Patent ID: 8643338

Claim:
A power supply circuit using a rechargeable battery comprising: an over-discharge protection circuit interposed in a current supply path from a rechargeable battery to a load circuit, wherein the over-discharge protection circuit stops a supply of a current from the rechargeable battery to the load circuit if the voltage of the rechargeable battery becomes less than a predetermined value; a connection switching unit connected to the rechargeable battery and connected to an input side of the over-discharge protection circuit, wherein only if the connection switching unit is manipulated, the connection switching unit is in a connected state in which the current is supplied to the over-discharge protection circuit; a power supply control circuit connected between the load circuit and an output of the over-discharge protection circuit, wherein the power supply control circuit controls a supply of the current to the load circuit; and a logic circuit connected to the connection switching unit, wherein the logic circuit controls the over-discharge protection circuit and the power supply control circuit in accordance with the manipulation of the connection switching unit, wherein if the connection switching unit changes to the connected state, the current starts to be supplied from the rechargeable battery to the over-discharge protection circuit, the logic circuit, and the power supply control circuit, wherein if the connection switching unit changes to a non-connected state from the connected state, the supply of the current to the over-discharge protection circuit, the logic circuit, and the power supply control circuit is maintained, and the supply of a current to the load circuit is started by supplying the current from the power supply control circuit to the load circuit, and wherein if a voltage of the rechargeable battery drops while the current is supplied to the load circuit, the over-discharge protection circuit stops the supply of the current from the rechargeable battery and maintains the stopped state.