Patent ID: 8183839

Claim:
A switching power source system, comprising: a rectifier circuit configured to carry out full-wave rectification of an AC power source to obtain a pulsating output; a switching device configured to turn a current flowing in an inductor connected to the rectifier circuit on and off; a capacitor configured to smooth the current to obtain a DC output; a first signal producing circuit producing a first threshold value signal in phase with an input voltage, with a waveform similar thereto and having an amplitude proportional to an amount of an error voltage in an output voltage of the DC output; a second signal producing circuit producing a second threshold value signal based on the first threshold value signal; a current range detecting circuit configured to detect whether the current becomes an upper limit value or a lower limit value by comparing the current with the first threshold value signal and the second threshold value signal; and a switching control circuit configured to set the switching device to be turned on or turned off according to a result of the current range detecting circuit and to adjust a timing of at least one of turning on and turning off of the switching device.