High frequency thyristor circuit for energizing a gaseous discharge lamp

Abstract

A circuit for energizing a gaseous discharge lamp at high frequency utilizing a thyristor, preferably an SCR. The energizing circuit for the lamp includes a resonant or tank circuit operating at an appropriate high frequency, preferably above the acoustic resonant frequencies of the lamp, and which also commutates an SCR. The cathode/anode of the SCR is connected to a voltage adjusting network to provide an initiating pulse through the SCR to start oscillations in the resonant or tank circuit when the SCR is gated on and which reduces the applied supply potential to the SCR during its conduction period to ensure non-conductive latching of the SCR when the gate thereto is removed by lengthening the natural commutation interval of the SCR. This permits the SCR to be used as a switch at the high frequencies involved, normally about 60 kHz. The gate of the SCR is connected to a gate energizing/deenergizing network for abruptly rendering the SCR conductive and non-conductive, which network includes a pair of capacitive discharge circuits designed to sequentially place appropriate amounts and polarity of charge onto the gate of the SCR.