| 摘要 |
PROBLEM TO BE SOLVED: To secure necessary voltage detection accuracy by providing a current conversion circuit that has an amplifier and a resistor forming a feedback loop and converts a cell voltage into a current, and an output resistor of which one end is connected to the negative terminal of a battery pack, and the other end is connected to the output of the current conversion circuit, and with which the voltage is detected as the cell voltage. SOLUTION: A feedback loop is formed so that a measurement cell voltage Vc equals a voltage between both ends of a current detection resistor R1. A source current Is flowing through the current detection resistor R1 becomes a drain current Id as it is because the gate current Ig of a P-channel FET is nearly zero. Therefore, the drain current Id flows through an output resistor R2 connected to the negative terminal of a battery pack, a voltage proportional to the cell voltage is generated across it, and the voltage is output on the basis of the negative terminal of the battery pack. In this case, provided that the resistance value of resistor R1 equals that of the resistor R2, the cell voltage is output as the voltage on the basis of the negative terminal of the battery pack.
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