| 摘要 |
PROBLEM TO BE SOLVED: To adopt a constitution where the reference electrode of a battery as a charging object is at the ground potential, and to measure the charging current without any influence of the potential rise of the battery. SOLUTION: A current detecting resistance R1 converts a charging current I into a voltage drop at both end parts. A differential amplifier A1 linearly amplifies the voltage drop. The battery B1 (secondary battery) as a charging object and a reference voltage setting circuit (a circuit including Zener diodes D2, D3, resistances R5, R6, a variable voltage source T1 and a differential amplifier A3) set the reference voltage of the differential amplifier A1. A differential amplifier A2 amplifies the output voltage of the differential amplifier A1. A transistor Tr1 converts a potential difference between the amplified output voltage and the reference voltage into a current (detected current). In a current mirror circuit (a circuit including transistors Tr2 to Tr4 and resistances R8, R9), the detected current is inputted and amplified as an output current in a space up to the GND.
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