Patent ID: 8324813

Claim:
An electronic ballast comprising: a filament voltage control block comprising first and second switching elements and configured to determine a filament voltage control state; an inverter circuit further comprising an inverter driver having first and second gate drive output terminals; first and second inverter switches, the second inverter switch coupled to the second gate drive output terminal; a gate drive transformer having a primary side coupled to the inverter driver, the gate drive transformer further having a first secondary side coupled to the first inverter switch and a second secondary side coupled to drive the first switching element in the filament voltage control block; wherein the filament voltage control block is effective in a first filament voltage control state to drive the first and second switching elements in the control block and generate a lamp filament heating voltage, and wherein the filament voltage control block is effective in a second filament voltage control state to disable the second secondary side of the gate drive transformer and thereby disable the lamp filament heating voltage.