Patent ID: 8907648
Filing Date: 2014-12-09
Classification: H05B

Abstract:
1. A power factor correction circuit receiving rectified power obtained by rectifying AC power and correcting the power factor of the rectified power, the power factor correction circuit comprising: an inductor coupled to the rectified power; a power switch operating to control a current of the inductor (inductor current); and a control circuit generating a feedback-related signal according to a feedback signal, and generating an operation signal to control the power switch according to the feedback-related signal, a current sensing signal relating to the inductor current, and a first reference signal, wherein the control circuit generates a second reference signal according to the first reference signal to determine an upper limit of the inductor current, and the control circuit compares the current sensing signal with the second reference signal; when the current sensing signal is not lower than the second reference signal, the power switch is turned off so that the inductor current is kept not higher than the upper limit; wherein the control circuit includes: a sample circuit generating a ratio signal according to the rectified power; a feed-forward circuit generating a square signal according to the ratio signal; a voltage-to-current converter generating a current signal according to the square signal; a first ramp signal generator generating a first ramp signal according to the current signal; a first PWM signal generator generating a PWM signal, wherein the PWM signal is generated according to the first ramp signal and the feedback-related signal; a calculation circuit multiplying the feedback-related signal with the first reference signal to generate the second reference signal; a current limiter circuit generating a chop signal, wherein the chop signal is generated according to the current sensing signal and the second reference signal; and a switch operation circuit generating the operation signal according to the PWM signal and the chop signal, wherein the operation signal controls the power switch to keep the inductor current not higher than the upper limit.