Power device for rectifier

A power device for a rectifier including a first terminal and a second terminal for connecting an external circuit, and a circuit system locating between the first terminal and the second terminal is provided. The circuit system is electrically connected to the first terminal and the second terminal. The circuit system includes a pre-mold transistor chip and a control device. The pre-mold transistor chip includes a transistor having a first electrode, a second electrode and a third electrode and a first encapsulant for encapsulating the transistor. The first terminal, the second terminal and the control device are respectively electrically connected to the first electrode, the second electrode and the third electrode of the transistor.