Battery pack active balancing circuit and control method

Abstract

The application relates to the technical field of energy storage batteries, and discloses a battery pack active equalization circuit and a control method. The battery pack active equalization circuit comprises a battery pack connection end, a matrix switch module, a polarity conversion module, an active equalization module, a sampling control module and a voltage conversion circuit. The input end of the voltage conversion circuit is connected to the battery pack connection end, and the output end is connected to the sampling control module. Electricity is taken from the battery pack and converted into the working voltage required by the sampling control module. According to the application, the voltage conversion circuit directly takes electricity from the high-voltage side of the battery pack and supplies power to the sampling control module. The power supply path does not need to cross the isolation band, thereby avoiding the influence of voltage fluctuation caused by power supply across the isolation band on the working stability of the sampling control module, and improving the working stability of the sampling control module.

Description

Technical Field

[0001] This application relates to the field of energy storage battery technology, specifically to active balancing circuits and control methods for battery packs. Background Technology

[0002] In recent years, energy storage technology has developed rapidly, and lithium-ion batteries are typically used in energy storage systems in series and parallel configurations. However, inconsistencies in capacity, internal resistance, and other properties exist between individual cells, which can be exacerbated by prolonged use and may even lead to safety incidents. Therefore, balanced management of battery packs is necessary to reduce inconsistencies and extend their lifespan.

[0003] In related technologies, passive balancing consumes energy by connecting a resistor in parallel across a single cell, but this results in significant heat generation and low efficiency when the balancing current is large. Active balancing, on the other hand, utilizes energy storage components such as capacitors, inductors, or transformers to redistribute energy, achieving higher energy utilization. Among these, the active balancing scheme using a switch matrix combined with a transformer can achieve energy transfer between any two cells, offering fast balancing speed and wide applicability.

[0004] In the above scheme, the drive circuits for the matrix switch and polarity reversing switch, as well as the sampling circuit for collecting the equalization current, are all located on the high-voltage side of the battery pack, and their operating power is obtained from the low-voltage side via an isolation transformer. This power supply path needs to cross the isolation zone, and the drive circuit and sampling circuit have certain requirements for the stability of the operating power supply. Under the above power supply architecture, the operating stability of the high-voltage side circuit is difficult to guarantee sufficiently. Summary of the Invention

[0005] This application provides a battery pack active balancing circuit and control method to solve the problem of insufficient operational stability of the high-voltage side drive circuit and sampling circuit in the active balancing circuit.

[0006] In a first aspect, this application provides a battery pack active balancing circuit, comprising: a battery pack connection terminal configured to connect to a battery pack consisting of multiple cells connected in series; a matrix switch module connected to the battery pack connection terminal and configured to select a target cell in the battery pack; a polarity conversion module connected to the matrix switch module and configured to adjust the output polarity of the target cell to a preset direction; an active balancing module connected to the polarity conversion module and configured to perform charge / discharge energy transfer on the target cell; a sampling control module connected to the matrix switch module, the polarity conversion module, and the active balancing module, configured to collect voltage information of each cell in the battery pack, collect the balancing current of the active balancing module, and control the selection and polarity switching of the matrix switch module and the polarity conversion module according to the voltage information, and control the active balancing module to perform charge / discharge balancing on the target cell; and a voltage conversion circuit, wherein the input terminal of the voltage conversion circuit is connected to the battery pack connection terminal, the output terminal of the voltage conversion circuit is connected to the sampling control module, and the voltage conversion circuit is configured to draw power from the battery pack and convert it into the operating voltage required by the sampling control module.

[0007] Beneficial effects: The active balancing circuit for the battery pack in this application sets up a voltage conversion circuit, so that the input terminal of the voltage conversion circuit is connected to the battery pack connection terminal and the output terminal is connected to the sampling control module. The voltage conversion circuit directly draws power from the high-voltage side of the battery pack and supplies power to the sampling control module. The operating power of the sampling control module does not need to be obtained from the low-voltage side through the isolation transformer, and the power supply path does not need to cross the isolation zone. This avoids the impact of voltage fluctuations caused by power supply across the isolation zone on the working stability of the sampling control module, thereby improving the working stability of the sampling control module.

[0008] In one optional embodiment, the active balancing module includes: a transformer having a high-voltage side and a low-voltage side, the high-voltage side being used to connect to the battery pack, and the low-voltage side being used to connect to a DC source; a first controllable switch transistor disposed on the high-voltage side, configured to, when turned on, allow the battery pack to release energy to the low-voltage side through the transformer to achieve discharge balancing; and a second controllable switch transistor disposed on the low-voltage side, configured to, when turned on, allow the DC source to replenish energy to the battery pack through the transformer to achieve charging balancing; wherein the first controllable switch transistor and the second controllable switch transistor are not turned on simultaneously.

[0009] Beneficial effects: By setting the first controllable switch on the high-voltage side of the transformer and the second controllable switch on the low-voltage side of the transformer, and limiting the first controllable switch to release energy from the battery pack to the low-voltage side through the transformer when it is turned on (discharge balancing), and the second controllable switch to replenish energy from the DC source to the battery pack through the transformer when it is turned on (charge balancing), and the two switches are not turned on at the same time, a single transformer can realize bidirectional energy transfer between the battery pack and the DC source, eliminating the need for separate balancing circuits for charging and discharging, simplifying the circuit structure. At the same time, since the charging and discharging circuits are not turned on at the same time, the risks of energy backflow and loop shoot-through are avoided.

[0010] In one optional embodiment, the sampling control module includes: a first sampling resistor, disposed on the high-voltage side of the transformer, configured to allow a discharge equalization current to flow through and generate a first voltage drop across the first sampling resistor; a second sampling resistor, disposed on the low-voltage side of the transformer, configured to allow a charging equalization current to flow through and generate a second voltage drop across the second sampling resistor; a differential amplifier, the two input terminals of which are respectively connected to the two ends of the first sampling resistor, configured to acquire the first voltage drop to determine the discharge equalization current; an analog front-end chip, connected to the battery pack connection terminal, configured to acquire the voltage and temperature of each cell; the analog front-end chip is also connected to the output terminal of the differential amplifier, configured to receive the discharge equalization current; a microcontroller unit, connected to the two ends of the second sampling resistor, configured to acquire the voltage across the second sampling resistor to determine the charging equalization current; the microcontroller unit is also connected to the control terminals of the first controllable switch and the second controllable switch, configured to control the on and off of the first controllable switch and the second controllable switch; the microcontroller unit is also connected to the analog front-end chip, configured to receive the voltage and the temperature.

[0011] Beneficial effects: By setting a first sampling resistor and a second sampling resistor on the high-voltage side and the low-voltage side of the transformer respectively, the discharge equalization current generates a first voltage drop when flowing through the first sampling resistor, and the charging equalization current generates a second voltage drop when flowing through the second sampling resistor. This achieves separate detection of the high-voltage side discharge current and the low-voltage side charging current. The high-voltage side discharge current is collected by a differential amplifier and sent to the analog front-end chip, while the low-voltage side charging current is directly collected by the microcontroller unit. This makes the detection paths of the charging and discharging equalization current independent and non-interfering, improving the current sampling accuracy. At the same time, the analog front-end chip and the microcontroller unit collect their respective current signals, reducing signal transmission loss and interference between modules, further improving the accuracy of equalization control.

[0012] In one optional implementation, the sampling control module further includes: an isolation circuit connected to the analog front-end chip and configured to achieve electrical isolation between the analog front-end chip and the microcontroller unit; and a gateway chip connected to the isolation circuit and the microcontroller unit and configured to convert the SPI communication of the microcontroller unit into daisy-chain communication of the analog front-end chip; the analog front-end chip transmits the voltage, the temperature, and the discharge equalization current to the microcontroller unit through the isolation circuit and the gateway chip.

[0013] Beneficial effects: By setting up an isolation circuit and a gateway chip between the analog front-end chip and the microcontroller unit, the isolation circuit achieves electrical isolation between the high-voltage side and the low-voltage side, ensuring system safety. The gateway chip converts the microcontroller unit's SPI communication into the analog front-end chip's daisy-chain communication, making the communication protocol between the microcontroller unit and the analog front-end chip compatible. This eliminates the need to modify the existing chip's communication interface, reducing the implementation cost of the communication link. At the same time, the voltage, temperature, and discharge equalization current collected by the analog front-end chip are completely transmitted to the microcontroller unit through the isolation circuit and the gateway chip, providing an accurate and complete data foundation for the microcontroller unit to make equalization decisions.

[0014] In one optional implementation, the microcontroller includes a CAN communication interface configured to communicate with a host computer or main controller; the microcontroller is further configured to: determine whether there is an abnormality based on the voltage and temperature collected by the analog front-end chip; if an abnormality exists, report the abnormality to the host computer or main controller via the CAN communication interface; if no abnormality exists, determine the cell with the highest voltage from the multiple battery cells as the discharge equalization target cell or the cell with the lowest voltage as the charge equalization target cell based on the voltage.

[0015] Beneficial effects: The microcontroller determines whether there are any abnormalities based on the voltage and temperature of each cell collected by the analog front-end chip. If an abnormality is detected, it reports to the host computer or main controller via the CAN communication interface. If no abnormality is detected, the cell with the highest voltage is selected as the target cell for discharge equalization, and the cell with the lowest voltage is selected as the target cell for charging equalization. By integrating abnormality detection, fault reporting, and equalization target selection into the microcontroller, fault protection and equalization control are achieved in a coordinated manner. This avoids the safety risks that may be caused by performing equalization operations under abnormal conditions. At the same time, communication with the host computer or main controller via the CAN communication interface allows the system status to be reported in real time, which facilitates global monitoring and scheduling by the host computer, thereby improving the system's security and manageability.

[0016] In one optional implementation, the sampling control module further includes: an I / O expansion chip connected to the matrix switch module and the polarity conversion module; the analog front-end chip is connected to the matrix switch module and the polarity conversion module through the I / O expansion chip, and is configured to drive the switching actions in the matrix switch module and the polarity conversion module through the I / O expansion chip.

[0017] Beneficial effects: By setting up an I / O expansion chip between the analog front-end chip and the matrix switch module and polarity conversion module, the analog front-end chip transmits control signals to the I / O expansion chip, which then drives the switching actions in the matrix switch module and polarity conversion module. Since there are many switches in the matrix switch module and polarity conversion module, and the number of I / O ports of the analog front-end chip is limited, the I / O expansion chip expands the number of I / O ports, enabling the analog front-end chip to control more switches. This avoids the increased cost caused by replacing the AFE chip with a higher specification due to insufficient I / O ports, and reduces hardware costs while ensuring control capabilities.

[0018] In one optional implementation, the matrix switch module includes: N+1 selector switches, where N is the number of battery cells. The N+1 selector switches are connected in series, and the common connection point between each pair of adjacent battery cells is connected to the common terminal between the two adjacent selector switches, so that each pair of adjacent battery cells shares one selector switch.

[0019] Beneficial effects: By setting the matrix switch module to N+1 switches connected in series, and connecting the common connection point between each pair of adjacent cells to the common terminal between the two adjacent switches, each pair of adjacent cells can share one switch. N+1 switches can select any target cell among the N cells. Compared with using two switches per cell (2N in total), this significantly reduces the number of switches, lowers circuit complexity and hardware cost. At the same time, the reduction in the number of switches also reduces the control difficulty and power consumption of the switch drive circuit.

[0020] In one optional implementation, the polarity conversion module includes: four conversion switches forming a bridge circuit, the two pairs of arms of the bridge circuit being connected to the positive and negative terminals of the target battery cell respectively, configured to adjust the polarity of the target battery cell to be consistent with the preset polarity of the active balancing module by opening and closing different pairs of arms in the bridge circuit.

[0021] Beneficial effects: A bridge circuit is constructed using four switches. The two pairs of arms of the bridge circuit are connected to the positive and negative terminals of the target cell, respectively. When one pair of arms is turned on, the target cell is connected to the active balancing module with positive polarity. When the other pair of arms is turned on, the target cell is connected to the active balancing module with negative polarity (i.e., reverse polarity). This ensures that the output polarity of the target cell can be adjusted to match the preset polarity of the active balancing module, regardless of its series position in the battery pack. This eliminates the need to design different balancing access paths for cells in different positions, simplifying the control logic for polarity matching. At the same time, the bridge circuit has a simple structure, reliable control, and only requires four switches to achieve polarity switching, resulting in low hardware costs.

[0022] In one optional implementation, there are multiple analog front-end chips, which are connected in a daisy-chain manner; each analog front-end chip is provided with a voltage conversion circuit.

[0023] Beneficial effects: By setting up multiple analog front-end chips and connecting them via daisy-chain communication, the problem of the limited number of sampling channels of a single AFE chip (usually no more than 18 strings) is solved. When the number of battery cells exceeds the number of sampling channels of a single AFE, the number of sampling channels can be flexibly expanded by cascading multiple AFEs to meet the balancing needs of large-scale battery packs. At the same time, each analog front-end chip is equipped with a voltage conversion circuit, and each AFE draws power independently from the battery pack, avoiding voltage fluctuations caused by long transmission paths or load changes when a single power supply powers multiple AFEs. This ensures the power supply stability of each AFE and its surrounding circuits and avoids sampling and control abnormalities caused by insufficient power supply or voltage fluctuations.

[0024] In one optional implementation, the microcontroller unit is further configured to: during the discharge equalization process, determine whether the target cell has completed discharge equalization based on the discharge equalization current; if discharge equalization has not been completed, control the active equalization module to continue discharging equalization of the target cell; and during the charging equalization process, determine whether the target cell has completed charging equalization based on the charging equalization current; if charging equalization has not been completed, control the active equalization module to continue charging equalization of the target cell.

[0025] Beneficial effects: By using the microcontroller to determine whether discharge equalization is complete based on the discharge equalization current during discharge equalization and to continue discharge equalization if it is not complete, and by using the microcontroller to determine whether charge equalization is complete based on the charge equalization current during charge equalization and to continue charge equalization if it is not complete, closed-loop control of the discharge equalization process and charge equalization process is achieved respectively. The microcontroller can monitor the magnitude change of the corresponding equalization current in real time in both equalization modes. When the equalization current decreases to a preset threshold, it determines that equalization is complete and terminates the equalization process in a timely manner, avoiding over-discharge or over-charge. At the same time, the closed-loop control can dynamically adjust the equalization process based on current feedback, improving the accuracy and safety of equalization.

[0026] Secondly, this application provides a battery pack active balancing control method, comprising: acquiring voltage information of multiple battery cells in a battery pack; determining a target battery cell from the multiple battery cells that needs to be balanced based on the voltage information; controlling a matrix switch module to select the target battery cell and controlling a polarity conversion module to adjust the polarity of the target battery cell to match the preset polarity of the active balancing module; and controlling a controllable switch in the active balancing module to conduct, so as to perform charging balancing or discharging balancing on the target battery cell through the active balancing module. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a logic block diagram of the active balancing circuit of the battery pack according to an embodiment of this application; Figure 2 This is a schematic diagram of an active balancing circuit power supply scheme in related technologies; Figure 3 This is a schematic diagram of the power supply scheme for the voltage conversion circuit in the active balancing circuit of the battery pack according to an embodiment of this application; Figure 4 This is a schematic diagram of a multi-analog front-end chip cascade architecture according to an embodiment of this application; Figure 5 This is a schematic diagram of the working principle of the active balancing circuit of the battery pack according to an embodiment of this application; Figure 6 This is a flowchart illustrating the active balancing control method for a battery pack according to an embodiment of this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] It is understood that before using the technical solutions disclosed in the various embodiments of this application, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in this application in an appropriate manner in accordance with relevant laws and regulations, and user authorization should be obtained.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0032] To address the issue that in related technologies, the high-voltage side drive circuit and sampling circuit in active balancing circuits draw power from the low-voltage side across the isolation zone via an isolation transformer, making it difficult to fully guarantee operational stability, this application provides a battery pack active balancing circuit and control method. By setting up a voltage conversion circuit, the voltage conversion circuit can directly draw power from the high-voltage side of the battery pack and supply power to the sampling control module, eliminating the need for the power supply path to cross the isolation zone, thereby improving the operational stability of the sampling control module.

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0034] It should be noted that when a component is described as "connected to" another component, it can be directly connected to that other component or indirectly connected to it through an intermediate component. The terms "include" and "have," and any variations thereof, are intended to cover non-exclusive inclusion.

[0035] Furthermore, it should be noted that in this application, "high voltage side" refers to the side connected to the battery pack, and its voltage is the total series voltage of the battery pack (e.g., several hundred volts); "low voltage side" refers to the side connected to the DC source, and its voltage is the low voltage output by the DC source (e.g., 18V to 32V). "Multiple" refers to two or more.

[0036] Reference Figure 1 As shown in the figure, an active balancing circuit for a battery pack provided in this application includes: a battery pack connection terminal (labeled as "N-cell battery pack") for connecting a battery pack composed of multiple cells connected in series; a matrix switch module (labeled as "matrix switch") connected to the battery pack connection terminal for selecting a target cell in the battery pack; a polarity conversion module (labeled as "polarity conversion switch") connected to the matrix switch module for adjusting the output polarity of the target cell to a preset direction; and an active balancing module (labeled as "active balancing circuit") connected to the polarity conversion module for charging and discharging the target cell. The system comprises: a power transfer module; a sampling control module, connected to the matrix switch module, polarity conversion module, and active balancing module, used to collect voltage information of each cell in the battery pack, collect the balancing current of the active balancing module, and control the selection and polarity switching of the matrix switch module and polarity conversion module based on the voltage information, as well as control the active balancing module to perform charge and discharge balancing on the target cell; and a voltage conversion circuit (marked as "DC / DC converter" in the figure), whose input is connected to the battery pack connection terminal and whose output is connected to the sampling control module, used to draw power from the battery pack and convert it to the operating voltage required by the sampling control module. Specifically, the sampling control module includes: an analog front-end chip (AFE), connected to the battery pack connection terminal and the sampling resistor in the active balancing module; an I / O expansion chip, connected to the AFE, matrix switch module, and polarity conversion module; a differential amplifier, connected to the sampling resistor in the active balancing module and the AFE; and a microcontroller unit (MCU), connected to the AFE through an isolation circuit and a gateway chip. The output of the voltage conversion circuit is connected to the drive voltage terminals of the I / O expansion chip, differential amplifier, matrix switch, and polarity conversion switch, respectively.

[0037] The aforementioned active balancing circuit for the battery pack, by setting up a voltage conversion circuit and allowing the voltage conversion circuit to directly draw power from the high-voltage side of the battery pack to power the sampling control module, eliminates the need for the sampling control module to obtain its operating power from the low-voltage side via an isolation transformer. The power supply path does not need to cross the isolation zone, thus avoiding the impact of voltage fluctuations caused by power supply across the isolation zone on the operating stability of the sampling control module, thereby improving the operating stability of the sampling control module.

[0038] Specifically, the matrix switch module is connected between the battery pack connection terminal and the polarity conversion module. By controlling the closing and opening of different switches in the matrix switch module, the target battery cell is connected to the equalization circuit. As one specific implementation method, refer to... Figure 1 or Figure 5 As shown, the matrix switch module includes N+1 switches (refer to...). Figure 1 or Figure 5 As shown in the diagram (Q1 to QN+1), where N is the number of battery cells, N+1 switches are connected in series. The common connection point between any two adjacent battery cells is connected to the common terminal between the two adjacent switches, so that each pair of adjacent battery cells shares one switch. When it is necessary to select the nth battery cell, control switches Qn and Qn+1 are closed, and the remaining switches are opened, thus connecting the nth battery cell to the equalization circuit. This configuration of N+1 switches connected in series with adjacent battery cells sharing one switch allows for the selection of any target battery cell from the N battery cells using only N+1 switches. Compared to the scheme of using two switches per battery cell (2N in total), this significantly reduces the number of switches, lowers circuit complexity, and reduces hardware costs. The switching devices in the matrix switching module can be relays or MOSFETs; those skilled in the art can choose the appropriate type of switching device based on the actual application scenario.

[0039] The polarity conversion module is connected between the matrix switch module and the active balancing module, and is used to adjust the positive and negative output directions of the target battery cell to match the preset polarity of the active balancing module. As one specific implementation method, refer to... Figure 1 or Figure 5 As shown, the polarity conversion module includes four switches (see reference). Figure 1 or Figure 5 As shown in K1 to K4, four switches form a bridge circuit, with the two pairs of arms of the bridge circuit connected to the positive and negative terminals of the target cell, respectively. When the target cell needs to be connected to the active balancing module with positive polarity, control switches K1 and K4 are closed, and K2 and K3 are open; when the target cell needs to be connected to the active balancing module with reverse polarity, control switches K2 and K3 are closed, and K1 and K4 are open. In this way, regardless of the series connection position of the target cell in the battery pack, its output polarity can be adjusted to match the preset polarity of the active balancing module, eliminating the need to design different balancing access paths for cells in different positions and simplifying the polarity matching control logic. The bridge circuit structure is simple, the control is reliable, and only four switches are needed to achieve polarity switching, resulting in low hardware cost. The switching devices in the polarity conversion module can be relays or field-effect transistors (MOSFETs), and those skilled in the art can select the appropriate type of switching device according to the actual application scenario.

[0040] The active balancing module is used to transfer charging and discharging energy to the target battery cell. As one specific implementation method, refer to... Figure 5As shown, the active balancing module includes a transformer, a first controllable switch S1, and a second controllable switch S2. The transformer has a high-voltage side and a low-voltage side. The high-voltage side is used to connect to the battery pack (i.e., to the output terminal of the polarity conversion module), and the low-voltage side is used to connect to a DC source. The first controllable switch S1 is located on the high-voltage side of the transformer, and the second controllable switch S2 is located on the low-voltage side. When S1 is closed and S2 is open, energy from the battery pack side is released to the low-voltage side through the transformer, achieving discharge balancing; when S2 is closed and S1 is open, energy from the DC source side is replenished to the battery pack side through the transformer, achieving charging balancing. S1 and S2 are not simultaneously turned on to avoid a short circuit caused by direct connection between the high-voltage and low-voltage sides. The above-mentioned bidirectional energy transfer between the battery pack and the DC source can be achieved using a single transformer and one controllable switch on each of the high-voltage and low-voltage sides, eliminating the need for separate balancing circuits for charging and discharging, thus simplifying the circuit structure. The aforementioned controllable switches can be field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs), and those skilled in the art can select the appropriate switch type according to the actual application scenario.

[0041] The sampling control module is used to collect the voltage information of each cell in the battery pack, collect the balancing current of the active balancing module, and control the selection and polarity switching of the matrix switch module and polarity conversion module according to the voltage information, as well as control the active balancing module to perform charge and discharge balancing on the target cell.

[0042] In the sampling control module, the sampling function is implemented in the following way. (Refer to...) Figure 5 As shown, the sampling control module includes a first sampling resistor R1, a second sampling resistor R2, and a differential amplifier. The first sampling resistor R1 is located on the high-voltage side of the transformer; when the discharge equalization current flows through R1, a first voltage drop is generated across R1. The second sampling resistor R2 is located on the low-voltage side of the transformer; when the charging equalization current flows through R2, a second voltage drop is generated across R2. The two input terminals of the differential amplifier are connected to the two ends of R1 respectively, acquiring the first voltage drop and amplifying it before outputting it to determine the discharge equalization current. The differential amplifier can be a model such as NSI1200C from Nanochip Microelectronics, CA-IS1300 from Chuantu Microelectronics, or TPA8000 from 3PEAK. Those skilled in the art can select a suitable differential amplifier model according to actual application requirements. (Refer to...) Figure 1 As shown, the sampling control module also includes an analog front-end chip (AFE), which is connected to the battery pack connection terminal to collect the voltage and temperature of each cell; the AFE is also connected to the output terminal of the differential amplifier to receive the discharge equalization current. (Refer to...) Figure 5As shown, the sampling control module also includes a microcontroller unit (MCU). The MCU is connected to both ends of the second sampling resistor R2 to collect the voltage across R2 to determine the charging equalization current. The MCU is also connected to the control terminals of the first controllable switch S1 and the second controllable switch S2 to control the conduction and cutoff of S1 and S2. The MCU is also connected to the AFE to receive voltage and temperature data collected by the AFE. By setting R1 and R2 on the high-voltage side and the low-voltage side of the transformer respectively, the discharge equalization current flowing through R1 generates a first voltage drop, and the charging equalization current flowing through R2 generates a second voltage drop. This achieves separate detection of the high-voltage side discharge current and the low-voltage side charging current. The high-voltage side discharge current is collected by a differential amplifier and sent to the AFE, while the low-voltage side charging current is directly collected by the MCU. This makes the detection paths of the charging and discharging equalization current independent and non-interfering, improving the current sampling accuracy. The resistance values ​​of R1 and R2 can be in the milliohm (mΩ) range, and the specific resistance values ​​can be determined by those skilled in the art based on the actual equalization current magnitude and the required sampling accuracy.

[0043] In the sampling control module, the control function is implemented in the following way. (Refer to...) Figure 1 As shown, the sampling control module also includes an I / O expansion chip. This chip is connected to the matrix switch module and the polarity conversion module. The AFE connects to these modules via the I / O expansion chip. Since the matrix switch module and polarity conversion module contain a large number of switches, while the AFE has a limited number of I / O ports, the AFE transmits control signals to the I / O expansion chip, which then drives the switches in these modules. This method of expanding the number of I / O ports via the I / O expansion chip allows the AFE to control more switches, avoiding the increased cost of replacing the AFE chip with a higher-specification one due to insufficient I / O ports.

[0044] In the sampling control module, the communication path is implemented as follows. (Refer to...) Figure 1 As shown, the sampling control module also includes an isolation circuit and a gateway chip. The isolation circuit is connected to the AFE, and the gateway chip is connected to both the isolation circuit and the MCU. The AFE transmits the collected voltage, temperature, and discharge equalization current to the MCU through the isolation circuit and the gateway chip. The isolation circuit is used to achieve electrical isolation (high and low voltage isolation) between the AFE and the MCU, and can be implemented using an isolation chip or an isolation transformer. The gateway chip is used to convert the SPI communication on the MCU side to daisy-chain communication on the AFE side, ensuring that the communication protocol between the MCU and the AFE is compatible. The isolation circuit ensures electrical isolation between the high-voltage side and the low-voltage side, guaranteeing system safety; the gateway chip implements the protocol conversion between SPI communication and daisy-chain communication without requiring modification to the existing chip's communication interface, reducing the implementation cost of the communication link.

[0045] The microcontroller unit (MCU) includes a CAN communication interface for communication with a host computer or main controller. The MCU determines whether there are any abnormalities (e.g., excessively high or low voltage in a battery cell, or temperature exceeding safe limits) based on the voltage and temperature data collected by the AFE. When an abnormality is detected, the MCU reports it to the host computer or main controller via the CAN communication interface. The host computer then performs global monitoring and scheduling, avoiding potential safety risks associated with equalization operations under abnormal conditions. When no abnormality is detected, the MCU determines the target cell for discharge equalization (higher voltage requires energy release) or charge equalization (lower voltage requires energy replenishment) based on the voltage values ​​of each battery cell, and accordingly decides whether to initiate charge equalization or discharge equalization. This communication with the host computer or main controller via the CAN communication interface allows for real-time reporting of system status, facilitating global monitoring and scheduling by the host computer, and improving system security and manageability. During discharge equalization, the MCU determines whether the target cell has completed discharge equalization based on the discharge equalization current, and continues to control the active equalization module to perform discharge equalization if not. During charge equalization, the MCU determines whether the target cell has completed charge equalization based on the charge equalization current, and continues to control the active equalization module to perform charge equalization if not. Specifically, when the discharge equalization current decreases to a preset threshold, discharge equalization is considered complete, and the discharge equalization process is terminated in time to avoid over-discharge; when the charge equalization current decreases to a preset threshold, charge equalization is considered complete, and the charge equalization process is terminated in time to avoid over-charging. The above-mentioned closed-loop control of the charge and discharge equalization process is achieved by real-time monitoring of the equalization current change by the MCU, improving the accuracy and safety of equalization. The preset threshold can be determined by those skilled in the art through experiments or simulations based on the battery type, equalization current magnitude, and required equalization accuracy; this application does not impose specific limitations on this.

[0046] The voltage conversion circuit draws power from the battery pack and converts it to the operating voltage required by the sampling control module. (Refer to...) Figure 1 and Figure 3 As shown, the input of the voltage conversion circuit (DC / DC converter) is connected to the battery pack connection (high-voltage side) to draw power from the battery pack; the output of the voltage conversion circuit is connected to the sampling control module, specifically the drive voltage terminals of the I / O expansion chip, differential amplifier, matrix switch, and polarity reversing switch, to power these components. The voltage conversion circuit can be a buck converter (BUCK circuit) or a low-dropout linear regulator (LDO). This scheme, where the voltage conversion circuit directly draws power from the high-voltage side to power the sampling control module, eliminates the need for an additional isolation transformer in related technologies (see [reference]). Figure 2As shown in the diagram, this design reduces the number of components and eliminates the need for the power supply path to cross the isolation zone, thus avoiding the impact of voltage fluctuations caused by power supply across the isolation zone on the stability of the sampling control module. The voltage conversion circuit can utilize commonly available chips, such as the VPS8701B from Yuante or the MK9019GAD from Xinzhou. Those skilled in the art can select a suitable voltage conversion chip based on the actual input voltage range, output voltage requirements, and load capacity. It should be understood that the specific implementation of the voltage conversion circuit includes, but is not limited to, BUCK circuits and LDOs; any voltage conversion method capable of converting the high voltage of the battery pack to the low voltage required by the sampling control module can be applied to this application.

[0047] Reference Figure 4 As shown, as an extended implementation of this application's embodiments, when the number of cells in the battery pack exceeds the number of sampling channels of a single AFE, multiple AFEs can be set (refer to...). Figure 4 AFE1 to AFE n As shown, n≥2). Multiple AFEs are connected via a daisy-chain communication system. The voltage, temperature, and discharge equalization current collected by each AFE are passed step-by-step to the first AFE (AFE1), and then AFE1 transmits the data to the MCU through an isolation circuit and a gateway chip. Specifically, the nth AFE transmits the collected voltage and temperature information to the (n-1)th AFE through an isolation circuit, the (n-1)th AFE transmits the collected voltage and temperature information to the (n-2)th AFE through an isolation circuit, and so on, with the second AFE transmitting the collected voltage and temperature information to the first AFE through an isolation circuit. Multiple AFEs can control their respective equalization switches and perform charge and discharge equalization simultaneously without interference. The above method of cascading multiple AFEs solves the problem of the limited number of sampling channels of a single AFE chip (usually no more than 18 strings). When the number of battery cells exceeds the number of sampling channels of a single AFE, cascading multiple AFEs can flexibly expand the number of sampling channels to meet the equalization requirements of large-scale battery packs. The AFE chip can be Analog Devices' LT8306, NXP's BMA7318, or BYD's BF8915, etc. Those skilled in the art can select the appropriate AFE chip model based on actual application requirements. Communication between AFEs uses daisy-chain communication, and the isolation circuit uses either transformer isolation or capacitor isolation. Each AFE has a corresponding voltage conversion circuit, drawing power from the battery pack to supply the I / O expansion chips, differential amplifiers, and switch drive voltages connected to it. This scheme, where each AFE has its own independent voltage conversion circuit, allows each AFE to draw power independently from the battery pack, avoiding voltage fluctuations caused by long transmission paths or load changes when a single power source supplies power to multiple AFEs, thus ensuring the power supply stability of each AFE and its surrounding circuits.

[0048] Reference Figure 5 As shown, the overall working principle of the active balancing circuit of the battery pack in this embodiment is as follows: When balancing is required, the AFE first collects the voltage and temperature of each cell and transmits them to the MCU through the isolation circuit and gateway chip. The MCU determines whether there is an abnormality based on the received voltage and temperature. If there is an abnormality, it reports to the host computer or main controller through the CAN communication interface; if there is no abnormality, it determines the cell with the highest voltage as the target cell for discharge balancing or the cell with the lowest voltage as the target cell for charge balancing. After determining the target cell and balancing direction, the AFE controls the corresponding switch in the matrix switch to close through the I / O expansion chip, connecting the target cell to the balancing circuit. Taking the nth cell as an example, switches Qn and Qn+1 in the matrix switch are closed, and the remaining switches are open. At the same time, the AFE controls the corresponding switch in the polarity conversion switch to close through the I / O expansion chip, adjusting the polarity of the target cell to be consistent with the preset polarity of the active balancing module. If positive polarity is required for connection, switches K1 and K4 are closed, and K2 and K3 are open; if reverse polarity is required, switches K2 and K3 are closed, and K1 and K4 are open. After the target cell is connected, the MCU controls the controllable switches in the active balancing module to perform balancing. For discharge balancing, the MCU controls the first controllable switch S1 to turn on (S2 to turn off), and the energy of the target cell is transferred from the high-voltage side of the transformer to the low-voltage side, where it is absorbed by the DC source to achieve discharge balancing. For charging balancing, the MCU controls the second controllable switch S2 to turn on (S1 to turn off), and the energy of the DC source is transferred from the low-voltage side of the transformer to the high-voltage side, replenishing the target cell to achieve charging balancing. S1 and S2 are not turned on simultaneously to avoid a short circuit caused by direct connection between the high-voltage side and the low-voltage side. During the balancing process, the sampling module collects the balancing current in real time for closed-loop control. During discharge equalization, a discharge equalization current flows through the first sampling resistor R1. The differential amplifier samples the first voltage drop across R1 to determine the discharge equalization current and sends it to the AFE. During charge equalization, a charge equalization current flows through the second sampling resistor R2. The MCU samples the second voltage drop across R2 to determine the charge equalization current. The MCU determines whether the target cell has completed equalization based on the equalization current (e.g., completion is determined when the current decreases to a preset threshold). If not, equalization continues; if completed, the corresponding controllable switch is disconnected, ending the equalization process. The coordinated operation of these modules achieves a complete equalization process from cell status identification, target cell selection, polarity matching, equalization execution to closed-loop termination. Specifically, the matrix switch and polarity conversion switch ensure that cells in any series position can be selected and connected to the equalization circuit with the correct polarity; the transformer, along with a controllable switch on both the high-voltage and low-voltage sides, enables bidirectional energy transfer; the sampling resistors on the high-voltage and low-voltage sides enable independent detection of the charge and discharge currents; and the coordinated control of the MCU and AFE achieves complete control logic for anomaly detection, target selection, closed-loop adjustment, and equalization termination.

[0049] Reference Figure 6 As shown in the figure, this application embodiment also provides a battery pack active balancing control method, which can be applied to the aforementioned battery pack active balancing circuit, including the following steps: Step S1: Obtain the voltage information of multiple cells in the battery pack. Specifically, this can be achieved by simulating a front-end chip to collect the voltage of each cell and transmit it to the microcontroller unit.

[0050] Step S2: Based on the voltage information, determine the target cell from the multiple cells that needs to be balanced.

[0051] Step S3: Control the matrix switch module to select the target cell and control the polarity conversion module to adjust the polarity of the target cell to match the preset polarity of the active balancing module.

[0052] Step S4: Control the controllable switch in the active balancing module to conduct the charge and discharge balancing of the target cell through the active balancing module.

[0053] In the above method, obtaining voltage information in step S1 is a continuous process, not just executed once at the beginning of the process. The battery pack active balancing control method provided in this application embodiment can be applied to the battery pack active balancing control circuit provided in any embodiment of this application, and has the beneficial effects that the corresponding functional modules of the circuit can achieve. Further effects of the above steps are the same as those in the corresponding embodiments above, and will not be repeated here.

[0054] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A battery pack active balancing circuit, characterized in that, include: The battery pack connection terminal is configured to connect to a battery pack consisting of multiple cells connected in series. A matrix switch module is connected to the battery pack connection terminal and configured to select a target cell in the battery pack. A polarity conversion module, connected to the matrix switch module, is configured to adjust the output polarity of the target battery cell to a preset direction; An active balancing module, connected to the polarity conversion module, is configured to perform charge and discharge energy transfer on the target battery cell; The sampling control module is connected to the matrix switch module, the polarity conversion module and the active balancing module. It is configured to collect the voltage information of each cell in the battery pack, collect the balancing current of the active balancing module, and control the selection and polarity switching of the matrix switch module and the polarity conversion module according to the voltage information, and control the active balancing module to perform charge and discharge balancing on the target cell. as well as A voltage conversion circuit is provided, with its input terminal connected to the battery pack connection terminal and its output terminal connected to the sampling control module. The circuit is configured to draw power from the battery pack and convert it into the operating voltage required by the sampling control module.

2. The battery pack active balancing circuit according to claim 1, characterized in that, The active balancing module includes: The transformer has a high-voltage side and a low-voltage side, wherein the high-voltage side is used to connect the battery pack and the low-voltage side is used to connect a DC source; A first controllable switch is located on the high-voltage side and configured to, when turned on, cause the battery pack to release energy to the low-voltage side through the transformer in order to achieve discharge balance. The second controllable switch is located on the low-voltage side and is configured to allow the DC source to replenish energy to the battery pack through the transformer when it is turned on, so as to achieve charging balance. The first controllable switch and the second controllable switch are not turned on at the same time.

3. The battery pack active balancing circuit according to claim 1, characterized in that, The sampling control module includes: The first sampling resistor is located on the high-voltage side of the transformer and is configured to allow the discharge equalization current to flow through it and generate a first voltage drop across the first sampling resistor. The second sampling resistor is located on the low-voltage side of the transformer and is configured to allow the charging equalization current to flow through it and generate a second voltage drop across the second sampling resistor. A differential amplifier, wherein the two input terminals of the differential amplifier are respectively connected to the two ends of the first sampling resistor, and is configured to collect the first voltage drop to determine the discharge equalization current; An analog front-end chip is connected to the battery pack connection terminal and configured to collect the voltage and temperature of each cell; the analog front-end chip is also connected to the output terminal of the differential amplifier and configured to receive the discharge equalization current. A microcontroller unit is connected to both ends of the second sampling resistor and configured to acquire the voltage across the second sampling resistor to determine the charging equalization current; the microcontroller unit is also connected to the control terminals of the first controllable switch and the second controllable switch and configured to control the conduction and cutoff of the first controllable switch and the second controllable switch; the microcontroller unit is also connected to the analog front-end chip and configured to receive the voltage and the temperature.

4. The battery pack active balancing circuit according to claim 3, characterized in that, The sampling control module further includes: An isolation circuit, connected to the analog front-end chip, is configured to achieve electrical isolation between the analog front-end chip and the microcontroller unit; A gateway chip, connecting the isolation circuit and the microcontroller unit, is configured to convert the SPI communication of the microcontroller unit into daisy-chain communication of the analog front-end chip; The analog front-end chip transmits the voltage, temperature, and discharge equalization current to the microcontroller unit through the isolation circuit and the gateway chip.

5. The battery pack active balancing circuit according to claim 3, characterized in that, The microcontroller includes a CAN communication interface, configured to communicate with a host computer or main controller; The microcontroller unit is also configured to: The presence of any abnormalities is determined based on the voltage and temperature collected by the analog front-end chip. In the event of an abnormal situation, the abnormal situation will be reported to the host computer or main controller through the CAN communication interface; In the absence of any abnormal conditions, the cell with the highest voltage among the multiple cells is determined as the target cell for discharge balancing, or the cell with the lowest voltage is determined as the target cell for charge balancing, based on the voltage.

6. The battery pack active balancing circuit according to claim 3, characterized in that, The sampling control module further includes: The I / O expansion chip is connected to the matrix switch module and the polarity conversion module; The analog front-end chip is connected to the matrix switch module and the polarity conversion module through the I / O expansion chip, and is configured to drive the switching actions in the matrix switch module and the polarity conversion module through the I / O expansion chip.

7. The battery pack active balancing circuit according to claim 1, characterized in that, The matrix switch module includes: There are N+1 selector switches, where N is the number of battery cells. The N+1 selector switches are connected in series. The common connection point between each pair of adjacent battery cells is connected to the common terminal between the two adjacent selector switches, so that each pair of adjacent battery cells shares one selector switch.

8. The battery pack active balancing circuit according to claim 1, characterized in that, The polarity conversion module includes: Four switching switches form a bridge circuit. The two pairs of arms of the bridge circuit are respectively connected to the positive and negative terminals of the target battery cell. The bridge circuit is configured to adjust the polarity of the target battery cell to match the preset polarity of the active balancing module by opening and closing different pairs of arms in the bridge circuit.

9. The battery pack active balancing circuit according to claim 3, characterized in that, The analog front-end chip is provided in multiple ways, and the multiple analog front-end chips are connected to each other via daisy chain communication. Each of the analog front-end chips is equipped with a corresponding voltage conversion circuit.

10. The battery pack active balancing circuit according to claim 5, characterized in that, The microcontroller unit is also configured to: During the discharge equalization process, the discharge equalization current is used to determine whether the target cell has completed discharge equalization. If the discharge equalization has not been completed, the active equalization module is controlled to continue to perform discharge equalization on the target cell. During the charging equalization process, the charging equalization current is used to determine whether the target cell has completed charging equalization. If charging equalization has not been completed, the active equalization module is controlled to continue charging equalization of the target cell.

11. A battery pack active balancing control method, characterized in that, include: Obtain voltage information of multiple cells in the battery pack; Based on the voltage information, the target cell that needs to be balanced is determined from the multiple battery cells; The control matrix switch module selects the target battery cell and controls the polarity conversion module to adjust the polarity of the target battery cell to match the preset polarity of the active balancing module; The controllable switch in the active balancing module is turned on to perform charging or discharging balancing on the target cell through the active balancing module.

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