CN216751227U

CN216751227U - Battery management circuit, battery management system and electric vehicle

Info

Publication number: CN216751227U
Application number: CN202123084688.0U
Authority: CN
Inventors: 马斌严
Original assignee: Malida Technology Nanjing Co ltd
Current assignee: Malida Technology Nanjing Co ltd
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2022-06-14
Anticipated expiration: 2031-12-09

Abstract

In an embodiment of the present application, a battery management circuit, a battery management system and an electric vehicle include: a power supply interface, a plurality of branches and a control unit. The battery interface in each branch circuit is coupled with a battery unit, and the negative electrode connecting end of the battery interface is coupled and grounded through the branch circuit switch unit and the current detection unit; the branch circuit switching unit comprises a switching element for switching on/off the branch circuit and a diode with the conducting direction pointing to the negative electrode connecting end of the battery, and the control unit drives the branch circuit switching unit to be switched on to form a second conducting path replacing the first conducting path or switch off the second conducting path according to the fact that the change of the current value in the branch circuit reaches a threshold value, so that the element is prevented from being overheated; when voltage difference exists between the batteries, the diode in the branch with lower voltage is cut off by reverse bias, so that charge and discharge between the batteries are avoided; in addition, the spark caused by sudden change of current can be avoided by matching with a main circuit switching unit which is started slowly; and a perfect battery hot plug scheme is realized.

Description

Battery management circuit, battery management system and electric vehicle

Technical Field

The present application relates to the field of battery management technologies, and in particular, to a battery management circuit, a battery management system, and an electric vehicle.

Background

At present, the electric vehicle is more and more widely applied, a technical scheme of parallel power supply of a plurality of batteries is adopted in a plurality of electric vehicles, and how to realize hot plug becomes a problem to be solved urgently when the batteries are replaced.

When a plurality of battery modules are directly connected in parallel, the voltages between batteries need to be very close, otherwise, the problems of battery overheating, mutual charging and discharging between batteries and the like caused by instant discharge can occur, and the batteries are easy to overheat and catch fire. Therefore, power supply can not be realized by directly and simply connecting a plurality of groups of batteries in parallel, so that the difficulty of realizing hot plug of the batteries is quite large in practice.

Currently, some control circuits are usually added to parallel connection of batteries to balance the voltages of different batteries to be the same. On the one hand, however, in a high-current application scenario of an electric vehicle, such a solution may cause circuit elements to generate high heat and have poor efficiency; on the other hand, when the input end of the power utilization system has a large input capacitance, the battery is connected in a hot plug mode, and a large pulse current can be generated at the moment when the battery is connected. The pulse current time is usually within one millisecond, but the current may be as high as hundreds of amperes, which easily causes the overcurrent protection of a Battery Management System (BMS) of the battery to operate and prevent the load from being started smoothly; in addition, sparking at the connector contacts can occur as a result of this pulse current. However, the current solution cannot solve the problem that sparks are generated at the battery contact due to instantaneous high current when the battery is hot-plugged.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a battery management circuit, a battery management system and an electric vehicle, which can solve the problems of the prior art well through a circuit structure and signal control.

A first aspect of the present application provides a battery management circuit, comprising: a power interface for coupling to a load, comprising: a positive output terminal and a negative output terminal; a plurality of branches; wherein each branch comprises: a battery interface, a branch switch unit and a current detection unit; the battery interface, for coupling to a battery cell, includes: the battery positive electrode connecting end is coupled with the positive electrode of the battery unit and the positive electrode output end of the power supply interface; the battery negative electrode connecting end is coupled with the negative electrode of the battery unit and is coupled with a common end of the plurality of branches through the branch switch unit and the current detection unit; the common terminal is coupled to the negative output terminal and grounded; the branch switch unit includes: a switching element and a diode element; the switching element includes: the current detection unit is respectively coupled to the negative end of the battery and two ends of the current detection unit, and the control end is used for controlling the connection or disconnection of the two ends; the diode element and the switch element are connected in parallel at the two ends, and the conduction direction of the diode element points to the negative electrode connecting end of the battery; wherein the diode turns on a first conductive path forming the branch circuit under a forward bias voltage when the branch circuit switching unit is turned off, or turns off to turn off the first conductive path under a reverse bias voltage generated by a voltage difference between the batteries; forming a second conductive path instead of the first conductive path when the branch switch unit is turned on; the current detection unit is used for detecting the current in the branch circuit to generate a first output signal; the control unit is coupled with the current detection unit in each branch circuit to obtain the current value of the current in each branch circuit according to each first output signal, and is coupled with the control end of the branch circuit switch unit in each branch circuit through a switch control driving circuit; the control unit is used for responding to the fact that the current value in one branch circuit reaches a first current threshold value, and outputting a first driving signal for enabling the corresponding branch circuit switch unit to be conducted; or, in response to the current value in one branch circuit decreasing below at least one second current threshold, outputting a second driving signal for turning off the corresponding branch circuit switching unit.

In an embodiment of the first aspect of the present application, the branch switch unit includes a first NMOS, a source of the first NMOS is coupled to the current detection unit, and a drain of the first NMOS is coupled to the battery negative connection terminal; the diode element is a parasitic diode of the first NMOS.

In an embodiment of the first aspect of the present application, the battery management circuit further includes: the main circuit switch unit is coupled in the main circuit between the common connection end and the negative output end and is coupled to the control unit so as to be controlled to be conducted when the control unit is started; wherein the main circuit switching unit includes a soft start circuit for it to be turned on or off slowly.

In an embodiment of the first aspect of the present application, the main circuit switch unit includes a second NMOS, a source of the second NMOS is coupled to the common terminal, a drain of the second NMOS is coupled to the negative output terminal, and a gate of the second NMOS is coupled to a slow start driving circuit controlled by the control unit, wherein the slow start driving circuit changes a driving voltage for turning on or off the main circuit switch unit slowly according to a driving signal of the control unit.

In an embodiment of the first aspect of the present application, the soft start driving circuit further includes: and the capacitor or the combination of the capacitor and the resistor is coupled between the grid and the drain of the second NMOS.

In an embodiment of the first aspect of the present application, a plurality of switch control drive circuits; each switch control driving circuit is coupled between the control unit and the control end of the branch switching unit in a branch, and is configured to output a corresponding first driving voltage or second driving voltage to the control end of the branch switching unit according to the received first driving signal or second driving signal.

In an embodiment of the first aspect of the present application, the method further includes: a plurality of voltage detection modules; each voltage detection module is coupled between a reference point in a branch and the control unit and is used for detecting the voltage of the reference point to generate a second output signal; and the control unit is used for obtaining the voltage values of the reference points in the branches according to the second output signals, comparing the voltage difference between the voltage values obtained by at least two branches, and taking the voltage difference lower than a preset voltage threshold value as a reference condition for turning on the branch switch unit in one of the branches to be turned on.

In an embodiment of the first aspect of the present application, the battery interface and the battery unit are coupled by hot-pluggable.

A second aspect of the present application provides a battery management system, comprising: a battery management circuit as claimed in any one of the first aspect.

A third aspect of the present application provides an electric vehicle comprising: the battery management system of the second aspect, the electric vehicle body is coupled to provide electrical energy.

A fourth aspect of the present application provides a battery management method applied to the battery management circuit of any one of the first aspects; the battery management method comprises the following steps: when the first branch of the battery management circuit is coupled with the first battery unit, the control unit drives the main circuit switch unit to be conducted; in response to that the current value detected by the current detecting unit in the first branch circuit reaches a first current threshold value or more, the control unit outputs a first driving signal for turning on the branch circuit switching unit in the first branch circuit to form a second conductive path instead of the first conductive path so as to form a power supply output of the first battery unit at the power supply interface; when a second branch of the battery management circuit is connected with a second battery unit, if the second battery unit is lower than the voltage of the first battery unit, a first conductive path in the second branch is limited to be conducted; when the voltage difference between the second battery unit and the first battery unit is eliminated, the second branch circuit forms a first conductive path; in response to that the current value detected by the current detecting unit in the second branch circuit reaches a first current threshold value or more, the control unit outputs a first driving signal for turning on the branch circuit switching unit in the second branch circuit, and forms a second conductive path for replacing the first conductive path of the second branch circuit, so as to form parallel output of the second battery unit and the first battery unit at the power supply interface; and in response to the current detected by the current detecting unit in a current branch decreasing below at least one second current threshold, the control unit outputs a second driving voltage for turning off the branch switch unit in the current branch, and turns off the second conductive path of the current branch to stop the power supply output of the corresponding battery unit to the power supply interface.

To sum up, in the battery management circuit, the battery management system and the electric vehicle in the embodiment of the present application, the battery management circuit includes: a power supply interface, a plurality of branches and a control unit. The battery interface in each branch circuit is coupled with a battery unit, and the negative connecting end of the battery interface is coupled and grounded through the branch circuit switch unit and the current detection unit; the branch circuit switching unit comprises a switching element for switching on/off the branch circuit and a diode with the conducting direction pointing to the battery cathode connecting end, and the control unit drives the branch circuit switching unit to be conducted to form a second conducting path replacing the first conducting path or disconnect the second conducting path according to the fact that the current value in the branch circuit changes to reach a threshold value, so that overheating of the element is avoided; when a voltage difference exists between the batteries, the diode in the branch circuit with lower voltage is cut off by reverse bias, so that charging and discharging between the batteries are avoided; in addition, the main circuit switching unit which is started slowly can be matched to avoid spark caused by sudden change of current; and a perfect battery hot plug scheme is realized.

Drawings

Fig. 1 shows a schematic structural diagram of a battery management circuit according to an embodiment of the present application.

Fig. 2A and 2B show application schematic diagrams of NMOS and PMOS, respectively, and their parasitic diodes.

Detailed Description

The following description of the embodiments of the present application is provided by way of specific examples, and other advantages and effects of the present application will be readily apparent to those skilled in the art from the disclosure herein. The present application is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present application. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

Embodiments of the present application will be described in detail below with reference to the accompanying drawings so that those skilled in the art to which the present application pertains can easily carry out the present application. The present application may be embodied in many different forms and is not limited to the embodiments described herein.

Reference throughout this specification to "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," or the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Furthermore, the particular features, structures, materials, or characteristics shown may be combined in any suitable manner in any one or more embodiments or examples. Moreover, various embodiments or examples and features of different embodiments or examples presented in this application can be combined and combined by those skilled in the art without contradiction.

Furthermore, the terms "first", "second" 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the expressions of the present application, "plurality" means two or more unless specifically defined otherwise.

In order to clearly explain the present application, elements that are not relevant to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

Throughout the specification, when it is said that a certain element is "coupled" to another element, this includes not only the case of "directly connecting", but also the case of "indirectly connecting" with other elements interposed therebetween. In addition, when a certain element "includes" a certain constituent element, unless otherwise stated, it means that other constituent elements may be included without excluding other constituent elements.

Although the terms first, second, etc. may be used herein to describe various elements in some instances, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, the first interface and the second interface are represented. Also, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, steps, operations, elements, modules, items, species, and/or groups, but do not preclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, modules, items, species, and/or groups thereof. The terms "or" and/or "as used herein are to be construed as inclusive or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any of the following: a; b; c; a and B; a and C; b and C; A. b and C ". An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" include plural forms as long as the words do not expressly indicate a contrary meaning. The term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and/or components.

Although not defined differently, including technical and scientific terms used herein, all terms have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Terms defined in commonly used dictionaries are to be additionally interpreted as having meanings consistent with those of related art documents and currently prompted messages, and should not be excessively interpreted as having ideal or very formulaic meanings unless defined.

Generally, an electric vehicle is powered by a battery pack, which may include a plurality of batteries connected in parallel. However, as previously mentioned, there are difficulties in achieving hot plugging of the batteries in the battery pack. On one hand, when the batteries are required to be plugged and unplugged (for example, when the batteries are replaced or installed), the voltages among the batteries are nearly the same, and the problems of loss and heating caused by mutual charging and discharging of the batteries can be avoided; on the other hand, it is necessary to reduce the current generated instantaneously when the battery is inserted and removed to avoid the problems of occurrence of sparks, burning of the battery, or damage to the connector. On the other hand, a set of precise and controllable schemes is needed to solve the problems.

In view of this, the present disclosure provides a battery management circuit for solving the above problems, and achieving good hot plugging and achieving parallel operation between batteries.

In particular, the "battery" referred to in the embodiments of the present application may be a battery applied to an electric vehicle such as an electric bicycle, an electric vehicle, or the like; alternatively, it may be a battery used in other electrically powered devices. The battery management circuit in the embodiment of the application aims to solve the problem of hot plug of the batteries, and can be an application scene of the battery management circuit as long as the scene of the battery hot plug problem exists.

Referring to fig. 1, a schematic structural diagram of a battery management circuit 100 according to an embodiment of the present application is shown.

The battery management circuit 100 may have access to a plurality of battery cells. Fig. 1 shows 2 battery units connected to the battery unit, namely a first battery unit 201 and a second battery unit 202. Each battery unit can comprise a single battery, and also can comprise a battery pack formed by connecting a plurality of single batteries.

The battery management circuit 100 may include: a power supply interface 101, a plurality of branches and a control unit 102.

The power supply interface 101 is for coupling to a load 203. The power supply interface 101 includes: a positive output terminal P + and a negative output terminal P-. After the battery management circuit 100 is connected to the battery, an output voltage may be formed between two ends of the positive output terminal P + and the negative output terminal P-of the power supply interface 101, so as to supply power to the load 203.

Each branch of the plurality of branches is used for accessing one battery unit, and the branches are coupled in parallel with each other. Wherein each branch may comprise: a battery interface, a bypass switch unit and a current detection unit. In the embodiment of fig. 1, two branches, i.e., a first branch and a second branch, in the battery management circuit 100 are exemplarily illustrated corresponding to a dual battery supply manner of the first battery cell 201 and the second battery cell 202. The first branch includes: a first battery interface, a first branch switch unit 103A, and a first current detection unit 104A; the second branch circuit includes: a second battery interface, a second branch switch unit 103B and a second current detection unit 104B. It is understood that, if more battery units need to be accessed, more branches need to be correspondingly shown, and the embodiment is not limited to the illustrated embodiment.

The structure of each branch may be the same, so the following is representatively described by taking the first branch as an example.

In the first branch, the first battery interface includes: a first cell positive connection terminal and a first cell negative connection terminal. The first positive battery connection terminal is coupled to the positive electrode of the first battery cell 201 and to the positive output terminal P + of the power supply interface 101. The first battery negative connection terminal is coupled to the negative electrode of the first battery unit 201, and is coupled to a common terminal of each branch circuit through the first branch switch unit 103A and the first current detection unit 104A. The common terminal may be coupled to the negative output terminal P-and to a ground terminal.

Each of the branch switching cells may include: a switching element and a diode element; the switching element includes: the current detection unit is coupled to the negative terminal of the battery and the two terminals of the current detection unit respectively, and a control terminal for controlling the on/off of the two terminals. The diode element and the switch element are connected in parallel at the two ends, and the conduction direction of the diode element points to the battery cathode connecting end. The switching element and the diode element are respectively conducted to correspond to different conducting paths of the branch circuit switching unit, the diode element forms a first conducting path when being conducted, and the switching element forms a second conducting path replacing the first conducting path when being conducted.

In some embodiments, the branch switching unit may be implemented by one or more MOSFETs (hereinafter, abbreviated as "MOS"). The two ends of the switch element can be correspondingly the drain electrode and the source electrode of the MOS, and the control end is the grid electrode of the MOS. Due to the structural characteristics of the MOS, a parasitic Diode (also called "Body Diode element") is equivalently formed between the source and the drain. The parasitic diode may serve as the diode element.

Taking the first branch switch unit 103A in fig. 1 as an example, the first branch switch unit 103A may be implemented by, for example, a first NMOS. In the example of fig. 1, the gate of the first branch switch unit 103A is coupled to the control unit 102 to drive the switch state thereof by the control unit 102. By controlling the gate-source voltage V between the gate (G pole) and the source (S pole) of the MOS_GSAnd a threshold voltage V_thTurn on the source and drain (D pole) while satisfying a predetermined relationship, and turn off when not satisfying, for example, when NMOS satisfies V_GS>V_thIs on when PMOS satisfies V_GS<V_thIs turned on. Therefore, MOS is often used for the implementation of switches.

As shown in fig. 2A and fig. 2B, which are schematic diagrams of NMOS and PMOS, respectively, the conduction direction of the parasitic diode is opposite to that of the MOS. For example, in fig. 2A, the conduction direction of the NMOS is D to S, and the conduction direction of the corresponding parasitic diode is S to D. In fig. 2B, the conduction direction of the PMOS is S to D, and the conduction direction of the corresponding parasitic diode is D to S. Therefore, the parasitic diode allows current to flow when the MOS is off.

In the example of fig. 1, the first bypass switch unit 103A is exemplarily selected to be a first NMOS, the drain thereof is coupled to the battery negative terminal, and the source thereof is coupled to the current detection unit. The conduction direction (i.e., S to D poles in this example) of the parasitic diode 1031A formed by the first branch switching unit 103A is directed to the battery negative electrode connection terminal. The states of the parasitic diode 1031A include: when the branch switch unit is turned off, if the branch switch unit is subjected to a forward bias voltage from S to D (higher than a conduction threshold value of the forward bias voltage), a first conductive path forming the first branch is conducted; or, when subjected to a reverse bias voltage, to maintain the first conductive path open. When the first branch switch unit 103A is turned on, a second conductive path (i.e., S to D pole in this example) is formed instead of the first conductive path.

When a voltage difference exists between the battery cells of different branches, for example, when the output voltage of the second battery cell 202 is higher than that of the first battery cell 201, a voltage difference between the first battery cell 201 and the second battery cell 202 forms a reverse bias voltage (D to S pole) at two ends of the parasitic diode 1031A of the first branch switch unit 103A in the first branch where the first battery cell 201 with a relatively lower voltage is located, the first conductive path cannot be conducted, and the first battery cell 201 cannot be charged by the second battery cell 202 by controlling the first branch switch unit 103A to be disconnected, that is, the second conductive path is disconnected. It is inferred that since each of the other branches has the same structure as the first branch, the charging of the other battery cells can be avoided under the action of the diode of the respective switching unit, such as the second branch switching unit 103B and the parasitic diode 1031B formed thereby.

In other embodiments, the first branch switch unit 103A may also be implemented by PMOS, and the source thereof corresponds to the battery negative connection terminal, and the drain thereof corresponds to the current detection unit, so as to configure that the switch conduction direction is the same as that in fig. 1, and the conduction direction of the parasitic diode 1031 is still directed to the battery negative connection terminal, and based on the difference between NMOS and PMOS, other circuit structures may also be changed correspondingly.

In addition, it should be specifically noted that although the first branch switch unit 103A and the second branch switch unit 103B in the embodiment of fig. 1 are exemplarily illustrated as MOS switches, it is understood that other combinations of elements that can obtain the same effect may be used instead of the MOS switches in other embodiments. For example, a Bipolar Junction Transistor (BJT), an Insulated Gate Bipolar Transistor (IGBT), or a relay is used as an element that can form the second conductive path, and is connected in parallel with a diode device (instead of a parasitic diode function) that can form the first conductive path, so as to be used in combination to realize a function similar to the above-described branch switching unit, instead of the MOS switching element.

The first current detecting unit 104A is configured to detect a current in the first branch and output a first output signal. In some embodiments, each current detection unit may be implemented by a current detection circuit constructed based on a sampling resistor and/or an operational amplifier, for example.

The power supply loop of the first battery is shown from the battery anode of the first battery unit 201 to the battery cathode through the first battery anode connection terminal, the anode output terminal P +, the load 203, the cathode output terminal P-, the first current detection unit 104A, the first bypass switch unit 103A, the first battery cathode connection terminal.

The second branch may have the same structure as the first branch, and the power supply loop of the second battery unit 202 is shown from the battery anode of the second battery unit 202 to the battery cathode through the second battery anode connection terminal, the anode output terminal P +, the load 203, the cathode output terminal P-, the second current detection unit 104B, the second branch switch unit 103B, and the second battery cathode connection terminal.

In some embodiments, the configuration of elements between the branches may be the same. For example, the first branch switch unit 103A and the second branch switch unit 103B select the same device to implement, and the first current detection unit 104A and the second current detection unit 104B select the same circuit to implement. Alternatively, it may be changed as needed.

The control unit 102 is coupled to the current detection units in the branches to obtain current values of the currents in the branches according to the first output signals, and is coupled to the control ends of the branch switch units in the branches to control on/off of the branch switch units. For example, in fig. 1, the control unit 102 is coupled to the gates of the first branch switch unit 103A and the second branch switch unit 103B, respectively. In some embodiments, the control unit 102 may be implemented by, for example, a Microprocessor (MCU) having a plurality of ports respectively coupled to the current detection units, the branch switch units, and the like, such as general purpose input/output (GPIO) ports. For the control unit 102, each branch can be regarded as a "channel" for power supply, and the control unit 102 outputs a driving signal to the branch switching unit of each branch, that is, the driving signal to the "channel" of the branch. In addition, the control unit 102 includes an analog-to-digital converter (ADC), and the current detection unit outputs an analog current signal to the control unit 102, and converts the analog current signal into a detected current value through the ADC. In some embodiments, a switch control driving circuit may be disposed between the control unit 102 and the branch switching units of each branch for generating a corresponding driving voltage according to a driving signal of the control unit 102 to drive the branch switching units to be turned on or off. For example, in fig. 1, a first switch control driving circuit 106A is coupled between the control unit 102 and the first branch switch unit 103A, and a second switch control driving circuit 106B is coupled between the control unit and the second branch switch unit 103B.

Optionally, the battery management circuit 100 further includes a main circuit switch unit 105, coupled in the main circuit between the common terminal and the negative output terminal P ", for controlling on/off of the main circuit. The control unit 102 may be coupled to the main circuit switching unit 105 to control it to be turned on or off. In some embodiments, such as fig. 1, the main circuit switch unit 105 may include a second NMOS having a gate coupled to a soft start driving circuit controlled by the control unit, the soft start driving circuit slowly changes a driving voltage for turning on or off the main circuit switch unit according to a driving signal of the control unit, a source coupled to the common terminal, and a drain coupled to the negative output terminal P-. When the accessed battery unit is triggered to start, the control unit 102 may turn on the main switch unit 105 to turn on the power supply loop of the load 203. It should be noted that in other examples, the main circuit switching unit may be replaced by a functionally similar BJT, IGBT, or relay, for example, and the MOS switch illustrated in the drawings is not limited.

The control unit 102 may control the on/off of the branch switch unit according to the detected current value, so as to control the power supply of the battery unit of each path, and by matching the characteristics of the branch switch unit, some problems related to the background art may be solved. Specifically, the control unit 102 is configured to output a first driving signal for turning on a corresponding branch switch unit in response to that a current value in a branch is greater than or equal to a first current threshold; or, in response to the current value in one branch circuit decreasing below at least one second current threshold, outputting a second driving signal for turning off the corresponding branch circuit switching unit. Wherein the first current threshold corresponds to a current setting in a first conductive path formed by conduction of a parasitic diode 1031 in the branch switching unit; the second current threshold corresponds to a current setting in the second conductive path.

It should be noted that the detected current value in the branch may have "+", "-", such as 1A, -1A, etc. The "+", "actually indicate the direction of current flow, which in each branch of the battery management circuit of the present application corresponds to the fact that the current flow may be the discharge current of the battery connected to the branch or the charging current of the battery being charged. The purpose of the second current threshold is to discriminate the situation that the discharging current of the battery is too low or the battery is charged, and trigger the control unit 102 to close the second conductive path of the branch under these circumstances. Therefore, for these situations, the second current threshold may be set to multiple values, such as a positive value x and a negative value y, and when the current value a < x in the branch is detected, it indicates that the battery in the branch has too low discharge current to close the second conductive path; alternatively, when it is detected that the current value b < y in the branch, i.e. b reaches below y, assuming that y is-1A, b is-1.1A or-1.2A, etc., a decrease in b actually indicates an increase in the current to which the battery is charged, and b < y indicates that the current value to which the battery is charged reaches a second predetermined threshold, the second conductive path may be triggered to be closed to prevent the batteries from being charged and discharged.

In order to facilitate the control unit 102 to more accurately determine the time when the voltage difference between the battery units disappears, in some embodiments, the battery management circuit may further include a plurality of voltage detection units, each of the voltage detection terminals may be coupled between a reference point in a branch and the control unit to detect the voltage and generate second output signals to be output to the control unit, and the control unit obtains the voltage value of the reference point of each branch according to each of the second output signals. For example, as illustrated in fig. 1, the reference point may be drains of branch switching cells in a branch, such as drains of the first branch switching cell 103A and the second branch switching cell 103B. The control unit 102 may be connected to the first voltage detecting unit 107A in the first branch and the second voltage detecting unit 107B in the second branch, respectively, to obtain output signals of reference points of the two branches, and obtain two voltage values through ADC conversion, respectively, and further may calculate a voltage difference between the two voltage values, to be used as a reference condition for turning on the related branch to be turned on, that is, as a reference condition matched with a condition that a current value of the detection current of the branch to be turned on reaches a first current threshold value or more. Optionally, the control unit 102 may further detect a voltage value of the positive output terminal P + through the third voltage detecting unit 108 as a reference voltage value.

The control principle of the battery management circuit 100 is described below in conjunction with a number of scenarios.

Scene 1: first battery unit access

Assuming that the power management circuit is not initially connected with the battery unit; when the first battery unit is connected to the power management circuit, refer to fig. 1, for example, the first battery unit 201 is coupled to the first battery interface, or the second battery unit 202 is coupled to the second battery interface. For example, taking the first battery unit 201 coupled to the first battery interface as an example, a forward bias voltage is generated across the parasitic diode 1031A of the first branch switch unit 103A, so that the parasitic diode 1031A is turned on from the S pole to the D pole in the forward direction. Thus, when the control unit 102 drives the main circuit switching unit 105 to turn on the main circuit, the first conductive path formed by the conduction of the parasitic diode 1031 is matched with the main circuit to form the power supply circuit, and the power supply circuit starts to operate. When the first current detecting unit 104A detects that the current is greater than the predetermined threshold, the control unit 102 controls the driving circuit 106A to drive the first branch switch unit 103A to be turned on through the first switch to form a second conductive path, and the second conductive path replaces the original first conductive path due to the low impedance when the MOS switch is turned on. Therefore, the power loss caused by the product of the forward voltage drop and the forward current when the parasitic diode 1031A is turned on can be greatly reduced, the heat generated by the element is reduced, and the first branch switch unit 103A is prevented from being burnt by the heat generated by the excessive current of the load 203. In addition, the power supply of the battery unit is reduced corresponding to the situations such as the electric vehicle staying, the flameout, etc., and when the first current detecting unit 104A detects that the current value is smaller than the second current threshold, the control unit 102 drives the first branch switch unit 103A to be turned off. At this time, the current is very low, and even if the first battery unit supplies power to the load 203 through the parasitic diode 1031A, a large amount of power loss is not generated; in the case of connecting a plurality of battery units, it is also possible to prevent the battery from being charged by other battery units.

Scene 2: multiple cell access

In the case where the battery management circuit 100 has a battery cell connected thereto, if a new battery cell is connected thereto, it may be necessary to cope with the fact that the output voltage of the existing battery cell is higher than that of the new battery cell, which may cause the discharge of the new battery cell from the existing battery cell. As described above, the parasitic diode formed by the branch switch unit of each branch can prevent the mutual charging and discharging between the batteries.

For example, referring to fig. 1, when the second battery unit 202 is coupled to the second branch of the battery management circuit 100, the output voltage of the existing first battery unit 201 is higher than the output voltage of the newly connected second battery unit 202, thereby forming a voltage difference. Accordingly, the parasitic diode 1031B of the second branch switch unit 103B in the second branch is subjected to a reverse bias voltage formed by the voltage difference, so that the power supply loop of the second branch is in an open circuit state, and the second battery unit 202 cannot supply power and is not charged. The first battery unit 201 continues to supply power to the load 203. As the load 203 continuously consumes power, the output voltage of the first battery unit 201 gradually decreases, and once the output voltage decreases to be the same as the output voltage of the second battery unit 202, the parasitic diode 1031B of the second branch switch unit 103B in the second branch is turned on to form, so that the second battery unit 202 starts to supply power to the load 203, thereby achieving the effect of supplying power in parallel with the first battery unit 201. When the second current detecting unit 104B detects that the current in the branch is greater than the preset first current threshold, the control unit 102 controls the driving circuit 106B to drive the second branch switch unit 103B to enter the conduction state through the second switch to form a second conductive path, and since the impedance is very low when the MOS switch is conducted, the second conductive path replaces the first conductive path, the power loss generated by the product of the forward voltage drop and the forward current when the MOS switch is conducted through the parasitic diode 1031B can be greatly reduced; the heating of the element is reduced, and the MOS switch is prevented from being burnt by the heat generated by the overlarge current of the load 203.

When the current detecting unit in any branch detects that the current is smaller than the second current threshold, indicating that the output voltage of the corresponding battery unit may be weakened, the control unit 102 turns off the corresponding branch switch unit to prevent the battery unit from being charged by other battery units and avoid unnecessary loop current.

In order to avoid the generation of sparks, the sudden current change during the hot plugging of the battery needs to be controlled.

In some embodiments, the main circuit switching unit 105 may include a slow start circuit for slow conduction for smoothing current changes in the branch.

As illustrated in fig. 1, a soft start driving circuit 1052, coupled between the control unit 102 and the main circuit switching unit 105, is used for slowly changing a driving voltage for turning on or off the main circuit switching unit 105 according to a driving signal of the control unit 102. When any battery unit is connected to the battery management circuit 100, the control unit 102 slowly turns the second NMOS 1051 into a conducting state by slowly starting the driving circuit 1052 after being started, for example, controls the gate voltage of the second NMOS 1051 to slowly rise until being in a conducting state, so as to suppress the pulse current that suddenly changes instantly.

Because the MOS is mainly operated in a conducting state or a non-conducting state, the MOS is prevented from being operated in a semi-conducting state as much as possible. Therefore, to achieve the effect of slow turn-on, in some embodiments, the slow start driving circuit 1052 may further include a capacitor coupled between the D-pole and the G-pole of the second NMOS 1051, or a combination of a capacitor and a resistor (e.g., a series connection or a parallel connection of one or more capacitors and one or more resistors), so as to slow the turn-on speed of the second NMOS 1051, and smooth the abrupt current at the turn-on moment into a smaller current to charge the load 203, thereby effectively preventing the generation of contact sparks and also preventing the main circuit switch unit 105 from being damaged.

The problems of overheating elements, mutual charging and discharging of the batteries, spark elimination during plugging and unplugging of the batteries and the like are solved, and a good battery hot plugging scheme can be realized.

The embodiment of the present application may further provide a battery management system, including: the battery management circuit described in the previous embodiment. The battery management system can be accessed into a plurality of battery units in a hot-pluggable mode and can supply power in parallel.

An embodiment of the present application may further provide an electric vehicle, including: the battery management system. In some embodiments, the electric vehicle may include an electric moped, an electric automobile, or the like, including an electric motor. Through each battery unit accessed by the battery management system, the motor can be powered in parallel.

The above embodiments are merely illustrative of the principles and utilities of the present application and are not intended to limit the application. Any person skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present application. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present disclosure be covered by the claims of the present application.

Claims

1. A battery management circuit, comprising:

a power interface for coupling to a load, comprising: a positive output terminal and a negative output terminal;

a plurality of branches; wherein each branch comprises: a battery interface, a branch switch unit and a current detection unit;

the battery interface, for coupling to a battery cell, includes: the battery positive electrode connecting end is coupled with the positive electrode of the battery unit and the positive electrode output end of the power supply interface; the battery negative electrode connecting end is coupled with the negative electrode of the battery unit and is coupled with a connecting end of the plurality of branches through the branch switch unit and the current detection unit; the common terminal is coupled to the negative output terminal and grounded;

the branch switch unit includes: a switching element and a diode element; the switching element includes: the current detection unit is respectively coupled to the negative end of the battery and two ends of the current detection unit, and the control end is used for controlling the connection or disconnection of the two ends; the diode element and the switch element are connected in parallel at the two ends, and the conduction direction of the diode element points to the negative electrode connecting end of the battery; wherein the diode turns on a first conductive path forming the branch circuit under a forward bias voltage when the branch circuit switching unit is turned off, or turns off to turn off the first conductive path under a reverse bias voltage generated by a voltage difference between the batteries; forming a second conductive path instead of the first conductive path when the branch switch unit is turned on;

the current detection unit is used for detecting the current in the branch circuit to generate a first output signal;

the control unit is coupled with the current detection unit in each branch circuit to obtain the current value of the current in each branch circuit according to each first output signal, and is coupled with the control end of the branch circuit switch unit in each branch circuit through a switch control driving circuit; the control unit is used for responding to the fact that the current value in one branch circuit reaches a first current threshold value, and outputting a first driving signal for enabling the corresponding branch circuit switch unit to be conducted; or, in response to the current value in one branch circuit decreasing below at least one second current threshold, outputting a second driving signal for turning off the corresponding branch circuit switching unit.

2. The battery management circuit of claim 1, wherein the branch switch unit comprises a first NMOS, a source of the first NMOS is coupled to the current detection unit, and a drain of the first NMOS is coupled to the battery negative connection terminal; the diode element is a parasitic diode of the first NMOS.

3. The battery management circuit of claim 1, further comprising:

a main circuit switch unit coupled in the main circuit between the common terminal and the negative output terminal and coupled to the control unit to be controlled to be conducted when the control unit is started;

wherein the main circuit switching unit includes a soft start circuit for it to be turned on or off slowly.

4. The battery management circuit of claim 3, wherein the main circuit switch unit comprises a second NMOS having a source coupled to the common terminal, a drain coupled to the negative output terminal, and a gate coupled to a soft start driving circuit controlled by the control unit, wherein the soft start driving circuit changes the driving voltage for turning on or off the main circuit switch unit according to the driving signal of the control unit.

5. The battery management circuit of claim 4, wherein the soft start drive circuit further comprises: and the capacitor or the combination of the capacitor and the resistor is coupled between the grid and the drain of the second NMOS.

6. The battery management circuit of claim 1, further comprising: a plurality of switch control drive circuits; each switch control driving circuit is coupled between the control unit and the control end of the branch switching unit in a branch, and is configured to output a corresponding first driving voltage or second driving voltage to the control end of the branch switching unit according to the received first driving signal or second driving signal.

7. The battery management circuit of claim 1, further comprising: a plurality of voltage detection modules; each voltage detection module is coupled between a reference point in a branch and the control unit and is used for detecting the voltage of the reference point to generate a second output signal; and the control unit is used for obtaining the voltage values of the reference points in the branches according to the second output signals, comparing the voltage difference between the voltage values obtained by at least two branches, and taking the voltage difference lower than a preset voltage threshold value as a reference condition for turning on the branch switch unit in one of the branches to be turned on.

8. The battery management circuit of claim 1, wherein the battery interface is hot-pluggable coupled to the battery cell.

9. A battery management system, comprising:

a battery management circuit according to any of claims 1 to 8.

10. An electric vehicle, comprising: the battery management system of claim 9.