A charging circuit and method for charging a power storage device in a power over Ethernet environment are necessary to prevent unnecessary power consumption. Power sourcing equipment continuously supplies power to a connected device after determining that the device is compatible. In order to prevent supply of power after a power storage device attains full charge, a charging circuit may include an interface for supplying electric power; a sensing circuit including a switch in series with a resistor; and a voltage detection circuit. The voltage detection circuit may communicate with the sensing circuit and may output a first signal that turns the switch OFF when the voltage of the power storage device is greater than or equal to a first voltage and may output a second signal that turns the switch ON when the voltage of the power storage device is less than or equal to a second voltage.