| 摘要 |
PROBLEM TO BE SOLVED: To provide a synchronous rectification switching power supply device of a flyback type that is reduced in the number of part items and also reduced in loss, and can prevent the penetration of a current and self-oscillation irrespective of the abrupt change of a load and types of external apparatuses connected between output terminals. SOLUTION: An inverter transistor Q1 is arranged between input terminals 11, 12, and a synchronous rectification device TR1 is arranged between a secondary winding N2 and the output terminals 13, 14. The synchronous switching power supply device comprises: a different power supply 16 that is charged by the switching of the inverter transistor Q1; a control circuit 18 that supplementally turns on and off the synchronous rectification device TR1 and the inverter transistor Q1; and a switch element TR2 that turns off the synchronous rectification device TR1. The different power supply 16 is provided with a capacitor C6 that is charged by an auxiliary winding N3. A transistor TR3 is also provided for turning the synchronous rectification device TR1 when an output voltage of the different power supply 16 is lowered to a certain value or lower by comparing the output voltage of the different power supply 16 and an output voltage of the output terminal 13. COPYRIGHT: (C)2006,JPO&NCIPI
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