A battery pack integrated circuit and control method

Abstract

The present disclosure proposes a battery pack integrated circuit and control method, including: a buck-boost converter and a digital controller, the digital controller is composed of multiple integrated circuit controllers; the buck-boost converter, the integrated circuit controller and the lithium-ion battery cells are connected one-to-one, and the digital controller determines the operation mode of the lithium-ion battery cell according to the voltage and current signal values ​​of the lithium-ion battery cell when it is working, and maintains the normal working state of the entire battery pack in each operation mode. The battery pack of the present invention can cut off the corresponding main circuit through a relay when any battery cell fails, allowing the other two battery cells to continue to work to achieve stable power supply of the DC bus.

Description

Technical Field

[0001] The present disclosure belongs to the field of battery control technology, and in particular, relates to a battery pack integrated circuit and a control method. Background Art

[0002] Power battery packs have become an important obstacle to the development of portable power equipment. Power battery packs are generally composed of multiple lithium-ion battery cells connected in series to obtain a sufficiently high voltage level to drive the motor. Although this method is simple enough and the cost is the lowest among many methods, when a lithium-ion battery cell fails, the entire power battery pack will not be able to work normally. In addition, due to the inconsistency of internal parameters, self-discharge rate and other parameters of each lithium-ion battery cell in series, the output voltage of the lithium-ion battery cells is inconsistent and the stored energy is also different. Therefore, during the charging process of the power battery pack, some lithium-ion battery cells may not be fully charged, while some lithium-ion battery cells are overcharged, resulting in a reduction in battery life; during the discharge process of the power battery pack, some lithium-ion battery cells may still have energy, while some lithium-ion battery cells are fully discharged, resulting in the entire power battery pack being unable to work before it is fully discharged.

[0003] In order to solve the voltage equalization problem during charging and discharging of portable battery packs, the commonly used methods currently include passive voltage equalization and active voltage equalization.

[0004] The passive voltage balancing method connects an energy-consuming resistor in parallel to each lithium-ion battery cell and determines the connection and disconnection of the energy-consuming resistor by detecting the voltage of the battery. This method is effective and low-cost, but for the entire system, its efficiency is low and the thermal stress caused to the system is also large.

[0005] Active voltage balancing methods often use special power electronic circuits to achieve voltage balance between each unit, such as the switched capacitor method, the switched inductor method, the energy feedback method, etc. However, these methods are all based on the series structure of lithium-ion battery cells. Once any lithium-ion battery cell fails, the entire battery pack will still not work properly. Summary of the invention

[0006] To overcome the above-mentioned deficiencies of the prior art, the present disclosure provides a battery pack integrated circuit, which solves the problem of charge and discharge voltage balance of lithium-ion battery cells and the normal operation of the battery pack when any lithium-ion battery cell fails.

[0007] To achieve the above objectives, one or more embodiments of the present disclosure provide the following technical solutions:

[0008] In a first aspect, a battery pack integrated circuit is disclosed, comprising:

[0009] a plurality of integrated circuits, each integrated circuit comprising a battery cell, a buck-boost converter, and a battery cell integrated circuit controller;

[0010] The buck-boost converter, integrated circuit controller and lithium-ion battery cells are connected one-to-one. The integrated circuit controller determines the operating mode of the lithium-ion battery cell according to the voltage and current signal values ​​of the lithium-ion battery cell when the lithium-ion battery cell is working, and maintains the normal working state of the entire battery pack in each operating mode.

[0011] According to a further technical solution, the buck-boost converters are connected in sequence, with the positive electrode of the buck-boost converter at the head end serving as the positive electrode of the battery pack integrated circuit, and the negative electrode of the buck-boost converter at the end serving as the negative electrode of the battery pack integrated circuit.

[0012] In a further technical solution, the integrated circuit controller controls the action of the relay in the buck-boost converter to change whether the lithium-ion battery cell participates in charging, discharging or is cut off from the operating circuit.

[0013] Further preferably, each integrated circuit controller determines whether the buck-boost converter operates in a charging or discharging operation mode by controlling a signal switch.

[0014] Further preferably, each battery cell integrated circuit controller includes a charging control dual closed-loop module and a discharging control dual closed-loop module, and determines whether to use the charging or discharging control dual closed-loop module to participate in the control according to the fault / mode identifier.

[0015] According to a further technical solution, the integrated circuit controller includes a reference voltage generator, which adjusts the output signal according to the working state of the lithium-ion battery cell to ensure that the voltage between the positive electrode and the negative electrode of the entire battery pack remains constant.

[0016] In a second aspect, a battery pack integrated circuit control method is disclosed, comprising:

[0017] The operating mode of the lithium-ion battery cell is determined according to the voltage and current signal values ​​of the lithium-ion battery cell when it is working. In each operating mode, the action of the relay in the buck-boost converter is controlled to change whether the lithium-ion battery cell participates in charging, discharging or is cut off from the operating circuit to maintain the normal working state of the entire battery pack.

[0018] A further technical solution is that the operating modes of the lithium-ion battery cells include a charging mode, a fault mode and a discharging mode. When one of the battery cells fails in the charging mode, the relay contacts corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cells are charged through the buck-boost converter; in the main circuit corresponding to the faulty battery cell, the relay contacts are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

[0019] A further technical solution is that when one of the battery cells fails in the discharge mode, the relay contacts corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cells are discharged through the buck-boost converter; in the main circuit corresponding to the faulty battery cell, the relay contacts are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

[0020] In a second aspect, a battery pack is disclosed, including the above-mentioned battery pack integrated circuit.

[0021] One or more of the above technical solutions have the following beneficial effects:

[0022] In the technical solution disclosed in the present invention, each lithium-ion battery cell is not directly connected in series, which can effectively avoid the voltage unevenness phenomenon in the traditional battery pack structure; when any lithium-ion battery cell fails, the operation of the failed cell can be cut off, thereby achieving safe and reliable operation of the power battery pack.

[0023] Compared with a traditional battery pack formed by connecting battery cells in series, the battery pack of the present invention can, in the event of a failure of any battery cell, cut off the corresponding main circuit through a relay, allowing the other two battery cells to continue working to achieve stable power supply of the DC bus.

[0024] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure.

[0026] Figure 1 This is a structural diagram of an electric vehicle integrated power battery pack structure and a control device based on a flyback converter disclosed in the present invention;

[0027] Figure 2 The main circuit equivalent circuit of the lithium-ion battery unit operating in the charging mode;

[0028] Figure 3 The main circuit equivalent circuit of the lithium-ion battery unit operating in the discharge mode;

[0029] Figure 4 The main circuit equivalent circuit of the lithium-ion battery unit operating in the fault mode;

[0030] Figure 5 It is an equivalent circuit of the main circuit of the entire battery pack when a second battery cell fails in the integrated power battery pack composed of lithium-ion battery cells disclosed in the present invention;

[0031] Figure 6 The main circuit equivalent circuit of the battery pack in the discharge mode when the second battery unit disclosed in the present invention fails;

[0032] Figure 7 A schematic diagram of the charging mode + fault mode operating state disclosed in the present invention;

[0033] Figure 8 A schematic diagram of the discharge mode + fault mode operating state disclosed in the present invention;

[0034] Symbol name in the figure: U bus ——Battery pack bus voltage; C i1 ——The i-th (i=1, 2, 3) input side capacitor; C i2 ——The i-th (i=1, 2, 3) output side capacitor; K i ——The i-th (i=1, 2, 3) relay; S i1 ——The i1th (i=1, 2, 3) switch tube; S i2 ——The i2th (i=1, 2, 3) switch tube; L i ——i (i=1, 2, 3) inductance; B i ——The i-th (i=1, 2, 3) lithium-ion battery cell; U nir ——The reference value of the input voltage of the ith (i=1, 2, 3) step-up / step-down converter; U nif ——the voltage value at the input side of the i-th (i=1, 2, 3) step-up / step-down converter; U nie ——The voltage error value at the input side of the i-th (i=1, 2, 3) step-up / step-down converter; I fir ——the discharge current reference value of the i-th (i=1, 2, 3) lithium-ion battery cell; I fif ——The discharge current value of the i-th (i=1, 2, 3) lithium-ion battery cell; I fie ——The discharge current error value of the i-th (i=1, 2, 3) lithium-ion battery cell; u ri1 ——Modulation signal of the discharge mode of the i-th (i=1, 2, 3) lithium-ion battery cell; U Bif ——The voltage value of the i-th (i=1, 2, 3) lithium-ion battery cell; U Bir ——the voltage reference value of the ith (i=1, 2, 3) lithium-ion battery cell; U Bie ——The voltage error value of the i-th (i=1, 2, 3) lithium-ion battery cell; I cir ——Charging current reference value of the i-th (i=1, 2, 3) lithium-ion battery unit; I cif ——Charging current value of the i-th (i=1, 2, 3) lithium-ion battery cell; I cie——Charging current error value of the i-th (i=1, 2, 3) lithium-ion battery cell; u ri2 ——Modulation signal of charging mode of the i-th (i=1, 2, 3) lithium-ion battery cell; u ri ——The modulation signal of the i-th (i=1, 2, 3) buck-boost converter; u Si1 ——The i1th (i=1, 2, 3) switch tube driving signal; u Si2 ——The i2th (i=1, 2, 3) switch tube drive signal; u K1 ——Select switch drive signal; u Gi ——The i-th (i=1, 2, 3) relay drive signal; u Ki ——The i-th (i=1, 2, 3) selection switch driving signal. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present disclosure belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] In the absence of conflict, the embodiments in the present disclosure and the features in the embodiments may be combined with each other.

[0038] Embodiment 1

[0039] This embodiment discloses a battery pack integrated circuit, such as Figure 1As shown, it comprises a digital controller consisting of 3 buck-boost converters, 6 voltage sensors, 3 current sensors, and 3 lithium-ion battery cell integrated circuit controllers; the negative electrode of the first buck-boost converter is connected to the positive electrode of the second buck-boost converter, the negative electrode of the second buck-boost converter is connected to the positive electrode of the third buck-boost converter, the positive electrode of the first buck-boost converter serves as the positive electrode of the battery pack integrated circuit, and the negative electrode of the third buck-boost converter serves as the negative electrode of the battery pack integrated circuit; the internal structures of the three buck-boost converters are the same; the i-th (i=1, 2, 3) buck-boost converter is connected to the i-th The i(i=1,2,3)th input side capacitor, the i(i=1,2,3)th relay, the i1(i=1,2,3)th switch tube, the i2(i=1,2,3)th switch tube, the i(i=1,2,3)th inductor and the i(i=1,2,3)th output side capacitor are formed; the positive electrode of the i(i=1,2,3)th input side capacitor, the third terminal of the i(i=1,2,3)th relay and the drain of the i1(i=1,2,3)th switch tube are connected together and serve as the positive electrode of the i(i=1,2,3)th step-up / step-down converter; the i(i=1,2,3)th input side capacitor The negative electrode of the ith (i=1, 2, 3) relay and the first terminal are connected together and serve as the negative electrode of the ith (i=1, 2, 3) buck-boost converter; the source electrode of the ith (i=1, 2, 3) switch tube, the drain electrode of the ith (i=1, 2, 3) switch tube, and one end of the ith (i=1, 2, 3) inductor are connected together; the second terminal of the ith (i=1, 2, 3) relay, the source electrode of the ith (i=1, 2, 3) switch tube, the negative electrode of the ith (i=1, 2, 3) output side capacitor, and the negative electrode of the ith (i=1, 2, 3) lithium-ion battery unit are connected together; The other end of the i (i=1, 2, 3)th inductor, the positive electrode of the i (i=1, 2, 3)th output capacitor, and the positive electrode of the i (i=1, 2, 3)th lithium-ion battery unit are connected together; the two input ends of the i1 (i=1, 2, 3)th voltage sensor are respectively connected to the positive electrode and the negative electrode of the i (i=1, 2, 3)th step-up / step-down converter; the two input ends of the i2 (i=1, 2, 3)th voltage sensor are respectively connected to the positive electrode and the negative electrode of the i (i=1, 2, 3)th lithium-ion battery unit; the input end of the i (i=1, 2, 3)th current sensor is connected in series with the lithium-ion battery unit.

[0040] In the digital controller, the internal structures of the three lithium-ion battery cell integrated circuit controllers are consistent; the i-th (i=1, 2, 3) lithium-ion battery cell integrated circuit controller includes a reference voltage generator, four subtractors, an input voltage regulator, a battery discharge current regulator, a fault / mode identifier, a cell voltage regulator, a battery charge current regulator, an inverter, a selection switch, and a signal conditioner; the two input ends of the i-th (i=1, 2, 3) fault / mode identifier are respectively connected to the output end of the i-th (i=1, 2, 3) current sensor and the output end of the i2-th (i=1, 2, 3) voltage sensor ...2-th (i=1, 2, 3) current sensor and the output end of the i3-th (i=1, 2, 3) voltage sensor; the two input ends of the i3-th (i=1, 2, 3) fault / mode identifier are respectively connected to the output end of the i3-th (i=1, 2, 3) fault / mode identifier. The output terminal signal is respectively used as the fault signal of the i-th (i=1, 2, 3) lithium-ion battery cell and the driving signal of the i-th (i=1, 2, 3) selection switch; the positive input terminal, negative input terminal and output terminal of the i1-th (i=1, 2, 3) subtractor are respectively connected to the output terminal of the i-th (i=1, 2, 3) reference voltage generator, the output terminal of the i1-th (i=1, 2, 3) voltage sensor, and the input terminal of the i-th (i=1, 2, 3) input voltage regulator; the input terminal of the i-th (i=1, 2, 3) inverter is connected to the output terminal of the i-th (i=1, 2, 3) current sensor; the positive input terminal, negative input terminal and output terminal of the i2-th (i=1, 2, 3) subtractor are respectively connected to the output terminal of the i-th (i=1, 2, 3) reference voltage generator, the output terminal of the i1-th (i=1, 2, 3) voltage sensor, and the input terminal of the i-th (i=1, 2, 3) input voltage regulator. The positive input terminal, negative input terminal and output terminal of the i3 (i=1,2,3)th subtractor are respectively connected to the output terminal of the i (i=1,2,3)th input voltage regulator, the output terminal of the i (i=1,2,3)th inverter, and the input terminal of the i (i=1,2,3)th battery discharge current regulator; the positive input terminal, negative input terminal and output terminal of the i4 (i=1,2,3)th subtractor are respectively connected to the reference value of the i (i=1,2,3)th lithium-ion battery cell voltage, the output terminal of the i2 (i=1,2,3)th voltage sensor, and the input terminal of the i (i=1,2,3)th cell voltage regulator; the positive input terminal, negative input terminal and output terminal of the i5 (i=1,2,3)th subtractor are respectively connected to the reference value of the i (i=1,2,3)th lithium-ion battery cell voltage, the output terminal of the i6 (i=1,2,3)th voltage sensor, and the input terminal of the i7 (i=1,2,3)th cell voltage regulator The first terminal, the second terminal and the third terminal of the i (i = 1, 2, 3) selection switch are respectively connected to the output end of the i (i = 1, 2, 3) battery discharge current regulator, the output end of the i (i = 1, 2, 3) battery charging current regulator and the input end of the i (i = 1, 2, 3) signal conditioner; the two output end signals of the i (i = 1, 2, 3) signal conditioner are respectively used as the driving signal of the i1 (i = 1, 2, 3) switch tube and the driving signal of the i2 (i = 1, 2, 3) switch tube.

[0041] In the i-th (i=1, 2, 3) fault / mode identifier, it is determined whether the lithium-ion battery cell is operating in a charging mode, a discharging mode or a fault mode according to the voltage and current signal values ​​of the i-th (i=1, 2, 3) lithium-ion battery cell; the two output terminal signals of the i-th (i=1, 2, 3) fault / mode identifier are u Gi (i=1, 2, 3), u KI (I = A, B, C), the two signals control the on and off of the i-th (i = 1, 2, 3) relay and the on and off of the i-th (i = 1, 2, 3) selection switch respectively; when the battery pack is running in charging mode, u Gi =0(i=1,2,3),u KI =-1 (I = A, B, C), the first terminal and the second terminal of the i-th (i = 1, 2, 3) relay are connected together, and the second terminal and the third terminal of the i-th (i = 1, 2, 3) selection switch are connected together. The corresponding buck-boost converter equivalent circuit is as follows: Figure 2 shown.

[0042] When the battery pack is running in discharge mode, u Gi =0(i=1,2,3),u KI =1 (I = A, B, C), the first terminal and the second terminal of the i-th (i = 1, 2, 3) relay are connected together, and the first terminal and the third terminal of the i-th (i = 1, 2, 3) selection switch are connected together. The corresponding buck-boost converter equivalent circuit is as follows: Figure 3 shown.

[0043] When the i-th (i=1, 2, 3) lithium-ion battery unit fails, u Gi =1(i=1,2,3),u KI =0 (I = A, B, C), the first terminal and the third terminal of the i-th (i = 1, 2, 3) relay are connected together, and the third terminal of the i-th (i = 1, 2, 3) selection switch is suspended, so that the switch tubes in the corresponding i-th (i = 1, 2, 3) buck-boost converter are all in the cut-off state. The corresponding buck-boost converter equivalent circuit is as follows: Figure 4 shown.

[0044] The working principle of the i-th (i=1, 2, 3) reference voltage generator is as follows: if the three lithium-ion battery cells are all working normally, the output signal of the i-th (i=1, 2, 3) reference voltage generator is unit 1; if one of the three lithium-ion battery cells fails, the output signal of the i-th (i=1, 2, 3) reference voltage generator is unit 1.5, thereby ensuring that when a lithium-ion battery cell fails, the voltage between the positive and negative electrodes of the entire battery pack remains constant, ensuring that the battery pack can work normally. The above-mentioned reference voltage output signal is unit 1 or unit 1.5, which refers to 1 times and 1.5 times a certain value. For example, when the bus voltage is 18V during normal operation, when the three lithium-ion battery cells are all normal, the reference voltage output signal is 6; if one battery cell fails, the output signal of the reference voltage generator corresponding to the two non-faulty battery cells is 1.5 times 6, that is, 9.

[0045] When the second battery cell in the battery pack fails, the main circuit equivalent circuit of the battery pack in the charging mode is as follows Figure 5 As shown, the second relay isolates the second lithium-ion battery unit from the DC bus, so that the second buck-boost converter does not participate in the operation, and the DC bus voltage is changed from being evenly distributed among three buck-boost converters to being evenly distributed among two buck-boost converters. Finally, the operating duty cycle of the i1th (i=1, 2, 3) switch tube becomes smaller than that in normal operation.

[0046] When the second battery cell in the battery pack fails, the main circuit equivalent circuit of the battery pack in the discharge mode is as follows Figure 6 As shown, the second relay isolates the second lithium-ion battery cell from the DC bus, so that the second buck-boost converter does not participate in the operation. At this time, the output signals of the first and third reference voltage generators become 1.5 times that of normal operation, so that the battery pack bus voltage when the two lithium-ion battery cells are operating is equal to the bus voltage when the three lithium-ion battery cells are normal.

[0047] The lithium-ion battery cells are respectively connected to the output ends of the buck-boost converter, thereby avoiding the problem of the battery pack not being able to work normally due to the failure of any lithium-ion battery cell in the traditional battery pack; in addition, since the buck-boost converter can charge and discharge the lithium-ion battery cells individually, the integrated circuit proposed in the present invention no longer needs a special voltage balancing device between the lithium-ion battery cells, thereby simplifying the system.

[0048] Embodiment 2

[0049] The purpose of this embodiment is to provide a control method for a battery pack integrated circuit, including:

[0050] The operating mode of the lithium-ion battery cell is determined according to the voltage and current signal values ​​of the lithium-ion battery cell when it is working. In each operating mode, the action of the relay in the buck-boost converter is controlled to change whether the lithium-ion battery cell participates in charging, discharging or is cut off from the operating circuit to maintain the normal working state of the entire battery pack.

[0051] The operating modes of the lithium-ion battery cells include charging mode, fault mode and discharging mode. When one of the battery cells fails in the charging mode, the relay contacts corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cells are charged through the buck-boost converter; in the main circuit corresponding to the faulty battery cell, the relay contacts are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

[0052] When one of the battery cells fails in the discharge mode, the relay contacts corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cells are discharged through the buck-boost converter; in the main circuit corresponding to the faulty battery cell, the relay contacts are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

[0053] In a more specific implementation example, the battery pack is composed of three integrated circuits, each of which includes a battery cell, a buck-boost converter, and a battery cell integrated circuit controller. Each controller controls the action of the relay Ki (i=1, 2, 3) in the buck-boost converter to change whether the battery cell participates in charging, discharging, or is cut off from the operating circuit; each controller determines whether the buck-boost converter operates in the charging or discharging operation mode by controlling the signal switches KA, KB, and KC; each battery cell integrated circuit controller includes a set of charging control double closed loops and a set of discharging control double closed loops, and a fault / mode identifier determines whether to use the charging or discharging control double closed loop for control.

[0054] See attached Figure 7 As shown, in charging mode + fault mode, the connection status of the three battery cell integrated circuits is as shown in the figure below. At this time, battery cell 2 fails, then the contacts 1 and 2 of relay K1 and relay K3 are closed, and battery cell 1 and battery cell 3 are charged through the buck-boost converter (where Si2 (i=1,2,3) is not controlled, and only the corresponding body diode works); in the main circuit corresponding to battery cell 2, the contacts 1 and 3 of relay K2 are closed, the corresponding buck-boost converter stops working, and battery cell 2 does not work.

[0055] See attached Figure 8As shown, in discharge mode + fault mode, the connection status of the three battery cell integrated circuits is as shown in the figure below. At this time, battery cell 2 fails, then the 1 and 2 contacts of relay K1 and relay K3 are closed, and battery cell 1 and battery cell 3 are discharged through the buck-boost converter (where Si1 (i=1,2,3) is not controlled, and only the corresponding body diode works); in the main circuit corresponding to battery cell 2, the 1 and 3 contacts of relay K2 are closed, the corresponding buck-boost converter stops working, and battery cell 2 does not work.

[0056] Embodiment 3

[0057] The purpose of this embodiment is to provide a battery pack, including the above-mentioned battery pack integrated circuit.

[0058] Those skilled in the art should understand that the modules or steps of the present disclosure can be implemented by a general computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present disclosure is not limited to any specific combination of hardware and software.

[0059] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A battery pack integrated circuit, characterized in that: include: The invention is composed of a digital controller consisting of 3 buck-boost converters, 6 voltage sensors, 3 current sensors, and 3 lithium-ion battery cell integrated circuit controllers; the negative electrode of the first buck-boost converter is connected to the positive electrode of the second buck-boost converter, the negative electrode of the second buck-boost converter is connected to the positive electrode of the third buck-boost converter, the positive electrode of the first buck-boost converter serves as the positive electrode of the battery pack integrated circuit, and the negative electrode of the third buck-boost converter serves as the negative electrode of the battery pack integrated circuit; the internal structures of the three buck-boost converters are consistent; the i-th buck-boost converter is composed of the i-th input side capacitor, the i-th relay, the i1-th switch tube, the i2-th switch tube, the i-th inductor, and the i-th output side capacitor; the positive electrode of the i-th input side capacitor, the third terminal of the i-th relay, and the drain of the i1-th switch tube are connected together and serve as the positive electrode of the i-th buck-boost converter; the negative electrode of the i-th input side capacitor and the first terminal of the i-th relay are connected together and serve as the negative electrode of the i-th buck-boost converter. The source of the i1th switch tube, the drain of the i2th switch tube, and one end of the i-th inductor are connected together; the second terminal of the i-th relay, the source of the i2th switch tube, the negative electrode of the i-th output side capacitor, and the negative electrode of the i-th lithium-ion battery unit are connected together; the other end of the i-th inductor, the positive electrode of the i-th output capacitor, and the positive electrode of the i-th lithium-ion battery unit are connected together; the two input ends of the i1th voltage sensor are respectively connected to the positive electrode and the negative electrode of the i-th step-up and step-down converter; the two input ends of the i2th voltage sensor are respectively connected to the positive electrode and the negative electrode of the i-th lithium-ion battery unit; the input end of the i-th current sensor is connected in series with the lithium-ion battery unit; the battery unit integrated circuit controller includes a charging control double closed-loop module and a discharging control double closed-loop module, and the charging or discharging control double closed-loop module is determined to participate in the control according to the pattern recognizer; the two input ends of the pattern recognizer are respectively connected to the output end of the i-th current sensor and the output end of the i2nd voltage sensor; The buck-boost converter, the battery cell integrated circuit controller and the lithium-ion battery cells are connected one by one, and the battery cell integrated circuit controller includes a reference voltage generator; the reference voltage generator adjusts the output signal according to the working state of the lithium-ion battery cell to ensure that the voltage between the positive electrode and the negative electrode of the entire battery pack is maintained constant; the working principle of the i-th reference voltage generator is: when the three lithium-ion battery cells are all working normally, the output signal of each reference voltage generator is a normal reference voltage; when one of the three lithium-ion battery cells fails, the output signals of the remaining two reference voltage generators are 1.5 times the normal reference voltage; The battery cell integrated circuit controller determines the operation mode of the lithium-ion battery cell according to the voltage and current signal values ​​of the lithium-ion battery cell when it is working, and maintains the normal working state of the entire battery pack in each operation mode; the battery cell integrated circuit controller controls the action of the relay in the buck-boost converter to change whether the lithium-ion battery cell participates in charging, discharging or is cut off from the operation circuit, specifically: The operation modes of the lithium-ion battery cells include a charging mode, a fault mode and a discharging mode. When one of the battery cells fails in the charging mode, the first and second terminals of the relay corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cells are charged via a buck-boost converter; in the main circuit corresponding to the faulty battery cell, the first and third terminals of the relay are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work; when one of the battery cells fails in the discharging mode, the first and second terminals of the relay corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cell is discharged via a buck-boost converter; in the main circuit corresponding to the faulty battery cell, the first and third terminals of the relay are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

2. A battery pack integrated circuit as claimed in claim 1, characterized in that: Each battery cell integrated circuit controller determines whether the buck-boost converter operates in charging or discharging operation mode by controlling the signal switch.

3. A control method for a battery pack integrated circuit, characterized in that: The battery pack integrated circuit as claimed in any one of claims 1 to 2 comprises: using a reference voltage generator, the reference voltage generator adjusting the output signal according to the working state of the lithium-ion battery cell to ensure that the voltage between the positive electrode and the negative electrode of the entire battery pack is maintained constant; The operating mode of the lithium-ion battery cell is determined according to the voltage and current signal values ​​of the lithium-ion battery cell when it is working. In each operating mode, the action of the relay in the buck-boost converter is controlled to change whether the lithium-ion battery cell participates in charging, discharging or is cut off from the operating circuit to maintain the normal working state of the entire battery pack.

4. The battery pack integrated circuit control method according to claim 3, characterized in that: The operation modes of the lithium-ion battery cells include a charging mode, a fault mode and a discharging mode. When a fault occurs in one of the battery cells in the charging mode, the first and second terminals of the relays corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cells are charged via a buck-boost converter; in the main circuit corresponding to the faulty battery cell, the first and third terminals of the relays are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

5. The battery pack integrated circuit control method as claimed in claim 3, characterized in that the discharge When one of the battery cells fails in this mode, the first and second terminals of the relay corresponding to the non-faulty battery cells other than the faulty battery cell are closed, and the non-faulty battery cell is discharged through the buck-boost converter; in the main circuit corresponding to the faulty battery cell, the first and third terminals of the relay are closed, the corresponding buck-boost converter stops working, and the faulty battery cell does not work.

6. A battery pack, characterized in that: A battery pack integrated circuit comprising any one of claims 1-2 above.

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