Charging systems with cell balancing functions

• US 8,148,942 B2
• Filed: 11/05/2009
• Issued: 04/03/2012
• Est. Priority Date: 11/05/2009
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Densham, William, Bucur, Constantin, Lupu, Flavius, Goh, Jiun Heng, Maireanu, Stefan
• Primary Examiner(s): Fantu, Yalkew
• Application Number:
  US12/613,333
• Publication Number:
  US 20110101916A1
• Time in Patent Office: 880 Days
• Field of Search: 320/116
• US Class Current: 320/116
• CPC Class Codes: H02J 7/0018 using separate charge circuits

Abstract

In a power converter, a primary winding receives an input power. In addition, multiple secondary windings transform the input power into multiple charging currents to charge a set of cells via a set of paths. The multiple secondary windings further balance the set of cells based on the charging currents. A ratio between a first turn number of a first secondary winding of the secondary windings and a second turn number of a second secondary winding of the secondary windings is determined by a nominal voltage ratio between two corresponding cells of the set of cells.

Claims

1. A power converter for reduced power consumption balancing and charging of a plurality of cells of a rechargeable multi-cell battery pack, comprising:

a primary winding for receiving an input power; and

a plurality of secondary windings for transforming said input power into a plurality of charging currents to charge said plurality of cells via a plurality of paths, and for balancing said plurality of cells based on said charging currents, wherein a ratio between a first turn number of a first secondary winding of said secondary windings and a second turn number of a second secondary winding of said secondary windings is determined by a nominal voltage ratio between two corresponding cells of said plurality of cells.

2. The power converter as claimed in claim 1, wherein a path of said plurality of paths is disabled when an input switch that is coupled in series to said primary winding is turned on, and wherein said path is enabled when said input switch is turned off.

3. The power converter as claimed in claim 1, wherein a path of said plurality of paths comprises a diode coupled in series to a corresponding secondary winding of said secondary windings and a corresponding cell of said plurality of cells.

4. The power converter as claimed in claim 1, wherein a path of said plurality of paths comprises an output switch.

5. The power converter as claimed in claim 4, wherein a switch controller controls said output switch based on a state of an input switch that is coupled in series to said primary winding.

6. The power converter as claimed in claim 1, wherein a first charging current for charging a first cell of said plurality of cells is less than a second charging current for charging a second cell of said plurality of cells if a first voltage across said first cell is greater than a second voltage across said second cell.

7. The power converter as claimed in claim 1, wherein said ratio between said first turn number and said second turn number is approximately equal to said nominal voltage ratio between said two corresponding cells.

12. The power converter as claimed in claim 1, wherein a secondary winding of said secondary windings receives energy from said primary winding when an input switch coupled to said primary winding is turned on, and wherein said secondary winding of said secondary windings transforms said energy into a corresponding charging current of said charging currents when said input switch is turned off.

8. A method for reduced power consumption balancing and charging of a plurality of cells of a rechargeable multi-cell battery pack, comprising:

receiving an input power at a primary winding of a power converter;

transforming said input power into a plurality of charging currents by a plurality of secondary windings of said power converter, wherein a ratio between a first turn number of a first secondary winding of said secondary windings and a second turn number of a second secondary winding of said secondary windings is determined by a nominal voltage ratio between two corresponding cells of said plurality of cells;

charging said plurality of cells by said charging currents via a plurality of paths; and

balancing said plurality of cells based on said charging currents.

9. The method as claimed in claim 8, further comprising:

disabling a path of said plurality of paths when an input switch that is coupled in series to said primary winding is turned on; and

enabling said path when said input switch is turned off.

10. The method as claimed in claim 8, wherein a path of said plurality of paths comprises an output switch, and wherein said method further comprises:

controlling said output switch based on a state of an input switch that is coupled in series to said primary winding.

11. The method as claimed in claim 8, wherein a first charging current for charging a first cell of said plurality of cells is less than a second charging current for charging a second cell of said plurality of cells if a first voltage across said first cell is greater than a second voltage across said second cell.

13. The method as claimed in claim 8, wherein said transforming said input power into said plurality of charging currents comprises:

receiving energy from said primary winding when an input switch coupled to said primary winding is turned on; and

transforming said energy into said charging currents when said input switch is turned off.

14. A charging system for reduced power consumption balancing and charging of a plurality of cells of a rechargeable multi-cell battery pack, comprising:

a plurality of paths operable for transferring a plurality of charging currents to charge said plurality of cells and balance said cells; and

a plurality of secondary windings coupled to said plurality of paths and operable for transforming an input power provided by a primary winding into said plurality of charging currents, wherein a ratio between a first turn number of a first secondary winding of said secondary windings and a second turn number of a second secondary winding of said secondary windings is determined by a nominal voltage ratio between two corresponding cells of said plurality of cells.

15. The charging system as claimed in claim 14, wherein a secondary winding of said secondary windings receives energy from said primary winding when an input switch coupled to said primary winding is turned on, and wherein said secondary winding of said secondary windings transforms said energy into a corresponding charging current of said charging currents when said input switch is turned off.

16. The charging system as claimed in claim 14, wherein a path of said paths comprises a diode coupled in series to a corresponding secondary winding of said secondary windings and a corresponding cell of said plurality of cells.

17. The charging system as claimed in claim 14, wherein a first charging current for charging a first cell of said plurality of cells is less than a second charging current for charging a second cell of said plurality of cells if a first voltage across said first cell is greater than a second voltage across said second cell.

18. The charging system as claimed in claim 14, wherein said ratio between said first turn number and said second turn number is approximately equal to said nominal voltage ratio between said two corresponding cells.

19. The charging system as claimed in claim 14, further comprising:

a controller operable for adjusting said input power by comparing a sensing signal indicative of said input power with a reference signal, and operable for adjusting a sum of said charging currents by adjusting said reference signal.

20. The charging system as claimed in claim 19, wherein said controller is further operable for adjusting said reference signal according to a voltage across each cell of said cells.