JP2712170B2 - Fluorescent lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluorescent lamp lighting device for lighting a fluorescent lamp at a 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. As a circuit generally used as a high-frequency lighting device, there is a one-stone self-excited inverter circuit shown in FIG. In this circuit, when commercial power is turned on, the rectifier 1
A DC power supply is provided by a power supply circuit including the power supply circuit and the smoothing capacitor 2. A current flows to the base of the transistor 9 via the track resistor 14, and the transistor 9 is turned on. At that time, the collector current and the positive electrode of the smoothing capacitor 2 → the oscillation transformer 4
4A → the collector of the transistor 9 → the emitter of the transistor 9 → the negative electrode of the smoothing capacitor 2.
Further, since an electromotive force is generated in the secondary winding 4B of the oscillation transformer 4 in a direction for turning on the transistor 9, the transistor 9 is kept on. Next, when the collector current Ic of the transistor 9 satisfies Ic> hfe ・ Ib (hfe: current amplification factor, Ib: base current), the electromotive force of the secondary winding 4 </ b> B 9 is turned off, and the transistor 9 is rapidly turned off. Then, the charge that has been charged in the base current limiting capacitor 10 in the direction of making the base potential negative is discharged through a reset circuit composed of a series body of the resistor 13 and the diode element 12, and the base potential of the transistor 9 rises. Then, the transistor 9 is turned on again, and the same operation is repeated thereafter to perform high-frequency oscillation. As a result, a high-frequency voltage is generated in the primary winding 4A of the oscillation transformer 4 (A in FIG. 2).
Part), the bidirectional semiconductor control element 8 breaks over and the preheating current is the positive electrode of the smoothing capacitor 2 → the current limiting inductance element 6 → the electrode 5A of the fluorescent lamp 5 → the diode element 7 → the bidirectional semiconductor control element 8 → the fluorescent lamp 5 Electrode 5B
→ It flows to the collector of transistor 9. Next, when the high frequency voltage of the oscillation transformer 4 is in a reverse cycle (transistor 9
When the voltage at both ends of the diode element 7 is in the forward direction (part B in FIG. 2) and the current flowing through the bidirectional semiconductor control element 8 decreases and becomes less than the holding current Ih, the bidirectional The semiconductor control element 8 is turned off. At this time, if the voltage across the bidirectional semiconductor control element 8 is equal to or higher than the breakover voltage, the bidirectional semiconductor control element 8 operates again. Then, when the high-frequency voltage of the oscillation transformer 4 is in the reverse cycle (when the transistor 9 is turned off) and the voltage across the diode element 7 is in the reverse direction (part C in FIG. 2).
Only when the preheating current flows, the high frequency voltage is applied to the fluorescent lamp 5 and the fluorescent lamp 5 is started by applying the half-wave preheating half-wave voltage. Problems to be Solved by the Invention However, in such a circuit, by repeating the above operation, the ON period of the bidirectional semiconductor control element 8 becomes longer, the element temperature rises, the breakover voltage drops, and the fluorescent lamp 5 , The bidirectional semiconductor control element 8 operates, and the preheating current continues to flow. For this reason, problems such as abnormal heat generation of the bidirectional semiconductor control element 8 and a decrease in the luminous flux of the fluorescent lamp occur. Means for solving the problem The fluorescent lamp lighting device of the present invention is a fluorescent lamp lighting device using a high-frequency transistor inverter circuit, between the two electrodes on the non-power supply side of the fluorescent lamp having a pair of electrodes, a diode element, It has a configuration in which a starting circuit formed by connecting a capacitor and a parallel body of a bidirectional semiconductor control element in series is connected. Function By connecting a capacitor in parallel with the bidirectional semiconductor control element, the capacitor is charged when the bidirectional semiconductor control element is turned on and then turned off (the preheating current is less than the holding current Ih), and the voltage on both sides of the diode element Is lower than the forward voltage, the bidirectional semiconductor control element is turned on, but the diode element is turned off, so that no preheating current flows. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, this circuit comprises a rectifier 1 connected to a commercial power supply, a smoothing capacitor 2 connected to a rectifier 1 to form a DC power supply unit, a resonance capacitor 3 and a primary winding 4A of an oscillation transformer 4.
And the switching transistor 9 are connected in series. Further, a current limiting inductance element 6 and a fluorescent lamp 5 having a pair of electrodes 5A and 5B are connected in series, and a diode element 7, a capacitor 15 and a bidirectional A starting circuit is connected in which a parallel body with the conductive semiconductor control element 8 is connected in series. One end of the secondary winding 4B of the oscillation transformer 4 is connected to the base of the transistor 9 via the base current control capacitor 10 and the inductor 11, and the other end is connected to the negative terminal of the DC power supply. The transistor 9
Is connected in series with a series body of a resistor 12 and a diode 13 as a reset circuit of the base current limiting capacitor 10. Next, the operation of such a circuit will be described. When the commercial power is turned on, the rectifier 1 and the smoothing capacitor 2
And a power supply circuit, a DC power is supplied, a current flows to the base of the transistor 9 via the starting resistor 14, and the transistor 9 is turned on. At that time, the collector current is the positive electrode of the smoothing capacitor 2 → the primary winding 4A of the oscillation transformer 4 → the collector of the transistor 9 → the emitter of the transistor 9 →
It flows to the negative electrode of the smoothing capacitor 2. Further, since an electromotive force is generated in the secondary winding 4B of the oscillation transformer 4 in a direction for turning on the transistor 9, the transistor 9 is kept on. Then, the collector current Ic of the transistor 9
When Ic> hfe · Ib (hfe: current amplification factor, Ib: base current), the collector current goes to saturation, so the secondary winding 4B
In the direction of turning off the transistor 9, and the transistor 9 is rapidly turned off. Then, the charge that has been charged in the base current limiting capacitor 10 in the direction of making the base potential negative is discharged through the reset circuit, 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 in the primary winding 4A of the oscillation transformer 4 (part A in FIG. 2), and the bidirectional semiconductor control element 8 breaks over and the preheating current is reduced to the smoothing capacitor 2.
→ the current limiting inductance element 6 → the fluorescent lamp electrode 5A → the diode element 7 → the bidirectional semiconductor control element 8 → the fluorescent lamp electrode 5B → the collector of the transistor 9. Next, when the high frequency voltage of the oscillation transformer 4 is in the reverse cycle (when the transistor 9 is turned off) and the voltage across the diode element 7 is in the forward direction (part B in FIG. 2), the bidirectional semiconductor control element 8 is turned on. When the flowing current decreases below the holding current Ih, the bidirectional semiconductor control element 8
Is turned off. Therefore, when the capacitor 15 is charged and the voltage across the diode element 7 falls below the forward voltage, the bidirectional semiconductor control element 8 is turned on, but the diode element 7 is turned off, so that the preheating current stops flowing. . Next, the preheating current does not flow because the high frequency voltage of the oscillation transformer 4 is in the reverse cycle (when the transistor 9 is turned off) and the voltage across the diode element 7 is in the reverse direction (portion C in FIG. 2). A high-frequency voltage is applied to the fluorescent lamp 5 to start the fluorescent lamp 5. As a result, the ON period of the bidirectional semiconductor control element 8 decreases, the element temperature does not rise, the breakover voltage does not change, and when the fluorescent lamp 5 shifts to the main discharge, the lamp voltage decreases and the bidirectional semiconductor control element 8 decreases. Becomes inactive, and the preheating current stops flowing. Effect of the Invention As described above, the fluorescent lamp lighting device of the present invention reduces the on-period of the bidirectional semiconductor control element at the start of the lamp, reliably shuts off the preheating current, and shifts the fluorescent lamp to main discharge. As a result, abnormal heat generation of the bidirectional semiconductor control element and reduction of the luminous flux of the fluorescent lamp can be prevented.

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 waveform diagram of the device, and FIG. 3 is a circuit diagram of a conventional fluorescent lamp lighting device. It is. 1 ... Rectifier, 2 ... Smoothing capacitor, 3 ... Resonant capacitor, 4 ... Oscillation transformer, 4A ... Primary winding of oscillation transformer, 4B ... Secondary winding of oscillation transformer, 5 ... Fluorescent lamp, 5A, 5B: Fluorescent lamp electrodes, 6: Current limiting inductance element, 7: Diode element, 8: Bidirectional semiconductor control element, 9: Transistor.

Continuation of front page    (56) References JP-A-62-126595 (JP, A)                 JP-A-57-141895 (JP, A)                 JP-A-62-208594 (JP, A)                 JP-A-62-133699 (JP, A)                 JP-A-62-26795 (JP, A)                 JP-A-62-133698 (JP, A)                 JP-A-62-126596 (JP, A)                 Shokai Sho 57-197197 (JP, U)

Claims (1)

(57) [Claims] In a fluorescent lamp lighting device using a high-frequency transistor inverter circuit, a diode element and a parallel body of a capacitor and a bidirectional semiconductor control element are connected in series between the two electrodes on the non-power supply side of the fluorescent lamp having a pair of electrodes. A fluorescent lamp lighting device, characterized in that a starting circuit comprising: