A DC source generates a DC voltage between a positive electrode and a negative electrode. An inductive element and a parallel-connected switch-circuits unit are provided in a conductive path extending from the positive electrode to the negative electrode. The parallel-connected switch-circuits unit includes a plurality of switch circuits connected in parallel with one another. The switch circuit opens and closes the conductive path in accordance with a drive signal inputted from a drive circuit. The drive signal causes the plurality of switch circuits to successively perform an ON operation in which the conductive path is closed and then opened. A pulse voltage generation period in which a pulse voltage occurs in the inductive element continuously follows an ON period which is a duration from when the conductive path is closed to when the conductive path is opened.