Patent ID: 7940011

Claim:
A lamp drive circuit for driving a plurality of lamps including a first lamp and a second lamp, the lamp drive circuit comprising: a power supply circuit including a first output terminal for outputting a first alternate voltage and a second output terminal for outputting a second alternate voltage; and a balance circuit, coupled to the first and second output terminals, for driving at least the first lamp and the second lamp, the balance circuit including: a first coil, having one end coupled to the first output terminal and the other end coupled to the first lamp; a second coil, having one end coupled to the second output terminal and the other end coupled to the second lamp, wherein a voltage across the first coil corresponds to a voltage across the second coil; a first core, a second core, a third coil, having coil turns substantially equal in number to the coil turns of the first coil, the third coil and the first coil both wound around the first core, and a fourth coil, the third coil and the fourth coil forming a closed loop, the coil turns of the fourth coil being substantially equal in number to the coil turns of the first coil, the fourth coil and the second coil both being wound around the second core, wherein the coil turns of the first coil are substantially equal in number to the coil turns of the second coil; a feedback circuit for outputting a feedback signal according to a voltage difference between one end of the third coil and one end of the fourth coil, wherein the power supply circuit further includes: an energy converter for outputting an alternating current signal, a transformer for outputting the first alternate voltage and the second alternate voltage according to the alternating current signal, and a controller for controlling the energy converter to output the voltage level of the alternating current signal according to the feedback signal.