Patent ID: 8797015

Claim:
A switching power supply device comprising: a rectifying circuit configured to receive a phase-controlled alternating voltage to rectify to a direct voltage; and a switching operation conversion circuit configured to convert the direct voltage to an output voltage different from the direct voltage, the switching operation conversion circuit including a switching element being of a normally on type and having a main terminal and a first control terminal, the direct voltage being applied to the switching element, a current control element having at least a second control terminal, the current control element configured to turn off the switching element by lowering a potential of the first control terminal than a potential of the main terminal when a current passing through the current control element exceeds a prescribed value, an inductor passing a current when the switching element is of an on-state, and a driving winding configured to control turning on or off the switching element by magnetically coupling with the inductor and supplying an induced voltage to the first control terminal, an end of the driving winding being connected to the inductor, another end of the driving winding being connected to the first control terminal.