A power management circuit includes an input, a switch circuit, a first control unit, a second control unit, and a voltage conversion circuit. The input is connected to a load and receives a first direct current (DC) voltage from an external power circuit. The switch circuit is connected between the load and a battery. The first control unit is configured to control whether the switch circuit is switched on or off, based on the first DC voltage and an output voltage of the battery. The voltage conversion circuit is configured to convert the first DC voltage into a second DC voltage and output the second DC voltage to charge the battery. The second control unit is configured to control whether the voltage conversion circuit converts the first DC voltage into the second DC voltage for charging the battery, based on the first DC voltage and the output voltage.