Method and apparatus for high power factor flyback converters

摘要

Apparatus for controlling a power transistor of a power circuit, comprising:a driver circuit having a first input configured to receive a voltage reference signal, a second input configured to receive a subtraction signal, and an output configured to drive the power transistor based on the voltage reference signal and the subtraction signal;a multiplier having a first input configured to receive a first signal based on a feedback signal from the power circuit, a second input configured to receive a second signal receive based on an input voltage to the power circuit and an output configured to provide the voltage reference signal; anda subtraction circuit configured to provide the subtraction signal based on a difference between a third signal based on the voltage reference signal and a sense signal representative of a current flowing through the power transistor,wherein the subtraction circuit comprises:a current generator coupled to the multiplier and configured to generate a capacitor signal based on the voltage reference signal; anda subtractor configured to subtract the capacitor signal from the sense signal and generate the subtraction signal.