JPH0845689A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To use commonly a single capacitor for preventing DC lighting when the lamp goes in its final period of lifetime and for preventing thermal /destruction of a transistor when the lamp is off load. CONSTITUTION:A parallel resonance circuit of capacitor 2 and choke 3 and a series circuit of transistor 10 are connected with the ends of a DC power supply 1, and a series circuitry of a feedback transformer 8 and a discharge lamp 6 equipped with a preheat capacitor 7 and a capacitor 4 is connected parallel with the choke 3. From the connection point of the capacitor 4 with the discharge lamp 6 a resistance 5 is connected with the base of the transistor 10, and a series resonance circuit of a capacitor 13 and the secondary winding of the transformer 8 is connected with the base of the transistor 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trigger device for a switching element in a one-stone self-excited inverter.

[0002]

2 and 3 show circuit diagrams of a conventional discharge lamp lighting device. In FIG. 2, a capacitor 14 for preventing direct current lighting during lamp life is connected in series with the feedback transformer 8. Further, the resistor 5 is connected to the positive electrode side of the DC power supply 1 and the base of the transistor 10 so that the base current of the transistor 10 is supplied when the DC power supply 1 is turned on. In FIG. 3, a capacitor 14 for preventing direct current lighting during lamp life is connected in series with the feedback transformer 8 as in FIG. 2, but a resistor 5 and a capacitor 15 are provided on the positive electrode side of the direct current power source 1 and the base of the transistor 10. Are connected in series, and the base current of the transistor 10 is supplied when the DC power supply 1 is turned on.

[0003]

The above-mentioned conventional technique is shown in FIG.
In the circuit, there was a risk that current would continue to flow into the base of the transistor when the lamp was unloaded, causing thermal damage to the transistor. On the other hand, in the circuit of FIG. 3, the number of components has increased because a capacitor is added to prevent thermal destruction of the transistor when the lamp is not loaded. An object of the present invention is to prevent thermal destruction of a transistor when the lamp is unloaded without increasing the number of parts.

[0004]

In order to achieve the above object, the present invention is to connect a capacitor for preventing direct current lighting during the life of a lamp to a filament on the positive electrode side of a discharge lamp in series, and to turn on the power from the connection point. The base current of the transistor is supplied.

[0005]

[Function] The capacitor connected in series with the filament on the positive electrode side of the discharge lamp stops direct current from flowing when it is charged, so it is possible to prevent direct current lighting during the life of the lamp and also to prevent the current from flowing to the base of the transistor when the lamp is unloaded. Does not continue to flow, preventing thermal breakdown of the transistor.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. This figure shows a circuit diagram of a one-stone self-excited discharge lamp lighting device. A parallel resonance circuit of a capacitor 2 and a choke 3 and a series circuit of a transistor 10 are connected to both ends of a DC power supply 1, and a choke 3
In parallel with this, a series circuit of a discharge lamp 6 having a capacitor 4 and a preheating capacitor 7 and a feedback transformer 8 is connected. In addition, from the connection point between the capacitor 4 and the discharge lamp 6, the resistance 5
Is connected to the base of the transistor 10, and the base of the transistor 10 is connected to the secondary winding of the feedback transformer 8 and the series resonance circuit of the capacitor 13. In this device, when the DC power supply 1 is turned on, the base current of the transistor 10 is supplied via the capacitor 4 and the resistor 5, and the transistor 10 is turned on. After that, the transistor 10 switches due to the series resonance of the secondary winding of the feedback transformer 8 and the capacitor 13 and the parallel resonance of the capacitor 2 and the choke 3, and the discharge lamp 6 is turned on. At this time, when the discharge lamp 6 reaches the end of its life and the oxide on one of the filaments at both ends of the discharge lamp 6 is completely consumed and direct-current lighting occurs due to discharge in only one direction, the capacitor 4 accumulates electric charge and a current is generated. It stops flowing. Therefore, direct current lighting can be prevented. When the DC power supply 1 is turned on when there is no load, the current flowing through the capacitor 4 and the resistor 5 to the base of the transistor 10 does not flow due to the accumulation of charges in the capacitor 4. Therefore, thermal destruction of the transistor 10 can be prevented.

[0007]

According to the present invention, the capacitor for preventing direct current lighting at the end of the lamp life and the capacitor for preventing thermal destruction of the transistor when the lamp is not loaded can be shared by one capacitor, so that the number of parts need not be increased. .

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a conventional discharge lamp lighting device.

FIG. 3 is a circuit diagram of another conventional discharge lamp lighting device.

[Explanation of symbols]

1: DC power source, 2: capacitor, 3: choke, 4: capacitor, 5: resistance, 6: discharge lamp, 7: preheating capacitor, 8: feedback transformer, 10: transistor, 13: capacitor.

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[Procedure amendment]

[Submission date] July 18, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

FIG.

[Fig. 2]

[Figure 3]

Claims (1)

[Claims] 1. A device in which a parallel resonant circuit formed by a choke and a capacitor and a switching element are connected in series, and a discharge lamp having a preheating capacitor in parallel with the resonant circuit and an inductor element are connected in series. A discharge lamp lighting device characterized in that a capacitor is connected in series with a filament on the positive electrode side of the discharge lamp, and a switching element is triggered when the power is turned on from the connection point.