| 摘要 |
PROBLEM TO BE SOLVED: To correctly measure a charged state of a battery by generating a voltage signal corresponding to a current of the battery, forming a digital model of the charged state from an integrated value of the voltage signal and inverting an integration direction cyclically. SOLUTION: A battery 10 is connected to a charger input part 11 and a load 12 via a resistor 13. An operational amplifier 14 generates a voltage signal corresponding to a time integration of a signal voltage proportional to a current of the battery 10 generated at the resistor 13. A window detector circuit including comparators 18-20 and resistors 21-24 connected in series is connected to the operational amplifier 14. When an output of the window detector circuit reaches an upper limit threshold value, a lower limit threshold value and a middle voltage level, the circuit feeds an input signal to an ASIC (application specified integrated circuit) 25. The ASIC 25 processes the signal and controls an inverting switch device comprising switch devices 26, 27 and a reset switch device comprising switch devices 28, 29. An offset voltage is compensated for by inverting an integration direction in the middle of each measurement cycle in this constitution.
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