| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of overshoot at a light load without increasing its parts count and also to suppress the rise of drive voltage of a switch element for synchronous rectification even at the time of an overcurrent. SOLUTION: When the voltage Vgs to be applied to a resistor 18 gets over threshold Vth, a switch element 14 for synchronous rectification becomes ON and a current Id flows, and when Vgs becomes smaller than Vth, the switch element 14 for synchronous rectification becomes OFF and the current Id ceases to flow. At a light load, Vgs does not reach Vth, and the switch 14 for synchronous rectification is switched off without fail, so overshoot does not arise. Moreover, when the voltage Vsns to be applied to the resistor 21 reaches overcurrent detection voltage Voc at a light load, a control circuit 100 switches off an AC output power source 10 by a control signal so as to protect a main circuit and also protect the switch element 14 for synchronous rectification, too. COPYRIGHT: (C)2007,JPO&INPIT
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