Patent ID: 7923942

Claim:
A dimming electronic ballast for operating a plurality of two or more high impedance lamps comprising: an inverter; a first ballast circuit comprising a first lamp output terminal configured to couple a first lamp current from the ballast to a first one of a plurality of two or more high impedance lamps; a second ballast circuit comprising a second lamp output terminal configured to couple a second lamp current from the ballast to a second one of a plurality of two or more high impedance lamps; the first ballast circuit further comprising a first resonant tank circuit coupled between the inverter and the first lamp output terminal; the second ballast circuit further comprising a second resonant tank circuit coupled between the inverter and the second lamp output terminal; the first and second ballast circuits are electrically coupled in parallel; the inverter further comprising circuitry to cause the ballast to selectably operate in a full power mode and in a dimming power mode; each of the first and second resonant circuits comprises a resonant inductor, a resonant capacitor, and a ballast capacitor having respective component values; and wherein the respective component values for the resonant inductor, resonant capacitor, and ballast capacitor in each of the first and second resonant circuits are selected so that when the ballast is connected to a plurality of two or more high impedance lamps, the ballast is functional to provide substantially constant and equal first and second lamp currents when operating in the full power mode, and to provide substantially constant and equal first and second lamp currents when operating in the dimming power mode.