MULTI-CELL BATTERY PACK PROTECTION CIRCUIT

• US 20100194345A1
• Filed: 02/05/2009
• Published: 08/05/2010
• Est. Priority Date: 02/05/2009
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: LI, Guo Xing
• Granted Patent: US 8,253,383 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

A voltage detection circuit can include a status sensing network and a comparing network. The status sensing network can simultaneously detect a cell voltage for each battery cell of a plurality of battery cells. The comparing network can simultaneously compare the detected cell voltages with a predetermined voltage threshold by comparing the maximum of the cell voltages with a first (high-voltage) threshold, and by comparing the minimum of the cell voltages with a second (low-voltage) threshold. The comparing network can also generate an indication signal when a cell voltage does not satisfy the respective voltage threshold.

Claims

1. A voltage detection circuit, comprising:

a status sensing network for detecting a plurality of cell voltages, each of said cell voltages corresponding to an individual battery cell of a plurality of battery cells including a first to an N^th battery cell; and

a comparing network coupled to said status sensing network for simultaneously comparing said cell voltages with at least one predetermined voltage threshold by comparing an extremum of said plurality of cell voltages with said predetermined voltage threshold, and for generating an indication signal when said extremum crosses said predetermined voltage threshold.

2. The voltage detection circuit as claimed in claim 1, wherein said status sensing network comprises a voltage to current (V/I) conversion network for converting said cell voltages to a plurality of cell currents.

3. The voltage detection circuit as claimed in claim 2, wherein said comparing network is capable of being used for simultaneously comparing said cell currents with a predetermined current threshold corresponding to said predetermined voltage threshold and for generating said indication signal when said extremum of said plurality of cell currents crosses said predetermined current threshold.

4. The voltage detection circuit as claimed in claim 2, further comprising a plurality of resistors coupled to said V/I conversion network for reconverting said cell currents to said cell voltages.

5. The voltage detection circuit as claimed in claim 1, wherein said comparing network comprises a voltage winner-take-all (V-WTA) network for simultaneously comparing said cell voltages with a predetermined high-voltage threshold and for generating said indication signal when the maximum cell voltage of said plurality of cell voltages is greater than said predetermined over-voltage threshold.

6. The voltage detection circuit as claimed in claim 5, wherein said V-WTA network comprises:

a threshold transistor for receiving said predetermined high-voltage threshold;

a first-gain stage coupled to said threshold transistor including a first to an N^th first-gain transistor for receiving said cell voltages of said first to said N^th battery cell respectively and for actuating a K^th first-gain transistor to amplify a voltage difference between said predetermined high-voltage threshold and a K^th cell voltage which is said maximum of said plurality of cell voltages and received by said K^th first-gain transistor when said K^th cell voltage is greater than said predetermined high-voltage threshold; and

a second gain stage coupled to said first gain stage including a first to an N^th second-gain transistor for actuating a K^th second-gain transistor corresponding to said K^th first-gain transistor to further amplify said voltage difference and for generating said indication signal when said K^th cell voltage is greater than said predetermined high-voltage threshold, where K=1, 2, . . . N.

7. The voltage detection circuit as claimed in claim 1, wherein said comparing network comprises a voltage loser-take-all (V-LTA) network for simultaneously comparing said cell voltages with a predetermined low-voltage threshold and for generating said indication signal when the minimum cell voltage of said plurality of cell voltages is lower than said predetermined low-voltage threshold.

8. The voltage detection circuit as claimed in claim 7, wherein said V-LTA network comprises:

a threshold transistor for receiving said predetermined low-voltage threshold;

a first-gain stage coupled to said threshold transistor including a first to an N^th first-gain transistor for receiving said cell voltages of said first to said N^th battery cell respectively and for actuating a K^th first-gain transistor to amplify a voltage difference between said predetermined low-voltage threshold and a K^th cell voltage which is said minimum of said plurality of cell voltages and received by said K^th first-gain transistor when said K^th cell voltage is lower than said predetermined low-voltage threshold; and

a second gain stage coupled to said first gain stage including a first to an N^th second-gain transistor for actuating a K^th second-gain transistor corresponding to said K^th first-gain transistor to further amplify said voltage difference and for generating said indication signal when said K^th cell voltage is lower than said predetermined low-voltage threshold, where K=1, 2, . . . N.

9. The voltage detection circuit as claimed in claim 1, further comprising a second predetermined threshold for generating a second indication signal when the maximum cell voltage of said plurality of cell voltages is greater than said second predetermined threshold.

10. The voltage detection circuit as claimed in claim 1, further comprising a second predetermined threshold for generating a second indication signal when the minimum cell voltage of said plurality of cell voltages is lower than said second predetermined threshold.

11. A method for protecting a multi-cell battery pack which includes a plurality of battery cells including a first to an N^th battery cell, said method comprising:

sensing a plurality of cell voltages corresponding to said battery cells;

comparing said cell voltages with at least one predetermined voltage threshold simultaneously by comparing the extremum of said plurality of cell voltages with said predetermined voltage threshold; and

generating a protection signal when said extremum crosses said predetermined voltage threshold.

12. The method as claimed in claim 11, further comprising:

converting said cell voltages to a plurality of cell currents; and

generating said protection signal when the extremum of said plurality of cell currents crosses a predetermined current threshold corresponding to said predetermined voltage threshold.

13. The method as claimed in claim 12, further comprising:

reconverting said cell currents to said cell voltages, wherein said cell voltages are ground-based.

14. A multi-cell battery pack protection circuit, comprising:

a plurality of battery cells including a first to an N^th battery cell coupled in series with each other;

a voltage detection circuit coupled to said plurality of battery cells for detecting a plurality of cell voltages each corresponding to an individual battery cell of said battery cells and simultaneously comparing said cell voltages with a predetermined high-voltage threshold by comparing the maximum cell voltage of said plurality of cell voltages with said predetermined high-voltage threshold;

a charging switch coupled to said plurality of battery cells for controlling charging of said battery cells; and

a controller coupled to said voltage detection circuit and said charging switch for disabling said charging switch when said maximum cell voltage is greater than said predetermined high-voltage threshold.

15. The multi-cell battery pack protection circuit as claimed in claim 14, wherein said voltage detection circuit comprises a V-WTA network for simultaneously comparing said cell voltages with said predetermined high-voltage threshold and for generating an over-voltage protection (OVP) signal to said controller when said maximum cell voltage is greater than said predetermined high-voltage threshold.

16. The multi-cell battery pack protection circuit as claimed in claim 15, wherein said V-WTA network further comprises:

a threshold transistor for receiving said predetermined high-voltage threshold;

a first-gain stage coupled to said threshold transistor including a first to an N^th first-gain transistor for receiving said cell voltages of said first to said N^th battery cell respectively and for actuating a K^th first-gain transistor to amplify a voltage difference between said predetermined high-voltage threshold and a K^th cell voltage which is said minimum cell voltage and received by said K^th first-gain transistor when said K^th cell voltage is greater than said predetermined high-voltage threshold; and

a second gain stage coupled to said first gain stage including a first to an N^th second-gain transistor for actuating a K^th second-gain transistor corresponding to said K^th first-gain transistor to further amplify said voltage difference and for generating said OVP signal when said K^th cell voltage is lower than said predetermined high-voltage threshold, where K=1, 2, . . . N.

17. The multi-cell battery pack protection circuit as claimed in claim 14, further comprising:

a V-LTA network for simultaneously comparing said cell voltages with a predetermined low-voltage threshold and for generating an under-voltage protection (UVP) signal to said controller when a minimum cell voltage of said plurality of cell voltages is lower than said predetermined low-voltage threshold.

18. The multi-cell battery pack protection circuit as claimed in claim 17, wherein said V-LTA network comprises:

a threshold transistor for receiving said predetermined low-voltage threshold;

a first-gain stage coupled to said threshold transistor including a first to an N^th first-gain transistor for receiving said cell voltages of said first to said N^th battery cell respectively and for actuating a K^th first-gain transistor to amplify a voltage difference between said predetermined low-voltage threshold and a K^th cell voltage which is said minimum cell voltage and received by said K^th first-gain transistor when said K^th cell voltage is lower than said predetermined low-voltage threshold; and

a second gain stage coupled to said first gain stage including a first to an N^th second-gain transistor for actuating a K^th second-gain transistor corresponding to said K^th first-gain transistor to further amplify said voltage difference and for generating said UVP signal when said K^th cell voltage is lower than said predetermined low-voltage threshold, where K=1, 2, . . . N.

19. The multi-cell battery pack protection circuit as claimed in claim 17, further comprising:

a discharging switch coupled to said battery cells and said controller for controlling discharging of said battery cells, wherein said controller receives said UVP signal and controls said discharging switch in response to said UVP signal.

20. The multi-cell battery pack protection circuit as claimed in claim 14, wherein said voltage detection circuit comprises a V/I conversion network for converting said cell voltages into a plurality of cell currents.