Patent ID: 7560874

Claim:
An electronic ballast for powering at least one gas discharge lamp, the ballast comprising: a half-bridge inverter, comprising: first and second inverter input terminals adapted to receive a source of substantially direct current (DC) voltage; first and second inverter output terminals, wherein the first inverter output terminal is coupled to the first inverter input terminal; a first inverter switch coupled between the first inverter input terminal and the second inverter output terminal, the first inverter switch having a base terminal; a second inverter switch coupled between the second inverter output terminal and circuit ground, the second inverter switch having a base terminal, wherein circuit ground is coupled to the second inverter input terminal; a first base-drive circuit comprising a series combination of a first base-drive winding and a first base-drive resistor, the series combination being coupled between the base terminal of the first inverter switch and the second inverter output terminal; a second base-drive circuit comprising a series combination of a second base-drive winding and a second base-drive resistor, the series combination being coupled between the base terminal of the second inverter switch and circuit ground; and an inverter startup circuit operably coupled to the first inverter output terminal, the second base-drive circuit, and the base terminal of the second inverter switch, and operable to provide a starting voltage for initially activating the second inverter switch, wherein the inverter startup circuit is characterized as being devoid of a voltage breakdown device, the inverter startup circuit comprising: a first resistor coupled between the first and second inverter output terminals; a second resistor coupled between the second inverter output terminal and the base terminal of the second inverter switch; and a capacitor coupled between the second base-drive circuit and circuit ground.