Patent ID: 7102297
Filing Date: 2006-09-05
Classification: H05B

Abstract:
1. A ballast for powering a lamp load comprising an even number of gas discharge lamps, the ballast comprising: an inverter having input terminals and output terminals, the inverter being operable to receive a substantially direct current (DC) voltage at the input terminals and to provide a high frequency alternating voltage at the output terminals; an output circuit coupled to the output terminals of the inverter, the output circuit having a plurality of output connections adapted for coupling to the lamp load, the output circuit being operable to provide an operating current to each of the even number of gas discharge lamps; a protection circuit coupled to the inverter and the output circuit, the protection circuit being operable to disable the inverter in response to an end-of-lamp-life condition, wherein the end-of-lamp-life condition is characterized by a predetermined imbalance in the operating current provided to each of the even number of gas discharge lamps; and wherein: