A ballast circuit includes a control loop to reduce a filament heating voltage below after the lamp filaments have been pre-heated. A filament cutback circuit includes a filament cut-back inductive component magnetically coupled to the resonant inductive component in the inverter to receive a filament cutback control voltage associated with an AC voltage for powering the lamps. During the pre-heating period, the filament cutback control voltage is not high enough to charge a chargeable component to a switch threshold level. However, during lamp ignition, the filament cutback control voltage is increased and charges the chargeable component to the switch threshold level. This causes a switch device to operate in a conductive switch state and the filament cutback circuit suppresses the pre-heat voltage.