A multiwinding transformer includes a primary-side winding and a plurality of secondary-side windings. A primary-side bridge circuit is connected between a primary-side DC terminal and the primary-side winding. A plurality of secondary-side bridge circuits are connected between the plurality of secondary-side windings and a plurality of secondary-side DC terminals, respectively. A switching converter variably controls a first DC voltage of the primary-side DC terminal or a second DC voltage of a first secondary-side DC terminal among the plurality of secondary-side DC terminals such that a voltage ratio between the first DC voltage and the second DC voltage is controlled to a constant ratio in accordance with a turns ratio between the primary-side winding and the secondary-side winding corresponding to the first secondary-side DC terminal among the plurality of secondary-side windings.