ASYMMETRIC FLYBACK CIRCUIT

摘要

PURPOSE: An asymmetric flyback circuit is provided to prevent a dual delay, occurring when a synchronous rectifier is turned off, using an output of a pulse width modulation part. CONSTITUTION: An asymmetric flyback circuit comprises a bridge rectifier(20) which converts an AC power from an EMI filter(10) into a dc power. A voltage doubler(30) maintains the dc voltage from the rectifier(20) at a DC power state. An asymmetric flyback converter(40) performs a zero crossing switching operation to a power flowing in through the voltage doubler(30). A synchronous rectifier(50) rectifies a power induced through a transformer(T1) according to a synchronous signal. A feedback part(100) senses a state of an output voltage of the rectifier(50) to transfer voltage state information to a previous stage. A pulse width modulation(PWM) controller(70) modulates a PWM signal according to the output voltage state of the rectifier(50). A switch gate driver(80) generates a driving signal for controlling the zero voltage switching operation of the converter(40) according to the control signal from the controller(70). An SR gate driver(90) receives a reference voltage signal and the control signal to control a synchronous state of the rectifier(50).