Patent ID: 6947298

Claim:
A switching power source apparatus ( 10 ) that supplies an AC voltage to a step-up reactor ( 5 ), ON/OFF-controls a switching element (Q 1 ) connected to an output of the step-up reactor to provide a stepped-up DC voltage hither than the AC voltage, and outputs the DC voltage, comprising: ON control means for turning on the switching element in a case where a voltage generated at a secondary coil of the step-up reactor becomes lower than a fist reference voltage; error voltage generation means for generating an error voltage made from a difference between a detected value of the output voltage and a second reference voltage; current target value generation means for generating a current target value interlocked with a full-wave-rectified waveform of the AC voltage according to the full-wave-rectified waveform and the error voltage; and OFF control means for turning off the switching element when a current passing through the switching element reaches the current target value, the apparatus characterized by: overvoltage protection means for continuously stopping the operation of the switching element only when an overvoltage greater than a third reference voltage is generated at the secondary coil of the step-up reactor.