PURPOSE: To reduce power loss in a converter by disabling a switching element, when a load deciding means decides that no load is connected to the output side, thereby stopping conversion of electrical characteristics.

CONSTITUTION: When no load is connected to the load terminal of a voltage converting section 5, output of a control circuit 15 goes Low to turn an analog switch 14 OFF. Consequently, power transistors Q1, Q2 are prevented from switching thus preventing DC-DC conversion itself at the voltage converting section 5. When a load is connected to the load terminal of the voltage converting section 5, output of the control circuit 15 goes High to turn the analog switch 14 ON thus allowing switching of the power transistors Q1, Q2 at the voltage converting section 5.