Methods and apparatus for a battery
Various embodiments of the present technology may provide methods and apparatus for a battery. The apparatus may determine a first current according to a first technique and a second current according to a second technique. The apparatus may use a Kalman filter to compute the state of charge of the battery, wherein the Kalman filter uses one of the first current and the second current based on a comparison of the second current to a threshold current.
1. An apparatus for charging a battery, comprising:
a voltage detector configured to measure a voltage of the battery;
a current sensor configured to detect a first current of the battery;
a switch configured to selectively control a charge current for charging the battery;
a charging controller configured to supply a control signal to the switch for controlling the charge current; and
a processor configured to:
compute a difference voltage from the measured voltage and an open circuit voltage;
determine a second current of the battery based on the difference voltage;
generate a first output comprising comparing the second current to a predetermined threshold current;
select one of the first current and the second current based on the first output;
compute a state of charge of the battery using a prediction and correction algorithm and the selected current; and
communicate the state of charge of the battery to the charging controller.
2. The apparatus according to claim 1 , further comprising a memory configured to store battery data indicating a relationship between voltage values and current values.
3. The apparatus according to claim 1 , wherein:
the processor selects the first current if the second current is greater than or equal to the threshold current; and
the processor selects the second current if the second current is less than the threshold current.
4. The apparatus according to claim 1 , wherein the processor is further configured to compare the difference voltage to a threshold voltage.
5. The apparatus according to claim 4 , wherein:
the processor selects the second current if the second current is greater than or equal to the threshold current or if the difference voltage is less than or equal to the threshold voltage; and
the processor selects the first current if the second current is less than the threshold current and the difference voltage is greater than the threshold voltage.
6. The apparatus according to claim 1 , wherein the processor comprises a multiplexer to select one of the first current and the second current based on the first output.
7. The apparatus according to claim 1 , wherein the processor comprises a Kalman Filter to compute the state of charge of the battery using the selected current.
8. The apparatus according to claim 1 , wherein the processor comprises a comparator to compare the second current to the predetermined threshold current.
9. The apparatus according to claim 1 , wherein determining the second current comprises: accessing a memory and selecting the second current that corresponds to the difference voltage.
10. A method for charging a battery, comprising:
detecting a first current of the battery;
measuring a voltage of the battery;
computing a difference voltage based on the measured voltage and an open circuit voltage;
determining a second current of the battery based on the difference voltage;
comparing the second current to a predetermined threshold current;
comparing the measured voltage to a predetermined voltage; and
calculating a state of charge of the battery comprising executing an algorithm using the first current if:
the second current is less than the predetermined threshold current; and
the difference voltage is greater than the predetermined voltage; and
otherwise using the second current;
communicating the state of charge of the battery to a charging controller;
generating, by the charging controller, a control signal for controlling a charge current for charging the battery; and
selectively controlling the charge current for charging the battery in response to the control signal from the charging controller.
11. The method according to claim 10 , wherein the algorithm performs prediction and correction.
12. The method according to claim 10 , wherein determining the second current comprises extracting the second current from a look-up table based on the difference voltage.
13. The method according to claim 10 , wherein detecting the first current comprises measuring a voltage across a sense resistor.
14. A system for battery charging, comprising:
a battery;
a switch configured to selectively control a charge current for charging the battery;
a charging controller configured to supply a control signal to the switch for controlling the charge current; and
a fuel gauge connected to the battery and comprising:
a voltage detector configured to measure a voltage of the battery;
a current sensor configured to detect a first current of the battery;
a memory for storing a look-up table comprising relational battery data; and
a processor connected to the voltage detector, the current sensor, and the memory, wherein the processor comprises:
an arithmetic circuit configured to compute a difference voltage of the measured voltage and an open circuit voltage;
a selector circuit configured to extract a second current from the memory according to the difference voltage;
a first comparator configured to compare the second current to a predetermined threshold current and generate a first comparator output based on the comparison;
a multiplexer configured to output one of the first current and the second current based on the first comparator output; and
a state of charge calculator connected to an output terminal of the multiplexer and configured to compute a state of charge of the battery using the output current; and
wherein the processor is configured to communicate the state of charge of the battery to the charging controller.
15. The system according to claim 14 , wherein the relational battery data comprises voltage values and corresponding current values.
16. The system according to claim 14 , wherein:
the multiplexer outputs the first current if the second current is greater than or equal to the predetermined threshold; and
the multiplexer outputs the second current if the second current is less than the predetermined threshold.
17. The system according to claim 14 , further comprising a second comparator configured to compare the difference voltage to a predetermined voltage and generate a second comparator output based on the comparison.
18. The system according to claim 17 , wherein the multiplexer outputs one of the first current and the second current based on the second comparator output.
19. The system according to claim 17 , wherein:
the multiplexer outputs the second current if the second current is greater than or equal to the predetermined threshold or if the difference voltage is less than or equal to the predetermined voltage; and
the multiplexer outputs the first current if the second current is less than the predetermined threshold and the difference voltage is greater than the predetermined voltage.
20. The system according to claim 14 , wherein the current sensor is configured to detect the first current by measuring a voltage across a sense resistor connected to the battery.