| 摘要 |
<p>PURPOSE:To attain the effective use of a back-up battery power supply and at the same time to prevent the overdischarge by detecting the voltage of a battery of a back-up power supply and controlling the supply of power to plural divided memory blocks. CONSTITUTION:The detection voltage levels V1 and V2 of the voltage detecting circuits 4 and 6 of a battery 15 are increased with reduction of the DC output Vm of a power unit 11. Then the detection signals Da and Db of both circuits 4 and 6 are set at high levels. Therefore the transistors TR Q2 and Q4 are turned on and then the TR Q1 and Q3 are also turned on. Then the power of the battery 15 is supplied to the memory blocks 13a and 13b. When the battery power supply is carried on and the voltage of the battery 15 drops down to the level V2 of the circuit 6, the signal Db of the circuit 6 is set at a low level. Thus, the supply of power is stopped to the block 13b. As a result, the overdischarge is prevented and at the same time a back-up period can be increased.</p> |
