In order to reduce the cost of a chopping converter supplying a continuous voltage at the terminals of a load, a circuit with three windings and a single magnetic core is proposed, according to the present invention, which enables the cost and the size of the circuit to be reduced. Since the size of the cells adjacent to the spacer is set smaller than the size of the other cells, the luminance and aperture rate of the panel can be improved. An embodiment may be generally triangle-shaped.