PURPOSE: To constitute a power supply whose current capacity is large by a method wherein a bridge rectifying operation is performed by MOS power FETs.

CONSTITUTION: MOS power FETs (TR1 to TR4) which constitute a bridge rectifier 4a and all constituted of N-channel ones, the FETs (TR1, TR4) and the FETs (TR2, TR3) form one set each, and a control signal which is turned on and off repeatedly is applied to gates of the respective sets. Then, an operating current flows in the order of A → C → a source for the TR1 → a drain →E → a load 5 → F → a source for the TR4 → a drain → D → B when the A end of a power-supply transformer 2a is at a positive half cycle, it flows in the order of B → D → a source for the TR3 → a drain → E → the load 5 → F → a source for the TR2 → a drain → C → A when the B end of the power-supply transformer 2a is at the positive half cycle, and rectified electric charges are stored respectively in the load 5. In this case, C, D, E and F represent both ends of the bridge rectifier 4a. Thereby, a large-capacity power supply 1 can be constituted.