| 摘要 |
PROBLEM TO BE SOLVED: To surely protect converter and load such as synchronous rectification elements by detecting the state of protective operation against overcurrent or the like, as an astable-insulating DC-DC converter. SOLUTION: The astable-insulating DC-DC converter comprises first and second power switches 3 and 4 on the primary side of a transformer 6. A control IC5 complementally turns on/off the first and second power switches 3 and 4 at on-duty ratio of about 50% in a normal condition. The control IC5 decreases the on-duty ratio of the power switches 3 and 4 when a dropping voltage of a current detection resistor 35 exceeds a threshold value. An integration circuit 37 drops its output voltage if the dropping of the on-duty ratio continues for specified hours to turn on transistors 22 and 23. If the state continues for specified hours, an FET28 is turned on by a charged voltage of a capacitor 26, and the control IC5 stop switching operation. COPYRIGHT: (C)2008,JPO&INPIT
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