Devices and methods for protection of rechargeable elements

• US 6,518,731 B2
• Filed: 10/30/2001
• Issued: 02/11/2003
• Est. Priority Date: 04/15/1998
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Tyco Electronics Corporation (TE Connectivity Ltd. (United Kingdom))
• Inventors: Thomas, Brian, Luan, Jiyuan, Thornton, Neill, Toth, James, Cogan, Adrian, Beaufils, Jean-Marc, Dallemange, Bernard, Gozlan, Gilles
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US10/017,931
• Publication Number:
  US 20020079865A1
• Time in Patent Office: 469 Days
• Field of Search: 320/136, 320/134, 320/135, 320/137, 320/127
• US Class Current: 320/136
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 25/16 the devices being of types provided for in two or more different main groups of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. forming hybrid circuits
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/1301 Thyristor
• CPC Class Codes: H01L 2924/13062 Junction field-effect transistor [JFET]
• CPC Class Codes: H01L 2924/13091 Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02H 9/042 comprising means to limit the absorbed power or indicate damaged over-voltage protection device
• 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 use with a charger and a chargeable element, such as a rechargeable lithium ion battery, comprises a shunt regulator having a threshold ON voltage coupled in parallel across the chargeable element, and a temperature-dependent resistor, e.g., a positive temperature coefficient device, coupled in series between the charger and the chargeable element. The temperature dependent resistor is thermally and electrically coupled to the shunt regulator, wherein the first variable resistor limits current flowing through the shunt regulator if the current reaches a predetermined level less than that which would cause failure of the regulator, due to ohmic heating of the regulator.

Claims

1. A protection device for use with a discharging load device, comprising:

a shunt regulator comprising a transistor switch;

a variable resistor having a first terminal, the variable resistor being thermally and electrically coupled to the shunt regulator;

a second terminal electrically coupled to the variable resistor; and

a third terminal electrically coupled to the transistor switch,

wherein the variable resistor limits current flowing through the transistor switch during an overvoltage or overcurrent condition before the current reaches a predetermined level sufficient to activate the transistor switch, and wherein an electrical path from the first terminal of the variable resistor to the third terminal is formed when the transistor switch is activated.

2. The protection device of claim 1, wherein the variable resistor comprises a positive temperature coefficient device.

3. The protection device of claim 1, wherein the variable resistor comprises a first electrode layer electrically coupled to the second terminal and a second electrode layer electrically coupled to the first terminal.

4. The protection device of claim 3, wherein the transistor switch is attached to a heat sink that is electrically and thermally coupled to the first electrode layer of the variable resistor.

5. The protection device of claim 1, wherein the variable resistor switches from a relatively low resistance to a relatively high resistance when heated to a certain transition temperature, and wherein current flowing through the transistor switch at the predetermined level causes ohmic heat generation in the transistor switch to cause the variable resistor to substantially reach its transition temperature.

6. The protection device of claim 1, wherein the shunt regulator further comprises control circuitry configured to activate the transistor switch.

7. The protection device of claim 1, wherein the transistor switch has a thermally-compensated voltage characteristic.

8. The protection device of claim 1, wherein the transistor switch is a MOSFET switch having a relatively high resistance, reverse-current body diode.

9. The protection device of claim 1, wherein the transistor switch having a channel through which current may flow in a forward direction if positive-biased, or a reverse direction if negative-biased, the switch being constructed such that current flowing in the forward direction encounters relatively low resistance, and current flowing in the reverse direction encounters relatively high resistance.

10. The protection device of claim 1, wherein the shunt regulator is configured to mount on a first side of a printed circuit board, and wherein the variable resistor is configured to mount to a second side of the printed circuit board.

11. The protection device of claim 10, wherein the first terminal is bonded to a first bond pad on the second side of the printed circuit board, the first bond pad being electrically coupled to a first conductive lead on the printed circuit board.

12. The protection device of claim 10, wherein the second terminal is bonded to a second bond pad on either the first side or the second side of the printed circuit board, the second bond pad being electrically coupled to a second conductive lead on the printed circuit board.

13. The protection device of claim 10, wherein the third terminal is bonded to a bond pad on the first side of the printed circuit board, the bond pad being electrically coupled to a third conductive lead on the printed circuit board.

14. The protection device of claim 10, wherein the variable transistor is configured to mount to a casing of a battery pack, and provides protection of the battery pack from an overtemperature condition.

15. The protection device of claim 1, wherein

the first terminal is configured for coupling to a positive terminal of the discharging load device, the second terminal is configured for coupling to a positive terminal of the chargeable element, and the third terminal is configured for coupling to a negative terminal of the discharging load device and a negative terminal of the chargeable element.

16. The protection device of claim 1, further comprising a second variable resistor coupled in series with the shunt regulator.

17. A protection circuit for use with a charger and a chargeable element, comprising:

a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator having a threshold ON voltage; and

a first variable resistor thermally and electrically coupled to the shunt regulator, the first variable resistor having a first terminal for coupling to the charger in series and a second terminal for coupling to the chargeable element in series,

wherein the first variable resistor limits current flowing through the shunt regulator during an overvoltage or overcurrent condition before the current reaches a level sufficient to cause the shunt regulator to fail, and

wherein the shunt regulator is configured to mount on a first side of a printed circuit board, and the first variable resistor is configured to mount to a second side of the printed circuit board.

18. The protection circuit of claim 17, wherein the first variable resistor switches from a relatively low resistance to a relatively high resistance when heated to a certain transition temperature, and wherein current flowing through the shunt regulator at the predetermined level causes ohmic heat generation in the shunt regulator to cause the first variable resistor to substantially reach its transition temperature.

19. The protection circuit of claim 17, wherein the first variable resistor comprises a positive temperature coefficient device.

20. The protection circuit of claim 17, wherein the shunt regulator comprises a transistor switch.

21. The protection circuit of claim 20, wherein the shunt regulator further comprises control circuitry configured to activate the transistor switch if the voltage across the chargeable element reaches the threshold ON voltage.

22. The protection circuit of claim 21, wherein the control circuitry comprises first and second voltage detection circuits, the first voltage detection circuit being relatively low leakage and the second voltage detection circuit being relatively precise, wherein the first voltage detection circuit is configured to activate the second voltage detection circuit if the voltage across the chargeable element approaches the threshold ON voltage, and wherein the second voltage detection circuit is configured to activate the transistor switch if the voltage across the chargeable element reaches the threshold ON voltage.

23. The protection circuit of claim 21, wherein the control circuitry comprises an operational amplifier having an output coupled to an activation gate of the transistor switch, and further comprising a voltage clamping element coupled to the operational amplifier output, the clamping element thereby clamping the activation gate voltage.

24. The protection circuit of claim 23, wherein the clamping element comprises a zener diode.

25. The protection circuit of claim 20, wherein the transistor switch has a thermally-compensated voltage characteristic.

26. The protection circuit of claim 17, further comprising undervoltage protection circuit.

27. The protection circuit of claim 26, wherein the undervoltage protection circuit comprises a transistor switch having a threshold ON voltage, and having source and drain terminals configured for coupling in series between the charger and the chargeable element.

28. The protection circuit of claim 27, wherein the undervoltage protection circuit further comprises control circuitry configured to turn the transistor switch ON if the voltage across the chargeable element is at or greater than a selected minimum voltage, and to turn the transistor switch OFF if the voltage across the chargeable element falls below the selected minimum voltage.

29. The protection circuit of claim 17, wherein the shunt regulator comprises a MOSFET switch having a relatively high resistance, reverse-current body diode.

30. The protection circuit of claim 17, wherein the shunt regulator comprises a transistor switch having a channel through which current may flow in a forward direction if positive-biased, or a reverse direction if negative-biased, the switch being constructed such that current flowing in the forward direction encounters relatively low resistance, and current flowing in the reverse direction encounters relatively high resistance.

31. The protection circuit of claim 17, further comprising a second variable resistor coupled in series with the shunt regulator.