JP2590676B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a discharge lamp lighting device using an inverter.

[0002]

2. Description of the Related Art Conventionally, as this kind of apparatus, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 123694 (prior art 1) is known. In the prior art 1, a discharge lamp is turned on by a self-excited transistor inverter. However, this prior art 1 does not disclose anything about a so-called soft start means for sufficiently preheating the electrodes of the discharge lamp at the start of the discharge lamp to prevent the life of the discharge lamp from deteriorating.

Another conventional example of lighting a discharge lamp with a self-excited transistor inverter is disclosed in JP-A-36-22.
No. 223 (prior art 2) is known. In the prior art 2, a variable resistor is provided in a base circuit of the main transistor, and the variable resistor changes the on-period of the main transistor, thereby dimming the discharge lamp. This prior art 2 also does not show anything about the soft start means.

Further, Japanese Patent Application Laid-Open No. 58-54874 (Prior Art 3) is known. The prior art 3 includes an output transformer having a primary winding and a feedback winding, and a transistor for controlling power supplied to the primary winding, and is supplied from the feedback winding via an LC series resonance circuit. The transistor is driven by the base current to generate a high-frequency voltage. The output transformer is provided with a resonance capacitor forming a parallel resonance circuit with an inductance component of the output transformer.

Further, Japanese Patent Application Laid-Open No. 57-110084 (prior art 4) has been proposed. In this method, when the discharge lamp is started, the base current of the switching transistor of the transistor inverter is reduced from that at the time of normal lighting, so that the inverter output voltage is maintained until the filament is sufficiently heated. Is performed so as to be lower than the starting voltage of the lamp.

Further, as disclosed in Japanese Patent Application Laid-Open No. 57-208098 (Prior Art 5), a series circuit of a capacitor and a switch is connected in parallel to a resonance capacitor of an inverter, and the switch is turned on and off. There is also known a device that switches the oscillation frequency of an inverter.

[0007]

In all of the prior arts 1 to 3, no consideration is given to sufficiently preheating the electrodes of the discharge lamp before starting the discharge lamp. Therefore,
Since a high voltage is generated at the same time as the DC power supply is turned on, the so-called cold start occurs when the electrodes of the discharge lamp are not sufficiently preheated, which causes the problem of early blackening and short life of the discharge lamp. there were.

In the prior art 2, since a variable resistor is used, a power loss occurs due to a base current flowing through the variable resistor. Although this loss is relatively small because it is based on a relatively small base current, it becomes a hindrance to the efficiency improvement for this type of device that requires high efficiency.

In the prior art 4, since the base current of the switching transistor is reduced as compared with the normal state, the switching transistor is easily operated in class A, the power loss in the switching transistor is large, and the switching transistor is likely to be burdened. There's a problem.

In the prior art 5, since the capacitance of the capacitor for resonance of the inverter is changed,
The capacitors and switches added for switching must have a sufficient withstand voltage to withstand the output power of the inverter, and it has been difficult to reduce the size and cost of the device.

The present invention has a relatively simple structure, prevents the power loss in the switching transistor from increasing, and starts the electrode of the discharge lamp after sufficiently preheating it. An object of the present invention is to provide a discharge lamp lighting device capable of preventing blackening and shortening of service life.

[0012]

According to the first aspect of the present invention,
A self-excited transistor inverter that converts a DC power supply voltage to a high-frequency voltage; a discharge lamp that is lit by a high-frequency output of the transistor inverter; a plurality of capacitors provided in a base circuit of a main transistor of the transistor inverter; A switch for changing the capacitance of the capacitor by switching a plurality of capacitors; and by operating the switch, the electrode can be sufficiently preheated and a discharge lamp cannot be started until a predetermined time has elapsed since the DC power supply was turned on. And a timer circuit for switching the frequency to a frequency sufficient for lighting the discharge lamp after a predetermined time has elapsed.

According to the first aspect of the present invention, the ON period of the main switching device is determined by the capacitance of the capacitor connected to the input portion, and the main switching device performs a self-excited switching operation. By the switching operation of this main switching device,
The supplied DC voltage is converted to a high-frequency voltage. Also,
By changing the capacitance of the capacitor, the ON period of the switching device changes and the frequency changes, so that the output supplied to the discharge lamp changes. Then, when starting the discharge lamp, the switching frequency is changed so that the electrodes can be sufficiently preheated and the output voltage is suppressed to such a level that the discharge lamp cannot be started. As a result, the discharge lamp does not perform so-called cold start.

In the first and second aspects of the present invention, a so-called soft start operation for reducing the output of the inverter at the time of starting the discharge lamp is performed. However, the present invention is not limited to this. In this case, the frequency may be changed so as to reduce the output of the inverter.

Further, the present invention can be appropriately modified and implemented without departing from the spirit of each invention. For example, as an inverter, a so-called auxiliary power supply type inverter which rectifies a part of the output and stores it in a capacitor and supplies the inverter as auxiliary power while the output of a rectifying circuit for non-smoothing rectifying the AC power is low. May be applied.

A second aspect of the present invention is a self-excited transistor inverter for converting a DC power supply voltage to a high-frequency voltage, a discharge lamp lit by the high-frequency output of the transistor inverter, current limiting means for limiting a lamp current of the discharge lamp,
In a discharge lamp lighting device, further comprising an output means for performing electrode preheating and starting of the discharge lamp, wherein an LC resonance circuit is formed in an input circuit of a main transistor of the transistor inverter, a plurality of capacitors of an input circuit of the transistor are provided. A switch for changing the capacity of the capacitor by switching the switch, and a timer circuit for operating this switch.The frequency is such that the electrode can be preheated sufficiently and the discharge lamp cannot be started until a predetermined time has elapsed since the DC power was turned on. And an electrode preheating means for operating the switch by a timer circuit after a predetermined time has elapsed to switch to a frequency sufficient for lighting the discharge lamp.

According to the present invention, the on-period of the main transistor is determined by the resonance of the LC resonance circuit connected to the input portion, and the main transistor performs a self-excited switching operation. The supplied DC voltage is converted into a high-frequency voltage by the switching operation of the transistor. Further, the on-period of the main transistor changes with a change in the resonance frequency of the LC resonance circuit, so that the output supplied to the discharge lamp changes. Then, when starting the discharge lamp, the switching frequency is changed so that the electrodes can be sufficiently preheated and the output voltage is suppressed to such a level that the discharge lamp cannot be started. As a result, the discharge lamp does not perform so-called cold start.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Reference numeral 1 denotes a self-excited inverter, for example, output terminals a and b of an unillustrated DC power supply including an AC power supply and a smooth or non-smooth rectifier circuit or a battery.
Connected between them. The inverter 1 according to the present embodiment is, for example, a one-block blocking oscillation type transistor inverter that is well known and disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-54874. Reference numeral 2 denotes a discharge lamp having electrodes 2a and 2b, which is connected to a secondary winding of an output transformer 11 as output means 11s, and is preheated, started, and lit. Although not shown, current limiting means for limiting lamp current, which is used as common sense for lighting the discharge lamp 2, is provided.

The inverter 1 is mainly formed by an output transformer 11 and a main switching device 12 which enables a transistor. Hereinafter, the inverter 1 will be described in detail. One output transformer 11 is connected between the positive output terminal a of the DC power supply and the collector of the switching device 12.
The secondary winding 11p is connected, and the primary winding 11p
And a resonance capacitor 13 is connected in parallel. The emitter of the switching device 12 is connected via a diode 14 to the negative output terminal (common terminal) b of the DC power supply.
In this embodiment, one end of a base feedback winding 11f of the output transformer 11, which is a feedback power supply, is connected to the negative output terminal b of the DC power supply, and the other end is an LC series resonance including an inductor element 15 and a capacitor 16. It is connected to the base of the switching device 12 via a circuit. The transistor 31 of the reset circuit 3 is provided at both ends of the capacitor 16.
And the base of the transistor 31 is connected to a terminal wound around the other end of the base feedback winding 11f of the output transformer 11 via a diode 32 or the like. I have.

The electrode preheating means 4 comprises an auxiliary capacitor 41 provided in parallel with the capacitor 16, a switch 42 connected in series to the auxiliary capacitor 41, and a timer circuit 43 for controlling the conduction of the switch 42. Is what is being done. Such an electrode preheating means 4 is such that the auxiliary circuit 41 is electrically disconnected by the timer circuit 43 only for a predetermined period when the discharge lamp 2 is started. As a result, the combined capacitance of the plurality of capacitors 16 and 41 is reduced, and the resonance frequency of the LC series resonance circuit for supplying the base current of the switching device 12 is increased. As a result, the ON period of the switching device 12 is shortened, that is, the oscillation frequency is increased, so that the oscillation frequency of the inverter 1 is increased, or the power stored in the output transformer 11 is reduced to supply the discharge lamp 2. Required power can be reduced.

The switch 42 of this embodiment comprises a thyristor 44 having a one-way conduction direction, and a diode 45 connected to the thyristor 44 in antiparallel.

The diode 14 protects the switching device 12 from a reverse voltage between the base and the emitter, and supplies a base drawing current without excess or shortage. The reset circuit 3 discharges and resets the capacitor 16 (and the capacitor 41) when the switching device 12 is turned off and the base feedback winding voltage becomes negative. The provision of the reset circuit 3 prevents a reduction in Q of the LC resonance circuit and a deterioration in switching characteristics of the switching device 12 due to connection of a discharging resistor in parallel with the capacitor 16 (and the capacitor 41).

Next, the operation will be described. When the DC power is turned on and supplied to the inverter 1, the inverter is turned on.
In the converter 1, a base current is supplied to the switching device 12 via a starting resistor (not shown), and the switching device 12 is turned on. When the switching device 12 is turned on, a voltage is generated in the primary winding 11p and the feedback winding 11f of the transformer 11, and in this embodiment, the voltage of the base feedback winding 11f is changed to the base feedback winding 11f-capacitor 16 -Inductor 1
5--Adds to the positive feedback loop consisting of the base emitter of the switching device 12 to forward bias the switching device 12;

On the other hand, in the electrode preheating means 4, the switch 42 is turned off until a predetermined time elapses after the power is turned on. Therefore, the combined capacitance of the capacitors 16 and 41 is relatively small, and the resonance frequency of the series resonance circuit is high. Therefore, the ON time of the switching device 12 is controlled to be shorter, the oscillation frequency of the inverter 1 increases, the output voltage decreases, and the power supplied to the discharge lamp decreases. At this time, the induced voltage of the output means 11s is set lower than the starting voltage of the discharge lamp 2. When the switching device 12 is turned off, the inductance component of the transformer 11 and the resonance capacitor 13 resonate, and this resonance voltage will be inverted. As a result, the switching device 12 is again forward-biased and turned on. Thereafter, by repeating such an operation, the primary winding 11p of the transformer 11,
A high-frequency voltage is generated in the output means 11s and the feedback winding 11f.

As described above, in order to reduce the output voltage by shortening the on-time of the switching device 12 for a predetermined time, the discharge lamp 2 is not started by the high frequency output from the inverter 1 and the electrodes are preheated.

In the present embodiment, the electrode preheating means 4 operates at the output voltage of the feedback winding 11f. When the time for sufficiently preheating the electrodes of the discharge lamp 2 elapses after the power is turned on and the electrode preheating means 4 turns on the switch 42, the capacitor 1
The combined capacitance of 6, 41 becomes relatively large, and the resonance frequency of the series resonance circuit becomes low. Therefore, the ON period of the switching device 12 becomes relatively long, and the output voltage value of the inverter 1 becomes relatively large. As a result, the discharge lamp 2 whose electrodes are sufficiently preheated is applied with a high-frequency voltage higher than the starting voltage between the two electrodes, and is started and lit.

Here, in order to control the on-period of the switching device by changing the resonance frequency of the series circuit of the inductor and the capacitor connected to the input portion of the switching device, the withstand voltage and the contact capacity of the capacitor used for switching and the switch are controlled. There is an advantage that a small one can be used.

[0028]

As described above, according to the first and second aspects of the present invention, the capacitance of the plurality of capacitors of the input circuit of the switching device is changed to change the electrodes of the discharge lamp until a predetermined time has elapsed since the power was turned on. The electrode preheating means that can sufficiently preheat the battery but keep the output voltage at such a level that it cannot be started is provided, so that the configuration is simple, miniaturization and cost reduction are possible, and power loss in the switching device increases. It is possible to eliminate or reduce the early blackening and short life of the discharge lamp while preventing the discharge lamp, and to provide a discharge lamp lighting device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1. Inverter 2. Discharge lamp 4. Electrode preheating means. 16, 41: Capacitor 12: Switching device 42: Switch 43: Timer circuit

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-208098 (JP, A) JP-A-57-123694 (JP, A) JP-A-60-65498 (JP, A) JP-A-60-1985 207290 (JP, A) JP-A-57-44995 (JP, A) JP-A-57-208097 (JP, A) JP-A-48-84479 (JP, A) JP-A-52-100769 (JP, A) Shoko 36-22223 (JP, Y2)

Claims (2)

(57) [Claims] A self-excited inverter for converting a DC power supply voltage into a high-frequency voltage; a discharge lamp lit by a high-frequency output of the self-excited inverter; a plurality of capacitors provided in an input circuit of a main switching device of the self-excited inverter. A switch for changing the capacitance of the capacitor by switching a plurality of capacitors in the input circuit of the main switching device; and by operating the switch, the electrode preheating is sufficient until a predetermined time has elapsed since the DC power was turned on. And the output voltage is suppressed to such a frequency that the discharge lamp cannot be started.
A timer circuit for switching to a frequency sufficient for the discharge lamp to light after a predetermined time has elapsed. 2. A self-excited transistor inverter for converting a DC power supply voltage to a high-frequency voltage, a discharge lamp lit by a high-frequency output of the transistor inverter, current limiting means for limiting a lamp current of the discharge lamp, and electrode preheating of the discharge lamp And an output means for performing a starting operation. In a discharge lamp lighting device in which an LC resonance circuit is formed in an input circuit of a main transistor of the transistor inverter, by switching a plurality of capacitors of the input circuit of the transistor, It consists of a switch for changing the capacity and a timer circuit for operating this switch.The electrode voltage can be sufficiently preheated until a predetermined time has elapsed since the DC power was turned on, and the output voltage is suppressed to a frequency that cannot start the discharge lamp. After a predetermined time has elapsed, the switch is operated by a timer circuit. A discharge lamp lighting device comprising an electrode preheating means for switching to a frequency sufficient for lighting the discharge lamp.