| 摘要 |
PROBLEM TO BE SOLVED: To execute synchronous rectification with a simple circuit and to enhance economical effects. SOLUTION: The switching power supply is composed of a winding and a synchronous rectification circuit provided with a first diode to discharge exciting energy to be accumulated in the winding. And, a saturable inductor is inserted in series in the first diode and a first switch element having a control electrode is connected in parallel in the synchronous rectification circuit. Also, a second diode is connected between the control electrode of the first switch element and a terminal on the opposite side of a terminal connected to the first diode of the saturable inductor. Further, a second switch element having a control electrode is connected in parallel in the second diode. The control electrode of the second switch element is connected to the terminal to which the first switch element of the saturable inductor is connected. By this, since the direction of a voltage generated in the winding is reversed when the exciting energy is accumulated and when the exciting energy is discharged, the first switch element is turned on by capturing the voltage with the saturable inductor. When reversed, the second switch element is turned on and the first switch element is turned off. As a result, the first switch element is made to execute the synchronous rectification. COPYRIGHT: (C)2004,JPO
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