Provided are semiconductor elements 107A, 107B, and 107C that allow a current to flow that is at most a maximum current determined by the level of control signals VGA, VGB, and VGC and that depends on the difference between the voltage of a DC power supply BA and the charging voltage of a capacitor 102, a controller 105 that outputs a control signal to each semiconductor element, and a temperature detection circuit that detects the temperature of each semiconductor element. Until a predetermined time elapses after the electric circuit is closed, the controller 105 adjusts the level of each control signal based on the temperature detected by the temperature detection circuit so that current through the electric circuit does not exceed a current limit, and after the predetermined time period elapses, the controller 105 adjusts the level of each control signal so that current through the electric circuit is allowed to exceed the current limit.