A method for converting a line voltage to an RMS load voltage in a lamp includes providing a control circuit which includes a switch and a microcontroller that operates the switch to establish an RMS load voltage for the lamp. The load voltage of the lamp is sensed and the sensed load voltage is compared in the microcontroller to a reference RMS voltage. Operation of the switch is adjusted in response to the comparison so that the RMS load voltage is substantially constant at the reference RMS voltage over a first operating range of the line voltage and so that the RMS load voltage decreases with decreasing line voltage at non-zero line voltages less than the first operating range.