| 摘要 |
PROBLEM TO BE SOLVED: To suppress noise produced in conjunction with expansion and shrinkage of a battery pack in an electric storage device for converting externally supplied power into direct-current power of a predetermined voltage and charging a secondary battery therewith. SOLUTION: The phase difference between the switching cycle supplied to battery modules 21 in a first group and the switching cycle supplied to battery modules 22 in a second group is set to 180°. When viewed at some point of time, displacement due to shrinkage is produced in either the battery modules 21 in the first group or the battery modules 22 in the second group. When viewed as an entire battery pack 120, however, the amount of this displacement is substantially constant in terms of time. That is, the amount of the displacement due to expansion and shrinkage of the entire battery pack 120 can be reduced. For this reason, noise and the like produced by the entire battery pack 120 expanding or shrinking can be reduced. COPYRIGHT: (C)2007,JPO&INPIT |
