Unmanned aerial vehicle battery active equalization circuit and method suitable for high-rate discharge

Abstract

The invention discloses an unmanned aerial vehicle battery active equalization circuit and method suitable for high-rate discharge, and belongs to the technical field of lithium battery management systems. The circuit comprises a common energy storage bus, a controller and a plurality of modularized bidirectional DC-DC equalization units. Each equalization unit comprises a transformer, a blocking capacitor, a main switch tube and a secondary switch tube, the primary winding is connected with the main switch tube through the blocking capacitor, and the secondary winding is directly connected with the public energy storage bus and the secondary switch tube. The method comprises the following steps: entering a dynamic equalization mode when high-rate discharge is monitored; calculating the voltage drop rate of each battery cell in real time, and identifying a target battery cell and a source battery cell; and through time division multiplexing control, energy is transferred from the source battery cell to the target battery cell through the public energy storage bus. According to the invention, predictive identification and rapid large-current supplement of the short-plate battery cell are realized, and the available capacity of the battery pack under high-rate discharge and the endurance of the unmanned aerial vehicle are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery management system technology, specifically to an active balancing circuit and method for drone batteries suitable for high-rate discharge. Background Technology

[0002] Lithium-ion batteries are widely used in drones due to their high energy density. To meet voltage and power requirements, drone battery packs typically consist of multiple cells connected in series. However, due to differences in manufacturing processes, operating temperatures, and initial capacity, the state of charge (SOC) between cells can become inconsistent after use.

[0003] This problem is particularly prominent when drones discharge at high rates (such as during takeoff and climb, when the current often reaches 10C to 50C). Cells with slightly higher internal resistance or lower charge will have their terminal voltage drop to the discharge cutoff voltage faster than other cells, triggering the undervoltage protection of the battery protection board. This forces the entire battery pack to stop working despite having residual charge, significantly shortening the drone's effective flight time.

[0004] Current common equalization techniques have significant shortcomings: 1. Passive balancing (dissipative balancing): At the end of charging, excess energy from higher-voltage cells is dissipated as heat through resistors. This method is completely ineffective during the discharge process, has a small balancing current (typically <100mA), low efficiency, and causes heat generation.

[0005] 2. Traditional active balancing: such as capacitor switch array method, has a slow balancing speed and low energy transfer efficiency for non-adjacent cells; while traditional inductor or transformer balancing has a rigid control strategy, usually based on static voltage difference threshold to start, with slow response and limited balancing current (usually <2A), making it difficult to quickly respond to the global "short-board" cell demand in high-rate discharge scenarios.

[0006] Therefore, existing technologies cannot meet the stringent requirements of drones for balanced speed, balanced current, and intelligent decision-making during high-rate dynamic discharge. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an active balancing circuit and method for drone batteries suitable for high-rate discharge, enabling predictive identification of "weak" cells and rapid, high-current energy replenishment, thereby improving the usable capacity of the battery pack under high-rate discharge and the drone's endurance. To achieve the above objective, the technical solution adopted by this invention is as follows: An active balancing circuit for drone batteries suitable for high-rate discharge includes: A common energy storage bus; Multiple modular equalization units, the number of which corresponds to the number of cells in the battery pack, with each modular equalization unit connected between the corresponding cell and the common energy storage bus; A controller with signal input connected to the battery pack and individual cells to collect voltage and current signals, and its control output connected to each modular equalization unit; When the battery pack is discharged at a high rate, the controller dynamically identifies the target cell and the source cell based on the voltage drop rate of each cell, and controls the corresponding modular equalization unit to transfer energy from the source cell to the target cell through the common energy storage bus.

[0008] Furthermore, each modular equalization unit is a bidirectional DC-DC equalization unit.

[0009] The bidirectional DC-DC equalization unit includes: A transformer consists of a primary winding and a secondary winding; The first end of the primary winding is connected to the positive terminal of the corresponding battery cell, and the second end is connected to the drain of a main switching transistor through a DC blocking capacitor. The source of the main switch is connected to the reference ground, and the gate receives the first PWM signal from the controller. The first end of the secondary winding is connected to a common energy storage bus via a common node, and the second end is connected to the drain of a secondary switching transistor. The source of the secondary-side switch is connected to the reference ground, and its gate receives a second PWM signal from the controller.

[0010] Furthermore, the controller applies the second PWM signal to the gate of the secondary-side switch corresponding to the source cell, while simultaneously invalidating the first PWM signal to turn off the corresponding main switch, thus transferring energy from the current source cell to the common energy storage bus. The controller applies the first PWM signal to the gate of the main switch corresponding to the target cell, and at the same time invalidates the second PWM signal to turn off the corresponding secondary switch, injecting energy into the current target cell from the common energy storage bus.

[0011] Furthermore, both the main switch and the secondary switch are N-MOSFETs.

[0012] Furthermore, the primary and secondary windings of the transformers of multiple bidirectional DC-DC equalization units are wound on the same magnetic core.

[0013] A method for an active balancing circuit for drone batteries suitable for high-rate discharge includes the following steps: S1. Monitor the battery pack's discharge current. When the discharge current exceeds a preset threshold, switch from sleep mode or static balancing mode to dynamic balancing mode. S2. In dynamic equalization mode, the voltage of all cells in the battery pack is sampled in real time and the voltage drop rate of each cell is calculated. S3. Based on the voltage drop rate, identify the target cell and the source cell from multiple cells; S4. Energy is transferred from the source cell to the target cell through a common energy storage bus and multiple modular equalization units.

[0014] Furthermore, in S4, through time-division multiplexing control, the modular equalization unit corresponding to the source cell is first controlled to transfer the energy of the source cell to the common energy storage bus, and then the modular equalization unit corresponding to the target cell is controlled to transfer the energy in the common energy storage bus to the target cell.

[0015] Further, S3 includes: S31. Identifying the cell with the largest voltage drop rate as the target cell; S32. Selecting the cell with the highest absolute voltage value and / or the smallest voltage drop rate from the remaining cells as the source cell.

[0016] Furthermore, it also includes: continuously monitoring the voltage drop rate of all cells during the energy transfer from the common energy storage bus to the target cell; when the voltage drop rate of the target cell decreases to less than the first recovery threshold, stopping the energy transfer and exiting the dynamic balancing mode.

[0017] Furthermore, it also includes: during the process of transferring energy from the common energy storage bus to the target cell, continuously calculating the voltage drop rate of all cells; if the voltage drop rate of a second cell exceeds the voltage drop rate of the target cell, immediately stopping the energy transfer to the target cell, identifying the second cell as the new target cell, and then transferring energy from the source cell to the new target cell; if the voltage drop rate of multiple cells exceeds the voltage drop rate of the target cell, immediately stopping the energy transfer to the target cell, reselecting the cell with the largest voltage drop rate from all cells as the new target cell, and then transferring energy from the source cell to the new target cell.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention overcomes the industry-wide challenge of premature battery pack shutdown due to the rapid degradation of weaker cells during high-rate discharge. Through dynamic prediction based on voltage drop rate and the synergistic effect of many-to-one centralized energy dispatch via a shared energy storage bus, the system can identify the most critical cells tens to hundreds of milliseconds in advance and proactively replenish them with a high-current supply of several amperes, directly raising their voltage curve and preventing them from reaching the protection threshold. This increases the usable capacity of the battery pack under high-rate discharge by 10%-20%, directly extending the flight time of the drone.

[0019] 2. During high-rate discharge, the voltage of all cells drops sharply due to internal resistance voltage drop, making it difficult to identify the most critical cells using traditional static voltage difference comparison. This invention introduces the voltage drop rate as a dynamic criterion to replace the traditional static voltage difference comparison, better reflecting the real-time performance status of cells under high current. This allows the system to initiate balancing tens to hundreds of milliseconds before severe voltage differentiation, achieving a shift from delayed remediation to predictive intervention with a response speed in the millisecond range.

[0020] 3. This invention, through a modular bidirectional converter + common energy storage bus architecture, breaks through the power bottleneck of traditional one-to-one or fixed-path balancing. It supports the scheduling of energy flowing from any source cell into the bus and then centrally supplying the target cell, and can achieve power superposition of multiple modules, stably providing a large balancing current of over 3A, sufficient to withstand the impact of discharge currents in the tens of amperes. Simultaneously, this invention utilizes energy transfer based on efficient DC-DC conversion, achieving an overall efficiency of over 85%, avoiding energy waste and thermal management pressure, reducing the thermal management burden on the battery pack, and improving system reliability and safety. Attached Figure Description

[0021] Figure 1 This is the overall block diagram of the circuit of the present invention.

[0022] Figure 2 This is a circuit schematic diagram of a single bidirectional DC-DC equalization unit (taking M1 as an example) of the present invention.

[0023] Figure 3 This is a control flowchart of the method of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. In the description of this invention, it should be noted that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] like Figure 1 As shown, the circuit of this invention includes a controller (MCU), a common energy storage bus (C_BUS), and N modular bidirectional DC-DC equalization units (M1 to MN). Each equalization unit is connected to a corresponding cell (B1 to BN) in a drone battery pack. The controller (MCU) is preferably an STM32GD32E230 model.

[0026] like Figure 2As shown, the specific structure and operation of the modular bidirectional DC-DC equalization unit (taking unit M1 connected to cell B1 as an example) are as follows: The modular bidirectional DC-DC equalization unit M1 includes a transformer T1, a DC blocking capacitor C1, a main switch Q1, a secondary switch Q2, and corresponding control signal interfaces.

[0027] Transformer T1 consists of a primary winding LP1 and a secondary winding L1S.

[0028] The first end of the primary winding LP1 is directly connected to the positive terminal (B1+) of the cell B1, and the second end is connected to the drain of the main switch Q1 through the DC blocking capacitor C1.

[0029] The source of the main switch Q1 is connected to the reference ground (GND), and its gate receives the first PWM control signal (PWM_CH1) from the controller (MCU).

[0030] The first end of the secondary winding L1S is directly connected to the common energy storage bus (C_BUS), and the second end is connected to the drain of the secondary-side switch Q2.

[0031] The source of the secondary-side switch Q2 is connected to the reference ground (GND), and its gate receives the second PWM control signal (PWM_CH2) from the controller (MCU).

[0032] The following is the workflow for transferring energy from cell B1 to the common energy storage bus C_BUS (with B1 as the source cell): The controller (MCU) outputs a high-frequency second PWM signal (PWM_CH2) to the gate of the secondary switch (Q2), while keeping the gate signal (PWM_CH1) of the main switch (Q1) in an invalid state. When the secondary switch (Q2) is turned on (the main switch (Q1) is turned off), current flows through the primary winding LP1 and the DC blocking capacitor C1, converting electrical energy into magnetic energy stored in the transformer T1; when the secondary switch (Q2) is turned off, the magnetic field energy is released through the secondary winding L1S to charge the common energy storage bus (C_BUS), thereby realizing the transfer of energy from the battery cell to the bus.

[0033] The following is the workflow for transferring energy from the common energy storage bus C_BUS to cell B1 (B1 being the target cell): The controller (MCU) outputs a high-frequency first PWM signal (PWM_CH1) to the gate of the main switch (Q1), while keeping the gate signal (PWM_CH2) of the secondary switch (Q2) in an inactive state. When the main switch (Q1) is turned on (the secondary switch (Q2) is turned off), the voltage of the common energy storage bus (C_BUS) is applied to the secondary winding L1S, and the energy is stored again in the transformer magnetic field T1. When the main switch (Q1) is turned off, the magnetic field energy is released through the primary winding LP1 and the DC blocking capacitor C1 to charge the battery cell B1, thereby realizing the transfer of energy from the bus to the battery cell.

[0034] like Figure 3 As shown, the closed-loop control flow of the method of the present invention is as follows: System initialization (S0): The system is powered on and monitoring begins.

[0035] Current judgment (S1): Continuously monitor the discharge current of the battery pack. If the discharge current exceeds the preset threshold (e.g., 5C), proceed to the next step; otherwise, continue monitoring.

[0036] Dynamic monitoring mode (S2): Enter dynamic equalization mode, sample the voltage of all cells in the battery pack in real time and calculate the voltage drop rate (dV / dt) of each cell. Dynamic identification (S3): Identify the cell with the largest voltage drop rate (dV / dt) as the target cell, and at the same time identify the cell with the highest absolute voltage value and the smallest voltage drop rate (dV / dt) as the source cell.

[0037] Energy Dispatch (S4): Through time-division multiplexing control, the source cell is first controlled to transfer energy to the common energy storage bus, and then the modular equalization unit corresponding to the target cell is controlled to transfer the energy in the common energy storage bus to the target cell, that is, the target cell unit obtains energy from the common energy storage bus.

[0038] Adaptive Feedback (S5): During the energy transfer to the target cell in the common energy storage bus (charging the target cell), the voltage drop rate of all cells is continuously monitored; when the voltage drop rate of the target cell decreases to less than the first recovery threshold, energy transfer is stopped (charging to the target cell ends) and the dynamic equalization mode is exited; if the voltage drop rate of a second cell exceeds the voltage drop rate of the target cell, energy transfer to the target cell is immediately stopped, the second cell is identified as the new target cell, and then energy is transferred from the source cell to the new target cell; if the voltage drop rate of multiple cells exceeds the voltage drop rate of the target cell, energy transfer to the target cell is immediately stopped, and the cell with the largest voltage drop rate is reselected from all cells as the new target cell, and then energy is transferred from the source cell to the new target cell.

[0039] In a preferred embodiment of the present invention, the step of calculating the voltage drop rate (dV / dt) in real time includes: The voltage values ​​of all battery cells are acquired synchronously at a sampling frequency higher than 1kHz; Based on multiple voltage samples of each cell within the most recent preset time window, the voltage drop rate is calculated using either the differential method or a linear regression algorithm based on a sliding window.

[0040] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. An active balancing circuit for UAV batteries suitable for high-rate discharge, characterized in that, include: A common energy storage bus; Multiple modular equalization units, the number of which corresponds to the number of cells in the battery pack, with each modular equalization unit connected between the corresponding cell and the common energy storage bus; A controller with signal input connected to the battery pack and individual cells to collect voltage and current signals, and its control output connected to each modular equalization unit; When the battery pack is discharged at a high rate, the controller dynamically identifies the target cell and the source cell based on the voltage drop rate of each cell, and controls the corresponding modular equalization unit to transfer energy from the source cell to the target cell through the common energy storage bus.

2. The active balancing circuit for UAV batteries suitable for high-rate discharge as described in claim 1, characterized in that, Each modular equalization unit is a bidirectional DC-DC equalization unit; The bidirectional DC-DC equalization unit includes: A transformer consists of a primary winding and a secondary winding; The first end of the primary winding is connected to the positive terminal of the corresponding battery cell, and the second end is connected to the drain of a main switching transistor through a DC blocking capacitor. The source of the main switch is connected to the reference ground, and the gate receives the first PWM signal from the controller. The first end of the secondary winding is connected to a common energy storage bus via a common node, and the second end is connected to the drain of a secondary switching transistor. The source of the secondary-side switch is connected to the reference ground, and its gate receives a second PWM signal from the controller.

3. The active balancing circuit for UAV batteries suitable for high-rate discharge as described in claim 2, characterized in that, The controller applies the second PWM signal to the gate of the secondary-side switch corresponding to the source cell, while simultaneously invalidating the first PWM signal to turn off the corresponding main switch, thus transferring energy from the current source cell to the common energy storage bus. The controller applies the first PWM signal to the gate of the main switch corresponding to the target cell, and at the same time invalidates the second PWM signal to turn off the corresponding secondary switch, injecting energy into the current target cell from the common energy storage bus.

4. The active balancing circuit for UAV batteries suitable for high-rate discharge as described in claim 2, characterized in that, Both the main switch and the secondary switch are N-MOSFETs.

5. The active balancing circuit for UAV batteries suitable for high-rate discharge as described in claim 2, characterized in that, The primary and secondary windings of the transformers of multiple bidirectional DC-DC equalization units are wound on the same magnetic core.

6. A method for an active balancing circuit for a drone battery suitable for high-rate discharge, as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Monitor the battery pack's discharge current. When the discharge current exceeds a preset threshold, switch from sleep mode or static balancing mode to dynamic balancing mode. S2. In dynamic equalization mode, the voltage of all cells in the battery pack is sampled in real time and the voltage drop rate of each cell is calculated. S3. Based on the voltage drop rate, identify the target cell and the source cell from multiple cells; S4. Energy is transferred from the source cell to the target cell through a common energy storage bus and multiple modular equalization units.

7. The method for an active balancing circuit for a drone battery suitable for high-rate discharge, as described in claim 6, is characterized in that... In S4, the modular equalization unit corresponding to the source cell is first controlled through time-division multiplexing control to transfer the energy of the source cell to the common energy storage bus, and then the modular equalization unit corresponding to the target cell is controlled to transfer the energy in the common energy storage bus to the target cell.

8. The method for an active balancing circuit for a drone battery suitable for high-rate discharge, as described in claim 6, is characterized in that... S3 This includes: S31. Identifying the cell with the largest voltage drop rate as the target cell; S32. Selecting the cell with the highest absolute voltage value and / or the smallest voltage drop rate from the remaining cells as the source cell.

9. A method for an active balancing circuit for a drone battery suitable for high-rate discharge, as described in claim 8, characterized in that, Also includes: During the energy transfer from the common energy storage bus to the target cell, the voltage drop rate of all cells is continuously monitored; when the voltage drop rate of the target cell decreases to less than the first recovery threshold, energy transfer is stopped and the dynamic balancing mode is exited.

10. A method for an active balancing circuit for a drone battery suitable for high-rate discharge, as described in claim 8, characterized in that, Also includes: During the process of transferring energy from the common energy storage bus to the target cell, the voltage drop rate of all cells is continuously calculated; If the voltage drop rate of a second cell exceeds that of the target cell, the energy transfer to the target cell is immediately stopped, the second cell is identified as the new target cell, and the energy is then transferred from the source cell to the new target cell. If the voltage drop rate of multiple cells exceeds that of the target cell, the energy transfer to the target cell is immediately stopped, and the cell with the largest voltage drop rate is selected from all the cells as the new target cell. The energy is then transferred from the source cell to the new target cell.

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