This invention is provided with: a switching unit comprising a first switching element and a second switching element connected in series; a first power storage element connected in parallel to both ends of the switching unit; a second power storage element connected in parallel to both ends of the second switching element; and a controller for performing on/off control of the first and second switching elements so that a part of the energy charged in the first power storage element is charged and discharged by the second power storage element at least once, and the energy charged in the first power storage element is discharged while being consumed by the first switching element and/or the second switching element.
