| 摘要 |
PROBLEM TO BE SOLVED: To prevent a synchronous rectifying device from being broken, by reducing counter voltage applied to a gate of a synchronous rectification element such as an FET when the synchronous rectification element is turned off. SOLUTION: A Zener diode D1 and a diode D2 are provided in series between the gate and a source of FETQ2. The Zener voltage of the Zener diode D1 is set so as to be less than counter withstand voltage between the gate and the source of FETQ2. When a main switch Q1 is on, the counter voltage applied between the gate and the source of FETQ2 can be restrained so as to obtain less than Zener voltage. Therefore, the voltage more than the withstand voltage is not applied between the gate and the source of FETQ2. Thus, the FETQ2 as the synchronous rectification element can be prevented from being broken. COPYRIGHT: (C)2004,JPO&NCIPI
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