JPH06196285A - Discharge lamp lighting device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a discharge lamp lighting device capable of reliably starting a discharge lamp. [Structure] A drive circuit unit 4 stops the operation of a full-bridge inverter circuit 3 which applies a rectangular wave voltage to the discharge lamp at the time of starting the discharge lamp, and a diagonal 2 of the full-bridge inverter circuit is stopped.
The two switching transistors Q2 and Q5 are driven by separate DC power supplies to apply a DC voltage to the discharge lamp La, and a voltage applied to the discharge lamp after a certain period of time sufficient to maintain arc discharge. Is provided with a discharge lamp DC starting circuit LS that switches so as to start the operation of the full-bridge inverter circuit so that the voltage becomes a rectangular wave voltage.

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 for lighting a discharge lamp such as a high pressure discharge lamp.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram of a conventional discharge lamp lighting device. This discharge lamp lighting device includes a power supply circuit unit 1 that rectifies and smoothes an AC voltage of an AC power supply VS to obtain a DC power supply voltage, and a step-down circuit that controls the DC power supply voltage to a required lamp power and outputs a DC voltage. The chopper circuit section 2, the full bridge inverter circuit section 3 for applying a rectangular wave to both ends of the discharge lamp La while inverting the polarity of the output DC voltage, and the switching transistors Q2 to Q5 of the full bridge inverter circuit section 3. Drive circuit part 4 to drive
And an igniter circuit section 5 that applies a high-voltage pulse to the discharge lamp La when the lamp is started.

The power supply circuit section 1 comprises a commercial power supply VS, a rectifying element DB1 and a smoothing capacitor C0. The commercial power supply 1 is full-wave rectified by the rectifying element DB1, smoothed by the smoothing capacitor C0 and converted into a DC power supply voltage. It The step-down chopper circuit section 2 includes a switching transistor Q1, a diode D1, a DC reactor L1, a smoothing capacitor C1, and a control circuit that controls and drives the switching transistor Q1. After that, the required lamp power control is performed and the DC voltage is output.

The full-bridge inverter circuit section 3 is composed of switching transistors Q2 to Q5. The drive circuit section 4 alternately turns on the switching transistors Q3, Q4 and Q2, Q5, and the DC output from the step-down chopper circuit section 2 is generated. While reversing the polarity of the voltage, discharge lamp L
A rectangular wave is applied by applying the voltage to both ends of a.

The drive circuit unit 4 is a low voltage DC power supply circuit unit V.
L, a signal generator OSC, a frequency divider DIV, and a drive circuit DR.

The low-voltage DC power supply circuit section VL comprises a step-down transformer T1, a rectifying element DB2, and a smoothing capacitor C4. The commercial power supply VS is stepped down by the step-down transformer T1, full-wave rectified by the rectifying element DB2, and smoothed by a smoothing capacitor C4. It is converted into a low voltage DC voltage.

The signal generator OSC is composed of two inverter drivers ID1, ID2, two resistors R2, R3 and a capacitor C5 into a well-known CR oscillator, and the signal generator OSC outputs a low-frequency driving signal. Is generated.

The frequency divider DIV is a flip-flop IC1.
And the two inverter drivers ID3 and ID4, the low-frequency driving signal output from the signal generator OSC is input to the clock input C of the flip-flop IC1, and a half of the Q output and the Q bar output is output. The frequency-divided outputs are output through inverter drivers ID3 and ID4, respectively.

The drive circuit DR includes switching transistors Q6 and Q7, a drive transformer T2, and a switching transistor Q2 of the full bridge inverter circuit section 3.
To Q5 of the base resistors R4 to R7, the switching transistors Q6 and Q7 are alternately switched by the output from the frequency divider DIV to drive the low frequency on the secondary side of the drive transformer T2. An AC output is generated to alternately drive the transistors Q2 and Q5 through the pair of base resistors R4 and R7 and the transistors Q3 and Q4 through the pair of base resistors R5 and R6.

In the igniter circuit section 5, the capacitor C2 is charged through the resistor R1, and the semiconductor switching element Sidac SSS1 is turned on when the voltage across the capacitor C2 reaches a predetermined voltage, and the voltage of the capacitor C2 is increased. Charges the capacitor C3 through the diode D2 through the transformer T3, and the spark gap G1
Discharges when the voltage across the capacitor C3 reaches a predetermined voltage and applies a high-voltage pulse to both ends of the discharge lamp La through the pulse transformer T4 to light the discharge lamp La.

[0011]

In the conventional discharge lamp lighting device as described above, at the start of the discharge lamp, a high voltage pulse from the igniter circuit is applied to both ends of the discharge lamp La as a rectangular wave voltage by a full bridge inverter circuit. The discharge lamp La is started and lit by superimposing and applying. Therefore, if the polarity of the applied rectangular wave voltage is reversed when the discharge lamp La is not in a sufficient state to sustain the arc discharge due to the high-voltage pulse, the arc lamp cannot be transferred to the arc discharge and disappears. There was a problem that it would not happen.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a discharge lamp lighting device capable of reliably starting a discharge lamp.

[0013]

In order to achieve the above object, in the present invention, a DC power supply unit, a step-down chopper circuit unit for controlling the DC power supply voltage to a required lamp power and outputting a DC voltage, and its output. A full-bridge inverter circuit section that applies a rectangular wave to both ends of the discharge lamp while reversing the polarity of the DC voltage that was generated, a drive circuit section that drives the switching transistors of the full-bridge inverter circuit section, and a high-voltage pulse is emitted when the lamp starts. In a discharge lamp lighting device having an igniter circuit section for applying to a lamp, the drive circuit section stops the operation of the full bridge inverter circuit for applying a rectangular wave voltage to the discharge lamp at the time of starting the discharge lamp, and Directly drive the discharge lamp with a DC voltage by driving it with a DC power supply with two diagonal switching transistors. In addition, after a certain period of time that is sufficient to maintain the arc discharge, the discharge lamp DC start circuit switches to start the operation of the full-bridge inverter circuit so that the voltage applied to the discharge lamp becomes a rectangular wave voltage. It is configured to include.

[0014]

When the discharge lamp is started, a DC voltage is applied to the discharge lamp for a certain period of time sufficient to maintain arc discharge, and then a rectangular wave voltage is applied by the full bridge inverter circuit.

[0015]

FIG. 1 is a circuit diagram showing an embodiment of the discharge lamp lighting device of the present invention. The basic configuration is the same as the conventional configuration shown in FIG. 2, and only the drive circuit unit 4 is different,
Descriptions other than the drive circuit unit 4 are omitted. As shown in FIG. 1, the drive circuit unit 4 of the present invention includes a low voltage DC power supply circuit unit VL, a signal generator OSC, a frequency divider DIV, a drive circuit DR, and
A discharge lamp DC starting circuit LS is attached.

The discharge lamp DC starting circuit LS has a timer circuit TM, a transistor Q8 which is turned on by the output of the timer circuit TM, and a relay RY1 which is driven when the transistor Q8 is turned on. The first relay contact r1 of the relay RY1 uses the common terminal b1 as the output of the signal generator OSC,
The normally closed contact c ₁ is connected to the input of the frequency divider DIV, and the common terminals b ₂ and b ₃ are connected to the _second and _third relay contacts r ₂ and r _3.
Is connected to the base resistors R8 and R9, and the normally open contacts a ₂ and a
₃ is connected to the bases of the switching transistors Q2 and Q5.

The commercial power supply VS is stepped down by a step-down transformer T1, full-wave rectified by rectifying elements DB3, DB4, smoothed by smoothing capacitors C6, C7, converted into a low voltage DC voltage, and diagonally switched in a full bridge inverter circuit. A base current is supplied to the transistors Q2 and Q5 through base resistors R8 and R9 to drive them, and a DC voltage is applied to the discharge lamp La. In the discharge lamp DC starting circuit LS, the transistor Q8 is turned on by the output from the timer circuit TM for a certain period of time that is sufficient to maintain arc discharge from the time of lamp starting, during which RY1 is driven and the relay contact r1 is turned on. The open side and r2 and r3 are closed.

Therefore, the output of the signal generator OSC is not input to the frequency divider DIV, the driving of the switching transistors Q2 to Q5 by the drive transformer T2 is stopped, and the switching transistors Q2 and Q5 are connected to the base resistors R8 and R9 from the low voltage DC power supply. A base current is supplied to drive through the discharge lamp La, and a DC voltage is applied to the discharge lamp La. Timer circuit TM
Turns off after a certain period of time, turns off the transistor Q8, the relay RY1 returns, and the relay contact r1 closes, r
2, r3 are thrown into the open side. That is, the circuit configuration is the same as that of the drive circuit unit 4 in the circuit diagram of the conventional discharge lamp lighting device of FIG. 2, and a rectangular wave voltage is applied to the discharge lamp La.

[0019]

According to the present invention, when the discharge lamp is started, the operation of the full-bridge inverter circuit for applying a rectangular wave voltage to the discharge lamp is stopped, and the two switching transistors on the diagonal of the full-bridge inverter circuit are driven. Then, apply a DC voltage to the discharge lamp, and provide a discharge lamp DC start circuit that switches the voltage applied to the discharge lamp to a rectangular wave voltage after a certain period of time sufficient to maintain arc discharge. Therefore, the discharge lamp can be surely started.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device according to the present invention.

FIG. 2 is a circuit diagram of a conventional discharge lamp lighting device.

[Explanation of symbols]

 1 power supply circuit section 2 step-down chopper circuit section 3 full bridge inverter circuit section 4 drive circuit section 5 igniter circuit section

Claims (1)

[Claims] 1. A DC power supply unit, a step-down chopper circuit unit for controlling the DC power supply voltage to a required lamp power to output a DC voltage, and applying a DC voltage output to both ends of a discharge lamp while inverting the polarity of the DC voltage. In a discharge lamp lighting device having a full-bridge inverter circuit section for lighting a rectangular wave, a drive circuit section for driving a switching transistor of the full-bridge inverter circuit section, and an igniter circuit section for applying a high-voltage pulse to the discharge lamp when the lamp is started. , The drive circuit section stops the operation of the full-bridge inverter circuit that applies a rectangular wave voltage to the discharge lamp at the time of starting the discharge lamp, and the direct-current power supply with the two diagonal switching transistors of the full-bridge inverter circuit is provided separately. Driven to apply DC voltage to the discharge lamp and it is in a state sufficient to maintain arc discharge. A discharge lamp lighting device, comprising: a discharge lamp DC starting circuit that switches the voltage applied to the discharge lamp to a rectangular wave voltage after a lapse of time so as to start the operation of the full-bridge inverter circuit.