| 摘要 |
PROBLEM TO BE SOLVED: To enable sufficiently obtaining effects of loss reduction by incorporating a synchronous rectification element, and to prevent an erroneous operation of the synchronous rectification element due to voltage applied from the outside. SOLUTION: When a main switching element Q1 is turned on during ON period of a switching element Q5 constituting a driving circuit 21, i.e. during rectification and when the switching element Q1 is shifted during OFF period of the switching element Q5, i.e. during a circulating period, a synchronous rectification element Q3 is turned on based on a reset voltage of a transformer T2. As described above, since the synchronous rectification elements Q3, Q4 are continuously being turned on, the effects of loss reduction by incorporation of the synchronous rectification elements Q3, Q4 can be sufficiently obtained. Also, since the synchronous rectification elements Q3, Q4 perform switching operations upon receiving signal supply from driving circuits 21, 22, erroneous operations of the synchronous rectification elements Q3, Q4 can be prevented. COPYRIGHT: (C)2008,JPO&INPIT
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