Patent ID: 7375995

Claim:
A power factor correction (PFC) circuit used in a power supply, which comprises a rectifier unit and a power output unit, wherein the PFC circuit is connected at the back end of the rectifier unit for regulating the phase of a DC current at the back end of the rectifier unit, the PFC circuit comprising: an energy storage inductor, for receiving the rectified DC current and storing energy and discharging; an output diode, electrically connected between the energy storage inductor and the power output unit; a switch unit, parallel connected at the back end of the rectifier unit; a magnetic material; a primary winding, series connected with the switch unit and wound on the magnetic material; a secondary winding, wound on the magnetic material, wherein when the DC current passes through the primary winding, the secondary winding produces an induced current; a sensing resistor, crossed at two ends of the secondary winding for producing a reference voltage when the induced current from the secondary winding passes through the two ends of the sensing resistor; and a pulse width modulation (PWM) unit, for producing a duty cycle for the switch unit according to the reference voltage so as to regulate the phase of the DC current.