| 摘要 |
A power source 13 having rechargeable batteries 1 is suitable as a back-up power supply. The power source 13 has a voltage boost circuit 2 to recharge the batteries 1 at a higher voltage than the mains supply 5. A voltage difference is developed between the negative input side 2c and the negative output side 2d of the voltage boost circuit 2. The negative input side 2c is connected to the negative side of the power source 5, and the negative output side 2d is connected to the negative side of the rechargeable batteries 1. The load FET 3 is an n channel FET and is connected between the negative input side 2c and the negative output side 2d of the voltage boost circuit 2. The control circuit 4 maintains the load FET 3 in the OFF state to cut-off conduction when there is no power outage, and switches the load FET 3 ON to supply power to the load 12 from the rechargeable batteries 1 during a power outage. The power source 13, having an n channel FET 3, is cheaper than the conventional power source which uses a p channel FET, yet avoids using a special voltage-boosted supply to the FET 3 gate, and can supply a high voltage, high current power to a load 12. |
