CN220492683U - BMS overcharge and overdischarge protection circuit - Google Patents

Abstract

The application provides a BMS overcharge and overdischarge protection circuit; the BMS overcharge and overdischarge protection circuit comprises a first voltage division circuit and a second voltage division circuit which are connected with the battery pack, a NOT gate circuit which is connected with the second voltage division circuit, and a switch circuit which is respectively connected with the first voltage division circuit and the NOT gate circuit; the first voltage dividing circuit outputs a first cut-off signal according to the charging state of the battery pack, and the second voltage dividing circuit outputs a conduction signal according to the discharging state of the battery pack; the NOT circuit completes conduction according to the conduction signal and outputs a second cut-off signal; the switching circuit is turned off according to the first cut-off signal or the second cut-off signal. The battery protection device can protect the battery from being damaged by overcharge or overdischarge, realizes accurate protection control of the battery, and improves the reliability and safety of a battery system.

Description

BMS overcharge and overdischarge protection circuit

Technical Field

The application relates to the technical field of battery systems, in particular to a BMS overcharge and overdischarge protection circuit.

Background

The BMS (Battery Management System ) is a key component in the battery system, and is responsible for monitoring and controlling parameters of the state, temperature, voltage, current, etc. of the battery, and ensuring the safety and optimal performance of the battery.

The overcharge of the battery can lead to volatilization of electrolyte, overhigh temperature of the battery and oxidation of internal materials, and the risks of battery expansion, leakage, explosion and the like can be caused when the battery is severe; over-discharge of the battery can result in an excessively low battery voltage, thereby reducing the performance and life of the battery and even damaging the battery.

In order to avoid the overcharge and overdischarge of the battery, the traditional scheme is to construct a sampling circuit, a signal conditioning circuit and a control circuit by using a CPU main control chip, realize the logic protection of the battery by software programming, and establish communication connection with the outside through various communication buses (such as CAN, RS485, RS232 and the like) to realize the interaction and transmission of information. However, this solution also has serious safety hidden trouble, because software bug or external electromagnetic interference of designer may cause software failure or program crash, and further cause out of control in charging and discharging process, resulting in damage caused by overcharging or overdischarging of battery.

Disclosure of Invention

The application provides a BMS overcharge and overdischarge protection circuit capable of avoiding battery overcharge or overdischarge for solving the technical problem.

Specifically, the application provides a BMS overcharge and overdischarge protection circuit, includes at least:

the first voltage dividing circuit outputs a first cut-off signal according to the charging state of the battery pack, and the second voltage dividing circuit outputs a turn-on signal according to the discharging state of the battery pack.

And the NOT gate circuit is connected with the second voltage division circuit, completes conduction according to the conduction signal and outputs a second cut-off signal.

And the switching circuit is respectively connected with the first voltage division circuit and the NOT circuit, and the switching circuit is switched off according to the first cut-off signal or the second cut-off signal.

In the above technical solution, the voltage of the battery pack is sampled and appropriately divided by the first voltage dividing circuit to accurately determine whether the battery pack reaches the charge cut-off state, and the voltage of the battery pack is sampled and appropriately divided by the second voltage dividing circuit to accurately determine whether the battery pack reaches the discharge cut-off state; when the battery pack reaches a discharge cut-off state, the NOT gate circuit is conducted and judges that the current battery pack needs to be cut off in discharge; and then the switch circuit completes the cut-off operation according to the signals output by the first voltage dividing circuit and the NOT gate circuit, so as to control the cut-off of the charging or discharging of the battery, protect the battery from being damaged by overcharging or overdischarging, realize the accurate protection control of the battery, and improve the reliability and the safety of a battery system.

The BMS overcharge and overdischarge protection circuit further comprises a load end; the positive electrode of the load end is connected with a switch circuit; and the negative electrode of the load end is connected with the negative electrode of the battery pack, and is grounded after being converged with the negative electrode.

In the technical scheme, the positive electrode of the load end is connected with the switch circuit, so that the current of the load end can be controlled and cut off, and the battery can be protected from being damaged by overcharge or overdischarge; the negative electrode of the load end is connected with the negative electrode of the battery pack and is grounded after being converged with the negative electrode, so that the grounding and the safety of the battery system can be ensured, the voltage suspension and the electromagnetic interference in the battery system can be reduced, and the stability and the safety of the whole system can be improved.

The first voltage dividing circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first zener diode and a first triode.

In the first voltage dividing circuit, the first resistor is connected with the second resistor; one end of the first zener diode is connected to any point of the wiring of the first resistor and the second resistor, and the other end of the first zener diode is connected to the third resistor; the other end of the third resistor is connected to the B pole of the first triode, the E pole of the first triode is grounded, the C pole of the first triode is connected with one end of the fourth resistor, and the other end of the fourth resistor is connected with the positive pole of the battery pack.

In the technical scheme, the first voltage dividing circuit has the advantages of simple component structure, easy realization and maintenance, lower power consumption and higher reliability; by selecting a proper resistance value, the first voltage dividing circuit can accurately divide the input voltage according to a preset proportion so as to realize accurate measurement and judgment of the voltage of the battery pack and provide accurate reference for subsequent protection control; the voltage stabilizing diode can provide stable reference voltage so as to ensure the stability and reliability of the voltage division output voltage, and the first triode can also realize quick response and accurate detection on voltage change; furthermore, the connection of the fourth resistor to the first transistor can protect the first transistor to a certain extent from excessive currents or overvoltages.

The second voltage dividing circuit comprises a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second zener diode and a second triode.

In the second voltage dividing circuit, the fifth resistor is connected with the sixth resistor, one end of the second zener diode is connected to any point of wiring of the fifth resistor and the sixth resistor, and the other end of the second zener diode is connected to the seventh resistor; the other end of the seventh resistor is connected to the B pole of the second triode, the E pole of the second triode is grounded, the C pole of the second triode is connected with one end of the eighth resistor, and the other end of the eighth resistor is connected with the positive pole of the battery pack.

In the technical scheme, the accurate voltage division of the input voltage can be realized by adjusting the proportion of the fifth resistor to the sixth resistor, and an accurate voltage signal is provided; the second zener diode can provide stable reference voltage, so as to provide accurate reference for subsequent protection control; the third triode can rapidly respond to and detect voltage changes; in addition, the eighth resistor is connected with the second triode, so that the second triode can be protected from over-current or over-voltage.

The NOT circuit comprises a ninth resistor, a tenth resistor, an eleventh resistor and a third triode.

In the NOT circuit, the ninth resistor is connected to the C electrode of the second triode; one end of the tenth resistor is connected to any point of the wiring between the ninth resistor and the B pole of the third triode, and the other end of the tenth resistor is connected with the E pole of the third triode and then grounded; one end of the eleventh resistor is connected to the positive electrode of the battery pack, and the other end of the eleventh resistor is connected with the C electrode of the third triode.

In the technical scheme, the inverter circuit has lower power consumption, is beneficial to saving energy and prolonging the service life of the battery, can provide faster response speed, and timely outputs a cut-off signal so as to protect the battery from damage.

The switching circuit comprises a first switching sub-circuit, a second switching sub-circuit, a third switching sub-circuit and a fourth switching sub-circuit; the first switch sub-circuit comprises a twelfth resistor, a thirteenth resistor and a first MOS tube; the second switch sub-circuit comprises a fourteenth resistor, a fifteenth resistor and a second MOS tube; the third switch sub-circuit comprises a sixteenth resistor, a seventeenth resistor and a second MOS tube; the fourth switching sub-circuit comprises an eighteenth resistor, a nineteenth resistor and a second MOS tube.

In the first switch sub-circuit, one end of the twelfth resistor is connected with the C electrode of the first triode and the G electrode of the first MOS tube respectively, the other end of the twelfth resistor is connected with the thirteenth resistor after being converged with the S electrode of the first MOS tube, and the other end of the thirteenth resistor is grounded.

In the second switch sub-circuit, one end of the fourteenth resistor is connected with the S pole of the second MOS tube and the positive pole of the load end respectively, the other end of the fourteenth resistor is connected with the G pole of the second MOS tube and then connected with the fifteenth resistor, and the other end of the fifteenth resistor is connected with the D pole of the first MOS tube.

In the third sub-switch circuit, one end of the sixteenth resistor is connected with the C electrode of the third triode and the G electrode of the third MOS tube respectively, the other end of the sixteenth resistor is connected with the seventeenth resistor after being converged with the S electrode of the third MOS tube, and the other end of the seventeenth resistor is grounded.

In the fourth switching sub-circuit, one end of the eighteenth resistor is connected with the S pole of the fourth MOS tube and the positive pole of the battery pack respectively, the other end of the eighteenth resistor is connected with the nineteenth resistor after being converged with the G pole of the fourth MOS tube, the other end of the nineteenth resistor is connected with the D pole of the third MOS tube, and the D pole of the fourth MOS tube is connected with the D pole of the second MOS tube.

In the technical scheme, through flexibly controlling each switch sub-circuit in the switch circuit, the battery can be ensured to work in a proper charge and discharge range, the normal operation of the battery pack and the load end is ensured, and the stability and the reliability of the whole system are improved; and when the battery pack is overcharged or overdischarged, the switch circuit can cut off current in time, so that the condition that the battery pack is overhigh in voltage due to continuous charging or overlow in voltage due to continuous discharging is avoided, and further the damage to the service life of the battery is reduced.

Compared with the prior art, the beneficial effect of this application lies in:

the application is provided with a first voltage dividing circuit, a second voltage dividing circuit, a NOT circuit and a switch circuit; the NOT gate receives a signal output by the first voltage division circuit according to the charging state of the battery pack to output a corresponding cut-off signal, and the second voltage division circuit outputs the corresponding cut-off signal according to the discharging state of the battery pack, so that the switch circuit finishes cut-off work according to the received cut-off signal. The battery protection device can protect the battery from being damaged by overcharge or overdischarge, realizes accurate protection control of the battery, and improves the reliability and safety of a battery system. The method and the device solve the technical problems that in the prior art, logic protection of the battery is realized through software programming, serious potential safety hazards exist, and further the charging and discharging processes are caused to run away, so that the battery is overcharged or overdischarged to be damaged.

Drawings

Fig. 1 is a schematic diagram of a BMS overcharge and overdischarge protection circuit described in the present application.

Fig. 2 is a schematic diagram of a partition of the BMS overcharge and overdischarge protection circuit described in the present application.

Detailed Description

The application provides a BMS overcharge and overdischarge protection circuit to realize the logic protection to the battery through software programming among the solution prior art, there is serious potential safety hazard that leads to, and then causes the charge and discharge process to run away, causes the overcharge of battery or overdischarge and the technical problem who damages.

A BMS overcharge and overdischarge protection circuit of the present application will be described in further detail with reference to specific embodiments and drawings.

Referring to fig. 1 and 2, the present application provides a BMS overcharge and overdischarge protection circuit, at least including:

the battery pack comprises a first voltage division circuit 1 and a second voltage division circuit 2 which are connected with the battery pack, wherein the first voltage division circuit 1 outputs a first cut-off signal according to the charging state of the battery pack, and the second voltage division circuit 2 outputs a turn-on signal according to the discharging state of the battery pack.

And the NOT circuit 3 is connected with the second voltage dividing circuit 2, and the NOT circuit 3 is switched on according to the on signal and outputs a second off signal.

And a switching circuit 4 connected to the first voltage dividing circuit 1 and the not gate circuit 3, respectively, wherein the switching circuit 4 is turned off according to the first turn-off signal or the second turn-off signal.

It should be noted that, the voltage of the battery pack is sampled and appropriately divided by the first voltage dividing circuit 1 to accurately determine whether the battery pack reaches the charge cut-off state, and the voltage of the battery pack is sampled and appropriately divided by the second voltage dividing circuit 2 to accurately determine whether the battery pack reaches the discharge cut-off state; when the battery pack reaches a discharge cut-off state, the NOT gate 3 is switched on and judges that the current battery pack needs to be cut off in discharge; then, the switch circuit 4 completes the cut-off operation according to the signals output by the first voltage division circuit 1 and the NOT gate circuit 3, so as to control the cut-off of the charging or discharging of the battery, protect the battery from being damaged by overcharging or overdischarging, realize the accurate protection control of the battery, and improve the reliability and the safety of a battery system.

Further, the BMS overcharge and overdischarge protection circuit further comprises a load end; the positive pole P+ of the load end is connected with the switch circuit 4; the negative electrode P-of the load end is connected with the negative electrode B-of the battery pack, and is grounded after being converged with the negative electrode.

It should be noted that, by connecting the positive electrode p+ of the load end with the switch circuit 4, the current of the load end can be controlled and cut off, which is helpful for protecting the battery from the damage of overcharge or overdischarge; the negative electrode P-of the load end is connected with the negative electrode B-of the battery pack and is grounded after being converged with the negative electrode, so that the grounding and the safety of the battery system can be ensured, the voltage suspension and the electromagnetic interference in the battery system can be reduced, and the stability and the safety of the whole system can be improved.

Further, the first voltage dividing circuit 1 includes a first resistor R6, a second resistor R9, a third resistor R7, a fourth resistor R5, a first zener diode D1, and a first triode Q4.

Further, in the first voltage dividing circuit 1, the first resistor R6 and the second resistor R9 are connected; one end of the first zener diode D1 is connected to any point of the wiring of the first resistor R6 and the second resistor R9, and the other end of the first zener diode D is connected to the third resistor R7; the other end of the third resistor R7 is connected to the B pole of the first triode Q4, the E pole of the first triode Q4 is grounded, the C pole of the first triode Q4 is connected with one end of the fourth resistor R5, and the other end of the fourth resistor R5 is connected with the positive pole B+ of the battery pack.

It should be noted that, the component structure of the first voltage dividing circuit 1 is simple, easy to implement and maintain, low in power consumption and high in reliability; by selecting a proper resistance value, the first voltage dividing circuit 1 can accurately divide the input voltage according to a preset proportion so as to realize accurate measurement and judgment of the voltage of the battery pack and provide accurate reference for subsequent protection control; the voltage stabilizing diode can provide stable reference voltage so as to ensure the stability and reliability of the divided output voltage, and the first triode Q4 can also realize quick response and accurate detection on voltage change; furthermore, the connection of the fourth resistor R5 to the first transistor Q4 can protect the first transistor Q4 to a certain extent from excessive currents or overvoltages.

Further, the second voltage dividing circuit 2 includes a fifth resistor R13, a sixth resistor R19, a seventh resistor R16, an eighth resistor R12, a second zener diode D2, and a second triode Q7.

Further, in the second voltage dividing circuit 2, the fifth resistor R13 and the sixth resistor R19 are connected, one end of the second zener diode D2 is connected to any point of the connection of the fifth resistor R13 and the sixth resistor R19, and the other end is connected to the seventh resistor R16; the other end of the seventh resistor R16 is connected to the B pole of the second triode Q7, the E pole of the second triode Q7 is grounded, the C pole of the second triode Q7 is connected with one end of the eighth resistor R12, and the other end of the eighth resistor R12 is connected with the positive pole B+ of the battery pack.

It should be noted that, by adjusting the ratio of the fifth resistor R13 to the sixth resistor R19, accurate voltage division of the input voltage can be achieved, and accurate voltage signals can be provided; the second zener diode D2 can provide a stable reference voltage, so as to provide an accurate reference for subsequent protection control; the third transistor Q6 can rapidly respond to and detect a voltage change; in addition, the eighth resistor R12 is connected to the second transistor Q7, so that the second transistor Q7 can be protected from overcurrent or overvoltage.

Further, the not gate circuit 3 includes a ninth resistor R14, a tenth resistor R17, an eleventh resistor R11, and a third transistor Q6.

Further, in the not gate 3, the ninth resistor R14 is connected to the C pole of the second transistor Q7; one end of the tenth resistor R17 is connected to any point of the wiring between the ninth resistor R14 and the B pole of the third triode Q6, and the other end of the tenth resistor R17 is connected with the E pole of the third triode Q6 and then grounded; one end of the eleventh resistor R11 is connected to the positive pole B+ of the battery pack, and the other end of the eleventh resistor R11 is connected with the C pole of the third triode Q6.

It should be noted that, the inverter circuit 3 has low power consumption, which is beneficial to saving energy and prolonging the service life of the battery, and can provide a faster response speed, timely output a cut-off signal, and further protect the battery from damage.

Further, the switch circuit 4 comprises a first switch sub-circuit, a second switch sub-circuit, a third switch sub-circuit and a fourth switch sub-circuit; the first switch sub-circuit comprises a twelfth resistor R18, a thirteenth resistor R10 and a first MOS tube Q3; the second switch sub-circuit comprises a fourteenth resistor R2, a fifteenth resistor R4 and a second MOS tube Q2; the third switch sub-circuit comprises a sixteenth resistor R15, a seventeenth resistor R18 and a second MOS tube Q2; the fourth switching sub-circuit comprises an eighteenth resistor R1, a nineteenth resistor R3 and a second MOS tube Q2.

Further, in the first switching sub-circuit, one end of the twelfth resistor R18 is connected to the C pole of the first triode Q4 and the G pole of the first MOS transistor Q3, the other end of the twelfth resistor R is connected to the thirteenth resistor R10 after being converged with the S pole of the first MOS transistor Q3, and the other end of the thirteenth resistor R10 is grounded.

In the second switch sub-circuit, one end of the fourteenth resistor R2 is connected with the S pole of the second MOS transistor Q2 and the positive pole p+ of the load end, the other end of the fourteenth resistor R2 is connected with the G pole of the second MOS transistor Q2, and then connected with the fifteenth resistor R4, and the other end of the fifteenth resistor R4 is connected with the D pole of the first MOS transistor Q3.

In the third sub-switch circuit 4, one end of the sixteenth resistor R15 is connected to the C pole of the third triode Q6 and the G pole of the third MOS transistor Q5, the other end of the sixteenth resistor R15 is connected to the seventeenth resistor R18 after being converged with the S pole of the third MOS transistor Q5, and the other end of the seventeenth resistor R18 is grounded.

In the fourth switching sub-circuit, one end of the eighteenth resistor R1 is connected with the S pole of the fourth MOS transistor Q1 and the positive pole b+ of the battery pack, the other end of the eighteenth resistor R1 is connected with the G pole of the fourth MOS transistor Q1, and then connected with the nineteenth resistor R3, the other end of the nineteenth resistor R3 is connected with the D pole of the third MOS transistor Q5, and the D pole of the fourth MOS transistor Q1 is connected with the D pole of the second MOS transistor Q2.

It should be noted that, by flexibly controlling each switch sub-circuit in the switch circuit 4, the battery can be ensured to work in a proper charge and discharge range, the normal operation of the battery pack and the load end is ensured, and the stability and reliability of the whole system are improved; and when the battery pack is overcharged or overdischarged, the switch circuit 4 can cut off current in time, so that the condition that the battery pack is excessively high in voltage due to continuous charging or excessively low in voltage due to continuous discharging is avoided, and the damage to the service life of the battery is further reduced.

In a possible implementation manner, when the voltage of the battery pack is higher than the first preset threshold value due to overcharge of the battery pack, after the voltage of the battery pack is divided by the first resistor R6 and the second resistor R9, the divided value is 0.7V greater than the cut-off voltage of the first zener diode D1, and the first triode Q4 is turned on; at this time, the gate voltage of the first MOS transistor Q3 becomes low, the first MOS transistor Q3 is turned off, the gate and source voltages of the second MOS transistor Q2 are almost equal, the second MOS transistor Q2 is also turned off, and at this time, the positive electrode p+ and the negative electrode at the load end cannot charge the battery pack; and further, the function that the battery cannot be charged continuously when overcharged is realized.

When the voltage of the battery pack is lower than a second preset threshold value due to overdischarge of the battery pack, after the voltage of the battery pack is divided by a fifth resistor R13 and a sixth resistor R19, the divided voltage value is smaller than the cut-off voltage of the second voltage stabilizing tube, the second triode Q7 cannot be conducted, at the moment, the lower part of the eighth resistor R12 is in a high level, a third triode Q6 in the NOT gate 3 is conducted, the voltage at the grid electrode of a third MOS tube Q5 is lowered, the third MOS tube Q5 is cut off, and the fourth MOS tube Q1 is also cut off; at this time, the battery pack cannot be discharged to the outside; and further, the function that the discharge can not be continued when the battery is overdischarged is realized.

The first preset threshold and the second preset threshold are not limited herein, and can be set by a person skilled in the art according to actual application requirements.

If the battery voltage conversion circuit is used for simple battery overcharge and overdischarge protection, compared with the method that a switch power supply module is used for converting the battery voltage into 5V/3.3V to supply power for a circuit, great cost is saved.

If the circuit is used for secondary protection, the circuit can work even when the battery system is shut down, and the switching power supply module for converting the battery voltage into 5V/3.3V to supply power to the circuit can be completely disconnected to save power consumption.

In summary, the present application provides a BMS overcharge and overdischarge protection circuit; the BMS overcharge and overdischarge protection circuit is provided with a first voltage division circuit 1, a second voltage division circuit 2, a NOT gate circuit 3 and a switch circuit 4; the NOT gate receives a signal output by the first voltage dividing circuit 1 according to the charging state of the battery pack to output a corresponding cut-off signal, and the second voltage dividing circuit 2 outputs a corresponding cut-off signal according to the discharging state of the battery pack, so that the switch circuit 4 finishes cut-off work according to the received cut-off signal. The battery protection device can protect the battery from being damaged by overcharge or overdischarge, realizes accurate protection control of the battery, and improves the reliability and safety of a battery system.

Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the above illustrative embodiments are merely exemplary and are not intended to limit the scope of the present application thereto. Various changes and modifications may be made therein by one of ordinary skill in the art without departing from the scope and spirit of the present application. All such changes and modifications are intended to be included within the scope of the present application as set forth in the appended claims.

It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

While the present application has been described in conjunction with the specific embodiments above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, all such alternatives, modifications, and variations are included within the spirit and scope of the following claims.

Claims (10)

1. A BMS overcharge and overdischarge protection circuit, comprising at least:

the first voltage dividing circuit outputs a first cut-off signal according to the charging state of the battery pack, and the second voltage dividing circuit outputs a conduction signal according to the discharging state of the battery pack;

the NOT gate circuit is connected with the second voltage dividing circuit, completes conduction according to the conduction signal and outputs a second cut-off signal;

and the switching circuit is respectively connected with the first voltage division circuit and the NOT circuit, and the switching circuit is switched off according to the first cut-off signal or the second cut-off signal.

2. The BMS overcharge and overdischarge protection circuit of claim 1, further comprising a load terminal;

the positive electrode of the load end is connected with a switch circuit;

and the negative electrode of the load end is connected with the negative electrode of the battery pack, and is grounded after being converged with the negative electrode.

3. The BMS overcharge and overdischarge protection circuit of claim 2, wherein the first voltage dividing circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first zener diode, and a first transistor.

4. The BMS overcharge and overdischarge protection circuit of claim 3, wherein in the first voltage dividing circuit, the first resistor and the second resistor are connected;

one end of the first zener diode is connected to any point of the wiring of the first resistor and the second resistor, and the other end of the first zener diode is connected to the third resistor;

the other end of the third resistor is connected to the B pole of the first triode, the E pole of the first triode is grounded, the C pole of the first triode is connected with one end of the fourth resistor, and the other end of the fourth resistor is connected with the positive pole of the battery pack.

5. The BMS overcharge and overdischarge protection circuit of claim 4, wherein the second voltage dividing circuit comprises a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a second zener diode, and a second transistor.

6. The BMS overcharge and overdischarge protection circuit according to claim 5, wherein in the second voltage dividing circuit, the fifth resistor and the sixth resistor are connected, and one end of the second zener diode is connected to any point of the fifth resistor and the sixth resistor, and the other end is connected to the seventh resistor;

the other end of the seventh resistor is connected to the B pole of the second triode, the E pole of the second triode is grounded, the C pole of the second triode is connected with one end of the eighth resistor, and the other end of the eighth resistor is connected with the positive pole of the battery pack.

7. The BMS overcharge and overdischarge protection circuit of claim 6, wherein the not gate circuit comprises a ninth resistor, a tenth resistor, an eleventh resistor, and a third transistor.

8. The BMS overcharge and overdischarge protection circuit of claim 7, wherein in the not gate circuit, the ninth resistor is connected to a C pole of a second transistor;

one end of the tenth resistor is connected to any point of the wiring between the ninth resistor and the B pole of the third triode, and the other end of the tenth resistor is connected with the E pole of the third triode and then grounded;

one end of the eleventh resistor is connected to the positive electrode of the battery pack, and the other end of the eleventh resistor is connected with the C electrode of the third triode.

9. The BMS overcharge and overdischarge protection circuit of claim 8, wherein the switching circuit comprises first and second, third, and fourth switching sub-circuits;

the first switch sub-circuit comprises a twelfth resistor, a thirteenth resistor and a first MOS tube;

the second switch sub-circuit comprises a fourteenth resistor, a fifteenth resistor and a second MOS tube;

the third switch sub-circuit comprises a sixteenth resistor, a seventeenth resistor and a second MOS tube;

the fourth switching sub-circuit comprises an eighteenth resistor, a nineteenth resistor and a second MOS tube.

10. The BMS overcharge and overdischarge protection circuit of claim 9, wherein in the first switching sub-circuit, one end of the twelfth resistor is connected to the C pole of the first triode and the G pole of the first MOS tube, and the other end of the twelfth resistor is connected to the thirteenth resistor after being converged with the S pole of the first MOS tube, and the other end of the thirteenth resistor is grounded;

in the second switch sub-circuit, one end of the fourteenth resistor is connected with the S pole of the second MOS tube and the positive pole of the load end respectively, the other end of the fourteenth resistor is connected with the G pole of the second MOS tube and then connected with the fifteenth resistor, and the other end of the fifteenth resistor is connected with the D pole of the first MOS tube;

in the third switch sub-circuit, one end of the sixteenth resistor is respectively connected with the C electrode of the third triode and the G electrode of the third MOS tube, the other end of the sixteenth resistor is connected with the seventeenth resistor after being converged with the S electrode of the third MOS tube, and the other end of the seventeenth resistor is grounded;

in the fourth switching sub-circuit, one end of the eighteenth resistor is connected with the S pole of the fourth MOS tube and the positive pole of the battery pack respectively, the other end of the eighteenth resistor is connected with the nineteenth resistor after being converged with the G pole of the fourth MOS tube, the other end of the nineteenth resistor is connected with the D pole of the third MOS tube, and the D pole of the fourth MOS tube is connected with the D pole of the second MOS tube.