CONTROL CIRCUIT IMPLEMENTING A RELATED METHOD FOR CONTROLLING A SWITCHING POWER FACTOR CORRECTOR, A PFC AND AN AC/DC CONVERTER

摘要

A control circuit controls a switching power factor corrector based on switch off-time modulation by controlling the input electric charge during on-time. The circuit includes a charge current generator that generates charge current as a replica of a current sense signal amplified with a gain corresponding to the square of peak value of a rectified input voltage, a loop capacitor charged with the charge current during on-time intervals and discharged with a discharge current during off-time intervals, a discharge current generator that generates the discharge current proportional to a product of a comparison voltage and a difference between a regulated output voltage and the rectified input voltage, and a PWM modulator that senses a charge voltage of the loop capacitor, turns on the switch for an on-time duration in response to detecting that the charge voltage nullifies, and turns off the switch when the on-time duration has elapsed.

主权项

1. A control circuit for controlling a switching power factor corrector that includes input terminals configured to receive a rectified input voltage, output terminals configured to provide a regulated output voltage, a switched network including an inductor and a power switch coupled to said input terminals and to said output terminals, and a sensing circuit configured to generate a current sense signal representing a current through the inductor during on-time intervals of the power switch, said control circuit comprising:
a charge current generator circuit configured to generate a charge current as a replica of a current sense signal amplified with a gain corresponding to the square of peak value of a rectified input voltage, a loop capacitor configured to be charged with said charge current during the on-time intervals and to be discharged with a discharge current during off-time intervals of the power switch, a discharge current generator circuit configured to be coupled to said loop capacitor during the off-time intervals and generate said discharge current proportional to a product of a comparison voltage and a difference between the regulated output voltage and the rectified input voltage, and a PWM modulator configured to sense a charge voltage of said loop capacitor, turn on said power switch for an on-time duration in response to detecting that said charge voltage nullifies, and turn off said power switch when said on-time duration has elapsed.