| 摘要 |
The present invention, by connecting an operational amplifier to a midpoint between a plurality of serially connected battery cells constituting the secondary battery, provides a charging circuit for a secondary battery, which is capable of inhibiting a charge/discharge current from flowing to the midpoint and an input/output current from flowing from the midpoint to each battery cell. The charging circuit has disposed therein excess voltage detectors 4 to 6 for detecting whether the voltage of each of the three lithium ion battery cells 1 to 3, by which a battery is constituted, is an excess voltage, and a charging controller 7 for determining an overcharge state of each battery cell on the basis of the voltages detected by the excess voltage detectors 4 to 6 and then controlling ON/OFF of a charging switch part 8. Voltage followers 101, 102 constituted by an operational amplifier, NPN transistor, and the like are connected to the midpoint between the battery cell 1 and the battery cell 2 and the midpoint between the battery cell 2 and the battery cell 3, respectively. The outputs of the voltage followers 101, 102 are configured as the grounds of the excess voltage detectors 5, 6, respectively.
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