The present invention provides a driving circuit for driving a light source. The driving circuit includes a serial-arranged transformers system having multiple primary windings and secondary windings; a first switch conducting current though a first path and a second switch conducting current though a second path. The first path is a first set of primary windings connected in series and the second path is a second set of primary windings connected in series and the first set of primary transformer windings and the second set of primary transformer windings form the dual primary windings of the transformers respectively. Based on the conduction of each switch, a DC voltage source supplies power to the primary windings of the transformers, which in turn powers on the light source connected to the secondary windings of the transformers.