Patent ID: 7876060
Filing Date: 2011-01-25
Classification: H05B

Abstract:
1. An electronic ballast comprising: a series half bridge resonant inverter including switches having an output for powering a plurality of gas discharge lamps connected in parallel; a control circuit controlling the inverter switches and having a control input, the control circuit responsive to signals provided to the control input to vary a switching frequency of the inverter switches; a first feedback circuit coupled between the inverter output and the control input, said first feedback circuit generating a referenced control signal provided to the control input to adjust the switching frequency of the inverter switches so that the inverter output provides a substantially constant current to power the plurality of lamps after starting; and a second feedback circuit coupled between the inverter output and the control input, said second feedback circuit generating an error control signal provided to the control input to adjust the switching frequency of the inverter switches when the output voltage exceeds a predetermined value.