disclosure includes a control method for over voltage protection , suitable for a power converter . the power converter has a rectifier for rectifying an alternative - current voltage into a direct - current input voltage . the direct - current input voltage is sensed and determined whether it locates in a valley . a detection voltage is provided , capable of representing the direct - current input voltage . the detection voltage is compared with a predetermined reference voltage . when the detection voltage exceeds the predetermined reference voltage and the direct - current input voltage is in the valley , an ovp signal is provided to stop the power conversion of the power converter .