CN216489799U

CN216489799U - Improved generation lithium cell protection circuit that charges

Info

Publication number: CN216489799U
Application number: CN202122201333.9U
Authority: CN
Inventors: 梁琪; 蔺会民; 王志云; 曾利强
Original assignee: Shenzhen Harding Energy Co ltd
Current assignee: Shenzhen Harding Energy Co ltd
Priority date: 2021-09-13
Filing date: 2021-09-13
Publication date: 2022-05-10
Anticipated expiration: 2031-09-13

Abstract

The utility model discloses an improved lithium battery charging protection circuit, relates to the technical field of new energy, and solves the technical problem that in the prior art, in order to meet the safety requirement in an excessive charging test of the existing lithium battery, the function of a battery core is influenced by changing the formula of the battery core or adding a temperature protection circuit, and the existing protection circuit needs to be improved. The battery protection circuit comprises a battery protection IC, a first MOS tube group Q1 and a second MOS tube group Q2; the first MOS tube bank Q1 and the second MOS tube bank Q2 are connected in series and then connected with the battery protection IC. The second MOS tube group Q2 is newly added, and the second MOS tube group Q2 is connected with the first MOS tube group Q1 in series. When the first MOS tube group Q1 fails, the second MOS tube group Q2 can normally protect the product and prevent the battery from being overcharged. When the safety requirement of the charge abuse experiment is met, the function of the battery cell is not influenced during electrification.

Description

Improved generation lithium cell protection circuit that charges

Technical Field

The utility model relates to the technical field of new energy, in particular to an improved lithium battery charging protection circuit.

Background

In the prior art, a very strict and careful battery safety design is carried out on a lithium battery so as to achieve the battery safety assessment index and ensure the safe and reliable use of the lithium battery. The battery safety assessment comprises an electrical test, a mechanical test, a battery shell test, a fire test and an environmental test. Among them, the charge abuse test is an important item in the electrical test.

The charge abuse test places a requirement on the lithium battery that overcharging with 2-rate constant current cannot explode or ignite in the event of failure of any one device. Each test cell was internally provided with a thermocouple to measure temperature. The test is continued until the battery explodes, leaks or the protection device acts, and the temperature of the internal battery reaches a stable state or is recovered to the ambient temperature.

In order to meet the requirements of the existing lithium battery in the charge abuse test, methods of changing the formula of a battery core or increasing the temperature to protect a circuit are mostly adopted. However, other properties of the cell, such as capacity reduction and service life reduction, may also be changed while changing the cell formulation. The addition of the temperature protection circuit increases the modal power consumption of the battery. The modal power consumption is a key parameter of the battery pack, and the increase of the modal power consumption can cause the increase of self-discharge of the battery pack and shorten the electric quantity retention time. In the process of implementing the utility model, the utility model people find that at least the following problems exist in the prior art:

in order to meet the safety requirement in the current lithium battery in the charge abuse test, the function of the battery core is affected by changing the formula of the battery core or adding a temperature protection circuit, and the current protection circuit needs to be improved.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide an improved lithium battery charging protection circuit, which aims to solve the technical problem that in order to meet the safety requirement of the existing lithium battery in the excessive charging test in the prior art, the function of a battery core is influenced by changing the formula of the battery core or adding a temperature protection circuit, and the existing protection circuit needs to be improved. The technical effects that can be produced by the preferred technical scheme in the technical schemes provided by the utility model are described in detail in the following.

In order to achieve the purpose, the utility model provides the following technical scheme:

the utility model provides an improved lithium battery charging protection circuit, which comprises a battery protection IC, a first MOS tube group Q1 and a second MOS tube group Q2; the first MOS tube bank Q1 is connected with the second MOS tube bank Q2 in series and then is connected with the battery protection IC; the models of the first MOS tube group Q1 and the second MOS tube group Q2 are 8205A; the first MOS tube group Q1 and the second MOS tube group Q2 are common-drain double-N-channel enhancement type field effect tubes; the first MOS tube group Q1 comprises a first sub MOS tube and a second sub MOS tube; the second MOS tube group Q2 comprises a third sub MOS tube and a fourth sub MOS tube; the improved lithium battery charging protection circuit also comprises a TH element; the TH element includes two NTC thermistors.

Preferably, the gates of the first sub-MOS transistor and the third sub-MOS transistor are connected to a DO pin of the battery protection IC; and the grids of the second sub MOS tube and the fourth sub MOS tube are connected with a CO pin of the battery protection IC.

Preferably, the source electrode of the first sub-MOS transistor is connected to a VSS pin of the battery protection IC; and the source electrode of the fourth sub MOS tube is connected with the VM pin of the battery protection IC.

Preferably, the drains of the first sub-MOS transistor and the second sub-MOS transistor are connected in series; the source electrodes of the second sub MOS tube and the third sub MOS tube are connected in series; and the drains of the third sub MOS tube and the fourth sub MOS tube are connected in series.

Preferably, the model of the battery protection IC is S-8261DAZ-M6T 1U.

The implementation of one of the technical schemes of the utility model has the following advantages or beneficial effects:

according to the utility model, the original lithium battery charging protection circuit can be improved by additionally arranging the second MOS tube group Q2 and arranging the second MOS tube group Q2 to be connected with the first MOS tube group Q1 in series. When the first MOS tube group Q1 fails, the second MOS tube group Q2 can normally protect the product and prevent the battery from being overcharged. When the safety requirement of the charge abuse experiment is met, the function of the battery cell is not influenced during electrification.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:

FIG. 1 is a schematic diagram of a conventional lithium battery charging protection circuit;

fig. 2 is a circuit diagram of the lithium battery charging protection circuit of the present invention.

Detailed Description

In order that the objects, aspects and advantages of the present invention will become more apparent, various exemplary embodiments will be described below with reference to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various exemplary embodiments in which the utility model may be practiced. The same numbers in different drawings identify the same or similar elements unless otherwise indicated. The implementations described in the exemplary embodiments below are not intended to represent all implementations consistent with the present disclosure. It is to be understood that they are merely examples of processes, methods, apparatus, etc. consistent with certain aspects of the present disclosure as detailed in the appended claims, and that other embodiments may be used or structural and functional modifications may be made to the embodiments set forth herein without departing from the scope and spirit of the present disclosure.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," and the like are used in the orientations and positional relationships illustrated in the accompanying drawings for the purpose of facilitating the description of the present invention and simplifying the description, and do not indicate or imply that the elements so referred to must have a particular orientation, be constructed in a particular orientation, and be operated. The terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "plurality" means two or more. The terms "coupled" and "connected" are to be construed broadly and may include, for example, a fixed connection, a removable connection, a unitary connection, a mechanical connection, an electrical connection, a communicative connection, a direct connection, an indirect connection via intermediate media, and may include, but are not limited to, a connection between two elements or an interactive relationship between two elements. The term "and/or" includes any and all combinations of one or more of the associated listed items. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In order to explain the technical solution of the present invention, the following description is made by way of specific examples, which only show the relevant portions of the embodiments of the present invention.

The first embodiment is as follows:

as shown in fig. 2, the present invention provides an improved lithium battery charging protection circuit, which is characterized by comprising a battery protection IC, a first MOS transistor group Q1 and a second MOS transistor group Q2; the first MOS transistor group Q1 and the second MOS transistor group Q2 are connected in series and then connected to a battery protection IC. Specifically, the battery protection IC can protect the lithium battery from overcharge, overdischarge, and overcurrent. The lithium battery charging protection circuit shown in fig. 2 is an improvement of fig. 1, and a second MOS tube group Q2 is added and connected in series with the first MOS tube group Q1. The first MOS transistor group Q1 and the second MOS transistor group Q2 are connected in series to a battery protection IC. In the circuit, the first MOS tube group Q1 and the second MOS tube group Q2 are both conducted, the charging loop can be conducted, and the lithium battery is normally electrified. When one of the first MOS tube group Q1 and the second MOS tube group Q2 is failed and becomes normal, the other MOS tube group can still work normally, and when the lithium battery is overcharged, the rest MOS tube groups are disconnected and cut off a charging loop under the control of a protection chip, and charging is stopped. The improved lithium battery charging protection circuit can still normally protect the battery cell under the condition that a single device fails, and safety accidents such as ignition or explosion of the battery cell and the like are avoided. When the improved circuit meets the safety requirement of the charge abuse experiment, the function of the battery cell is not influenced when the circuit is electrified.

In an alternative embodiment, the first MOS transistor group Q1 and the second MOS transistor group Q2 are 8205A in size; the first MOS tube group Q1 and the second MOS tube group Q2 are common-drain double-N-channel enhancement type field effect tubes. Specifically, 8205A is a typical common-drain double-N-channel enhancement type field-effect transistor, is designed for battery protection, and has the characteristics of rapid switching, ultralow on-resistance and high cost performance. When the charger normally charges the battery, the voltage of the battery cell is higher and higher as the charging time increases. When the voltage of the lithium battery rises to 3.9V to 4.5V, the battery protection IC considers that the battery voltage is in an overcharge voltage state, and immediately turns off the output voltage of the CO pin, so that the voltage of the CO pin becomes 0V, and the fourth pin of the first MOS tube group Q1 and the sixth pin of the second MOS tube group Q2 are turned off due to a low level. At this time, the cathode B-of the battery cell is disconnected from the cathode output P-of the protection circuit. That is, the charging circuit of the lithium battery is cut off, and the lithium battery stops charging. The protection circuit is in an overcharged state and is always in a maintenance state. After the positive and negative electrodes P and P-of the protection circuit are indirectly discharged, the overcharge controls the first MOS tube group Q1 and the second MOS tube group Q2 to be closed, but the positive direction of the diode inside the protection circuit is the same as the direction of the discharge circuit, so the discharge circuit can discharge. The battery protection IC stops the overcharge protection state and outputs a high voltage on the CO pin again, thereby opening the overcharge control tubes in the first and second MOS tube groups Q1 and Q2, i.e., the negative electrode B-of the battery cell is reconnected with the negative electrode output P-of the protection circuit.

As an optional implementation, the first MOS tube group Q1 includes a first sub MOS tube and a second sub MOS tube; the second MOS transistor group Q2 includes a third sub MOS transistor and a fourth sub MOS transistor. Specifically, the first MOS tube group Q1 and the second MOS tube group Q2 each have two sub-MOS tubes built therein. As shown in fig. 2, the first sub-MOS transistor, the second sub-MOS transistor, the third sub-MOS transistor and the fourth sub-MOS transistor are arranged from left to right in sequence.

As an optional implementation, the gates of the first sub-MOS transistor and the third sub-MOS transistor are connected to a DO pin of the battery protection IC; and the grids of the second sub MOS tube and the fourth sub MOS tube are connected with a CO pin of the battery protection IC. Specifically, a DO pin of the protection IC is a discharge control end of the battery, a CO pin of the protection IC is a charge control end of the battery, and the protection IC controls the DO pin and the CO pin to output a high level or a low level by detecting an output voltage of the VM port, so as to control whether the first MOS tube bank Q1 and the second MOS tube bank Q2 are turned on. Only if the first MOS tube group Q1 and the second MOS tube group Q2 are conducted simultaneously, the charging loop can be conducted, and the lithium battery is charged normally.

As an alternative embodiment, the source of the first sub-MOS transistor is connected to the VSS pin of the battery protection IC; and the source electrode of the fourth sub MOS tube is connected with a VM pin of the battery protection IC. Specifically, the VSS pin of the battery protection IC is an input terminal of a negative power supply of a lithium battery, and the VM pin of the battery protection IC is a voltage detection terminal between VM and VSS, and can detect an overcurrent in a circuit.

As an optional implementation manner, the drains of the first sub-MOS transistor and the second sub-MOS transistor are connected in series; the source electrodes of the second sub MOS tube and the third sub MOS tube are connected in series; the drains of the third sub-MOS tube and the fourth sub-MOS tube are connected in series. Specifically, the first MOS tube group Q1 and the second MOS tube group Q2 are connected in series, the first MOS tube group Q1 and the second MOS tube group Q2 are all common-drain dual N-channel enhancement type field effect transistors, the drains of two sub-MOS transistors included in the two MOS tube groups are connected in series, and the sources of two sub-MOS transistors adjacent to the two MOS tube groups in series are connected in series.

As an alternative embodiment, the battery protection IC is model S-8261DAZ-M6T 1U. Specifically, the S-8261 series incorporates a high-precision voltage detection circuit and a delay circuit, which are protection ICs for lithium ion/lithium polymer rechargeable batteries. The S-8261 series IC is most suitable for overcharge, overdischarge, and overcurrent protection of 1-cell lithium ion/lithium polymer rechargeable battery. The model number of the battery protection IC used in the present embodiment is S-8261DAZ-M6T1U, which is a preferable scheme in the present embodiment.

As an alternative embodiment, the improved lithium battery charging protection circuit further comprises a TH element. Specifically, the TH element can detect the temperature of the circuit and protect the circuit.

As an alternative embodiment, the TH element comprises two NTC thermistors. Specifically, the NTC is a negative temperature coefficient resistor, and mainly plays a role of overheat protection in a circuit, that is, when the temperature of the lithium battery itself or the surrounding environment rises, the resistance value of the NTC element decreases, an electric device or a charging device timely responds, and if the temperature exceeds a certain value, the system enters a protection state and stops charging and discharging.

As an alternative embodiment, the NTC thermistor has a parameter of 10k 1% B3435 k 1%. Specifically, the B value is the thermal constant of the ntc thermistor, i.e., the chip (a semiconductor ceramic) of the thermistor is sintered at high temperature to form a material with a certain resistivity, and there is only one B value for each formulation and sintering temperature. The B value can be calculated by measuring the resistance values at 25 degrees celsius and 50 degrees celsius (or 85 degrees celsius). The value B is positively correlated with the temperature coefficient of resistance of the product, namely the larger the value B is, the larger the temperature coefficient of resistance is. The NTC thermistor used in the embodiment has a zero power resistance value of between 9.9K and 10.1K and a B value of between 3400.65K and 3469.35K under the conditions of 25 ℃ and almost zero test power.

The embodiment is only a specific example and does not indicate such an implementation of the utility model.

While the utility model has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the utility model. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the utility model without departing from the essential scope thereof. Therefore, it is intended that the utility model not be limited to the particular embodiment disclosed, but that the utility model will include all embodiments falling within the scope of the appended claims.

Claims

1. An improved lithium battery charging protection circuit is characterized by comprising a battery protection IC, a first MOS tube group Q1 and a second MOS tube group Q2; the first MOS tube bank Q1 is connected with the second MOS tube bank Q2 in series and then is connected with the battery protection IC; the models of the first MOS tube group Q1 and the second MOS tube group Q2 are 8205A; the first MOS tube group Q1 and the second MOS tube group Q2 are common-drain double-N-channel enhancement type field effect tubes; the first MOS tube group Q1 comprises a first sub MOS tube and a second sub MOS tube; the second MOS tube group Q2 comprises a third sub MOS tube and a fourth sub MOS tube; the improved lithium battery charging protection circuit also comprises a TH element; the TH element includes two NTC thermistors.

2. The improved lithium battery charging protection circuit as claimed in claim 1, wherein the gates of the first and third sub-MOS transistors are connected to a DO pin of the battery protection IC; and the grids of the second sub MOS tube and the fourth sub MOS tube are connected with a CO pin of the battery protection IC.

3. The improved lithium battery charging protection circuit as claimed in claim 2, wherein the source of the first sub-MOS transistor is connected to the VSS pin of the battery protection IC; and the source electrode of the fourth sub MOS tube is connected with the VM pin of the battery protection IC.

4. The improved lithium battery charging protection circuit as claimed in claim 2, wherein the drains of the first sub-MOS transistor and the second sub-MOS transistor are connected in series; the source electrodes of the second sub MOS tube and the third sub MOS tube are connected in series; and the drains of the third sub MOS tube and the fourth sub MOS tube are connected in series.

5. The improved lithium battery charging protection circuit as claimed in claim 1, wherein the model number of said battery protection IC is S-8261DAZ-M6T 1U.