Patent ID: 7990076

Claim:
Lamp driver circuit ( 400 ) for operating a discharge lamp (La) at a set lamp power, the lamp driver circuit comprising: a DC supply voltage circuit ( 408 ) for generating a DC supply voltage (V DC ); an output circuit for supplying an AC current to the discharge lamp (La), the output circuit comprising an inverter circuit for generating an AC current at an operating frequency from the DC supply voltage; a feedback circuit comprising: an actual lamp power sensing circuit for determining an actual lamp power; a high-speed feedback circuit coupled to the inverter circuit for controlling the operating frequency of the AC current in response to a power difference between the determined actual lamp power and the set lamp power in order to maintain stable lamp operation; and a low-speed feedback circuit coupled to the DC supply voltage circuit for controlling the DC supply voltage in response to the power difference between the determined actual lamp power and the set lamp power in order to control the actual lamp power.