Power factor correction circuit

A power factor correction circuit comprising:

• a reactor including one end connected to one end of an AC power supply and another end connected to a first main terminal of a control switch;
• a first series circuit in which a synchronous rectification switch and an output capacitor are connected in series to the first main terminal and a second main terminal of the control switch;
• a second series circuit in which a first polarity changeover switch and a second polarity changeover switch are connected in series to both ends of a series circuit of the control switch and the synchronous rectification switch;
• and
• a control circuit that alternately turns on and off the control switch and the synchronous rectification switch so that output voltage of the output capacitor becomes a first predetermined value to control ON time of the control switch so that a peak value of current flowing through the control switch is proportional to input voltage of the AC power supply, and switches the control switch and the synchronous rectification switch according to polarity of input voltage of the AC power supply and switches processing of turning on one of the first polarity changeover switch and the second polarity changeover switch and turning off another one of the first polarity changeover switch and the second polarity changeover switch,
• wherein
• the control circuit turns on and off the control switch and the synchronous rectification switch so as to adjust a reverse excitation amount of reverse excitation of the reactor by causing current flowing through the reactor to flow backward from an output voltage side to an input voltage side, and
• the reverse excitation amount is adjusted to a second predetermined value regardless of the input voltage.