. One that detects the mounting state of the electric light, or the like can be considered.

(Embodiment 2) FIG. 3 is a circuit diagram of a second embodiment according to the present invention, and FIG. 4 is a voltage waveform diagram thereof.

The difference from the first embodiment shown in FIG. 1 is that the control unit 3
Means that the output of the high-frequency power supply 2 is controlled. The same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The operation will be briefly described below with reference to FIG. During normal times (when two lamps are turned on), as shown in FIG. 4, the output voltage value of the high-frequency power supply 2 is increased as the state of the discharge lamp changes from preheating to starting to lighting, and the high voltage is released during starting. Vary so that it is applied to the light. Where 2
When the discharge lamp lighting discrimination circuit 4 detects that one of the discharge lamps has been turned off or removed to a light load state when the lamp is turned on, the detection output of the discharge lamp lighting discrimination circuit 4 to that effect is received. The control unit 3 includes, as shown in FIG.
Is controlled so as to lower the output voltage value of the second lamp than when two lamps are turned on. Here, the voltage is reduced to a voltage value higher than the voltage required for starting (starting voltage).

(Embodiment 3) FIG. 5 shows an operation waveform diagram of a third embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that when the two lamps are turned on, one of the discharge lamps is turned off or removed, and the light-load state is established. When the control unit 3 receives the detection output from the discharge lamp lighting determination circuit 4 to that effect, the control unit 3 changes the output voltage value of the power supply circuit 1 to a voltage necessary for starting (starting voltage) as shown in FIG. The circuit configuration is the same as that shown in FIG. 1. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

With the above-described configuration, an appropriate starting voltage is supplied when a normal discharge lamp is mounted after one of the discharge lamps is put in a light load state by being turned off or removed or the like. be able to.

(Embodiment 4) FIG. 6 is a circuit diagram of a fourth embodiment according to the present invention, and FIG. 7 is an operation waveform diagram thereof.

The difference from the first embodiment shown in FIG. 1 is that in a circuit in which three lamps are connected in parallel, first, one lamp is turned off or removed, and the light load state is established. When the light-load state is caused by turning off or removing the eyes, the output voltage value of the high-frequency power supply 2 is controlled to gradually decrease from the time when the three lamps are turned on every time each discharge lamp becomes the light-load state. The same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Note that three load circuits A, B, and C are connected in parallel between the output terminals of the high-frequency power supply 2, and the load circuit C includes a coupling capacitor C5, a primary winding n1 of a resonance choke T3, and a discharge lamp La3. Series circuit and discharge lamp L
a3, a capacitor for resonance and preheating connected between the non-power-supply-side terminals of a3, and a resonance circuit is constituted by the resonance choke T3 and the capacitor C6. In this case, the discharge lamp lighting determination circuit 4 includes the resonance chokes T1, T
2. By detecting the voltage of the secondary winding n2 of T3,
It has a configuration for detecting the mounting state of the discharge lamp.

Hereinafter, the operation will be briefly described with reference to FIG. Normally, as shown in FIG. 7, the output voltage value of the high-frequency power supply 2 is increased as the state of the discharge lamp changes from preheating to starting to lighting. Here, when the discharge lamp lighting discrimination circuit 4 detects that one of the discharge lamps has become a light load state by turning off or removing one of the discharge lamps when the three lamps are turned on, Upon receiving the detection output, the control unit 3
As shown in FIG. 7, the output voltage value of the power supply circuit 1 is controlled to be lower than when the three lamps are turned on. Further, when the discharge lamp lighting discrimination circuit 4 detects that one of the discharge lamps has been turned off or removed to a light load state, the control unit receives the detection output of the discharge lamp lighting discrimination circuit 4 to that effect. The control 3 controls the output voltage value of the power supply circuit 1 to be lower than when the two lamps are turned on, as shown in FIG. Here, in a state in which the two discharge lamps are in a light load state due to being turned off or removed, etc., the voltage is reduced to a value substantially corresponding to a voltage necessary for starting (starting voltage). It may be higher than the required voltage (starting voltage).

With the above configuration, even when the impedance on the load side changes gradually, an output corresponding to the change can be supplied to the load side. The number of discharge lamps is three, but may be four or more.

(Embodiment 5) FIG. 8 shows an operation waveform diagram of a fifth embodiment according to the present invention.

The difference from the fourth embodiment shown in FIG. 6 is that the discharge lamp lighting discriminating circuit 4 detects that a light load state is caused by turning off or removing one of the lamps.
The output voltage value of the power supply circuit 1 is substantially equal to the case where the discharge lamp lighting determination circuit 4 detects that the n lamps (n> 1, n is a natural number) are in a light load state due to being turned off or removed. Since the circuit configuration is the same as that shown in FIG. 6, the same components as those of the other fourth embodiments are denoted by the same reference numerals, and the description thereof will be omitted. Omitted.

The present invention is not limited to the above-described embodiment, but can be implemented in various modifications. For example, when the load becomes light, instead of controlling the output of the power supply circuit 1, May be controlled, or the outputs of the power supply circuit 1 and the high-frequency power supply 2 may be controlled together.

[0028]

According to the first aspect of the present invention, even if one of the discharge lamps is removed and the load side is lightly loaded, even if one of the discharge lamps is turned off or removed, the load side becomes lightly loaded. ,
Since the voltage between the terminals of the discharge lamp and the voltage to the ground are reduced, it is possible to reduce the stress applied to the connection portion of the discharge lamp and the like. Equipment can be provided.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, a normal discharge lamp can be used after the one discharge lamp is turned off or removed and becomes lightly loaded. It is possible to provide a discharge lamp lighting device capable of supplying an appropriate starting voltage when mounted.

According to the third aspect of the invention, in addition to the effect of the first aspect, even when the impedance on the load side changes gradually, an output corresponding to the change is supplied to the load side. And a discharge lamp lighting device capable of performing the same.

According to the fourth aspect of the present invention, even if one lamp is removed and the load side is lightly loaded, the stress applied to the connection portion of the discharge lamp is reduced, so that the entire discharge lamp lighting device can be manufactured. Such stress can be reduced, and a highly reliable discharge lamp lighting device can be provided.

[Brief description of the drawings]

FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

FIG. 2 shows an operation waveform diagram according to the embodiment.

FIG. 3 shows a circuit diagram of a second embodiment according to the present invention.

FIG. 4 is an operation waveform diagram according to the embodiment.

FIG. 5 shows an operation waveform diagram of a third embodiment according to the present invention.

FIG. 6 shows a circuit diagram of a fourth embodiment according to the present invention.

FIG. 7 shows an operation waveform diagram according to the embodiment.

FIG. 8 shows an operation waveform diagram of a fifth embodiment according to the present invention.

[Explanation of symbols]

 1 power supply circuit 2 high frequency power supply La discharge lamp

Claims (4)

[Claims] 1. A discharge lamp lighting device for lighting a plurality of discharge lamps in parallel by outputting a high-frequency voltage from a main circuit having a high-frequency power supply, comprising: a determination circuit for detecting a light load state of each of the discharge lamps;
A discharge lamp lighting device, wherein when the detection output of the determination circuit becomes an abnormal state, the output supply to the discharge lamp is reduced to a predetermined level from a normal state. 2. The discharge lamp lighting according to claim 1, wherein when the detection output of said determination circuit becomes abnormal, the output supply to said discharge lamp is reduced to a level necessary for starting said discharge lamp. apparatus. 3. The discharge lamp lighting device according to claim 1, wherein the output supply to the discharge lamp is gradually reduced each time each of the discharge lamps becomes a light load state. 4. The discharge lamp lighting device according to claim 1, wherein when at least one of the discharge lamps is in a light load state, the output supply to the discharge lamp is reduced to a predetermined level.