Patent ID: 8278835

Claim:
An electronic ballast for powering one or more fluorescent lamps, the ballast comprising: a primary circuit board further comprising an AC input circuit coupled to receive an AC signal transmitted via an AC mains power line, a supplemental input circuit configured to receive one or more supplemental signals transmitted via a supplemental communications bus, a lamp feedback circuit effective to detect a feedback signal across said one or more lamps, a ballast control circuit effective to generate an output signal for an oscillating inverter coupled to said one or more lamps; and a secondary card detachably coupled to said primary circuit board and selected from a plurality of secondary cards, each of said plurality of secondary cards configured to provide a dimming control signal of a predetermined range and readable by said ballast control circuit, said secondary cards collectively configured to provide dimming control signals in response to each of a digitally addressable interface for providing continuous dimming, an AC power line-coupled demand response interface, analog dimming signals received via said supplemental communications bus, and three-wire phase control signals received via said AC line and said supplemental communications bus; wherein said primary circuit board is configured to interchangeably receive any one of said secondary cards, and wherein said ballast control circuit is effective to generate said output signal in response to said feedback signal, said dimming control signal and a predetermined lamp output value.