Circuit for driving a gas discharge lamp load

Abstract

A circuit (100) for driving an instant-start fluorescent lamp (102) has an inverter (103, 132) and a series-resonant LC oscillator (146, 152). A capacitor (190) begins charging after power-up of the circuit and when its voltage reaches a certain level causes breakdown of a diac (192), which discharges the capacitor into an inverter transistor (132) to trigger operation of the inverter. Re-triggerring of the inverter is prevented by a diode (194) which subsequently discharges the capacitor cyclically, and by a capacitor (186) which enables a transistor (180) at a predetermined time following power-up. The occurrence of a subsequent fault condition causes a capacitor (210) to charge and to enable a transistor (196) which disables the inverter. Charging of the initiating capacitor (190) is prevented by an open circuit between terminal connectors (160, 162) if the lamp is not present.

Dependencies are inferred from the claim text.