POWER FACTOR CORRECTION CIRCUIT WITH DIGITAL CONTROL SCHEME AND ASSOCIATED CONTROL METHOD

摘要

A PFC circuit having a switching circuit and a control circuit, the control circuit controls an operation mode of the switching circuit based on an input current and a switching frequency of the switching circuit, when the switching circuit works under a continuous current mode, the switching circuit is turned ON when the input current is less than an OFF current reference signal, and when the switching circuit works under a first discontinuous mode or a second discontinuous mode, the switching circuit is turned ON after a turn ON delay time period when the input current is less than the OFF current reference signal.

主权项

1. A control method for controlling a power factor correction circuit, wherein the power factor correction circuit comprises a switching circuit having an input terminal configured to receive an input voltage and an input current, and an output terminal configured to provide an output voltage, the control method comprising:
providing a peak current sampling signal indicative of a maximum value of the input current; providing an input voltage sampling signal indicative of the input voltage; providing an output voltage sampling signal indicative of the output voltage; providing a current reference signal based on the input voltage sampling signal, the output voltage sampling signal and a voltage reference signal; providing a turn ON delay time period based on the peak current sampling signal and the current reference signal; providing a comparison signal via comparing the input current with an OFF current reference signal; determining an operation mode of the switching circuit based on the input current and a switching frequency of the switching circuit, wherein the operation mode comprises a continuous current mode, a first discontinuous current mode and a second discontinuous current mode; and turning ON the switching circuit based on the comparison signal, and turning OFF the switching circuit when an ON-time period of the switching circuit equals a predetermined ON-time period; wherein when the switching circuit works under the continuous current mode, turning ON the switching circuit when the input current is less than the OFF current reference signal, and calculating the predetermined ON-time period based on the input voltage sampling signal; wherein when the switching circuit works under the first discontinuous current mode, turning ON the switching circuit after the turn ON delay time period when the input current is less than the OFF current reference signal, and calculating the predetermined ON-time period based on the input voltage sampling signal; and wherein when the switching circuit works under the second discontinuous current mode, turning ON the switching circuit after the turn ON delay time period when the input current is less than the OFF current reference signal, and calculating the predetermined ON-time period based on the input voltage sampling signal, the current reference signal and the peak current sampling signal.