SWITCHING POWER SUPPLY

PROBLEM TO BE SOLVED: To provide a switching power supply having a pair of rectifier elements wherein the rectifier elements can be turned on, even during a period when no voltage is induced in the secondary winding, and can be driven at low loss. SOLUTION: In a switching power supply including an output transformer 12 having the secondary winding 12a and an auxiliary winding 12b, a synchronous rectifying circuit 16 having the pair of rectifier elements 20 and 22 and first and second input capacitors 20b and 22b provided individually between the drive terminals and the ground terminals of the pair of rectifier elements 20 and 22, and a smoothing circuit 18, there are provided with charge-holding capacitors 34 and 38 which are charged with the voltage induced in the auxiliary winding 12b and hold the charges; and the charge held by the first input capacitor 20b or second input capacitor 22b and the charge-holding capacitor 34 or 38 move through the auxiliary winding 12b, while the voltage is not output from the secondary winding 12a and the first and second rectifier elements 20 and 22 are simultaneously turned on. COPYRIGHT: (C)2011,JPO&INPIT