JPH05283187A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To reduce the cost and miniaturize a device by constituting a lighting device capable of starting a lamp with a one-stage, high-voltage transformer. CONSTITUTION:A starting circuit is constituted of a resistor R1, a capacitor C2, a switch element SW1, and one transformer T3. When a power source is turned on, a chopper circuit 2 is operated, voltage is applied to the starting circuit 5, and the capacitor C2 is charged at the time constant determined by the resistor R1 and the capacitor C2. When the capacitor C2 reaches the fixed voltage, the switch element SW1 is broken down, and the capacitor C2 is discharged via the primary winding of the transformer T3. A current flows in the primary winding of the transformer T3 to generate voltage, and the voltage corresponding to the winding ratio is generated on the secondary winding. The secondary winding is wound with a flat rectangular wire into one layer, the attenuation of the pulse voltage is small, and the pulse voltage required to light a lamp is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a high pressure discharge lamp used as a light source for an optical device such as a liquid crystal projector, and particularly for a short arc metahalide lamp.

[0002]

2. Description of the Related Art A short arc metahalide lamp (hereinafter referred to as "lamp") has a high starting voltage,
At the time of starting, a particularly high voltage is applied to start the lamp. Further, since the vapor pressure in the arc tube of the lamp is high immediately after the lamp is turned off, a higher starting voltage is required to relight the lamp. Therefore, when the lamp is used as a light source of an optical device, a starting voltage of 10 KV or higher is required in consideration of the restart of the lamp.

FIG. 3 shows an example of a circuit of a conventionally used discharge lamp lighting device. The device comprises a chopper circuit 2 for controlling the electric power of the lamp, a rectangular wave exchanging circuit 3 for stably lighting the lamp, and a starting circuit 4 for starting the lamp.

The chopper circuit 2 is a control circuit (not shown).
Switching transistor Q1 controlled and driven by
And a diode D1, a DC reactor L1, and a smoothing capacitor C1. A DC power supply voltage is input from a DC power supply 1 to a chopper circuit 2, a required lamp power control is performed, and a DC voltage is output. ..

The rectangular wave conversion circuit 3 is composed of switching transistors Q2 to Q5, and a driving circuit (not shown) switches the switching transistors Q2, Q5 and Q.
Alternately turning on Q3 and Q4, while inverting the polarity of the DC voltage output from the chopper circuit 2, the voltage is applied to both ends of the lamp La and the rectangular wave is lit.

The starting circuit 4 includes a resistor R1 and a capacitor C.
2, voltage switching element SSS1, transformer T1, diode D2, capacitor C3, spark gap S
G and a transformer T2. When the power is turned on, the output of the chopper circuit 2 is received, the capacitor C2 is charged with the time constant determined by the resistor R1 and the capacitor C2, and when the breakover voltage of the voltage switching element SSS1 is reached. Via the primary winding on the primary side of the transformer T1,
The capacitor C2 is discharged. Voltage switching element SS
S1 is turned off and the capacitor C2 starts to be charged again.

The capacitor C3 is provided to rectify and smooth the output of the secondary winding of the transformer T1 with the diode D2.
It is charged according to the discharge of the capacitor C2.
When the voltage on the capacitor C3 reaches the breakover voltage of the spark gap SG, the capacitor C3 is discharged through the primary winding of the transformer T2 and the secondary winding of the transformer T2 is pulsed to start the lamp. Voltage is generated. By repeating the above operation, the lamp La starts to be lit, and after the lighting, the lamp voltage becomes equal to or lower than the breakover voltage of the voltage switching element SSS1, and the operation of the pulse circuit is stopped.

[0008]

The transformer T1 is for boosting the primary voltage, and the transformer T2 is for placing the boosted voltage on the winding through which the lamp current can flow. As described above, conventionally, since two high-voltage transformers are used, there is a drawback that the cost becomes high. Further, for safety, it is necessary to secure a sufficient space between the surrounding space and an adjacent device, and there is a drawback that the device becomes large.

An object of the present invention is to provide a discharge lamp lighting device which is low in cost and can be downsized.

[0010]

To achieve this object, in the present invention, in a discharge lamp lighting device having a chopper circuit, a rectangular wave conversion circuit, and a starting circuit, the starting circuit comprises:
A series circuit of a resistor and a capacitor connected to the DC power source end, and a secondary winding composed of one layer of rectangular wire 1
It is configured to include a plurality of transformers and a switch element that breaks over by the voltage of the capacitor and discharges the electric charge of the capacitor through the primary winding of the transformer.

[0011]

When the power is turned on and the chopper circuit operates to supply voltage to the starting circuit, the capacitor is charged with the time constant determined by the resistor and the capacitor. When the capacitor reaches a certain voltage, the switch element breaks down and the capacitor discharges through the primary winding of the transformer. When a current flows through the primary winding of the transformer and a voltage is generated, a high voltage necessary for lighting the lamp is generated in the secondary winding wound in one layer by the rectangular wire.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of an embodiment of a discharge lamp lighting device according to the present invention. Here, the construction and operation of a chopper circuit 2 and a rectangular wave conversion circuit 3 are the same as those of a conventional example, and therefore description thereof will be given. Is omitted. The starting circuit 5 of the present invention includes a resistor R
1, a capacitor C2, a switch element SW1 and a transformer T3. The switch element SW1 breaks down when the capacitor C2 reaches a constant voltage, and is preferably a field effect transistor (FET) having a low resistance value when turned on.

As the transformer T3, there is used one in which the secondary winding 10 is wound in a single layer by a so-called rectangular wire having a rectangular cross section as shown in FIG. Reference numeral 11 is an iron core, 12 is an insulating paper, and 13 is a primary winding. Since the secondary winding is wound in one layer with a rectangular wire, the distributed stray capacitance between layers can be suppressed to a small level, and even if the number of turns on the secondary side is increased, the attenuation of the pulse voltage generated on the secondary side can be suppressed. Therefore, the pulse voltage necessary for lighting the lamp can be obtained without increasing the number of turns more than necessary.

When the power is now turned on and the chopper circuit 2 operates and a voltage is supplied to the starting circuit 5, the capacitor C2 is charged with a time constant determined by the resistor R1 and the capacitor C2. When the capacitor C2 reaches a constant voltage, the switch element SW1 breaks down and discharges from the capacitor C2 via the primary winding of the transformer T3.

When a current flows in the primary winding of the transformer T3 and a voltage is generated, a voltage corresponding to the turn ratio is also generated in the secondary winding. Here, since the secondary winding is wound in a single layer with a rectangular wire, the pulse voltage is less attenuated as compared with the conventional transformer, and it is necessary to use the 1
It is possible to generate a voltage of 0 KV or more.

[0016]

According to the present invention, since the lamp can be started by the one-stage high-voltage transformer, an inexpensive and small discharge lamp lighting device can be realized.

[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 cross-sectional view of a transformer used in the present invention.

FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device.

[Explanation of symbols]

 2 Chopper circuit 3 Rectangular wave conversion circuit 5 Starting circuit

Claims (1)

[Claims] 1. A discharge lamp lighting device having a chopper circuit, a rectangular wave conversion circuit and a starting circuit, wherein the starting circuit comprises a series circuit of a resistor and a capacitor connected to a DC power source end,
One transformer in which the secondary winding is composed of a flat wire in one layer, and a switch element that breaks over by the voltage of the capacitor and discharges the charge of the capacitor through the primary winding of the transformer. A discharge lamp lighting device, comprising: