IN-VEHICLE DC-DC CONVERTER

An in-vehicle DC-DC converter includes a gain setting unit that sets a gain to be used for feedback computation, a duty ratio determination unit that determines a duty ratio, and a drive unit that outputs, to a switching element, a PWM signal that is based on the duty ratio to be used determined by the duty ratio determination unit. The duty ratio determination unit includes a computation unit that repeatedly performs feedback computation for calculating a duty ratio of a PWM signal, so as to approximate a voltage value of an output-side conductive path to a target voltage value, based on a voltage value detected by the voltage detection unit and the gain to be used set by the gain setting unit. The gain setting unit sets the gain to be used, based on a voltage value detected by the voltage detection unit.