Layered inductance energy storage bidirectional lossless lithium battery cell equalization hardware circuit

Abstract

The application discloses a layered inductance energy storage bidirectional lossless lithium battery monomer equalization hardware circuit, which comprises a battery connection module, a bidirectional switch matrix, a layered inductance energy storage module, a hardware voltage sampling comparison module and a switch driving module, wherein the layered inductance energy storage module comprises a primary common energy storage inductance and a plurality of secondary distributed transfer inductances. The hardware voltage sampling comparison module is used for identifying a battery to be released and a battery to be supplemented, and controls the bidirectional switch matrix through the switch driving module, so that the electric energy of the battery to be released is transferred to the battery to be supplemented through the layered inductance energy storage module, and bidirectional energy equalization between different batteries is realized. The circuit is also provided with a current limiting protection module, a voltage self-locking protection module, an optical coupling isolation driving module and an auxiliary power supply module, which can reduce equalization energy loss, improve equalization response speed and operation safety.

Description

Technical Field

[0001] This invention relates to the field of lithium battery management technology, specifically to a layered inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit. Background Technology

[0002] Lithium-ion batteries are characterized by high energy density, long cycle life, and wide application range, and are widely used in energy storage power supplies, electric vehicles, portable electrical devices, and home energy storage devices. In actual use, to obtain a higher output voltage, multiple lithium-ion battery cells are usually connected in series to form a battery pack. However, different cells objectively have differences in parameters such as capacity, internal resistance, and self-discharge rate during the manufacturing process. With long-term repeated charging and discharging of the battery pack, the voltage difference between the cells will gradually increase. When the voltage of some cells is too high, they are prone to reaching the overvoltage protection threshold prematurely during charging, causing the entire battery pack to stop charging, thus preventing other cells from being fully charged. When the voltage of some cells is too low, they are prone to reaching the undervoltage protection threshold prematurely during discharging, causing the battery pack to stop discharging prematurely, resulting in a decrease in the usable capacity of the battery pack. Long-term exposure to a large voltage difference between cells will also accelerate the aging of some cells and increase the risk of cell swelling and thermal runaway. Therefore, it is necessary to adjust the state of charge of each cell in the series-connected battery pack through a cell balancing circuit.

[0003] Existing lithium battery balancing technologies mainly include passive resistor balancing, single-inductor adjacent active balancing, and multi-winding transformer active balancing. Passive resistor balancing typically involves placing power discharge resistors and switching devices at both ends of each cell. When a cell's voltage is detected to be too high, the excess energy of that cell is dissipated as heat by activating the corresponding branch. While this method has a relatively simple circuit structure, it suffers from significant energy loss and generates noticeable heat during the balancing process. In large-capacity or high-current battery packs, appropriate heat dissipation structures are required, reducing the overall energy utilization rate of the battery pack.

[0004] Single-inductor adjacent active balancing utilizes energy storage inductors and switching devices to transfer energy between adjacent cells, reducing energy loss caused by resistive discharge. However, its energy transfer range is mainly limited to adjacent cells. When there are multiple cells between a higher-voltage cell and a lower-voltage cell, energy needs to be transferred step by step through multiple adjacent cells. This results in a longer energy transfer path, more switching operations, and a longer time to repair voltage differences between cells over long distances. Furthermore, it is prone to large voltage fluctuations under high-current operating conditions, making it difficult to meet the rapid dynamic balancing requirements of fast charging and large-capacity energy storage devices.

[0005] Active balancing using multi-winding transformers achieves energy transfer between multiple cells through magnetic coupling. While this can improve balancing speed to some extent, it requires designing transformers with multiple windings to accommodate the number of cells. This results in complex and bulky magnetic components, leading to high procurement and manufacturing costs. Furthermore, multi-winding transformers suffer from leakage inductance during high-frequency operation, which can cause additional energy losses. This hinders the miniaturization and modularization of balancing circuits and makes direct integration into space-constrained BMS protection boards difficult.

[0006] Furthermore, some existing equalization systems typically rely on the BMS main control MCU to sample the voltage of each cell using an ADC, and then the software completes the voltage comparison, equalization target identification, and switching control. Since data acquisition, program calculation, and control command output all require processing time, equalization control is prone to lag under dynamic operating conditions such as fast charging and rapid load changes. Simultaneously, some equalization circuits lack hardware current limiting and overvoltage / undervoltage latching protection independent of the main control program. When a large transient inrush current occurs during equalization, or when the main control program malfunctions, the equalization branch may not be able to be shut down in time, affecting the operational safety of the cells and the equalization circuit.

[0007] Therefore, it is necessary to provide a hierarchical inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit. By constructing a hierarchical inductor energy storage structure, multiple cells can achieve cross-cell energy transfer through a common energy storage channel. Through hardware voltage sampling and comparison, bidirectional switch control, and hardware protection structure, the cell voltage difference repair speed and energy utilization rate are improved. At the same time, the dependence of the balancing process on the real-time calculation of the main control software is reduced, so as to meet the needs of energy storage power supply, electric vehicle and other multi-string lithium battery devices. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a layered inductor energy storage bidirectional lossless lithium battery cell equalization hardware circuit, which effectively overcomes the shortcomings of existing technologies.

[0009] This invention is achieved through the following technical solution: a layered inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit, comprising:

[0010] A cell connection module is connected to multiple cells in a series battery pack to form equalization branches corresponding to each of the cells.

[0011] A bidirectional switching matrix, connected to multiple equalization branches, includes bidirectional switching units respectively corresponding to each of the battery cells, for selectively establishing bidirectional conductive paths between the corresponding battery cell and the equalization energy channel;

[0012] The layered inductor energy storage module, connected to the bidirectional switch matrix, includes a primary common energy storage inductor and multiple secondary distributed transfer inductors. The primary common energy storage inductor is connected to a common balancing energy channel shared by multiple balancing branches, and is used to receive and temporarily store the energy output from the battery cells to be released. The multiple secondary distributed transfer inductors are respectively connected between the primary common energy storage inductor and the corresponding balancing branch, and are used to store and release energy for the energy transfer between the primary common energy storage inductor and the battery cells to be replenished.

[0013] A hardware voltage sampling and comparison module is connected to multiple battery cells respectively, and is used to acquire the individual voltage of each battery cell and perform hardware comparison of each individual voltage to output equalization control signals corresponding to the battery cells to be released and the battery cells to be replenished.

[0014] A switch driving module is connected between the hardware voltage sampling and comparison module and the bidirectional switch matrix, and is used to drive the corresponding bidirectional switch unit to turn on or off according to the equalization control signal.

[0015] When the bidirectional switching unit corresponding to the cell to be released is turned on, the cell to be released transmits energy to the layered inductor energy storage module through the corresponding balancing branch; when the bidirectional switching unit corresponding to the cell to be replenished is turned on, the layered inductor energy storage module releases energy to the cell to be replenished through the corresponding balancing branch, so as to form a balanced path for energy transfer between the cell to be released and the cell to be replenished via the layered inductor energy storage module.

[0016] As a preferred technical solution, the primary common energy storage inductor serves as a primary energy storage element shared by multiple equalization branches, and the multiple secondary distributed transfer inductors are respectively set for different equalization branches. The primary common energy storage inductor and the multiple secondary distributed transfer inductors together form a hierarchical energy storage structure in which primary common energy storage and secondary distributed energy storage complement each other.

[0017] As a preferred technical solution, the hardware voltage sampling and comparison module includes multiple voltage divider sampling branches and multiple differential operational amplifiers. The multiple voltage divider sampling branches are respectively connected to multiple battery cells. The output terminal of each voltage divider sampling branch is connected to the corresponding differential operational amplifier. The differential operational amplifier is used to generate a differential voltage analog signal characterizing the voltage difference of the battery cells based on the input sampling voltage, and transmit the differential voltage analog signal to the switch drive module.

[0018] As a preferred technical solution, the hardware voltage sampling and comparison module further includes a temperature compensation network, which includes an NTC thermistor and a compensation resistor. The NTC thermistor and the compensation resistor are connected to the voltage divider sampling branch to adjust the sampling voltage output by the voltage divider sampling branch according to temperature changes, so as to compensate for the voltage sampling deviation caused by temperature changes.

[0019] As a preferred technical solution, it also includes a primary current limiting protection unit, which includes a current sampling resistor connected in series in the multiple equalization branches and a current comparator connected to the current sampling resistor. The current comparator is connected to the corresponding bidirectional switching unit and is used to output a shutdown signal when the current of the corresponding equalization branch reaches the preset current limiting condition, so as to shut down the corresponding bidirectional switching unit.

[0020] As a preferred technical solution, a secondary peak current limiting protection unit is also included. The secondary peak current limiting protection unit is located in the equalization energy channel where the primary common energy storage inductor is located, and includes a transient suppression diode and a high-frequency ferrite bead, which are used to suppress transient inrush current in the equalization energy channel.

[0021] As a preferred technical solution, a hardware voltage self-locking protection unit is also included. The hardware voltage self-locking protection unit is connected to the hardware voltage sampling and comparison module, the bidirectional switch matrix and the BMS main controller respectively. It is used to lock the bidirectional switch unit corresponding to any of the battery cells when the voltage of any single cell reaches a preset overvoltage condition or a preset undervoltage condition, and output a fault signal to the BMS main controller.

[0022] As a preferred technical solution, the switch driving module includes multiple optocouplers and multiple totem pole driving circuits. The multiple optocouplers are respectively set for multiple bidirectional switching units. The input terminal of the optocoupler is connected to the hardware voltage sampling and comparison module, and the output terminal of the optocoupler is connected to the bidirectional switching unit through the corresponding totem pole driving circuit, so as to electrically isolate the control loop where the hardware voltage sampling and comparison module is located from the power loop where the equalization branch is located.

[0023] As a preferred technical solution, an auxiliary power supply module is also included. The input terminal of the auxiliary power supply module is connected to the total voltage terminal of the series battery pack, and the output terminal of the auxiliary power supply module is connected to the hardware voltage sampling and comparison module and the switch drive module respectively. The auxiliary power supply module includes an isolated DC-DC power supply circuit and a soft-start circuit, which are used to convert the total voltage of the series battery pack into the low-voltage DC power required by the hardware voltage sampling and comparison module and the switch drive module.

[0024] As a preferred technical solution, the auxiliary power supply module further includes an input reverse connection protection circuit and an output short circuit protection circuit; the bidirectional switch matrix and the layered inductor energy storage module are set in the power balancing area of ​​the PCB board, the hardware voltage sampling comparison module is set in the low voltage sampling area of ​​the PCB board, the power balancing area and the low voltage sampling area are spaced apart, and a grounding isolation area is provided between the power balancing area and the low voltage sampling area.

[0025] The beneficial effects of this invention are as follows: This invention employs a hierarchical inductor energy storage structure formed by a primary common energy storage inductor and multiple secondary distributed transfer inductors, and connects the balancing branches corresponding to multiple battery cells to the balancing energy channel through a bidirectional switch matrix. Battery cells with higher voltage can first transfer excess energy to the hierarchical inductor energy storage module, and then the hierarchical inductor energy storage module releases energy to the battery cells needing replenishment. This enables cross-level energy transfer between battery cells in different locations, reducing the need for multiple battery cells to be transferred sequentially in traditional single-inductor adjacent balancing, thus shortening the battery cell voltage difference repair path and improving the balancing speed.

[0026] This invention utilizes a primary common energy storage inductor to centrally buffer large amounts of energy, and a secondary distributed transfer inductor to complete energy transfer and replenishment between different balancing branches. This allows for the coordinated completion of large energy transfer and small voltage drop compensation within a layered energy storage structure. During the balancing process, there is no need to continuously discharge excess charge from the high-voltage cells using power resistors, reducing energy loss as heat. This helps lower the heat generation of the balancing circuit, improves the energy utilization rate of the battery pack, and alleviates the heat dissipation design pressure of large-capacity battery systems.

[0027] This invention incorporates a hardware voltage sampling and comparison module. Through a voltage divider sampling branch and a differential operational amplifier, it directly samples and compares the individual voltages of each battery cell. Based on the voltage difference comparison results, it provides an equalization control signal to the switch drive module, enabling the bidirectional switch matrix to switch the corresponding equalization branch in a timely manner. Compared to methods that rely entirely on the MCU for voltage sampling, software calculation, and control output, this reduces the impact of software computation on the equalization response speed, making it more suitable for real-time cell equalization in fast charging and dynamically changing load scenarios.

[0028] This invention compensates for the cell voltage sampling process through a temperature compensation network, which can reduce the impact of ambient temperature changes and cell temperature changes on the sampling results, thereby improving the stability of hardware differential voltage judgment, reducing erroneous equalization triggers caused by temperature changes, and improving the reliability of cell equalization control under different environmental conditions.

[0029] This invention forms a first-level current-limiting protection by using a current sampling resistor and a current comparator in the equalization branch, and forms a second-level peak current-limiting protection by setting a transient suppression diode and a high-frequency ferrite bead in the common energy storage channel. It limits the equalization current from two levels: the equalization current of the branch and the transient impact of the common energy storage channel. This helps to reduce the impact of the inrush current generated during switching and energy transfer on the battery cell and switching devices.

[0030] This invention also includes a hardware voltage self-locking protection unit. When a cell reaches a preset overvoltage or undervoltage condition, it can directly lock the corresponding bidirectional switching unit and output a fault signal, causing the relevant equalization branch to stop working. This protection process can operate independently of the normal program of the BMS main control. Even if the main control program malfunctions, it can still provide hardware protection for abnormal cells, improving the safety and fault tolerance of the entire equalization system.

[0031] This invention sets up an optocoupler isolator and a totem pole drive circuit between the hardware voltage sampling and comparison module and the bidirectional switch matrix, so as to form electrical isolation between the low-voltage sampling control circuit and the cell power balancing circuit, and can provide fast turn-on and turn-off drive for the bidirectional switch unit, which helps to reduce the interference of the power circuit to the sampling and comparison circuit, and at the same time reduce the additional losses during the switching process of the switching devices.

[0032] This invention employs an isolated auxiliary power supply structure to provide low-voltage DC power to the hardware voltage sampling and comparison module and the switch drive module. It also improves the stability of the auxiliary power supply process through soft start, input reverse connection protection, and output short circuit protection. At the same time, the power equalization area and the low-voltage sampling area are arranged in separate areas on the PCB board, and a grounding isolation area is set up. This helps to reduce electromagnetic interference generated by high-frequency switching, and allows the equalization circuit to be integrated into the BMS protection board with a smaller PCB area, thereby improving the miniaturization and modularity of the circuit. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a block diagram of the overall structure of the layered inductor energy storage bidirectional lossless lithium battery cell equalization hardware circuit of the present invention.

[0035] Figure 2 This is a schematic diagram of the equalization main topology and hierarchical current limiting protection circuit of the layered inductor energy storage bidirectional lossless lithium battery cell equalization hardware circuit of the present invention. Detailed Implementation

[0036] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0037] Any feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by other equivalent or similar features for a similar purpose, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0038] Reference Figure 1 and Figure 2 This embodiment provides a hierarchical inductive energy storage bidirectional lossless lithium battery cell balancing hardware circuit, mainly applied to battery packs formed by multiple lithium battery cells connected in series. It can be used in conjunction with a battery management system (BMS) to dynamically balance the voltage differences between cells during charging, discharging, and resting states of the battery pack. This balancing hardware circuit mainly includes a cell connection module, a bidirectional switch matrix, a hierarchical inductive energy storage module, a hardware voltage sampling and comparison module, a switch drive module, a primary current limiting protection unit, a secondary peak current limiting protection unit, a hardware voltage self-locking protection unit, and an auxiliary power supply module. These modules are connected via hardware circuitry, enabling cell voltage identification, balancing branch selection, energy transfer, current limiting protection, and abnormal self-locking to be independently completed by the hardware circuitry, thereby reducing reliance on the real-time calculation process of the BMS main control software.

[0039] In this embodiment, the cell connection module is connected to multiple cells in the series-connected battery pack. Each cell is provided with a corresponding balancing branch. One end of each balancing branch is connected to the corresponding cell, and the other end is connected to a bidirectional switch matrix, so that each cell can independently connect to the subsequent balancing energy channel. The series-connected battery pack can use different numbers of cells connected in series according to the actual equipment needs. The circuit structure of this embodiment can be applied to 3-cell to 24-cell lithium battery packs, and can be further adapted to energy storage power supplies, two-wheeled electric vehicle battery packs, household energy storage battery packs, and other devices using series-connected lithium battery packs with different voltage levels such as 12V, 24V, 48V, and 72V. Since each cell is connected to the balancing system through its corresponding balancing branch, the balancing process does not need to be limited to two adjacent cells, but can select the cells that need to release energy and the cells that need to replenish energy based on the real-time voltage status of each cell.

[0040] A bidirectional switch matrix is ​​positioned between each balancing branch and the hierarchical inductor energy storage module. The matrix includes bidirectional switch units corresponding to each battery cell, each constructed using MOS switching devices and capable of selectively turning on or off based on the drive signal output from the switch drive module. When each bidirectional switch unit is on, a conductive path for energy transfer is formed between the corresponding battery cell and the balancing energy channel; when the bidirectional switch unit is off, the corresponding battery cell is disconnected from the balancing energy channel. By combining and controlling different bidirectional switch units, charging paths can be formed from the battery cell to be released energy to the hierarchical inductor energy storage module, and discharging paths can be formed from the hierarchical inductor energy storage module to the battery cell to be replenished energy. Since each battery cell can establish a connection with the common balancing energy channel through the bidirectional switch matrix, high-voltage and low-voltage cells can transfer energy through the hierarchical inductor energy storage module even if they are not adjacent, without needing to transfer energy section by section according to the cell arrangement order.

[0041] The hierarchical inductor energy storage module is the main energy transfer part of this embodiment, including a primary common energy storage inductor L1 and multiple secondary distributed transfer inductors L2 to Ln. The primary common energy storage inductor L1 is set in the equalization energy channel shared by multiple equalization branches, serving as a primary energy storage element shared by all cells. It is used to receive and temporarily store the electrical energy output from the higher-voltage cells to be released. The multiple secondary distributed transfer inductors are respectively set for different equalization branches and connected between the primary common energy storage inductor and the corresponding equalization branch. After the primary common energy storage inductor completes the main energy buffering, it is used to further store, release, and finely compensate the energy transfer between the primary common energy storage inductor and the cells to be replenished, thereby forming a hierarchical inductor energy storage structure that combines primary common energy storage and secondary distributed energy storage. In this embodiment, the structure is explicitly defined as a hierarchical common inductor array consisting of a primary common energy storage inductor L1 and secondary distributed transfer inductors L2 to Ln. The primary common energy storage inductor serves as a large-capacity energy buffer, while the secondary distributed transfer inductors are used for fine-tuning energy replenishment under small voltage differences.

[0042] During the balancing process, the hardware voltage sampling and comparison module first detects the individual voltage of each cell in real time and identifies the cell with the higher voltage to be released and the cell with the lower voltage to be replenished from among multiple cells. The switch drive module first controls the bidirectional switch unit corresponding to the cell to be released to turn on, so that the cell releases energy to the primary common energy storage inductor L1 through the corresponding balancing branch. The current in the primary common energy storage inductor L1 gradually builds up and stores electromagnetic energy. When the corresponding energy transfer conditions are reached, the bidirectional switch unit corresponding to the cell to be released turns off, and at the same time, the bidirectional switch unit corresponding to the cell to be replenished turns on. The energy stored in the primary common energy storage inductor L1 is released to the cell to be replenished through the corresponding secondary distributed transfer inductor. Through the above charging and discharging process, a cross-cell balancing energy transfer path can be formed between two cells in different series positions, thereby avoiding the problem of traditional single-inductor adjacent balancing methods that require multiple intermediate cells for step-by-step transfer. For the remaining small voltage difference, a small amount of energy can be stored and released by a secondary distributed transfer inductor, so that the target cell can receive precise energy replenishment.

[0043] The hardware voltage sampling and comparison module includes multiple voltage divider sampling branches and multiple differential operational amplifiers. Each voltage divider sampling branch is connected to a corresponding battery cell, converting the individual cell voltage into a sampling voltage suitable for processing by the differential operational amplifier. The voltage divider sampling branches can be constructed using low-temperature-drift voltage divider resistors to reduce the impact of resistor temperature drift on the sampling results. The output of each voltage divider sampling branch is connected to the input of the corresponding differential operational amplifier, and the multiple differential operational amplifiers together form a hardware differential voltage judgment network. The differential operational amplifier directly compares the sampling voltages corresponding to different battery cells and outputs a differential voltage analog signal characterizing the voltage difference between the battery cells. This differential voltage analog signal does not need to be sent to the BMS main control for software calculation; it can be directly transmitted to the switch drive module to drive the corresponding bidirectional switch unit to switch. In this embodiment, the signal response time of the hardware differential voltage judgment network can be controlled within 0.8ms, thereby reducing the processing delay caused by using an MCU to perform ADC sampling, data processing, and control output.

[0044] To further improve voltage sampling stability under different ambient temperatures, the hardware voltage sampling and comparison module also includes a temperature compensation network. This network comprises an NTC thermistor and a compensation resistor, which are connected to the corresponding voltage divider sampling branch. The resistance of the NTC thermistor changes with temperature, thus providing compensation to the voltage divider sampling branch based on the ambient temperature of the battery cell, correcting voltage division errors caused by temperature variations. In one specific implementation parameter of this embodiment, the temperature compensation network enables the circuit to maintain a relatively stable voltage sampling state within an ambient temperature range of -20℃ to 60℃, with the voltage sampling error controlled within 2mV. This reduces erroneous triggering of the equalization circuit due to changes in the battery cell's internal resistance or temperature drift of the sampling components under low-temperature conditions.

[0045] A switch driver module is connected between the hardware voltage sampling and comparison module and the bidirectional switch matrix. It converts the equalization control signal generated by the hardware voltage sampling and comparison module into a drive signal suitable for use by the bidirectional MOS switch unit. The switch driver module includes multiple optocouplers and multiple totem-pole drive circuits, with each bidirectional switch unit corresponding to an optocoupler. The input of the optocoupler is connected to the hardware voltage sampling and comparison module, and the output is connected to the corresponding totem-pole drive circuit. The totem-pole drive circuit then connects to the control terminal of the bidirectional switch unit, thus creating electrical isolation between the low-voltage sampling control loop and the cell-side power equalization loop. The optocoupler can block the transmission of high-frequency interference generated by power-side switching operations to the sampling and comparison side. The isolation impedance of the optocoupler isolation structure used in this embodiment can reach over 1000MΩ. The totem-pole drive circuit can quickly provide charging drive current when the bidirectional MOS switch unit is turned on and quickly release the control terminal charge when turned off, thereby improving the turn-on and turn-off speed of the MOS switch device, reducing additional losses during switching, and reducing electromagnetic interference generated by high-frequency switching.

[0046] Each balancing branch is also equipped with a primary current-limiting protection unit. The primary current-limiting protection unit includes a manganin current sampling resistor connected in series in the corresponding balancing branch and a current comparator connected to the current sampling resistor. When the balancing current flows through the manganin current sampling resistor, a sampling voltage corresponding to the balancing current is generated across the resistor. The current comparator compares this sampling voltage in real time. When the current in the balancing branch reaches a preset primary current-limiting threshold, the current comparator immediately outputs a shutdown signal to the corresponding bidirectional switching unit or its drive circuit, causing the balancing branch to stop transmitting power. In one specific embodiment, the primary current-limiting threshold can be set to 3A. That is, when the balancing current exceeds 3A, the hardware current comparator directly shuts off the corresponding branch MOS without waiting for the BMS main control program to make a current-limiting judgment, thereby improving the response speed during the high-current balancing process.

[0047] In addition to the primary current-limiting protection units installed in each balancing branch, a secondary peak current-limiting protection unit is also installed in the balancing energy channel where the primary common energy storage inductor L1 is located. The secondary peak current-limiting protection unit includes a TVS transient voltage suppressor diode and a high-frequency ferrite bead. The TVS transient voltage suppressor diode is used to quickly conduct and clamp the transient energy when a high transient voltage is generated during switching or power-on. The high-frequency ferrite bead is used to attenuate the high-frequency impact component, thereby reducing the transient inrush current in the common energy channel where the primary common energy storage inductor is located. The primary current-limiting protection unit mainly detects and shuts off continuous overcurrent in the branch during normal balancing, while the secondary peak current-limiting protection unit mainly suppresses peak impacts formed during switching and power-on. Together, they constitute a graded current-limiting protection structure to reduce the adverse effects of inrush current on the cell tabs, diaphragm, energy storage inductor, and MOS switching devices.

[0048] This embodiment also includes a hardware voltage self-locking protection unit, which is connected to the hardware voltage sampling and comparison module, the bidirectional switch matrix, and the BMS main control. The hardware voltage self-locking protection unit can determine whether a cell is in an overvoltage or undervoltage state based on the cell voltage status detected by the hardware voltage sampling and comparison module. When the voltage of any single cell reaches a preset overvoltage or undervoltage condition, the hardware voltage self-locking protection unit directly locks the corresponding bidirectional switch unit, causing the cell to exit the equalization energy transfer path, and simultaneously outputs a fault level to the BMS main control, so that the BMS main control can control the battery pack's total charging circuit or total discharging circuit according to the fault level. In this embodiment, a single cell voltage greater than 4.25V can be set as an overvoltage self-locking condition, and a single cell voltage less than 2.5V can be set as an undervoltage self-locking condition. When the above states occur, the corresponding equalization branch is directly locked by the hardware circuit, thus making the protection function independent of whether the software program executes normally. Even if the BMS main control experiences a program freeze or abnormal reset, the cell equalization branch can still maintain a hardware shutdown state.

[0049] The auxiliary power supply module provides a stable operating power supply for the hardware voltage sampling and comparison module, optocoupler isolator, totem-pole driver circuit, current comparator, and other low-voltage control devices. The input terminal of the auxiliary power supply module is connected to the total voltage terminal of the series battery pack. Internally, it incorporates an isolated wide-voltage DC-DC power supply circuit to convert the total battery pack voltage into a stable DC voltage suitable for the low-voltage hardware circuitry. In this embodiment, the input voltage range of the isolated wide-voltage DC-DC power supply circuit can be set from 12V to 96V, and it can output two low-voltage DC power supplies of 3.3V and 5V to meet the power supply needs of different operational amplifiers, comparators, optocouplers, and driver devices. The auxiliary power supply module also includes a soft-start circuit, allowing the output voltage to gradually build up after power-on, preventing a rapid voltage jump at power-on that could impact low-voltage devices.

[0050] To improve the operational reliability of the auxiliary power supply section, the auxiliary power supply module is also equipped with an input reverse connection protection circuit and an output short-circuit protection circuit. The input reverse connection protection circuit uses a reverse connection protection diode placed on the input side of the DC-DC power supply circuit to prevent reverse current from entering the auxiliary power supply module when the power supply polarity is incorrect. The output short-circuit protection circuit uses a self-resetting short-circuit protection device to limit the fault current when an abnormal short circuit occurs on the output side of the auxiliary power supply module and restore normal power supply after the short-circuit fault is cleared. Through the coordination of soft start, input reverse connection protection, and output short-circuit protection, the auxiliary power supply module can provide stable power to the entire equalization hardware circuit over a wide range of the battery pack's total voltage.

[0051] In terms of PCB layout, the bidirectional switch matrix and layered inductor energy storage module are located in the power balancing area of ​​the PCB, while the hardware voltage sampling and comparison module is located in the low-voltage sampling area. A physical separation is maintained between the power balancing area and the low-voltage sampling area, and a grounding isolation area or grounding isolation trench is provided between them to reduce electromagnetic coupling interference from high-frequency, high-current switching signals in the power balancing area to the low-voltage sampling area. Furthermore, the main balancing topology, hardware voltage sampling and comparison module, current limiting and self-locking protection section, and auxiliary power supply section can all form relatively independent functional areas, enabling each functional module to independently complete surface mount production and testing. In this embodiment, the physical partitioning of the high-voltage balancing branch and the low-voltage sampling circuit, along with the intermediate grounding isolation trench, significantly attenuates external electromagnetic interference.

[0052] In this embodiment, both the primary common energy storage inductor and the secondary distributed transfer inductor can be general-purpose surface-mount power inductors. The bidirectional switch matrix, hardware differential voltage sampling and comparison module, protection unit, and auxiliary power supply module can also be constructed using standardized discrete components. This eliminates the need for multi-winding transformers specifically wound for a particular number of battery cells, thus reducing the PCB area occupied by large magnetic components and facilitating modular mass production using existing SMT assembly lines. Compared to balancing solutions using custom multi-winding transformers, the overall material cost can be reduced by approximately 35%, and the PCB area of ​​the balancing circuit can be reduced by approximately 42%, making it more suitable for direct integration into space-constrained BMS protection boards.

[0053] During actual operation, when the series-connected battery pack is charging, if a cell's voltage is higher than other cells due to differences in capacity, internal resistance, or state of charge, the hardware voltage sampling and comparison module continuously monitors the voltage of that cell and other cells. A hardware voltage difference judgment network composed of differential operational amplifiers identifies the relatively high-voltage and relatively low-voltage cells. Based on this hardware comparison result, the switch drive module first drives the bidirectional switch unit corresponding to the high-voltage cell to conduct, allowing some of the high-voltage cell's energy to be transferred to the primary common energy storage inductor L1 via the balancing branch. Once the primary common energy storage inductor L1 has completed its energy storage, the bidirectional switch unit corresponding to the high-voltage cell turns off, while the bidirectional switch unit corresponding to the low-voltage cell turns on. The energy stored in the primary common energy storage inductor L1 and the corresponding secondary distributed transfer inductor is then released to the low-voltage cell via the balancing branch. This process is repeated based on the cell voltage difference, ensuring that excess energy released by the high-voltage cell is not converted into heat consumption through the power resistor but is instead transferred and replenished in the low-voltage cell.

[0054] In the discharge state, when the voltage of a certain cell drops faster than that of other cells, the hardware voltage sampling and comparison module can identify this cell as the one needing replenished energy. It then selects other cells with relatively higher voltages as the cells to be released energy, causing the corresponding bidirectional switching unit to operate in the order of energy storage and release, thereby transferring some of the energy from the high-voltage cell to the low-voltage cell. Since any cell can be connected to the primary common energy storage inductor L1 via the bidirectional switching matrix, this energy transfer does not require the two cells to be adjacent, avoiding the problem of multiple transfers required when transferring energy across multiple cells in traditional adjacent balancing methods. In the battery pack's resting state, as long as the hardware voltage sampling and comparison module detects a voltage difference between different cells that meets the balancing conditions, the above balancing process can also be performed. Therefore, this embodiment can continuously perform dynamic cell balancing in charging, discharging, and resting states.

[0055] During the aforementioned equalization process, the primary current-limiting protection unit continuously monitors the operating current of each equalization branch, while the secondary peak current-limiting protection unit simultaneously suppresses transient peaks in the common equalization energy channel. When the current in any equalization branch increases abnormally, the current comparator directly shuts down that equalization branch. When the common energy storage channel experiences transient impacts due to MOS switching or power-on, TVS transient suppression diodes and high-frequency ferrite beads provide further suppression. Simultaneously, the hardware voltage self-locking protection unit continuously monitors whether the cell exceeds the preset overvoltage or undervoltage range. Once an abnormal condition is reached, the corresponding bidirectional switching unit is locked, thus forming a complete hardware closed loop for the equalization process: voltage identification, branch selection, tiered energy storage, cross-cell release, branch current limiting, peak suppression, and abnormal self-locking.

[0056] In this embodiment, by employing the aforementioned layered common inductor energy storage structure, the energy released by the high-voltage cell can directly replenish the low-voltage cell through the common energy storage path, eliminating the need for continuous transfer between adjacent cells. This significantly improves the cross-cell voltage difference repair efficiency compared to traditional single-inductor adjacent balancing schemes. Simultaneously, since no power resistor is used to discharge excess energy, energy conversion loss can be controlled at a low level, within 1.2%, meaning the energy utilization rate can reach approximately 98.8%. The voltage difference judgment network composed of hardware differential operational amplifiers can control the balancing control response time to within 0.8ms, making it suitable for dynamic balancing scenarios where cell voltage changes rapidly during fast charging.

[0057] Furthermore, the circuit in this embodiment can operate under conditions ranging from -20℃ to 60℃ and with ambient humidity from 0% to 95%RH and no condensation. NTC temperature compensation, graded current limiting, hardware overvoltage and undervoltage lockout, optocoupler isolation, and PCB high / low voltage partitioning collectively improve the circuit's stability under high / low temperature and high-current conditions. Under continuous dynamic equilibrium conditions, the voltage difference between individual cells can be maintained within a small range, thereby reducing the probability of some cells being in an overcharged or over-discharged state for extended periods. In this embodiment, under appropriate test conditions, the voltage difference between individual cells can be stably controlled within ±5mV, improving the consistency of the operating state of each cell in the series-connected battery pack.

[0058] Therefore, in this embodiment, multiple series-connected cells are connected to corresponding balancing branches through a cell connection module. The selection of balancing objects and energy transfer directions is completed through a bidirectional switching matrix. A hierarchical energy storage and release path is formed through a primary common energy storage inductor and multiple secondary distributed transfer inductors. The cell voltage difference is directly identified through a hardware voltage sampling and comparison module. The bidirectional switching unit is driven by optocoupler isolation and a totem pole drive structure. A multi-level protection system independent of the main control software is formed by primary branch current limiting, secondary peak suppression, and overvoltage and undervoltage hardware self-locking. This enables low-loss and fast bidirectional energy transfer between cells in different series positions, while taking into account the requirements of balancing response speed, circuit miniaturization, hardware safety protection, and BMS integration application.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A layered inductive energy storage bidirectional lossless lithium battery cell balancing hardware circuit, characterized in that, include: A cell connection module is connected to multiple cells in a series battery pack to form equalization branches corresponding to each of the cells. A bidirectional switching matrix, connected to multiple equalization branches, includes bidirectional switching units respectively corresponding to each of the battery cells, for selectively establishing bidirectional conductive paths between the corresponding battery cell and the equalization energy channel; The layered inductor energy storage module, connected to the bidirectional switch matrix, includes a primary common energy storage inductor and multiple secondary distributed transfer inductors. The primary common energy storage inductor is connected to a common balancing energy channel shared by multiple balancing branches, and is used to receive and temporarily store the energy output from the battery cells to be released. The multiple secondary distributed transfer inductors are respectively connected between the primary common energy storage inductor and the corresponding balancing branch, and are used to store and release energy for the energy transfer between the primary common energy storage inductor and the battery cells to be replenished. A hardware voltage sampling and comparison module is connected to multiple battery cells respectively, and is used to acquire the individual voltage of each battery cell and perform hardware comparison of each individual voltage to output equalization control signals corresponding to the battery cells to be released and the battery cells to be replenished. A switch driving module is connected between the hardware voltage sampling and comparison module and the bidirectional switch matrix, and is used to drive the corresponding bidirectional switch unit to turn on or off according to the equalization control signal. When the bidirectional switching unit corresponding to the cell to be released is turned on, the cell to be released transmits energy to the layered inductor energy storage module through the corresponding balancing branch; when the bidirectional switching unit corresponding to the cell to be replenished is turned on, the layered inductor energy storage module releases energy to the cell to be replenished through the corresponding balancing branch, so as to form a balanced path for energy transfer between the cell to be released and the cell to be replenished via the layered inductor energy storage module.

2. The layered inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 1, characterized in that, The primary common energy storage inductor serves as a primary energy storage element shared by multiple equalization branches. The multiple secondary distributed transfer inductors are respectively set up for different equalization branches. The primary common energy storage inductor and the multiple secondary distributed transfer inductors together form a hierarchical energy storage structure that combines primary common energy storage and secondary distributed energy storage.

3. The layered inductive energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 1, characterized in that, The hardware voltage sampling and comparison module includes multiple voltage divider sampling branches and multiple differential operational amplifiers. The multiple voltage divider sampling branches are respectively connected to multiple battery cells. The output terminal of each voltage divider sampling branch is connected to the corresponding differential operational amplifier. The differential operational amplifier is used to generate a differential voltage analog signal characterizing the voltage difference of the battery cells based on the input sampling voltage, and transmits the differential voltage analog signal to the switch drive module.

4. The layered inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 3, characterized in that, The hardware voltage sampling and comparison module also includes a temperature compensation network, which includes an NTC thermistor and a compensation resistor. The NTC thermistor and the compensation resistor are connected to the voltage divider sampling branch and are used to adjust the sampling voltage output by the voltage divider sampling branch according to the temperature change to compensate for the voltage sampling deviation caused by the temperature change.

5. The layered inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 1, characterized in that, It also includes a primary current limiting protection unit, which includes a current sampling resistor connected in series in the multiple equalization branches and a current comparator connected to the current sampling resistor. The current comparator is connected to the corresponding bidirectional switching unit and is used to output a shutdown signal when the current in the corresponding equalization branch reaches the preset current limiting condition, so as to shut down the corresponding bidirectional switching unit.

6. The layered inductive energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 5, characterized in that, It also includes a secondary peak current limiting protection unit, which is located in the equalization energy channel where the primary common energy storage inductor is located. The secondary peak current limiting protection unit includes a transient suppression diode and a high-frequency ferrite bead, which are used to suppress transient inrush current in the equalization energy channel.

7. The layered inductor energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 6, characterized in that, It also includes a hardware voltage self-locking protection unit, which is connected to the hardware voltage sampling and comparison module, the bidirectional switch matrix and the BMS main controller respectively. It is used to lock the bidirectional switch unit corresponding to any of the battery cells when the voltage of any single cell reaches a preset overvoltage condition or a preset undervoltage condition, and output a fault signal to the BMS main controller.

8. The layered inductor energy storage bidirectional lossless lithium battery cell equalization hardware circuit according to claim 1, characterized in that, The switch driving module includes multiple optocouplers and multiple totem pole driving circuits. The multiple optocouplers are respectively set for multiple bidirectional switching units. The input terminal of the optocoupler is connected to the hardware voltage sampling and comparison module, and the output terminal of the optocoupler is connected to the bidirectional switching unit through the corresponding totem pole driving circuit, so as to electrically isolate the control loop where the hardware voltage sampling and comparison module is located from the power loop where the equalization branch is located.

9. The layered inductive energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 1, characterized in that, It also includes an auxiliary power supply module, the input of which is connected to the total voltage terminal of the series battery pack, and the output of which is connected to the hardware voltage sampling and comparison module and the switch drive module respectively. The auxiliary power supply module includes an isolated DC-DC power supply circuit and a soft-start circuit, which are used to convert the total voltage of the series battery pack into the low-voltage DC power required by the hardware voltage sampling and comparison module and the switch drive module.

10. The layered inductive energy storage bidirectional lossless lithium battery cell balancing hardware circuit according to claim 9, characterized in that, The auxiliary power supply module also includes an input reverse connection protection circuit and an output short circuit protection circuit; the bidirectional switch matrix and the layered inductor energy storage module are set in the power balancing area of ​​the PCB board, the hardware voltage sampling comparison module is set in the low voltage sampling area of ​​the PCB board, the power balancing area and the low voltage sampling area are spaced apart, and a grounding isolation area is provided between the power balancing area and the low voltage sampling area.

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