Synchronous rectification controller applied to power converter and start-up method for the same in start-up stage

Abstract

A synchronous rectification controller is coupled to a rectification switch at a secondary-side of a power converter, and the rectification switch includes a rectification switch control, first, and second terminal. The synchronous rectification controller includes a driving signal terminal, a power receiving terminal, a transistor, and a start-up control module. The power receiving terminal receives an operating voltage, and when the operating voltage is higher than an operating voltage threshold, the synchronous rectification controller can output a driving signal for driving the rectification switch through the driving signal terminal. When the operating voltage is lower than the operating voltage threshold, the start-up control module limits a cross voltage between the rectification switch control terminal and the rectification switch second terminal to be lower than a first threshold voltage of the rectification switch by turning on the transistor to prevent conduction of the rectification switch.