Patent ID: 8320144

Claim:
A power factor correction circuit provided with a boost circuit including a first inductor which is electrically connected at a first end thereof to an input terminal and is electrically connected at a second end thereof to a switch, the power factor correction circuit comprising: a second coil coupled with the first inductor for allowing a second coil voltage to be induced by the first inductor; and a switching control unit for receiving the second coil voltage and an output voltage of an output terminal of the power factor correction circuit, turning on the switch using the second coil voltage when current flowing through the first inductor becomes zero from positive, generating a second control voltage by adjusting a first control signal corresponding to the output voltage depending on the second coil voltage when the switch is turned on, and turning off the switch by comparing the second control voltage with a reference voltage, wherein the switching control unit comprises: a first comparator for receiving the second coil voltage, comparing the second coil voltage with the reference voltage, and generating a switch turn-on signal when the second coil voltage becomes lower than the reference voltage; an output voltage controller for receiving the output voltage of the output terminal and outputting a first control voltage for controlling the turning off of the switch; a control voltage modifier for receiving the second coil voltage and the first control voltage of the output voltage controller and outputting the second control voltage whose waveform is modified using the second coil voltage; a ramp generator for generating a ramp waveform voltage; and a second comparator for comparing the second control voltage of the control voltage modifier with the ramp waveform voltage, and generating a switch turn-off signal when the ramp waveform voltage becomes equal to the second control voltage.