| 摘要 |
PROBLEM TO BE SOLVED: To positively prevent a backward current or a regenerative current in a synchronous rectification type switching power supply. SOLUTION: A transformer 1 transmits primary power to a secondary side. An exciting switch circuit 2 excites a primary winding of the transformer 1. A rectifying switch circuit 3 rectifies an output of the transformer 1. A monitor circuit 20 monitors an input voltage Vin. A control circuit 10 supplies a control signal generated based on an output voltage Vout to the exciting switch circuit 2 and the rectifying switch circuit 3. If the input voltage Vin is below a predetermined value, a control signal supplied to the rectifying switch circuit 3 is shut down, so that the rectifying switch circuit 3 stops. COPYRIGHT: (C)2005,JPO&NCIPI
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