Patent ID: 8638039

Claim:
A discharge lamp ballast comprising: an inverter circuit including first and second pairs of four switching elements in a full bridge configuration, and a resonant circuit having a resonant frequency connected between output terminals of the switch pairs, the inverter circuit further adapted to output AC power for driving a discharge lamp; and a control circuit adapted to control switch states of the switching elements and thereby to generate the output AC power, wherein the control circuit during a starting operation is adapted to control the inverter switching elements for a predetermined time so as to make an operating frequency of the output AC power sufficiently close to the resonant frequency of the resonant circuit, wherein a high voltage is generated for igniting the discharge lamp, and the control circuit is further adapted to control the inverter switching elements in the starting operation so as to periodically and alternately repeat a state of turning on the switching elements in one of the first or second sets of switching elements, respectively, and turning off the switching elements in the other set, respectively, and a state of turning on only one of the switching elements in the other set and turning off the remaining three switching elements, respectively, wherein a DC component is generated in the output voltage during the starting operation.