To avoid feeding an excessive current from flowing even if a switching element is turned on carelessly when a primary power supply is connected to a converter.

An output voltage of a converter is acquired by a voltage division circuit 11 and supplied to a switching control circuit 12 so that the driving operation of the switching element Q1 is controlled. As a result, a voltage raised by a coil L1 is given to an output terminal Vout. The switching control circuit 12 is operated by receiving a power voltage Vdd generated by a regulator 13. A Vdd detection circuit 14 is provided to verify a supply status of the power voltage Vdd generated by the regulator 13. When a non-supply status of Vdd is verified, the switching element Q1 is forcibly set at an OFF status by a switching means SW2.