Battery pack and a battery charging/discharging circuit incorporating the same

• US 20040217737A1
• Filed: 05/02/2003
• Published: 11/04/2004
• Est. Priority Date: 05/02/2003
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Popescu, Serban-Mihai
• Granted Patent: US 6,850,039 B2
• Time in Patent Office: Days
• US Class Current: 320/128
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery pack including at least one battery cell; first and second battery selector switches configured to allow selective coupling of the battery cell to a power source or load for charging/discharging the battery cell; and a switch controller. The switch controller closes both of the switches to allow charging/discharging of the battery cell when a minimum charge/discharge current level is reached. A battery charging/discharging circuit including such a battery pack and a method of controlling the charging and discharging a battery cell in a battery pack are also provided.

Claims

1. A battery pack comprising:

at least one battery cell;

first and second switches configured to allow selective coupling of said battery cell to a load for discharging said battery cell and to allow selective coupling of said battery cell to a power source for charging said battery cell; and

a switch controller configured to close both of said switches to allow discharging of said battery cell when a discharging current through said cell reaches a predetermined minimum discharge current level and to close both of said switches to allow charging of said battery cell when a charging current through said cell reaches a predetermined minimum charge current level.

2. A battery pack according to claim 1, wherein said battery pack comprises a plurality of said battery cells.

3. A battery pack according to claim 1, wherein said first switch comprises a first transistor and said second switch comprises a second transistor, and wherein said switch controller is configured to close said first and second switches by placing said first and second transistors in a conducting state.

4. A battery pack according to claim 3, wherein said battery pack further comprises a first diode in parallel with said first transistor, and said second diode in parallel with said second transistor.

5. A battery pack according to claim 4, wherein said first diode is in reverse bias with said at least one battery cell, and said second diode is in forward bias with said at least one battery cell.

6. A battery pack according to claim 5, wherein said first and second transistors are field effect transistors, and wherein a source of said first transistor is coupled to a source of said second transistor.

7. A battery pack according to claim 6, wherein a drain of said first transistor is coupled to a positive battery terminal, and wherein a drain of said second transistor is coupled to said at least one battery cell.

8. A battery pack according to claim 7, wherein said switch controller is configured to provide first and second outputs, said first output being coupled to a gate of said first transistor for controlling a conduction state of said first transistor, and said second output being coupled to a gate of said second transistor for controlling a conduction state of said second transistor.

9. A battery pack according to claim 1, wherein said switch controller comprises a battery current monitor for monitoring said discharging current and said charging current, and wherein said switch controller is configured to close said switches in response to an output of said battery current monitor.

10. A battery pack according to claim 9, wherein battery current monitor comprises:

a first comparator configured to compare a discharge reference voltage with a voltage across a sense impedance in series with said at least one battery cell; and

a second comparator configured to compare a charge reference voltage with said voltage across said sense impedance.

11. A battery pack according to claim 1, wherein said switch controller is configured to receive a discharge signal and a charge signal, and wherein said switch controller is configured to close a first one of said switches in response to said discharge signal when said discharging current has not reached said discharge current level and to close both of said switches when said discharging current through said cell reaches said predetermined level, and wherein said switch controller is configured to close a second one of said switches in response to said charge signal when said charging current has not reached said predetermined level and to close both of said switches when said charging current through said cell reaches said charge current level.

12. A battery pack according to claim 11, wherein said switch controller comprises a charge/discharge circuit for providing said discharge signal and said charge signal.

13. A battery pack according to claim 1, wherein said battery pack comprises a protection circuit for monitoring said a voltage across said cell and providing an output indicating when a maximum cell voltage is reached, and wherein said switch controller is configured to close both of said switches when said charging current through said cell reaches said minimum charge current level and when said maximum cell voltage has not been reached.

14. A battery pack according to claim 13, wherein said output comprises an output of a comparator configured to compare a reference voltage with a voltage said at least one battery cell.

15. A battery pack according to claim 1, wherein said battery pack comprises a protection circuit for monitoring said discharging current and providing an output indicating when a maximum discharge current is reached, and wherein said switch controller is configured to close both of said switches when said discharging current through said cell reaches said discharge current level and when said maximum discharge current has not been reached.

16. A battery pack according to claim 15, wherein said output comprises an output of a comparator configured to compare a reference voltage with a voltage across a sense impedance in series with said at least one battery cell.

17. A battery pack comprising:

at least one battery cell;

first and second transistors configured to allow selective coupling of said battery cell to a load for discharging said battery cell and to allow selective coupling of said battery cell to a power source for charging said battery cell;

a first diode in parallel with said first transistor and in reverse bias with said battery cell, and a second diode parallel with said second transistor and in forward bias with said battery cell; and

a switch controller configured to cause said first and second transistors to conduct for allowing discharging of said battery cell in response to a discharge signal and a discharge current signal, said discharge current signal comprising a first output of a battery current monitor indicating that a discharge current through said cell has reached a predetermined minimum discharge current level,

said switch controller being further configured to cause said first and second transistors to conduct for allowing charging of said battery cell in response to a charge signal an a charge current signal, said charge current signal comprising a second output of said battery current monitor indicating that a charge current through said cell has reached a predetermined minimum charge current level.

18. A battery pack according to claim 17, wherein said battery pack comprises a plurality of said battery cells.

19. A battery pack according to claim 17, wherein said first and second transistors are field effect transistors, and wherein a source of said first transistor is coupled to a source of said second transistor.

20. A battery pack according to claim 19, wherein a drain of said first transistor is coupled to a positive battery terminal, and wherein a drain of said second transistor is coupled to said at least one battery cell.

21. A battery pack according to claim 20, wherein said switch controller is configured to provide first and second outputs, said first output being coupled to a gate of said first transistor for controlling a conduction state of said first transistor, and said second output being coupled to a gate of said second transistor for controlling a conduction state of said second transistor.

22. A battery pack according to claim 21, wherein said first output comprises an output of a first comparator configured to compare a discharge reference voltage with a voltage across a sense impedance in series with said at least one battery cell;

and said second output comprises an output of a second comparator configured to compare a charge reference voltage with said voltage across said sense impedance.

23. A battery pack according to claim 17, wherein said switch controller comprises a charge/discharge circuit for providing said discharge signal and said charge signal.

24. A battery charging/discharging circuit comprising:

a plurality of battery packs, each of said battery packs comprising,

at least one battery cell,

first and second battery selector switches configured to allow selective coupling of said battery cell to a load for discharging said battery cell and to allow selective coupling of said battery cell to a power source for charging said battery cell, and

a switch controller configured to close said first and second battery selector switches to allow discharging of said battery cell when a discharging current through said cell reaches a predetermined minimum discharge current level and to close said first and second battery selector switches to allow charging of said battery cell when a charging current through said cell reaches a predetermined minimum charge current level;

a discharge switch for selectively coupling said battery packs to said load along a discharging path for discharging said battery packs; and

a charge switch for selectively coupling said battery packs to said power source along a charging path.

25. A circuit according to claim 24, said circuit further comprising a charge control circuit configured to selectively control the conduction state of said discharge switch and said charge switch in response to a control signal indicative of the presence of said power source.

26. A circuit according to claim 24, wherein said charge switch comprises a first transistor and a first diode in parallel with said first transistor, said first diode being in reverse bias with said power source, and wherein said discharge switch comprises a second transistor and a second diode in parallel with said second transistor, said second diode being in reverse bias with said power source.

27. A circuit according to claim 24, wherein said power source includes an AC/DC adapter.

28. A circuit according to claim 24, wherein said charge path comprises a converter circuit for generating a DC charging current from said power source.

29. A circuit according to claim 28, wherein said converter circuit includes a buck converter circuit comprising an inductor coupled to said charge switch and said battery packs, a capacitor coupled to said inductor and said battery packs, and a diode coupled to said inductor and said charge switch.

30. A circuit according to claim 24, wherein at least one of said battery packs comprises a plurality of said battery cells.

31. A circuit according to claim 24, wherein said first battery selector switch comprises a first transistor and said second battery selector switch comprises a second transistor and wherein said switch controller is configured to close said first and second battery selector switches by placing said first and second transistors in a conducting state.

32. A circuit according to claim 31, wherein each said battery pack further comprises a first diode in parallel with said first transistor, and said second diode in parallel with said second transistor.

33. A circuit according to claim 32, wherein said first diode is in reverse bias with said at least one battery cell, and said second diode is in forward bias with said at least one battery cell.

34. A circuit according to claim 33, wherein said first and second transistors are field effect transistors, and wherein a source of said first transistor is coupled to a source of said second transistor.

35. A circuit according to claim 34, wherein a drain of said first transistor is coupled to a positive battery terminal, and wherein a drain of said second transistor is coupled to said at least one battery cell.

36. A circuit according to claim 35, wherein said switch controller is configured to provide first and second outputs, said first output being coupled to a gate of said first transistor for controlling a conduction state of said first transistor, and said second output being coupled to a gate of said second transistor for controlling a conduction state of said second transistor.

37. A circuit according to claim 24, wherein said switch controller comprises a battery current monitor for monitoring said discharging current and said charging current, and wherein said switch controller is configured to close said battery selector switches in response to an output of said battery current monitor.

38. A circuit according to claim 37, wherein said battery current monitor comprises:

a first comparator configured to compare a discharge reference voltage with a voltage across a sense impedance in series with said at least one battery cell; and

a second comparator configured to compare a charge reference voltage with said voltage across said sense impedance.

39. A circuit according to claim 24, wherein said switch controller is configured to receive a discharge signal and a charge signal, and wherein said switch controller is configured to close a first one of said battery selector switches in response to said discharge signal when said discharging current has not reached said discharge current level and to close both of said battery selector switches when said discharging current through said cell reaches said predetermined level, and wherein said switch controller is configured to close a second one of said battery selector switches in response to said charge signal when said charging current has not reached said predetermined level and to close both of said battery selector switches when said charging current through said cell reaches said charge current level.

40. A circuit according to claim 39, wherein said switch controller comprises a charge/discharge circuit for providing said discharge signal and said charge signal.

41. A circuit according to claim 24, wherein at least one of said battery packs comprises a protection circuit for monitoring said a voltage across said cell and providing an output indicating when a maximum cell voltage is reached, and wherein said switch controller is configured to close both of said battery selector switches when said charging current through said cell reaches said minimum charge current level and when said maximum cell voltage has not been reached.

42. A circuit according to claim 41, wherein said output comprises an output of a comparator configured to compare a reference voltage with a voltage said at least one battery cell.

43. A circuit according to claim 24, wherein at least one of said battery packs comprises a protection circuit for monitoring said discharging current and providing an output indicating when a maximum discharge current is reached, and wherein said switch controller is configured to close both of said battery selector switches when said discharging current through said cell reaches said discharge current level and when said maximum discharge current has not been reached.

44. A circuit according to claim 43, wherein said output comprises an output of a comparator configured to compare a reference voltage with a voltage across a sense impedance in series with said at least one battery cell.

45. A method of controlling the charging and discharging a battery cell in a battery pack, said method comprising:

providing first and second battery selector switches in said battery pack;

closing said first and second battery selector switches to charge said battery pack when a predetermined charge current through said battery cell is achieved; and

closing said first and second battery selector switches to discharge said battery pack when a predetermined discharge current through said battery cell is achieved.

46. A method according to claim 45, said method further comprising providing a first diode in parallel with said first switch and a second diode in parallel with said second switch, said first diode being in forward bias with said battery cell and said second diode being in reverse bias with said battery cell.

47. A method according to claim 45, wherein said first switch comprises a first transistor and said second switch comprises a second transistor.

48. A method according to claim 47, wherein said first and second transistors are field effect transistors, and wherein a source of said first transistor is coupled to a source of said second transistor.

49. A method according to claim 48, wherein a drain of said first transistor is coupled to a positive battery terminal, and wherein a drain of said second transistor is coupled to said at least one battery cell.

50. A battery pack comprising:

at least one battery cell;

battery selector switch means for allowing selective coupling of said battery cell to a load for discharging said battery cell and selective coupling of said battery cell to a power source for charging said battery cell; and

switch controller means for closing said battery selector switch means to allow discharging of said battery cell when a discharging current through said cell reaches a predetermined discharge current level and for closing said battery selector switch means to allow charging of said battery cell when a charging current through said cell reaches a predetermined charge current level.