A BMS low-side current-limiting buck duty cycle dynamic expansion control method and system

Abstract

This application proposes a method and system for dynamic expansion control of Buck duty cycle in low-side current limiting of a battery management system (BMS), relating to the field of battery management system control technology. The method includes: when the battery management system calculates that the required duty cycle of the Buck converter exceeds a preset limit, obtaining the operating parameters of the Buck converter; obtaining a predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter; dynamically adjusting the maximum duty cycle limit of the Buck converter based on the predicted value of the bootstrap capacitor voltage; allowing the maximum duty cycle limit to expand when the predicted value of the bootstrap capacitor voltage is higher than a preset expansion threshold to maintain the charging current; and activating a duty cycle callback mechanism when the predicted value of the bootstrap capacitor voltage is lower than a preset callback threshold to avoid excessively short discharge time of the bootstrap capacitor. This application can improve the efficiency and stability of the charging system and enhance the system's safety.

Description

Technical Field

[0001] This application relates to the field of battery management system control technology, and in particular to a method and system for dynamic expansion control of the Buck duty cycle of a low-side current limiting BMS. Background Technology

[0002] In related technologies, DC-DC converters, especially Buck converters, play a crucial role in the design and application of Battery Management Systems (BMS), responsible for adjusting the input power supply voltage to a level suitable for charging the battery pack or supplying power to the load. To ensure the efficiency, stability, and safety of the charging process, BMS typically employs precise control methods, such as low-side current-limiting Buck duty cycle dynamic extension control. The core of this method lies in precisely controlling the output current by adjusting the on-time ratio (i.e., duty cycle) of the power switches in the Buck converter. However, in practical applications, especially in high-voltage, high-power scenarios, the drive circuit of the low-side power switches in the Buck converter often relies on bootstrap capacitors to provide a stable drive voltage. This requires that sufficient charging and discharging time be reserved for the bootstrap capacitors in each switching cycle, usually achieved by limiting the maximum duty cycle. If the duty cycle is too high and the off-time too short, the bootstrap capacitors may not discharge sufficiently, causing the low-side switches to fail to fully conduct, resulting in no current at the end of battery charging. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a BMS low-side current limiting Buck duty cycle dynamic expansion control method and system, aiming to improve the efficiency and stability of the charging system and enhance its safety.

[0004] In a first aspect, embodiments of this application provide a method for dynamically expanding the Buck duty cycle of a BMS low-side current limiting system, including: When the battery management system calculates that the duty cycle required by the Buck converter exceeds the preset limit, it obtains the operating parameters of the Buck converter. Based on the operating parameters of the Buck converter, the predicted value of the bootstrap capacitor voltage is obtained; The maximum duty cycle limit of the Buck converter is dynamically adjusted based on the predicted value of the bootstrap capacitor voltage. When the predicted value of the bootstrap capacitor voltage is higher than the preset extension threshold, the maximum duty cycle limit is allowed to extend in order to maintain the charging current; When the predicted value of the bootstrap capacitor voltage is lower than the preset callback threshold, the duty cycle callback mechanism is activated to avoid the bootstrap capacitor discharge time being too short.

[0005] According to some embodiments of this application, the step of obtaining the predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter includes: When the Buck converter is operating in the non-limited duty cycle extended range and the input voltage is stable, monitor the bootstrap capacitor charging parameters. The voltage change and charging time of the bootstrap capacitor during the monitoring period are obtained based on the bootstrap capacitor charging parameters. Based on the voltage change and charging time of the bootstrap capacitor during the monitoring period, the actual average charging current of the bootstrap capacitor is estimated. The charging efficiency correction factor is calculated based on the actual average charging current and the average charging current parameters used in the prediction program. Based on the charging efficiency correction factor, the average charging current parameter used in the prediction program is updated, and the bootstrap capacitor voltage prediction value is obtained based on the operating parameters of the Buck converter.

[0006] According to some embodiments of this application, after the step of allowing the maximum duty cycle limit to extend to maintain the charging current when the predicted value of the bootstrap capacitor voltage is higher than a preset extension threshold, the method further includes: When the predicted value of the bootstrap capacitor voltage approaches the preset callback threshold... Based on the operating parameters of the Buck converter, predict the voltage value of the bootstrap capacitor after a preset number of cycles; Calculate the bootstrap capacitor voltage drop rate based on the operating parameters of the Buck converter; Based on the voltage value of the bootstrap capacitor after a preset number of cycles and the rate of voltage drop of the bootstrap capacitor, the response speed of the duty cycle callback mechanism is adjusted to dynamically adjust the maximum duty cycle limit of the Buck converter.

[0007] According to some embodiments of this application, after the step of allowing the maximum duty cycle limit to extend to maintain the charging current when the predicted value of the bootstrap capacitor voltage is higher than a preset extension threshold, the method further includes: Monitor the temperature of key components of the Buck converter; Based on the operating parameters of the Buck converter, estimate the junction temperature rise trend of the low-side power switch. When the temperature of a critical component of the Buck converter or the junction temperature rises above a preset threshold, the maximum duty cycle limit is reduced to restore the temperature of the critical component of the Buck converter to a safe range.

[0008] According to some embodiments of this application, when the predicted value of the bootstrap capacitor voltage is lower than a preset callback threshold, the step of activating a duty cycle callback mechanism to avoid excessively short bootstrap capacitor discharge time includes: Obtain the actual voltage drop rate of the bootstrap capacitor; Based on the deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold, and the actual voltage drop rate of the bootstrap capacitor, the duty cycle callback mechanism is activated to adjust the step size or callback period of the duty cycle callback in order to avoid undervoltage of the bootstrap capacitor.

[0009] According to some embodiments of this application, the step of activating a duty cycle callback mechanism based on the deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold, and the actual voltage drop rate of the bootstrap capacitor, and adjusting the step size or callback period of the duty cycle callback to avoid undervoltage of the bootstrap capacitor includes: The actual voltage drop rate of the bootstrap capacitor is subjected to multi-cycle moving average filtering. The deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold is subjected to multi-period moving average filtering. Based on the actual voltage drop rate after filtering and the predicted deviation after filtering, the duty cycle callback mechanism is activated to adjust the step size or callback period of the duty cycle callback in order to avoid undervoltage of the bootstrap capacitor.

[0010] According to some embodiments of this application, the step of activating the duty cycle callback mechanism based on the filtered actual voltage drop rate and the filtered prediction deviation, and adjusting the step size or callback period of the duty cycle callback to avoid undervoltage of the bootstrap capacitor, further includes: When the Buck converter is operating in the non-limiting duty cycle extended range and the input voltage is stable, the actual capacitance of the bootstrap capacitor is periodically calibrated. The calibration includes: During the conduction of the low-side switch, the voltage across the bootstrap capacitor is monitored to obtain the voltage change and charging time of the bootstrap capacitor. Calculate the actual charge amount of the bootstrap capacitor based on the voltage change of the bootstrap capacitor, the charging time, and the known charging current. The actual capacity of the bootstrap capacitor is estimated by using the actual amount of charging charge and the voltage change of the bootstrap capacitor. The actual capacity is compared with the bootstrap capacitor capacity parameter used in the prediction program, and the capacity correction factor is calculated. Update the bootstrap capacitor capacity parameter used in the prediction program according to the capacity correction factor; When adjusting the step size or callback period of the duty cycle callback, the updated bootstrap capacitor capacity parameter is applied to the calculation of the bootstrap voltage margin prediction module to correct the filtered actual voltage drop rate and the filtered prediction deviation, thereby adjusting the step size or callback period of the duty cycle callback.

[0011] According to some embodiments of this application, the step following the periodic calibration of the actual capacitance of the bootstrap capacitor when the Buck converter is operating in the non-limited duty cycle extended range and the input voltage is stable includes: Get the current ambient temperature and the output power of the Buck converter; Based on the ambient temperature and the output power, and combined with the preset aging rate curve, the current aging rate of the bootstrap capacitor is estimated. The cycle for calibrating the actual capacity of the bootstrap capacitor is dynamically adjusted based on the bootstrap capacitor aging rate. When the cumulative value of the bootstrap capacitor voltage prediction deviation exceeds a preset threshold, the actual capacity calibration of the bootstrap capacitor is triggered.

[0012] According to some embodiments of this application, the step of monitoring the voltage across the bootstrap capacitor and obtaining the voltage change and charging time of the bootstrap capacitor during the conduction period of the low-side switch includes: During the conduction of the low-side switch, the voltage data across the bootstrap capacitor is collected; The voltage data across the bootstrap capacitor is subjected to digital low-pass filtering to remove high-frequency noise; Identify the start and end times of the low-side switch's conduction and obtain the actual conduction time; Obtain the filtered voltage values ​​at the start time and the end time; Based on the filtered voltage value and the actual conduction time, the voltage change and charging time of the bootstrap capacitor under conditions free from high-frequency noise interference are obtained.

[0013] Secondly, embodiments of this application provide a BMS low-side current limiting Buck duty cycle dynamic expansion control system, comprising: The acquisition module is used to acquire the operating parameters of the Buck converter when the battery management system calculates that the required duty cycle of the Buck converter exceeds the preset limit. The prediction module is used to obtain the predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter. The adjustment module is used to dynamically adjust the maximum duty cycle limit of the Buck converter based on the predicted value of the bootstrap capacitor voltage. When the predicted value of the bootstrap capacitor voltage is higher than a preset extension threshold, the maximum duty cycle limit is allowed to extend to maintain the charging current. When the predicted value of the bootstrap capacitor voltage is lower than a preset callback threshold, the duty cycle callback mechanism is activated to avoid the bootstrap capacitor discharge time being too short.

[0014] The technical solution according to the embodiments of this application has at least the following beneficial effects: This application discloses a BMS low-side current limiting Buck duty cycle dynamic expansion control method. By obtaining the operating parameters of the Buck converter when the required duty cycle of the Buck converter exceeds a preset limit calculated by the battery management system, and obtaining the predicted value of the bootstrap capacitor voltage based on these parameters, this application can dynamically adjust the maximum duty cycle limit of the Buck converter based on this predicted value. Specifically, when the predicted value of the bootstrap capacitor voltage is higher than a preset expansion threshold, the system allows the maximum duty cycle limit to expand to maintain the charging current, thereby effectively solving the problem of a significant drop in charging current due to duty cycle clamping in the prior art. Simultaneously, when the predicted value of the bootstrap capacitor voltage is lower than a preset callback threshold, the system will activate a duty cycle callback mechanism to avoid undervoltage of the bootstrap capacitor, thereby overcoming the risk of damage to the low-side switch due to insufficient charging of the bootstrap capacitor in the prior art. This application intelligently balances the maintenance of charging current with the protection of the bootstrap capacitor, avoiding charging power fluctuations caused by excessively strict duty cycle restrictions in traditional control methods under extreme conditions such as sudden input voltage drops, as well as overheating damage to the switching transistor caused by blindly relaxing the duty cycle restriction. This method not only improves the efficiency and stability of the charging system but also significantly enhances system safety, extends the service life of key components, and provides a more reliable and flexible control strategy for battery management systems in high-voltage, high-power scenarios.

[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0016] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0017] Figure 1 A flowchart illustrating a BMS low-side current limiting Buck duty cycle dynamic expansion control method provided in one embodiment of this application; Figure 2 This is a schematic diagram of a BMS low-side current limiting Buck duty cycle dynamic expansion control system provided in one embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical methods, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] It should be noted that the meaning of "multiple" (or "more than") in the description of the embodiments of this application refers to two or more, and "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, while "above," "below," "within," etc. are understood to include the number itself. If "first," "second," etc. are used in the description, they are only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0020] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, or the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: the existence of a alone, the existence of b alone, the existence of c alone, the simultaneous existence of a and b, the simultaneous existence of a and c, the simultaneous existence of b and c, or the simultaneous existence of a, b, and c, where a, b, and c can be single or multiple.

[0021] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0022] Based on the above, this application proposes a BMS low-side current limiting Buck duty cycle dynamic expansion control method and system, aiming to improve the efficiency and stability of the charging system and enhance the system's safety.

[0023] The BMS low-side rate limiting Buck duty cycle dynamic expansion control method provided in this application embodiment can be applied to a terminal, a server, or software running on either a terminal or a server. In some embodiments, the terminal can be a smartphone, tablet, laptop, desktop computer, etc.; the server can be configured as an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDN), and big data and artificial intelligence platforms; the software can be an application implementing the BMS low-side rate limiting Buck duty cycle dynamic expansion control method, etc., but is not limited to the above forms.

[0024] This application can be applied to numerous general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics devices, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices. This application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via communication networks. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices. It should be noted that in various specific embodiments of this invention, when processing is required based on data related to the characteristics of an object (e.g., user attributes or sets of attribute information), permission or consent from the corresponding object is obtained first, and the collection, use, and processing of this data comply with relevant laws and standards. Furthermore, when the embodiments of the present invention need to obtain the attribute information of an object, they will obtain the separate permission or separate consent of the corresponding object through pop-up windows or redirection to a confirmation page. After obtaining the separate permission or separate consent of the corresponding object, they will then obtain the relevant data of the object necessary for the embodiments of the present invention to operate normally.

[0025] See Figure 1 , Figure 1 This is a flowchart illustrating a BMS low-side current limiting Buck duty cycle dynamic expansion control method provided in one embodiment of this application. The BMS low-side current limiting Buck duty cycle dynamic expansion control method provided in this embodiment includes, but is not limited to, steps S110 to S150, which are described in detail below.

[0026] Step S110: When the battery management system calculates that the duty cycle required by the Buck converter exceeds the preset limit, the operating parameters of the Buck converter are obtained. Step S120: Obtain the predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter; Step S130: Dynamically adjust the maximum duty cycle limit of the Buck converter based on the predicted value of the bootstrap capacitor voltage. Step S140: When the predicted value of the bootstrap capacitor voltage is higher than the preset extension threshold, the maximum duty cycle limit is allowed to extend in order to maintain the charging current. Step S150: When the predicted value of the bootstrap capacitor voltage is lower than the preset callback threshold, the duty cycle callback mechanism is activated to avoid undervoltage of the bootstrap capacitor.

[0027] It's important to note that a Buck converter is a step-down DC-DC converter whose primary function is to convert an input DC voltage into a lower DC output voltage. It's commonly used in battery charging management systems. The operating parameters of a Buck converter typically include input voltage, output current, switching frequency, and duty cycle. These parameters form the basis for evaluating the converter's operating status and predicting the bootstrap capacitor voltage. The bootstrap capacitor is a key component in the low-side power switch driver circuit, providing the drive voltage to ensure the low-side switch can turn on and off normally. The predicted bootstrap capacitor voltage refers to an algorithmic estimation of the bootstrap capacitor's voltage at a future point in time to determine if it's within a safe operating range. The preset limit is the initial maximum duty cycle limit set by the system to protect the Buck converter and bootstrap capacitor. The preset extension threshold and preset callback threshold are two key voltage thresholds used to determine whether the predicted bootstrap capacitor voltage allows for duty cycle extension or requires triggering a callback mechanism. The duty cycle callback mechanism means that when the bootstrap capacitor voltage is too low, the system actively reduces the duty cycle to ensure the bootstrap capacitor has sufficient charging time and avoids undervoltage. When the battery management system (BMS) calculates that the required duty cycle of the Buck converter exceeds a preset limit, it needs to obtain the Buck converter's operating parameters. For example, sensors integrated into the BMS can monitor parameters such as the Buck converter's input voltage, output current, and switching frequency in real time. These parameters can be sampled by an analog-to-digital converter (ADC) and transmitted to the microcontroller for processing. Alternatively, these operating parameters can be indirectly obtained using a pre-defined lookup table or mathematical model, based on the Buck converter's current operating mode and load conditions.

[0028] In one embodiment, the predicted value of the bootstrap capacitor voltage is obtained based on the operating parameters of the Buck converter. One implementation involves establishing a simplified bootstrap capacitor charging and discharging model based on the operating parameters of the Buck converter, such as switching frequency, duty cycle, and drive current of the low-side switch. This model can predict the voltage change trend of the bootstrap capacitor in the next one or several switching cycles based on the current operating parameters, thus obtaining the predicted bootstrap capacitor voltage. For example, the discharge amount of the bootstrap capacitor in each switching cycle can be estimated based on the capacitance of the bootstrap capacitor, the gate charge of the low-side switch, and the switching frequency, and its charging status can be predicted by combining the voltage and resistance of the charging path. The maximum duty cycle limit of the Buck converter is dynamically adjusted based on the predicted bootstrap capacitor voltage. When the predicted bootstrap capacitor voltage is higher than a preset extension threshold, the maximum duty cycle limit is allowed to extend to maintain the charging current. For example, if the predicted value is much higher than a safety threshold, the system can gradually increase the maximum duty cycle limit, for example, from 95% to 97% or 98%, thereby allowing the Buck converter to still output the required charging current when the input voltage is low. This adjustment can be linear or piecewise, depending on the difference between the predicted bootstrap capacitor voltage and the preset extended threshold. Alternatively, fuzzy control or adaptive control algorithms can be used to intelligently adjust the maximum duty cycle limit based on the relationship between the predicted bootstrap capacitor voltage and the preset extended threshold, as well as the operating state of the Buck converter. When the predicted bootstrap capacitor voltage falls below the preset callback threshold, a duty cycle callback mechanism is activated to prevent undervoltage of the bootstrap capacitor. For example, when the predicted value falls below the preset callback threshold, the system immediately reduces the Buck converter's duty cycle, for example, by a preset step size or rate, thereby increasing the turn-off time of the low-side switch and providing a longer charging time for the bootstrap capacitor. This callback mechanism ensures that the bootstrap capacitor voltage recovers to a safe range, preventing damage to the low-side switch due to excessively long drive-on time. Alternatively, the step size or callback period of the duty cycle callback can be dynamically adjusted based on the deviation between the predicted bootstrap capacitor voltage and the preset callback threshold to achieve a finer and faster response.

[0029] This application's BMS low-side current-limiting Buck duty cycle dynamic expansion control method dynamically adjusts the maximum duty cycle limit of the Buck converter by introducing a bootstrap capacitor voltage prediction mechanism. When the battery management system calculates that the required duty cycle of the Buck converter exceeds the preset limit, the system first obtains the operating parameters of the Buck converter and then obtains the predicted value of the bootstrap capacitor voltage based on these parameters. If the predicted value is higher than the preset expansion threshold, it indicates that the bootstrap capacitor has sufficient margin, and the system allows the maximum duty cycle limit to expand, thereby maintaining the required charging current even when the input voltage fluctuates, avoiding the charging interruption or current drop problems caused by traditional fixed duty cycle limits. Conversely, when the predicted value is lower than the preset callback threshold, the system immediately activates the duty cycle callback mechanism, actively reducing the duty cycle to provide sufficient charging time for the bootstrap capacitor, thereby effectively avoiding undervoltage of the bootstrap capacitor and protecting the low-side power switch from damage. The entire process forms a closed-loop control, enabling the Buck converter to maximize its efficiency and adaptability while ensuring safety.

[0030] It should be noted that the "non-limit duty cycle extension range" refers to the range within which the Buck converter's operating duty cycle has not yet reached its maximum permissible extension limit. Within this range, the charging conditions of the bootstrap capacitor are relatively stable, which is beneficial for accurate parameter monitoring. "Input voltage stability" means that the input voltage fluctuation of the Buck converter is within an acceptable range, ensuring that the bootstrap capacitor charging process is not significantly affected by external power supply instability. The "bootstrap capacitor charging parameters" can be understood as measurable physical quantities related to the bootstrap capacitor charging process during normal Buck converter operation, such as the voltage across the bootstrap capacitor and the charging current. Monitoring these parameters aims to provide raw data for subsequent calculations of voltage changes and charging time. The "voltage changes and charging time of the bootstrap capacitor during monitoring" are obtained by processing the monitored bootstrap capacitor charging parameters. For example, during the conduction of the low-side switch, the rise in voltage across the bootstrap capacitor and the duration of this conduction can be measured. The purpose is to quantify the charging behavior of the bootstrap capacitor within a specific time period. The "estimated actual average charging current of the bootstrap capacitor" is calculated based on the aforementioned voltage change and charging time, combined with the nominal or calibrated capacity of the bootstrap capacitor, using the principle of charge conservation. Its purpose is to obtain a charging current value closer to reality to correct the prediction model. The "average charging current parameter used in the prediction program" refers to the preset or empirically set charging current value in the mathematical model used to predict the bootstrap capacitor voltage within the BMS or Buck controller. This parameter may deviate from the actual situation due to factors such as device aging and temperature changes. The "charging efficiency correction factor" is a proportionality coefficient calculated by comparing the estimated "actual average charging current" with the "average charging current parameter used in the prediction program." Its purpose is to quantify the deviation of the charging current parameter in the prediction model and use it for subsequent corrections. "Update the average charging current parameter used in the prediction program" means applying the calculated charging efficiency correction factor to the average charging current parameter in the prediction model to more accurately reflect the current actual charging conditions. In this way, the accuracy of bootstrap capacitor voltage prediction can be improved, thus providing a more reliable basis for the dynamic adjustment of the maximum duty cycle limit of the Buck converter.

[0031] In one embodiment, when the predicted value of the bootstrap capacitor voltage approaches a preset callback threshold, it means that the difference between the predicted value and the preset callback threshold is less than or equal to a preset voltage margin, for example, when the predicted value enters a warning range. In this case, the system predicts the voltage value of the bootstrap capacitor after a preset number of cycles based on the operating parameters of the Buck converter, such as input voltage, output current, and switching frequency. This prediction can be estimated by establishing a discharge model of the bootstrap capacitor, combined with the current load conditions and switching cycles. Simultaneously, the system also calculates the bootstrap capacitor voltage drop rate, which can be obtained by monitoring the voltage change of the bootstrap capacitor over multiple consecutive switching cycles and dividing by the corresponding time interval, and can be filtered to improve accuracy. Adjusting the response speed of the duty cycle callback mechanism can be understood as dynamically adjusting the step size, callback frequency, or callback trigger point of the duty cycle callback based on the predicted future voltage trend and voltage drop rate. For example, if it is predicted that the bootstrap capacitor voltage will drop rapidly and fall below the callback threshold in a short period of time, the step size of the duty cycle callback can be increased or the callback frequency can be accelerated to reduce the duty cycle more quickly; conversely, if it is predicted that the voltage drop trend is gradual, a smaller callback step size or a slower callback frequency can be used to achieve a smooth transition.

[0032] It's important to note that the critical component temperatures of a Buck converter refer to the temperatures of heat-sensitive components within the converter that significantly impact system performance and lifespan, such as power switches, inductors, and output capacitors. These temperatures can be monitored in real-time using temperature sensors integrated within the components or external thermistors. Buck converter operating parameters include input voltage, output current, switching frequency, and duty cycle, which directly affect power loss and heat generation. The low-side power switch is one of the main heat sources in a Buck converter, and its junction temperature is a key indicator of its thermal stress. The estimated junction temperature rise trend can be calculated by establishing a thermal model and combining it with the Buck converter's operating parameters and power loss; for example, it can be estimated based on the switch's conduction and switching losses, as well as its thermal resistance. Preset thresholds are upper limits set based on the safe operating temperature range of the components and system reliability requirements. When the monitored critical component temperature or the estimated junction temperature rise trend reaches or exceeds these thresholds, it indicates a risk of overheating. In this case, the system will take measures to reduce the maximum duty cycle limit, thereby reducing power loss and bringing the component temperature back to the safe operating range.

[0033] In one embodiment, assuming an electric vehicle's BMS system is charging, during which the battery voltage rises, the Buck converter needs to extend its duty cycle to its limit to maintain a constant charging current. At this time, the system continuously monitors the temperature of the low-side MOSFET, inductor, and output diode in the Buck converter. Simultaneously, based on current operating parameters such as input voltage, output current, and switching frequency, the system estimates the junction temperature rise trend of the low-side MOSFET in real time. For example, when the surface temperature sensor of the low-side MOSFET detects a temperature of 85°C, or the estimated junction temperature rise rate indicates that it will exceed the safe junction temperature threshold of 120°C in the near future, the system will immediately trigger a thermal protection mechanism, even if the bootstrap capacitor voltage prediction still allows for duty cycle extension. Specifically, the maximum duty cycle limit will be gradually or rapidly reduced, for example, from 95% to 90%, or even lower, until the temperature of critical components falls back to a preset safe range, such as the MOSFET surface temperature falling below 80°C. In this way, the charging current is maintained as much as possible while avoiding component failure due to overheating, ensuring the long-term stable operation of the charging system.

[0034] It should be noted that obtaining the actual voltage drop rate of the bootstrap capacitor refers to monitoring the voltage across the bootstrap capacitor in real time or periodically and calculating the ratio of its voltage change over a specific time period to that time period. The current voltage drop trend and speed can be estimated by continuously sampling the bootstrap capacitor voltage and using algorithms such as differential or linear regression. The purpose is to obtain real-time dynamic information on the bootstrap capacitor voltage changes, providing an accurate basis for subsequent duty cycle adjustments. The deviation between the predicted bootstrap capacitor voltage and the preset adjustment threshold can be understood as the margin between the currently predicted bootstrap capacitor voltage and the system's set safety lower limit (i.e., the preset adjustment threshold). The magnitude of this deviation directly reflects how close the bootstrap capacitor is to an undervoltage state. For example, a larger deviation indicates that the bootstrap capacitor still has sufficient voltage margin; a smaller deviation indicates that the bootstrap capacitor is close to the undervoltage edge and requires more urgent intervention. Its purpose is to quantify the risk level of the bootstrap capacitor. Adjusting the duty cycle callback step size or callback period refers to dynamically changing the magnitude (step size) or frequency (callback period) of the duty cycle reduction based on the actual voltage drop rate and prediction deviation obtained above. For example, when the actual voltage drop rate is fast and the prediction deviation is small, a larger callback step size and a shorter callback period can be used to reduce the Buck converter's duty cycle more quickly and aggressively, thereby rapidly increasing the bootstrap capacitor voltage. Conversely, when the actual voltage drop rate is slow and the prediction deviation is large, a smaller callback step size and a longer callback period can be used to adjust the duty cycle more smoothly and gently, minimizing the impact on the charging current while ensuring the safety of the bootstrap capacitor. The aim is to achieve intelligent and adaptive duty cycle callback mechanisms.

[0035] In one embodiment, assuming that during the charging process of the Buck converter, the bootstrap capacitor voltage predicted by the BMS system gradually decreases and approaches a preset callback threshold, the system continuously monitors the actual voltage of the bootstrap capacitor and calculates its actual voltage drop rate over a recent period. For example, if a rapid voltage drop rate is detected and the deviation between the predicted value and the callback threshold is small, indicating a high risk of undervoltage, the system will activate the duty cycle callback mechanism, selecting a larger callback step size and a shorter callback period to quickly reduce the duty cycle and rapidly increase the bootstrap capacitor voltage, thereby effectively avoiding undervoltage. Conversely, if the actual voltage drop rate is slow and the deviation between the predicted value and the callback threshold is large, the system will select a smaller callback step size and a longer callback period to smoothly adjust the duty cycle, minimizing the impact on the charging current while ensuring the safety of the bootstrap capacitor.

[0036] It should be noted that multi-period moving average filtering refers to averaging continuously acquired data points within a certain time window to smooth the data and remove high-frequency noise and transient interference. For example, for the actual voltage drop rate of the bootstrap capacitor, the drop rate values ​​can be continuously acquired for N periods, and then the average of these N values ​​can be calculated as the current filtered actual voltage drop rate. Similarly, the deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold can also be processed using a similar multi-period moving average filtering method. N can be set according to the actual application scenario and the requirements for response speed and smoothness; for example, it can be set to 3, 5, 10, or more periods. In this way, the impact of a single measurement error on the overall judgment can be effectively reduced, making the input parameters used for the duty cycle callback mechanism more stable and reliable. The solution in this application effectively solves the problem of unstable response or misjudgment of the duty cycle callback mechanism that may be caused by directly using the original measurement data by introducing multi-period moving average filtering. Specifically, filtering the actual voltage drop rate of the bootstrap capacitor and the deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold can eliminate transient noise and interference that may exist during the measurement process. Because these key parameters have been smoothed, the system can base its judgments on more stable and representative data when determining the bootstrap capacitor status and adjusting the duty cycle callback strategy. This makes the duty cycle callback mechanism's decision-making more accurate, avoiding frequent or unnecessary duty cycle adjustments caused by data fluctuations, thereby improving the robustness and reliability of the entire control system.

[0037] In one embodiment, it is assumed that during a certain duty cycle, the actual voltage drop rate of the bootstrap capacitor in the Buck converter experiences a spike due to transient interference, or the deviation between the predicted bootstrap capacitor voltage and a preset callback threshold temporarily deviates from the true value due to measurement noise. If these unprocessed transient data are used directly, the system may incorrectly determine that the bootstrap capacitor is about to become undervoltage, thus prematurely or excessively activating the duty cycle callback mechanism, leading to unexpected fluctuations in the charging current. Specifically, when using the solution of this application, the system continuously collects the actual voltage drop rate and prediction deviation data of the bootstrap capacitor. For example, a 5-cycle moving average window is set. In each new cycle, the latest measurement value is added to the dataset, while the oldest measurement value is removed, and then the average of these 5 values ​​is calculated. In this way, even if the data in a certain cycle is abnormal, its impact will be averaged by the data in other normal cycles, thereby obtaining a smoother and more realistic filtered actual voltage drop rate and filtered prediction deviation. For example, the original voltage drop rate sequence might be [10, 12, 100, 11, 13, 12, ...]. After a 5-cycle moving average filter, the impact of the outlier 100 is significantly reduced, making the data received by the system more stable, for example, [10, 12, (10+12+100+11+13) / 5=29.2, (12+100+11+13+12) / 5=29.6, ...]. Based on this filtered stable data, the duty cycle callback mechanism can make more accurate and stable decisions, such as adjusting the step size or callback period of the duty cycle callback, so that the callback is only initiated when truly needed and adjusted at an appropriate rate, effectively avoiding undervoltage of the bootstrap capacitor while maintaining the stability of the charging current.

[0038] It should be noted that during the calibration process, the bootstrap capacitor is charged while the low-side switch is on. At this time, by monitoring the voltage across the bootstrap capacitor, the voltage change and charging time within a specific charging cycle can be obtained. For example, a high-precision voltage sensor and timer can be used to accurately measure these parameters. Subsequently, based on the obtained voltage change, charging time, and known charging current, the actual charge amount of the bootstrap capacitor during the monitoring period can be calculated. The charge amount can be obtained by multiplying the charging current by the charging time. Further, using the calculated actual charge amount and the measured voltage change of the bootstrap capacitor, the actual capacitance of the bootstrap capacitor can be estimated. The capacitance of the bootstrap capacitor can be determined by the ratio of the charge amount to the voltage change. By comparing the estimated actual capacitance with the preset or currently used bootstrap capacitor capacitance parameters in the prediction program, a capacitance correction factor can be calculated. This correction factor reflects the deviation between the actual capacitance and the program parameters. Based on this capacitance correction factor, the bootstrap capacitor capacitance parameters used in the prediction program will be updated. This update ensures that subsequent bootstrap capacitor voltage prediction calculations are based on capacitance values ​​closer to reality. Ultimately, when adjusting the duty cycle callback step size or callback period, the updated bootstrap capacitor capacitance parameters will be applied to the bootstrap voltage margin prediction module's calculations. By using more accurate capacitance parameters, the filtered actual voltage drop rate and the filtered prediction deviation can be corrected, resulting in more precise and timely adjustments to the duty cycle callback step size or callback period.

[0039] It's important to note that obtaining the current ambient temperature and Buck converter output power refers to acquiring the ambient temperature and current output power of the Buck converter in real time through appropriate sensors or internal status monitoring modules. Ambient temperature is typically measured using a temperature sensor, while output power can be calculated from output voltage and current. These parameters are considered key inputs for assessing the aging status of the bootstrap capacitor. Specifically, estimating the current aging rate of the bootstrap capacitor based on the ambient temperature and output power, combined with a pre-defined aging rate curve, can be understood as utilizing a pre-established capacitor aging model. This model is usually based on extensive experimental data, describing the decay of bootstrap capacitor capacity over time under different temperature and load conditions. By substituting the real-time ambient temperature and output power into this model, the aging rate of the bootstrap capacitor at the current moment can be estimated. Dynamically adjusting the actual capacity calibration cycle of the bootstrap capacitor based on its aging rate specifically means intelligently adjusting the frequency of actual capacity calibration based on the estimated aging rate. For example, when the estimated aging rate is high, the calibration cycle can be shortened to update the capacity parameters more frequently; when the aging rate is low, the calibration cycle can be appropriately extended to reduce system overhead. When the cumulative deviation of the bootstrap capacitor voltage prediction exceeds a preset threshold, the actual capacity calibration of the bootstrap capacitor is triggered. This means that in addition to periodic adjustments based on aging rate, a performance feedback-based triggering mechanism is introduced. The bootstrap capacitor voltage prediction deviation refers to the difference between the predicted value and the actual measured value. By accumulating these deviations, the accuracy of the prediction model or capacity parameter can be reflected. Once the accumulated deviation exceeds the preset threshold, it indicates that the current capacity parameter may no longer be accurate enough. At this point, the system will immediately trigger an actual capacity calibration of the bootstrap capacitor to correct the deviation.

[0040] In one embodiment, it is assumed that the BMS system of an electric vehicle employs the Buck duty cycle dynamic extension control method of this application. During vehicle operation, the system continuously monitors the ambient temperature inside the battery compartment and the output power of the Buck converter charging the battery. For example, when the vehicle operates in a high-temperature environment for an extended period or is rapidly charged with a high current, the system estimates that the current aging rate of the bootstrap capacitor is accelerating based on a preset aging rate curve (which may be obtained through accelerated aging experiments in the laboratory and stored in the BMS's memory). At this time, the system dynamically shortens the calibration cycle of the actual capacity of the bootstrap capacitor, for example, adjusting it from once every 100 hours to once every 50 hours, to update the capacity parameters of the bootstrap capacitor more frequently and ensure its accuracy. Simultaneously, the system continuously calculates the deviation between the predicted value and the actual measured value of the bootstrap capacitor voltage and accumulates these deviations. For example, if the predicted voltage is systematically higher than the actual voltage for several consecutive cycles, and the accumulated deviation exceeds a preset 50mV threshold, this may indicate that the actual capacity of the bootstrap capacitor is lower than the parameters used in the prediction program. In this scenario, even before the dynamically adjusted calibration cycle has been reached, the system will immediately trigger a calibration of the actual capacity of the bootstrap capacitor. This instantaneous calibration quickly corrects the capacity parameters, preventing duty cycle control errors caused by inaccurate capacity estimation. This effectively prevents the risk of undervoltage in the bootstrap capacitor and ensures the stability and safety of the charging process.

[0041] It should be noted that during the conduction period of the low-side switch, acquiring the voltage data across the bootstrap capacitor refers to periodically sampling the voltage across the bootstrap capacitor using an analog-to-digital converter (ADC). The sampling frequency should be set sufficiently to capture the voltage change trend of the bootstrap capacitor during charging. Digital low-pass filtering is applied to the voltage data across the bootstrap capacitor to remove high-frequency noise. Specifically, since the Buck converter generates high-frequency switching noise during operation, this noise may be superimposed on the voltage measurement of the bootstrap capacitor, affecting the accuracy of the measurement. Therefore, by applying a digital low-pass filter, such as a moving average filter or a Butterworth filter, this high-frequency noise can be effectively filtered out, resulting in a smoother and more realistic voltage waveform. Furthermore, identifying the start and end times of the low-side switch's conduction and obtaining the actual conduction time specifically refers to accurately determining the time from turn-off to turn-on and from turn-on to turn-off of the low-side switch by monitoring the gate drive signal of the low-side switch or the voltage state across it. The time interval between these two moments is the actual on-time of the low-side switch, which is recorded as the charging time of the bootstrap capacitor. Obtaining the filtered voltage values ​​at the start and end times specifically involves extracting the voltage values ​​corresponding to the start and end times of the low-side switch's on-time from the filtered voltage data after digital low-pass filtering. These filtered voltage values ​​represent the stable voltage levels of the bootstrap capacitor at the start and end of charging. Therefore, based on the filtered voltage values ​​and the actual on-time, the voltage change and charging time of the bootstrap capacitor under conditions free from high-frequency noise interference are obtained. Specifically, the voltage change of the bootstrap capacitor can be obtained by subtracting the filtered voltage value at the start time from the filtered voltage value at the end time. The charging time is directly taken from the previously obtained actual on-time. Through these steps, it can be ensured that the obtained voltage change and charging time of the bootstrap capacitor are accurate and free from high-frequency noise interference, providing reliable input data for subsequent bootstrap capacitor capacitance calibration.

[0042] See Figure 2 , Figure 2 This is a schematic diagram of a BMS low-side current limiting Buck duty cycle dynamic expansion control system provided in one embodiment of this application. The BMS low-side current limiting Buck duty cycle dynamic expansion control system 200 includes: The acquisition module 210 is used to acquire the operating parameters of the Buck converter when the battery management system calculates that the required duty cycle of the Buck converter exceeds the preset limit. The prediction module 220 is used to obtain the predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter. The adjustment module 230 is used to dynamically adjust the maximum duty cycle limit of the Buck converter based on the predicted value of the bootstrap capacitor voltage. When the predicted value of the bootstrap capacitor voltage is higher than the preset extension threshold, the maximum duty cycle limit is allowed to extend to maintain the charging current. When the predicted value of the bootstrap capacitor voltage is lower than the preset callback threshold, the duty cycle callback mechanism is activated to avoid undervoltage of the bootstrap capacitor.

[0043] It should be noted that the information interaction and execution process between the above modules are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, which will not be repeated here.

[0044] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically include computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0045] The above provides a detailed description of the preferred embodiments of this application. However, this application is not limited to the above-described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined in this application.

Claims

1. A BMS low-side current-limiting Buck duty-cycle dynamic extension control method, characterized in that, include: When the battery management system calculates that the duty cycle required by the Buck converter exceeds the preset limit, it obtains the operating parameters of the Buck converter. Based on the operating parameters of the Buck converter, the predicted value of the bootstrap capacitor voltage is obtained; The maximum duty cycle limit of the Buck converter is dynamically adjusted based on the predicted value of the bootstrap capacitor voltage. When the predicted value of the bootstrap capacitor voltage is higher than the preset extension threshold, the maximum duty cycle limit is allowed to extend in order to maintain the charging current; When the predicted value of the bootstrap capacitor voltage is lower than the preset callback threshold, the duty cycle callback mechanism is activated to avoid the bootstrap capacitor discharge time being too short.

2. The method of claim 1, wherein, The step of obtaining the predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter includes: When the Buck converter is operating in the non-limited duty cycle extended range and the input voltage is stable, monitor the bootstrap capacitor charging parameters. The voltage change and charging time of the bootstrap capacitor during the monitoring period are obtained based on the bootstrap capacitor charging parameters. Based on the voltage change and charging time of the bootstrap capacitor during the monitoring period, the actual average charging current of the bootstrap capacitor is estimated. The charging efficiency correction factor is calculated based on the actual average charging current and the average charging current parameters used in the prediction program. Based on the charging efficiency correction factor, the average charging current parameter used in the prediction program is updated, and the bootstrap capacitor voltage prediction value is obtained based on the operating parameters of the Buck converter.

3. The method of claim 1, wherein, When the predicted value of the bootstrap capacitor voltage is higher than the preset extension threshold, the step of allowing the maximum duty cycle limit to extend to maintain the charging current further includes: When the predicted value of the bootstrap capacitor voltage approaches the preset callback threshold... Based on the operating parameters of the Buck converter, predict the voltage value of the bootstrap capacitor after a preset number of cycles; Calculate the bootstrap capacitor voltage drop rate based on the operating parameters of the Buck converter; Based on the voltage value of the bootstrap capacitor after a preset number of cycles and the rate of voltage drop of the bootstrap capacitor, the response speed of the duty cycle callback mechanism is adjusted to dynamically adjust the maximum duty cycle limit of the Buck converter.

4. The method according to claim 1, characterized in that, The step of allowing the maximum duty cycle limit to extend to maintain the charging current when the predicted value of the bootstrap capacitor voltage is higher than the preset extension threshold further includes: Monitor the temperature of key components of the Buck converter; Based on the operating parameters of the Buck converter, estimate the junction temperature rise trend of the low-side power switch. When the temperature of a critical component of the Buck converter or the junction temperature rises above a preset threshold, the maximum duty cycle limit is reduced to restore the temperature of the critical component of the Buck converter to a safe range.

5. The method according to claim 1, characterized in that, When the predicted value of the bootstrap capacitor voltage is lower than a preset callback threshold, the duty cycle callback mechanism is activated to avoid the bootstrap capacitor discharge time being too short. The steps include: Obtain the actual voltage drop rate of the bootstrap capacitor; Based on the deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold, and the actual voltage drop rate of the bootstrap capacitor, the duty cycle callback mechanism is activated to adjust the step size or callback period of the duty cycle callback in order to avoid undervoltage of the bootstrap capacitor.

6. The method according to claim 5, characterized in that, The step of initiating a duty cycle callback mechanism and adjusting the step size or callback period of the duty cycle callback to avoid undervoltage of the bootstrap capacitor based on the deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold, and the actual voltage drop rate of the bootstrap capacitor, includes: The actual voltage drop rate of the bootstrap capacitor is subjected to multi-cycle moving average filtering. The deviation between the predicted value of the bootstrap capacitor voltage and the preset callback threshold is subjected to multi-period moving average filtering. Based on the actual voltage drop rate after filtering and the predicted deviation after filtering, the duty cycle callback mechanism is activated to adjust the step size or callback period of the duty cycle callback in order to avoid undervoltage of the bootstrap capacitor.

7. The method according to claim 6, characterized in that, The step of activating the duty cycle callback mechanism based on the actual voltage drop rate after filtering and the predicted deviation after filtering, and adjusting the step size or callback period of the duty cycle callback to avoid undervoltage of the bootstrap capacitor, further includes: When the Buck converter is operating in the non-limiting duty cycle extended range and the input voltage is stable, the actual capacitance of the bootstrap capacitor is periodically calibrated. The calibration includes: During the conduction of the low-side switch, the voltage across the bootstrap capacitor is monitored to obtain the voltage change and charging time of the bootstrap capacitor. Calculate the actual charge amount of the bootstrap capacitor based on the voltage change of the bootstrap capacitor, the charging time, and the known charging current. The actual capacity of the bootstrap capacitor is estimated by using the actual amount of charging charge and the voltage change of the bootstrap capacitor. The actual capacity is compared with the bootstrap capacitor capacity parameter used in the prediction program, and the capacity correction factor is calculated. Update the bootstrap capacitor capacity parameter used in the prediction program according to the capacity correction factor; When adjusting the step size or callback period of the duty cycle callback, the updated bootstrap capacitor capacity parameter is applied to the calculation of the bootstrap voltage margin prediction module to correct the filtered actual voltage drop rate and the filtered prediction deviation, thereby adjusting the step size or callback period of the duty cycle callback.

8. The method according to claim 7, characterized in that, The steps following the periodic calibration of the actual capacitance of the bootstrap capacitor when the Buck converter is operating in the non-limiting duty cycle extension range and the input voltage is stable include: Get the current ambient temperature and the output power of the Buck converter; Based on the ambient temperature and the output power, and combined with the preset aging rate curve, the current aging rate of the bootstrap capacitor is estimated. The cycle for calibrating the actual capacity of the bootstrap capacitor is dynamically adjusted based on the bootstrap capacitor aging rate. When the cumulative value of the bootstrap capacitor voltage prediction deviation exceeds a preset threshold, the actual capacity calibration of the bootstrap capacitor is triggered.

9. The method according to claim 7, characterized in that, The step of monitoring the voltage across the bootstrap capacitor and obtaining the voltage change and charging time of the bootstrap capacitor during the conduction of the low-side switch includes: During the conduction of the low-side switch, the voltage data across the bootstrap capacitor is collected; The voltage data across the bootstrap capacitor is subjected to digital low-pass filtering to remove high-frequency noise; Identify the start and end times of the low-side switch's conduction and obtain the actual conduction time; Obtain the filtered voltage values ​​at the start time and the end time; Based on the filtered voltage value and the actual conduction time, the voltage change and charging time of the bootstrap capacitor under conditions free from high-frequency noise interference are obtained.

10. A BMS low-side current-limiting Buck duty cycle dynamic extended control system, characterized in that, The system includes: The acquisition module is used to acquire the operating parameters of the Buck converter when the battery management system calculates that the required duty cycle of the Buck converter exceeds the preset limit. The prediction module is used to obtain the predicted value of the bootstrap capacitor voltage based on the operating parameters of the Buck converter. The adjustment module is used to dynamically adjust the maximum duty cycle limit of the Buck converter based on the predicted value of the bootstrap capacitor voltage. When the predicted value of the bootstrap capacitor voltage is higher than a preset extension threshold, the maximum duty cycle limit is allowed to extend to maintain the charging current. When the predicted value of the bootstrap capacitor voltage is lower than a preset callback threshold, the duty cycle callback mechanism is activated to avoid the bootstrap capacitor discharge time being too short.

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