A power converter includes at least one electric control switch, an electric current detecting and converting unit, a power controller, and a voltage detecting and controlling unit at the primary side; and a synchronous rectifying circuit, two MOSFETs, and an oscillating loop. During the actual operation, electric current detecting and converting unit outputs an AC voltage signal to the power controller and outputs a DC voltage signal to the voltage detecting and controlling unit, and then voltage detecting and controlling unit compares with a reference voltage to turn off the synchronous rectifying circuit at the no-load mode and to rectify via a body diodes of the MOSFETs. Accordingly, the power converter can reduce the power wastage at the no-load mode to be energy-saving.