Patent ID: 8627121

Claim:
A power management circuit for an electronic device, comprising: a regulator that converts an input voltage into a corresponding rated voltage, the regulator comprising: an enable pin that receives a voltage signal to enable or disable the regulator according to the voltage signal; and an output pin that selectively outputs the rated voltage; and a protection circuit electrically connected to the output pin, wherein 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; the protection circuit comprises a first field effect transistor (FET), a second FET, a first bias resistor, and a second bias resistor, the drain of the first FET is electrically connected to the output pin, the second bias resistor is electrically connected between the source and the gate of the first FET, the drain of the second FET is electrically connected to the source of the first FET, and the second bias resistor is electrically connected between the drain and the gate of the second FET.