In ignition mode, intermittent short circuit control is implemented such that a short circuit current flows into a current-source-type step-down chopper. Short-circuit current energy primarily accumulates in an inductor provided in the current-source-type step-down chopper. The accumulated energy boosts the output voltage of a DC power supply device by way of the flow of current during the time period until the next short circuit, a multiphase inverter, and a rectifier. The accumulation of current energy due to short circuiting, and boosting operations in which the output voltage is repeatedly boosted due to conduction are used to implement control in which the output voltage applied to a plasma generation device is increased.