Bidirectional active equalization control system and method among multi-section series battery pack monomers

Abstract

This application relates to the field of battery management technology and discloses a bidirectional active balancing control system and its control chip for a multi-cell series-connected battery pack. The system includes a primary-side energy storage terminal, a flyback transformer, a primary-side control chip, a secondary-side control chip, and an optocoupler communication module. The secondary-side control chip integrates N power channel switches and selects between cells to be discharged and cells to be charged via selection signals output from a cell voltage monitoring module. The energy from the cell to be discharged is transferred to the cell to be charged after passing through the flyback transformer and the primary-side energy storage terminal, achieving bidirectional energy transfer between any two cells. This system requires only two control chips to complete the active balancing of a multi-cell battery pack, exhibiting high integration and simplified peripheral circuitry.

Description

Technical Field

[0001] This application relates to the field of battery management technology, and in particular to bidirectional active balancing control technology between individual cells in a multi-cell series battery pack. Background Technology

[0002] With the large-scale application of new energy technologies in electric vehicle power battery systems, residential and commercial photovoltaic energy storage systems, and backup power supplies for communication base stations, large-capacity battery packs composed of multiple lithium-ion battery cells connected in series have become the basic unit for energy storage and power supply in these scenarios. For example, in electric vehicles, power battery packs typically consist of dozens or even hundreds of battery cells connected in series to meet the high voltage requirements of the drive motor; in photovoltaic energy storage systems, series-connected battery packs bear the cyclic load of daytime energy storage and nighttime discharge; in communication base stations, backup power battery packs need to continuously supply power to communication equipment with a stable voltage when the mains power is interrupted. However, due to the inherent differences in manufacturing processes, internal resistance characteristics, self-discharge rates, and aging degradation of battery cells, inconsistencies in voltage and capacity inevitably occur between cells during long-term use. If left unaddressed, this imbalance will continue to worsen with the increase in the number of charge-discharge cycles, resulting in the usable capacity of the entire battery pack being limited to the worst-performing cell, while accelerating the overcharging or over-discharging of individual cells, thereby affecting the overall lifespan and safety of the battery pack.

[0003] To address the aforementioned issues, existing technologies have proposed various active balancing schemes, including multi-winding transformers, switched capacitors, bidirectional DC / DC converters, inductor energy storage, and flyback transformers. However, given the current state of technology, existing solutions still face several unresolved technical problems when applied to the specific application scenarios mentioned above: First, many existing solutions require multiple chips to work together and a large number of external discrete power devices, resulting in low system integration and a sharp increase in control complexity as the number of battery cells increases. Second, some existing solutions can only support energy transfer from individual battery cells to the battery pack or from the battery pack to individual battery cells, but cannot directly establish a bidirectional energy transfer channel between any two battery cells, leading to a circuitous balancing path and increased energy loss. Third, at the control level, existing solutions often lack the means to implement precise closed-loop control of the balancing current on both the charging and discharging sides under electrical isolation conditions, limiting the adjustability and control accuracy of the balancing current. Therefore, there is an urgent need for an active balancing control system and its control method that has higher integration, fewer chips, and can achieve direct bidirectional energy dispatch between any two cells in a multi-cell series battery pack. Summary of the Invention

[0004] The purpose of this application is to provide a bidirectional active balancing control system and method for multi-cell series-connected battery packs to solve the problems mentioned in the background art.

[0005] The bidirectional active balancing control system for multi-cell series-connected battery packs proposed in this application sets the primary-side energy storage terminal Bsv as the energy transfer node in the active balancing process, and uses a flyback transformer as the energy coupling channel between the primary and secondary sides. With the coordinated control of the primary-side control chip and the secondary-side control chip, the energy of the cell to be discharged is first transferred to the primary-side energy storage terminal Bsv for temporary storage through its corresponding secondary-side inductor and primary-side inductor, and then transferred from Bsv to the cell to be charged through the primary-side inductor and the secondary-side inductor corresponding to the cell to be charged. This "cell → Bsv → cell" energy channel enables the establishment of a bidirectional energy transfer path between any two cells in the N series-connected battery packs without having to transfer energy through the entire bus, thereby avoiding the additional losses caused by multi-stage conversion, making the energy transfer path shorter and the conversion efficiency higher. Meanwhile, the primary-side control chip and the secondary-side control chip each integrate corresponding power channel switches, directly manufacturing the discrete power devices that would otherwise require external components onto the bare die of the control chip. This allows the active balancing of the entire multi-cell battery pack to be completed by only two control chips, significantly reducing the complexity and quantity of peripheral hardware circuits. Furthermore, the extremely short connection distance between the power transistors and the control circuit effectively reduces the interference caused by parasitic inductance and resistance of PCB traces to the system.

[0006] In the implementation of a flyback transformer using a planar flyback transformer ( Figure 1 Because the windings are directly integrated between PCB layers, the transformer's thickness is significantly reduced compared to traditional wound transformers, which is particularly advantageous for applications with strict space requirements. The primary-side voltage regulator capacitor CL0 and the secondary-side voltage regulator capacitor CL1 provide stable power supply conditions for the primary and secondary control chips, respectively, filtering out power ripple and switching noise, ensuring that the internal control modules of the chip operate under reliable operating voltages.

[0007] Regarding the primary control chip ( Figure 3Internally, the primary-side input rectifier module rectifies the primary-side power supply voltage Vbsv to generate the operating voltage VDD5V and the reference voltage Vref0, providing a voltage reference for subsequent modules. The primary-side demagnetization detection module detects voltage jumps at the Vdrn0 terminal to determine whether demagnetization is complete and outputs a demagnetization signal Demg0. The primary-side overcurrent detection module monitors the current in the power channel in real time and outputs an overcurrent signal OVI0 to trigger protection when the current exceeds the safety threshold. The primary-side switching frequency control module dynamically adjusts the switching frequency according to the optocoupler feedback signal FB to adapt to different operating conditions. The signals from these modules converge to the primary-side PWM generator, which integrates the demagnetization signal Demg0, the overcurrent signal OVI0, the frequency control signal Fs0, the optocoupler feedback signal FB, and the zero-crossing detection signal Vzi0 to generate a PWM signal PWM0 with an appropriate duty cycle and frequency to drive the primary-side power channel switches in the primary-side power stage module. In particular, when the primary-side power stage module detects that the primary-side inductor current has crossed zero, it outputs a zero-crossing detection signal Vzi0. Based on this signal, the primary-side PWM generator automatically switches its operating mode from "charging Bsv from the primary-side inductor" to "discharging Bsv from the primary-side inductor", thus realizing automatic phase switching of the charging and discharging modes without the need for external timing coordination.

[0008] Regarding the secondary control chip ( Figure 4 Internally, the cell voltage monitoring module samples the voltage of each of the N battery cells and filters out cells with high voltage to be discharged and cells with low voltage to be charged, encoding the filtering results into a selection signal b_sel. The secondary input rectifier module uses each battery cell as a power source to rectify and generate the operating voltage VDD and the reference voltage Vref. The controller module implements closed-loop current control for the discharge and charging processes based on b_sel and outputs a PWM signal PWM_out and an optocoupler drive signal OPC. The secondary power stage module integrates N secondary power channel switches, which are selected based on b_sel. This architecture, which integrates voltage detection, current sampling, and N power channel selection into a single chip, eliminates the need to increase the number of control chips as the number of battery cells increases, and the system complexity does not increase linearly with the number of battery cells.

[0009] Controller module ( Figure 5 The system is further divided into two sub-modules: the secondary charging side controller module and the secondary discharging side controller module. This division is not a simple functional split, but a technical consideration based on the fundamental differences in the control objectives and feedback paths between the discharging and charging stages. The current control during the discharging stage is completed locally on the secondary side, while the current control during the charging stage needs to cross electrical isolation and be fed back to the primary side through the optocoupler communication module to form a cross-isolation closed loop. The resulting dual closed-loop structure enables precise control of the equal current on both the charging and discharging sides even under isolation conditions.

[0010] On the secondary charging side controller module ( Figure 6 In this circuit, the charging-side inductor current conversion module selects the sampled current of the secondary inductor containing the cell to be charged from the N current signals ICS1-ICSN based on the selection signal b_sel and converts it into a voltage signal Vcs_cg. The charging-side error amplifier compares and amplifies Vcs_cg with the charging-side reference voltage signal Vref_cg, outputting a charging-side error signal Verr_cg. The optocoupler driver generates an optocoupler drive signal OPC based on this signal and feeds it back to the primary-side control chip via the optocoupler communication module using an optocoupler feedback signal FB, bridging the electrical isolation. This complete signal path allows the deviation information between the secondary-side charging current and the expected value to be transmitted to the primary side in an electrically isolated manner. The primary-side control chip adjusts the switching timing of the primary-side power channel accordingly, thereby indirectly controlling the charging current amplitude. The charging-side compensator ensures the stability of the closed loop by performing frequency compensation on the error amplifier loop.

[0011] In the secondary discharge side controller module ( Figure 7 In the discharge-side inductor current conversion module, the sampling current corresponding to the cell to be discharged is selected according to b_sel and converted into a voltage signal Vcs_discg. After being compared and amplified by the discharge-side error amplifier, the discharge-side error signal Verr_discg is obtained. The secondary-side PWM generator adjusts the duty cycle of the PWM signal PWM_out according to Verr_discg to control the average discharge current of the cell to be discharged to the expected value, thus forming a closed-loop control of the discharge current locally on the secondary side. The secondary-side demagnetization detection module selects the Vdrn terminal voltage corresponding to the currently active channel according to b_sel for demagnetization detection and outputs the secondary-side demagnetization signal Demg_discg; the secondary-side overcurrent detection module monitors the selected current signal ICS_sel and outputs the protection signal OVI_discg when there is an overcurrent; the secondary-side switching frequency control module dynamically adjusts the secondary-side frequency control signal Fs_discg according to Verr_discg. These signals jointly participate in the secondary-side PWM generator's generation process of the PWM_out signal, so that the current control, demagnetization judgment and overcurrent protection in the discharge stage are organically coordinated.

[0012] Furthermore, the charging-side reference voltage signal Vref_cg output by the charging-side reference voltage generator and the discharging-side reference voltage signal Vref_discg output by the discharging-side reference voltage generator are both configurable reference voltage signals. By configuring the levels of the two signals respectively, the average charging current level of the cell to be charged and the average discharging current level of the cell to be discharged can be independently adjusted, so that the system can flexibly set the magnitude of the balancing current according to the degree of voltage difference between the cells.

[0013] In the secondary power stage module ( Figure 8In this circuit, the temperature monitoring module monitors the chip's operating temperature in real time. When the temperature exceeds the safety threshold, it outputs a temperature protection signal OTP_discg. The non-overlapping logic module outputs non-overlapping pulse signals PWM_discg and PWM_cg based on PWM_out and OTP_discg. The non-overlapping dead time setting ensures that the charging branch and the discharging branch in the same power channel will not be turned on simultaneously, thereby avoiding damage to power devices and energy loss caused by shoot-through current. When the temperature protection signal OTP_discg is valid, the non-overlapping logic module forcibly shuts down the two pulse outputs, causing all power channel switches to open to achieve automatic over-temperature shutdown protection.

[0014] Power module ( Figure 9 The system comprises N power channels, each corresponding to one of the N battery cells. The power ground of each channel is connected to the negative terminal of the corresponding battery cell, and the power terminal is connected to the corresponding tap on the secondary inductor of the flyback transformer. The selection signal b_sel determines which channel is active during the current balancing cycle. The power transistor in each power channel can function as a discharge channel under the PWM_discg signal and as a charging channel under the PWM_cg signal. This means that the same power channel can function as both a discharge energy source and a charging energy sink under different PWM control signals, achieving bidirectional multiplexing of the power channel.

[0015] Furthermore, the secondary-side control chip uses N series-connected battery cells as its own power source. Each of the N power ports is connected to the positive terminal of one of the N battery cells. The secondary-side input rectifier module rectifies the input voltage of each power port to generate a unified operating voltage VDD and a reference voltage Vref. This cell-by-cell power supply architecture allows a single primary-side control chip to cover the entire voltage range of the series-connected battery pack. This provides a foundation for the N secondary-side power channels to operate in the voltage domain of their corresponding battery cells, avoiding the hardware redundancy caused by configuring a separate chip for each battery cell's power supply domain in traditional solutions.

[0016] In summary, the active balancing control system of this application constitutes a triple protection mechanism consisting of overcurrent detection, overtemperature detection, and demagnetization detection. These protection signals are respectively output by the primary-side overcurrent detection module (OVI0), the secondary-side overcurrent detection module (OVI_discg), the temperature monitoring module (OTP_discg), the primary-side demagnetization detection module (Demg0), and the secondary-side demagnetization detection module (Demg_discg). These protection signals are respectively connected to the corresponding PWM generator or non-overlapping logic module, enabling the system to protect the power channel switch in a timely manner under various fault conditions such as overcurrent, overtemperature, and demagnetization anomalies, thereby improving the reliability of the active balancing system in actual operation.

[0017] At the methodological level, the bidirectional active balancing control method of this application sequentially executes the following complete processes: establishing the working voltage domain, detecting the voltage of individual battery cells and selecting the target cell, discharging the cell to be discharged to charge the secondary inductor, transferring energy from the secondary to the primary side to charge the primary energy storage terminal Bsv, switching modes after the primary inductor current crosses zero to discharge Bsv, transferring energy from the primary to the secondary side to charge the cell to be charged, and returning to the next balancing cycle after demagnetization detection. The commutation between each stage in this method is automatically completed based on the primary inductor current zero-crossing detection or the demagnetization detection result of the flyback transformer, without requiring additional timing coordination from an external controller. During the discharge phase, the average discharge current is controlled locally on the secondary side via a closed-loop mechanism: "sampled current → voltage signal Vcs_discg → error amplification Verr_discg → secondary-side PWM generator adjusting PWM_out duty cycle". During the charging phase, the average charging current is controlled via a closed-loop mechanism across electrical isolation, feeding back to the primary side via "sampled current → voltage signal Vcs_cg → error amplification Verr_cg → optocoupler driver OPC → optocoupler communication module → optocoupler feedback signal FB → primary-side PWM generator". The coordinated operation of these two feedback paths allows for precise and independent adjustment of the equalization current on both the charging and discharging sides under electrical isolation conditions. By configuring the charging-side reference voltage signal Vref_cg and the discharging-side reference voltage signal Vref_discg with different levels, controllable adjustment of the equalization current can be achieved at the method level, enabling the system to flexibly select the appropriate equalization speed under different voltage deviation conditions.

[0018] The specification of this application contains numerous technical features distributed across various technical solutions. Listing all possible combinations of these technical features (i.e., technical solutions) would make the specification excessively lengthy. To avoid this problem, the various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which are considered to have been described in this specification), unless such a combination of technical features is technically infeasible. For example, one example discloses feature A+B+C, and another example discloses feature A+B+D+E. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; they cannot be used simultaneously. Feature E can technically be combined with feature C. Therefore, the solution A+B+C+D should not be considered as described because it is technically infeasible, while the solution A+B+C+E should be considered as described. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of a bidirectional active balancing control system for a multi-cell series-connected battery pack according to an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of a battery pack charge-discharge equalization control system in the prior art.

[0021] Figure 3 This is a schematic diagram of the structure of the primary-side control chip according to an embodiment of this application.

[0022] Figure 4 This is a schematic diagram of the structure of a secondary control chip according to an embodiment of this application.

[0023] Figure 5 This is a schematic diagram of the controller module in the secondary control chip according to an embodiment of this application.

[0024] Figure 6 This is a schematic diagram of the charging-side controller module in the secondary-side control chip according to an embodiment of this application.

[0025] Figure 7 This is a schematic diagram of the discharge-side controller module in the secondary-side control chip according to an embodiment of this application.

[0026] Figure 8 This is a schematic diagram of the power stage module in the secondary control chip according to an embodiment of this application.

[0027] Figure 9 This is a schematic diagram of the power module in the secondary control chip according to an embodiment of this application.

[0028] Figure 10 This is a flowchart of the bidirectional active balancing control system between individual cells of a multi-cell series-connected battery pack according to an embodiment of this application. Detailed Implementation

[0029] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0030] Explanation of some concepts: Active balancing refers to a method in which excess energy in a multi-cell series battery pack is actively transferred to a lower-voltage cell through a controllable energy transfer mechanism, so that the voltages of the cells tend to be consistent.

[0031] A flyback transformer is an isolated transformer topology that stores energy in the transformer inductance during the switching-on period and releases the stored energy to the load side during the switching-off period.

[0032] A planar flyback transformer is a flyback transformer in which the windings are directly implemented using the copper layers of a printed circuit board (PCB). Its thickness dimension is significantly reduced compared to that of a traditional wound transformer.

[0033] Demagnetization refers to the process by which the magnetic field energy stored in the inductor of a flyback transformer is completely released to the load side or transferred. When demagnetization is complete, the inductor current drops to zero.

[0034] The inductor current crossing zero refers to the moment when the current flowing through the inductor winding of a flyback transformer decreases to zero in one direction and is about to reverse. This moment is usually used as the trigger criterion for mode switching in the control timing.

[0035] Non-overlapping logic refers to a logic control method that sets a dead time between the charging branch switch signal and the discharging branch switch signal in the same power channel to ensure that the two switches will not be turned on at the same time.

[0036] The primary-side energy storage terminal refers to the energy storage element set on the primary side of the flyback transformer in an active balancing system. It is used to temporarily store energy from battery cells with higher voltage during the balancing cycle and then transfer the energy to battery cells with lower voltage.

[0037] The selection signal b_sel is an encoded signal output by the cell voltage monitoring module in the secondary control chip based on the detection results of the voltage of each battery cell. It is used to indicate the number of the selected cell to be discharged and the cell to be charged in the current equalization cycle, and to select and control the N secondary power channels accordingly.

[0038] An optocoupler communication module is a communication module that uses optocouplers to achieve electrically isolated signal transmission. Its input end receives the optocoupler drive signal OPC from the secondary side, and its output end generates an optocoupler feedback signal FB, which transmits control information between different ground potential domains of the primary and secondary sides.

[0039] The following is a brief summary of some of the innovative aspects of this application: In summary, the innovative contribution of the bidirectional active balancing control system for multi-cell series-connected battery packs proposed in this application is not a simple improvement or replacement of a single element in existing flyback balancing technology. Rather, it lies in the inventor's construction of a comprehensive technical solution addressing the technical challenge of "how to achieve controlled bidirectional energy dispatch between any two cells in a series-connected battery pack with as few control chips as possible without passing through the entire busbar." This solution involves a primary-side energy storage terminal (Bsv) relay, a secondary-side selection signal (b_sel) that selects N integrated power channels on-chip point-to-point, and a collaborative mechanism between the cross-electrical isolation optocoupler feedback signal (FB) and the secondary-side local PWM closed-loop. The reason this solution can overcome the structural limitation of existing multi-winding flyback solutions, which can only transfer energy between "cells and the entire pack," lies in the inseparable intrinsic relationship between the following features: the cell voltage monitoring module inside the secondary-side control chip (…). Figure 4 The voltage of each of the N battery cells is sampled and a selection signal b_sel is output. This signal is simultaneously applied to the secondary discharge side controller module. Figure 7 ) and secondary charging side controller module ( Figure 6 ) and secondary power stage modules ( Figure 8 , Figure 9 The N power channels in the primary-side control chip allow different power channels for different battery cells to be selected during the discharge and charging phases within the same equalization cycle. This ability to "time-division multiplex the same flyback transformer to achieve energy scheduling between any two cells" relies precisely on the primary-side energy storage terminal (Bsv) providing a temporary energy storage function between the discharge and charging phases. Without Bsv, the energy released by the secondary-side discharge inductor cannot reside on the primary side and wait for the charging power channel to open. Furthermore, the primary-side control chip (… Figure 3The primary-side power stage module automatically switches from charging mode to discharging mode after detecting the zero-crossing signal Vzi0 of the primary-side inductor current. This commutation timing, together with the demagnetizing signal Demg_discg output by the secondary-side demagnetizing detection module, ensures a seamless transition from the discharging stage to the charging stage. At the same time, the sampled current on the charging side is converted and then used by the optocoupler driver to generate the optocoupler drive signal OPC. This signal is converted into the optocoupler feedback signal FB through the optocoupler communication module across electrical isolation and sent to the primary-side PWM generator. This establishes a closed-loop regulation of the average charging current under isolation conditions. This cross-isolation closed loop, together with the secondary-side discharge side local closed loop (Vcs_discg→Verr_discg→PWM_out), forms a dual closed loop that allows the equalization current on both the charging and discharging sides to be controlled independently and precisely. The combination of the above features has not been fully disclosed in the prior art, nor can it be naturally obtained by simply combining the known "flyback topology", "energy storage element" and "multi-channel selection" because there is a one-to-one locked structural constraint between the power supply domain of each cell and the transformer winding in the existing multi-winding scheme. Under this constraint, those skilled in the art lack the technical inspiration to replace the multi-winding with "single transformer multi-tap + primary side energy storage transfer + secondary side single chip b_sel selection".

[0040] Furthermore, the inventors of this application have discovered through long-term in-depth research that the reason why existing multi-cell series battery pack active balancing technology cannot simultaneously achieve satisfactory technical performance in the three dimensions of integration, balancing path and current control accuracy is that there is an inherent contradiction between the system topology and control architecture of the existing solutions.

[0041] After a thorough analysis of existing equalization schemes, exemplified by multi-winding flyback transformers, the inventors discovered that while these schemes manage the power channels of each battery cell through independent control circuits or chips, enabling energy transfer between individual cells and the battery pack, the inherent structural characteristic of "each cell's power supply domain being locked to the transformer winding" prevents the power channels from being flexibly redistributed to different cells within the same equalization cycle. In other words, this type of scheme eliminates the possibility of directly establishing an energy transfer channel between any two cells at the topology level. Energy must first converge to the entire bus or a common node before being distributed to the target cell, resulting in unnecessary multi-stage conversion losses and longer equalization paths. The inventors further noted that this discrete control architecture, with its "one chip per cell" approach, leads to a proportional increase in the number of chips and external power devices as the number of battery cells increases. This not only increases PCB trace length and worsens parasitic parameters but also makes timing coordination between multiple chips an additional engineering burden.

[0042] At the control level, through in-depth analysis of the electrical isolation characteristics between the primary and secondary sides in a flyback equalization topology, the inventors realized that since the primary energy storage side and the secondary battery pack side each have independent ground potential references, the current information during the charging phase must cross the electrical isolation boundary to be fed back to the primary control terminal. This requirement is often simplified or not fully considered in existing solutions, resulting in insufficient closed-loop regulation accuracy of the charging current and an unavoidable deviation between the actual and expected values ​​of the equalization current. After repeated demonstrations, the inventors further realized that although the control objectives for the equalization current during the discharging and charging phases are the same (i.e., maintaining the average current at the expected level), their feedback paths are physically distinct. The former can be locally closed on the secondary side, while the latter must achieve cross-domain feedback through an isolation channel. This difference requires the system to construct independent closed loops for both the charging and discharging sides at the controller architecture level, and to ensure precise timing coordination between the two closed loops in order to achieve precise bidirectional regulation of the equalization current under isolation conditions.

[0043] Based on the above in-depth research, the inventors of this application propose an overall technical solution that uses the primary-side energy storage terminal Bsv as the energy transfer node, integrates N power channels on the secondary-side single chip and performs point-to-point selection via the selection signal b_sel, and forms a dual-closed-loop collaborative control system with the optocoupler feedback signal FB and the secondary-side local PWM closed loop. This enables direct bidirectional energy dispatching between any two cells in a multi-cell series battery pack with only two control chips. The implementation process of this invention is described in detail below through specific embodiments.

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] Example 1: Bidirectional Active Balancing Control System Between Individual Cells in a Multi-Section Series Battery Pack Figure 1 This is a schematic diagram of the overall structure of the bidirectional active balancing control system between individual cells of a multi-cell series-connected battery pack provided in an embodiment of the present invention. Figure 1As shown, the active balancing control system includes a primary-side energy storage terminal Bsv, a secondary-side battery pack consisting of N series-connected battery cells B1-BN, a flyback transformer, a primary-side control chip, a secondary-side control chip, and an optocoupler communication module. N is an integer greater than or equal to 2, and each battery cell corresponds to an independent power channel. The core idea of ​​this system is to introduce the primary-side energy storage terminal Bsv~ as an energy transfer node, and to use one primary-side control chip and one secondary-side control chip to collaboratively control a flyback transformer, enabling bidirectional energy transfer channels to be established between any two battery cells in the series-connected battery pack, without needing to transfer energy through the entire busbar. Compared to the multi-winding flyback schemes used in existing technologies that require multiple chips to work together, this scheme only requires two control chips to complete all balancing functions, and both chips integrate corresponding power channel switches, significantly reducing the number of external components and parasitic interference on PCB traces. The components are described in detail below.

[0046] The positive terminal of the primary-side energy storage terminal Bsv is Vbsv, and the negative terminal is ground potential GND0. It is used to temporarily store energy from battery cells with higher voltage during active balancing and subsequently transfer this energy to battery cells with lower voltage. In other words, the primary-side energy storage terminal Bsv acts as an energy transfer node throughout the balancing cycle, allowing energy to be transferred bidirectionally between any two cells without passing through the entire battery pack bus. It should be noted that the "energy storage terminal" mentioned here is implemented in the form of an energy storage battery in this embodiment. In other equivalent embodiments, the primary-side energy storage terminal Bsv can also be replaced by any component capable of temporarily storing electrical energy within the time scale of the balancing cycle, such as a supercapacitor, a large-capacity electrolytic capacitor, or an energy storage inductor, as long as it can complete the charging and discharging process within one balancing cycle.

[0047] The secondary battery pack consists of N battery cells B1-BN connected in series, with the positive electrode voltages of each cell sequentially designated as VBAT1-VBATN. The reference ground potential of the entire battery pack is GND. For example, in a typical application scenario, N can be 4, 7, 13, or 16, and the nominal voltage of each battery cell can be within the common voltage range for lithium batteries. Due to differences in manufacturing processes, aging levels, and self-discharge rates among the battery cells, inconsistencies in voltage between cells are inevitable during use, which is the fundamental reason for the need for active balancing. In this embodiment, each battery cell can either act as a cell to release excess energy or as a cell to receive supplemental energy, the specific role being automatically determined by the secondary control chip based on the actual voltage deviation of each cell.

[0048] The flyback transformer is the core component for energy transfer in this system. Its primary-side inductor has two taps connected to voltages Vbsv and Vdrn0, respectively. The secondary-side inductor has N taps, one end of which is sequentially connected to the positive terminals BAT1-BATN of each individual battery cell, and the other end is sequentially connected to voltages Vdrn1-VdrnN. This multi-tap secondary-side inductor structure allows each battery cell to have an independent channel directly coupled to the flyback transformer. Under the selection control of the secondary-side control chip, the energy of any battery cell can be transferred to any other battery cell via the primary-side energy storage terminal Bsv, thus providing the hardware foundation for energy transfer between any two cells. Furthermore, in a preferred embodiment, the flyback transformer is a planar flyback transformer, with its windings directly integrated between PCB layers. Compared to traditional wound transformers, planar flyback transformers have significantly reduced dimensions in the thickness direction, offering a significant advantage for applications with strict space utilization requirements. Optionally, the flyback transformer can also be of other forms, such as a low-profile wound transformer, as long as it can meet the bidirectional energy transfer requirement between the primary and secondary inductors. For key design parameters of the flyback transformer, please refer to Supplementary Item Nine in the appendix of this specification.

[0049] The primary-side control chip is the core control unit on the primary side of the system. Its power supply terminal is connected to voltage Vbsv, its reference ground terminal is connected to voltage GND0, its rectified and regulated output terminal outputs voltage VDD5V, its feedback input terminal receives the optocoupler feedback signal FB, and its power terminal is connected to voltage Vdrn0. More specifically, the primary-side control chip integrates a primary-side power channel switch; that is, the power transistor is directly manufactured on the die of the control chip, rather than using the traditional approach of external discrete power devices. Based on the optocoupler feedback signal FB and internally generated demagnetizing and overcurrent signals, the primary-side control chip controls the switching of the primary-side power channel switch to charge and discharge the primary-side energy storage terminal Bsv. This design, integrating the power transistor within the control chip, results in extremely short trace lengths in the critical power loop on the primary side, effectively reducing switching spike voltages and conduction losses caused by parasitic inductance and resistance. For details regarding chip integration technology and power transistor type, please refer to Supplementary Item Ten in the appendix of this specification.

[0050] The secondary-side control chip is the core of the secondary-side control of the system. It has N power ports, sequentially connected to the positive terminal voltages VBAT1-VBATN of each individual battery cell, with the reference ground connected to ground potential GND. The rectified and regulated output terminal outputs the operating voltage VDD. N power ports are sequentially connected to voltages Vdrn1-VdrnN, and the optocoupler drive output terminal outputs the optocoupler drive signal OPC. The secondary-side control chip integrates N secondary-side power channel switches, each corresponding to a single battery cell. Based on the voltage of each battery cell, the secondary-side control chip filters out cells with higher voltages to be discharged and cells with lower voltages to be charged, and selects their corresponding secondary-side power channel switches using the selection signal b_sel. This architecture of "integrating N power channels on a single chip and using selection signals for point-to-point selection" is one of the key structural features that distinguishes this invention from existing solutions. In the prior art, the power channel of each battery cell is usually controlled by an independent chip or an independent drive circuit. As the number of battery cells increases, the system complexity and hardware cost rise sharply. However, the secondary control chip of the present invention integrates voltage detection, current sampling and N-channel power selection into a single chip, which significantly simplifies the system design.

[0051] It should be noted that the secondary-side control chip uses N battery cells connected in series as its own power source. The N power ports are connected one-to-one with the positive terminals of the N battery cells. The secondary-side input rectifier module rectifies the input voltage of each power port to generate the operating voltage VDD and reference voltage Vref for the secondary-side control chip itself. This cell-by-cell power supply architecture allows a single primary-side control chip to cover the voltage span of the entire series-connected battery pack, providing a basis for the N secondary-side power channels to operate in the voltage domain of their corresponding battery cells. This avoids the hardware redundancy caused by configuring a separate chip for each battery cell's power supply domain in traditional solutions.

[0052] The input of the optocoupler communication module is connected to the optocoupler drive signal OPC, and the output is an optocoupler feedback signal FB, which feeds back the charging current information of the secondary side to the primary side control chip in an electrically isolated manner. Since the primary side energy storage terminal Bsv and the secondary side battery pack each have independent ground potentials (GND0 and GND respectively), and a potential difference exists between them, the electrical isolation function provided by the optocoupler communication module is crucial for the safe and stable operation of the system. For details on the specific modulation method of the charging current information transmitted by the optocoupler feedback signal FB, please refer to Supplementary Item 3 in the appendix of this specification. Optionally, in other embodiments of the present invention, the optocoupler communication module can be equivalently replaced by components with electrical isolation functions such as magnetically coupled digital isolators, capacitor isolators, or transformer isolators.

[0053] In addition, the active equalization control system also includes a primary-side voltage stabilizing filter capacitor CL0 and a secondary-side voltage stabilizing filter capacitor CL1, which are respectively connected between the power supply terminal and the reference ground terminal of the primary-side control chip and the secondary-side control chip, to stabilize the chip's operating voltage, filter out power supply ripple and switching noise, and ensure that each module inside the chip operates under stable power supply conditions.

[0054] In the above system, the secondary-side control chip and the primary-side control chip work together to control the flyback transformer. The coordination is as follows: the cell to be discharged first transfers energy to the primary-side energy storage terminal Bsv via its corresponding secondary-side inductor and primary-side inductor for temporary storage. Then, Bsv transfers energy to the cell to be charged via the primary-side inductor and the secondary-side inductor corresponding to the cell to be charged, thus charging it. This achieves bidirectional energy transfer between any two cells in N battery cells without passing through the entire bus. Here, "bidirectional" means that the same power channel can act as both a discharge energy source and a charging energy sink under different PWM control signals, rather than simply referring to unidirectional energy flow in a fixed direction. This "cell → Bsv → cell" energy channel is the core difference between this invention and the existing "cell ↔ entire pack" flyback scheme.

[0055] Internal structure of primary-side control chip Figure 3 is a schematic diagram of the primary-side control chip. For example... Figure 3 As shown, the primary-side control chip includes a primary-side input rectifier module, a primary-side demagnetization detection module, a primary-side overcurrent detection module, a primary-side switching frequency control module, a primary-side PWM generator, and a primary-side power stage module.

[0056] The input terminal of the primary-side input rectifier module is connected to the primary-side power supply voltage Vbsv, and the output terminal outputs voltage VDD5v and reference voltage Vref0. VDD5v provides the operating voltage for the various modules inside the primary-side control chip, while Vref0 provides the reference voltage for the subsequent PWM generator and other control modules.

[0057] The primary-side demagnetization detection module is connected to the input voltage Vdrn0 and outputs the demagnetization signal Demg0. When the energy stored in the primary-side inductance of the flyback transformer is fully released, the voltage at the Vdrn0 terminal will experience a characteristic jump. The primary-side demagnetization detection module detects this voltage jump to determine whether demagnetization is complete and outputs the demagnetization signal Demg0 accordingly. For details on the specific electrical implementation principle of demagnetization detection and the debouncing strategy to prevent false triggering, please refer to Supplementary Item VII in the appendix of this manual.

[0058] The input of the primary-side overcurrent detection module is connected to the current signal ICS0 sampled by the primary-side power channel switch, and the output is the overcurrent signal OVI0. When the current in the primary-side power channel exceeds a preset safety threshold, the overcurrent signal OVI0 is triggered to protect the power channel switch and flyback transformer from damage due to excessive current.

[0059] The primary-side switching frequency control module's optocoupler feedback input is connected to the optocoupler feedback signal FB, and its output is the frequency control signal Fs0. Based on the secondary-side charging current information carried by the optocoupler feedback signal FB, this module dynamically adjusts the switching frequency of the primary-side power channel to adapt to the energy transfer requirements under different equalization conditions.

[0060] The primary-side PWM generator is the control center of the primary-side control chip. Its demagnetizing signal input is connected to the demagnetizing signal Demg0, the reference voltage input is connected to Vref0, the optocoupler feedback input is connected to the optocoupler feedback signal FB, the overcurrent signal input is connected to the overcurrent signal OVI0, the frequency input is connected to the frequency control signal Fs0, the zero-crossing signal receiver receives the inductor current zero-crossing signal Vzi0, and the output terminal outputs the PWM signal PWM0. The primary-side PWM generator integrates these multiple input signals to generate a PWM signal PWM0 with an appropriate duty cycle and frequency to drive the primary-side power channel switch. Specifically, when the zero-crossing signal Vzi0 indicates that the primary-side inductor current has crossed zero, the primary-side PWM generator automatically switches its operating mode from "charging the primary-side inductor to Bsv" to "discharging the primary-side inductor from Bsv," that is, the direction of the primary-side inductor current reverses and begins to increase, realizing automatic commutation of the charging and discharging mode. Subsequently, the primary-side PWM generator, in conjunction with the demagnetizing signal Demg0 and the optocoupler feedback signal FB, controls the primary-side power channel switch to turn off. When the optocoupler feedback signal FB indicates that the current has reached the required level, the primary-side power channel switch is turned off.

[0061] The primary-side power stage module internally includes the aforementioned primary-side power channel switch. Its pulse input terminal is connected to the PWM signal PWM0, and its power terminals are connected to the primary-side ground potential GND0 and Vdrn0 respectively. The current detection output terminal outputs the current signal ICS0, and the zero-crossing detection output terminal outputs the inductor current zero-crossing signal Vzi0. The primary-side power stage module drives its internal power channel switch according to the PWM0 signal, controlling the on / off state and direction of the current in the primary-side inductor. It also monitors the current information ICS0 flowing through the power channel in real time through its internal current sampling structure, and simultaneously monitors whether the inductor current has crossed zero through the zero-crossing detection circuit and outputs the zero-crossing detection signal Vzi0. For details on the specific electrical implementation of the zero-crossing detection, please refer to Supplementary Item Six in the appendix of this manual.

[0062] Internal structure of the secondary control chip Figure 4 This is a schematic diagram of the secondary control chip. (See diagram below.) Figure 4 As shown, the secondary control chip includes a cell voltage monitoring module, a secondary input rectifier module, a controller module, and a secondary power stage module.

[0063] The cell voltage monitoring module's input is connected to the positive and negative voltages of each individual cell in the battery pack, and its output is a selection signal b_sel. This module samples and compares the voltages of N individual cells one by one, filtering out cells with excessively high voltages to be discharged and those with excessively low voltages to be charged, and encodes the filtering results as the selection signal b_sel. The selection signal b_sel is the algorithmic hub for achieving "arbitrary cell-to-cell" equalization; subsequent controller and power stage modules determine which power path should be activated based on b_sel. For details regarding the specific sampling method, sorting, threshold determination process, and b_sel encoding rules of the cell voltage monitoring module, please refer to Supplementary Item 1 in the appendix of this manual; for the specific criteria for determining "excessively high voltage" and "excessively low voltage," please refer to Supplementary Item 2 in the appendix of this manual.

[0064] The input terminal of the secondary-side input rectifier module is connected to the positive and negative terminal voltages of each individual battery cell in the battery pack, and its output terminals output the operating voltage VDD and the reference voltage Vref, respectively. As mentioned earlier, this module receives power from N individual battery cells and rectifies it to generate a unified operating voltage domain and reference standard required by all modules within the secondary-side control chip.

[0065] The controller module's selection input is connected to the selection signal b_sel, the reference voltage input is connected to the reference voltage Vref, and the current input is connected to the current signals ICS1-ICSN. The outputs are the PWM signal PWM_out and the optocoupler drive signal OPC, respectively. The controller module is the decision-making core of the secondary control chip; it performs closed-loop current control on the discharging and charging processes based on the cell to be discharged and charged as indicated by b_sel.

[0066] The secondary power stage module contains N secondary power channel switches that correspond one-to-one with each battery cell. The selection input terminal is connected to the selection signal b_sel, the pulse input terminal is connected to the PWM signal PWM_out, the power ports are connected to the battery terminals BAT1-BATN, GND and Vdrn1-VdrnN respectively, and the current detection output terminal outputs the current signal ICS1-ICSN.

[0067] Internal structure of the controller module Figure 5 This is a structural diagram of the controller module. (For example...) Figure 5As shown, the controller module further includes a secondary-side charging-side controller module and a secondary-side discharging-side controller module. The controller module is divided into two independent sub-modules, charging and discharging, because in the equalization process of this invention, the control objectives and feedback paths for the discharging and charging phases are different: current control during the discharging phase is completed locally on the secondary side, while current control during the charging phase needs to cross electrical isolation and be fed back to the primary side via an optocoupler communication module to form a cross-isolation closed loop. This "dual closed-loop" structure enables precise control of the charging and discharging current amplitude even under electrical isolation conditions.

[0068] The secondary charging-side controller module has its reference voltage input connected to the reference voltage Vref, its current input connected to current signals ICS1-ICSN, its selection input connected to the selection signal b_sel, and its output output being the optocoupler drive signal OPC. The secondary discharging-side controller module has its reference voltage input connected to the reference voltage Vref, its current input connected to current signals ICS1-ICSN, its selection input connected to the selection signal b_sel, its demagnetization detection input connected to voltages Vdrn1-VdrnN, and its output output being the PWM signal PWM_out. These two sub-modules are responsible for the current loop control on the charging and discharging sides respectively, working together to achieve bidirectional energy scheduling during the equalization cycle.

[0069] Secondary charging side controller module Figure 6 This is a structural diagram of the secondary charging side controller module. (See diagram below.) Figure 6 As shown, the secondary charging side controller module includes a charging side reference voltage generator, a charging side inductor current conversion module, a charging side error amplifier, a charging side compensator, and an optocoupler driver.

[0070] The reference voltage input of the charging-side reference voltage generator is connected to the reference voltage Vref, and its output terminal outputs the charging-side reference voltage signal Vref_cg. This reference voltage signal Vref_cg serves as the reference for the charging-side error amplifier and directly determines the target value of the average charging current. Furthermore, Vref_cg is a configurable reference voltage signal; by configuring its level, the average charging current level of the individual cell to be charged can be directly adjusted.

[0071] The charging-side inductor current conversion module has a selection input connected to the selection signal b_sel, a current input connected to the current signals ICS1-ICSN, and an output voltage signal Vcs_cg. Based on the selection signal b_sel, this module selects the sampled current of the secondary inductor containing the cell to be charged from the N current signals ICS1-ICSN and converts it into a voltage signal Vcs_cg that is proportional to the current.

[0072] The charging-side error amplifier connects its reference voltage input to the charging-side reference voltage signal Vref_cg, its feedback input to the voltage signal Vcs_cg, and its output to the charging-side error signal Verr_cg. The compensation input is connected to the voltage signal Vcmp_cg. The charging-side error amplifier compares the voltage signal Vcs_cg with the charging-side reference voltage signal Vref_cg, amplifies the difference, and outputs the charging-side error signal Verr_cg. The input of the charging-side compensator is connected to the voltage signal Vcmp_cg, and it is used to perform frequency compensation on the charging-side error amplifier loop to ensure the stability of the charging-side control loop. For details on the specific circuit structure of the compensator, please refer to Supplementary Item 8 in the Appendix of this manual.

[0073] The input of the optocoupler driver is connected to the charging-side error signal Verr_cg, and the output is the optocoupler drive signal OPC. The optocoupler driver generates the optocoupler drive signal OPC based on the charging-side error signal Verr_cg. This signal is converted into an optocoupler feedback signal FB by the optocoupler communication module and fed back to the primary-side control chip after overcoming electrical isolation. This constitutes an isolated closed-loop control of the average charging current of the individual cells: when the charging current deviates from the desired value, the change in the error signal Verr_cg is transmitted to the primary side via the optocoupler channel. The primary-side control chip adjusts the switching timing of the primary-side power channel accordingly, thereby indirectly regulating the charging current to bring it closer to the desired level.

[0074] Secondary discharge side controller module Figure 7 This is a schematic diagram of the secondary discharge side controller module. (See diagram below.) Figure 7 As shown, the secondary discharge side controller module includes a discharge side reference voltage generator, a discharge side inductor current conversion module, a discharge side error amplifier, a discharge side compensator, a secondary side demagnetization detection module, a secondary side overcurrent detection module, a secondary side switching frequency control module, and a secondary side PWM generator.

[0075] The discharge-side reference voltage generator's input terminal is connected to the reference voltage Vref, and its output terminal outputs the discharge-side reference voltage signal Vref_discg. Similar to the charging side, Vref_discg is also a configurable reference voltage signal. By configuring its level, the average discharge current level of the cell to be discharged can be directly adjusted. This dual-level mechanism, where the charging and discharging sides are independently adjustable, allows the system to flexibly set the balancing current based on the degree of voltage difference between battery cells. For example, when the voltage deviation is large, a higher balancing current level can be selected to accelerate the balancing speed; when the voltage deviation tends to converge, the balancing current can be reduced to improve control accuracy. For the specific quantitative relationship between each level and the balancing current, please refer to Supplementary Item 5 in the appendix of this manual.

[0076] The discharge-side inductor current conversion module has its selection input connected to the selection signal b_sel, its current input connected to current signals ICS1-ICSN, and its output output a voltage signal Vcs_discg. The current output also outputs the current signal ICS_sel selected by the selection signal b_sel. This module selects the sampling current corresponding to the cell to be discharged from N current signals based on b_sel and performs current-to-voltage conversion. The discharge-side error amplifier has its reference voltage input connected to the discharge-side reference voltage signal Vref_discg, its feedback input connected to the voltage signal Vcs_discg, its output output a discharge-side error signal Verr_discg, and its compensation terminal connected to the voltage signal Vcmp_discg. The discharge-side compensator's input is connected to the voltage signal Vcmp_discg and is used for frequency compensation in the discharge-side control loop.

[0077] The secondary demagnetization detection module has its input terminals connected to voltages Vdrn1-VdrnN, its selection input terminal connected to the selection signal b_sel, and its output terminal outputting the secondary demagnetization signal Demg_discg. This module selects the Vdrn terminal voltage corresponding to the currently active power channel based on b_sel for demagnetization detection. The secondary overcurrent detection module has its input terminal connected to the current signal ICS_sel and its output terminal outputting the secondary overcurrent signal OVI_discg, used to trigger protection when the secondary discharge current exceeds a safety threshold. The secondary switching frequency control module has its input terminal connected to the discharge-side error signal Verr_discg and its output terminal outputting the secondary frequency control signal Fs_discg.

[0078] The error signal input of the secondary-side PWM generator is connected to the discharge-side error signal Verr_discg, the demagnetization signal input is connected to the secondary-side demagnetization signal Demg_discg, the reference voltage input is connected to the discharge-side reference voltage signal Vref_discg, the overcurrent signal input is connected to the secondary-side overcurrent signal OVI_discg, and the frequency input is connected to the secondary-side frequency control signal Fs_discg. The output terminal outputs the PWM signal PWM_out. The secondary-side PWM generator adjusts the duty cycle of the PWM signal PWM_out according to the discharge-side error signal Verr_discg to control the average discharge current of the cell to be discharged to the expected value. Thus, a secondary-side local closed loop is formed on the discharge side: "Sampling current ICS1-ICSN → Voltage signal Vcs_discg → Error amplification Verr_discg → Secondary-side PWM generator adjusting the duty cycle of PWM_out," achieving precise control of the average discharge current.

[0079] Secondary power stage module Figure 8 This is a schematic diagram of the secondary power stage module. (See diagram below.) Figure 8As shown, the secondary power stage module includes a temperature monitoring module, a non-overlapping logic module, and a power module.

[0080] The temperature monitoring module's reference voltage input is connected to a reference voltage Vref, and its output terminal outputs a temperature protection signal OTP_discg. This module monitors the operating temperature of the secondary power stage module in real time. When the detected temperature exceeds a preset safety threshold, it outputs the temperature protection signal OTP_discg to trigger a protection action. For details regarding the temperature monitoring module's trigger threshold, protection action, and recovery strategy, please refer to Supplementary Item 4 in the appendix of this manual.

[0081] The non-overlapping logic module connects the pulse input to the PWM signal PWM_out and the temperature protection input to the temperature protection signal OTP_discg. Its outputs are non-overlapping pulse signals PWM_discg and PWM_cg, respectively. The core function of this module is to ensure that the charging and discharging branches within the same power channel do not conduct simultaneously. This is achieved by setting a non-overlapping dead time between PWM_discg and PWM_cg to prevent damage to power devices and energy loss due to shoot-through current. When the temperature protection signal OTP_discg is active, the non-overlapping logic module forcibly shuts down both pulse outputs, disconnecting all power channel switches and thus achieving automatic shutdown protection in case of overheating.

[0082] Figure 9 This is a schematic diagram of the power module. (For example...) Figure 9 As shown, the power module includes N power channels, namely power channel 1 to power channel N, and each of the N power channels integrates N secondary power channel switches. The pulse input terminals of the N power channels are connected to pulse signals PWM_discg and PWM_cg, respectively; the selection input terminals are all connected to the selection signal b_sel; the reference voltage input terminals are all connected to the reference voltage Vref; and the current detection output terminals output current signals ICS1-ICSN, respectively. Regarding the power port connections, the power ports of power channel 1 are connected to GND and Vdrn1; the power ports of power channels j (where j=2, 3, …, N) are connected to BAT(j-1) and Vdrnj, respectively. This connection method allows the power ground terminal of each power channel to be connected to the negative terminal of its corresponding battery cell, while the power terminal is connected to the corresponding tap of the secondary inductor of the flyback transformer, thus enabling each power channel to operate independently within the voltage domain of its corresponding battery cell. The selection signal b_sel determines which channel is in the conducting state during the current balancing cycle. The power transistors in each power channel can act as a discharge channel under the action of the PWM_discg signal and as a charging channel under the action of the PWM_cg signal. That is, the same power channel can act as both a discharge power source and a charging sink under the action of different PWM control signals, realizing bidirectional multiplexing of the power channel.

[0083] As can be seen from the above structure, the active balancing control system in this embodiment employs a triple protection mechanism consisting of overcurrent detection (primary-side OVI0, secondary-side OVI_discg), overtemperature detection (OTP_discg), and demagnetization detection (primary-side Demg0, secondary-side Demg_discg). These three types of protection signals are respectively connected to the corresponding PWM generators or non-overlapping logic modules, enabling the system to promptly protect the power channel switches under various fault conditions such as overcurrent, overtemperature, and demagnetization anomalies, thereby improving the reliability of the active balancing system.

[0084] Example 2: Bidirectional Active Equalization Control Method Figure 10 This is a flowchart illustrating the workflow of the bidirectional active balancing control system between individual cells in a multi-cell series battery pack provided in an embodiment of the present invention. The following is in conjunction with... Figure 10 The bidirectional active balancing control method applied to the active balancing control system described in Embodiment 1 will be explained. This method includes the following steps.

[0085] Step 100: Establish the operating voltage domain.

[0086] The primary-side control chip rectifies the input voltage Vbsv, generating the primary-side operating voltage domain VDD5v and the primary-side reference voltage Vref0 through the primary-side input rectifier module. Simultaneously, the secondary-side control chip rectifies the voltages of each individual battery cell (VBAT1-VBATN), generating the secondary-side operating voltage domain VDD and the secondary-side reference voltage Vref through the secondary-side input rectifier module. VDD5v and Vref0 provide the voltages for the control logic and benchmark comparison in subsequent steps of the primary-side control chip; VDD and Vref provide the voltages for voltage monitoring, current sampling, and PWM generation in subsequent steps of the secondary-side control chip. After this step is completed, the system enters the operational state.

[0087] Step 200: Battery cell voltage detection and target cell selection.

[0088] Under the operating voltage established in step 100, the secondary control chip uses the cell voltage monitoring module to detect the voltage of each battery cell, selects the battery cells with higher voltage as cells to be discharged and the battery cells with lower voltage as cells to be charged, and outputs a selection signal b_sel.

[0089] Step 300: Discharge of the single cell to be discharged - charging of the secondary inductor.

[0090] The secondary-side control chip, based on the selection signal b_sel, opens the secondary-side power channel switch corresponding to the cell to be discharged, allowing the cell to begin charging the secondary-side inductor of the flyback transformer. During this process, the secondary-side discharge controller module begins operation: the current in the secondary-side inductor continuously rises, and the current information is sampled and converted into a voltage signal Vcs_discg by the discharge-side inductor current conversion module. This voltage signal Vcs_discg and the discharge-side reference voltage signal Vref_discg are compared and amplified by the discharge-side error amplifier to obtain the discharge-side error signal Verr_discg. The secondary-side PWM generator then adjusts the duty cycle of the PWM signal PWM_out accordingly, forming a secondary-side closed-loop control of the average discharge current of the cell to be discharged. Optionally, the average discharge current level of the cell to be discharged can be adjusted by configuring the range of the discharge-side reference voltage signal Vref_discg output by the discharge-side reference voltage generator.

[0091] Step 400: Energy is transferred from the secondary side to the primary side – the primary side energy storage terminal Bsv is charged.

[0092] Once the average discharge current value controlled in step 300 reaches the expected value, the secondary-side control chip closes the secondary-side power channel switch corresponding to the cell to be discharged, stops the charging of the secondary-side inductor, and resets the secondary-side discharge control signal. Simultaneously, the primary-side control chip opens the primary-side power channel switch, allowing the energy stored in the secondary-side inductor of the flyback transformer in step 300 to be transferred to the primary-side energy storage terminal Bsv via the primary-side inductor. During this stage, the current flow in the primary-side inductor is from the Vdrn0 terminal, through the primary-side inductor to the Vbsv terminal, and into Bsv. The current value gradually decreases, and the primary-side energy storage terminal Bsv is charged.

[0093] Step 500: Primary inductor current crosses zero and mode switching — primary energy storage terminal Bsv discharges.

[0094] During step 400, when the primary-side power stage module in the primary-side control chip detects that the current of the primary-side inductor has crossed zero, the zero-crossing detection signal Vzi0 is sent to the primary-side PWM generator. Based on this, the primary-side PWM generator automatically switches its operating mode from "charging Bsv from the primary-side inductor" to "discharging Bsv from the primary-side inductor." In the switched discharge mode, the primary-side power channel switch remains open, the primary-side inductor current reverses direction and its value gradually increases (that is, the primary-side inductor current first decreases to zero and then automatically reverses direction after the zero-crossing detection signal Vzi0 flips; after reversal, the current value gradually increases under the energy release effect of the primary-side energy storage terminal Bsv). The primary-side energy storage terminal Bsv begins to release energy to the primary-side inductor, and the primary-side inductor begins to store energy. At this time, the primary-side overcurrent detection module, the primary-side switching frequency control module, and the primary-side PWM generator work together. The primary-side control chip controls the primary-side power channel switch according to the current value of the primary-side inductor and the optocoupler feedback signal FB. The optocoupler feedback signal FB originates from the charging current control information transmitted by the secondary-side charging controller module via the optocoupler communication module, and is used to limit the peak value of the primary-side inductor current. The primary-side PWM generator is controlled by this optocoupler feedback signal FB. When the current value of the primary-side inductor reaches the level limited by the optocoupler feedback signal FB, the primary-side control chip turns off the primary-side power channel switch, stops charging the primary-side inductor, and resets the primary-side control signal.

[0095] Furthermore, the demagnetization signal Demg0 output by the primary-side demagnetization detection module, together with the optocoupler feedback signal FB, participates in the primary-side PWM generator's control of the primary-side power channel switch, making the commutation timing more accurate and reliable.

[0096] Step 600: Energy is transferred from the primary side to the secondary side – the cell to be charged is charged.

[0097] After the primary-side power channel switch is closed in step 500, the secondary-side control chip, based on the selection signal b_sel output in step 200, opens the secondary-side power channel switch corresponding to the cell to be charged. At this time, the energy stored in the primary-side inductor in step 500 is transferred to the secondary-side inductor corresponding to the cell to be charged via a flyback transformer, and the cell is charged. During this process, the secondary-side charging controller module starts working, detecting the charging inductor current to maintain the average charging current value at the expected level. Specifically, the sampled current of the secondary-side inductor is converted into a voltage signal Vcs_cg by the charging-side inductor current conversion module. This voltage signal Vcs_cg and the charging-side reference voltage signal Vref_cg are compared and amplified by the charging-side error amplifier to obtain the charging-side error signal Verr_cg, which is then used by the optocoupler driver to generate an optocoupler drive signal OPC. This OPC signal is converted into an optocoupler feedback signal FB by the optocoupler communication module and fed back to the primary-side control chip, forming a cross-electrically isolated closed-loop control of the average charging current of the cell to be charged. The optocoupler feedback signal FB serves as the basis for the primary-side control chip to turn off the primary-side power channel switch in step 500, thus establishing a complete closed loop of "charging current sampling - error amplification - optocoupler feedback - primary-side switch control". Optionally, the average charging current level of the cell to be charged can be adjusted by configuring the charging-side reference voltage signal Vref_cg output by the charging-side reference voltage generator.

[0098] Step 700: Demagnetization detection and equalization cycle.

[0099] After the charging current of the secondary inductor reaches zero as described in step 600, the secondary power stage module shuts off the secondary power channel switch corresponding to the cell to be charged and resets the control signal on the secondary charging side. Subsequently, the secondary demagnetization detection module in the secondary control chip detects the demagnetization state of the flyback transformer, and the primary demagnetization detection module also detects the demagnetization state of the primary inductor. When the flyback transformer is detected to have completed demagnetization, the control signals on the primary and secondary sides are released, and the system returns to step 200 to repeat the process, starting the next equalization cycle. This cycle continues until the voltage difference between the individual battery cells converges to a uniform level, at which point the active equalization ends.

[0100] Therefore, the commutation at each stage between steps 200 and 700 is automatically completed based on the zero-crossing detection of the current inductor on the primary side or the demagnetization detection of the flyback transformer, without the need for additional timing coordination by an external controller. Simultaneously, the non-overlapping logic module within the secondary power stage outputs non-overlapping PWM_discg and PWM_cg based on PWM_out and the temperature protection signal OTP_discg, consistently preventing overlapping conduction of the charging and discharging branches within the same power channel throughout the entire equalization cycle, further ensuring system safety.

[0101] The above embodiments have the following technical effects The active balancing control system of this invention requires only two control chips to complete the active balancing between individual cells in the entire multi-cell series battery pack. The primary-side power transistors and N secondary-side power transistors are integrated within the bare dies of the primary-side and secondary-side control chips, respectively. Compared to existing solutions that require multiple chips working together and a large number of external discrete power devices, the complexity of the system's peripheral hardware circuitry and the number of components are significantly reduced. Simultaneously, the on-chip integration of the power transistors shortens the connection distance between the power transistors and the control circuitry, effectively reducing the interference of parasitic inductance and resistance of PCB traces on the system.

[0102] This invention introduces the primary-side energy storage terminal Bsv as an energy transfer node, and in conjunction with the primary-side inductance and multi-tap secondary-side inductance of the flyback transformer, achieves bidirectional energy transfer between any two cells in an N-cell battery pack. This "cell → Bsv → cell" energy path differs from the limitation of existing flyback schemes, which can only transfer energy between "cell → pack". Because energy is directly transferred between two cells with voltage differences, without passing through the pack bus or auxiliary batteries, the additional losses caused by multi-stage conversion are avoided, resulting in a shorter energy path and higher conversion efficiency.

[0103] The secondary control chip uses "cell voltage monitoring + selection signal b_sel" to achieve point-to-point selection of N power channels, so that the balancing current can be accurately focused on the cell pairs that need the most adjustment. It can directly perform point-to-point energy scheduling on the two cells with the largest voltage difference in the battery pack, resulting in faster balancing speed and more accurate response.

[0104] On the discharge side, a closed-loop control of the average discharge current is formed locally on the secondary side. On the charging side, feedback is sent to the primary side via an optocoupler communication module across electrical isolation to form a closed-loop control of the average charging current, achieving precise control of the balancing current under isolation conditions. Simultaneously, the reference voltage generators on both the charging and discharging sides support level configurations, allowing the balancing current to be independently adjusted among multiple levels as needed.

[0105] The fully automatic commutation timing based on primary-side inductor current zero-crossing detection and demagnetization detection enables automatic switching of power channels between stages in the equalization cycle, eliminating the need for external timing coordination. The non-overlapping logic module further avoids the risk of overlapping conduction between charging and discharging branches within the same power channel.

[0106] The secondary-side control chip uses a segment-by-segment power supply architecture where each of the N battery cells in series powers itself. This allows a single secondary-side control chip to cover the voltage span of the entire series-connected battery pack, providing a basis for the N secondary-side power channels to operate in the voltage domain of their respective battery cells. This avoids the hardware redundancy of configuring an independent chip for each battery cell's power supply domain, as is common in traditional solutions.

[0107] The combined use of overcurrent detection, temperature monitoring, and demagnetization detection mechanisms enables the system to reliably protect itself from various fault conditions such as overcurrent, overtemperature, and demagnetization anomalies.

[0108] The embodiments of this application are further explained below by way of example.

[0109] The cell voltage monitoring module internally features a multiplexed successive approximation ADC, which sequentially samples and digitizes the terminal voltage of each battery cell from B1 to BN. After each round of sampling, internal digital comparison logic sorts the N sampled values, selecting the cell with the highest voltage as the cell to be discharged and the cell with the lowest voltage as the cell to be charged. The encoding width of the selection signal b_sel is [missing information]. Position, of which high The low-order digit is the serial number of the cell to be discharged. The code encodes the serial number of the cell to be charged. For example, when N=8, b_sel is a 6-bit binary signal, with the high 3 bits indicating the cell number to be discharged and the low 3 bits indicating the cell number to be charged.

[0110] After sampling the voltage of each cell from B1 to BN, the cell voltage monitoring module calculates the average voltage of the N cells: in Let N be the arithmetic mean of the voltages of the individual N cells. For the first The terminal voltage of the unit. The voltage should be higher than... The individual cells were identified as having excessively high voltage, and those with voltages lower than [a certain value] were removed. The individual cells were identified as those with low voltage, among which... This is a preset voltage deviation threshold. Within the same equalization cycle, the cell with the highest voltage is preferentially selected as the cell to be discharged, and the cell with the lowest voltage is selected as the cell to be charged. When When the voltages of all individual cells have converged and become consistent, the active balancing process ends.

[0111] The optocoupler driver converts the error signal Verr_cg output from the charging-side error amplifier into a corresponding drive current signal OPC. This current signal drives the LED terminal of the optocoupler communication module, and the phototransistor terminal of the optocoupler communication module outputs the corresponding optocoupler feedback signal FB on the primary side. The FB signal reflects the deviation between the secondary-side charging current and the expected value in the form of an analog voltage level. The primary-side PWM generator can obtain the deviation information by detecting the level of the FB signal and adjust the turn-off time of the primary-side power channel switch accordingly. The higher the FB level, the more insufficient the secondary-side charging current is, and the primary-side inductor current is allowed to increase to a higher peak value.

[0112] The temperature monitoring module integrates a temperature sensor and comparator thermally coupled to the chip substrate. It converts the detected temperature into a voltage and compares it to a threshold voltage generated by dividing the reference voltage Vref. When the chip junction temperature exceeds the preset over-temperature protection threshold, the OTP_discg signal flips to an active level. The non-overlapping logic module then simultaneously pulls both the PWM_discg and PWM_cg signals low, shutting down all power channels. When the chip junction temperature falls below the hysteresis threshold, OTP_discg automatically recovers, and the system re-enters normal equilibrium. This protection is automatic and requires no manual reset.

[0113] Taking the discharge side as an example, the average current on the discharge side is equalized. With discharge side reference voltage and sampling resistor The relationship between them can be expressed by the following formula: in, To balance the average current on the discharge side, This is the reference voltage signal output by the discharge-side reference voltage generator. This is the current sampling resistor inside the power channel. The discharge-side reference voltage generator has at least K ≥ 2 configurable levels, each corresponding to a different... value, thus making Switch between multiple preset levels. For example, at the low setting. Taking a smaller value results in a lower average discharge current, suitable for fine balancing scenarios with small voltage differences; at high voltage levels... Taking a larger value results in a higher average discharge current, suitable for scenarios requiring rapid balancing. The situation is similar on the charging side, where the balancing average current is... With charging side reference voltage The corresponding relationship between the sampling resistor and the sampling resistor is similar.

[0114] The primary-side power stage module incorporates a zero-crossing comparator in its current sampling path. One input of this comparator is connected to the current sampling signal ICS0, and the other input is connected to a near-zero reference voltage. When the ICS0 signal drops from a positive value and crosses the reference voltage, the zero-crossing signal Vzi0, output by the zero-crossing comparator, flips, indicating that the primary-side inductor current has crossed zero. Upon receiving the flip of Vzi0, the primary-side PWM generator automatically switches its operating mode from charging mode to discharging mode. To avoid false triggering caused by switching noise, the zero-crossing detection circuit has a blanking time window, which shields the detection output for a brief period after the power transistor switches. It should be noted that in a DCM (Discontinuous Conduction Mode) flyback topology, the inductor current zero-crossing and demagnetization completion are physically correlated. Therefore, if the inventors confirm that zero-crossing detection is achieved through a voltage jump at the Vdrn0 terminal (i.e., completed by the primary-side demagnetization detection module) in actual implementation, the Vzi0 signal can be equivalently replaced by the Demg0 signal generated by the primary-side demagnetization detection module.

[0115] The primary-side demagnetization detection module determines demagnetization completion by monitoring changes in the voltage at the Vdrn0 terminal. When the energy stored in the primary-side inductance of the flyback transformer is fully released, the voltage at the Vdrn0 terminal jumps from a low potential clamped by the power transistor to a high potential near Vbsv. The comparator inside the demagnetization detection module detects this voltage jump and outputs the demagnetization signal Demg0. The secondary-side demagnetization detection module operates similarly, selecting the Vdrn terminal corresponding to the currently active channel for detection based on b_sel. To avoid false triggering caused by switching noise, both the primary and secondary-side demagnetization detection circuits have a blanking time window. The detection output is shielded for a brief period after the power transistor switches, and the detection function is restored after the switching transient ends.

[0116] The compensation network establishes a frequency-dependent feedback path between the compensation terminal and the output terminal of the error amplifier. By properly configuring the parameter values ​​of the resistors and capacitors in the compensation network, sufficient phase margin is provided at the cross-frequency of the equalization current control loop, thereby ensuring the stability of the closed-loop system.

[0117] The primary winding and N-way secondary windings of the planar flyback transformer are both implemented using PCB printed coils. Each secondary tap is connected to the power path of the corresponding battery cell via vias. A low-profile planar ferrite core can be used. Primary-to-secondary turns ratio... The transformer inductance is set based on the ratio of the primary-side energy storage terminal voltage (Bsv) to the battery cell voltage (Vcell) to ensure sufficient energy transfer efficiency while operating within a reasonable magnetic flux density range. and secondary inductance The system is determined based on its switching frequency, equalization current, and the voltage range of individual battery cells.

[0118] Both the primary-side and secondary-side control chips integrate control circuitry and power MOSFETs on the same die using BCD technology. The primary-side power channel switch uses LDMOS devices, with a drain-source withstand voltage not lower than a preset safety margin multiple of the primary-side energy storage terminal Bsv voltage. The secondary-side power channel switch uses a back-to-back LDMOS structure to prevent reverse current flow, and its drain-source withstand voltage is not lower than a preset safety margin multiple of the single cell voltage.

[0119] It should be noted that in the application documents of this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In the application documents of this application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0120] All documents mentioned in this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the foregoing disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A bidirectional active balancing control system for multiple series-connected battery cells is characterized in that, include: The primary energy storage terminal Bsv has Vbsv as its positive terminal and ground potential GND0 as its negative terminal, serving as an energy storage element for active balancing energy transfer. A secondary battery pack consists of N battery cells B1-BN connected in series. The positive electrode voltages of each cell are VBAT1-VBATN, and the reference ground potential is GND. N is an integer greater than or equal to 2. In a flyback transformer, the two taps of the primary inductor are connected to Vbsv and Vdrn0 respectively; one end of the secondary inductor is connected to BAT1-BATN in sequence, and the other end is connected to Vdrn1-VdrnN in sequence. The primary-side control chip has its power supply terminal connected to Vbsv, its reference ground terminal connected to GND0, its rectified and regulated output terminal outputting VDD5V, its feedback input terminal receiving the optocoupler feedback signal FB, and its power terminal connected to Vdrn0. The primary-side control chip integrates a primary-side power channel switch, and controls the switching on and off according to the optocoupler feedback signal FB to charge and discharge the primary-side energy storage terminal Bsv. The secondary-side control chip has N power ports connected sequentially to VBAT1-VBATN, a reference ground connected to GND, a rectified and regulated output terminal outputting VDD, N power ports connected sequentially to Vdrn1-VdrnN, and an optocoupler drive output terminal outputting an optocoupler drive signal OPC. The secondary-side control chip integrates N secondary-side power channel switches corresponding to each battery cell, and filters out cells with high voltage to be discharged and cells with low voltage to be charged based on the voltage of each battery cell, and selects their corresponding secondary-side power channel switches respectively. The optocoupler communication module has its input end connected to the optocoupler drive signal OPC and its output end outputting the optocoupler feedback signal FB, which feeds back the charging current information of the secondary side to the primary side control chip in an electrically isolated manner. The secondary-side control chip and the primary-side control chip work together to control the flyback transformer, so that the cell to be discharged first transfers energy to the primary-side energy storage terminal Bsv for temporary storage through its corresponding secondary-side inductor and primary-side inductor, and then the energy is transferred from Bsv to the cell to be charged through the primary-side inductor and the secondary-side inductor corresponding to the cell to be charged, thereby realizing bidirectional energy transfer between any two cells in N battery cells.

2. The active balancing control system according to claim 1 is characterized in that: The flyback transformer is a planar flyback transformer; The active equalization control system also includes a primary-side voltage stabilizing filter capacitor CL0 and a secondary-side voltage stabilizing filter capacitor CL1, which are used to stabilize the operating voltage of the primary-side control chip and the secondary-side control chip, respectively.

3. The active balancing control system according to claim 1 is characterized in that, The primary-side control chip includes: The primary-side input rectifier module has its input terminal connected to the primary-side power supply voltage Vbsv, and its output terminal outputs voltage VDD5v and reference voltage Vref0. The primary-side demagnetization detection module has a voltage Vdrn0 connected to its input terminal and a demagnetization signal Demg0 output terminal. The primary-side overcurrent detection module has an input terminal connected to the current signal ICS0 sampled by the primary-side power channel switch, and an output terminal outputting an overcurrent signal OVI0. The primary-side switching frequency control module has an optocoupler feedback input terminal connected to the optocoupler feedback signal FB, and an output terminal outputting a frequency control signal Fs0. The primary-side PWM generator has its demagnetizing signal input terminal connected to the demagnetizing signal Demg0, its reference voltage input terminal connected to Vref0, its optocoupler feedback input terminal connected to the optocoupler feedback signal FB, its overcurrent signal input terminal connected to the overcurrent signal OVI0, its frequency input terminal connected to the frequency control signal Fs0, its output terminal outputting the PWM signal PWM0, and its zero-crossing signal receiving terminal receiving the signal Vzi0. The primary-side power stage module contains the primary-side power channel switch. Its pulse input terminal is connected to the PWM signal PWM0, and its power terminals are connected to the primary-side ground potential GND0 and Vdrn0 respectively. The current detection output terminal outputs the current signal ICS0, and the zero-crossing detection output terminal outputs the inductor current zero-crossing signal Vzi0.

4. The active balancing control system according to claim 1 is characterized in that, The secondary control chip includes: The cell voltage monitoring module has its input terminal connected to the positive and negative voltages of each cell in the battery pack, and its output terminal outputs a selection signal b_sel for filtering the cells to be discharged and the cells to be charged. The secondary input rectifier module has its input terminals connected to the positive and negative terminals of each battery cell in the battery pack, and its output terminals output the operating voltage VDD and the reference voltage Vref, respectively. The controller module has a selection input terminal connected to the selection signal b_sel, a reference voltage input terminal connected to the reference voltage Vref, a current input terminal connected to the current signals ICS1-ICSN, and an output terminal that outputs the PWM signal PWM_out and the optocoupler drive signal OPC, respectively. The secondary power stage module contains N secondary power channel switches. Its selection input terminal is connected to the selection signal b_sel, its pulse input terminal is connected to the PWM signal PWM_out, its power ports are respectively connected to the battery terminals BAT1-BATN, GND and Vdrn1-VdrnN, and its current detection output terminal outputs the current signals ICS1-ICSN.

5. The active balancing control system according to claim 4 is characterized in that, The controller module includes: The secondary charging side controller module has a reference voltage input terminal connected to the reference voltage Vref, a current input terminal connected to the current signal ICS1-ICSN, a selection input terminal connected to the selection signal b_sel, and an output terminal outputting the optocoupler drive signal OPC. The secondary discharge side controller module has a reference voltage input terminal connected to the reference voltage Vref, a current input terminal connected to the current signals ICS1-ICSN, a selection input terminal connected to the selection signal b_sel, a demagnetization detection input terminal connected to voltages Vdrn1-VdrnN, and an output terminal outputting the PWM signal PWM_out.

6. The active balancing control system according to claim 5 is characterized in that, The secondary charging side controller module includes: A charging-side reference voltage generator has its reference voltage input terminal connected to the reference voltage Vref, and its output terminal outputting the charging-side reference voltage signal Vref_cg; The charging-side inductor current conversion module has a selection input terminal connected to the selection signal b_sel, a current input terminal connected to the current signal ICS1-ICSN, and an output terminal outputting a voltage signal Vcs_cg. The charging-side error amplifier has a reference voltage input terminal connected to the charging-side reference voltage signal Vref_cg, a feedback input terminal connected to the voltage signal Vcs_cg, an output terminal outputting the charging-side error signal Verr_cg, and a compensation terminal connected to the voltage signal Vcmp_cg. A charging-side compensator, the input of which is connected to the voltage signal Vcmp_cg; An optocoupler driver, whose input terminal is connected to the charging side error signal Verr_cg, and whose output terminal outputs the optocoupler drive signal OPC; The charging-side inductor current conversion module selects the sampled current of the secondary inductor where the cell to be charged is located from the current signals ICS1-ICSN according to the selection signal b_sel and converts it into the voltage signal Vcs_cg. The charging-side error amplifier compares the voltage signal Vcs_cg with the charging-side reference voltage signal Vref_cg and amplifies it to output the charging-side error signal Verr_cg. The optocoupler driver generates the optocoupler drive signal OPC accordingly, and feeds it back to the primary-side control chip via the optocoupler feedback signal FB across electrical isolation through the optocoupler communication module, thus forming an isolated closed-loop control of the average charging current of the cell to be charged.

7. The active balancing control system according to claim 5 is characterized in that, The secondary discharge-side controller module includes: A discharge-side reference voltage generator, whose reference voltage input terminal is connected to the reference voltage Vref, and whose output terminal outputs the discharge-side reference voltage signal Vref_discg; The discharge-side inductor current conversion module has a selection input terminal connected to the selection signal b_sel, a current input terminal connected to the current signal ICS1-ICSN, an output terminal outputting a voltage signal Vcs_discg, and a current output terminal outputting a current signal ICS_sel selected by the selection signal b_sel. The discharge-side error amplifier has a reference voltage input terminal connected to the discharge-side reference voltage signal Vref_discg, a feedback input terminal connected to the voltage signal Vcs_discg, an output terminal outputting the discharge-side error signal Verr_discg, and a compensation terminal connected to the voltage signal Vcmp_discg. A discharge-side compensator, the input of which is connected to the voltage signal Vcmp_discg; The secondary demagnetization detection module has its detection input terminals connected to the voltages Vdrn1-VdrnN respectively, its selection input terminal connected to the selection signal b_sel, and its output terminal outputting the secondary demagnetization signal Demg_discg. The secondary overcurrent detection module has its input terminal connected to the current signal ICS_sel and its output terminal outputting the secondary overcurrent signal OVI_discg. The secondary-side switching frequency control module has its input terminal connected to the discharge-side error signal Verr_discg and its output terminal outputting the secondary-side frequency control signal Fs_discg. The secondary-side PWM generator has its error signal input terminal connected to the discharge-side error signal Verr_discg, its demagnetization signal input terminal connected to the secondary-side demagnetization signal Demg_discg, its reference voltage input terminal connected to the discharge-side reference voltage signal Vref_discg, its overcurrent signal input terminal connected to the secondary-side overcurrent signal OVI_discg, its frequency input terminal connected to the secondary-side frequency control signal Fs_discg, and its output terminal outputting the PWM signal PWM_out. The secondary PWM generator adjusts the duty cycle of the PWM signal PWM_out according to the discharge-side error signal Verr_discg to control the average discharge current of the cell to be discharged to the expected value.

8. The active balancing control system according to claim 5 is characterized in that: The charging-side reference voltage signal Vref_cg output by the charging-side reference voltage generator and the discharging-side reference voltage signal Vref_discg output by the discharging-side reference voltage generator are both reference voltage signals with configurable ranges. The average charging current level of the cell to be charged is adjusted by configuring the level of the charging-side reference voltage signal Vref_cg; the average discharging current level of the cell to be discharged is adjusted by configuring the level of the discharging-side reference voltage signal Vref_discg.

9. The active balancing control system according to claim 4 is characterized in that, The secondary power stage module includes: The temperature monitoring module has a reference voltage input terminal connected to the reference voltage Vref, and an output terminal that outputs a temperature protection signal OTP_discg; The non-overlapping logic module has its pulse input terminal connected to the PWM signal PWM_out, its temperature protection input terminal connected to the temperature protection signal OTP_discg, and its output terminal outputting non-overlapping pulse signals PWM_discg and PWM_cg respectively, so as to avoid overlapping conduction between the charging branch and the discharging branch in the same power channel; The power module has its pulse input terminals connected to the pulse signals PWM_discg and PWM_cg respectively, its selection input terminal connected to the selection signal b_sel, its reference voltage input terminal connected to the reference voltage Vref, its current detection output terminal outputting the current signals ICS1-ICSN, and its power ports connected to GND, BAT1-BAT(N-1), and Vdrn1-VdrnN respectively.

10. The active balancing control system according to claim 9 is characterized in that: The power module includes N power channels, namely power channel 1 to power channel N, and each of the N power channels integrates the N secondary power channel switches. The pulse input terminals of the N power channels are respectively connected to the pulse signals PWM_discg and PWM_cg, the selection input terminals are all connected to the selection signal b_sel, the reference voltage input terminals are all connected to the reference voltage Vref, and the current detection output terminals output the current signals ICS1-ICSN respectively. The power ports of power channel 1 are connected to GND and Vdrn1 respectively, and the power ports of power channel j are connected to BAT(j-1) and Vdrnj respectively. .

11. A bidirectional active balancing control method applied to the active balancing control system according to any one of claims 1-10, characterized in that, Includes the following steps: Step 1: The primary-side control chip rectifies the input voltage Vbsv to generate the primary-side operating voltage domain VDD5v and the primary-side reference voltage Vref0; the secondary-side control chip rectifies the input battery cell voltages VBAT1-VBATN to generate the secondary-side operating voltage domain VDD and the secondary-side reference voltage Vref. VDD5v, Vref0, VDD, and Vref provide the operating and reference voltages for the primary-side control chip and the secondary-side control chip, respectively, in subsequent steps. Step 2: Under the operating voltage established in Step 1, the secondary-side control chip detects the voltage of each battery cell, selects the battery cells with higher voltage as cells to be discharged and the battery cells with lower voltage as cells to be charged, and outputs a selection signal b_sel; based on the selection signal b_sel, the secondary-side control chip opens the secondary-side power channel switch corresponding to the cell to be discharged, so that the cell to be discharged begins to charge the secondary-side inductor of the flyback transformer, and controls the average discharge current of the cell to be discharged according to the sampling current of the secondary-side inductor; Step 3: When the average discharge current value controlled in Step 2 reaches the expected value, the secondary control chip will turn off the secondary power channel switch corresponding to the single cell to be discharged, and stop the charging of the secondary inductor. At the same time, the primary-side control chip turns on the primary-side power channel switch, so that the energy stored in the flyback transformer in the second step is transferred from the secondary-side inductor to the primary-side energy storage terminal Bsv through the primary-side inductor. The primary-side inductor current gradually decreases and charges Bsv. Step 4: During Step 3, when the primary-side control chip detects that the current of the primary-side inductor has crossed zero, it automatically enters the charging mode. The primary-side power channel switch remains open, the current direction of the primary-side inductor reverses and the current value gradually increases, and the primary-side energy storage terminal Bsv begins to discharge to the primary-side inductor. The primary-side control chip controls the primary-side power channel switch according to the current value of the primary-side inductor and the optocoupler feedback signal FB. Controlled by the optocoupler feedback signal FB, when the current value of the primary-side inductor reaches the level limited by the optocoupler feedback signal FB, the primary-side control chip closes the primary-side power channel switch and stops charging the primary-side inductor. Step 5: After the primary-side power channel switch is closed in Step 4, the secondary-side control chip, based on the selection signal b_sel output in Step 2, opens the secondary-side power channel switch corresponding to the cell to be charged. This allows the energy stored in the primary-side inductor in Step 4 to be transferred to the secondary-side inductor corresponding to the cell to be charged via the flyback transformer, thus charging the cell. Simultaneously, the secondary-side control chip detects the charging inductor current to maintain the average charging current value at the expected level. The charging current information is converted into the optocoupler feedback signal FB via the optocoupler communication module through the optocoupler drive signal OPC and sent to the primary-side control chip. The optocoupler feedback signal FB serves as the basis for the primary-side control chip to turn off the primary-side power channel switch in Step 4. Step 6: When the charging current of the secondary inductor mentioned in Step 5 returns to zero, the secondary control chip turns off the secondary power channel switch corresponding to the single cell to be charged. Once the secondary control chip detects that the flyback transformer has completed demagnetization, it returns to the second step and repeats the process to start the next balancing cycle. Active balancing ends when the voltage difference between each battery cell converges to the same value.

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