A power management method includes: determining, by a control circuit, whether a first connector is connected to a first power supply and whether a second connector is connected to a second power supply. The method further includes: controlling, by the control circuit, a first conversion circuit to supply power to a battery unit and a system circuit, and computing a second fully-charged condition that is less than a first fully-charged condition when a determining result is yes. The method also includes: determining, by the control circuit, whether power information of the battery unit reaches the second fully-charged condition, and controlling, by the control circuit, a second conversion circuit to convert a second power from the second connector according to the second fully-charged condition, to supply power to the battery unit and the system circuit. A related circuit and electronic device are also provided.