COMPENSATING METHOD FOR BATTERY VOLTAGE READ ERROR DUE TO SUPPLY VOLTAGE VARIATION

摘要

PURPOSE:To compensate the supply voltage variation and the absolute accuracy of an A/D converter for a battery voltage monitoring function itself by compensating the input voltage of the A/D converter through a variable resistor and making adjustments with data after digital conversion. CONSTITUTION:The voltage from a battery is divided by resistances R1 - R3 so as to make the A/D converter in an IC, supplied with a voltage V5, read it. At this time, the voltage division resistance values are so set that the full-charging voltage of the battery does not exceed the control part supply voltage of the IC. Then an adjusting jig which is proportional to the supply voltage variation comes into contact with points A and B and adjustment are made with an external variable resistor R2 so that a read of a digital multimeter V is 0 (V). At this time, the upper voltage of the A/D converter can freely be adjusted by varying the fixed voltage division ratio. Consequently, even if the voltage of the A/D converter for the battery voltage monitoring function varies, the compensation can be performed including the supply voltage variation and the absolute accuracy of the converter itself, the battery voltage can accurately be observed, and software is prevented from malfunction when the voltage is low.