Patent ID: 7728570

Claim:
A power factor correction circuit, comprising: a boost converter, having an input terminal, an output terminal and a ground terminal, for transforming a rectified voltage transmitted via the input terminal to a correction voltage transmitted via the output terminal according to a pulse width modulation (PWM) signal; a first capacitor, having a first terminal coupled to the input terminal; a first resistor, having a first terminal coupled to a second terminal of the first capacitor, and a second terminal coupled to the ground terminal; and a boost control unit, coupled to the first terminal and the second terminal of the first resistor, and coupled to the input terminal and the output terminal, wherein the boost control unit generates the PWM signal based on a ramp signal, and adjusts a duty cycle and a frequency of the PWM signal according to a current flowing through the first resistor, the rectified voltage and the correction voltage, wherein the boost control unit comprises: a signal generator, for generating the ramp signal, and adjusting a slope of the ramp signal according to a charging current; and a frequency controller, coupled to the signal generator and the input terminal, for adjusting the charging current according to the rectified voltage.