| 摘要 |
PROBLEM TO BE SOLVED: To use a system reset circuit for a battery checking circuit in an equipment controlled by a CPU by using a battery as a power supply. SOLUTION: A capacitor 7 is charged from a battery 2 through a diode 6, and when the capacity of the capacitor 7 exceeds the terminal voltage of a resistor 4 maintained at reference voltage by a constant current source 3, a CPU 1 is reset by a comparator 5 and starts initial operation. When the capacitor 7 is discharged by a transistor(TR) 15 in accordance with the driving of a load 18, the capacitor 7 is reduced up to a level dropped by loading, and when the capacity of the capacitor 7 is reduced less than the reference voltage, the CPU 1 stops its operation and the drive of the load 18 is also stopped. When power supply voltage is recovered due to release from the load the load 18, the output of the comparator 5 is turned to a high level again and the CPU 1 is reset again. Thereby the CPU 1 starts initial operation again. When a manual operation switching means 17 for driving the load 18 is driven at the time of initial operation, the shortage of power supply voltage can be judged and the system reset circuit can be used also as the battery checking circuit. |
