Abstract: Provided is a power factor correction circuit capable of reducing ringing sound of a transformer produced when an overshoot protection is effected. An output voltage control circuit performs constant voltage-control such that capacitor charge voltage of an output capacitor corresponds to a first voltage value, and when the capacitor charge voltage of the output capacitor reaches a second voltage value higher than the first voltage value, an overvoltage detecting unit detects the second voltage value. Further, a current limiting unit detects a value of a switching current through a switching element, and determines a limiting value of the level of the switching current. Then, the switching current is limited to the limiting value, and when an overvoltage detecting unit detects the second voltage value, a limiting value changing unit causes the current limiting unit to change the limiting value to decrease the value of the switching current.

Abstract: Provided is a power factor correction circuit capable of reducing ringing sound of a transformer produced when an overshoot protection is effected. An output voltage control circuit performs constant voltage-control such that capacitor charge voltage of an output capacitor corresponds to a first voltage value, and when the capacitor charge voltage of the output capacitor reaches a second voltage value higher than the first voltage value, an overvoltage detecting unit detects the second voltage value. Further, a current limiting unit detects a value of a switching current through a switching element, and determines a limiting value of the level of the switching current. Then, the switching current is limited to the limiting value, and when an overvoltage detecting unit detects the second voltage value, a limiting value changing unit causes the current limiting unit to change the limiting value to decrease the value of the switching current.