Battery cell balancing systems using current regulators

• US 7,973,514 B2
• Filed: 12/27/2007
• Issued: 07/05/2011
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Gong, Xiaofei, Xiao, Anquan
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): RAMADAN, RAMY O
• Application Number:
  US12/005,507
• Publication Number:
  US 20090091294A1
• Time in Patent Office: 1,286 Days
• Field of Search: 320/116, 320118-120, 320/122, 361/54, 307 52- 54, 307/77
• US Class Current: 320/122
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

According to one embodiment of the invention, there is provided a cell balancing circuit used for balancing a cell. The cell balancing circuit includes a bypass path coupled to the cell, a current regulator coupled to the bypass path, and a bleeding control switch. The current regulator is operable for producing a current and for controlling a conductance status of the bypass path. The bleeding control switch conducts the bypass path in response to the current produced by the current regulator.

Claims

1. A cell balancing circuit comprising:

a bypass path coupled to a cell for enabling a bypass current of said cell;

a current regulator coupled to said bypass path for producing a current having a predetermined current level to control a conductance status of said bypass path;

a bleeding control switch in said bypass path for conducting said bypass path in response to said current, said bleeding control switch has a first terminal and a second terminal; and

a resistor coupled between said bypass path and said current regulator,

wherein said current flows through said resistor to produce a voltage drop on said resistor, wherein a voltage difference between said first terminal and said second terminal of said bleeding control switch is equal to said voltage drop on said resistor, and wherein a conductance status of said bleeding control switch is determined by said voltage difference.

2. The cell balancing circuit of claim 1, wherein said current regulator comprises a current source operable for producing said current flowing from a power supply to a negative terminal of said cell.

3. The cell balancing circuit of claim 1, wherein said current regulator comprises a current sink operable for producing said current flowing from a positive terminal of said cell to ground.

4. The cell balancing circuit of claim 1, further comprising:

a current regulator control unit coupled to said current regulator for controlling said current regulator and for enabling said current regulator if said cell is unbalanced.

5. The cell balancing circuit of claim 4, wherein said cell is unbalanced if a voltage difference between a first cell voltage of said cell and a second cell voltage of another cell in series with said first cell is greater than a predetermined threshold.

6. The cell balancing circuit of claim 4, wherein said cell is unbalanced if a first cell voltage of said cell is greater than a predetermined threshold.

7. A battery pack having at least a first cell and a second cell adjacent to said first cell, comprising:

a first bypass path coupled to said first cell for enabling a bypass current of said first cell;

a second bypass path coupled to said second cell for enabling a bypass current of said second cell;

a controller coupled to said first cell and said second cell for balancing said first cell and said second cell, said controller comprising a first current regulator coupled to said first bypass path for producing a first current to control a conductance status of said first bypass path and comprising a second current regulator coupled to said second bypass path for producing a second current to control a conductance status of said second bypass path;

a first bleeding control switch in said first bypass path for conducting said first bypass path in response to said first current, said first bleeding control switch has a first terminal and a second terminal;

a second bleeding control switch in said first bypass path for conducting said second bypass path in response to said second current; and

a resistor coupled between said first bypass path and said first current regulator,

wherein said first current flows through said resistor to produce a voltage drop on said resistor, wherein a voltage difference between said first terminal and said second terminal of said first bleeding control switch is equal to said voltage drop on said resistor,

wherein said conductance status of said first bleeding control switch is determined by said voltage difference,

wherein said controller is operable for enabling said first current regulator and said second current regulator simultaneously.

8. The battery pack of claim 7, wherein said first current regulator comprises a current sink operable for producing said first current flowing from a positive terminal of said first cell to ground.

9. The battery pack of claim 7, wherein said first current regulator comprises a current source operable for producing said first current flowing from a power supply to a negative terminal of said first cell.

10. The battery pack of claim 7, wherein said controller enables said first current regulator if said first cell is unbalanced.

11. The battery pack of claim 10, wherein said first cell is unbalanced if a voltage difference between a first cell voltage of said first cell and a second cell voltage of another cell is greater than a predetermined threshold.

12. The battery pack of claim 10, wherein said first cell is unbalanced if a first cell voltage of said first cell is greater than a predetermined threshold.

13. A method for balancing a plurality of cells, said method comprising:

generating a first current having a predetermined current level by a first current regulator;

enabling said first current to flow through a resistor coupled between said first current regulator and a first bypass path corresponding to a first cell of said cells to produce a voltage drop on said resistor;

turning on a bleeding control switch in said first bypass path in response to said voltage drop to conduct said first bypass path, wherein a conductance status of said bleeding control switch is determined by a voltage difference between a first terminal of said bleeding control switch and a second terminal of said bleeding control switch, and wherein said voltage difference is equal to said voltage drop on said resistor; and

enabling a bypass current of said first cell to flow through said first bypass path.

22. The method of claim 13, further comprising:

generating a second current having said predetermined current level by a second current regulator;

conducting a second bypass path coupled to a second cell of said cells in response to said second current; and

enabling said first current regulator and said second current regulator simultaneously,

wherein said second cell is adjacent to said first cell.

14. An electronic system comprising:

a functional module for performing a function; and

a battery pack for powering said functional module, wherein said battery pack comprises;

a plurality of cells comprising a first cell and a second cell adjacent to said first cell;

a first bypass path coupled to said first cell for enabling a bypass current of said first cell;

a second bypass path coupled to said second cell for enabling a bypass current of said second cell;

a controller coupled to said first cell and said second cell for balancing said first cell and said second cell, said controller comprising a first current regulator coupled to said first bypass path for producing a first current to control a conductance status of said first bypass path and comprising a second current regulator coupled to said second bypass path for producing a second current to control a conductance status of said second bypass path;

a first bleeding control switch in said first bypass path for conducting said first bypass path in response to said first current, said first bleeding control switch has a first terminal and a second terminal;

a second bleeding control switch in said first bypass path for conducting said second bypass path in response to said second current; and

a resistor coupled between said first bypass path and said first current regulator,

wherein said first current flows through said resistor to produce a voltage drop on said resistor, wherein a voltage difference between said first terminal and said second terminal of said first bleeding control switch is equal to said voltage drop on said resistor, and wherein said conductance status of said first bleeding control switch is determined by said voltage difference,

wherein said controller is operable for enabling said first current regulator and said second current regulator simultaneously.

15. The electronic system of claim 14, wherein said first current regulator comprises a current sink operable for producing said first current, and wherein said first current flows from a positive terminal of said first cell to ground.

16. The electronic system of claim 14, wherein said first current regulator comprises a current source operable for producing said first current, and wherein said first current flows from a power supply to a negative terminal of said first cell.

17. The electronic system of claim 14, wherein said controller enables said first current regulator if said first cell is unbalanced.

18. The electronic system of claim 17, wherein said first cell is unbalanced if a voltage difference between a first cell voltage of said first cell and a second cell voltage of another cell is greater than a predetermined threshold.

19. The electronic system of claim 17, wherein said first cell is unbalanced if a first cell voltage of said first cell is greater than a predetermined threshold.

20. The electronic system of claim 14, wherein said functional module comprises a central processing unit (CPU).

21. The electronic system of claim 14, wherein said functional module comprises a vehicle motor.