A power supply circuit includes inductors, capacitors, and switching elements. Ports are electrically insulated from each other. Two switching elements are alternately switched, and two other switching elements are alternately switched. The inductors are wound such that a magnetic flux is generated in the same direction when a phase difference between the switchings of the switching elements is zero. Duties of the switchings of the switching elements are changed equally, and a phase difference between the switchings is changed.