Negative Peak Voltage Detection for Enhanced FuelGauge Empty Voltage Prediction

• US 20120153960A1
• Filed: 12/09/2011
• Published: 06/21/2012
• Est. Priority Date: 12/15/2010
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Wortham, Jason Allen, Vanden Wymelenberg, Joseph Brian, Lau, Kin Keung
• Granted Patent: US 9,052,368 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3828 using current integration

Abstract

Negative peak voltage detection for battery end of life estimations in fuel gauging is disclosed. Battery powered devices such cell phones and laptop computers create some noise in the form of negative excursions from the average output voltage of the battery which can cause the battery powered device to stop functioning. By negative peak detection relative to the average battery voltage, the end of life or discharged voltage condition can be altered in response to the negative peaks to obtain the maximum battery life without risk of the device inadvertently shutting down. Average output voltage of the battery may be taken as an estimated open circuit voltage or some other battery voltage. Various embodiments are disclosed.

Claims

1. A method of estimating the end of life of a battery in a battery powered device having a predetermined available state of charge comprising:

estimating an average battery voltage;

determining the negative peaks in the battery voltage relative to the average battery voltage during operation of the battery powered device and storing a largest negative peak in the battery voltage relative to the average battery voltage;

modifying the predetermined available state of charge based on the largest negative peak in the battery voltage relative to the average battery voltage.

2. The method of claim 1 wherein the average battery voltage is an estimated open circuit voltage of the battery.

3. The method of claim 2 wherein the estimated open circuit battery voltage is estimated by a battery voltage model.

4. The method of claim 3 wherein the battery voltage model is an RC battery voltage model.

5. The method of claim 3 wherein the battery voltage model includes a coulomb counter.

6. The method of claim 1 further comprising:

providing the modified predetermined available state of charge to a battery voltage model; and

determining the state of charge of the battery using the battery voltage model and the modified predetermined available state of charge of the battery.

7. The method of claim 1 wherein the sensing of the negative peaks in the battery voltage relative to the average battery voltage during operation of the battery powered device and storing a largest negative peak in the battery voltage relative to the estimated state of charge of the battery is done repeatedly, each over a time period during which the change in the average battery voltage due to discharge of the battery is less than the negative peaks being stored.

8. The method of claim 1 wherein the sensing the negative peaks in the battery voltage during operation of the battery powered device is done using an oscillator, a counter coupled to an output of the oscillator and a variable resistance controlled by the counter, the variable resistance controlling a circuit providing an output responsive to the negative peaks as stored as a count in the counter, the sensing being done by repeatedly resetting the counter, and enabling the oscillator whenever, between resets, a negative peak exceeds an already stored negative peak, to cause the counter to count until the counter output corresponds to the new negative peak in battery voltage.

9. The method of claim 1 wherein the battery voltage model receives as inputs, a voltage responsive to battery voltage and an input from a coulomb counter.

10. The method of claim 1 wherein modifying the predetermined available state of charge based on the largest negative peak in the battery voltage relative to the average battery voltage comprises subtracting the largest negative peak in the battery voltage relative to the average battery voltage from the average battery voltage.

11. The method of claim 1 wherein modifying the predetermined available state of charge based on the largest negative peak in the battery voltage relative to the average battery voltage comprises subtracting a fraction of the largest negative peak in the battery voltage relative to the average battery voltage wherein the fraction is less than or greater than one.

12. The method of claim 1 wherein the battery powered device has a plurality of operating modes, and wherein the method is practiced separately for each operating mode.

13. A method of estimating the end of life of a battery in a battery powered device having a predetermined available state of charge comprising:

estimating an average battery voltage;

determining the ripple in the battery voltage relative to the average battery voltage during operation of the battery powered device and storing a largest ripple in the battery voltage relative to the average battery voltage;

modifying the predetermined available state of charge based on the ripple in the battery voltage relative to the average battery voltage.

14. The method of claim 13 wherein the average battery voltage is an estimated open circuit voltage of the battery.

15. The method of claim 14 wherein the estimated open circuit battery voltage is estimated by a battery voltage model.

16. The method of claim 15 wherein the battery voltage model is an RC battery voltage model.

17. The method of claim 15 wherein the battery voltage model includes a coulomb counter.

18. The method of claim 13 further comprising:

providing the modified predetermined available state of charge to a battery voltage model; and

determining the state of charge of the battery using the battery voltage model and the modified predetermined available state of charge of the battery.

19. The method of claim 13 wherein the battery voltage model receives as inputs, a voltage responsive to battery voltage and an input from a coulomb counter.

20. The method of claim 13 wherein modifying the predetermined available state of charge based on the largest ripple in the battery voltage relative to the average battery voltage comprises subtracting the largest ripple in the battery voltage relative to the average battery voltage from the average battery voltage.

21. The method of claim 13 wherein modifying the predetermined available state of charge based on the largest ripple in the battery voltage relative to the average battery voltage comprises subtracting a fraction of the largest ripple in the battery voltage relative to the average battery voltage wherein the fraction is less than or greater than one.

22. The method of claim 13 wherein the battery powered device has a plurality of operating modes, and wherein the method is practiced separately for each operating mode.