JP2830311B2 - Fluorescent lamp lighting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp lighting device, and more particularly to a starting device using a semiconductor switching element for a fluorescent lamp having a preheating electrode.

2. Description of the Related Art A glow starter has been mainly used as a starting device of a fluorescent lamp.
There are drawbacks such as short life. Recently, a starting circuit using a semiconductor switching element has been developed. However, since the starting circuit is expensive, the demand has been limited. For this reason, it has been desired to develop a starting device using a semiconductor switching element and having an inexpensive circuit system.

Based on the above request, a circuit as shown in FIG. 3 using an inexpensive transistor as a semiconductor switch element has been proposed. In the figure, 1 is an AC power supply, 2 is a ballast,
Reference numeral 3 denotes a fluorescent lamp, 4 denotes a noise prevention capacitor, 5 denotes a diode, 6, 7, and 11 denote resistors, 8 denotes an electrolytic capacitor, 9 and 12 denote Zener diodes, 10 denotes a thyristor, and 13 denotes a transistor.

Next, the operation of the circuit will be described with reference to the voltage / current waveforms of the respective parts in FIG. In the figure, V is the waveform of the power supply voltage, I is the waveform of the preheating current of the ballast 2 and the fluorescent lamp 3,
_VL is a voltage waveform across the fluorescent lamp. Here, when the power supply voltage V is in a negative cycle, no preheating current flows due to the reverse blocking characteristic of the diode 5. Next, when the power supply voltage V is a positive cycle and the power supply voltage V becomes equal to or higher than the voltage of the Zener diode 12 at t ₁ , a base current is supplied to the base of the transistor 13 via the resistor 11. A large collector current flows from the power supply via the diode 5. At this time,
The power supply of the timer circuit of the resistor 6 and the electrolytic capacitor 8 is maintained at the Zener voltage of the Zener diode 12. As described above, a half-wave of the preheating current flows to preheat the preheating electrode of the fluorescent lamp 3, and when the time set by the timer circuit is reached, the timer circuit of the resistor 6 and the electrolytic capacitor 8 supplies the electrolytic current to the gate terminal of the thyristor 10. The charge of the capacitor 8 is released through the resistor 7 and the Zener diode 9,
Turn on thyristor 10. When that time t _2, since the collector current of the transistor 13 is forced off, the kick voltage V _L is generated in the ballast 2 by inductance, thereby lighting the fluorescent lamp 3.

In the starting circuit using the transistor 13 as a semiconductor switch element, the transistor 13 is turned on when the fluorescent lamp 3 is in an emitterless state, and is thermally destroyed by a rise in temperature. At that time, if the transistor 13 had a resistance value, heat was generated, and there was a risk of fire.

Means for Solving the Problems The fluorescent lamp lighting device of the present invention comprises a closed circuit comprising an AC power supply, a ballast and a fluorescent lamp with a preheating electrode, and a timer circuit between the non-power supply side preheating electrode terminals of the fluorescent lamp. The collector terminal and the emitter terminal of a transistor having a base circuit that performs switching at are connected via a diode, a thermal fuse element is directly connected to the transistor, and the thermal fuse is arranged near the transistor. doing.

Effect By connecting a thermal fuse in series with a transistor, the transistor is destroyed, and even if it generates heat with a resistance value, it is cut at a set temperature by a thermal fuse arranged near the transistor. As a result, adverse effects due to heat generation due to transistor breakdown can be prevented.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, an AC power supply 1, a ballast 2, and a fluorescent lamp 3 form a closed circuit. A noise prevention capacitor 4 is connected to both ends of the fluorescent lamp 3. A collector terminal and an emitter terminal of a transistor 13 having a base circuit for switching by a timer circuit including a resistor 6 and an electrolytic capacitor 8 are connected between the non-power-supply-side preheating electrode terminals of the fluorescent lamp 3 via a diode 5. Connected. Further, a thermal fuse 14 is connected in series with the transistor 13.
Are connected in series, and this thermal fuse is arranged near the transistor 13 as shown in FIG.

In FIG. 1, 7 indicates a resistor, 9 indicates a Zener diode, 10 indicates a thyristor, 11 indicates a resistor, and 12 indicates a Zener diode.

Next, since the operation of this circuit at the time of normal lighting is the same as that of the conventional circuit shown in FIG. 3, it is omitted, and only the operation at the time of abnormality will be described. When the fluorescent lamp 3 reaches the end of its life, one of the electrodes of the fluorescent lamp 3 loses its emitter, a half-wave discharge occurs, and the transistor 13 maintains a preheated state. As a result, the transistor 13 is thermally destroyed due to the self-temperature rise. When the transistor 13 is destroyed, it has a certain resistance value, so that the transistor 13 further generates heat by a half-wave preheating current. As a result, the printed circuit board and the like may be ignited by heat. However, since the thermal fuse 14 is connected in series with the transistor 13 and is disposed at a position where the temperature of the transistor 13 can be detected, the thermal fuse 14 is cut off at a certain set temperature. As a result, no current flows through the transistor 13, and the transistor 13 enters a safe state.

Effect of the Invention As described above, the present invention can provide a fluorescent lamp lighting device that can prevent smoke and ignition at the end of the life of a starting circuit of a fluorescent lamp and when a transistor is destroyed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fluorescent lamp lighting device according to one embodiment of the present invention, FIG. 2 is a diagram for explaining the arrangement of thermal fuses and transistors in the circuit, and FIG. 3 is a conventional fluorescent lamp. FIG. 4 is a circuit diagram of the lighting device, and FIG. 4 is a voltage / current waveform diagram of the conventional device. 1 AC power supply 2 Ballast 3 Fluorescent lamp 5
…… Diode, 6,7 …… Resistance, 8 …… Electrolytic capacitor, 9,12 …… Zener diode, 10 …… Thyristor,
11 ... resistor, 13 ... transistor, 14 ... thermal fuse.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tetsuya Tahara 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-138494 (JP, A) JP-A-1- 246791 (JP, A) JP-A-57-74995 (JP, A) JP-A-57-134891 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/18

Claims (1)

(57) [Claims] 1. A transistor comprising a closed circuit comprising an AC power supply, a ballast, and a fluorescent lamp with a preheating electrode, and a base circuit for switching by a timer circuit between non-power supply side preheating electrode terminals of the fluorescent lamp. Wherein the collector terminal and the emitter terminal are connected via a diode, a thermal fuse is connected in series with the transistor, and the thermal fuse is arranged near the transistor.