JPH07201480A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To reduce loss when a transistor is turned on. CONSTITUTION:A parallel circuit of a DC power supply 1, inductor 2 and a capacitor 3 and a closed circuit containing a transistor 9 are provided. A series circuit 5, 7 containing an electric discharge lamp 5 and a feedback transformer 7 is connected to both ends of the parallel circuits 2, 3. A capacitor 6 is connected in parallel to the electric discharge lamp 5. A closed circuit, containing a secondary side of the feedback transformer 7, inductor 12, capacitor 13 and base emitter connected of the transistor 9, is provided. A rectifier 10, connected in reverse parallel to the base emitter connection of the transistor 9, and a resistor 11, inserted in series to the rectifier 10, are provided. A capacitor 14 is connected in parallel to the base emitter connection of the transistor 9. By this constitution, a vibration curve of base emitter voltage of the transistor 9 is relaxed by parallelly connecting the capacitor 14, and the base emitter voltage is prevented from exceeding on-voltage of the transistor 9 when it is turned on.

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 which switching loss of a switching transistor is reduced.

[0002]

2. Description of the Related Art A conventional device shown in FIG. 3 will be described. Figure 3
The device comprises a DC power supply 1, a parallel circuit of a capacitor 3 and an inductor 2, and a closed circuit including a transistor 9 for switching. A series circuit including a discharge lamp 5 and a feedback transformer 7 is connected to both ends of the parallel circuit 3 or 2. A capacitor 6 is connected in parallel with the discharge lamp 5. A closed circuit including the secondary side of the feedback transformer 7, the inductor 12, the capacitor 13, and the base-emitter junction of the transistor 9 is provided. It comprises a rectifier 10 connected in antiparallel with the base-emitter junction of the transistor 9 and a resistor 11 inserted in series with the rectifier 10.
Reference numeral 4 is a starting resistor.

[0003]

FIG. 4 shows operating waveforms of the transistor 9 of the device shown in FIG. FIG. 4A shows the collector current I _C and the collector-emitter voltage V _CE .
4B shows the base-emitter voltage V _BE , and FIG.
FIG. 4C is an enlarged waveform at turn-on in FIG.
In the figure, the base
Since the rise of the emitter voltage V _BE is steep, the ON voltage of the transistor 9 is exceeded when the transistor 9 is turned on, and the collector-emitter voltage V _BE becomes as shown in the waveform of FIG.
_{When CE} has a positive voltage, it is turned on and a switch loss occurs.
For this reason, the transistor 9 may generate heat and run into heat runaway. The present invention aims to reduce the above switching loss.

[0004]

To achieve the above object, a capacitor is connected in parallel with the base-emitter junction of a transistor.

[0005]

When the capacitor is connected in parallel to the base / emitter junction of the transistor, the capacitor is placed in series with the inductor in operation after the transistor is turned off. Therefore, the vibration curve around the inductor becomes gentle, and when the transistor turns on, it does not exceed the on-voltage of the transistor. This eliminates the loss when the transistor turns on.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of FIGS. 1 and 2 according to the present invention will be described. Incidentally, the part numbers and the like of the device of FIG. 1 are cited as they are, and a part of the overlapping description will be omitted. The main operation of the apparatus shown in FIG. 1 is as follows. When the DC power supply 1 is applied,
A drive current flows through the base / emitter junction of the transistor 9 via the resistor 4, and the transistor 9 is turned on. At the same time, a preheating current flows through one filament of the discharge lamp 5, the capacitor 6, the other filament, the primary side of the feedback transformer 7, and the transistor 9. This keeps the transistor 9 on. Next, the feedback transformer 9
The oscillating current flowing through the inductor 12 and the capacitor 13 is generated by the voltage generated in the secondary winding of the transistor 9
Flows to the base-emitter junction of. When this oscillating current reversely biases the transistor 9, the transistor 9
Turn off. At the same time, inductor 2 and capacitor 3
The energy stored in the parallel circuit is discharged through the discharge lamp 5, and a voltage is applied by the series resonance of the primary side of the feedback transformer 7 and the capacitor 6, so that the discharge lamp 5 shifts from the preheat state to the lighting state. Then, when the oscillatory current due to this starts flowing again from the discharge lamp 5 to the transistor 9, the transistor 9 is turned on again, and the same operation is repeated thereafter. Although the feedback transformer 7 of the device in FIG. 1 also serves as the ballast inductor of the discharge lamp 5, a ballast inductor (not shown) may be inserted in series with the feedback transformer 7 and the discharge lamp 5. In the present invention, as shown in FIG. 1, the capacitor 14 is connected in parallel with the base-emitter junction of the transistor 9. In this way, after the transistor 9 turns off,
The capacitor 14 and the inductor 12 are connected in series in the series resonance circuit. Therefore, the oscillation curve of the base-emitter voltage V _BE of the transistor 9 becomes gentle because the capacitor 14 is connected in parallel, and does not exceed the on-voltage of the transistor 9 when the transistor 9 turns on. This causes the transistor 9
The loss at turn-on is reduced.

[0007]

According to the present invention, the loss at the turn-on of the switching transistor at the time of preheating, at the time of lighting, and at the end of the discharge lamp life is reduced, so that the reliability is improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a device of the present invention.

FIG. 2 is an operation waveform diagram thereof, (a) shows collector current I _C and collector-emitter voltage V _CE , (b) shows base-emitter voltage V _BE , and (c) shows (a). It is an enlarged waveform at turn-on.

FIG. 3 is a circuit diagram of a conventional device.

FIG. 4 is an operation waveform diagram thereof, (a) shows collector current I _C and collector-emitter voltage V _CE , (b) shows base-emitter voltage V _BE , and (c) shows turn-on of (a). It is an enlarged waveform of time.

[Explanation of symbols]

1: DC power supply, 2.12: inductor, 3.6.13.
14: capacitor, 4/11: resistance, 5: discharge lamp, 7:
Feedback transformer, 8/10: rectifier

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[Procedure amendment]

[Submission date] June 15, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

Claims (1)

[Claims] 1. A DC power supply, a parallel circuit of an inductor and a capacitor, and a closed circuit including a transistor, and a series circuit including a discharge lamp and a feedback transformer is connected to both ends of the parallel circuit.
A capacitor is connected in parallel with the discharge lamp, a secondary circuit of the feedback transformer, an inductor, a capacitor, and a closed circuit including a base-emitter junction of the transistor are provided, and the capacitor is connected in antiparallel with the base-emitter junction of the transistor. And a resistor inserted in series with the rectifier, and a capacitor is connected in parallel with the base-emitter junction of the transistor.