| 摘要 |
PROBLEM TO BE SOLVED: To enable current consumption of a load circuit to be accurately measured without excessively charging a secondary battery. SOLUTION: A backup power supply circuit 20 for a real-time clock circuit 11 includes: a backup power source 20 which is charged by a main power source Vin; a first switch means SW1 interposed between the main power source Vin and a power supply terminal of the real-time clock circuit 11; a second switch means SW2 interposed between the backup power source 20 and the power supply terminal of the real-time clock circuit 11; a first voltage detection circuit 12 which detects a voltage of the main power source Vin and turns off the first switch means SW1 when the voltage is lower than or equal to a first detection voltage; and a second voltage detection circuit 13 which detects the voltage of the main power source Vin and turns off the second switch means SW2 when the voltage is equal to or higher than a second detection voltage. COPYRIGHT: (C)2009,JPO&INPIT
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