Patent ID: 7187137

Claim:
A ballast for powering at least one gas discharge lamp, comprising: an electromagnetic interference (EMI) filter adapted to receive a conventional source of alternating current (AC) voltage; a full-wave rectifier circuit coupled to the EMI filter; a DC-to-DC converter coupled to the full-wave rectifier circuit, the DC-to-DC converter having a non-operating mode and an operating mode, wherein: (i) during the non-operating mode, the DC-to-DC converter provides an output voltage that is substantially zero; and (ii) during the operating mode, the DC-to-DC converter provides an output voltage that is substantially greater than zero; an inverter coupled to the DC-to-DC converter; an output circuit coupled to the inverter, the output circuit including output terminals adapted for connection to the at least one gas discharge lamp; and a microcontroller coupled to the DC-to-DC converter, the inverter, and the output circuit, wherein the microcontroller is operable, in response to an output ground-fault condition wherein at least one of the output terminals is shorted to earth ground, to direct the DC-to-DC converter to remain in the non-operating mode.