An electronic ballast for a gas discharge lamp includes an adjustable constant current source circuit adapted to convert a direct current input to provide an initial start current and a variably controlled constant current. A coupling transformer circuit is connected to the adjustable constant current source and adapted to couple the initial start current to the gas discharge lamp to provide a corresponding start voltage approximately equal to a strike voltage of the gas discharge lamp and to convert the variably controlled constant current to a square wave current to power the gas discharge lamp thereafter. A current sense circuit is adapted to sense an operating current at the coupling transformer and to provide corresponding current sense information to the adjustable constant current source, wherein said current sense information is used to vary the variably controlled constant current.