| 摘要 |
<p>PURPOSE:To accurately detect the voltage drop despite of the temperature change by using batteries of the same characteristics to both a reference power supply and a starting power supply and detecting the potential difference between both batteries for detection of the voltage drop of the starting power supply. CONSTITUTION:The paper lithium batteries 27 and 28, for example, are used as the power supplies of an IC card. The battery 27 supplies the electric power to drive the IC card; while the battery 28 produces the reference voltage of a comparator 36 which detects the output voltage of the battery 27. The voltage level of the battery 28 is set lower than that of the battery 27. The comparator 36 detects the potential difference between both batteries 27 and 28. Then the detection output is supplied to a status signal generating circuit 37 from the comparator 36 when the voltage of the battery 27 is lowered less than that of the battery 28. The status signal is supplied to a CPU 31 and a display part 25 is driven via a display control circuit 34 to show the voltage drop of the battery 27.</p> |
