ARC lamp igniter apparatus and method
AssigneeIn Focus Systems, Inc.
InventorHenry Frazier Pruett
Life of this patent
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Abstract
An arc lamp igniter circuit (10) employs a resonant inverter circuit (16) to convert low-voltage DC to a relatively high-voltage, 80 kilohertz sinusoidal AC voltage that is rectified and voltage-doubled (42, 44, 46) to about 2,500 volts DC for repetitively charging an igniter capacitor (50) until it discharges through a spark gap (58) and a primary winding (54) of a compact, low-mass igniter transformer (52). A secondary winding (56) of the igniter transformer provides repetitive 20 kilovolt pulses, which are sufficient to ionize a metal halide arc lamp (14), causing it to ignite and produce intense illumination.
Claims19
An apparatus for igniting an arc lamp, comprising:
- an inverter changing a low direct current ("DC") voltage to a substantially sinusoidal alternating current voltage, the inverter including an inverter transformer having a primary winding with a parasitic capacitance and a secondary winding;
- a resonating capacitor electrically connected in parallel with the primary winding and the parasitic capacitance causing the inverter to operate at a resonant frequency of the inverter transformer;
- a voltage-multiplying rectifier circuit electrically connected to the secondary winding of the inverter transformer to develop a high DC voltage;
- an igniter capacitor lightly coupled by a charging resistor to the voltage-multiplying rectifier circuit to develop a high DC voltage charge across the igniter capacitor;
- an igniter transformer having a primary winding that is connected to the igniter capacitor and a secondary winding that is connected to the arc lamp;
- and
- a spark gap electrically connected to the igniter capacitor and the primary winding of the igniter transformer such that the high DC voltage charge across the igniter capacitor discharges through the spark gap and the primary winding of the igniter transformer to couple across the secondary winding of the igniter transformer a high-voltage pulse that ionizes the arc lamp.
A method of igniting an arc lamp, comprising:
- providing an igniter transformer having a primary winding and a secondary winding;
- connecting the arc lamp to the secondary winding of the igniter transformer;
- providing an inverter that changes a low direct current ("DC") voltage to a substantially sinusoidal alternating current voltage, the inverter including an inverter transformer having a primary winding and a secondary winding;
- operating the inverter at a resonant frequency of the primary winding of the inverter transformer;
- connecting a voltage-multiplying rectifier circuit to the secondary winding of the inverter transformer to develop a high DC voltage;
- charging an igniter capacitor from the high DC voltage;
- and
- discharging the igniter capacitor through a spark gap and the primary winding of the igniter transformer to couple a high-voltage ignition pulse into the arc lamp.
Dependencies are inferred from the claim text.