A power management unit, adapted to a wireless power system, includes: a rectifier, converts an AC power received by an input port thereof to a direct-current (DC) voltage outputted by a rectifying output terminal thereof; a first switch, wherein a first protecting capacitor is coupled between one terminal of the input port and a channel thereof; a second switch, wherein a second protecting capacitor is coupled between the other terminal of the input port and a channel thereof; a reference voltage terminal, for providing a reference voltage; and, a comparator, including two input terminals coupled to the rectifying output terminal and the reference voltage terminal respectively, and including an output terminal coupled to both the control terminals of the first switch and the second switch.