JPH10172780A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent trouble or the like of a lighting device by the last stage of the service life of a discharge lamp by restarting a switching element, changing operation time of a preheating time setting timer circuit, and switching it to a lighting frequency. SOLUTION: In starting operation of a discharge lamp 11 of a discharge lamp lighting device, when voltage of a capacitor 28 exceeds Zener voltage of a Zener diode 37, a transistor 39 is turned on, and electric charge of capacitors 24 and 31 is discharged through a diode 40. When the voltage of the capacitor 28 exceeds the breakover voltage of a bidirectional trigger diode 30, electric charge of the capacitor 28 is let to move to the base of a transistor 6, and oscillation is started. Accordingly, the transistor 6 repeats on and off in a self-excited manner, and a DC voltage is converted into a high frequency. Even if oscillation of a switching element is stopped by a half-wave discharge phenomenon by dispersion or the like of the discharge lamp at low temperature starting time, it is restarted, and since preheating time of the discharge lamp can be changed, the discharge lamp can be lighted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp at a high frequency.

[Prior art]

FIG. 1 shows a conventional discharge lamp lighting device. In FIG. 1, a DC power supply circuit including a rectifier 2 and a smoothing capacitor 3 connected to a commercial power supply 1,
A self-excited inverter circuit is configured by connecting a switching output transistor 6 in series with a parallel resonance circuit including a resonance capacitor 4 and a resonance inductance 5. A diode 7 is connected to the transistor 6 in parallel. The output terminal of the output transistor 6 includes a primary winding 8a of a current transformer, a DC cut capacitor 9,
The ballast inductance 10 is connected to one end of a discharge lamp 11, and the other end of the discharge lamp 11 is connected to a DC power supply circuit. A preheating capacitor 1 is provided between both ends of the discharge lamp 11.
2 are connected. Secondary winding 8b of current transformer
Is connected to the base of the transistor 6 via a resistor 13, and is connected to a bias circuit including a starting resistor 14, a diode 15, and a resistor 16. A diode 17, a preheating frequency capacitor and a lighting frequency capacitor 1 are connected to the other end of the secondary winding 8a of the current transformer.
9, a lighting frequency switching circuit including a lighting switching transistor 21, a diode 20, and a resistor 22 is connected.
A preheating time timer circuit for the resistor 23 and the capacitor 24 is connected to the lighting frequency switching circuit. Further, a DC stabilized power supply circuit including a resistor 25, a Zener diode 26, and a capacitor 27 is connected to the DC power supply circuit.

[Problems to be solved by the invention]

In a conventional discharge lamp lighting device, a discharge lamp 1
1 at the end of life and the ambient temperature of the discharge lamp 11,
Due to this variation, a half-wave discharge state occurs, for example, rectification from the filament 11b to the filament 11a causes the DC cut capacitor 9 to be charged with the polarity as shown in FIG. When the capacitor 9 is sufficiently charged, when a lamp current including the excess DC component flows through the primary winding 8a of the current transformer, the secondary winding 8b
Since the ON time of the transistor 6 to which the output of the transistor 6 is input becomes long, excessive energy is accumulated in the resonance inductance 5, and a high voltage is applied to the transistor 6, which may cause a breakdown. For this reason, conventionally, the lamp voltage of the discharge lamp 11 is detected to stop or reduce the output of the transistor 6. However, the lamp voltage is increased when the discharge lamp 11 is preheated and turned on, so that the lamp voltage can be detected. And transistor 6
Output cannot be stopped or reduced.
The object of the present invention is a half-wave discharge that occurs at the transition of preheating / lighting or a half-wave discharge phenomenon that occurs at the end of life due to the variation of the discharge lamp and the ambient temperature of the related art. An object of the present invention is to prevent a failure such as destruction of an element such as a transistor.

In order to achieve the above object, a DC power supply circuit, a parallel resonance circuit comprising a resonance capacitor and a resonance inductance, and a switching element are connected in series, and an output terminal of the switching element is connected to an output terminal of the switching element. Connect the primary winding of the transformer, a DC cut capacitor and a discharge lamp, connect a preheating capacitor in parallel with this discharge lamp, connect one end of the secondary winding of the current transformer to the control terminal of the switching element, Connect the preheating frequency capacitor and lighting frequency capacitor to the other end,
A positive feedback circuit is formed, the frequency of the switching element is controlled, a current is supplied to the preheating capacitor to preheat the discharge lamp, and then a tube current is supplied to the discharge lamp to light the discharge lamp. In a lamp lighting device, a bidirectional trigger diode is turned on by a voltage of a charging circuit of a resistor and a capacitor in a starting circuit of the switching element to oscillate the switching element. In addition, a preheating time setting timer circuit is provided in the switching circuit of the lighting frequency capacitor, the voltage of the capacitor of the starting circuit is detected, the preheating time setting timer circuit is reset, and when the oscillation of the switching element stops, the switching element is reset. In addition to starting, the operating time of the preheating time setting timer circuit is changed to switch to the lighting frequency. Due to variations in the discharge lamp at the time of low-temperature startup and half-wave discharge at the end of the life of the discharge lamp, lamp current including DC current flowed, charged the DC cut capacitor, and included DC component in the current transformer. Oscillation of the switching element stops due to a decrease in the feedback current due to a lamp current or the like. Thereby, the starting circuit of the switching element is started, and the preheating time setting timer circuit is reset and the preheating time is changed. Therefore, when restarting, the preheating time can be switched.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below with reference to FIG. In FIG. 2, a rectifier 2 connected to a commercial power supply 1, a DC power supply circuit for rectifying and smoothing the commercial power supply 1 from a smoothing capacitor 3, a parallel resonance circuit including a resonance capacitor 4 and a resonance inductance 5, and an output transformer for switching. A self-excited inverter circuit is formed by connecting the resistors 6 in series. Transistor 6 has diode 7
Are connected in parallel. The output terminal of the transistor 6 is connected to a primary winding 8a of a current transformer, a DC cut capacitor 9, a discharge resistor 66, a ballast inductor 10, and one end of a discharge lamp 11, and the other end of the discharge lamp 11 is connected to a DC power supply circuit. It is connected. A preheating capacitor 12 is connected between both ends of the discharge lamp 11. One end of the secondary winding 8b of the current transformer is connected to the control terminal of the transistor 6 via the resistor 13, and a bias circuit including the diode 15 and the resistor 16 is configured. The control terminal of the transistor 6 includes a resistor 14, a capacitor 28,
A trigger circuit including a diode 29 and a bidirectional trigger diode 30 is connected. The other end of the secondary winding 8b of the current transformer is connected to a lighting frequency switching circuit including a diode 17, a preheating frequency capacitor and a lighting frequency capacitor 19, a lighting switching transistor 21, a diode 20, and a resistor 22. The lighting frequency switching circuit includes a resistor 23, a capacitor 24, and a capacitor 3
1, a preheating timer circuit including a transistor 32, a resistor 33, a Zener diode 34, a resistor 35, and a capacitor 36 is connected. In the capacitor 28 of the trigger circuit,
Zener diode 37, resistor 38, transistor 3
9. A reset circuit consisting of a diode 40 is connected,
The capacitors 24 and 31 of the preheat timer circuit are reset. A restart timer circuit including a resistor 41 and a capacitor 42 includes a Zener diode 43, a resistor 44,
A trigger stop circuit consisting of a transistor 45 and a preheat timer change reset circuit consisting of resistors 47 and 48 and a transistor 49 are connected via a NOT circuit 46. The discharge lamp 11 is connected to a discharge lamp end-of-life detection circuit including a capacitor 50, resistors 51 and 52, a capacitor 53, diodes 54 and 55, a resistor 56, a capacitor 57, a Zener diode 58, a resistor 59, a transistor 60 and a resistor 61. Have been. The output of the transistor 60 of the discharge lamp end-of-life detection circuit and the output of the NOT circuit 46 are connected to a NOR circuit 62, and the output of the NOR circuit 62 is a resistor 6
3, a stop circuit for the transistor 6 including the transistor 65 and the transistor 65 is connected. The DC power supply circuit has a resistor 2
5, a DC stabilized power supply circuit comprising a zener diode 26 and a capacitor 27 is connected. The starting operation of the discharge lamp lighting device thus configured will be described. The operation of starting the discharge lamp 11 of the discharge lamp lighting device depends on the commercial power supply 1.
Is turned on, the capacitor 28 is charged via the DC power supply circuit and the resistor 14. When the voltage of the capacitor 28 exceeds the Zener voltage of the Zener diode 37, the transistor 39 is turned on, and the capacitor 2 is connected via the diode 40.
The charges of 4, 31 are discharged. When the voltage of the capacitor 28 exceeds the breakover voltage of the bidirectional trigger diode 30, the charge of the capacitor 28 is
Oscillate by flowing to the base. As a result, the transistor 6 repeats on / off self-excitingly, and converts the DC voltage to a high frequency. Also, the secondary winding b of the current transformer 8
The preheating frequency is set by the inductance and the capacitor 18, and the filament of the discharge lamp 11 is preheated via the preheating capacitor 12. Further, when the voltage across the capacitor 24 of the preheating timer circuit exceeds the threshold value of the transistor 21, the discharge lamp 11 is turned on by switching to the lighting frequency. When a half-wave discharge occurs at the time of starting due to the ambient temperature of the discharge lamp 11, variation in the discharge lamp, end of life, or the like, the lamp current includes a direct current. Therefore, the lamp current decreases, the feedback current of the current transformer 8 decreases, and the oscillation of the transistor 6 stops. When the oscillation stops, the charge of the capacitor 9 is discharged by the resistor 66, and the voltage across the capacitor 36 turns on the transistor 32.
As a result, when the voltage of the capacitor 28 described in the start operation exceeds the Zener voltage of the Zener diode, the transistor 39 is turned on, the capacitors 24 and 31 are reset, the preheating time is changed, and the restart operation can be performed. .

[0007]

According to the present invention, the switching element can be restarted and the preheating time of the discharge lamp can be changed even if the switching element stops oscillating due to a half-wave discharge phenomenon caused by variations in the discharge lamp at the time of low temperature startup. Therefore, the discharge lamp can be turned on. Further, when the discharge lamp reaches the end of its life, it is prevented from restarting after a specified time, so that it is possible to prevent a failure of the lighting device due to the end of the life of the discharge lamp.

[Brief description of the drawings]

FIG. 1 is a conventional circuit diagram

FIG. 2 is a circuit diagram of the present invention.

[Explanation of symbols]

1: commercial power supply, 2: rectifier, 3: smoothing capacitor,
4: resonance capacitor, 5: resonance inductance,
6: Transistor, 7: Diode, 8: Current transformer, 9: DC cut capacitor, 10: Ballast inductance, 11: Discharge lamp, 12: Preheating capacitor,
18: capacitor for preheating frequency, 19: capacitor for lighting frequency

Claims (1)

[Claims] A switching element is connected in series with a DC power supply circuit, a parallel resonance circuit including a resonance capacitor and a resonance inductance, and a primary winding of a current transformer and a DC cut capacitor are connected to an output terminal of the switching element. A discharge lamp is connected, a preheating capacitor is connected in parallel to the discharge lamp, one end of a secondary winding of the current transformer is connected to a control terminal of the switching element, and a preheating frequency capacitor is lit at the other end. By connecting a capacitor for frequency, forming a positive feedback circuit, controlling the frequency of the switching element by switching the capacitor, passing a current to the capacitor for preheating, and after preheating the discharge lamp, In a discharge lamp lighting device in which a lamp current is caused to flow by flowing a tube current to the discharge lamp, when starting at a low temperature, variations in the discharge lamp, When the DC cut capacitor is charged by the half-wave discharge phenomenon at the end of the life of the discharge lamp and a lamp current including a DC component flows in the current transformer, and the oscillation of the switching element stops, the switching element is restarted, A discharge lamp lighting device characterized by changing a preheating time.