| 摘要 |
PROBLEM TO BE SOLVED: To provide technology which can protect a synchronous commutation type step-down DC-DC converter from an overvoltage of an output voltage and can avoid the overvoltage of the output voltage without making a circuit structure complicated. SOLUTION: This synchronous commutation type DC-DC converter has a first switching device provided between a power supply and a power storing means for storing power from the power supply, a second switching device provided between the junction of the first switching device and the storing means and the ground, and a control means which controls the first and second switching devices in order to keep the output voltage of the storing means at a constant value. If the output voltage of the storing means exceeds a prescribed voltage, the first and second switching devices are closed to short-circuit a voltage from the power supply and, by utilizing the short-circuited voltage, the input from the power supply is cut off.
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