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Battery charger

  • US 5,850,136 A
  • Filed: 05/14/1997
  • Issued: 12/15/1998
  • Est. Priority Date: 12/26/1996
  • Status: Expired due to Term
First Claim
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1. A battery charger comprising:

  • a direct current power source adapted to be connected in series with a battery array which is comprised of serially-connected battery cells, said direct current power source being operable to output a predetermined maximum electric current when it performs a constant-current operation; and

    charge control circuits adapted to be connected in parallel with the serially-connected battery cells, respectively, each of said charge control circuits including;

    a switching device which is connected in parallel with an associated one of the battery cells when said charge control circuit is connected to the associated one battery cell;

    a comparator, having a hysteresis characteristic thereof determined by a first threshold voltage and a second threshold voltage lower than the first threshold voltage, for comparing a battery voltage across the associated one battery cell with one of the first and second threshold voltages which is selected depending on a direction in which the battery voltage changes and for generating a comparator output indicative of a result of the comparison between the battery voltage and the selected one threshold voltage, the first and second threshold voltages being determined according to charging characteristics of the serially-connected battery cells;

    a reference voltage source for generating a reference voltage corresponding to one of the first and second threshold voltages; and

    a driving circuit for selectively rendering the switching device conductive according to the comparator output, said driving circuit being operable to permit a constant current to flow from the associated one battery cell to said switching device when said switching device is conductive.

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