| 摘要 |
PROBLEM TO BE SOLVED: To prevent failures effectively in FET due to heating from a parasitic diode, while charging a battery pack including an anomalous battery, in safety. SOLUTION: A power supply unit comprises the battery pack 1 incorporating a plurality of secondary batteries 3 connected in series, and a charging circuit 9 for charging this battery pack 1. The battery pack 1 comprises a discharging current interrupting FET 4 that interrupts the discharging current, and a lowest voltage detecting portion 6, that when any battery voltage falls below a lowest voltage, changes the setting of the discharging current interrupting FET 4 from on to off. The charging circuit 9 comprises a charging current-changing portion 10 that detects the output voltage of the battery pack 1. The charging current changing portion changes the charging current so that the following is implemented: when the detected output voltage is higher than a preset voltage, main charging operation is performed; and when the detected output voltage is lower than the preset voltage, auxiliary charging operation is performed with a current smaller than that in main charging operation. In a state in which an off signal indicating the off state of the discharging current interruption FET 4 is inputted, the charging current changing portion 10 performs auxiliary charging operation, even if the output voltage of the battery pack 1 is higher than the preset voltage. COPYRIGHT: (C)2005,JPO&NCIPI
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