Patent ID: 8120262

Claim:
A circuit for driving a plurality of lamps including a first to a 2N th lamp, wherein N is an integer and at least 2, comprising: a switch circuit operable for converting an external DC electric power into a first AC electric power; a first transformer having a primary winding and a secondary winding, wherein said primary winding of said first transformer is coupled to said switch circuit and is operable for receiving said first AC electric power and for energizing said secondary winding of said first transformer so as to generate a second AC electric power from said secondary winding of said first transformer to energize said plurality of lamps; a second transformer having a primary winding and a secondary winding, wherein said primary winding of said second transformer is coupled to said primary winding of said first transformer in parallel and is operable for receiving said first AC electric power and for energizing said secondary winding of said second transformer, wherein said secondary winding of said second transformer is coupled to said secondary winding of said first transformer in series so as to generate a third AC electric power from said secondary winding of said second transformer to energize said plurality of lamps; and a plurality of balance chokes including not more than (N−1) balance chokes, each of said balance chokes having a first winding and a second winding, wherein said plurality of lamps are paired to form a plurality of pairs of lamps, wherein each of said pairs of lamps comprises a first lamp and a second lamp which are coupled to each other in series, and wherein said first winding and said second winding of a K th balance choke are coupled between two lamps of a K th pair of said pairs of lamps in series and between two lamps of a (K+1) th pair of said pairs of lamps in series, respectively, so as to balance currents flowing through said plurality of lamps, wherein K=1, 2, . . . , (N−1), wherein each of said pairs of lamps further comprises a first capacitor coupled between said first transformer and said first lamp, and a second capacitor coupled between said second transformer and said second lamp, wherein said first capacitor, said first lamp, said second lamp and said second capacitor are coupled in series, wherein said first capacitor has a first end directly connected to said secondary winding of said first transformer and has a second end directly connected to said first lamp, and wherein said second capacitor has a first end directly connected to said secondary winding of said second transformer and a second end directly connected to said second lamp.