| 摘要 |
A switching power supply with a high power-conversion-efficiency is obtained by further reducing a loss occurring in a transistor rectifying element. A driving transistor Q3 is arranged between a base of a transistor Q2 as the rectifying element and the ground. A driving signal is inputted from a connection point of the transistor Q2 and a choke coil L1 generating a flyback voltage to the base of the driving transistor Q3, and an ON ad OFF operation of the transistor Q2 is caused to synchronize with an ON ad OFF operation of the switching transistor Q1, thereby preventing a leakage of the current in direction of the base from the collector of the transistor Q2 when it turns off, reducing the loss of the transistor rectifying element and then, improving the power conversion efficiency of the switching power supply.
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