Patent ID: 7154229

Claim:
A ballast for powering at least one gas discharge lamp, the ballast comprising: a current-fed resonant inverter adapted for connection to the at least one gas discharge lamp and operable to provide a lamp power to the lamp, the lamp power having a first value and a second value, wherein the second value is less than the first value; and a load shed circuit coupled to the inverter and operable, in response to a load shed command, to cause to the inverter to reduce the lamp power from the first level to the second level, wherein: the current-fed resonant inverter comprises: a pair of input terminals adapted to receive a substantially direct current (DC) voltage; a first output terminal and a return output terminal, wherein the first output terminal and the return output terminal are adapted for connection to the lamp; and a first ballasting capacitor and a return ballasting capacitor, wherein the first ballasting capacitor is coupled to the first output terminal, and the return ballasting capacitor is coupled to the return output terminal; and the load shed circuit comprises: an isolation circuit adapted for coupling to a load shed receiver; and a bidirectional switch coupled to the isolation circuit, the bidirectional switch including first and second output connections coupled in parallel with the return ballasting capacitor.