System and methods for current balancing

Patent metadata

Field	Value
Publication number	US-9368981-B2
Application number	US-201414328355-A
Country	US
Kind code	B2
Filing date	Jul 10, 2014
Priority date	Jul 12, 2013
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

A battery module includes: a battery pack including multiple cells; control circuits corresponding to the cells, each control circuit including a control unit for managing the corresponding cell and a compensation unit for generating a corresponding compensation current such that the sum of the corresponding consumed current and the corresponding compensation current is equal to a target total current, where the control circuits include a first control circuit and a second control circuit, where the first control circuit includes a first control unit operating with a first consumed current, the second control circuit includes a second control unit operating with a second consumed current, and where the first control circuit conditionally generates a first compensation current and the second control circuit conditionally generates a second compensation current based on a comparison of the first consumed current and the second consumed current.

First claim

We claim:

1. A battery module, comprising:
a battery pack comprising a plurality of cells; and
a plurality of control circuits corresponding to the plurality of cells, each control circuit comprising:
a control unit, operable for managing the corresponding cell, the control unit operating with a corresponding consumed current; and
a compensation unit, coupled to the control unit, that is operable for generating a corresponding compensation current such that the sum of the corresponding consumed current and the corresponding compensation current is equal to a target total current,

wherein the plurality of control circuits comprise a first control circuit and a second control circuit, the first control circuit comprising a first control unit operating with a first consumed current, the second control circuit comprising a second control unit operating with a second consumed current, and wherein the first control circuit conditionally generates a first compensation current and the second control circuit conditionally generates a second compensation current based on a comparison of the first consumed current and the second consumed current.

2. The battery module of claim 1 , wherein if the first consumed current is greater than the second consumed current, then the second control circuit generates the second compensation current such that the sum of the second consumed current and the second compensation current is equal to the target total current.

3. The battery module of claim 1 , wherein if the second consumed current is greater than the first consumed current, then the first control circuit generates the first compensation current such that the sum of the first consumed current and the first compensation current is equal to the target total current.

4. The battery module of claim 1 , wherein each compensation unit comprises:
a first compensation branch, operable for generating a first branch current, the first compensation branch comprising a first operational amplifier and a first switch controlled by an output of the first operational amplifier; and
a second compensation branch, operable for generating a second branch current, the second compensation branch comprising a second operational amplifier and a second switch controlled by an output of the second operational amplifier,
wherein the sum of the first branch current and the second branch current is equal to the corresponding compensation current.

5. The battery module of claim 4 , wherein the first switch is a PMOSFET, wherein the first switch is on if the output of the first operational amplifier is in a first state, wherein the first switch is off if the output of the first operational amplifier is in a second state, and wherein the first switch has a built-in voltage offset that sets the output of the first operational amplifier to the second state if the first operational amplifier operates in a nonlinear region and if the first operational amplifier's inverting input is equal to its non-inverting input.

6. The battery module of claim 4 , wherein the first switch is a PMOSFET, wherein the first switch is on if the output of the first operational amplifier is in a first state, wherein the first switch is off if the output of the first operational amplifier is in a second state, and wherein the output of the first operational amplifier changes to the first state if a voltage difference between the first operational amplifier's inverting input and non-inverting input is greater than a voltage threshold.

7. The battery module of claim 4 , wherein the second switch is an NMOSFET, wherein the second switch is on if the output of the second operational amplifier is in a first state, wherein the second switch is off if the output of the second operational amplifier is in a second state, and wherein the second switch has a built-in voltage offset that sets the output of the second operational amplifier to the second state if the second operational amplifier operates in a nonlinear region and if the second operational amplifier's inverting input is equal to its non-inverting input.

8. The battery module of claim 4 , wherein the second switch is an NMOSFET, wherein the second switch is on if the output of the second operational amplifier is in a first state, wherein the second switch is off if the output of the second operational amplifier is in a second state, and wherein the output of the second operational amplifier changes to the first state if a voltage difference between the second operational amplifier's non-inverting input and inverting input is greater than a voltage threshold.

9. The battery module of claim 1 , further comprising:
a plurality of detection units, wherein one of the detection units is coupled between the first control circuit and the second control circuit, operable for generating a detection signal indicative of a difference between the first consumed current and the second consumed current,
wherein the first control circuit and the second control circuit are coupled to the corresponding cells through the detection unit, and wherein the first control circuit and the second control circuit generate the first compensation current and the second compensation current, respectively, based on the detection signal.

10. The battery module of claim 9 , wherein each detection unit comprises two diodes connected back-to back in parallel.

11. The battery module of claim 10 , wherein each detection unit detects voltages at the two diodes to generate the detection signal.

12. The battery module of claim 1 , wherein if the battery module enters a balanced working state, then there is no current flowing through a plurality of paths between the plurality of cells and the plurality of control circuits.

13. A method comprising:
operating a first control unit of a battery module with a first consumed current, the battery module further comprising a plurality of cells and a plurality of control circuits;
operating a second control unit of the battery module with a second consumed current;
detecting a difference between the first consumed current and the second consumed current based on a detection signal;
generating a compensation current based on the detection signal; and
repeating the detecting and generating operations until the battery module enters a balanced working state, wherein in the balanced working state there is no current flowing through a plurality of paths between the plurality of cells and the plurality of control circuits.

14. The method of claim 13 , wherein if the detection signal indicates that the second consumed current is greater than the first consumed current, then a first control circuit generates a first compensation current such that the sum of the first consumed current and the first compensation current is equal to a target total current.

15. The method of claim 13 , wherein if the detection signal indicates that the first consumed current is greater than the second consumed current, then a second control circuit generates a second compensation current such that the sum of the second consumed current and the second compensation current is equal to a target total current.

16. The method of claim 13 , wherein the detection signal is generated by a detection unit coupled between the first control circuit and the second control circuit, and wherein the detection unit comprises two diodes connected back-to back in parallel.

17. The method of claim 16 , wherein the detection signal is generated by detecting voltages at the two diodes.

18. A system comprising:
a first cont

Assignees

• O2Micro Inc

Inventors

• Li Guoxing
• Li Yan
• Xue Weidong
• Xiao Anquan

Classifications

• H02J7/54 Primary

  Passive balancing, e.g. using resistors or parallel MOSFETs · CPC title

• H02J7/0016 Primary

  Electricity · mapped topic