Circuit and device for protecting secondary battery

• US 6,577,105 B1
• Filed: 01/11/2001
• Issued: 06/10/2003
• Est. Priority Date: 05/17/1999
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Iwaizono, Yoshinori
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/743,539
• Time in Patent Office: 880 Days
• Field of Search: 320/127, 320/128, 320/134, 320/136, 320/150, 320/153
• US Class Current: 320/134
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 2200/106 PTC
• CPC Class Codes: H01M 50/581 in response to temperature
• 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 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A protective circuit for protecting a rechargeable battery from battery breakdown caused by prolonged overcharging, and a protective element incorporated in this circuit are provided. A main protective circuit is equipped with main control means for shutting off a first FET or a second FET when any of overcharging, overdischarging, or excessive discharge current is detected. A sub-protective circuit is equipped with sub-control means for shutting off a third FET when the anti-overcharging function of the main control means is not operating properly.

Claims

1. A battery protective circuit incorporated in a rechargeable battery, comprising:

a charge/discharge circuit including;

a first switching means for protecting the rechargeable battery from overcharging; and

a second switching means for protecting he rechargeable battery from overdischarging connected in series with the first switching means in the charge/discharge circuit of the rechargeable battery;

a main protective circuit for;

detecting a battery voltage between positive and negative electrodes of the rechargeable battery;

turning on the first switching means when the battery voltage is below a charge-prohibiting voltage, above which charging of the rechargeable battery must be prohibited; and

turning off the first switching means when the battery voltage is detected to be higher than said charge-prohibiting voltage, and maintaining the OFF state of the first switching means until the detected voltage becomes below a charge-permitting voltage that is lower than said charge-prohibiting voltage; and

a sub-protective circuit for;

detecting the battery voltage between the positive and negative electrodes of the rechargeable battery;

turning on the second switching means when the battery voltage is below a second charge-prohibiting voltage which is higher than the first charge-prohibiting voltage; and

turning off the second switching means when the battery voltage is detected to be higher than the second charge-prohibiting voltage.

2. The battery protective circuit according to claim 1, wherein the sub-protective circuit maintains the OFF state of the second switching means until a second charge-permitting voltage, which is lower the second charge-prohibiting voltage, is detected.

3. The battery protective circuit according to claim 1, wherein the sub-protective circuit fixes the OFF state of the second switching means after the second charge-prohibiting voltage has been detected.

4. The battery protective circuit according to claim 1, wherein the first switching means and second switching means include power MOSFETs having parasitic diodes therein, wherein said first switching means and second switching means are connected such that the forward direction of the parasitic diodes is the discharge direction of the rechargeable battery.

5. A battery protective circuit incorporated in a rechargeable battery, comprising:

a charge/discharge circuit including;

a first switching means for protecting against excessively large current; and

a second switching means for preventing overcharging connected in series with the first switching means in the charge/discharge circuit of the rechargeable battery;

a main protective circuit for controlling the first switching means in accordance with a battery voltage across positive and negative electrodes of the rechargeable battery and a discharge current of the rechargeable battery; and

a sub-protective circuit for controlling the second switching means in accordance with the battery voltage across positive and negative electrodes of the rechargeable battery, wherein;

the first switching means and the second switching means are turned on, when the rechargeable battery is in a normal condition wherein the voltage across the positive and negative electrodes of the rechargeable battery is within range above a discharge-prohibiting voltage and below a first charge-prohibiting voltage, said discharge-prohibiting voltage being a limit value below which discharging of the rechargeable battery must be prohibited, and said charge-prohibiting voltage being a limit value above which charging of the rechargeable battery must be prohibited;

the first switching means is turned OFF, when the detected discharge current is above a predetermined value;

the first switching means is put in a charging direction OFF/discharging direction ON state when the detected voltage is above said first charge-prohibiting voltage, and maintained in said charging direction OFF/discharging direction ON state until a first charge-permitting voltage, that is lower than the first charge-prohibiting voltage, is detected;

the first switching means is put in a discharging direction OFF/charging direction ON state when the deleted voltage is below said discharge-prohibiting voltage, and maintained in said discharging direction OFF/charging direction ON state until a discharge-permitting voltage, that is higher than said discharge-prohibiting voltage is detected; and

the second switching means is turned off when the detected voltage is above a second charge-prohibiting voltage, which is higher than said first charge-prohibiting voltage, and maintained in the OFF state until a second charge-permitting voltage, that is lower than said second charge-prohibiting voltage, is detected.

6. The battery protective circuit according to claim 5, wherein the first switching means is an FET with no parasitic diode therein, and controlled in accordance with gate voltage thereof.

7. A battery protective circuit incorporated in a rechargeable battery, comprising:

a charge/discharge circuit for the rechargeable bakery including;

a PTC device connected in the charge/discharge circuit of the rechargeable battery;

a heating means heat-coupled to the PTC element;

a first switching means connected in series to the PTC device for controlling power supply to said heating means;

a second switching means for preventing overcharging connected in series with the first switching means in the charge/discharge circuit of the rechargeable battery;

a main protective circuit for;

detecting a battery voltage between positive and negative electrodes of the rechargeable battery;

turning off the first switching means when the detected voltage is below a first charge-prohibiting voltage, above which charging of the rechargeable battery must be prohibited; and

turning on the first switching means for supplying power to the heating means when the detected voltage is above the first charge-prohibiting voltage, and maintaining said ON state of the first switching means until a first charge-permitting voltage, that is lower than said first charge-prohibiting voltage, is detected; and

a sub-protective circuit for;

detecting the battery voltage between the positive and negative electrodes of the rechargeable battery;

turning on the second switching means when the detected voltage is below a second charge-prohibiting voltage that is higher than the first charge-prohibiting voltage; and

turning off the second switching means when the detected voltage is above the second charge-prohibiting voltage, and maintaining the OFF state of the second switching means until a second charge-permitting voltage, which is lower than said second charge-prohibiting voltage, is detected.

8. The battery protective circuit according to claim 7, wherein the heating means is a second PTC device heat-coupled to the first PTC device.

9. A battery protective circuit for a rechargeable battery, comprising:

voltage detection means connected in series between positive and negative electrodes of the rechargeable battery for detecting a battery voltage and outputting a control signal when a voltage exceeding a predetermined value is detected;

a PTC device serially connected to the voltage detection means;

heating means, which heats up by electrical conduction, connected to the voltage detection means and heat-coupled to the PTC device; and

switching means for turning on the heating means accordance with the control signal from the voltage detection means.

10. The battery protective circuit according to claim 9, wherein the voltage exceeding a predetermined value detected by the voltage detection means is set higher than the voltage at which an overcharging state is detected.

11. The battery protective circuit according to claim 9, wherein the heating means is a second PTC device heat-coupled to the PTC device.

12. A battery protective circuit for a rechargeable battery, comprising:

voltage detection means connected across positive and negative electrodes of a rechargeable battery for detecting a battery voltage and outputting a control signal when a voltage exuding a predetermined value is detected;

a temperature fuse serially connected to the rechargeable battery;

a heating PTC device heat-coupled to the temperature fuse; and

switching means for turning on the heating PC device in accordance with the control signal from the voltage detection means.

13. The battery protective circuit according to claim 12, wherein the voltage exceeding a predetermined value detected by the voltage detection means is set higher than the voltage at which an overcharging state is detected.

14. A protective element incorporate in a battery protective circuit for a rechargeable battery, comprising a plurality of PTC elements formed in a flat shape and laminated in a heat-coupled state.

15. The protective element according to claim 14, wherein the plurality of PTC elements have various different shapes, sizes, and electrical characteristics.

16. The protective element according to claim 14, wherein two PTC elements formed in a flat shape are joined together by means of an electrode material interposed between the flat sides thereof, each of the PTC elements being respectively provided with electrode materials joined to their outer sides.

17. The protective element according to claim 16, wherein the electrode materials are made from one of a copper-nickel alloy and a clad material made from a copper-nickel alloy and nickel.

18. The protective element according to claim 16, wherein leads are extended from the electrode materials.

19. The protective element according to claim 18, wherein the leads are extended from the electrode materials in two mutually opposite directions.

20. The protective element according claim 18, wherein the leads are severally formed extending from the electrode materials in different directions.

21. The protective element according claim 16, wherein the electrode materials are formed in smaller outer dimension than the PTC elements to which they are joined.

23. The protective element according to claim 14 or 22, wherein the heat-coupled portion is covered with a thermally insulating material.

22. A protective element incorporates in a battery protective circuit for a rechargeable battery, comprising a temperature fuse, and a PTC device heat-coupled to the temperature fuse.

24. A protective circuit comprising:

a main control means for detecting the voltage across the positive and negative leads of a battery;

a first switch;

a second switch;

the first switch being serially connected at a connection point to the second switch;

the connection point of the first switch and the second switch connecting to the main control means, wherein the main control means, the first switch and the second switch are connected to prevent overcharging of rechargeable battery.

25. A protective circuit according to claim 24, wherein the first switch and the second switch include power MOSFETs having parasitic diodes.

26. A protective circuit comprising:

a main control means for detecting the voltage across the positive and negative leads of a battery;

a first switch;

a protective element;

the first switch being serially connected to the protective element;

the main control means connecting to the first switch so that the main control means controls the first switch, wherein the main control means, the first switch and the protective element are connected to control power supply to the battery.

27. A protective circuit according claim 26, wherein the protective element includes a PTC device and a heating means heat coupled to the PTC device.

28. A protective circuit according to claim 27, further comprising a resistor coupled across the heating means.

29. A protective circuit according to claim 26, wherein the protective element includes a PTC device and a fuse.

30. A protective circuit according to claim 29, wherein the fuse is a temperature fuse.