Deep under voltage recovery in a battery pack

• US 20070210757A1
• Filed: 03/10/2006
• Published: 09/13/2007
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated), Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Gangstoe, Gunnar, Aas, Arne, Kastnes, Paal
• Granted Patent: US 7,605,568 B2
• Time in Patent Office: Days
• US Class Current: 320/130
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 7/0036 using connection detecting circuits H02J7/0034 takes precedence
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation

Abstract

In one implementation, a method for charging a battery system is provided. The method includes enabling determining if a charger is coupled to a battery system, the battery system including one or more cells and a charge enable transistor. The method also includes enabling determining if a voltage level of the cells is less than a predetermined first low voltage level. If the voltage level of the cells is less than the predetermined first low voltage level, enabling charging of the cells at a reduced rate including adjusting a voltage applied to the charge transistor gate terminal to regulate a voltage seen by the charger to a level that is less than a predetermined second voltage level. Additionally, when the voltage of the cells reaches the predetermined first low voltage level, the method includes substantially fully enabling the charge transistor to allow for charging at full rate by the charger.

Claims

1. A method for charging a battery system comprising:

enabling determining if a charger is coupled to a battery system, the battery system including one or more cells and a charge enable transistor;

enabling determining if a voltage level of the cells is less than a predetermined first low voltage level;

if so, enabling charging of the cells at a reduced rate including adjusting a voltage applied to the charge transistor gate terminal to regulate a voltage seen by the charger to a level that is less than a predetermined second voltage level; and

when the voltage of the cells reaches the predetermined first low voltage level, substantially fully enabling the charge transistor to allow for charging at full rate by the charger.

2. The method of claim 1 where adjusting a voltage applied to the gate terminal of the charge transistor includes partially enabling the charge transistor.

3. The method of claim 2 where partially enabling the charge transistor includes partially enabling the charge transistor until a voltage of the cells exceeds the predetermined first low voltage level.

4. The method of claim 2 where partially enabling the charge transistor includes adjusting a potential across the charge transistor to be higher than a difference between a potential of the cells and a minimum operating voltage required to power battery system monitor circuitry of the battery system.

5. The method of claim 2 where partially enabling the charge transistor includes adjusting a potential across the charge transistor so the voltage seen by the charger is lower than a voltage level where the charger switches from a reduced charge rate to a normal charge rate.

6. The method of claim 1 where the battery system includes a battery management system including battery monitoring circuitry and where adjusting a voltage applied to the charge transistor includes adjusting a drive signal to the charge transistor to maintain a voltage seen at an input to the battery management system at a level higher than a minimum operating voltage for the battery management system.

7. The method of claim 1 where the battery system includes a battery management system including battery monitoring circuitry and where adjusting a voltage applied to the charge transistor includes adjusting a drive signal to the charge transistor to maintain a voltage seen at an input to the battery management system at a level that is lower than a voltage level where the charger will switch from a reduced charge rate to a normal charge rate.

8. The method of claim 1 further comprising:

prior to charging the cells at a reduced rate, enabling monitoring circuitry in the battery system; and

monitoring the reduced rate charging of the cells.

9. The method of claim 8 further comprising safety monitoring the battery system while charging.

10. The method of claim 8 further comprising monitoring a change in a capacity of the cells of the battery system while charging.

11. The method of claim 1 where adjusting a voltage applied to the charge transistor includes determining if an operating voltage of the battery system is above a predefined maximum, and if so, increasing a drive voltage presented to the charge transistor.

12. The method of claim 1 where adjusting a voltage applied to the charge transistor includes determining if an operating voltage of the battery system is below a predefined minimum, and if so, decreasing a drive voltage presented to the charge transistor.

13. A method for charging a battery system comprising:

enabling determining if a charger is coupled to a battery system, the battery system including one or more cells, a charge enable transistor, and charge monitor control circuitry;

enabling the charge monitor control circuitry prior to enabling charging of the cells;

enabling determining if a voltage level of the cells is less than a predetermined first low voltage level;

if so, enabling charging the cells at a reduced rate including partially enabling the charge transistor; and

when the voltage of the cells reaches the predetermined first low voltage level, substantially fully enabling the charge transistor to allow for charging at full rate by the charger.

14. The method of claim 13 where partially enabling the charge transistor includes regulating a voltage seen by the charger to a level that is less than a predetermined second voltage level.

15. A method for charging a battery system comprising:

enabling determining if a charger is coupled to a battery system through a charge transistor;

enabling a charge transistor to a partially enabled state while one or more cells of a battery system are at a voltage that is less than a predetermined first threshold to allow for reduced rate charging; and

enabling the charge transistor to a fully enabled state if the determined voltage level is at or above the predetermined first threshold to allow for full rate charging.

16. A method comprising:

enabling determining that a charger has been coupled to a battery system, the battery system including one or more cells, monitoring circuitry for monitoring a charge level of the one or more cells, a charge transistor for enabling the charging of the one or more cells and a drive circuit for driving the charge transistor gate terminal;

monitoring the one or more cells voltage level and determining if the monitored voltage level is below a first threshold voltage level;

if so, enabling charging the cells at a reduced rate including partially enabling the charge transistor gate terminal; and

when the monitored voltage exceeds the first threshold voltage level, substantially completely enabling the charge transistor.

17. The method of claim 16 where enabling charging at a reduced rate includes regulating a voltage seen by the charger.

18. A battery management system comprising:

a monitor operable to detect a voltage level of one or more cells of a battery pack; and

a drive circuit operable to drive a charge transistor in one of at least three modes including being operable to;

drive the charge transistor in a first low-voltage mode including partially enabling the charge transistor to regulate the voltage seen by an external charger;

drive the charge transistor in a second off mode, to disable charging; and

drive the charge transistor in a third on mode, to enable full charging.

19. An apparatus comprising:

a high-side NFET charge transistor;

a drive circuit for driving the high side NFET charge transistor; and

a monitor circuit for monitoring a voltage level of a battery cell to be charged;

where the drive circuit is operable to partially enable the high side NFET charge transistor if the voltage level of the battery cell is below a first threshold level while in the presence of a charger.

20. An apparatus comprising:

a drive circuit for driving a charge transistor of a battery pack; and

a monitor circuit for monitoring a voltage level of a battery cell to be charged;

where the drive circuit is operable to partially enable the charge transistor if the voltage level of the battery cell is below a first threshold level while in the presence of a charger.

21. A method comprising:

monitoring a voltage level of cells associated with a battery pack to determine if the monitored voltage level is below a first threshold voltage level;

enabling determining if a charger is coupled to the battery pack; and

regulating a potential seen by the charger until a potential of the cells exceeds the first threshold level.