A power management circuit for managing power of an electronic device includes a regulator and a protection circuit. The regulator converts an input voltage into a corresponding rated voltage and includes an enable pin and an output pin. The enable pin receives a voltage signal to enable or disable the regulator, and the output pin selectively outputs the rated voltage. When the electronic device is implemented as a slave universal serial bus (USB) device and the enable pin receives a low voltage signal, the regulator is disabled, and the protection circuit receives an output voltage. When the electronic device is implemented as a USB host and the enable pin receives a high voltage signal, the regulator is enabled, and the output protection circuit outputs the rated voltage.