DENSHISHIKIDENRYOKURYOKEI

摘要

PURPOSE:To enable the minimizing of a voltage drop of a power source for backup even when a power failure occurs while a periodical discharge of a lithium battery is performed. CONSTITUTION:A power failure detection circuit comprising a comparator 14 and a power failure compensation circuit comprising a microcomputer 12 and an AND circuit 15 are arranged and a power source 6 for backup is discharged periodically in a normal operation based on an output of the power failure detection circuit. During a power failure, the periodical discharging of the backup power source 6 is stopped with the power failure compensation circuit. Thus, there is no duplication of the power failure and the periodical discharge thereby enabling the checking of a voltage drop to the minimum.