CN113690956A

CN113690956A - Switch circuit, battery management system and battery pack

Info

Publication number: CN113690956A
Application number: CN202110778686.7A
Authority: CN
Inventors: 杜晓佳; 黄思林; 李昊旸
Original assignee: Dongguan Poweramp Technology Ltd
Current assignee: Dongguan Poweramp Technology Ltd
Priority date: 2021-07-09
Filing date: 2021-07-09
Publication date: 2021-11-23

Abstract

The embodiment of the application relates to the technical field of batteries and discloses a switching circuit, a battery management system and a battery pack, wherein the switching circuit comprises a switching tube and a fuse which are connected in series, the first end of the switching circuit is used for being connected with the positive pole of a battery pack, the second end of the switching circuit is used for being connected with the negative pole of the battery pack, the fuse is used for connecting the battery pack and external equipment (a load or a charger), and a controller controls the switching tube to be connected and disconnected. When an abnormality (overcurrent, overvoltage, overtemperature or the like) occurs, the switching tube is conducted, so that the fuse protector is fused due to short circuit, and further the connection between the battery pack and external equipment is disconnected, and the battery pack is prevented from being exploded due to the factors such as overcurrent, overvoltage or overtemperature. And secondly, the switch tube is not arranged in a charge-discharge loop formed by the battery pack and external equipment, is not interfered by current or voltage in the charge-discharge loop, is only driven by the controller, and has high control accuracy. In addition, the switch tube has a simple structure, and bidirectional conduction can be realized without a complex connection structure.

Description

Switch circuit, battery management system and battery pack

Technical Field

The embodiment of the application relates to the technical field of batteries, in particular to a switch circuit, a battery management system and a battery pack.

Background

The BATTERY management system (BATTERY MANAGEMENT SYSTEM, BMS) is a protection and management unit designed specifically for BATTERY packs. The battery pack comprises a battery pack and a battery management system, the battery management system carries out charge and discharge management on the battery pack, intelligent balance is carried out on the electric quantity of each single battery in the charging process, the situations of overcharge and overdischarge of the single battery are prevented, the service life of the battery pack is greatly prolonged, and the battery pack is prevented from being damaged due to overcharge or overdischarge. Meanwhile, the battery management system further comprises a switch circuit, wherein the switch circuit is connected with the battery pack and an external device (a load or a charger), and when the battery pack has overcurrent, overcharge voltage or high temperature, the switch circuit is controlled to be disconnected, so that the battery pack is disconnected with the external device.

Disclosure of Invention

In the process of implementing the embodiment of the present application, the inventors of the present application find that: at present, a switch circuit in a battery management system is equivalently connected with external equipment in series, and the switch circuit cannot be normally disconnected due to the fact that current and time cannot meet disconnection conditions, so that the risk of failure of protection of a battery pack and the external equipment occurs, and after continuous overcurrent, overcharge voltage and overtemperature, the battery pack can be exploded.

In the process of implementing the embodiments of the present application, the inventors of the present application further find that: the related switch tube has a large threshold voltage, the general threshold voltage is 5V-12V, the level signal of a common controller is smaller than the threshold voltage, and the level signal of the general controller is 3.3V, so that an additional level conversion circuit is needed between the controller and the switch tube to control the switch tube to be switched on and off through the controller.

The technical problem that this application embodiment mainly solved provides a switch circuit, battery management system and battery package, and this switch circuit can in time, accurate control group battery and external equipment's electricity be connected, improves battery management system's reliability to, make the battery package have good explosion-proof function and security.

In order to solve the above technical problem, in a first aspect, an embodiment of the present application provides a switching circuit, including: the switch circuit comprises a switch tube and a fuse which are connected in series, wherein a first end of the switch circuit is used for being connected with the positive pole of a battery pack, and a second end of the switch circuit is used for being connected with the negative pole of the battery pack; the fuse is used for connecting the battery pack and external equipment; the switch tube is connected with a controller, and the switch tube is configured to control the switch tube to be switched on and off through the controller. The switch tube comprises two transistors, and each transistor comprises: the semiconductor device comprises a semiconductor substrate, a source electrode, a drain electrode, an insulating layer and a grid electrode, wherein the source electrode and the drain electrode are arranged on the semiconductor substrate at intervals and are respectively connected with the semiconductor substrate; the insulating layer is arranged on the semiconductor substrate and is positioned between the source electrode and the drain electrode; the grid electrode is arranged on the insulating layer and is respectively insulated from the source electrode and the drain electrode; wherein the drains of the two transistors are electrically connected, and the gates of the two transistors are electrically connected.

In some embodiments, the material of the semiconductor substrate comprises silicon carbide.

In some embodiments, the dielectric constant of the material of the insulating layer is 6-9.

In some embodiments, the material of the insulating layer comprises silicon nitride.

In some embodiments, an N-type impurity is added to a channel region, and the channel region is located on the surface layer of the semiconductor substrate close to the insulating layer and located within the projection of the gate relative to the semiconductor substrate.

In some embodiments, the N-type impurities include arsenic and/or phosphorous.

In some embodiments, connection points of the sources of the two transistors and the gates of the two transistors are respectively soldered on a circuit board on which the switching circuit is located.

In some embodiments, the surface of the switch tube away from the circuit board is provided with an insulating glue.

In order to solve the above technical problem, in a second aspect, an embodiment of the present application provides a battery management system, including the switch circuit as described in the first aspect.

In order to solve the above technical problem, in a third aspect, an embodiment of the present application provides a battery pack, including a battery pack and the battery management system as described in the second aspect, where the battery pack supplies power to the battery management system.

Benefits of one or more embodiments of the present application include: in contrast to the prior art, one or more embodiments of the present application provide a switching circuit, which includes a switching tube and a fuse connected in series, where a first end of the switching circuit is used to connect to a positive electrode of a battery pack, a second end of the switching circuit is used to connect to a negative electrode of the battery pack, and the fuse is used to connect the battery pack to an external device (a load or a charger), and since the switching tube is connected to a controller, the switching tube can be controlled to be turned on and off by the controller. Under the normal condition, the switch tube disconnection, group battery and external equipment normal connection, when taking place unusually (overcurrent, overvoltage or excess temperature etc.), switch on through the switch tube, can make the fuse short circuit take place the fusing, and then the connection of disconnection group battery and external equipment for the group battery can not take place to explode because of factors such as overcurrent, overvoltage or excess temperature. And secondly, the switch tube is not arranged in a charge-discharge loop formed by the battery pack and the external equipment, is not interfered by current or voltage in the charge-discharge loop, is only driven by the controller, and can timely and accurately control the electric connection between the battery pack and the external equipment.

In addition, the switch tube comprises two transistors, wherein any transistor comprises a semiconductor substrate, a source electrode, a drain electrode, an insulating layer and a grid electrode, the source electrode and the drain electrode are arranged on the semiconductor substrate at intervals and are respectively and electrically connected with the semiconductor substrate, the insulating layer is arranged on the semiconductor substrate and is respectively insulated from the source electrode and the drain electrode, the grid electrode is arranged on the insulating layer and is respectively insulated from the source electrode and the drain electrode, the drain electrodes of the two transistors are electrically connected, and the grid electrodes of the two transistors are electrically connected, so that the two transistors can be conducted under the driving of grid voltage no matter which of the two source electrodes is at a high level, namely the switch can be conducted in two directions. Therefore, no matter the battery pack is in the charging process or the discharging process, when overcurrent and over-charging voltage occur or the temperature is too high, the driving voltage can be applied to the grid electrode through the controller to control the two transistors to be conducted, so that the switching circuit is connected, namely the fuse is short-circuited, the fuse is rapidly fused, and the battery pack cannot be exploded due to overcurrent, overvoltage or over-temperature. And, the switch tube simple structure need not complicated connection structure and can realize two-way electrically conductive.

Drawings

One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.

Fig. 1 is a schematic diagram illustrating a conventional connection of a switching circuit applied to a battery management system;

fig. 2 is a schematic connection diagram of a switch circuit applied in a battery management system according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a switching tube according to an embodiment of the present application;

fig. 4 is a schematic structural diagram of a switching tube according to another embodiment of the present application.

Detailed Description

The present application will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present application, but are not intended to limit the present application in any way. It should be noted that various changes and modifications can be made by one skilled in the art without departing from the spirit of the application. All falling within the scope of protection of the present application.

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It should be noted that, if not conflicted, the various features of the embodiments of the present application may be combined with each other within the scope of protection of the present application. Additionally, while functional block divisions are performed in apparatus schematics, with logical sequences shown in flowcharts, in some cases, steps shown or described may be performed in sequences other than block divisions in apparatus or flowcharts. Further, the terms "first," "second," "third," and the like, as used herein, do not limit the data and the execution order, but merely distinguish the same items or similar items having substantially the same functions and actions.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In addition, the technical features mentioned in the embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.

In recent years, more and more electronic devices such as portable computers, digital cameras, mobile phones, portable audio devices, and bluetooth devices use a battery pack as a main power source, and the battery pack has the advantages of small size, high energy density, no memory effect, long cycle life, high-voltage battery, low self-discharge rate, and the like.

The battery pack comprises a battery pack and a battery management system, wherein the battery pack comprises a plurality of batteries which are connected in series or in parallel, and the battery management system comprises a voltage sampling module, a current sampling module, a controller, a switch circuit and the like. The voltage sampling module is used for collecting the voltage, the passive balance electric quantity and the like of the battery pack or each battery in real time, the current sampling module is used for sampling the current of the battery pack or each battery, the voltage sampling module and the current sampling module transmit the collected data to the controller (MCU), the controller determines protection measures corresponding to abnormal states such as undervoltage, overvoltage, overcurrent, short circuit, overtemperature, low temperature and the like required by the battery pack according to the collected data, and then the switching circuit is controlled to be selectively switched off or switched on according to the determined protection measures so as to implement the determined protection measures. It is understood that the voltage sampling module and the current sampling module can be implemented by an existing chip module (e.g., an integrated circuit IC) or a circuit conventional in the art, and the circuit structures of the voltage sampling module and the current sampling module are not described in detail herein.

As shown in fig. 1, the conventional switching circuit includes two MOS transistors and a fuse 20, the two MOS transistors are connected in series with the fuse 20, and control terminals of the two MOS transistors are respectively connected to a controller 30. Then, the switching circuit connects the battery pack 10 and the external device 40 (load or charger), which corresponds to the switching circuit being connected in series with the external device 40. It is understood that the MOS transistor can be turned on and off in a current threshold range or a voltage threshold range by a driving voltage applied by the controller 30. When the controller 30 determines that an abnormal state such as overcurrent, overcharge, or overtemperature occurs according to data collected by the voltage sampling module and the current sampling module in the battery management system, the MOS transistor is controlled to be turned off, so that the battery pack 10 is disconnected from the external device 40 (a load circuit or a charging circuit), thereby preventing the battery pack 10 from being exploded due to the overcurrent, overvoltage, or overtemperature.

However, when the current in the loop formed by the battery pack 10, the switching circuit and the external device 40 is larger than the current threshold of the MOS transistor, the MOS transistor may not be turned off, for example, when the current in the loop is larger than the current threshold of the MOS transistor, the MOS transistor may be broken down, and the MOS transistor may not be turned off. In this case, since the external device 40 (load or charger) is connected to the switching circuit, the current in the switching circuit may not reach the current required for the fuse 20 to be blown, and thus, the fuse 20 is not blown immediately, so that the battery pack 10 is continuously over-current and is in danger of being ignited and exploded.

In view of the above problem, as shown in fig. 2, an embodiment of the present application provides a switching circuit, which includes a switching tube 50 and a fuse 60 connected in series, where a first end of the switching circuit is used to connect with a positive electrode of the battery pack 10, a second end of the switching circuit is used to connect with a negative electrode of the battery pack 10, and a control end of the switching tube 50 is further connected with the controller 30, so that the switching tube 50, that is, the switching circuit and the battery pack 10 form a protection circuit, can be controlled to be turned on and off by the controller 30.

The fuse 60 is used to connect the battery pack 10 and the external device 40 (load or charger), i.e., the battery pack 10, the fuse 60, and the external device 40 may constitute a charge and discharge circuit. The fuse 60 is a device that fuses when a current passing through the charge and discharge circuit satisfies a fusing condition, for example, the fuse 60 may be a fuse, and the fusing condition may be that the current exceeds a certain threshold and lasts for a preset time (i.e., the heat accumulation exceeds a certain degree). Here, the fuse 60 and the blowing condition are not limited in any way, and those skilled in the art can select a fuse and determine a blowing condition according to actual situations.

Normally, the switch tube 50 is opened (i.e., the protection circuit is opened), and the battery pack 10, the fuse 60 and the external device 40 (load or charger) form a charge/discharge circuit to realize charging or discharging.

It can be understood that the current collecting module in the battery management system collects current in the charge and discharge circuit, the voltage collecting module collects voltage in the charge and discharge circuit and sends the voltage to the controller 30, and the controller 30 determines whether abnormality (over-current, over-voltage, over-temperature, etc.) occurs in the charge and discharge circuit according to the current or the voltage. When the controller 30 determines that the current in the discharging circuit is too large, or the voltage at the two ends of the battery pack 10 in the charging circuit is too large, or the temperature is too high, the controller 30 controls the switching tube 50 to be turned on, so that the protection circuit is turned on, that is, the fuse 60 is short-circuited and fused to disconnect the charging and discharging circuit, thereby preventing the battery pack 10 from being exploded due to overcurrent, overvoltage or overtemperature.

It can be seen that in this embodiment, the switch tube 50 is not in the charge-discharge circuit formed by the battery pack 10 and the external device 40, is not interfered by the current or voltage in the charge-discharge circuit, is driven only by the controller 30, and has high control accuracy.

In this embodiment, as shown in fig. 3, the switching tube 50 includes two transistors, each of which includes a semiconductor substrate 51, a source 52, a drain 53, an insulating layer 54 and a gate 55, the source 52 and the drain 53 are disposed on the semiconductor substrate 51 at intervals and are respectively connected to the semiconductor substrate 51, the insulating layer 54 is disposed on the semiconductor substrate 51 and between the source 52 and the drain 53, and the gate 55 is disposed on the insulating layer 54 and is respectively insulated from the source 51 and the drain 52.

The semiconductor substrate 51 is formed of a semiconductor material, which may include amorphous silicon, polysilicon, an organic material, a metal oxide, or amorphous indium gallium zinc oxide. The conductivity of the semiconductor material is between that of a conductor and an insulator, so that the semiconductor substrate 51 has no conductivity without being triggered by an external condition, but when electrons or holes inside the semiconductor substrate 51 are shifted by an electric field under a certain condition, for example, in an electric field environment, the concentration of electrons or holes in a central region of the semiconductor substrate 51 is increased, so that the semiconductor substrate 51 has conductivity.

Wherein the drain electrode 53 and the source electrode 52 are formed of a conductive material, which may include a metal, such as aluminum, molybdenum, tungsten, chromium, a button, or a combination thereof. The drain 53 and the source 52 are disposed on the semiconductor substrate 51 at intervals and electrically connected to the semiconductor substrate 51, respectively. In some embodiments, the source electrode 52 and the drain electrode 53 may be directly connected to the semiconductor substrate 51, and when the semiconductor substrate 51 has conductivity in a region adjacent to the source electrode 52 and the drain electrode 53 under an electric field, the source electrode 52 and the drain electrode 53 may be electrically connected to the semiconductor substrate 51 based on the fact that the source electrode 52 and the drain electrode 53 also have conductivity. In order to increase the conductivity between the metal and the semiconductor, in some embodiments, two spaced apart highly doped regions 56 (i.e., N + regions) may be fabricated on the semiconductor, and the impurity in the highly doped regions 56 may be an N-type impurity, so that there are a large number of electron sources in the highly doped regions 56 that provide free electrons for current flow, and metal electrodes are respectively led out from the two highly doped regions 56 as the source 52 and the drain 53, i.e., so that the source 52 and the drain 53 are respectively indirectly connected to the semiconductor substrate 51. When the semiconductor substrate 51 has conductivity in a portion between the two highly doped regions 56 under an electric field, the conductivity is higher than that of the semiconductor based on the two highly doped regions 56, thereby enabling the source electrode 52 and the drain electrode 53 to be electrically connected.

The insulating layer 54 is made of an insulating material, and the insulating material may include silicon oxide, aluminum oxide, or the like. An insulating layer 54 is disposed on the semiconductor substrate 51 between the source 52 and the drain 53, and the insulating layer 54 serves to insulate the gate 55 from the semiconductor substrate 51.

Wherein the gate 55 is formed of a conductive material, which may include a metal, such as aluminum, molybdenum, tungsten, chromium, a button, or a combination thereof.

Based on the structure of the transistor, the controller 30 applies a positive voltage to the gate 55 to generate an electric field between the semiconductor substrate 51 and the gate 55, and under the action of the electric field, electrons in the semiconductor substrate 51 move toward the gate 55, and under the blocking action of the insulating layer 54, the electrons are collected on the surface of the semiconductor substrate 51 near the insulating layer 54, thereby forming a conductive channel. It is understood that the region where the conductive channel is located is referred to as a channel region 57, the shape and size of the channel region 57 are related to the shape and size of the gate 55, and the channel region 57 is located on the surface layer of the semiconductor substrate 51 close to the insulating layer 54 and is located within the projection of the gate 55 relative to the semiconductor substrate 51. Since the channel region 57 is conductive due to the conductive channel formed by the convergence of the electrons, when a potential difference exists between the source 52 and the drain 53, the electrons in the channel region 57 flow due to the potential difference, and a current is generated.

In addition, in this embodiment, the drains 53 of the two transistors constituting the switching tube 50 are electrically connected, and the gates 55 of the two transistors are electrically connected. The source electrodes 52 of the two transistors are connected in series with the fuse 60 and the positive and negative electrodes of the battery pack 10, and a potential difference is formed between the two source electrodes 52 under the action of the battery pack 10. Because the two transistors have their gates 55 electrically connected and a positive voltage is applied to the connection line between either gate 55 or both gates 55, the two gates 55 can be controlled to form an electric field, and the drains 53 of the two transistors are electrically connected, the two drains 53 have the same potential, so that when one transistor is turned on, the other transistor is also turned on. In addition, any one of the two sources 52 is at a high potential, and the other source 52 is at a low potential, and both sources can be conducted under the driving voltage of the gate 55, i.e., bidirectional conduction is realized, so as to meet the control requirement in the charging and discharging processes of the battery pack 10.

For example, if the external device 40 is a load, during the discharging process, the positive electrode potential of the battery pack 10 is higher than the negative electrode potential, the source 52 of the transistor 1# close to the positive electrode of the battery pack 10 is at a high potential, and the source 52 of the transistor 2# close to the negative electrode of the battery pack 10 is at a low potential, when the transistor 1# close to the positive electrode of the battery pack 10 is turned on, the potential of the drain 53 of the transistor 1# is increased, so that a potential difference is formed between the drain 53 and the source 52 of the transistor 2# and the transistor 2# is also turned on. If the external device 40 is a charger, during charging, the potential of the negative electrode of the battery pack 10 is higher than that of the positive electrode, the source 52 of the transistor 1# is at a low potential, the source 52 of the transistor 2# is at a high potential, and when the transistor 2# close to the negative electrode of the battery pack 10 is turned on, the potential of the drain 53 of the transistor 1# is increased, so that a potential difference is formed between the drain 53 and the source 52 of the transistor 1# and the transistor 1# is also turned on.

In some embodiments, the connection between the two gates 55 may be a wire connection, or a connection through a conductive channel filled with a conductive substance such as a conductive paste. In some embodiments, the two drains 53 may also be connected by a wire, or a conductive channel filled with a conductive substance such as conductive paste. It will be appreciated that in some embodiments, as shown in fig. 4, two drains 53 may also be contacted adjacent to each other to form a whole, i.e., equivalent to two transistors sharing a single drain 53.

As can be seen from the above, the switching tube 50 has a simple structure, and can realize bidirectional conduction without a complicated connection structure. Whether the battery pack 10 is in a charging process or a discharging process, when overcurrent or over-charging voltage occurs, or when the temperature is too high, the driving voltage can be applied to the gate 55 by the controller 30 to control the two transistors to be turned on, so that the switching circuit is connected, that is, the fuse 60 is short-circuited, and the fuse 60 is rapidly fused, so that the battery pack 10 is not exploded due to overcurrent, overvoltage or over-temperature.

In some embodiments, referring to fig. 2 again, the switch circuit further includes a resistor 70, the resistor 70 is connected in series with the switch tube 50 and the fuse 60, on one hand, when the switch circuit is turned on, the resistor 70 can divide voltage to prevent the current in the circuit from being too large, but can satisfy the fusing condition, so that the potential safety hazard caused by excessive heat generated by fusing the fuse 60 can be eliminated, and on the other hand, when the battery pack 10 is connected to the external device 40 (load or charger) through the resistor 70, it is convenient to collect electrical signals at two ends of the resistor 70 to determine the current or voltage in the charge and discharge circuit.

To sum up, the switching circuit that this application embodiment provided, including switch tube and the fuse of establishing ties, the first end of switching circuit is used for being connected with the positive pole of group battery, and the second end of switching circuit is used for being connected with the negative pole of group battery, and the fuse is used for connecting group battery and external equipment (load or charger), because the switch tube is connected with the controller, can be through switching on and the disconnection of controller control switch tube. Under the normal condition, the switch tube disconnection, group battery and external equipment normal connection, when taking place unusually (overcurrent, overvoltage or excess temperature etc.), switch on through the switch tube, can make the fuse short circuit take place the fusing, and then the connection of disconnection group battery and external equipment for the group battery can not take place to explode because of factors such as overcurrent, overvoltage or excess temperature. And secondly, the switch tube is not arranged in a charge-discharge loop formed by the battery pack and the external equipment, is not interfered by current or voltage in the charge-discharge loop, is driven by the controller only, and can timely and accurately control the electric connection between the battery pack and the external equipment.

When the switch tube is turned on, the fuse is blown out when the duration time of the current and the current in the protection loop needs to meet the blowing condition, and in order to enable the switch tube to bear the current and the current time specified by the blowing condition, for example, the fuse can bear 300A of current and last for 2-5 seconds, namely, the fuse can be smoothly blown out, and the switch tube is not damaged by large current, the switch tube is required to have the capacity of resisting the large current.

In some embodiments, the material of the semiconductor substrate comprises silicon carbide. The silicon carbide has unique electrical properties of high critical field, high bulk mobility, high saturation velocity and the like. Particularly, the high critical field enables a transistor with silicon carbide as a substrate to have higher doping concentration and thinner drift layer thickness compared with a transistor with silicon as a substrate under the same voltage, thereby realizing lower on-resistance and higher electron mobility. The electron mobility is a physical quantity used in solid physics for describing the degree of speed of electrons in a metal or a semiconductor moving under the action of an electric field. Based on that carborundum itself has higher electron mobility, under the electric field effect, the inside electron of carborundum can the rapid draing, collects in the channel region, forms higher electric current to, carborundum can not be because of the heavy current punctures, and then, makes the transistor and the switch tube that constitutes by two transistors have the ability of nai heavy current.

In this embodiment, silicon carbide is used as the semiconductor substrate, and the silicon carbide itself has a high electron mobility, so that the transistor and the switching tube formed by the two transistors have a high current resistance, and further, the switching tube has good stability and cannot be damaged by a high current, and thus, the switching circuit failure caused by the failure of the switching tube can be avoided.

The switch tube is driven by the controller, so that the interference of current or voltage in a charge-discharge loop is avoided, and the control accuracy is high. In order to enable the switching tube to be directly controlled by the controller, no additional level conversion circuit is needed, and the threshold voltage of the switching tube should be less than the maximum voltage signal that the controller can output. It can be understood that the switching tube is turned on when the driving voltage applied to the switching tube by the controller is greater than or equal to the threshold voltage.

In order to adapt the threshold voltage of the switching tube to the output voltage of the controller, e.g. the maximum voltage of the controller output is 3.3V, the threshold voltage should be less than or equal to 3.3V. In some embodiments, the dielectric constant of the material of the insulating layer is 6 to 9. It is understood that the dielectric constant is the ability of a substance to hold a charge, and that a higher dielectric constant results in a larger capacitance formed between the gate and the semiconductor substrate, indicating a larger ability of the capacitance to store a charge, and thus, a larger change in charge due to a change in unit voltage results in a smaller threshold voltage.

In some embodiments, the material of the insulating layer comprises silicon nitride. Silicon nitride has a high dielectric constant (the dielectric constant is in a range of 6-9), and the insulating layer of the conventional transistor is made of silicon dioxide, which has a dielectric constant of only about 4.2, so that the transistor has a low threshold voltage compared with the conventional transistor which uses silicon nitride as the insulating layer.

In the embodiment, the material with high dielectric constant is used as the insulating layer, so that the capacitance formed between the grid and the semiconductor substrate can be effectively increased, the threshold voltage is reduced, the threshold voltage is smaller than or equal to the maximum voltage signal which can be output by the controller, namely, the switch tube can be directly controlled by the controller, an additional level switching circuit is not needed, and the switch circuit is simplified.

To further reduce the threshold voltage, in some embodiments, the channel region is doped with N-type impurities. It will be appreciated that the channel region is located at a surface layer of the semiconductor substrate adjacent to the insulating layer and within a projection of the gate electrode relative to the semiconductor substrate.

Wherein, the N-type impurity is an impurity with rich electrons. Among the N-type impurities, mainly negatively charged electrons participating in the conduction, for example the N-type impurities may comprise arsenic and/or phosphorus, which can increase the conductivity of the channel region

Taking the example that the N-type impurity includes phosphorus atoms, it is exemplified that the N-type impurity can increase the conductivity of the channel region. Specifically, phosphorus atoms have 5 valence electrons, and in a semiconductor substrate made of silicon carbide, phosphorus atoms share 4 valence electrons for 4 silicon atoms around the phosphorus atoms, 4 pairs of electrons give 8 shared electrons to the phosphorus atoms, and 1 unshared electron is added, and 9 valence electrons are shared in total. Since the phosphorus valence layer can only accommodate 8 electrons, the 9 th electron is not released. This electron is discarded by the phosphorus atom and freely migrates into the crystal structure. Thus, each phosphorus atom added to the channel region can generate one free electron.

It will be appreciated that the more free electrons in the channel region, the more conductive and the less resistive, and thus, less drive voltage is required to achieve the desired electron concentration in the channel region for current generation.

That is, in this embodiment, the N-type impurity is added to the channel region to increase the free electrons in the channel region, so as to improve the conductivity of the channel region and reduce the resistance of the channel region, and the electron concentration in the channel region can reach the electron concentration required for forming a current under a smaller driving voltage to trigger the conduction of the switching tube, thereby effectively reducing the threshold voltage.

It will be appreciated that the switching circuit or the entire battery management system is provided on a circuit board, wherein the circuit board may be a PCB board. In some embodiments, the connection points of the sources of the two transistors and the gates of the two transistors are respectively soldered on the circuit board. In the embodiment, the source electrodes and the grid electrodes of the two transistors face the circuit board, are mounted on the surface of the circuit board, and are then soldered by means of reflow soldering, dip soldering or the like, so that the connection points of the source electrodes of the two transistors and the grid electrodes of the two transistors are soldered on the circuit board respectively.

The conventional method for mounting the transistor is to glue the transistor on the circuit board, and then lead the transistor to another element on the circuit board through the lead. The process flow comprises the following steps: cleaning the circuit board, dispensing, transistor pasting, baking glue, lead wires and the like are very tedious.

Compared with the traditional installation method, on one hand, the metal forming the two source electrode and two grid electrode connection points is directly in welding contact with the metal foil on the circuit board, so that heat dissipation is facilitated, the switch tube is lighter and thinner, and good in anti-collision and anti-pressure capacity, therefore, the switch tube can be continuously started under a high-current condition, the reliability of the switch circuit can be further improved, on the other hand, other elements on the circuit board are required to be welded and installed, the switch tube can be welded with other elements together, an extra installation process is not required, and installation can be simplified.

In order to avoid contamination or damage of the switching tube due to direct exposure to air, in some embodiments, the surface of the switching tube remote from the circuit board is provided with an insulating glue. Specifically, after welding of the switch tube is completed, insulating glue is applied to the switch tube in a point brushing mode, and the switch tube is packaged. By selecting proper insulating cement, the insulating cement has the effects of water resistance, corrosion resistance, dust resistance, static electricity resistance, oxidation resistance, ultraviolet ray resistance and the like, and the switch tube is well protected.

To sum up, the switching circuit that this application embodiment provided, including switch tube and the fuse of establishing ties, the first end of switching circuit is used for being connected with the positive pole of group battery, and the second end of switching circuit is used for being connected with the negative pole of group battery, and the fuse is used for connecting group battery and external equipment (load or charger), because the switch tube is connected with the controller, can be through switching on and the disconnection of controller control switch tube. Under the normal condition, the switch tube disconnection, group battery and external equipment normal connection, when taking place unusually (overcurrent, overvoltage or excess temperature etc.), switch on through the switch tube, can make the fuse short circuit take place the fusing, and then the connection of disconnection group battery and external equipment for the group battery can not take place to explode because of factors such as overcurrent, overvoltage or excess temperature. And secondly, the switch tube is not arranged in a charge-discharge loop formed by the battery pack and the external equipment, is not interfered by current or voltage in the charge-discharge loop, is only driven by the controller, and can timely and accurately control the electric connection between the battery pack and the external equipment.

Based on the same inventive concept, another embodiment of the present application further provides a battery management system, including the switch circuit in any of the above embodiments. In this embodiment, the structure and function of the switch circuit are the same as those of the switch circuit in the above embodiment, and are not described in detail here.

Based on the same inventive concept, another embodiment of the present application further provides a battery pack, which includes a battery pack and the battery management system in the above embodiment, wherein the battery pack supplies power to the battery management system. The battery pack comprises a plurality of single batteries which are connected in series or in parallel, and the anode and the cathode of the battery pack are connected with the battery management system to supply power for the battery management system. The battery management system has the same structure and function as those of the battery management system in the above embodiments, and is not described herein again.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; within the context of the present application, where technical features in the above embodiments or in different embodiments can also be combined, the steps can be implemented in any order and there are many other variations of the different aspects of the present application as described above, which are not provided in detail for the sake of brevity; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A switching circuit, comprising:

the switch circuit comprises a switch tube and a fuse which are connected in series, wherein a first end of the switch circuit is used for being connected with the positive pole of a battery pack, and a second end of the switch circuit is used for being connected with the negative pole of the battery pack;

the fuse is used for connecting the battery pack and external equipment;

the switch tube is connected with a controller, and the switch tube is configured to control the switch tube to be switched on and off through the controller;

the switch tube comprises two transistors, and each transistor comprises:

a semiconductor substrate, a semiconductor substrate and a semiconductor substrate,

the source electrode and the drain electrode are arranged on the semiconductor substrate at intervals and are respectively connected with the semiconductor substrate;

the insulating layer is arranged on the semiconductor substrate and is positioned between the source electrode and the drain electrode;

the grid electrode is arranged on the insulating layer and is respectively insulated from the source electrode and the drain electrode;

wherein the drains of the two transistors are electrically connected, and the gates of the two transistors are electrically connected.

2. The switching circuit of claim 1, wherein the material of the semiconductor substrate comprises silicon carbide.

3. The switch circuit according to claim 1, wherein the dielectric constant of the material of the insulating layer is 6 to 9.

4. The switch circuit of claim 3, wherein the material of the insulating layer comprises silicon nitride.

5. The switch circuit of claim 1, wherein a channel region is doped with N-type impurities, the channel region being located on a surface layer of the semiconductor substrate near the insulating layer and within a projection of the gate electrode with respect to the semiconductor substrate.

6. The switch circuit of claim 5, wherein the N-type impurity comprises arsenic and/or phosphorous.

7. The switch circuit according to claim 1, wherein connection points of the sources of the two transistors and the gates of the two transistors are soldered to a circuit board on which the switch circuit is located.

8. The switching circuit according to claim 7, wherein the surface of the switching tube remote from the circuit board is provided with an insulating glue.

9. A battery management system comprising a switching circuit according to any one of claims 1 to 8.

10. A battery pack comprising a battery pack and the battery management system of claim 9, the battery pack powering the battery management system.