Circuit for detecting low battery condition on an electronic device with a changing load
First Claim
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1. A circuit for detecting a low battery condition on a portable computer device comprising:
- a. inputs from a battery pack having an internal resistance, where the inputs comprise a battery output voltage and a battery output current;
b. a current sense circuit to provide a voltage proportional to the battery output current;
c. an A/D converter which inputs the battery output voltage and the voltage proportional to the battery current and outputs in digital form the measured battery output voltage and measured battery current; and
d. a micro-processor which inputs the measured battery current and measured battery output voltage;
e. wherein the micro-processor adjusts the measured battery output voltage based on the measured battery current and the battery internal resistance and then uses the adjusted battery voltage to determine an estimate of remaining battery life according to a battery voltage discharge curve associated with the battery pack.
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Abstract
A method to more accurately monitor remaining battery life under varying load conditions. The measured battery voltage is adjusted for the current load and then used to determine the remaining battery life according to the battery voltage discharge curve for the battery type and chemistry. Advantageously, in an embodiment the present invention the remaining battery life can be determined despite fluctuations in the current due to a changing load and without monitoring current flow so that the determination of battery life is independent of the battery charging process.
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Citations
13 Claims
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1. A circuit for detecting a low battery condition on a portable computer device comprising:
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a. inputs from a battery pack having an internal resistance, where the inputs comprise a battery output voltage and a battery output current;
b. a current sense circuit to provide a voltage proportional to the battery output current;
c. an A/D converter which inputs the battery output voltage and the voltage proportional to the battery current and outputs in digital form the measured battery output voltage and measured battery current; and
d. a micro-processor which inputs the measured battery current and measured battery output voltage;
e. wherein the micro-processor adjusts the measured battery output voltage based on the measured battery current and the battery internal resistance and then uses the adjusted battery voltage to determine an estimate of remaining battery life according to a battery voltage discharge curve associated with the battery pack. - View Dependent Claims (2, 3, 4)
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5. A portable computer device having a circuit for detecting a low battery condition comprising:
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a. inputs from a battery pack having an internal resistance, where the inputs comprise a battery output voltage and a battery output current;
b. a current sense circuit to provide a voltage proportional to the battery output current;
c. an A/D converter which inputs the battery output voltage and the voltage proportional to the battery current and outputs in digital form the measured battery output voltage and measured battery current; and
d. a micro-processor which inputs the measured battery current and measured battery output voltage;
e. wherein the microprocessor adjusts the measured battery output voltage based on the measured battery current and the battery internal resistance and then uses the adjusted battery voltage to determine an estimate of remaining battery life according to a battery voltage discharge curve associated with the battery pack. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A method for detecting a low battery condition on a portable computer device comprising:
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a. inputting from a battery pack having an internal resistance, a battery output voltage and a battery output current;
b. adjusting the output voltage based on the battery output current and the battery internal resistance;
c. estimating the remaining battery life according to a battery voltage discharge curve associated with the battery pack using the adjusted battery voltage. - View Dependent Claims (12, 13)
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Specification