| 摘要 |
PROBLEM TO BE SOLVED: To reduce exchange loss of power supply which results from commutating FET. SOLUTION: This synchronous rectifying circuit is provided with an FET for supplying the DC power source 1 to the coil P of a transformer 4, when a rectangular waveform is impressed to the gate and the source-to-drain is conductive, an FET7 in the rectifying side which becomes conductive with a forward bias voltage induced in a coil S of the transformer 4 and charges a capacitor 11 via a choke coil 10, an FET8 in the commutation side for making nonconductive the FET7 on the rectifying side with an inverse bias of the flyback voltage generated in the coil S of the transformer 4, when the FET3 is non conductive and charging the capacitor 11 with an reverse electromotive force from the choke coil 10, moreover, an FET9 for auxiliary switch for connecting the gate to the input side of the choke coil 10 and also connecting the drain and source between the gate and source of the FET8 for commutation, and a drive circuit 14 for supplying a DC voltage to the FET9 of the auxiliary switch.
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