To provide a DC/DC converter which can determine whether input voltage is within an appropriate range or not at early stage.

The DC/DC converter includes a voltage range determining part 33 judging whether voltage obtained by filter-processing inputted DC voltage is within the appropriate voltage range or not, a voltage change rate range determining part 34 determining whether a voltage change rate with which voltage after a filter processing is time-differentiated or not and a control part 38 turning on/off starting switches 23-1 and 23-2 or adjusting a duty ratio of the switching element Q1 in accordance with respective determination results of the voltage range determining part 33 and the change rate range determining part 34.

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