A power factor correction circuit comprising: an input diode configured to rectify commercial input power; a choke coil having one terminal connected to the input diode; an output diode having an anode terminal connected to the other terminal of the choke coil; an output capacitor having a positive terminal connected to a cathode terminal of the output diode; a switching element connected between a contact point and a negative terminal of the output capacitor, the contact point locating between the anode terminal of the output diode and the other terminal of the choke coil; and a control circuit configured to control turning on and off of the switching element, wherein a voltage of the commercial input power is boosted, a direct voltage from the output capacitor is outputted, and electricity is supplied to a load side, and the control circuit includes: an output voltage control circuit configured to perform constant voltage-control of a capacitor charge voltage of the output capacitor to be a first voltage value; an overvoltage detecting unit configured to detect a second voltage value to generate a first overvoltage detection signal, when the capacitor charge voltage of the output capacitor reaches the second voltage value higher than the first voltage value; wherein the power factor correction circuit is characterised in that it further comprises: a current limiting unit configured to detect a value of a switching current through the switching element, determine a limiting value of a level of the switching current, and limit the value of the switching current to the limiting value; and a limiting value changing unit configured to cause the current limiting unit to change the limiting value to decrease the level of the switching current based on the first overvoltage detection signal when the overvoltage detecting unit has detected the second voltage value. an input diode configured to rectify commercial input power; a choke coil having one terminal connected to the input diode; an output diode having an anode terminal connected to the other terminal of the choke coil; an output capacitor having a positive terminal connected to a cathode terminal of the output diode; a switching element connected between a contact point and a negative terminal of the output capacitor, the contact point locating between the anode terminal of the output diode and the other terminal of the choke coil; and a control circuit configured to control turning on and off of the switching element, wherein a voltage of the commercial input power is boosted, a direct voltage from the output capacitor is outputted, and electricity is supplied to a load side, and the control circuit includes: an output voltage control circuit configured to perform constant voltage-control of a capacitor charge voltage of the output capacitor to be a first voltage value; an overvoltage detecting unit configured to detect a second voltage value to generate a first overvoltage detection signal, when the capacitor charge voltage of the output capacitor reaches the second voltage value higher than the first voltage value; an output voltage control circuit configured to perform constant voltage-control of a capacitor charge voltage of the output capacitor to be a first voltage value; an overvoltage detecting unit configured to detect a second voltage value to generate a first overvoltage detection signal, when the capacitor charge voltage of the output capacitor reaches the second voltage value higher than the first voltage value; wherein the power factor correction circuit is characterised in that it further comprises: a current limiting unit configured to detect a value of a switching current through the switching element, determine a limiting value of a level of the switching current, and limit the value of the switching current to the limiting value; and a limiting value changing unit configured to cause the current limiting unit to change the limiting value to decrease the level of the switching current based on the first overvoltage detection signal when the overvoltage detecting unit has detected the second voltage value. a current limiting unit configured to detect a value of a switching current through the switching element, determine a limiting value of a level of the switching current, and limit the value of the switching current to the limiting value; and a limiting value changing unit configured to cause the current limiting unit to change the limiting value to decrease the level of the switching current based on the first overvoltage detection signal when the overvoltage detecting unit has detected the second voltage value.