| 摘要 |
PURPOSE:To prevent a backup battery from being completely discharged by controlling a switch unit to supply a power to a load when the voltage of the backup battery is higher than a reference voltage and to cut a power supply to the load when the voltage of the backup battery is lower than the reference voltage. CONSTITUTION:When a main power supply 2 can not supply a power, a switching transistor 12 continues an ON condition, a power is supplied from a backup battery 4 to a voltage comparator 10 and a backup load 14 is fed via the switching transistor 12. When the backup battery 4 is discharged and a voltage drops, since the voltage of a reference voltage capacitor 8 is higher than that of the backup battery 4, the switching transistor 12 is turned off whereby the power supply to the voltage comparator 10 and the backup load 14 from the backup battery 4 is cut off. |
