TEMPERATURE-BASED CHARGE AND DISCHARGE CONTROL FOR A BATTERY

• US 20080018304A1
• Filed: 07/24/2006
• Published: 01/24/2008
• Est. Priority Date: 07/24/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Idzik, Jacek S., Litingtun, Siong
• Granted Patent: US 7,808,212 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

A protection circuit for a battery pack, comprising: a thermistor for indicating a temperature of a cell in the battery pack; a first comparator coupled to the thermistor for determining whether the temperature has exceeded a charge cut-off temperature threshold for the cell, and if so, for turning off a first switch in series with the cell to prevent: charging of the cell; and, a second comparator coupled to the thermistor for determining whether the temperature has exceeded a discharge cut-off temperature threshold for the cell, and if so, for turning off a second switch in series with the cell to prevent discharging of the cell.

Claims

1. A protection circuit for a battery pack, comprising:

a thermistor for indicating a temperature of a cell in the battery pack;

a first comparator coupled to the thermistor for determining whether the temperature has exceeded a charge cut-off temperature threshold for the cell, and if so, for turning off a first switch in series with the cell to prevent charging of the cell; and

,

a second comparator coupled to the thermistor for determining whether the temperature has exceeded a discharge cut-off temperature threshold for the cell, and if so, for turning off a second switch in series with the cell to prevent discharging of the cell.

2. The protection circuit of claim 1 and further comprising first and second resistors coupled to the first and second comparators, respectively, for establishing the charge and discharge cut-off temperature thresholds, respectively.

3. The protection circuit of claim 2 wherein the temperature is a voltage indicative of the temperature, wherein the charge cut-off temperature threshold is a voltage indicative of the charge cut-off temperature threshold, and wherein the discharge cut-off temperature threshold is a voltage indicative of the discharge cut-off temperature threshold.

4. The protection circuit of claim 2 and further comprising an integrated circuit having at least one of:

a module for determining whether the cell has exceeded an over-voltage threshold, and if so, for turning off the first switch;

a module for determining whether the cell has exceeded an over-current threshold, and if so, for turning off the second switch; and

, a module for determining whether the cell has exceeded an over-discharge threshold, and if so, for turning off the second switch.

5. The protection circuit of claim 4 and further comprising a thermal protector in series with the cell for determining whether the cell has exceeded an over-temperature threshold for the cell, and if so, for opening to prevent charging and discharging of the cell.

6. The protection circuit of claim 5 wherein the thermal protector is a fuse.

7. The protection circuit of claim 1 wherein the first and second switches are first and second metal-oxide semiconductor field-effect transistors (“

MOSFETS”

).

8. The protection circuit of claim 1 wherein the thermistor is one of a negative temperature coefficient (“

NTC”

) type thermistor and a positive temperature coefficient (“

PTC”

) type thermistor.

9. The protection circuit of claim 1 wherein the cell is one of a lithium (“

Li-Ion”

) cell and a lithium-ion polymer cell.

10. The protection circuit of claim 2 wherein the battery pack is a battery pack for a wireless device, wherein the protection circuit is included in the battery pack, and wherein the thermistor is in contact with the cell.

11. A method for controlling charging and discharging of a battery pack, comprising:

receiving from a thermistor a temperature of a cell in the battery pack;

determining with a first comparator coupled to the thermistor whether the temperature has exceeded a charge cut-off temperature threshold for the cell, and if so, turning off a first switch in series with the cell to prevent charging of the cell; and

,

determining with a second comparator coupled to the thermistor whether the temperature has exceeded a discharge cut-off temperature threshold for the cell, and if so, turning off a second switch in series with the cell to prevent discharging of the cell.

12. The method of claim 11 and further comprising establishing the charge and discharge cut-off temperature thresholds with first and second resistors, respectively, coupled to the first and second comparators, respectively.

13. The method of claim 12 wherein the temperature is a voltage indicative of the temperature, wherein the charge cut-off temperature threshold is a voltage indicative of the charge cut-off temperature threshold, and wherein the discharge cut-off temperature threshold is a voltage indicative of the discharge cut-off temperature threshold.

14. The method of claim 12 and further comprising at least one of:

determining whether the cell has exceeded an over-voltage threshold, and if so, turning off the first switch;

determining whether the cell has exceeded an over-current threshold, and if so, turning off the second switch; and

, determining whether the cell has exceeded an over-discharge threshold, and if so, turning off the second switch.

15. The method of claim 14 and further comprising determining with a thermal protector in series with the cell whether the cell has exceeded an over-temperature threshold for the cell, and if so, opening the thermal protector to prevent charging and discharging of the cell.

16. The method of claim 15 wherein the thermal protector is a fuse.

17. The method of claim 11 wherein the first and second switches are first and second metal-oxide semiconductor field-effect transistors (“

MOSFETS”

).

18. The method of claim 11 wherein the thermistor is one of a negative temperature coefficient (“

NTC”

) type thermistor and a positive temperature coefficient (“

PTC”

) type thermistor.

19. The method of claim 11 wherein the cell is one of a lithium (“

Li-Ion”

) cell and a lithium-ion polymer cell.

20. The method of claim 12 wherein the battery pack is a battery pack for a wireless device, wherein the protection circuit is included in the battery pack, and wherein the thermistor is in contact with the cell.