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Method for detecting battery removal or absent battery condition in a constant current charger

  • US 6,340,876 B1
  • Filed: 09/18/2000
  • Issued: 01/22/2002
  • Est. Priority Date: 09/18/2000
  • Status: Active Grant
First Claim
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1. A battery detecting system for a battery charger comprising:

  • a first combinatorial element having a first input for receiving current flowing through a battery charger, a second input and an output;

    a second combinatorial element having a first input connected to the first combinatorial element output, a second input and an output;

    a first inverter having an input for detecting a battery charger output voltage and further having an output;

    a second inverter having an input connected to the first inverter output and further having an output;

    a third combinatorial element having a first input connect to the second inverter output, a second input connected to the first inverter input, and an output connected to the first combinatorial element second input;

    a third inverter having an input for detecting a battery charger output voltage and further having an output;

    a fourth combinatorial element having a first input connected to the third inverter output, a second input connected to the third inverter input, and an output;

    a fifth combinatorial element having a first input connected to the second combinatorial element output, a second input for receiving a global reset signal, a third input connected to the fourth combinatorial element output, and an output;

    a sixth combinatorial element having a first input connected to the second combinatorial element second input, a second input for receiving a global clock signal, and an output;

    a first flip-flop element having a non-inverting input connected to the sixth combinatorial element output, an inverting input connected to the sixth combinatorial element output, and an output; and

    a second flip-flop element having a non-inverting input connected to the first flip-flop element output, a clock input connected to the sixth combinatorial element output, an inverting input connected to the sixth combinatorial element output, and an output connected to the sixth combinatorial element first input, wherein the battery detecting system is operational to generate an output signal at the second flip-flop element output when a first signal rising edge is received at the first inverter input, and within one minute of receiving the first signal rising edge, a second signal rising edge is latched at the fifth combinatorial element first input subsequent to a falling edge of the first signal in which the first signal is low for a duration of at least 20-seconds.

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