Protective circuit for energy-storage device

• US 20090200986A1
• Filed: 02/08/2008
• Published: 08/13/2009
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Sion Power Corporation
• Original Assignee: Sion Power Corporation
• Inventors: Kopera, John Joseph Christopher
• Granted Patent: US 8,264,205 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00306 Overdischarge 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
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method and apparatus for protecting an energy-storage device (ESD), such as a rechargeable battery, is provided. A protective circuit protects an ESD from adverse charging and loading conditions including overcharging, overdischarging, charging at an excessive rate and discharging at an excessive rate. The protective circuit selectively disables charging and discharging based on the present terminal conditions. A plurality of ESDs and protective circuits can be interconnected to protect a multi-cell ESD device. Embodiments of the protective circuit are adapted to protect a lithium cell operating around 2 volts. The protective circuit may also protect the ESD from adverse temperature conditions.

Claims

1. A protective circuit for an energy-storage device, comprising:

a charge protection circuit adapted to disable current flow into the energy-storage device and allow current to flow out of the energy-storage device while a voltage corresponding to an overcharge state of energy-storage device is detected; and

a discharge protection circuit adapted to disable current flow out of the energy-storage device when a voltage corresponding to an overdischarged state of the energy-storage device is detected until a voltage corresponding to an operating range of the energy-storage device is detected and allow current to flow into the energy-storage device while a voltage corresponding to an overdischarged state of the energy-storage device is detected.

2. The protective circuit of claim 1, wherein the discharge protection circuit comprises a p-channel FET.

3. The protective circuit of claim 2, wherein the p-channel FET is adapted and configured to selectively disable current flow out of the energy-storage device.

4. The protective circuit of claim 2, wherein the charge protection circuit comprises an n-channel FET adapted and configured to disable current flow into the energy-storage device.

5. The protective circuit of claim 1, wherein the discharge protection circuit comprises an n-channel FET and the charge protection circuit comprises an n-channel FET.

6. The protective circuit of claim 1, wherein the energy-storage device is a rechargeable battery.

7. The protective circuit of claim 6, wherein, the operating range is between 1.5 and 2.5 volts.

8. The protective circuit of claim 6, wherein the overcharged state comprises a voltage over 2.65 volts and the overdischarged state comprises voltages under 1.40 volts.

9. The protective circuit of claim 1, in combination with a charging circuit and a rechargeable lithium battery cell wherein the protective circuit is electrically coupled between the rechargeable battery cell and the protective circuit.

10. An apparatus comprising a plurality of energy-storage devices and a plurality of protective circuits, each energy-storage device comprising a first terminal and a second terminal and each protective circuit having a first terminal and a second terminal coupled to the first terminal and the second terminal, respectively, of energy-storage device of the plurality of energy-storage device, each protective circuit comprising:

a third terminal;

a fourth terminal;

a first directional element coupled between the first terminal and the third terminal of the protective circuit adapted and configured to allow current flow in a first direction between the first terminal and the third terminal;

a first switch coupled between the first terminal and the third terminal of the protective circuit in parallel with the first directional element, the first switch having a control input, the first switch being adapted and configured to selectively block current flow in response to a value in a first state at the control input of the first switch;

an overdischarge detector having an input coupled between the third terminal and the fourth terminal of the protective circuit, the overcharge detector having an output coupled to the control input of the first directional switch, the output of the overdischarge detector having a value in the first state when the voltage at the input of the overdischarge detector drops below a value corresponding to an overdischarge state and a value other than in the first state when the voltage at the input of the overdischarge detector raises to a voltage corresponding to an operating range;

a second directional element coupled between the first terminal and the fourth terminal of the protective circuit, the second directional element being adapted and configured to allow current flow in a second direction between the second terminal and the fourth terminal;

a second switch coupled between the second terminal and the fourth terminal of the protective circuit in parallel with the second directional element, the second switch having a control input, the second directional switch adapted and configured to block current flow between the second terminal and the fourth terminal in response to a value in a second state at the control input of the second switch; and

an overcharge detector having an input coupled between the second terminal and the fourth terminal of the protective circuit, the overcharge detector having an output coupled to the control input of the second switch, the output of the overcharge detector having a value in the second state when the voltage at the input of the overcharge detector increases above a value corresponding to an overcharge state.

11. The apparatus of claim 10, wherein each protective circuit further comprises an over-temperature detector coupled to the control input of the first switch and the control input of the second switch, the over-temperature detector adapted and configured to provide a value in the first state to the control input of the first switch and a value in the second state to the control input of the second switch when the temperature is outside an acceptable range.

12. The apparatus of claim 10, wherein the first switch comprises a p-channel FET.

13. The apparatus of claim 12, wherein second switch comprises an n-channel FET.

14. The apparatus of claim 10, wherein the first switch comprises an n-channel FET.

15. The apparatus of claim 14, wherein second switch comprises a p-channel FET.

16. The apparatus of claim 10, wherein at least a portion of the plurality of protective circuits are connected in parallel.

17. The apparatus of claim 10, wherein at least a portion of the plurality of protective circuits are connected in series.

18. The apparatus of claim 10, wherein the plurality of energy-storage devices comprise lithium cells.

19. The apparatus of claim 10, further comprising a package;

and

wherein at least one of the plurality of energy-storage devices and at least one of the plurality of protective circuits is disposed within the package.

20. The apparatus of claim 10, wherein each protective circuit further comprise an anti-parallel diode coupled between the third terminal and the fourth terminal.

21. A method of operating a protective circuit for an energy-storage device, the method comprising:

sensing a voltage applied across terminals coupled to an energy-storage device;

disabling current flow into the energy-storage device and allowing current flow out of the energy-storage device while a voltage corresponding to an overcharge state of the energy-storage device is sensed; and

disabling current flow out of the energy-storage device when a voltage corresponding to an overdischarged state of the energy-storage device is detected until a voltage corresponding to an operating range of the energy-storage device is sensed and allowing current to flow into the energy-storage device while a voltage corresponding to an overdischarged state of the energy-storage device is sensed.

22. The method of claim 21, further comprising:

monitoring a temperature; and

disconnecting the energy-storage device when the monitored temperature is outside an allowed temperature range.

23. The method of claim 21, wherein disabling current flow out of the energy-storage device comprises placing a p-channel FET in a non-conductive state.

24. The method of claim 23, wherein disabling current flow into the energy-storage device comprises placing an n-channel FET in a non-conductive state.

25. The method of claim 23, wherein the energy-storage device is a lithium battery.

26. The method of claim 25, wherein lithium battery has an operating range between 1.5 and 2.5 volts.

27. The battery protective circuit of claim 25, wherein the overcharged state comprises voltages over 1.65 volts and the overdischarged state comprises voltages under 1.40 volts.

28. The method of claim 21, wherein disabling current flow out of the energy-storage device comprises placing an n-channel FET in a non-conductive state.

29. The method of claim 28, wherein disabling current flow into the energy-storage device comprises placing a p-channel FET in a non-conductive state.