Power module includes transformer unit including primary and secondary windings and magnetic core; first and second capacitor units coupled to first terminal of primary winding of transformer unit through first node; first and second external pins respectively coupled to first terminal of first capacitor unit and second terminal of second capacitor unit; first and second switch units coupled to second terminal of primary winding of transformer unit thorough second node; third and fourth external pins respectively coupled to first terminal of first switch unit and second terminal of second switch unit; secondary-side circuit coupled to secondary winding; and fifth and sixth external pins electrically coupled to first and second output terminals of secondary-side circuit, respectively. First external pin is coupled to one of third and fourth external pins selectively.