| 摘要 |
PROBLEM TO BE SOLVED: To achieve simplification and the reduction of loss in a synchronous rectifying circuit using an MOSFET. SOLUTION: A capacitor C3 of a first series circuit of a diode D6 and the capacitor C3 is charged by using a voltage VQ4 which is applied across a source and a drain of an MOSFET Q4. When the voltage VQ4 becomes zero, electric charges charged in the capacitor C3 are transferred to a capacitor C4 by using a second series circuit of a diode D7 and the capacitor C4. When the voltage VQ4 is applied to the MOSFET Q4, the voltage VQ4 and the charged voltage of the capacitor C3 are applied to a capacitor C5, so that double voltage charging is conducted by the voltage of the applied voltage of the MOSFET Q4. By using the doubled charge voltage as the drive voltage of the MOSFET Q4, the MOSFET can be driven fully in spite of the rectifying circuit having a low output voltage.
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