JPH1116690A - Lighting device for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable lighting device for a discharge lamp which prevents a big stress from being generated in a switching element even when a lamp is removed while it is lighted. SOLUTION: This device is equipped with an inverter circuit to convert a direct current voltage into a high frequency voltage, a series circuit of discharge lamps La1, La2 to which the high frequency voltage of the inverter circuit is supplied, a resonance circuit connected to an output end of the inverter circuit through either one of filaments of each discharge lamp La1, La2, and a closed circuit formed through another filament of each discharge lamp La1, La2. In this case, a lamp socket cover to cover a lamp socket is provided, and it is structured so that it can be removed from the filament side forming a resonance circuit when the lamp is removed while it is lighted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a discharge lamp lighting device.

[0002]

2. Description of the Related Art FIG. 2 is a schematic plan view and FIG. 3 is a circuit diagram according to the present invention.

FIG. 2 is a schematic plan view showing a two-lamp lighting device for a discharge lamp (hereinafter, referred to as a lamp).
A lamp L having an appliance body 1 and lamp sockets 3, 5
a1; La2 having lamp sockets 4 and 6; an electronic ballast 2 for lighting the lamps La1 and La2; and lead wires L1 to L7 connecting between the lamps La1, La2 and the electronic ballast 2; , La
2, the electronic ballast 2 and the lead wires L1 to L7 are housed in the instrument body 1.

FIG. 3 is a circuit diagram of a discharge lamp lighting device including the lamps La1 and La2, the electronic ballast 2, and the lead wires L1 to L7.

[0005] An AC power supply E, a filter circuit F connected to both ends of the AC power supply E and including a capacitor C4 and an inductor L3, a rectifier DB for rectifying the AC power supply E through the filter circuit F, and an output of the rectifier DB A smoothing capacitor C2 connected to an end of the rectifier DB and smoothing a DC voltage output of the rectifier DB; and an inverter circuit connected to an output end of the rectifier DB and converting a voltage between both ends of the smoothing capacitor C2 into a high-frequency voltage and supplying it to a load circuit. And rectifier D
And a capacitor C1 connected to the output terminal of B. Here, the inverter circuit is a so-called half-bridge type inverter circuit including a series circuit of a field effect transistor (hereinafter, referred to as a switching element) Q1 and Q2, and the switching elements Q1 and Q2 are alternately turned on and off by the control circuit 10. Are repeated to perform high frequency lighting of the lamps La1 and La2 as loads. Also,
The load circuit is connected to a series circuit of the capacitor C4 connected to both ends of the switching element Q2 and the primary winding n1 of the leakage transformer T1, and to the secondary side of the leakage transformer T1 via the leads L2, L3, L5, L6. It is composed of lamps La1 and La2 connected in series, and a capacitor C3 connected to both ends of a series circuit of lamps La1 and La2 via lead wires L1 and L4. Also, the leakage inductance of the leakage transformer T1 and the capacitor C
3 together form a series resonance circuit. Capacitor C
Reference numeral 4 denotes a DC component cutting capacitor.
It has a capacitance value sufficiently larger than 3.

Then, the current of the capacitor C3 flows through the path of the secondary winding n2 of the leakage transformer T1, the filament f1, the capacitor C3, the filament f4, and the secondary winding n2 of the leakage transformer T1, whereby the filament f1 and the filament f4 flow. And the secondary winding n3 of the leakage transformer T1 → the filament f2 → the filament f3 → the secondary winding n3 of the leakage transformer T1.
When the current flows through the path, the filament f2 and the filament f3 are preheated. Lamps La1, La2
By sufficiently preheating each filament before applying a high voltage to both ends, the transition from startup to lighting is facilitated.

[0007]

However, in the above-mentioned conventional example, if the lamp La1 is removed during the operation of the lamp, for example, the lamps La1 and La2 have no problem, but the filament f2 is removed before the filament f1. And the leakage inductance of the leakage transformer T1 and the capacitor C
3 keeps the series resonance circuit configured,
An excessive current flowing through the resonance circuit causes the switching element Q1,
A problem arises in that the current flows to Q2 and the like and a large stress is generated in the switching elements Q1 and Q2 and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the switching elements Q1, Q2 even when the lamp is removed during lamp operation.
It is an object of the present invention to provide a highly reliable discharge lamp lighting device that prevents a large stress from being generated.

[0009]

According to the first aspect of the present invention, there is provided an inverter circuit for converting a DC voltage to a high-frequency voltage, and a plurality of inverter circuits for supplying the high-frequency voltage to the inverter circuit. A series circuit of the discharge lamps, a resonance circuit connected to the output terminal of the inverter circuit via one filament of each discharge lamp, and a closed circuit formed through the other filament of each discharge lamp. And a protection means for detaching the filament connected to the resonance circuit first when the discharge lamp is detached.

According to the invention described in claim 2, the protection means covers the filament forming the closed circuit.

According to the third aspect of the present invention, the closed circuit includes:
A discharge lamp preheating circuit is formed.

According to a fourth aspect of the present invention, the resonance circuit forms a preheating circuit for the discharge lamp.

[0013]

FIG. 1 is a schematic plan view of an embodiment according to the present invention.

The difference from the conventional example shown in FIG. 2 is that a lamp socket cover 7 for covering the lamp sockets 5 and 6 is provided so that when the lamp is removed while the lamp is lit, the leakage inductance of the leakage transformer T1 and the capacitor C3 are removed. This is configured so as to be removed from the filament side (here, filaments f1 and f4 shown in FIG. 3) forming the series resonance circuit. Description is omitted.

With this configuration, in any case where the lamp is removed while the lamp is lit, the series resonance circuit formed by the leakage inductance of the leakage transformer T1 and the capacitor C3 is removed first, so that the switching element Q1 , Q2 and the like can be prevented from generating a large stress.

Although two lamps are used, any number of lamps may be used, and the configuration of the inverter circuit may be any.

[0017]

According to the first to fourth aspects of the present invention, even if the lamp is removed during the operation of the lamp, reliability for preventing a large stress from being generated in the switching elements Q1, Q2, etc. And a discharge lamp lighting device with high reliability.

[Brief description of the drawings]

FIG. 1 shows a schematic plan view of an embodiment according to the present invention.

FIG. 2 shows a schematic plan view of a conventional example according to the present invention.

FIG. 3 shows a circuit diagram according to the invention.

[Explanation of symbols]

 f filament La discharge lamp

Claims (4)

[Claims] 1. An inverter circuit for converting a DC voltage to a high-frequency voltage, a series circuit of a plurality of discharge lamps to which the high-frequency voltage of the inverter circuit is supplied, and the inverter via one filament of each of the discharge lamps. In a discharge lamp lighting device including a resonance circuit connected to an output terminal of a circuit and a closed circuit formed through the other filament of each of the discharge lamps, the discharge lamp is connected to the resonance circuit when the discharge lamp is removed. A discharge lamp lighting device provided with a protection means for detaching the filament first. 2. The discharge lamp lighting device according to claim 1, wherein said protection means covers said filament forming said closed circuit. 3. The discharge lamp lighting device according to claim 1, wherein the closed circuit forms a preheating circuit for the discharge lamp. 4. The discharge lamp lighting device according to claim 1, wherein the resonance circuit forms a preheating circuit for the discharge lamp.