CURRENT MEASUREMENT TECHNIQUES TO COMPENSATE FOR SHUNT DRIFT
First Claim
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1. A method of determining a resistance of a shunt resistor coupled to a battery terminal, the method comprising:
- receiving an input signal corresponding to a voltage across the shunt resistor;
during a first conversion cycle in the absence of a stimulus applied to the shunt resistor and during a second conversion cycle in the presence of the stimulus applied to the shunt resistor;
generating a first digital signal using a combination of a chopped input signal and an offset error;
determining a first output signal using a de-chopped first digital signal; and
determining a second output signal using the first digital signal; and
determining the resistance of the shunt resistor using the first and second output signals from the first and second conversion cycles.
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Abstract
Described are various current measurement techniques that can compensate for drift in shunt resistance. Determining a resistance of a shunt resistor, e.g., coupled to a battery terminal, can include introducing a known signal in sync with the chop phases of a dual system chop scheme, chopping the known signal out in the main signal path, and explicitly extracting the known signal in a parallel, additional signal deprocessing path.
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Citations
20 Claims
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1. A method of determining a resistance of a shunt resistor coupled to a battery terminal, the method comprising:
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receiving an input signal corresponding to a voltage across the shunt resistor; during a first conversion cycle in the absence of a stimulus applied to the shunt resistor and during a second conversion cycle in the presence of the stimulus applied to the shunt resistor; generating a first digital signal using a combination of a chopped input signal and an offset error; determining a first output signal using a de-chopped first digital signal; and determining a second output signal using the first digital signal; and determining the resistance of the shunt resistor using the first and second output signals from the first and second conversion cycles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for determining a resistance of a shunt resistor coupled to a battery terminal, the apparatus comprising:
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a measurement channel circuit configured to receive a chopped input signal corresponding to a voltage across the shunt resistor and to generate a first digital signal using a combination of the chopped input signal and an offset error during a first conversion cycle in the absence of a stimulus applied to the shunt resistor and during a second conversion cycle in the presence of the stimulus applied to the shunt resistor; a first output channel circuit coupled to the output of the measurement channel circuit and configured to determine a first output signal using a de-chopped first digital signal for the first and second conversion cycles; a second output channel circuit coupled to the output of the measurement channel circuit and configured to determine a second output signal using the first digital signal for the first and second conversion cycles; and a processor configured to determine the resistance of the shunt resistor using the first and second output signals from the first and second conversion cycles. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for determining a resistance of a shunt resistor coupled to a battery terminal, the apparatus comprising:
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means for receiving an input signal corresponding to a voltage across the shunt resistor; means for generating a first digital signal using a combination of a chopped input signal and an offset error during a first conversion cycle in the absence of a stimulus applied to the shunt resistor and during a second conversion cycle in the presence of the stimulus applied to the shunt resistor; means for determining a first output signal using a de-chopped first digital signal for the first and second conversion cycles; and means for determining a second output signal using the first digital signal for the first and second conversion cycles; and means for determining the resistance of the shunt resistor using the first and second output signals. - View Dependent Claims (19, 20)
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Specification