| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a synchronous rectification type DC-DC converter which prevents the breakage of a circuit by restraining a self-exciting oscillation operation caused by an external voltage or the like inputted from an output terminal at the stop of a primary-side operation, and normally operates at the start of the primary-side operation and also after the start thereof. <P>SOLUTION: A second switch element Q6 which clamps a gate voltage of a rectification-side synchronous rectification element Q2 prevents self-exciting oscillation by restraining the gate charge of the rectification-side synchronous rectification element Q2 when a commutation-side synchronous rectification element Q3 is turned off, by lowering a gate voltage of the commutation-side synchronous rectification element Q3 and a control terminal voltage of the second switch element Q6. When the on-state of the commutation-side synchronous rectification element Q3 is continued for a fixed time or longer due to the stop of the switching operation of a main switch element Q1, a turn-off circuit SW lowers the gate voltage of the commutation-side synchronous rectification element Q3, and prevents the self-exciting oscillation by restraining the gate charge of the rectification-side synchronous rectification element Q2 at a moment when the commutation-side synchronous rectification element Q3 is turned off. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
