JP2687423B2 - Fluorescent lamp lighting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluorescent lamp lighting device for lighting a fluorescent lamp at high frequency.

2. Description of the Related Art It is well known that lighting a fluorescent lamp at a high frequency makes it possible to reduce the size and weight of a lighting device and improve luminous efficiency. The applicant previously described in Japanese Patent Application No. 62-180414, No. 6
A discharge lamp lighting device having a circuit as shown in the figure is proposed.

In this circuit, when commercial power is turned on, the rectifier 1
And the smoothing capacitor 2 serve as a DC power source, and a resistor 12
A current flows to the base of the transistor 9 through the transistor 9 and the transistor 9 is turned on. At that time, the collector current is the positive electrode of the smoothing capacitor 2 → the electrode 6A of the fluorescent lamp 6 → the DC bypass inductance element 8 → the electrode 6B of the fluorescent lamp 6.
→ The primary winding 5A of the current limiting inductance element 5 → the collector of the transistor 9 → the emitter of the transistor 9 → the negative electrode of the smoothing capacitor 2. Further, since electromotive force is generated in the secondary winding 5B of the current limiting inductance element 5 in the direction of turning on the transistor 9, the transistor 9 is maintained in the on state. Next, when the collector current I _c of the transistor 9 becomes I _c > hfe · I _b (hfe: current amplification factor, I _b : base current), the collector current goes toward saturation, so that the secondary winding 5B The electromotive force turns off the transistor 9, and the transistor 9 rapidly turns off. Next, the charge charged in the direction in which the base potential of the base current limiting capacitor 11 becomes negative is discharged by the reset circuit composed of the resistor 13 and the diode 14, and when the base potential rises again, the transistor 9 is turned on, and the same operation is repeated thereafter to perform high frequency oscillation. As a result, a high frequency voltage is generated across the starting circuit, for example, the starting capacitor 7, and the fluorescent lamp 6 is started. Further, the DC bypass inductance element 8 is for preventing the occurrence of a catalysis phenomenon in which mercury ions in the fluorescent lamp 6 are biased to one side electrode.

However, in such a circuit, in the end of the life of the fluorescent lamp, when the electron emissive substance on one electrode disappears,
The fluorescent lamp 6 has a rectifying function, and the lamp current waveform becomes non-symmetrical, and a direct current more than twice as much as that in the normal state of the fluorescent lamp flows through the DC bypass inductance element 8.
As a result, the DC bypass inductance element 8 may cause magnetic saturation to exceed the Curie temperature of the core, and the winding of the DC bypass inductance 8 may cause a rare short circuit, which is a safety risk.

Means for Solving the Problems A fluorescent lamp lighting device of the present invention is a device for lighting a fluorescent lamp at high frequency by an inverter, wherein a starting capacitor and a DC bypass inductance are provided between the electrodes of a fluorescent lamp having a pair of electrodes. A heat-responsive element is inserted between the fluorescent lamp and the parallel body, and the heat-responsive element is provided close to the DC bypass inductance element. The device has a configuration that is set to operate at the Curie temperature of the core.

Action At the end of the life of the fluorescent lamp, when the electron emissive material on one of the electrodes is exhausted, a direct current more than twice as much as that in the normal state of the fluorescent lamp flows through the DC bypass inductance element for the reason described above. As a result, the DC bypass inductance element causes magnetic saturation and exceeds the Curie temperature of the core. Then, since the thermal response element is provided close to the core of the DC bypass inductance element, the thermal response element operates, the DC bypass inductance element and the starting capacitor are electrically separated from the circuit, and the operation of the circuit is prevented. Stop. Therefore, it is possible to prevent the winding of the DC bypass inductance element from causing a rare short circuit. Further, the direct-current bypass inductance element prevents the direct-current component from flowing through the fluorescent lamp, so that the cataphoresis phenomenon can be prevented from occurring.

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

In FIG. 1, a smoothing capacitor 2 is connected to a rectifier 1 which is connected to a commercial power source to form a DC power supply section. The resonance capacitor 3 and the switching transistor 9 are connected in series. Further, the fluorescent lamp 6 having a pair of electrodes 6A and 6B and the primary winding 5A of the current limiting inductance element 5 are connected in series. A parallel body of the starting capacitor 7 and the DC bypass inductance element 8 is connected between the quantity electrodes 6A and 6B of the fluorescent lamp 6. A thermal fuse 4 as a heat responsive element is connected between the fluorescent lamp 6 and the parallel body. As shown in FIG. 2, the thermal fuse 4 is provided close to the core 8a of the DC bypass inductance element 8 and is set to operate at the Curie temperature of this core. As the thermal fuse 4, for example, a resin dispersion sintering type thermal fuse is used. This is because the fusible material in which the surface of the fusible alloy dispersed and sintered is covered with a thermosoftening resin is mechanically held and protected by an insulating cover during the manufacturing process, and the extrudability is imparted. By embedding the electrode terminals on both ends of the, the joint surface of the fusible body and the electrode terminals is alloyed by heat treatment and firmly fixed,
Furthermore, the outer circumference is protected and the existing one can be used. Further, one end of the secondary winding 5B of the current limiting inductance element 5 is connected to the base of the transistor 9 via the inductance element 10 and the base current limiting capacitor 11, and the other end is connected to the negative terminal of the DC power supply unit. ing.
A resistor 12 as a starting resistor of the transistor 9 is connected in series to a series body of a resistor 13 as a reset circuit of the base current limiting capacitor 11 and a diode 14.

In FIG. 2, 4a is a lead wire of the thermal fuse 4, 8b
Is a winding wound around the core 8a of the DC bypass inductance element 8, 8c is a lead wire end of the winding 8b, and 15 is a printed circuit board.

 Next, the operation of such a circuit will be described.

In FIG. 1, when the commercial power supply is turned on, the rectifier 1 and the smoothing capacitor 2 serve as a DC power supply, a current flows to the base of the transistor 9 through the resistor 12, and the transistor 9 is turned on. At that time, the collector current of the transistor 9 is the positive electrode of the smoothing capacitor 2 → the electrode 6A of the fluorescent lamp 6 → the DC bypass inductance 8 → the primary winding 5A of the current limiting inductance element 5 → the electrode 6B of the fluorescent lamp 6 → the transistor 9 It flows from the collector → the emitter of the transistor 9 → the negative electrode of the smoothing capacitor 2. Further, since the electromotive force is generated in the secondary winding 5B of the current limiting inductance element 5 in the direction of turning on the transistor 9, the transistor 9 maintains the on state. Next, when the collector current I _c of the transistor 9 becomes I _c > hfe · I _b (hfe: current amplification factor, I _b : base current), the collector current goes toward saturation, so that the secondary winding 5B The electromotive force turns off the transistor 9, and the transistor 9 rapidly turns off. Next, when the reset circuit discharges the electric charge charged in the direction in which the base potential of the base current limiting capacitor 11 becomes negative, and the base potential rises again, the transistor 9 is turned on, and the same operation is performed thereafter. High frequency oscillation is repeated. As a result, a high frequency voltage is generated across the starting capacitor 7, and the fluorescent lamp 6 is started.

In such a circuit, at the end of the life of the fluorescent lamp 6, when the electron emissive substance on one of the electrodes runs out, the fluorescent lamp 6 has a rectifying function, and as shown by the broken line in FIG. Becomes asymmetric. The solid line in FIG. 3A shows the lamp current waveform when the fluorescent lamp 6 is normal. When the lamp current waveform becomes asymmetrical, the direct-current bypass inductance element 8 has a direct-current bypass inductance element 8 when the fluorescent lamp 6 is normal (as shown in FIG. 3 (b) at this time, as indicated by a broken line in FIG. 3 (b). 8), a DC current more than twice as large as that of the current waveform flowing in FIG. As a result, the DC bypass inductance element 8 causes magnetic saturation, and the Curie temperature of the core 8a, for example, 170 ° C. is exceeded. Then, the thermal fuse 4 having a fusing characteristic of, for example, 168 ° C., which is set to blow at the Curie temperature of the core 8a, is installed close to the core 8a. The capacitor 7 and the DC bypass inductance element 8 are electrically disconnected from the circuit, and the operation of the circuit is stopped. Therefore, it is possible to prevent the winding of the DC bypass inductance element 8 from causing a rare short circuit.

In the circuit of the embodiment of the present invention, since the direct current bypass inductance element 8 is connected in parallel with the fluorescent lamp 6, the direct current component does not flow into the fluorescent lamp 6, and as a result, mercury ions are generated in the fluorescent lamp 6. It is possible to prevent the occurrence of a cataphoresis phenomenon that is biased to one electrode.

FIG. 4 shows another embodiment of the present invention in which a thermal protector 40 is used as a heat responsive element, and the other structure is exactly the same as the circuit structure shown in FIG.

FIG. 5 shows a state in which the thermal protector 40 is provided close to the core 8a of the DC bypass inductance element 8. The thermal protector 40 is provided in the container so that the fixed electrode and the movable electrode are opposed to each other, and when the predetermined temperature is reached, the movable electrode is separated from the fixed electrode and the space between both electrodes is opened. Can be used.

In FIG. 4, the circuit operation of the fluorescent lamp 6 at the normal time is the same as that of the above embodiment. When the fluorescent lamp 6 is abnormal, that is, when the electron emissive substance on one of the electrodes runs out, the DC bypass inductance element 8 causes magnetic saturation and the Curie temperature of the core 8a, for example, 170 ° C. is exceeded, as in the case of the above embodiment. . Then, the Curie temperature of the core 8a is set to open between both electrodes,
For example, a thermal protector 4 with a temperature characteristic of 168 ℃
However, since it is installed close to the core 8a, the space between both electrodes of the thermal protector 4 is opened, the starting capacitor 7 and the DC bypass inductance element 8 are electrically disconnected from the circuit, and the operation of the circuit is stopped. To do. Therefore,
The winding of the DC bypass inductance element 8 is prevented from causing a rare short circuit.

Also, in the circuit of this embodiment, the fluorescent lamp 6
Due to the DC bypass action of the DC bypass inductance element 8 connected in parallel with, it is possible to prevent the occurrence of the cataphoresis phenomenon.

EFFECTS OF THE INVENTION As described above, the fluorescent lamp lighting device of the present invention can prevent the occurrence of the cataphoresis phenomenon, can stop the circuit operation at the end of the life of the fluorescent lamp, and is extremely safe. It is a thing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fluorescent lamp lighting device according to an embodiment of the present invention, FIG. 2 is a front view showing a state in which a temperature fuse is provided close to the core of a DC bypass inductance element, and FIG. ) And (b) are waveform diagrams of the lamp current and the current flowing through the DC bypass inductance element when the fluorescent lamp is normal and abnormal, and FIG. 4 is a circuit diagram of a fluorescent lamp lighting device according to another embodiment of the present invention. FIG. 5 is a front view showing a state in which a thermal protector is provided close to the core of the DC bypass inductance element, and FIG. 6 is a circuit diagram of the fluorescent lamp lighting device previously proposed by the applicant. 1 ... Rectifier, 2 ... Smoothing capacitor, 3 ... Resonance capacitor, 4 ... Temperature fuse, 5 ... Current limiting inductance element, 5A ... Primary winding of current limiting inductance element, 5B ... Current limiting Secondary winding of the inductance element, 6 ... Fluorescent lamp, 6A, 6B ... Fluorescent lamp electrode, 7 ... Starting capacitor, 8 ... DC bypass inductance element, 9 ... Transistor, 10 ... Inductor element , 11 ... Base current limiting capacitor, 13 ... Resistor, 14 ... Diode, 40 ... Thermal protector.

Claims (3)

(57) [Claims] 1. A device for lighting a fluorescent lamp at high frequency by an inverter, wherein a parallel body of a starting capacitor and a DC bypass inductance element is connected between the electrodes of a fluorescent lamp having a pair of electrodes, and A thermoresponsive element is inserted between the fluorescent lamp and the parallel body, and the thermoresponsive element is provided close to the core of the DC bypass inductance element, and the thermoresponsive element operates at the Curie temperature of the core. The fluorescent lamp lighting device is characterized by being set to. 2. The fluorescent lamp lighting device according to claim 1, wherein the thermoresponsive element comprises a thermal fuse. 3. The fluorescent lamp lighting device according to claim 1, wherein the heat responsive element comprises a thermal protector.