Regulation of hot restrike pulse intensity and repetition

Abstract

Included in a ballast circuit arrangement for a gas discharge lamp is a ballast transformer arrangement receptive of an input power signal and providing an output, ballast voltage. Further included is a pulse transformer having a secondary winding in serial circuit with the lamp for impressing a high voltage, hot restrike starting pulse across the lamp. A bypass capacitor is coupled to the ballast transformer for being charged by the ballast voltage. A hot restrike starting circuit for pulsing a primary winding of the pulse transformer comprises a serially connected starting capacitor and resistor coupled across the bypass capacitor; and a circuit for discharging the starting capacitor including, in serial circuit, the primary winding of the pulse transformer and a current switch having a control electrode responsive to a control signal. A trigger circuit for supplying such control signal comprises a serially connected trigger capacitor and resistor coupled across the starting capacitor; a circuit for discharging the trigger capacitor including a first voltage-breakover switch and producing the mentioned control signal when the first voltage-breakover switch becomes conductive; and a second voltage-breakover switch in serial circuit with the trigger resistor, between the trigger and starting capacitors. The foregoing arrangement provides multiple, consistently high, hot restrike pulses for restarting the lamp.