Abstract: A current resonance type switching power supply circuit in which a power factor and a voltage regulation in the power supply are improved includes switching elements for interrupting either a voltage or a current output from a DC power supply and supplying the output to primary windings of an insulating transformer and a non-insulating transformer. The switching power supply circuit receives a predetermined alternating voltage from the insulating transformer, and is driven by a DC power supply including a rectifying means for rectifying an AC power supply, a decoupling capacitor arranged at an output side of the rectifying means so as to eliminate noise, a secondary winding of the non-insulating transformer, and a smoothing capacitor charged by a charging circuit including a diode and a choke coil.