Lithium electronic-mechanical automatic protection system (LEAPS)

• US 5,875,085 A
• Filed: 02/23/1996
• Issued: 02/23/1999
• Est. Priority Date: 02/23/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Farley, Joseph
• Primary Examiner(s): Gaffin, Jeffrey
• Assistant Examiner(s): JACKSON, STEPHEN W
• Application Number:
  US08/606,362
• Time in Patent Office: 1,096 Days
• Field of Search: 361/18, 361/82, 361/84, 361/115, 361/93, 361/91, 361/90, 361/92, 320/6, 320/31, 320/39
• US Class Current: 361/18
• CPC Class Codes: H01L 27/0248 for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
• CPC Class Codes: H01L 29/78 with field effect produced by an insulated gate H01L29/7725, H01L29/775, H01L29/778 take precedence
• 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 7/00714 in response to battery charging or discharging current

Abstract

This device includes, connected in parallel with each of the elements (I, II), corresponding shunt regulators (S11, R11, S21, R21) linked together in series, and the control electrodes of which are connected to networks of resistors which represent voltages of the elements which can be applied to respective comparators (C11, C12, C21, C22) of the lower and upper threshold voltages (Vth11, Vth12, Vth21, Vth22) of the elements with a reference voltage delivered by a reference voltage source (Vref), a switching MOSFET transistor (4), with low conduction resistance and with defined off-state impedance, connected between the most negative terminal of the set of elements (II) in series and the negative terminal (Vbat-) of the protection device and means of control of the MOSFET transistor from output signals from the comparators (C11, C12, C21, C22) in order to alter the state of the said MOSFET transistor (4) for the purpose of regulating the state of charge and of discharge of the elements (I, II). It makes it possible to use a common charger for NiCd and NiMH elements.

Claims

1. A battery module, comprising:

two rechargeable elements (I,II);

a protection circuit for protecting the rechargeable elements, the protection circuit further comprising;

connected in parallel with each of the elements (I;

II), corresponding shunt regulators (S11, R11, S21, R21) linked together in series, and the control electrodes of which are connected to networks of resistors which represent voltages of the rechargeable elements which can be applied to respective comparators (C11, C12, C21, C22) of the lower and upper threshold voltages (Vth11, Vth12, Vth2l, Vth22) of the rechargeable elements with a reference voltage delivered by a reference voltage source (Vref), a bi-directional switching element (4) with low conduction resistance and with off-state impedance in one direction of a near-infinite ohmic value and a defined off-state impedance in the other direction, connected between a most negative terminal of the set of rechargeable elements (II) in series and a negative terminal (vbat-) of the battery module and means of control of the switching element from output signals from the comparators (C11, C12, C21, C22) in order to alter the state of the said switching element (4) for the purpose of regulating the rate of charge and of discharge of the rechargeable elements (I, II).

2. Protection circuit according to claim 1, further comprising a constant gate-source voltage control means giving the MOSFET transistor (4) a resistance characteristic making it possible to use it as a current-detecting element in systems for measuring state of charge.

3. The protection circuit according to claim 1, further comprising a selection logic circuit (20, 22, 24, 26, 28, 30) for low- and high- voltage charge balancing, using the output signals from the comparators (C11, C12, C21, C22), which are driven logically in order to control the control electrodes of the shunt regulators (S11, S21).

4. The battery module according to claim 1, further comprising a non-volatile memory (40) for storing time and date data corresponding to the state of charge of the elements (I, II), and other parameters of the elements (I, II) relative to the technology of the elements and to the charge and discharge characteristics, the said memory (40) being connected to a temperature sensor (42), the said memory (40) and the said temperature sensor (42) being supplied with voltage by a common source (Vcc) external to the device.

5. The battery module of claim 1, further comprising an automatic charge control means making it possible to charge the battery module with a common charger for NiCd or NiMH rechargeable elements.

6. The battery module of claim 1, further comprising a thermal protection element (2) connected between a positive terminal (Vbat+) of the battery module and a positive terminal of the set of rechargeable elements (I, II).

7. The battery module of claim 6, wherein the thermal protection device is a bimetallic strip.

8. The battery module of claim 6, wherein the thermal protection device is a thermistor device with a positive temperature coefficient, made of polymer or ceramic.

9. The battery module according to claim 6, further comprising an electronic protection circuit (10) connected to the power supply terminals (vbat+, vbat-) of the module, wherein the electronic protection circuit is operable to actuate the thermal protection device in response to a detected condition and thereby interrupt current flowing to or from the battery module.

10. The battery module according to claim 9, further comprising a device (46) for displaying the state of charge according to the data contained in the memory (40) under the control of a charge-state switch (48).

11. The battery module according to claim 10, further comprising a voltage- and temperature-measuring circuit and a circuit with high time constant capable of being reset to zero which is comparable in time with the time for setting the oxidation-reduction potential, which can display the latter state of charge written into the memory (40) by an application, or after the recycling of the oxidation-reduction period, a state of charge corresponding to the voltage and to the temperature read when a charge changeover switch of the battery module is actuated.

12. A battery module, comprising:

one or more rechargeable elements;

a protection circuit for protecting the rechargeable elements, the protection circuit further comprising;

a bi-directional switching element with low conduction resistance and with off-state impedance in one direction of a near-infinite ohmic value and a defined off-state impedance in the other direction, connected in series with the one or more rechargable elements and a terminal of the battery module; and

control circuitry connected to a control terminal of the bi-directional switching element operable to alter the state of the the switching element for the purpose of regulating the rate of charge and of discharge of the one or more rechargeable elements.

13. The battery module of claim 12, further comprising an automatic charge control means making it possible to charge the battery module with a common charger for NiCd or NiMH rechargeable elements.

14. The battery module of claim 12, wherein:

the bidirectional switching element is a MOS device; and

the protection circuit further comprises a constant gate-source voltage control circuit connected to a gate and source of the bi-directional switching element, the bi-directional switching element having a resistance characteristic such that the bi-directional switching element is operable as a current-detecting element.

15. The battery module of claim 12, wherein the protection circuit further comprises a mechanical protection element connected in series with the one or more rechargeable elements and the terminal of the battery module, the mechanical protection element being operable to interrupt a current flowing through the one or more rechargeable elements in response to one of the rechargeable elements having an abnormally high temperature.

16. The battery module of claim 15, wherein the protection circuit further comprises an electronic protection circuit connected to the mechanical protection element, the electronic protection circuit being operable to sense an abnormally high current flowing through the bi-directional switching element and to cause the mechanical protection element to interrupt current flowing through the one or more rechargeable elements.

17. The battery module of claim 12, further comprising a non-volatile memory (40) for storing parameters relative to the technology of the one or more rechargeable elements and relative to the charge and discharge characteristics corresponding to the state of charge of the one or more rechargeable elements.

18. The battery module according to claim 17, further comprising a device for displaying a state of charge according to the data contained in the non-volatile memory.

19. The battery module of claim 18, further comprising a voltage- and temperature-measuring circuit.