| 摘要 |
PROBLEM TO BE SOLVED: To provide a DC-DC converter of a synchronous rectifying circuit system which has simple circuit configuration and a high reliability. SOLUTION: The DC-DC converter is provided with a first transistor Q1 for converting a first DC voltage V1 into an AC voltage by switching the DC voltage with a specified frequency, a switching control circuit 1 which on/off- controls the first transistor Q1, a first coil L1 which stores energy according to the source voltage of the first transistor Q1, a capacitor C2 connected between the other end of the first coil L1 and a common terminal, a second transistor Q2 for synchronous rectification, and a second coil L2 coupled magnetically to the first coil L1 with its polarity reverse to the first coil L1. Component costs can sharply be reduced, since on/off control of the second transistor Q2 is performed with the second coil L2 coupled magnetically to the first coil L1, in place of performing the control with a controlling IC for exclusive use.
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