Switching power supply

A switching power supply comprising:

• a bridge circuit that includes a plurality of switches, and is configured to convert an input DC voltage into an AC voltage by switching;
• a transformer to whose primary coil the AC voltage converted by the bridge circuit is applied, and that is configured to output the transformed voltage from a center tap between secondary coils of the transformer;
• two second switches for respectively causing two ends of the secondary coils to be brought in contact with and be separated from a fixed electrical potential, and
• a smoothing circuit that smoothes the voltage output from the center tap,
• wherein a rectified DC voltage is output from the center tap by the second switches being respectively switched on/off with control signals synchronized with the switching, and the DC voltage smoothed by the smoothing circuit is output from the switching power supply, and
• wherein the switching power supply further comprising:
• two diodes that are respectively connected to the two ends of the secondary coils, and are configured to cause currents to flow from the two ends;
• a capacitor that is configured to store the currents caused to flow by the diodes;
• and
• a third switch that is connected between the capacitor and the center tap,
• wherein the capacitor is discharged to the smoothing circuit by the third switch being turned on with a second control signal synchronized with the switching.