A method of converting a line voltage to an RMS load voltage in a lamp includes performing phase-control clipping of a load voltage with a phase-control clipping circuit that provides an RMS load voltage to the lamp. Conduction in the phase-control clipping circuit is triggered independently of a line voltage magnitude with a time-based pulse source that defines a conduction angle of the phase-control clipping circuit. The phase-control clipping circuit includes a transistor switch whose gate receives positive polarity signals from the time-based pulse source to trigger conduction of the phase-control clipping circuit.