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Computer battery pack charge current sensor with gain control

  • US 5,659,238 A
  • Filed: 02/22/1996
  • Issued: 08/19/1997
  • Est. Priority Date: 02/22/1996
  • Status: Expired due to Term
First Claim
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1. A current sensor for monitoring discharge currents from a battery while the battery is connected to a system capable of discharging the battery in at least first and second discharge states, the system providing an indication of the first discharge state and an indication of the second discharge state, the current sensor comprising:

  • a first sense resistor for coupling in series with the battery during the first discharge state and having a first terminal for providing a first current signal indicating the current in the battery during the first discharge state;

    a second sense resistor for coupling in series with the battery during the second discharge state and having a first terminal for providing a second current signal indicating the current in the battery during the second discharge state;

    a third resistor having a first terminal for receiving the second current signal and a second terminal for providing a sense signal indicative of the current in the battery during the second discharge state;

    a first switch having a series switched path activated by a control terminal for coupling said first resistor and the battery in series when the system indicates the first discharge state and for decoupling said first resistor and the battery when the system indicates the second discharge state; and

    a second switch having a series switched path activated by a control terminal, the series switched path of said second switch having a first terminal coupled to the first terminal of said first sense resistor for receiving the first current signal and having a second terminal coupled to the second terminal of said third resistor for providing the sense signal when the system indicates the first discharge state.

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