An under-voltage protection circuit has a power input terminal connected to a battery, a power output terminal connected to an electronic device, a switch circuit for switching the power supply circuit from the power input terminal to the power output terminal, a control circuit for controlling the switch circuit, and a control voltage generating circuit that generates a first control voltage when the switch circuit is cut off. The control circuit controls the switch circuit in accordance with the first control voltage. The control voltage generating circuit further generates a second control voltage when the switch circuit is conductive, and then the control circuit controls the switch circuit in accordance with the second control voltage.