A DC-DC converter includes a switch, a rectifier, a smoothing circuit, and a control circuit. The control circuit includes an output detection circuit for outputting an error signal, a current detection circuit for outputting a current detection signal in a period in which at least the switch is OFF, a first circuit for outputting a first signal for setting a timing of turning ON of the switch according to a comparison result between the error signal and the current detection signal, and a second circuit for outputting a second signal for setting an ON time of the switch, according to a reduction in output power from the smoothing circuit, so that the ON time of the switch is reduced, and generates the control signal, based on the first and second signals.