Patent ID: 7291991

Claim:
An apparatus for driving one or more discharge lamps, the apparatus comprising: a PWM (pulse-width modulation) controller for controlling switch-drivers; at least six switches, wherein every pair of switches are stacked in a totem-pole configuration, forming at least three totem-poles; at least three switch-drivers, wherein to generate PWM signals, each switch-driver turns on or off the two switches of one totem-pole; at least one transformer that includes a primary winding and a secondary winding, wherein the primary winding of the transformer is connected between the outputs of the at least two totem-poles, and wherein the secondary winding of the transformer feeds one discharge lamp or multiple discharge lamps in series, and wherein if there are more than one transformer and more than two corresponding totem-poles, at least one totem-pole is shared by the primary windings of two transformers; and a configuration wherein the PWM controller receives current and voltage feedback from secondary sides of the transformers and wherein the PWM controller controls the phases between PWM signals to regulate current in the secondary windings of the at least one transformer.