| 摘要 |
PROBLEM TO BE SOLVED: To provide an isolation DC-DC converter using a synchronous rectifier capable of improving efficiency characteristics. SOLUTION: The isolation DC-DC converter is provided with an on-timing delay circuit which delays the on-timing of a power switch 3 by preventing the on-operation start of the power switch 3 when an on-signal is outputted from a power switch drive circuit inside a control IC 4 to the power switch 3, an early turn-off circuit 16 to turn off the synchronous rectifier 6 in which on/off operations of switching are in reverse to those of the power switch 3 during delaying the on-timing of the power switch 3, and a delay cancellation circuit 17 which immediately cancels the delay operation of the on-timing delay circuit when it has detected that the synchronous rectifier 6 is turned off due to a drop in a gate voltage of the synchronous rectifier 6. When the delay operation of the on-timing delay circuit is conducted continuously even after the turning-off of the synchronous rectifier 6, although loss resulting from the continuous delay operation will occur, the problem of the loss can be prevented by the delay cancellation circuit 17. COPYRIGHT: (C)2004,JPO
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