In-vehicle DC-DC converter

An in-vehicle DC-DC converter that is electrically connected to a first conductive path and a second conductive path, one of the first conductive path and the second conductive path being defined as an input-side conductive path and the other being defined as an output-side conductive path, steps up or down a voltage applied to the input-side conductive path, and outputs the voltage to the output-side conductive path, the in-vehicle DC-DC converter including:

• a voltage conversion unit that includes a switching element that performs an on/off operation in accordance with being supplied with a PWM signal, the voltage conversion unit stepping up or down a voltage applied to the input-side conductive path, through an on/off operation by the switching element, and outputting the voltage to the output-side conductive path;
• a voltage detection unit that detects a voltage value of the output-side conductive path;
• a gain setting unit that sets a gain to be used for feedback computation;
• a duty ratio determination unit that includes a computation unit that repeatedly performs feedback computation for calculating a duty ratio of the PWM signal so as to approximate a voltage value of the output-side conductive path to a target voltage value based on at least a voltage value detected by the voltage detection unit and the gain to be used set by the gain setting unit, and, every time the computation unit performs feedback computation, determines a duty ratio to be used, based on a calculated duty ratio calculated through the feedback computation;
• and
• a drive unit that outputs, to the switching element, a PWM signal that is based on the duty ratio to be used determined by the duty ratio determination unit,
• wherein the gain setting unit sets the gain to be used, based on a voltage value detected by the voltage detection unit.