Abstract: A DC/DC converter includes a control unit for outputting a control signal on the basis of a voltage difference between a DC output voltage and a reference voltage; a switching element which is connected to a line of the DC input voltage, and which becomes ON-state or OFF-state in accordance with the control signal; and a minimum ON-state duration setting unit, e.g., a monostable multivibrator, which defines the minimum ON-state duration of the switching element, when a necessary output electric power is low. Preferably, the converter includes a charge-pumping circuit having two diodes and two capacitors, so as to obtain from one capacitor a driving voltage source for driving an N-channel type field-effect transistor as the switching element.