Patent ID: 7598707

Claim:
A power source apparatus comprising rechargeable batteries, a voltage boost circuit to boost power source voltage and supply it to charge the rechargeable batteries, a load FET connected between the rechargeable batteries and the load to control power supplied to the load from the rechargeable batteries when there is no input of power source voltage, and a control circuit to control the load FET ON and OFF; wherein the voltage boost circuit develops a voltage difference between its negative input side and its negative output side, the negative input side is connected to the negative side of the power source, and the negative output side is connected to the negative side of the rechargeable batteries; wherein the load FET that controls power supplied to the load from the rechargeable batteries is connected to the negative side of the rechargeable batteries, and an n-channel FET is used as the load FET; and wherein the control circuit maintains the load FET in the OFF state when there is no power outage, switches the load FET ON during a power outage, cuts-off load FET conduction when there is no power outage, and supplies power to the load from the rechargeable batteries during a power outage.