Patent ID: 7292461

Claim:
A switching power source apparatus comprising: a switching element connected in series with a DC power source through a primary winding of a transformer; a voltage detector configured to detect timing synchronized with a period of voltage free oscillation and output a detection signal, the voltage free oscillation occurring at a gate of the switching element after a flyback period due to parasitic capacitance between terminals of the switching element or optionally added capacitance; a timing corrector configured to estimate timing when the voltage free oscillation substantially reaches a bottom level a second time or later and output an ON start signal at the estimated timing, according to the detection signal from the voltage detector; a controller configured to output an ON control signal to turn on the switching element in response to the ON start signal from the timing corrector; and a driver configured to apply a drive signal to the gate of the switching element and thereby drive the switching element in response to the ON control signal from the controller.