Patent ID: 7295452

Claim:
An active power factor correction (PFC) circuit, comprising: a bridge rectifier for receiving an alternating current (AC) input voltage and providing a rectified input voltage; an input inductor coupled to the bridge rectifier; a power switch coupled between the input inductor and a ground; an output diode coupled to the input inductor and the power switch; an output capacitor coupled between the output diode and the ground; and a control circuit for driving the power switch so that the phase angle of the average current through the input inductor is substantially the same as the phase angle of the rectified input voltage, wherein the control circuit suspends the operation of the power switch at a first moment in a first line cycle of the rectified input voltage and then the control circuit resumes the operation of the power switch at a second moment in a second line cycle of the rectified input voltage, the first moment is when the phase angle of the rectified input voltage exceeds a predetermined angle and the switching frequency of the power switch exceeds a predetermined frequency, the time span from the first moment to the end of the first line cycle is substantially as long as the time span from the beginning of the second line cycle to the second moment.