| 摘要 |
<p>PURPOSE:To monitor the voltage of a power supply with high accuracy without requiring a highly accurate voltage dividing resistor by storing the output data of a reference power supply as reference data to compare the same with the output data of a user power supply. CONSTITUTION:The reference voltage of the reference power supply connected between power supply terminals 21 is divided by a voltage divider 12 and converted to digital data by an A/D converter to be taken in a CPU 10 and the digital data is stored in the predetermined address of an RAM 20 as reference data VR1 by the writing order from the outside. Next, the data VR1 is multiplied by a coefficient smaller than 1 to prepare reference data VR2which is, in turn, stored in the RAM 20 in the same way. A battery 30 to be used is connected between the terminals 21 and the voltage thereof is divided by the voltage divider 12 to be converted to digital data appropriately or at every predetermined time by the A/D converter 11 to be taken in the CPU 10 to be compared with the data VR1, VR2 stored in the RAM 20 and, when the taken-in data is smaller than VR1 and larger than VR2, an alarm signal is issued and, when said data is smaller than the data VR2, a stop signal is issued. By this constitution, one voltage divider circuit 12 may be used and it is unnecessary to use highly accurate resistors R1, R2 and the A/D converter 11 excellent in rectilinear properties.</p> |
