A device designed to reduce temperature rise in its control board. The device includes a switching element; a coil; a smoothing capacitor; an electrical connection member for electrically connecting the switching element with the smoothing capacitor and the coil; a control board that mounts a control element; a control signal line for electrically connecting the switching element with the control board; and a switching element placing portion for placing the switching element thereon. The electrical connection member is arranged between the switching element and the control board; the smoothing capacitor and the coil are arranged, with respect to the electrical connection member, on a side of the switching element; and end surfaces of the smoothing capacitor and the coil are positioned, with respect to the electrical connection member, apart from a plane where the switching element and the switching element placing portion are adjoined together.