Lithium battery energy equalization circuit and control method

Abstract

The application discloses a lithium battery energy equalization circuit and a control method, and relates to the technical field of battery management. The lithium battery energy equalization circuit comprises a plurality of equalization modules, a battery pack common bus and a control unit. Each equalization module comprises two series-connected battery monomers, a switch control circuit and a flyback conversion unit. The control unit establishes an energy transmission path between the battery monomers and between the equalization module and the battery pack common bus by controlling the conduction state of a power switch tube. The flyback conversion unit comprises a flyback transformer, which is used for realizing bidirectional energy transmission between the battery monomers in the equalization module and bidirectional energy exchange between the equalization module and the battery pack common bus. The plurality of equalization modules can simultaneously release energy to the battery pack common bus or simultaneously obtain energy from the battery pack common bus under the control of the control unit. The application further discloses a control method based on the above lithium battery energy equalization circuit.

Description

Technical Field

[0001] This application relates to the field of battery management technology, and in particular to a lithium battery energy balancing circuit and control method. Background Technology

[0002] With the development of new energy technologies, lithium batteries, due to their high energy density and long cycle life, are widely used in electric vehicles, communication base stations, energy storage systems, and other fields. Since practical applications typically require multiple individual cells to be connected in series to form a battery pack to meet voltage and capacity requirements, the consistency management of the individual cells within the battery pack becomes a crucial factor affecting the performance and reliability of the battery system.

[0003] In existing lithium battery pack management technologies, balancing circuits are typically used to regulate voltage or charge differences between different cells. Current active balancing schemes are mostly based on inductors, capacitors, or flyback converter structures, using control switching devices to achieve energy transfer between cells or parts of the module. Among these, balancing circuits using flyback converter structures can achieve isolated energy transfer and are applied in battery pack balancing management.

[0004] However, existing equalization circuits based on flyback converter structures can usually only achieve energy transfer within a single equalization module or between a single module and the target battery. It is difficult for multiple equalization modules to coordinate and participate in the overall energy regulation of the battery pack, and they cannot meet the needs of multiple modules in a large-scale series battery pack to exchange energy simultaneously.

[0005] Therefore, providing a lithium battery balancing circuit that can support coordinated energy exchange between multiple balancing modules and the battery pack is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this application is to provide a lithium battery energy balancing circuit and control method to solve the technical problem that multiple balancing modules in the existing flyback converter balancing circuit cannot cooperate in the overall energy regulation of the battery pack.

[0007] To address the aforementioned technical problems, this application provides a lithium battery energy balancing circuit, comprising: multiple balancing modules, a common bus of the battery pack connected to the multiple balancing modules, and a control unit; Each equalization module includes two battery cells connected in series, a switch control circuit, and a flyback converter unit connected to the battery cells. The switching control circuit includes multiple power switching transistors. The control unit is connected to the power switching transistors and controls the conduction state of different power switching transistors, so that the equalization circuit forms energy transmission paths between battery cells, energy transmission paths from the equalization module to the common bus of the battery pack, and energy transmission paths from the common bus of the battery pack to the equalization module. The flyback converter unit includes a flyback transformer, which is connected between the individual battery cell and the common bus of the battery pack to realize bidirectional energy transfer between individual battery cells within the equalization module, as well as bidirectional energy exchange between the equalization module and the common bus of the battery pack. The multiple equalization modules are respectively connected to the common bus of the battery pack, and the control unit controls the multiple equalization modules to simultaneously release energy to the common bus of the battery pack, or simultaneously obtain energy from the common bus of the battery pack.

[0008] Optionally, the power switch is a power switch with an anti-parallel diode; In the off state, the power switch forms a unidirectional conduction path through the anti-parallel diode, and in the on state, it forms a low-impedance energy transmission path.

[0009] Optionally, the power switching transistor includes: a unit control switch, a transformer primary-side control switch, and a common bus control switch; The unit control switch is used to control the connection between the battery cell and the flyback transformer, so as to realize the energy transfer between the battery cells inside the equalization module. The transformer primary control switch is used to control the on / off of the primary current of the flyback transformer, so as to control the flyback converter unit to perform energy conversion. The common bus control switch is used to control the connection status between the secondary side of the flyback transformer and the common bus of the battery pack, so as to realize the energy exchange between the equalization module and the common bus of the battery pack.

[0010] Optionally, the control unit forms a bidirectional energy transfer path between battery cells within the equalization module by controlling the unit control switch, the transformer primary-side control switch, and the common bus control switch, so as to transfer energy from battery cells with higher voltage to battery cells with lower voltage.

[0011] Optionally, the control unit controls the unit control switch, transformer primary control switch, and common bus control switch in multiple equalization modules, so that the primary sides of the multiple flyback converter units respectively obtain energy from the battery cells of the corresponding equalization modules and simultaneously release energy to the common bus of the battery pack through the secondary sides.

[0012] Optionally, the control unit controls the unit control switch, the transformer primary-side control switch, and the common bus control switch in multiple equalization modules, so that multiple flyback converter units simultaneously obtain energy from the battery pack common bus and release energy to the battery cells in the corresponding equalization modules.

[0013] Optionally, the excitation inductance of the flyback transformer serves as both the energy storage inductance for energy transfer between the individual battery cells and the primary winding of the transformer for energy exchange between the equalization module and the common bus of the battery pack.

[0014] Optionally, the control unit includes an independent control subunit corresponding to each equalization module, and each control subunit independently controls the conduction state of the power switch in the corresponding equalization module to enable parallel equalization control of multiple equalization modules.

[0015] Furthermore, to achieve the above objectives, the present invention also provides a lithium battery energy balancing circuit control method, applied to the aforementioned lithium battery energy balancing circuit, comprising: Obtain the voltage information of individual battery cells within each equalization module; Determine whether there is a voltage difference between the individual battery cells based on the voltage information; When a voltage difference is detected between battery cells within the same equalization module, the corresponding flyback converter unit is controlled to operate, so that the battery cell with higher voltage can transfer energy to the battery cell with lower voltage. When the voltage of a single battery cell corresponding to multiple equalization modules is detected to be higher than the target state, the multiple equalization modules are controlled to release energy to the common bus of the battery pack simultaneously. When it is detected that the voltage of a single battery cell corresponding to multiple equalization modules is lower than the target state, the multiple equalization modules are controlled to simultaneously obtain energy from the common bus of the battery pack.

[0016] Optionally, when the voltage or state of charge of a single battery cell corresponding to multiple equalization modules is detected to be higher than the target state, the multiple equalization modules are controlled to work synchronously, so that the multiple equalization modules simultaneously output energy to the common bus of the battery pack through the corresponding flyback converter unit. When the voltage or state of charge of a single battery cell corresponding to multiple equalization modules is detected to be lower than the target state, the multiple equalization modules are controlled to work synchronously, so that the multiple equalization modules can simultaneously obtain energy from the common bus of the battery pack through the corresponding flyback converter unit.

[0017] The lithium battery energy balancing circuit provided in this application sets up multiple balancing modules, each connected to a common bus of the battery pack, enabling energy exchange between the modules via the common bus. Simultaneously, a control unit coordinates and controls these modules, allowing them to simultaneously release energy to or from the common bus, thus enabling multiple modules to participate in the overall energy regulation of the battery pack and improving the synergy of the balancing process. Each balancing module incorporates a flyback converter unit, enabling bidirectional energy transfer between individual cells within the module and bidirectional energy exchange between the module and the common bus. The control unit manages the conduction state of the power switching transistors, allowing the balancing circuit to create multiple energy transfer paths between individual cells and between the module and the common bus, selecting the appropriate energy transfer mode based on different battery states, thus improving the flexibility of balancing control. Furthermore, the balancing modules can be expanded and configured according to the battery pack size, achieving matching applications in battery systems with different numbers of series-connected cells, improving the adaptability of the balancing circuit.

[0018] In addition, this application also provides a lithium battery energy balancing circuit control method, which corresponds to the above-mentioned lithium battery energy balancing circuit and has the same effect. Attached Figure Description

[0019] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall topology of a lithium battery energy balancing circuit provided in an embodiment of this application; Figure 2 A schematic diagram illustrating a path for energy transfer from a first battery cell to a second battery cell, provided as an embodiment of this application; Figure 3 A schematic diagram illustrating a path for energy transfer from a second battery cell to a first battery cell, provided as an embodiment of this application; Figure 4 This application provides a schematic diagram of multiple equalization modules releasing energy to the common bus of the battery pack. Figure 5 This application provides a schematic diagram of energy transmission from a common bus of a battery pack to multiple equalization modules. Figure 6A flowchart of a lithium battery energy balancing circuit control method provided in an embodiment of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0022] The core of this application is to provide a lithium battery energy balancing circuit and control method.

[0023] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown, this embodiment proposes a lithium battery energy balancing circuit, including: multiple balancing modules 11, a battery pack common bus connected to the multiple balancing modules 11, and a control unit; Each equalization module 11 includes two battery cells connected in series, a switch control circuit, and a flyback converter unit connected to the battery cells. The switching control circuit includes multiple power switching transistors. The control unit is connected to the power switching transistors and controls the conduction state of different power switching transistors, so that the equalization circuit forms the energy transmission path between battery cells, the energy transmission path from the equalization module 11 to the battery pack common bus, and the energy transmission path from the battery pack common bus to the equalization module 11. The flyback converter unit includes a flyback transformer, which is connected between the individual battery cells and the common bus of the battery pack to realize bidirectional energy transfer between the individual battery cells inside the equalization module 11, as well as bidirectional energy exchange between the equalization module 11 and the common bus of the battery pack. Multiple equalization modules 11 are connected to the common bus of the battery pack respectively. The control unit controls the multiple equalization modules 11 to simultaneously release energy to the common bus of the battery pack or simultaneously obtain energy from the common bus of the battery pack.

[0025] Specifically, the number of equalization modules 11 is n / 2. Each equalization module 11 includes two battery cells connected in series, where n is the total number of battery cells in the battery pack, and n is an integer multiple of 4. For example, when the battery pack has 4 series cells, it contains 2 equalization modules 11; when it has 8 series cells, it contains 4 equalization modules 11; when it has 12 series cells, it contains 6 equalization modules 11, and so on.

[0026] Each equalization module 11 is connected to the battery pack common bus via a corresponding flyback converter unit. The battery pack common bus includes a positive bus and a negative bus, which are connected to the positive and negative terminals of the battery pack, respectively.

[0027] The control unit is connected to the power switching transistors in each equalization module 11 to control the conduction state of different power switching transistors so as to form different energy transmission paths.

[0028] Each equalization module 11 includes two battery cells connected in series, a switching control circuit, and a flyback converter unit.

[0029] The switching control circuit includes multiple power switching transistors. These power switching transistors are metal-oxide-semiconductor field-effect transistors (MOSFETs) with anti-parallel diodes. In the on-state, a MOSFET is equivalent to a low-impedance wire; in the off-state, its anti-parallel diodes form a unidirectional conduction path.

[0030] The flyback converter unit includes a flyback transformer. The primary side of the flyback transformer is connected to two individual battery cells, and the secondary side is connected to the positive and negative busbars of the common busbar of the battery pack.

[0031] The control unit controls the conduction state of different power switches, enabling the equalization circuit to form the following three independent and controllable energy transfer paths: Path 1: Energy transfer path between individual battery cells. This path enables bidirectional energy transfer between two individual battery cells within the equalization module 11. When a voltage difference exists between two individual battery cells within the module, the corresponding power switch is turned on, allowing energy to be transferred from the battery cell with the higher voltage to the battery cell with the lower voltage.

[0032] Path 2: The path for balancing module 11 to release energy to the battery pack common bus. This path enables multiple balancing modules 11 to simultaneously release energy to the battery pack common bus. When the voltage of the individual battery cells corresponding to multiple balancing modules 11 is higher than the average voltage of the battery pack, the primary side of each module's flyback converter unit obtains energy from the corresponding individual battery cell, while the secondary side simultaneously releases energy to the battery pack common bus.

[0033] Path 3: The path for obtaining energy from the battery pack common bus to the equalization module 11. This path enables multiple equalization modules 11 to simultaneously obtain energy from the battery pack common bus. When the voltage of the individual battery cells corresponding to multiple equalization modules 11 is lower than the average voltage of the battery pack, the secondary side of the flyback converter unit of each module simultaneously obtains energy from the battery pack common bus, and the primary side releases energy to the corresponding individual battery cells.

[0034] Based on the overall architecture described above, the following will further elaborate on... Figure 1 The circuit topology shown is explained below. Figure 1Taking a 4-cell battery as an example, it includes two equalization modules 11. The left module contains batteries B1 and B2, and the right module contains batteries B3 and B4. Each module contains a flyback transformer. The primary side of the transformer connects to the two batteries within the module, and the secondary side is connected to the battery pack's common bus via a common bus control switch. The positions and connections of each switch are clearly shown in the attached diagram. The unit control switch is located on the left side of the module and controls the connection between the individual battery cells and the transformer's primary side; the transformer primary side control switches are located at different nodes between the transformer's primary side and the batteries; and the common bus control switch is located between the transformer's secondary side and the bus.

[0035] Each equalization module 11 adopts a standardized interface design, and the modules are connected through a unified electrical interface and communication protocol. The standardized interface includes a power interface and a communication interface. When it is necessary to expand the battery pack capacity, only the standardized equalization module 11 needs to be added and connected to the battery pack common bus. There is no need to modify the hardware and software of the existing modules, realizing plug-and-play expansion.

[0036] Building upon modular expansion, a hot-swap protection mechanism is added. Each equalization module 11 has a pre-charging circuit and a soft-start circuit at its power interface. When a new module is connected, the pre-charging circuit pre-charges the capacitors within the module to avoid a large current surge upon connection. The soft-start circuit gradually establishes the power switch, preventing voltage surges from impacting individual battery cells and the bus. This hot-swap protection mechanism allows for the safe addition or replacement of equalization modules 11 during system operation, improving system maintainability and availability.

[0037] The lithium battery energy balancing circuit provided in this application sets up multiple balancing modules 11 and connects them to the common bus of the battery pack, enabling energy exchange between the balancing modules 11 through the common bus. Simultaneously, a control unit coordinates and controls the multiple balancing modules 11, allowing them to simultaneously release energy to or obtain energy from the common bus, thus enabling multiple balancing modules 11 to participate in the overall energy regulation of the battery pack and improving the synergy of the battery pack balancing process. Each balancing module 11 includes a flyback converter unit, enabling bidirectional energy transfer between individual battery cells within the balancing module 11 and bidirectional energy exchange between the balancing module 11 and the common bus of the battery pack. By controlling the conduction state of the power switch transistors through the control unit, the balancing circuit can form multiple energy transfer paths between individual battery cells and between the balancing module 11 and the common bus of the battery pack, allowing for the selection of the appropriate energy transfer mode based on different battery states, thus improving the flexibility of balancing control. In addition, the equalization module 11 can be expanded according to the size of the battery pack to achieve matching application in battery systems composed of different numbers of series-connected battery cells, thereby improving the adaptability of the equalization circuit.

[0038] Specifically, the power switch is a power switch with an anti-parallel diode; In the off state, the power switch forms a unidirectional conduction path through the anti-parallel diode, and in the on state, it forms a low-impedance energy transfer path.

[0039] A MOSFET consists of three electrodes: a gate, a source, and a drain, as well as a body diode integrated inside the device, also known as an anti-parallel diode. The anode of the body diode is connected to the source, and the cathode is connected to the drain, in parallel with the conductive channel of the MOSFET.

[0040] In the on-state, when the gate and source voltages are higher than the threshold voltage, the MOSFET channel is turned on, forming a low-impedance conductive path between the drain and source. The equivalent resistance is the on-resistance Rds(on), typically ranging from a few milliohms to tens of milliohms. At this time, the power switch is equivalent to a low-impedance wire, allowing current to flow bidirectionally.

[0041] In the off state, the MOSFET channel is turned off when the gate and source voltages are below the threshold voltage. At this time, if the drain and source voltages forward bias the body diode (i.e., the drain voltage is lower than the source voltage), the body diode conducts, forming a unidirectional conduction path; if the drain and source voltages reverse bias the body diode, the body diode is turned off, and the power switch exhibits a high-impedance state.

[0042] One of the core innovations of this invention is to utilize the unidirectional conduction characteristic of the power switch in the off state, combined with the low impedance characteristic in the on state, to reconstruct the energy transmission path through different on-off combinations.

[0043] For example, when forming an energy transfer path between battery cells, some power switches are in the on state, equivalent to wires; others are in the off state, equivalent to unidirectional diodes. The directionality of the anti-parallel diodes of the power switches in the off state determines the direction of current flow, thus cooperating with the on power switches to form a complete energy transfer loop.

[0044] Specifically, the power switching transistors include: unit control switches, transformer primary-side control switches, and common bus control switches; The unit control switch is used to control the connection between the battery cell and the flyback transformer in order to realize the energy transfer between the battery cells inside the equalization module 11. The transformer primary control switch is used to control the on / off of the primary current of the flyback transformer, so as to control the energy conversion of the flyback converter unit; The common bus control switch is used to control the connection status between the secondary side of the flyback transformer and the common bus of the battery pack, so as to realize the energy exchange between the equalization module 11 and the common bus of the battery pack.

[0045] The unit control switch is located inside each equalization module 11 and is used to control the connection between the battery cell and the flyback transformer to realize the energy transfer between the battery cells inside the equalization module 11.

[0046] In an equalization module 11, the unit control switches include a first unit control switch and a second unit control switch. The first unit control switch connects the positive terminal of the first battery cell to one end of the primary winding of the transformer, and the second unit control switch connects the other end of the primary winding of the transformer to either the positive or negative terminal of the second battery cell, depending on the specific topology. By controlling the on and off states of the first and second unit control switches, the flow of energy from the first battery cell to the second battery cell, or vice versa, can be controlled.

[0047] The transformer primary control switch is set at different connection nodes between the primary side of the flyback transformer and the two battery cells of the corresponding equalization module 11. It is used to switch the primary current path and control the flyback converter unit to perform energy conversion.

[0048] The transformer primary control switch includes multiple switches, each located at a different connection point on the transformer primary winding. For example, one switch connects the lower end of the transformer primary winding to the negative terminal of the first battery cell, another switch connects the upper end of the transformer primary winding to the positive terminal of the second battery cell, and a third switch connects the midpoint of the transformer primary winding to the connection point between the two battery cells. By using different combinations of these switches, the connection method between the transformer primary winding and the battery cells can be changed, achieving different energy conversion modes.

[0049] The common bus control switch is located between the secondary side of the flyback transformer and the common bus of the battery pack. It is used to control the connection status between the secondary side and the common bus of the battery pack, so as to realize the energy exchange between the equalization module 11 and the common bus of the battery pack.

[0050] The common bus control switch includes a switch connecting the upper end of the transformer secondary side to the positive terminal of the battery pack common bus, and a switch connecting the lower end of the transformer secondary side to the negative terminal of the battery pack common bus. When the common bus control switch is on, the transformer secondary side and the battery pack common bus are electrically connected, and energy can be transferred between the module and the entire battery pack; when the common bus control switch is off, the transformer secondary side is isolated from the bus, and the module operates independently.

[0051] The combination of the on / off states of the three types of switches determines the current energy transmission path. Based on the above principle, the switching states of each path are explained in detail below with reference to the accompanying drawings.

[0052] like Figure 1 As shown, the switch control circuit in this embodiment includes multiple power switching transistors, including a unit control switch, a transformer primary-side control switch, and a common bus control switch.

[0053] The positive terminal of battery cell B1 is connected to the drain of the first unit control switch Q1, and the negative terminal of B1 is connected to the positive terminal of battery cell B2. The positive terminal of battery cell B2 is connected to both the source of the second unit control switch Q2 and the source of the transformer primary control switch Q3, and the negative terminal of B2 is connected to the drain of the transformer primary control switch Q8.

[0054] The source of the first unit control switch Q1 is connected to the source of the transformer primary control switch Q8 and the lower end of the transformer primary winding. The gate of Q1 is connected to the pulse-width modulation (PWM) output of the control unit.

[0055] The drain of the second unit control switch Q2 is connected to the source of the transformer primary control switch Q6 and the upper end of the transformer primary winding. The gate of Q2 is connected to the PWM output terminal of the control unit.

[0056] The drain of the transformer primary control switch Q3 is connected to the positive terminal of the battery cell B2, and the source of Q3 is connected to the lower end of the transformer primary winding. The gate of Q3 is connected to the drive output terminal of the control unit.

[0057] The drain of the transformer primary control switch Q6 is connected to the source of the common bus control switch Q7 and the upper end of the transformer secondary winding. The source of Q6 is connected to the upper end of the transformer primary winding. The gate of Q6 is connected to the drive output terminal of the control unit.

[0058] The source of transformer primary control switch Q8 is connected to the source of first unit control switch Q1 and the lower end of transformer primary winding, and the drain of Q8 is connected to the negative terminal of battery cell B2. The gate of Q8 is connected to the drive output terminal of control unit.

[0059] The upper end of the primary winding of the flyback transformer is connected to the source of the primary control switch Q6 and the drain of the second unit control switch Q2. The lower end of the primary winding is connected to the source of the first unit control switch Q1, the source of the primary control switch Q3, and the source of the primary control switch Q8. The upper end of the secondary winding is connected to the drain of the primary control switch Q6 and the source of the common bus control switch Q7. The lower end of the secondary winding is connected to the drain of the common bus control switch Q5.

[0060] The drain of the common bus control switch Q4 is connected to the positive terminal of the battery pack common bus, and the source of Q4 is connected to the drain of the transformer primary control switch Q6 and the upper end of the transformer secondary winding. The gate of Q4 is connected to the drive output terminal of the control unit.

[0061] The source of the common bus control switch Q5 is connected to the negative terminal of the battery pack's common bus or the positive terminal of a battery cell in an adjacent module, and the drain of Q5 is connected to the lower end of the transformer's secondary winding. The gate of Q5 is connected to the drive output terminal of the control unit.

[0062] The drain of the common bus control switch Q7 is connected to the positive terminal of the battery pack common bus. The source of Q7 is connected to the drain of the transformer primary control switch Q6, the source of the common bus control switch Q4, and the upper end of the transformer secondary winding. The gate of Q7 is connected to the PWM output terminal of the control unit.

[0063] Specifically, Q4 and Q5 are used to form a secondary bidirectional energy transmission loop, and Q7 is used to control the connection between the secondary loop and the common bus.

[0064] Specifically, in each equalization module 11, the first unit control switch and the second unit control switch are respectively disposed between the two battery cells and the flyback converter unit, corresponding to Q1 and Q2 respectively in the embodiment shown in the attached figure. Q1 is used to control the connection state between the first battery cell B1 and the flyback transformer, and Q2 is used to control the connection state between the second battery cell B2 and the flyback transformer.

[0065] When Q1 is turned on and Q2 is operating in a preset state, the first battery cell B1 can provide energy to the flyback transformer; when Q2 is turned on and Q1 is operating in a preset state, the second battery cell B2 can provide energy to the flyback transformer. Thus, by changing the conduction combination of Q1 and Q2, bidirectional energy transfer between the two battery cells can be achieved.

[0066] Furthermore, the primary-side control switch of the transformer is set in the primary-side circuit of the flyback transformer, corresponding to Q3, Q6, and Q8 in the embodiment shown in the attached figure. This switch is used to control the establishment and release process of the primary-side excitation current of the flyback transformer. When the primary-side control switch is turned on, the excitation inductor of the flyback transformer stores energy from the individual battery cells; when the primary-side control switch is turned off, the energy stored in the excitation inductor is coupled to the target side through the transformer, realizing energy conversion.

[0067] Furthermore, a common bus control switch is located between the secondary side of the flyback transformer and the common bus of the battery pack, corresponding to Q4, Q5, and Q7 in the embodiment shown in the attached drawings. This switch controls the connection between the secondary side of the flyback transformer and the common bus of the battery pack. When the equalization module 11 needs to release energy to the common bus of the battery pack, Q4, Q5, and Q7 are turned on, forming an energy transmission path between the secondary side of the flyback transformer and the common bus. When the common bus of the battery pack needs to replenish energy to the equalization module 11, the conduction combination of Q4, Q5, and Q7 is adjusted, allowing the energy from the common bus to be transmitted to the corresponding battery cell via the flyback converter unit.

[0068] It should be noted that the specific numbers Q1 to Q8 in the attached figures are only used to illustrate the positional relationship of each power switch in one embodiment and do not constitute a limitation on the number of switches or the connection method. In other embodiments, the number of power switches and the connection method can be adjusted according to the number of battery cells, the flyback converter structure, and the control strategy, as long as bidirectional energy exchange between battery cells and between the equalization module 11 and the common bus of the battery pack can be achieved.

[0069] Specifically, when the control unit detects a voltage difference between two battery cells within the same equalization module 11, the control unit first compares the voltage values ​​or state of charge of the two battery cells to determine the direction of energy transfer.

[0070] If the voltage of the first battery cell is higher than that of the second battery cell, the control unit controls the corresponding unit control switch and the transformer primary side control switch to be turned on, while keeping the common bus control switch off, so that the flyback converter unit only participates in the energy transmission within the equalization module 11.

[0071] At this time, the first battery cell provides electrical energy to the primary winding of the flyback transformer, and the primary winding establishes an excitation current and completes magnetic field energy storage. When the control unit turns off the primary control switch of the transformer, the primary excitation current disappears, and the magnetic field energy is coupled to the corresponding release circuit on the primary side through the secondary side, and finally transferred to the second battery cell, realizing the energy transfer from the first battery cell to the second battery cell.

[0072] Similarly, when the voltage of the second battery cell is higher than that of the first battery cell, it is only necessary to adjust the conduction combination of the corresponding unit control switch to establish an energy transmission path in the opposite direction and realize the energy transfer from the second battery cell to the first battery cell.

[0073] like Figure 2 , 3 As shown, when the voltage of the first battery cell B1 is higher than that of the second battery cell B2, the control unit controls Q1 to turn on; Q6 to turn on; Q3 to turn on; Q8 to turn off; Q4 to turn off; Q5 to turn off; Q7 to turn off.

[0074] At this point, the first battery cell B1, Q1, Q3, Q6, and the primary side of the flyback transformer T1 form an energy storage circuit. The output current of the first battery cell B1 enters the primary side of the flyback transformer T1 through Q1, causing the magnetizing inductor to store energy.

[0075] Once the primary side energy storage is complete, the control unit controls the primary side control switch to turn off, and the magnetic field energy in the flyback transformer T1 is released through the secondary side and transmitted to the second battery cell B2 through the corresponding freewheeling paths Q4 and Q5.

[0076] like Figure 3As shown, when the voltage of the second battery cell B2 is higher than that of the first battery cell B1, the control unit adjusts the switching state to reverse the energy transmission direction. Specifically, Q2 is on; Q8 is on; Q6 is on; Q3 is off; Q4 is off; Q5 is off; Q7 is off. At this time, the second battery cell B2 supplies energy to the primary side of the flyback transformer T1 through Q2, Q8, and Q6.

[0077] After the primary side completes energy storage: Q6 is turned off; the secondary side of the flyback transformer T1 releases energy and transmits it to the first battery cell B1 through the corresponding path.

[0078] Formation: Energy transfer path from B2 to T1 to B1.

[0079] It should be noted that the common bus control switch remains off throughout the equalization process. Therefore, the flyback converter unit does not exchange energy with the battery pack common bus, but is only used for bidirectional energy transfer between two battery cells within the equalization module 11.

[0080] Furthermore, to ensure a smooth balancing process, the control unit can dynamically adjust the PWM duty cycle or switching frequency based on the voltage difference between the two battery cells, so that the energy transferred per unit time varies with the voltage difference. When the voltage difference is large, the duty cycle can be increased or the switching frequency can be appropriately increased to increase the balancing current; as the voltage difference gradually decreases, the duty cycle can be decreased to make the balancing process smoother.

[0081] On the other hand, in other embodiments, the control unit can also determine the equilibration timing by comprehensively considering parameters such as temperature, state of charge, and health status, rather than solely relying on the voltage difference. This embodiment does not impose any limitations on this.

[0082] In summary, this embodiment utilizes the flyback converter unit to establish a bidirectional energy transmission path within the equalization module 11, enabling active equalization within the module without the need for the battery pack's common bus. This provides a foundation for multiple equalization modules 11 to collaboratively participate in the overall energy regulation of the battery pack.

[0083] In the above embodiments, the bidirectional energy transfer method between the two battery cells within the equalization module 11 has been described. It should be noted that when there is energy surplus in multiple equalization modules 11, relying solely on internal equalization within the modules is insufficient to redistribute the energy of the entire battery pack. The control unit controls the unit control switches, transformer primary-side control switches, and common bus control switches in the multiple equalization modules 11, enabling the primary sides of the multiple flyback converter units to obtain energy from the corresponding battery cells in the equalization module 11 and simultaneously release energy to the common bus of the battery pack through their secondary sides.

[0084] like Figure 4As shown, when the voltage of the battery cells corresponding to the multiple equalization modules 11 is higher than the target state, the control unit controls the multiple equalization modules 11 to enter the common bus energy release mode.

[0085] Taking a single equalization module 11 as an example: Energy storage stage control: Q1 is turned on; Q6 is turned on; Q3 is turned on; Q8 is turned off; Q7 is turned off.

[0086] At this time: energy from the B1 / B2 side enters the primary side of T1, and the T1 magnetizing inductor completes energy storage.

[0087] Release phase control: Q6 is off; Q4 is on; Q5 is on; Q7 is on.

[0088] At this time: the secondary side of T1 is connected to the common bus of the battery pack. The secondary side of the flyback transformer outputs energy to the common bus.

[0089] Multiple equalization modules 11 all execute the above control process, so multiple flyback converter units can simultaneously release energy to the common bus.

[0090] Specifically, the control unit controls the unit control switch, transformer primary control switch and common bus control switch in each equalization module 11 to be turned on according to a preset timing sequence, so that the primary side of the flyback converter unit in each equalization module 11 is connected to the battery cell in the corresponding equalization module 11, and the primary side of multiple flyback transformers absorbs energy from the corresponding battery cell and establishes excitation current.

[0091] As the primary-side energy storage ends, the control unit shuts off the primary-side control switch of the control transformer, and the flyback transformer enters the energy release phase. Since the common bus control switch remains on, the secondary sides of each flyback transformer are connected to the common bus of the battery pack, and the secondary sides of each flyback transformer output energy to the common bus of the battery pack almost simultaneously, thereby realizing that multiple equalization modules 11 release energy to the common bus of the battery pack synchronously.

[0092] It should be noted that synchronous release here does not require all equalization modules 11 to be turned on absolutely simultaneously, but rather refers to multiple equalization modules 11 participating in energy exchange on the common bus within the same control cycle. Those skilled in the art can employ a strictly synchronous control method, or a time-division control method or an interleaved control method, depending on the controller's performance, to allow multiple equalization modules 11 to output energy to the common bus sequentially, thereby reducing instantaneous current fluctuations on the common bus. This embodiment does not impose strict limitations on this.

[0093] Furthermore, since multiple equalization modules 11 are connected to the same battery pack common bus through their respective corresponding flyback converter units, no additional point-to-point connections are needed between the multiple equalization modules 11 to complete the overall energy collection. Compared to traditional flyback equalization circuits that can only achieve one-to-one energy transfer between individual cells or modules, this embodiment establishes an energy exchange channel through the common bus for multiple equalization modules 11 to participate in, enabling multiple equalization modules 11 to participate in the overall equalization of the battery pack simultaneously, thereby improving the energy regulation capability of the entire system.

[0094] On the other hand, to avoid excessive common bus current caused by multiple flyback converter units operating simultaneously, the control unit can also adjust the PWM duty cycle or operating frequency of each equalization module 11 in real time according to the common bus current. For example, when the common bus current reaches a set threshold, the duty cycle of some equalization modules 11 can be reduced, or some equalization modules 11 can be put into a waiting state; when the common bus current recovers to the allowable range, the corresponding equalization module 11 is resumed to operate. This embodiment does not impose any limitations on this.

[0095] Furthermore, all equalization modules 11 can participate in the energy release of the common bus, or only some of them can be selected to participate. For example, when only the cell voltage corresponding to some equalization modules 11 is higher than the target state, only the corresponding equalization modules 11 are controlled to participate in the energy exchange of the common bus, while the remaining equalization modules 11 remain in standby mode. Similarly, the control can also be selected based on the state of charge, health status, or temperature information.

[0096] In summary, this embodiment utilizes a common bus to establish an energy release channel in which multiple equalization modules 11 participate, enabling multiple equalization modules 11 to release energy to the common bus of the battery pack synchronously or at different times, thereby breaking through the limitations of the traditional single-module flyback equalization method and improving the overall equalization capability of the battery pack.

[0097] This embodiment further illustrates the working method of the battery pack common bus supplementing energy to multiple equalization modules 11. The control unit controls the unit control switch, transformer primary side control switch and common bus control switch in multiple equalization modules 11, so that multiple flyback converter units can simultaneously obtain energy from the battery pack common bus and release energy to the battery cells in the corresponding equalization module 11.

[0098] like Figure 5 As shown, when the voltage of the battery cells corresponding to multiple equalization modules 11 is lower than the target state, the control unit controls multiple equalization modules 11 to enter the common bus replenishment mode.

[0099] Energy storage stage control: Q4 is turned on; Q5 is turned on; Q7 is turned on; connecting the common bus to the secondary side of the flyback transformer T1. The common bus provides energy to the secondary side of T1, enabling the transformer to complete energy storage.

[0100] Release phase control: Q4 is off; Q5 is off; Q7 remains in the corresponding state; Q2 or Q1 is turned on depending on the target battery cell. This causes the primary side of T1 to release energy to the corresponding battery cell.

[0101] When energy needs to be replenished to B1: control Q1 to turn on; control the corresponding primary-side switch to operate; When energy needs to be replenished to B2: control Q2 to turn on; control the corresponding primary-side switch to operate.

[0102] This leads to: Energy transmission path from common bus to T1 to B1 / B2.

[0103] Specifically, the control unit controls the common bus control switch in each equalization module 11 to turn on, so that the secondary sides of multiple flyback converter units are respectively connected to the common bus of the battery pack. At the same time, the control switch of the primary side of the control transformer operates according to the preset PWM signal, so that the secondary sides of multiple flyback transformers obtain energy from the common bus of the battery pack and transfer it to the primary winding through electromagnetic coupling.

[0104] Subsequently, the primary side of each flyback converter unit releases energy to the corresponding battery cell in the equalization module 11, so that multiple equalization modules 11 can simultaneously obtain supplemental energy, thereby improving the voltage or state of charge of the corresponding battery cell.

[0105] It should be noted that in this embodiment, the energy flow is from the common bus of the battery pack to each equalization module 11. Therefore, the flyback converter unit operates in the opposite energy conversion state to that in the above embodiment. However, since the same flyback converter unit is used, there is no need to add a new energy conversion device. The energy transmission direction can be changed simply by controlling the conduction state of the power switch, thus achieving bidirectional energy exchange.

[0106] Furthermore, during the simultaneous energy replenishment process of multiple equalization modules 11, the control unit can determine the energy replenishment priority of different modules based on the voltage difference between the corresponding battery cells of each equalization module 11. For example, for equalization modules 11 with lower voltage or lower state of charge, the PWM duty cycle of the corresponding flyback converter unit can be increased to obtain a larger energy replenishment current; for equalization modules 11 that are close to the target state, the duty cycle can be appropriately reduced to make the multiple equalization modules 11 gradually converge.

[0107] On the other hand, in order to further improve the energy replenishment stability, the control unit can also dynamically adjust the operating frequency of each flyback converter unit according to the change of the common bus voltage, so that the common bus is always kept within the predetermined voltage range, thereby ensuring that the energy replenishment process of multiple equalization modules 11 is stable.

[0108] Furthermore, in other embodiments, the control unit can also modify the energy replenishment strategy based on ambient temperature, battery temperature, or battery health status. For example, when the temperature of a battery cell corresponding to a certain equalization module 11 is higher than a set threshold, the energy replenishment current of the corresponding equalization module 11 can be temporarily reduced, and it can continue to participate in energy exchange after the temperature returns to normal; or the maximum energy replenishment current can be limited according to the health status of each battery cell to extend battery life. This embodiment does not impose any limitations on this.

[0109] In summary, this embodiment utilizes the battery pack's common bus as a shared energy source for multiple balancing modules 11. Multiple flyback converters synchronously establish energy transmission paths from the common bus to the balancing modules 11, enabling all balancing modules 11 to simultaneously receive supplemental energy and achieving coordinated balancing control involving multiple modules 11. In conjunction with the above embodiment, multiple balancing modules 11 can both jointly release energy to and jointly obtain energy from the battery pack's common bus, thus forming a complete bidirectional coordinated energy exchange mechanism, providing a foundation for subsequent implementations of excitation inductor reuse and control strategies.

[0110] In the above embodiments, it has been explained that the flyback converter unit can realize bidirectional energy exchange between the equalization module 11 and the common bus of the battery pack. It should be noted that whether the flyback converter unit is used for energy transfer between individual battery cells within the equalization module 11 or for energy exchange between the equalization module 11 and the common bus of the battery pack, the same flyback transformer is used to complete the energy conversion. Therefore, this embodiment further illustrates the reuse method of the flyback transformer's magnetizing inductance, where the magnetizing inductance of the flyback transformer serves as both the energy storage inductance for energy transfer between individual battery cells and the primary winding of the transformer for energy exchange between the equalization module 11 and the common bus of the battery pack.

[0111] like Figure 1 As shown, each equalization module 11 is equipped with a corresponding flyback converter unit, which includes a flyback transformer. The flyback transformer includes a primary winding, a secondary winding, and an excitation inductor formed by a magnetic core. The excitation inductor is used to store electrical energy during the primary winding's conduction period and couple the stored magnetic field energy to the secondary winding or the corresponding primary winding's release circuit during the primary winding's turn-off period, thereby realizing energy conversion.

[0112] It should be noted that the magnetizing inductor in this embodiment is not an independently set energy storage inductor, but rather an inherent excitation parameter of the flyback transformer itself. When the flyback transformer is working, the primary winding current establishes a magnetic field in the core, and the excitation flux in the core correspondingly forms the magnetizing inductor. Therefore, this embodiment does not require an additional independent energy storage inductor.

[0113] Furthermore, when energy transfer occurs between two battery cells within the balancing module 11, the control unit keeps the common bus control switch off, with only the control unit control switch and the transformer primary-side control switch operating. At this time, the magnetizing inductor stores electrical energy from the higher-voltage battery cell and releases it to the lower-voltage battery cell after energy storage is complete, thus achieving active balancing within the balancing module 11.

[0114] On the other hand, when the balancing module 11 needs to release energy to the battery pack's common bus, the control unit controls the common bus control switch to turn on, connecting the secondary side of the flyback transformer to the common bus. At this time, the magnetizing inductor still performs the energy storage function, but the stored energy is no longer released to another battery cell, but is released to the common bus through the secondary side.

[0115] Similarly, when the equalization module 11 needs to obtain energy from the battery pack's common bus, the secondary side of the flyback transformer first obtains electrical energy from the common bus, and after electromagnetic coupling, the primary side releases energy to the corresponding battery cell. In this process, the magnetizing inductor still participates in energy conversion as an energy storage element in the flyback converter process.

[0116] Therefore, in this invention, the excitation inductance in the same flyback transformer participates in the energy transfer between individual battery cells within the equalization module 11 and the energy exchange between the equalization module 11 and the common bus of the battery pack, without the need to configure different energy storage elements for different operating modes.

[0117] It should be noted that magnetizing inductor reuse does not mean that the same energy storage process is used simultaneously in different operating modes. Rather, it means that under different control modes, the magnetizing inductor in the same flyback transformer undertakes the energy storage function for the corresponding operating mode. The control unit switches the conduction relationship of the corresponding power switch according to different operating states, so that the magnetizing inductor switches between different energy transfer modes.

[0118] Furthermore, the flyback transformer can use a ferrite core, or a nanocrystalline core, amorphous alloy core, or other core materials suitable for high-frequency flyback conversion; the primary and secondary turns ratio can be designed according to the battery pack's rated voltage, balancing current, and allowable duty cycle. For example, when the output voltage of the balancing module 11 is low, the number of secondary turns can be appropriately increased; when the common bus voltage is low, the primary and secondary turns ratio can be adjusted accordingly to meet the needs of different application scenarios. This embodiment does not impose strict limitations on this.

[0119] On the other hand, the control unit can also dynamically adjust the PWM duty cycle or operating frequency according to the peak value of the excitation current, so that the excitation inductor always works within the allowable magnetic flux range, avoids the magnetic core from entering the saturation state, and improves the stability of the flyback converter unit.

[0120] In summary, this embodiment reuses the magnetizing inductor in the flyback transformer, enabling the same flyback converter unit to simultaneously handle active balancing within the balancing module 11 and bidirectional energy exchange between the balancing module 11 and the common bus of the battery pack. This eliminates the need for additional energy storage components, simplifies the overall circuit structure, and provides a unified magnetic component basis for switching between multiple operating modes.

[0121] To further improve the flexibility of collaborative operation among multiple equalization modules 11, this embodiment further describes the implementation of the control unit. The control unit includes an independent control subunit corresponding to each equalization module 11. Each control subunit independently controls the conduction state of the power switch tube in the corresponding equalization module 11 to enable parallel equalization control of multiple equalization modules 11.

[0122] The control unit includes multiple control sub-units corresponding to each equalization module 11. Each control sub-unit is connected to the switch control circuit in the corresponding equalization module 11 and controls the conduction state of each power switch in the corresponding equalization module 11.

[0123] It should be noted that the control subunit in this embodiment can be understood as a local control unit with independent data acquisition, status judgment, and power switch driving functions. Each control subunit collects the voltage, temperature, and other operating parameters of the corresponding battery cell in the equalization module 11, and independently completes the energy control of the corresponding equalization module 11 based on the acquisition results.

[0124] Furthermore, the control subunits can exchange data via CAN bus, RS485 bus, SPI communication bus, or other industrial communication methods, or they can exchange equalization status information via wireless communication. This embodiment does not impose any limitations on this.

[0125] On the other hand, in one embodiment, the control unit may further include a main controller, with each control subunit acting as a slave controller. The main controller is responsible for collecting the operating status of the entire battery pack and determining whether each equalization module 11 participates in the energy exchange of the common bus; each control subunit is responsible for executing the specific control actions within the corresponding equalization module 11.

[0126] For example, when the main controller determines that multiple equalization modules 11 need to release energy to the common bus together, the main controller sends a start command to the corresponding control subunit. Each control subunit controls the corresponding flyback converter unit to work, thereby enabling multiple equalization modules 11 to participate in energy exchange synchronously.

[0127] For example, when only one equalization module 11 needs to perform internal equalization, its corresponding control subunit can independently complete the energy transfer between battery cells without the participation of other equalization modules 11.

[0128] It should be noted that independent control does not mean that the equalization modules 11 operate completely independently, but rather that each control subunit can independently establish an energy transmission path based on the state of its corresponding equalization module 11, and can participate in the energy exchange of the common bus under the coordination of the main controller. Therefore, each equalization module 11 can work both independently and collaboratively.

[0129] Furthermore, to ensure the stability of multiple equalization modules 11 working together, each control subunit can use a unified clock source to achieve synchronous PWM output; alternatively, the main controller can broadcast a synchronization signal, and each control subunit can correct its local PWM phase according to the synchronization signal to reduce the common bus current fluctuation caused by multiple flyback converter units working simultaneously.

[0130] On the other hand, in another implementation, each control subunit can also dynamically adjust the PWM duty cycle according to the voltage deviation of the corresponding equalization module 11, so that different equalization modules 11 have different equalization currents. For example, the equalization module 11 with a larger voltage deviation can use a larger duty cycle, while the equalization module 11 with a smaller voltage deviation can use a smaller duty cycle, thereby improving the equalization efficiency of the entire battery pack.

[0131] In summary, this embodiment achieves independent and coordinated control of multiple equalization modules 11 by setting up multiple control subunits, enabling each equalization module 11 to flexibly participate in internal equalization or energy exchange on the common bus according to its own state, further improving the scalability and control flexibility of the entire lithium battery energy equalization system, and providing a hardware foundation for subsequent control method embodiments.

[0132] Based on the above hardware structure, this embodiment further provides a lithium battery energy balancing circuit control method, applied to the aforementioned lithium battery energy balancing circuit, such as... Figure 6 As shown, it includes: S101: Obtain the voltage information of each battery cell in each equalization module 11; S102: Determine whether there is a voltage difference between individual battery cells based on voltage information; S103: When a voltage difference is detected between battery cells in the same equalization module 11, the corresponding flyback converter unit is controlled to work, so that the battery cell with higher voltage can transfer energy to the battery cell with lower voltage. S104: When the voltage of a single battery cell corresponding to multiple equalization modules 11 is detected to be higher than the target state, control multiple equalization modules 11 to release energy to the common bus of the battery pack at the same time. S105: When the voltage of a single battery cell corresponding to multiple equalization modules 11 is detected to be lower than the target state, control multiple equalization modules 11 to simultaneously obtain energy from the common bus of the battery pack.

[0133] Step S101 acquires the operating information of each battery cell in each equalization module 11. Specifically, the control unit periodically collects the voltage information of each battery cell in each equalization module 11, and can further collect parameters such as current, temperature, state of charge, and health status. Among them, voltage information serves as the main basis for judging the equalization status in this embodiment, while other parameters can be used as auxiliary judgment criteria. It should be noted that voltage information can be directly obtained through a voltage sampling circuit or provided by the battery management system; this embodiment does not limit this.

[0134] S102 determines whether a voltage difference exists within the equalization module 11. The control unit calculates the voltage difference between two battery cells within the same equalization module 11 based on the collected voltage information. Let the voltages of the two battery cells be V1 and V2, respectively; then the voltage difference within the module can be expressed as: ΔV = |V1 - V2|; when ΔV is greater than the preset equalization threshold ΔVth, it is considered that there is a voltage inconsistency within the equalization module 11, and internal equalization is required. When ΔV is less than or equal to ΔVth, it is considered that the module has reached an equalization state, and no internal energy transfer path is established. It should be noted that the equalization threshold ΔVth can be set according to actual applications, such as 5mV, 10mV, or 20mV, etc., and this embodiment does not impose such limitations.

[0135] In step S103, when a voltage difference is detected within the module, the control unit compares the voltages of the two individual battery cells. If the voltage of the first battery cell is higher than that of the second battery cell, the corresponding unit control switch and the transformer primary-side control switch are turned on, while the common bus control switch remains off, allowing the flyback converter unit to establish an energy transfer path from the first battery cell to the second battery cell. If the voltage of the second battery cell is higher than that of the first battery cell, the corresponding switch on / off relationship is adjusted, allowing the flyback converter unit to establish an energy transfer path from the second battery cell to the first battery cell. Throughout this process, the common bus does not participate in energy exchange; therefore, the multiple equalization modules 11 do not affect each other, and each equalization module 11 can independently complete its internal equalization.

[0136] The system determines whether module-wide balancing is required. After completing the balancing judgment within each module, the control unit further analyzes the overall state among the multiple balancing modules 11. For example, it can calculate the average voltage of each balancing module 11: Vm(i); then calculate the average voltage of the entire battery pack: Vavg; if the average voltages corresponding to multiple balancing modules 11 are all higher than the target state, the system enters the common bus energy release mode. If the average voltages corresponding to multiple balancing modules 11 are all lower than the target state, the system enters the common bus energy replenishment mode.

[0137] On the other hand, the State of Charge (SOC) can also be used as a criterion. Values ​​below the lower limit of charge or above the upper limit of charge can be used as conditions for entering the common bus cooperative equilibrium.

[0138] Through the above steps, the control method can first complete the internal balance judgment of the module, and then complete the collaborative balance judgment between multiple balance modules 11, thereby combining the internal balance of the module with the collaborative balance between modules and improving the flexibility of the overall battery pack balance control.

[0139] Specifically, when the voltage or state of charge of the battery cells corresponding to multiple equalization modules 11 is detected to be higher than the target state, the multiple equalization modules 11 are controlled to work synchronously, so that the multiple equalization modules 11 simultaneously output energy to the common bus of the battery pack through the corresponding flyback converter unit. When the voltage or state of charge of a battery cell corresponding to multiple equalization modules 11 is detected to be lower than the target state, the multiple equalization modules 11 are controlled to work synchronously, so that the multiple equalization modules 11 can simultaneously obtain energy from the common bus of the battery pack through the corresponding flyback converter unit.

[0140] Specifically, the control unit sends a synchronization control command to the corresponding control subunit, and each control subunit controls the unit control switch, transformer primary control switch and common bus control switch in the corresponding equalization module 11 to be turned on according to the synchronization control command.

[0141] Multiple flyback converters obtain energy from their respective battery cells on their primary sides and establish excitation currents. After the predetermined energy storage time is reached, the secondary sides of each flyback converter release energy to the common bus of the battery pack.

[0142] It should be noted that synchronous operation does not mean that multiple flyback converter units must be turned on at exactly the same time. In this embodiment, synchronous operation means that multiple equalization modules 11 participate in the energy exchange of the common bus within the same control cycle. Depending on the control strategy, either synchronous PWM or interleaved PWM can be used.

[0143] On the other hand, when the control unit determines that the voltage or state of charge of the battery cells corresponding to the multiple equalization modules 11 is lower than the target state, an energy transmission path from the common bus to the equalization module 11 is established.

[0144] The control unit controls multiple common bus control switches to turn on, so that the secondary sides of multiple flyback converter units are simultaneously connected to the common bus. Each flyback converter unit obtains energy from the common bus and releases it to the corresponding battery cell in the equalization module 11 through the primary side.

[0145] Furthermore, to avoid the problem that some modules replenish energy too quickly while others do not replenish energy enough during the replenishment process of multiple equalization modules 11, the control unit can dynamically adjust the PWM duty cycle according to the voltage deviation of each equalization module 11.

[0146] In addition, the control unit can monitor the common bus voltage in real time. When the common bus voltage is higher than the preset upper limit, the output power of part of the equalization module 11 is reduced; when the common bus voltage is lower than the preset lower limit, the supplementary power of part of the equalization module 11 is increased, thereby maintaining the stability of the common bus voltage.

[0147] In summary, this embodiment coordinates the working states of multiple equalization modules 11, enabling them to synchronously release energy to or obtain energy from the battery pack's common bus according to overall equalization requirements. This combines internal equalization with inter-module collaborative equalization. Compared to traditional flyback equalization circuits, this invention utilizes the common bus to establish a collaborative energy exchange mechanism among multiple equalization modules 11 and combines it with a flyback converter unit to achieve bidirectional energy transmission. This improves the ability of multiple equalization modules 11 to participate in overall equalization while also considering modular expansion requirements, making it suitable for active equalization control of large-scale series lithium battery packs.

[0148] The lithium battery energy balancing circuit and control method provided in this application have been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0149] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, 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 the element.

Claims

1. A lithium battery energy balancing circuit, characterized in that, include: Multiple equalization modules, a common bus for the battery pack connected to the multiple equalization modules, and a control unit; Each equalization module includes two battery cells connected in series, a switch control circuit, and a flyback converter unit connected to the battery cells. The switching control circuit includes multiple power switching transistors. The control unit is connected to the power switching transistors and controls the conduction state of different power switching transistors, so that the equalization circuit forms energy transmission paths between battery cells, energy transmission paths from the equalization module to the common bus of the battery pack, and energy transmission paths from the common bus of the battery pack to the equalization module. The flyback converter unit includes a flyback transformer, which is connected between the individual battery cell and the common bus of the battery pack to realize bidirectional energy transfer between individual battery cells within the equalization module, as well as bidirectional energy exchange between the equalization module and the common bus of the battery pack. The multiple equalization modules are respectively connected to the common bus of the battery pack, and the control unit controls the multiple equalization modules to simultaneously release energy to the common bus of the battery pack, or simultaneously obtain energy from the common bus of the battery pack.

2. The lithium battery energy balancing circuit according to claim 1, characterized in that, The power switch is a power switch with an anti-parallel diode; In the off state, the power switch forms a unidirectional conduction path through the anti-parallel diode, and in the on state, it forms a low-impedance energy transmission path.

3. The lithium battery energy balancing circuit according to claim 1, characterized in that, The power switching transistors include: a unit control switch, a transformer primary-side control switch, and a common bus control switch; The unit control switch is used to control the connection between the battery cell and the flyback transformer, so as to realize the energy transfer between the battery cells inside the equalization module. The transformer primary control switch is used to control the on / off of the primary current of the flyback transformer, so as to control the flyback converter unit to perform energy conversion. The common bus control switch is used to control the connection status between the secondary side of the flyback transformer and the common bus of the battery pack, so as to realize the energy exchange between the equalization module and the common bus of the battery pack.

4. The lithium battery energy balancing circuit according to claim 3, characterized in that, The control unit controls the unit control switch, the transformer primary control switch, and the common bus control switch to form a bidirectional energy transfer path between battery cells within the equalization module, so as to transfer energy from battery cells with higher voltage to battery cells with lower voltage.

5. The lithium battery energy balancing circuit according to claim 3, characterized in that, The control unit controls the unit control switches, transformer primary control switches, and common bus control switches in multiple equalization modules, so that the primary sides of the multiple flyback converter units respectively obtain energy from the battery cells of the corresponding equalization modules, and simultaneously release energy to the common bus of the battery pack through the secondary sides.

6. The lithium battery energy balancing circuit according to claim 3, characterized in that, The control unit controls the unit control switches, transformer primary-side control switches, and common bus control switches in multiple equalization modules, enabling multiple flyback converter units to simultaneously obtain energy from the battery pack common bus and release energy to the battery cells in the corresponding equalization modules.

7. The lithium battery energy balancing circuit according to claim 1, characterized in that, The excitation inductance of the flyback transformer serves as both the energy storage inductance for energy transfer between the individual battery cells and the primary winding of the transformer for energy exchange between the equalization module and the common bus of the battery pack.

8. The lithium battery energy balancing circuit according to claim 1, characterized in that, The control unit includes independent control subunits corresponding to each equalization module. Each control subunit independently controls the conduction state of the power switch in the corresponding equalization module to enable parallel equalization control of multiple equalization modules.

9. A lithium battery energy balancing circuit control method, applied to the lithium battery energy balancing circuit according to any one of claims 1 to 8, characterized in that, include: Obtain the voltage information of individual battery cells within each equalization module; Determine whether there is a voltage difference between the individual battery cells based on the voltage information; When a voltage difference is detected between battery cells within the same equalization module, the corresponding flyback converter unit is controlled to operate, so that the battery cell with higher voltage can transfer energy to the battery cell with lower voltage. When the voltage of a single battery cell corresponding to multiple equalization modules is detected to be higher than the target state, the multiple equalization modules are controlled to release energy to the common bus of the battery pack simultaneously. When it is detected that the voltage of a single battery cell corresponding to multiple equalization modules is lower than the target state, the multiple equalization modules are controlled to simultaneously obtain energy from the common bus of the battery pack.

10. The lithium battery energy balancing circuit control method according to claim 9, characterized in that, When the voltage or state of charge of a single battery cell corresponding to multiple equalization modules is detected to be higher than the target state, the multiple equalization modules are controlled to work synchronously, so that the multiple equalization modules simultaneously output energy to the common bus of the battery pack through the corresponding flyback converter unit. When the voltage or state of charge of a battery cell corresponding to multiple equalization modules is detected to be lower than the target state, the multiple equalization modules are controlled to work synchronously, so that the multiple equalization modules can simultaneously obtain energy from the common bus of the battery pack through the corresponding flyback converter unit.

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