本发明提供一种电源转换器以及其控制方法。电源转换器包括变压器、同步整流器以及控制电路。变压器的一次侧接收输入电压，变压器的二次侧产生传感信号。同步整流器耦接于变压器的二次侧。控制电路接收传感信号并侦测其变化斜率，并据以产生控制信号来控制同步整流器进行截止，以于所述电源转换器输出电压。

A power converter and a control method therefor are provided. The power converter includes a transformer, synchronous rectifier and a control circuit. A primary side of the transformer receives an input voltage, and a secondary side of the transformer generates a sensing signal. The synchronous rectifier is coupled to the secondary side of the transformer. The control circuit receives the sensing signal and detects a changing slope of the sensing signal, and accordingly generates a control signal to control the synchronous rectifier to be turned off, so as to regulate an output voltage of the power converter.