Patent ID: 7462996

Claim:
A method of converting a line voltage to an RMS load voltage in a lamp, the method comprising the steps of: connecting a control circuit to a lamp terminal, the control circuit including a switch and a microcontroller that operates the switch to establish an RMS load voltage for the lamp; sensing a load voltage of the lamp; comparing, in the microcontroller, the sensed load voltage to a reference RMS voltage; and adjusting operation of the switch 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 adjusting operation of said switch so that the RMS load voltage decreases with decreasing line voltage at non-zero line voltages less than the first operating range, wherein the first operating range of the line voltage is defined to include a predetermined normal line voltage, to have a maximum greater than the predetermined normal line voltage, and to have a minimum less than the predetermined normal line voltage, the minimum being defined as a non-zero line voltage at which a load current is a predetermined maximum.