Battery cell integrated circuit, power battery pack, electric vehicle and method

Abstract

The present disclosure proposes a battery cell integrated circuit, a power battery pack, an electric vehicle and a method. The battery cell integrated circuit includes: a bidirectional flyback converter, a detection unit and a digital controller; the bidirectional flyback converter is connected to a battery cell; the detection unit detects the voltage data of the bidirectional flyback converter and the voltage and current data of the battery cell respectively and transmits them to the digital controller; the digital controller determines the operating mode of the battery cell integrated circuit according to the received voltage, current and operating mode external signals, and operates in charging mode, discharging mode, fault mode or bypass mode.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of power electronic converters, and in particular relates to a battery cell integrated circuit, a power battery pack, an electric vehicle and a method. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] In recent years, electric vehicles have developed rapidly, but power battery packs have become an important obstacle to the development of electric vehicles. Power battery packs are generally composed of many battery cells connected in series and in parallel to obtain a sufficiently high voltage level and a sufficiently large output current. Although this method is simple enough and the cost is the lowest among many methods, when a battery cell fails, the entire power battery pack cannot work normally. In addition, due to the inconsistency of internal parameters, self-discharge rate and other parameters of each battery cell in series, the output voltage of the battery cells is inconsistent and the stored energy is also different. Therefore, during the charging process of the power battery pack, some battery cells may not be fully charged, while some battery cells are overcharged, resulting in a reduction in battery life; during the discharge process of the power battery pack, some battery cells may still have energy, while some battery cells are fully discharged, resulting in the entire power battery pack not being able to work before it is fully discharged.

[0004] In order to solve the voltage equalization problem during charging and discharging of automotive power battery packs, the commonly used methods currently include passive voltage equalization and active voltage equalization.

[0005] The passive voltage balancing method connects an energy-consuming resistor in parallel to each 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.

[0006] 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 battery cells. Once any battery cell fails, the entire battery pack will still not work properly.

[0007] The power battery pack of an electric vehicle is composed of multiple battery cells connected in series. During the repeated charging and discharging process, some battery cells will be overcharged or over-discharged, which greatly limits the life of the power battery pack. In addition, when any battery cell fails, the power battery pack cannot operate normally.

[0008] Therefore, there is a voltage unevenness phenomenon in the traditional battery pack structure. When any battery cell fails, the operation of the failed cell cannot be cut off in time, and the safe and reliable operation of the power battery pack cannot be achieved. Summary of the invention

[0009] In order to overcome the deficiencies of the above-mentioned prior art, the present disclosure provides a battery cell integrated circuit, a battery pack, an electric vehicle and a method. Each battery cell is not directly connected in series, which can effectively avoid the voltage unevenness phenomenon in the traditional battery pack structure; when any battery cell fails, the operation of the faulty cell can be cut off, thereby achieving safe and reliable operation of the power battery pack.

[0010] To achieve the above objectives, one or more embodiments of the present disclosure provide the following technical solutions:

[0011] In a first aspect, a battery cell integrated circuit is disclosed, comprising: a bidirectional flyback converter, a detection unit and a digital controller;

[0012] The bidirectional flyback converter is connected to a battery cell;

[0013] The detection unit detects the voltage data of the bidirectional flyback converter and the voltage and current data of the battery cell respectively and transmits them to the digital controller;

[0014] The digital controller determines the operation mode of the battery cell integrated circuit according to the received voltage, current and operation mode external signal, and operates in a charging mode, a discharging mode, a fault mode or a bypass mode.

[0015] According to a further technical solution, the bidirectional flyback converter comprises an input side capacitor, a first relay, a first switch tube, a transformer, and a second relay;

[0016] The positive electrode of the input side capacitor, the first terminal of the first relay, the first terminal of the second relay, and the same-name end of the primary winding of the transformer are connected together and serve as the positive electrode of the battery cell integrated circuit;

[0017] The negative electrode of the input side capacitor, the second terminal of the first relay, the third terminal of the second relay, and the source electrode of the first switch tube are connected together and serve as the negative electrode of the battery cell integrated circuit;

[0018] The drain of the first switch tube is connected to the opposite end of the primary winding of the transformer.

[0019] According to a further technical solution, the bidirectional flyback converter further includes: a second switch tube and an output side capacitor;

[0020] The opposite-name end of the secondary winding of the transformer is connected to the source of the second switch tube;

[0021] The drain of the second switch tube, the second terminal of the second relay, the positive electrode of the output side capacitor, and the positive electrode of the battery unit are connected together;

[0022] The same-name end of the secondary winding of the transformer, the fourth terminal of the second relay, the negative electrode of the output side capacitor, and the negative electrode of the battery unit are connected together.

[0023] In a further technical solution, the first relay includes a set of normally open contacts, and the second relay includes two sets of normally open contacts;

[0024] According to a further technical solution, the detection unit includes: a first voltage sensor, a second voltage sensor and a current sensor;

[0025] The first input terminal and the second input terminal of the first voltage sensor are respectively connected to the positive electrode of the battery cell integrated circuit and the negative electrode of the battery cell integrated circuit;

[0026] The first input terminal and the second input terminal of the second voltage sensor are connected to the positive electrode of the battery cell and the negative electrode of the battery cell respectively;

[0027] The input terminal of the current sensor is connected in series with the battery unit.

[0028] According to a further technical solution, the digital controller includes a battery discharge controller, a battery charge controller, a selection switch, a signal conditioner, and an operation mode identifier;

[0029] In a second aspect, a control method of a battery cell integrated circuit is disclosed, comprising:

[0030] The operating mode of the battery cell integrated circuit is determined by the battery cell voltage, battery current and external operating mode signal. There are four operating modes in total, namely discharge mode, charge mode, fault mode and bypass mode.

[0031] A further technical solution is that in the charging mode, the signal output by the battery charging controller is used as the input signal of the signal conditioner, one group of normally open contacts of the first relay is disconnected, two groups of normally open contacts of the second relay are disconnected, the second switch tube is in the off state, and the first switch tube operates at high frequency for charging.

[0032] A further technical solution is that in the discharge mode, the signal output by the battery discharge controller is used as the input signal of the signal conditioner, one group of normally open contacts of the first relay is disconnected, two groups of normally open contacts of the second relay are disconnected, the second switch tube operates at a high frequency, and the first switch tube is in the off state.

[0033] A further technical solution is that in the fault mode, one group of normally open contacts of the first relay is closed, and two groups of normally open contacts of the second relay are disconnected, the battery discharge controller and the battery charge controller do not work, and the first switch tube and the second switch tube are both in the cut-off state.

[0034] According to a further technical solution, in the bypass mode, one group of normally open contacts of the first relay is disconnected, and two groups of normally open contacts of the second relay are closed. The battery discharge controller and the battery charge controller do not work, and the first switch tube and the second switch tube are both in the cut-off state.

[0035] On the third aspect, a power battery pack is disclosed, which is composed of n of the above-mentioned battery cell integrated circuits, the positive electrode of the i-th battery cell integrated circuit is connected to the negative electrode of the i+1-th battery cell integrated circuit, the negative electrode of the 1st battery cell integrated circuit serves as the negative electrode of the electric vehicle integrated power battery pack, and the positive electrode of the n-th battery cell integrated circuit serves as the positive electrode of the electric vehicle integrated power battery pack, i=1, 2,…, n-1.

[0036] In a fourth aspect, an electric vehicle is disclosed, wherein the electric vehicle is powered by the power battery pack described above.

[0037] One or more of the above technical solutions have the following beneficial effects:

[0038] With the power battery pack and its control strategy disclosed in the technical solution of the present invention, there is no direct connection between the battery cells. Through the four operating modes of the bidirectional flyback converter, the integrated power battery pack can be guaranteed to operate normally under any conditions, thereby avoiding the voltage equalization problem of the battery cells in the traditional series battery pack and the problem of the battery pack failing to operate due to the failure of any battery cell.

[0039] The technical solution disclosed in the present invention integrates a bidirectional flyback converter before each battery cell. The bidirectional flyback converter can enable the battery cell to operate in charging mode, discharging mode, fault mode and bypass mode, thereby solving the problem of charging and discharging voltage balance of the battery cell and the normal operation of the battery pack when any battery cell fails.

[0040] 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

[0041] 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.

[0042] 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;

[0043] Figure 2 It is a schematic diagram of the equivalent circuit of the main circuit of the battery unit operating in the charging mode;

[0044] Figure 3It is a schematic diagram of the equivalent circuit of the main circuit of the battery unit operating in the discharge mode;

[0045] Figure 4 It is a schematic diagram of the equivalent circuit of the main circuit of the battery unit operating in the fault mode;

[0046] Figure 5 The schematic diagram of the equivalent circuit of the main circuit of the battery unit operating in the bypass mode;

[0047] Figure 6 It is a schematic diagram of the main circuit equivalent circuit when three cells of the integrated power battery pack composed of four battery cells operate in the charging mode and one cell operates in the fault mode;

[0048] Figure 7 A schematic diagram of the connection of the 4 battery cell integrated circuits in charging mode;

[0049] Figure 8 Schematic diagram of the connection of 4 battery cell integrated circuits in discharge mode;

[0050] Fig. 9 Schematic diagram of the connection of 4 battery cell integrated circuits in bypass mode;

[0051] Figure 10-11 The schematic diagram of the discharge and charge process is that the battery cell B3 fails, the relay k31 is closed, and the remaining three battery cells are discharged and charged through the flyback converter;

[0052] Symbol name in the figure: U bus ——Battery pack bus voltage; C 11 ——Capacitor on the input side of the bidirectional flyback converter; C 12 ——bidirectional flyback converter output side capacitance; K 11 ——The first relay in the bidirectional flyback converter; K 12 ——The second relay in the bidirectional flyback converter; S 11 ——The first switch in the bidirectional flyback converter; K 12 ——The second switch in the bidirectional flyback converter; T 1 ——Transformer in bidirectional flyback converter; B 1 ——Battery unit; U inr ——Reference value of the battery cell integrated circuit input voltage; U inf ——Battery unit integrated circuit input voltage value; U ine ——Battery cell integrated circuit input voltage error value; I fr ——Battery unit discharge current reference value; I ff ——Battery unit discharge current value; I fe ——Battery unit discharge current error value; ur1 ——Modulation signal of battery cell discharge mode; U Bf ——Battery unit voltage value; U Br ——Battery unit voltage reference value; U Be ——Battery cell voltage error value; I cr ——Battery unit charging current reference value; I cf ——Battery unit charging current value; I ce ——Battery unit charging current error value; u r2 ——Modulation signal of battery cell charging mode; u r ——Modulation signal of bidirectional flyback converter; u out ——External signal of operation mode; u S11 ——The first switch tube driving signal; u S12 ——The second switch tube driving signal; u K1 ——Select switch drive signal; u K11 ——The first relay drive signal; u K12 ——The second relay driving signal. DETAILED DESCRIPTION

[0053] 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.

[0054] 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.

[0055] In the absence of conflict, the embodiments in the present disclosure and the features in the embodiments may be combined with each other.

[0056] Embodiment 1

[0057] like Figure 1 As shown, this embodiment discloses a battery cell integrated circuit, including a bidirectional flyback converter and a digital controller, wherein the digital controller is composed of a battery charging controller, a battery discharging controller, a selection switch, a signal conditioner, and an operating mode identifier. The interconnection relationship and components thereof will be described in detail below.

[0058] The positive electrode of the i-th (i=1, 2, ..., n-1) battery cell integrated circuit is connected to the negative electrode of the i+1-th (i=1, 2, ..., n-1) battery cell integrated circuit, the negative electrode of the first battery cell integrated circuit serves as the negative electrode of the electric vehicle integrated power battery pack, and the positive electrode of the n-th battery cell integrated circuit serves as the positive electrode of the electric vehicle integrated power battery pack; the i-th (i=1, 2, ..., n) battery cell integrated circuit includes a bidirectional flyback converter, a digital controller, a first voltage sensor, a second voltage sensor, and a current sensor; the bidirectional flyback converter includes an input side capacitor, a first relay, a first switch tube, a transformer, a second switch tube, a second relay, and an output side capacitor, wherein the first relay includes a group of normally open contacts, and the second relay includes 2 groups of normally open contacts. ; The positive electrode of the input side capacitor, the first terminal of the first relay, the first terminal of the second relay, and the like-name end of the primary winding of the transformer are connected together and serve as the positive electrode of the battery cell integrated circuit; the drain of the first switch tube is connected to the opposite-name end of the primary winding of the transformer; the negative electrode of the input side capacitor, the second terminal of the first relay, the third terminal of the second relay, and the source of the first switch tube are connected together and serve as the negative electrode of the battery cell integrated circuit; the opposite-name end of the secondary winding of the transformer is connected to the source of the second switch tube; the drain of the second switch tube, the second terminal of the second relay, the positive electrode of the output side capacitor, and the positive electrode of the battery cell are connected together; the like-name end of the secondary winding of the transformer, the fourth terminal of the second relay, the negative electrode of the output side capacitor, and the negative electrode of the battery cell are connected together.

[0059] The first input terminal and the second input terminal of the first voltage sensor are respectively connected to the positive electrode and the negative electrode of the battery cell integrated circuit; the first input terminal and the second input terminal of the second voltage sensor are respectively connected to the positive electrode and the negative electrode of the battery cell; the input terminal of the current sensor is connected in series with the battery cell.

[0060] The digital controller includes a battery discharge controller, a battery charge controller, a selection switch, a signal conditioner, and an operation mode identifier; in the battery discharge controller, the positive input end of the first subtractor is connected to the reference value of the input voltage of the battery cell integrated circuit, the negative input end of the first subtractor is connected to the output end of the first voltage sensor, the output end of the first subtractor is connected to the input end of the input voltage regulator, and the output end of the input voltage regulator is connected to the positive input end of the second subtractor; the output end of the current sensor is connected to the output end of the inverter, and the output end of the inverter is connected to the negative input end of the second subtractor; the output end of the second subtractor is connected to the input end of the battery discharge current regulator; in the battery charge controller, the positive input end of the third subtractor is connected to the reference value of the battery cell voltage, the negative input end of the third subtractor is connected to the output end of the second voltage sensor, the output end of the third subtractor is connected to the input end of the battery voltage regulator, and the output end of the battery voltage regulator is connected to the positive input end of the third subtractor. The positive input end of the 4th subtractor; the output end of the current sensor is connected to the negative input end of the 4th subtractor; the output end of the 4th subtractor is connected to the input end of the battery charging current regulator; the second terminal and the third terminal of the selection switch are respectively connected to the output end of the battery discharging current regulator and the output end of the battery charging current regulator; the first terminal of the selection switch is connected to the first terminal of the signal conditioner; the first input end, the second input end and the third input end of the operation mode identifier are respectively connected to the output end of the second voltage sensor, the output end of the current sensor, and the external signal of the operation mode; the first output end signal, the second output end signal and the third output end signal of the operation mode identifier are respectively used as the driving signals of the selection switch, the first relay and the second relay; the second terminal of the signal conditioner is connected to the external signal of the operation mode; the output signal of the third terminal and the output signal of the fourth terminal of the signal conditioner are respectively used as the driving signals of the first switch tube and the second switch tube.

[0061] Example 2

[0062] This embodiment discloses a control method of a battery cell integrated circuit, including:

[0063] The operation mode of the battery cell integrated circuit is determined by the battery cell voltage, battery current and external operation mode signal. There are 4 operation modes in total, namely charging mode, discharging mode, fault mode and bypass mode. The first output signal of the operation mode identifier is u K1 , the second output signal of the operating mode identifier is u K11 , the third output signal of the operating mode identifier is u K12 .

[0064] When the battery pack is charging, the mode recognizer determines the charging mode, u K1 =1,u K11 =0,u K12=0, the first terminal of the corresponding selection switch is connected to the third terminal, the signal output by the battery charging controller is used as the input signal of the signal conditioner, the first group of normally open contacts of the first relay is disconnected, the two groups of normally open contacts of the second relay are disconnected, the second switch tube is in the off state, and the first switch tube works at high frequency. The corresponding equivalent circuit is as follows Figure 2 shown.

[0065] When the battery pack is discharged, the pattern recognizer determines the discharge mode, u K1 =-1,u K11 =0,u K12 =0, the first terminal of the corresponding selection switch is connected to the second terminal, the signal output by the battery discharge controller is used as the input signal of the signal conditioner, the first group of normally open contacts of the first relay is disconnected, the two groups of normally open contacts of the second relay are disconnected, the second switch tube works at high frequency, and the first switch tube is in the off state. The corresponding equivalent circuit is as follows Figure 3 shown.

[0066] When a battery cell fails, regardless of whether the battery pack is in charging or discharging mode, the integrated circuit corresponding to the failed battery cell is determined as a failure mode by the pattern identifier. K1 =0,u K11 =1,u K12 =0, the first terminal of the corresponding selection switch is suspended, the first group of normally open contacts of the first relay is closed, the two groups of normally open contacts of the second relay are disconnected, the battery discharge controller and the battery charging controller are not working, the first switch tube and the second switch tube are both in the cut-off state, and the corresponding equivalent circuit is as follows Figure 4 shown.

[0067] When the battery pack is discharging and the battery cell voltage is close to the input voltage of the integrated circuit, it becomes inefficient to discharge the battery cell through the bidirectional flyback converter, so the bypass mode is added. K1 =0,u K11 =0,u K12 =1, the first terminal of the corresponding selection switch is suspended, the first group of normally open contacts of the first relay is disconnected, the two groups of normally open contacts of the second relay are closed, the battery discharge controller and the battery charging controller are not working, the first switch tube and the second switch tube are both in the cut-off state, and the corresponding equivalent circuit is as follows Figure 5 shown.

[0068] It should be noted that the working principle of the bidirectional flyback converter is the same as that of the ordinary flyback converter. When the battery cell is charging or discharging, only one switch tube works at high frequency, and the body diode of the other switch tube is alternately turned on and off at high frequency, which will not be repeated here.

[0069] To better explain the working principle of the battery pack, Figure 6An equivalent circuit of a main circuit of a battery pack composed of four battery cell integrated circuits during charging is given, wherein, if the third battery cell integrated circuit fails, the normally open contact of the first relay in the third battery cell integrated circuit is closed, and the entire third battery cell integrated circuit is bypassed and no longer participates in the work; in addition, the first, second, and fourth battery cell integrated circuits operate in charging mode, absorbing electrical energy from the DC bus and charging their respective battery cells through the flyback converter.

[0070] Embodiment 3

[0071] This embodiment discloses a power battery pack, which is composed of n of the above-mentioned battery cell integrated circuits. The positive electrode of the i-th battery cell integrated circuit is connected to the negative electrode of the i+1-th battery cell integrated circuit. The negative electrode of the 1st battery cell integrated circuit serves as the negative electrode of the electric vehicle integrated power battery pack, and the positive electrode of the n-th battery cell integrated circuit serves as the positive electrode of the electric vehicle integrated power battery pack, i=1, 2,…, n-1.

[0072] In further explanation, the battery pack includes n battery cell integrated circuits, each of which includes a bidirectional flyback converter, a switch, a battery cell, and a digital control device. The bidirectional flyback converters in each battery cell integrated circuit are connected to each other, and the battery cell is switched by a digital controller, so that the battery cell integrated circuit can operate in a charging mode, a discharging mode, a bypass mode, and a fault mode. The following takes four battery cell integrated circuits as examples to illustrate the operation of the flyback converter.

[0073] Each battery cell of the embodiment of the present disclosure is not directly connected in series, which can effectively avoid the voltage unevenness phenomenon in the traditional battery pack structure; when any battery cell fails, the operation of the failed cell can be cut off, thereby achieving safe and reliable operation of the power battery pack.

[0074] The digital control device can control the battery cells to operate in charging mode, discharging mode, bypass mode and fault mode, ensuring that the battery cells operate independently of each other, avoiding the voltage equalization problem of the battery cells in the traditional series battery pack and the problem of the battery pack being unable to operate due to the failure of any battery cell.

[0075] There is no direct connection between the battery cells. The four operating modes of the bidirectional flyback converter can ensure that the integrated power battery pack can operate normally under any conditions, thus avoiding the voltage equalization problem of the battery cells in the traditional series battery pack and the problem of the battery pack failing to operate due to the failure of any battery cell.

[0076] In charging mode, the connections of the 4 battery cell integrated circuits are as follows: Figure 7As shown, at this time, all the contact switches of relays Ki1 (i = 1, 2, 3, 4) and Ki2 (i = 1, 2, 3, 4) are in the open state, so Figure 7 Ki1 (i = 1, 2, 3, 4) and Ki2 (i = 1, 2, 3, 4) are not drawn; the energy is supplied by the DC bus, i.e. Figure 7 The Ubus in the flyback converter flows to each battery unit; the switch tube on the battery side is not controlled at this stage and is only used as a diode; the working principle of each flyback converter belongs to the existing technology and will not be explained in detail here.

[0077] In discharge mode, the connections of the 4 battery cell integrated circuits are as follows: Figure 8 At this time, all the contact switches of relays Ki1 (i=1,2,3,4) and Ki2 (i=1,2,3,4) are in the open state, so Figure 7 Ki1 (i = 1, 2, 3, 4) and Ki2 (i = 1, 2, 3, 4) are not drawn; the energy flows from the battery unit to the bus.

[0078] In bypass mode, the connections of the 4 battery cell integrated circuits are as follows: Fig. 9 During the battery discharge process, when the voltage of the four battery cells is high enough to ensure the normal power supply of the DC bus, the relay Ki2 (i=1,2,3,4) is turned on, and the battery cells are directly connected in series through the relay Ki2 (i=1,2,3,4). The bus voltage formed is the sum of the voltages of the battery cells.

[0079] Fault mode: When one of the battery cells fails, the cell and the corresponding flyback converter are directly short-circuited. Figure 10-11 The schematic diagram shows that during the discharge and charge processes of the corresponding battery pack, battery cell B3 fails, relay k31 is closed, and the remaining three battery cells are discharged and charged through the flyback converter.

[0080] Embodiment 4

[0081] This embodiment discloses an electric vehicle, which is powered by the power battery pack mentioned above.

[0082] The above technical solution disclosed in the present invention operates the battery integrated unit in four modes of charging, discharging, bypass and fault through the control of relays, thereby maximizing the potential of the battery cells and ensuring: each battery cell is charged or discharged individually, avoiding the problem of battery cell damage caused by overcharging or over-discharging of individual battery cells in the series battery pack; the bypass mode ensures the high efficiency of the battery pack operation; the fault mode ensures that the battery pack can continue to work when an individual cell fails, avoiding the problem of the battery pack not being able to operate due to damage to individual battery cells in the series battery pack.

[0083] 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 cell integrated circuit, characterized in that: include: Bidirectional flyback converter, detection unit and digital controller; The bidirectional flyback converter is connected to a battery cell; the bidirectional flyback converter comprises an input side capacitor, a first relay, a first switch tube, a transformer, and a second relay; the positive electrode of the input side capacitor, the first terminal of the first relay, the first terminal of the second relay, and the same-name end of the primary winding of the transformer are connected together and serve as the positive electrode of the battery cell integrated circuit; the negative electrode of the input side capacitor, the second terminal of the first relay, the third terminal of the second relay, and the source electrode of the first switch tube are connected together and serve as the negative electrode of the battery cell integrated circuit; the drain electrode of the first switch tube is connected to the opposite-name end of the primary winding of the transformer; the first relay comprises a group of normally open contacts, and the second relay comprises two groups of normally open contacts; The detection unit detects the voltage data of the bidirectional flyback converter and the voltage and current data of the battery cell respectively and transmits them to the digital controller; The digital controller includes a battery discharge controller, a battery charge controller, a selection switch, a signal conditioner, and an operation mode identifier; The digital controller determines the operation mode of the battery cell integrated circuit according to the received voltage, current and operation mode external signal, and operates in a charging mode, a discharging mode, a fault mode or a bypass mode; When a battery cell fails, regardless of whether the battery pack is in a charging or discharging mode, the integrated circuit corresponding to the failed battery cell is determined as a failure mode by the operation mode identifier; In the bypass mode, one group of normally open contacts of the first relay is disconnected, two groups of normally open contacts of the second relay are closed, the battery discharge controller and the battery charge controller do not work, and the first switch tube and the second switch tube are both in the cut-off state; In the fault mode, when one of the battery cells fails, the cell and the corresponding bidirectional flyback converter are directly short-circuited.

2. The battery cell integrated circuit according to claim 1, wherein: The bidirectional flyback converter further includes: a second switch tube and an output side capacitor; The opposite-name end of the secondary winding of the transformer is connected to the source of the second switch tube; The drain of the second switch tube, the second terminal of the second relay, the positive electrode of the output side capacitor, and the positive electrode of the battery unit are connected together; The same-name end of the secondary winding of the transformer, the fourth terminal of the second relay, the negative electrode of the output side capacitor, and the negative electrode of the battery unit are connected together; a first voltage sensor, a second voltage sensor and a current sensor; The first input terminal and the second input terminal of the first voltage sensor are respectively connected to the positive electrode of the battery cell integrated circuit and the negative electrode of the battery cell integrated circuit; The first input terminal and the second input terminal of the second voltage sensor are connected to the positive electrode of the battery cell and the negative electrode of the battery cell respectively; The input terminal of the current sensor is connected in series with the battery unit.

3. A control method for a battery cell integrated circuit, characterized in that: A battery cell integrated circuit as claimed in any one of claims 1 to 2, comprising: The operation mode of the battery cell integrated circuit is determined by the battery cell voltage, battery current and external operation mode signal. There are 4 operation modes in total, namely, discharge mode, charge mode, fault mode and bypass mode. In the charging mode, the signal output by the battery charging controller is used as the input signal of the signal conditioner, one group of normally open contacts of the first relay is disconnected, two groups of normally open contacts of the second relay are disconnected, the second switch tube is in the off state, and the first switch tube works at a high frequency for charging; In the bypass mode, one group of normally open contacts of the first relay is disconnected, two groups of normally open contacts of the second relay are closed, the battery discharge controller and the battery charge controller do not work, and the first switch tube and the second switch tube are both in the cut-off state; In the fault mode, one group of normally open contacts of the first relay is closed, two groups of normally open contacts of the second relay are disconnected, the battery discharge controller and the battery charge controller do not work, and the first switch tube and the second switch tube are both in the cut-off state.

4. The control method of the battery cell integrated circuit as claimed in claim 3, characterized in that: In the discharge mode, the signal output by the battery discharge controller is used as the input signal of the signal conditioner, one group of normally open contacts of the first relay is disconnected, two groups of normally open contacts of the second relay are disconnected, the second switch tube operates at high frequency, and the first switch tube is in the off state.

5. A power battery pack, characterized in that it consists of The invention is composed of n battery cell integrated circuits as described in any one of claims 1-2, the positive electrode of the i-th battery cell integrated circuit is connected to the negative electrode of the i+1-th battery cell integrated circuit, the negative electrode of the first battery cell integrated circuit serves as the negative electrode of the electric vehicle integrated power battery pack, and the positive electrode of the n-th battery cell integrated circuit serves as the positive electrode of the electric vehicle integrated power battery pack, i=1, 2, ..., n-1.

6. An electric vehicle, characterized in that: The electric vehicle is powered by the power battery pack described in claim 5 above.

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