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AC adapter including differential comparator for tracking battery voltage during trickle charge

  • US 5,402,055 A
  • Filed: 09/30/1992
  • Issued: 03/28/1995
  • Est. Priority Date: 09/30/1992
  • Status: Expired due to Term
First Claim
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1. An AC adapter for charging a battery and for powering an electronic device, the electronic device having a maximum power requirement, the AC adapter comprising:

  • means having a sense input and an output, said means for providing electrical power up to a predetermined maximum power level and developing a voltage level at said output, wherein said voltage level of said output is regulated by a sense signal provided at said sense input and wherein said predetermined maximum power level exceeds the maximum power requirement of the electronic device;

    a battery coupled between said power providing means output and ground;

    means coupled to said power providing means for sensing said voltage level of said output and for providing said sense signal at a level so that said power providing means regulates said output at a predetermined minimum voltage level, wherein said predetermined minimum voltage level corresponds to the voltage level of said battery when fully discharged;

    a current limiter coupled in a charge path of said battery providing a signal indicative of a voltage developed across said current limiter; and

    a differential comparator coupled to said power providing means sense input and receiving said signal indicative of a voltage developed across said current limiter for modifying said sense signal to a level so that said power providing means regulates said voltage level of said output at a level to maintain said current limiter signal at a predetermined nominal voltage level.

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