High-efficiency rectifier thermal management method based on SiC device

Abstract

The invention belongs to the technical field of high-efficiency rectifier thermal management, and provides a SiC device-based high-efficiency rectifier thermal management method, which comprises the following steps of: acquiring temperature distribution of a SiC device in a high-efficiency rectifier under a full-load condition, and acquiring a transient temperature rise area and a steady temperature rise area by analyzing a temperature change range; the global voltage and the local voltage of the SiC device are collected, whether a global avalanche phenomenon occurs or not is judged by comparing the change rate of the global voltage with a typical value, if yes, a thermal-electric coupling coefficient is calculated through the local voltage and the temperature, an avalanche breakdown source candidate grid area is extracted, and a local avalanche origin point is positioned; determining the specific position of an avalanche breakdown origin point; and outputting a space overlapping degree according to the thermal-electric coupling coefficient and the space overlapping proportion, judging whether transient temperature rise is caused by an avalanche breakdown phenomenon, and if the transient temperature rise is caused by avalanche breakdown, triggering avalanche breakdown protection optimization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-efficiency rectifier thermal management, in particular to a high-efficiency rectifier thermal management method based on SiC devices. BACKGROUND

[0002] With the development of power electronic systems towards high frequency, high power density and high efficiency, high-efficiency rectifiers based on silicon carbide (SiC) devices have become the core technology in the fields of new energy conversion, electric vehicle charging and smart grid, etc. SiC devices, such as MOSFET or Schottky diode, have much faster switching speed than Si devices, mainly because the carrier mobility of SiC is higher and the on-resistance is lower, so the dv / dt and di / dt change rates in the switching process are larger. When the switching speed increases, the parasitic inductance (such as lead inductance, PCB wiring inductance, internal inductance of the module, etc.) in the circuit will produce a larger voltage spike. According to the basic formula of inductance V=L*(di / dt), when di / dt increases, even if L is the same, the voltage V will also increase significantly. If the voltage spike exceeds the rated withstand voltage of the device, it will cause the device to enter an avalanche breakdown state. When the avalanche breakdown occurs, the device will withstand high voltage and large current, generating a large amount of heat and forming a local hot spot. If this situation occurs frequently, it will cause the device to overheat and even be damaged, which may lead to the failure of the high-efficiency rectifier. Therefore, the application provides a high-efficiency rectifier thermal management method based on SiC devices. SUMMARY

[0003] In order to make up for the deficiencies of the prior art and solve at least one technical problem raised in the background.

[0004] The technical scheme adopted by the application to solve the technical problems is: a high-efficiency rectifier thermal management method based on SiC devices, comprising the following steps: Collecting the temperature distribution of SiC devices in the high-efficiency rectifier under full load conditions, and obtaining the transient temperature rise area and the steady-state temperature rise area by analyzing the range of temperature change; Collecting the global voltage and local voltage of the SiC device, determining whether a global avalanche phenomenon occurs by comparing the global voltage change rate with the typical value, and if so, calculating the thermal-electric coupling coefficient by the local voltage and temperature, extracting the avalanche breakdown source candidate grid area and positioning the local avalanche origin point to determine the specific position of the avalanche breakdown origin point; According to the thermal-electric coupling coefficient and the spatial overlap ratio, the spatial overlap degree is output, and it is judged whether the transient temperature rise is caused by the avalanche breakdown phenomenon. If the transient temperature rise is caused by the avalanche breakdown, the avalanche breakdown protection optimization is triggered. After implementing the avalanche breakdown protection optimization, the heat conduction path of the transient temperature rise region to the steady temperature rise region is predicted through the thermal coupling model, the steady temperature rise region which is heated due to the transient heat conduction of the transient temperature rise region is marked as an affected region, the temperature changes of the transient temperature rise region and the affected region before and after the optimization are analyzed, a comprehensive optimization coefficient is output, and the optimization effect is evaluated.

[0005] The beneficial effects of the present application are as follows: The present application determines the thermal failure causes and triggers targeted protection optimization by analyzing the spatial overlap and thermal-electric coupling relationship of the avalanche breakdown and the transient temperature rise, further combines the thermal coupling model to evaluate the optimization effect and iteratively adjusts the strategy, which not only reduces the invalid optimization of non-critical factors, but also fundamentally suppresses the thermal failure risk caused by the avalanche breakdown, significantly improving the reliability and service life of the SiC device and the rectifier. BRIEF DESCRIPTION OF DRAWINGS

[0006] The present application will be further described below with reference to the accompanying drawings.

[0007] Figure 1 is a step flowchart of a high-efficiency rectifier thermal management method based on a SiC device of the present application; Figure 2 is a flowchart of step S2 of a high-efficiency rectifier thermal management method based on a SiC device of the present application; Figure 3 is an architecture diagram of a high-efficiency rectifier thermal management system based on a SiC device of the present application. DETAILED DESCRIPTION

[0008] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the present application will be further described below with reference to the specific embodiments.

[0009] Embodiment 1 Please refer to Figure 1 and Figure 2 , a high-efficiency rectifier thermal management method based on a SiC device according to an embodiment of the present application includes the following steps: Step S1: Collect the temperature distribution of the SiC device in the high-efficiency rectifier under full load conditions, and obtain the transient temperature rise region and the steady temperature rise region by analyzing the range of temperature change; In some embodiments, the definition of full load conditions: set the input voltage range, output current and environmental temperature to make the test reproducible; For example, define the input voltage range as 600V±5%, the output current as 120A, and the environmental temperature as a 25℃ constant temperature box; Divide the surface of the SiC device into several regions in a grid format; Optionally, SiC device surface meshing division: according to the SiC power module packaging structure, a two-dimensional coordinate system is established along the surface of the SiC device, an equal-interval meshing is adopted, and a fine division is performed with a mesh interval of 2.4 mm*2.4 mm; in the known heat concentration areas of the SiC device pin connection area, gate drive area, and power loop connection, mesh encryption is implemented, which can be divided according to 0.8 mm*0.8 mm; the physical coordinates of each mesh node are determined, and a mapping relationship with the three-dimensional model of the device is established; Among them, in the encryption mesh area, the judgment of transient temperature rise is more sensitive, which can capture local subtle thermal transients and reduce the missed judgment of thermal hazards caused by overall temperature averaging; Set the collection frequency to obtain the temperature value of each area at the collection time, and calculate the temperature change rate corresponding to the adjacent collection time of each area; In the collection period, for each area, the collection time with a positive temperature change rate is extracted as the temperature rise time; Compare the temperature change rate at the temperature rise time with the temperature change rate limit value; if the temperature change rate is greater than the temperature change rate limit value, mark it as transient temperature rise; if the temperature change rate is less than or equal to the temperature change rate limit value, mark it as steady-state temperature rise; Among them, by setting the temperature change rate limit value, the two temperature rise modes can be distinguished from the dynamics; when the temperature change rate exceeds the limit value, it indicates that the heat accumulation rate exceeds the steady-state heat dissipation capacity, which belongs to transient thermal shock, otherwise it is steady-state heat accumulation; the temperature change rate limit value is determined by the material properties, failure physical mechanism and application scenario of the SiC device, which needs to be calibrated through simulation and experiment; Statistically, the number of temperature rise times of transient temperature rise is calculated, and the ratio of the number of temperature rise times of transient temperature rise to the total number of collection times is taken as the proportion of transient temperature rise time; Compare the proportion of transient temperature rise time with the proportion limit value of transient temperature rise time; if the proportion of transient temperature rise time is greater than the proportion limit value of transient temperature rise time, the area frequently experiences transient thermal shock, and is marked as a transient high-temperature area; if the proportion of transient temperature rise time is less than or equal to the proportion limit value of transient temperature rise time, the area is marked as a steady-state temperature rise area; Among them, the proportion limit value of transient temperature rise time is set by technicians in the art based on the fatigue life model and system reliability target, and is generally set at 20%-30%; It needs to be explained that the proportion of transient temperature rise time represents the proportion of the number of transient temperature rise times to the total number of collection times, which is used to evaluate the persistence of the thermal characteristics of the area; Through the dual judgment logic of temperature change rate and proportion of transient time, the thermal response of the SiC device is divided into transient and steady-state modes, which is essentially to realize the accurate positioning of thermal hazards from the two dimensions of thermal shock intensity and thermal stress persistence; Step S2: Collecting the electrical parameters of the SiC device, identifying whether the avalanche breakdown phenomenon occurs, and if so, analyzing the overlap degree of the avalanche breakdown phenomenon and the transient heating area based on the spatial position; In some embodiments, the electrical parameters of the SiC device are collected at a high speed and synchronously to detect the avalanche phenomenon; The electrical parameters include voltage parameters, because the essence of avalanche breakdown is a voltage-driven physical process; A detection circuit is connected in parallel across the drain and source of the SiC device to detect the global voltage, and micro-voltage probes are arranged at key areas on the surface of the SiC device to detect the local voltage; wherein the key areas at least include the terminal edge and the JFET region; The collected overall voltage and local voltage are subjected to a moving average filter to remove high-frequency noise and suppress the interference of switching noise on the avalanche feature extraction; Whether the avalanche breakdown triggers the avalanche breakdown phenomenon is determined by the global voltage and the local voltage; The determination process by the global voltage is as follows: The global voltage change rate is calculated, which is the ratio of the difference of the global voltage at adjacent collection times to the difference of the adjacent collection times; The global voltage change rate is compared with a typical value, if the voltage change rate is greater than the typical value, it is determined that the global avalanche phenomenon is triggered, otherwise, it is determined that the global avalanche phenomenon is not triggered; The typical value is set by the person skilled in the art according to experience and industry specifications, which can be set to ; After determining that the global avalanche phenomenon is triggered, the local avalanche is located by the local voltage, and the process is as follows: The voltage difference of adjacent micro-voltage probes is calculated to construct a voltage gradient vector; If the amplitude of the voltage gradient vector exceeds the amplitude threshold and the direction points to the inside of the SiC device, it indicates that the electric field is concentrated; The direction pointing to the SiC device or not is determined by the coordinate system direction; The transient heating area marked in the foregoing step S1 is mapped to the surface coordinate system of the SiC device; The occurrence time of triggering the global avalanche phenomenon is obtained, and the local voltage of all micro-voltage probes and the temperature value of the corresponding grid area are extracted; The thermal-electric coupling coefficient is calculated, and the calculation formula is as follows: ; wherein C represents the thermal-electric coupling coefficient, represents the temperature of the i-th grid area, represents the i-th local voltage change value, and N represents the total number of grid areas; The grid area with a thermal-electric coupling coefficient greater than a coupling coefficient threshold is extracted to determine as a candidate grid area of the avalanche breakdown source; Extracting the grid area with the thermal-electric coupling coefficient greater than the coupling coefficient threshold as a candidate avalanche breakdown source grid area; Sorting the voltage change values of all micro-voltage probes, and taking the grid where the micro-voltage probe with the largest voltage change value is located as the avalanche origin point; The role of identifying the avalanche origin point is to provide a targeted position for the targeted implementation of avalanche breakdown protection optimization, to focus on the cooling scheme of the area where the avalanche origin point is located, to improve the accuracy of the thermal management strategy, and to reduce the waste of resources caused by indiscriminate heat dissipation. The thermal-electric coupling coefficient reflects the synergistic effect of temperature rise and voltage mutation in space, and captures the spatial co-location of temperature and voltage change through the product term. If the two are completely overlapped in space, for example, the avalanche breakdown source causes local electric field concentration and high temperature at the same time, then the thermal-electric coupling coefficient is close to 1, and if the two are not overlapped in space, then the thermal-electric coupling coefficient is close to 0. The role of the calculated thermal-electric coupling coefficient is that: first, it can reflect the systematic effect of temperature rise and voltage mutation in space; second, by comparing with the threshold value, it extracts the candidate grid area of the avalanche breakdown source, provides the basis for subsequent accurate positioning of the avalanche origin point, and helps to identify the specific location of the avalanche breakdown origin point; third, in the following step S3, it is used as one of the indicators to judge whether the transient temperature rise is caused by avalanche breakdown, combined with the spatial overlap area, to comprehensively evaluate the relevance of transient temperature rise and avalanche breakdown in physical and control dimensions, and to extract the basis for whether to trigger the avalanche breakdown protection optimization; Step S3: According to the spatial overlap degree, it is judged whether the transient temperature rise is caused by avalanche breakdown. If the transient temperature rise is caused by avalanche breakdown, the avalanche breakdown protection optimization is triggered. In some embodiments, the avalanche breakdown source and the candidate source grid area of the avalanche breakdown are obtained as the avalanche breakdown related area, and are spatially matched with the transient temperature rise area marked in the aforementioned step S1; The total area of the overlapping grid area of the avalanche breakdown related area and the transient temperature rise area is obtained, and the total area of the overlapping grid area is calculated by the ratio of the total area of the transient temperature rise area to obtain the overlapping area ratio; The grid area is calculated according to the grid division rule in the aforementioned step S1; The thermal-electric coupling coefficient corresponding to the total area of the overlapping grid area is averaged; The overlapping area ratio and the average thermal-electric coupling coefficient are weighted and fused to output the spatial overlap degree; The weight coefficient of the overlap area ratio and the average thermal-electric coupling coefficient is obtained by a large number of failure test data (such as the correlation sample of avalanche breakdown time and transient temperature rise recorded in the accelerated aging test), and the optimal weight is obtained by statistical methods (such as least squares method, logistic regression) to make the correlation between the weighted spatial overlap degree and the actual incidence (real label) of "avalanche breakdown leading to transient temperature rise" highest; if the contribution of the thermal-electric coupling coefficient is greater in 80% of the real correlation samples in the experiment, the weight of the thermal-electric coupling coefficient is increased; The spatial overlap degree reflects the overall correlation strength between the avalanche breakdown related region (avalanche source and candidate source) and the transient temperature rise region on the surface of the SiC device, from the spatial position coincidence to the thermal-electric physical mechanism coupling; By fusing the thermal-electric coupling coefficient and the overlap area ratio, for the causal relationship judgment of the avalanche breakdown phenomenon and the transient temperature rise, the following effects are achieved: first, the causal relationship can be accurately judged by comprehensively verifying from the physical correlation and the spatial distribution; second, by fusing the indicators, the contribution of the avalanche breakdown in the transient temperature rise can be more clearly understood, the core inducement can be identified, and the subsequent thermal management strategy can be targeted to solve the key problems, thereby improving the effectiveness of thermal management; third, by accurately judging the causal relationship and implementing targeted optimization, the local hot spots and device overheating risks caused by avalanche breakdown can be reduced from the root, the probability of damage of the SiC device due to thermal failure is reduced, and the reliability and service life of the high-efficiency rectifier based on the SiC device are improved; If the spatial overlap degree is less than the spatial overlap degree threshold, it is determined that the transient temperature rise is not caused by the avalanche breakdown phenomenon, and other thermal management strategies are executed, including but not limited to: optimizing the heat dissipation mechanism; If the spatial overlap degree is greater than or equal to the spatial overlap degree threshold, it is determined that the transient temperature rise is caused by the avalanche breakdown phenomenon, and the avalanche breakdown protection optimization process is triggered; The avalanche breakdown protection optimization process includes the following optimization measures: The gate drive circuit dynamically adjusts the drive resistance, increases the drive resistance at the initial stage of conduction to reduce di / dt (ratio of current change to time experienced by current change) t, and reduces the drive resistance at the initial stage of turn-off to reduce dv / dt, thereby suppressing the voltage peak amplitude; The directional cooling enhancement is started for the avalanche origin point region, such as controlling the flow of the micro liquid cooling channel to be increased, or triggering the local thermoelectric refrigeration module (TEC) to start, so that the temperature of the avalanche origin point region is reduced at an increased rate, and the heat accumulation caused by continuous avalanche is reduced; The step analyzes the causal relationship between avalanche breakdown and transient temperature rise. The reason is that transient temperature rise can be caused by multiple factors, while avalanche breakdown is the most risky and special cause. If the transient temperature rise is caused by avalanche breakdown, the essence is the transient high power loss caused by voltage peak, which needs to be targeted to suppress avalanche breakdown itself, rather than simply enhancing heat dissipation. If the transient temperature rise is caused by other factors, the heat dissipation path needs to be optimized, rather than adjusting the circuit parameters. If the causal judgment is not made, the wrong heat management strategy may be adopted (such as using heat dissipation optimization to deal with the transient temperature rise caused by avalanche breakdown), which not only cannot solve the problem, but also wastes resources. Step S4: After implementing the avalanche breakdown protection optimization, the transient heat conduction path of the transient temperature rise to the steady-state region is predicted by the thermal coupling model, the steady-state region that is heated by the transient heat conduction of the transient temperature rise region is marked as the affected region, and the temperature changes of the transient temperature rise region and the affected region before and after optimization are analyzed to evaluate the optimization effect. In some embodiments, based on the three-dimensional structure model of the SiC device, a transient thermal coupling model is constructed, the optimized SiC device operating parameters and environmental parameters are input, and the transient temperature field, heat flux density and conduction path, and temperature change rate are output. The operating parameters at least include gate drive resistance, switching frequency, voltage and current waveform (reflecting the electrical state after avalanche breakdown protection optimization). The environmental parameters at least include environmental temperature, cooling system parameters (such as liquid cooling flow), thermal conductivity, specific heat capacity and density of each material. As understood by those skilled in the art, the transient thermal coupling model is a dynamic simulation model that integrates device physical structure, thermal conduction characteristics and electro-thermal interaction. The transient thermal coupling model works by dynamically simulating the transient heat conduction process to predict how the heat of the transient temperature rise region spreads to the steady-state region after the avalanche breakdown protection optimization, providing quantitative data support for extracting the heat conduction path and marking the affected region. It more realistically reflects the actual impact of avalanche breakdown protection optimization on the overall thermal management of the device. The transient temperature field distribution at m (several) time points after optimization is obtained by thermal coupling model simulation; where m is set by those skilled in the art based on experience. The temperature field data includes all grid regions on the surface of the SiC device; the temperature value, temperature change rate and heat flux density of each grid region at different time points are recorded; where the heat flux density reflects the heat transfer intensity. The extraction process of the diffusion path is: taking the transient temperature rise region as the starting point, calculating the heat flow direction of each grid region, where the heat flow direction is obtained based on the temperature gradient, and the heat flow conducts from the high temperature region to the low temperature region, and the direction is determined by the direction of the gradient vector. Along the heat flow direction, screen the grid nodes with heat flux density greater than the heat flux density threshold (such as 0.5 W / mm², set according to the heat dissipation capacity of the device) to form a continuous heat conduction path; Extract the heat flow from the transient heating area to the steady heating area marked in the foregoing step S1; Based on the heat conduction path and the temperature change, mark the steady area heated by transient heat conduction as an affected area; For the transient heating area and the affected area, calculate the temperature change before and after optimization, evaluate the optimization effect, and the process is: For the transient heating area, obtain the highest temperature value in all transient heating areas before optimization and the highest temperature value in all transient heating areas after optimization, and perform difference calculation, and then perform ratio calculation of the difference and the highest temperature value in all transient heating areas before optimization to obtain the highest temperature reduction ratio; For the affected area, obtain the area of the affected area before optimization and the area of the affected area after optimization, and perform difference calculation, and then perform ratio calculation of the difference and the area of the affected area before optimization to obtain the affected area reduction ratio; Among them, the affected area before optimization refers to the area of the steady state area heated by the transient heating area; The calculation of the affected area reduction ratio serves to: first, reflect the contraction degree of the heat conduction path, the higher the area reduction ratio, the more effective the optimization in inhibiting heat diffusion; second, the area of the affected area is related to the SiC failure probability, according to the failure physical model, the steady state area affected by the transient heat conduction for a long time will accelerate the material aging (such as gate oxide layer degradation, metallization layer migration), the area reduction ratio can be used as an input parameter to predict the remaining life of the device: the higher the reduction ratio, the slower the aging rate, and the more significant the reliability improvement, providing data support for the maintenance period and life evaluation of the rectifier; third, if the affected area reduction ratio is low, it means that the existing heat dissipation structure (such as liquid cooling channel layout, thermoelectric refrigeration module position) may have design defects (such as not covering the main heat conduction path); Weighted fusion of the highest temperature ratio and the affected area reduction ratio is performed to output a comprehensive optimization coefficient; Among them, the weight coefficients of the highest temperature ratio and the affected area reduction ratio are set by those skilled in the art according to the SiC device failure risk, if the transient high temperature is the main failure inducement, the weight coefficient of the highest temperature ratio is 0.6-0.7, and if the large-area overheating caused by heat diffusion is the key inducement, the weight coefficient of the affected area reduction ratio is 0.6-0.7; The effect of evaluating the optimization effect by fusing the maximum temperature ratio with the affected area reduction ratio lies in: firstly, the fusing can more comprehensively evaluate the inhibition effect of the optimization strategy on thermal failure; secondly, the deficiencies of the optimization strategy can be determined to provide a direction for subsequent iterative optimization and reduce trial and error; If the comprehensive optimization coefficient is greater than or equal to the comprehensive optimization coefficient threshold, it is determined that the optimization is effective; if the comprehensive optimization coefficient is less than the comprehensive optimization coefficient threshold, it is determined that the optimization is ineffective, and iterative optimization is performed, that is, returning to step S3 to adjust the avalanche breakdown protection optimization strategy until the comprehensive optimization coefficient is greater than or equal to the comprehensive optimization coefficient threshold; The setting of the comprehensive optimization coefficient threshold is determined by a person skilled in the art in combination with the characteristics of the SiC device, the reliability target of the rectifier, the application scenario requirement and the experimental data verification, so that the threshold can effectively avoid the risk of thermal failure and also consider the feasibility of the optimization strategy. For example, different application fields (such as new energy vehicle charging, smart grid, aerospace) have different reliability requirements for rectifiers, and the threshold needs to meet the definition of the risk level of thermal failure in the industry standard. In the civil field (such as new energy vehicle charging pile), the average failure-free time (MTBF) of the device is usually required to be ≥10 5 hours, and the thermal failure probability is ≤0.1% / year. By statistically analyzing experimental data, the minimum value (such as 70%) of the comprehensive optimization coefficient that meets the MTBF is determined as the threshold. In the industrial or aerospace field: higher reliability (MTBF ≥10 6 hours) is required, and the thermal failure probability is ≤0.01% / year. The threshold needs to be increased to more than 80% to match the more stringent risk control target. The effect of this step lies in: firstly, by verifying the effectiveness of the protection optimization, it can be determined whether the avalanche breakdown protection optimization measure actually reduces the thermal shock and the impact on other grid regions, reducing the waste of resources caused by invalid optimization; secondly, through the evaluation process, the inhibition effect of the avalanche breakdown protection optimization on transient thermal shock and thermal diffusion can be quantified, ensuring that the thermal management strategy can effectively reduce the thermal failure risk of the SiC device and improve the stability of the rectifier; thirdly, through the thermal conduction path prediction, the affected area that still exists after optimization can be understood, providing an improvement direction for subsequent heat dissipation design. The present embodiment forms a closed-loop thermal management system by locating the thermal hazard area, determining the causal relationship between transient temperature rise and avalanche breakdown, implementing targeted protection optimization, and scientifically and quantitatively evaluating the optimization effect, solves the problem from the root, improves the thermal stability and reliability of the high-efficiency rectifier based on the SiC device, and promotes its wide application in the fields of new energy vehicles, smart grids and the like.

[0010] Embodiment 2 Based on the same inventive concept as the SiC device-based high-efficiency rectifier thermal management method in one of the foregoing embodiments, the present application provides a SiC device-based high-efficiency rectifier thermal management system, as shown in Figure 3 The system specifically includes: A temperature distribution analysis module: collects the temperature distribution of the SiC device in the high-efficiency rectifier under full load conditions, and obtains the transient heating area and the steady heating area by analyzing the range of temperature change; An execution process: under full load conditions, the temperature distribution of the SiC device is collected, the surface is divided into a grid format (the normal area is 2.4 mm x 2.4 mm, and the pin connection area and other heat concentration areas are encrypted as 0.8 mm x 0.8 mm), the temperature values of each area are obtained by setting the collection frequency, the temperature change rate of adjacent time is calculated, the transient heating area (the temperature change rate exceeds the limit value and the transient time proportion exceeds the threshold value) and the steady heating area are distinguished and marked in combination with the temperature change rate limit value and the transient time proportion limit value, and the mapping relationship between the temperature distribution and the three-dimensional model of the device is established; An avalanche breakdown analysis module: collects the electrical parameters of the SiC device, identifies whether the avalanche breakdown phenomenon occurs, and if so, analyzes the overlap degree of the avalanche breakdown phenomenon and the transient heating area based on the spatial position; An execution process: the electrical parameters (mainly voltage parameters) of the SiC device are collected, the overall voltage is obtained by connecting a detection circuit in parallel across the drain and source, and the local voltage is detected by setting a micro-voltage probe in the key area (such as the terminal edge and the JFET area) on the surface; after the overall voltage and the local voltage collected are filtered by using the moving average filter to remove high-frequency noise, the avalanche breakdown phenomenon is determined by using the global voltage and the local voltage in two dimensions; First, the overall voltage change rate (the ratio of the difference between the overall voltages of adjacent time and the time difference) is calculated, compared with the typical value, and if it is greater than the typical value, it is determined that the global avalanche phenomenon is triggered; after the global avalanche is determined, the voltage difference of adjacent micro-voltage probes is calculated to construct a voltage gradient vector, if the amplitude of the voltage gradient vector exceeds the threshold value and the direction points to the inside of the device, the local avalanche origin point is located, and the grid area with a thermal-electric coupling coefficient greater than a coupling coefficient threshold value is extracted as a candidate area of the avalanche breakdown source; the transient heating area is mapped to the surface coordinate system of the device, the thermal-electric coupling coefficient is calculated in combination with the local voltage at the time when the global avalanche occurs and the temperature value of the corresponding grid area, and the spatial overlap degree of the avalanche breakdown avalanche origin point, the candidate area, and the transient heating area is analyzed; An overlap judgment module: according to the spatial overlap degree, it is judged whether the transient heating is caused by the avalanche breakdown phenomenon, and if the transient heating is caused by the avalanche breakdown phenomenon, the avalanche breakdown protection optimization is triggered; Execution process: The spatial overlap ratio (the ratio of the overlapping area to the total area of ​​the transient region) of the avalanche breakdown-related region and the transient temperature rise region is weighted and fused with the thermal-electric coupling coefficient. If the spatial overlap ratio is greater than or equal to the threshold, the transient temperature rise is determined to be caused by avalanche breakdown, and protection optimization is triggered (such as dynamically adjusting the gate drive resistor to suppress voltage spikes and starting directional cooling to enhance heat dissipation in the overlapping region). If the spatial overlap ratio is less than the threshold, it is determined to be caused by other factors, and other thermal management strategies such as optimizing the heat dissipation structure are executed. Optimization effect evaluation module: After implementing avalanche breakdown protection optimization, the heat conduction path from transient temperature rise to steady state region is predicted through thermal coupling model. The steady state region that is heated due to transient heat conduction in the transient temperature rise region is marked as the affected region. The temperature changes of the transient temperature rise region and the affected region before and after optimization are analyzed to evaluate the optimization effect. Execution process: A transient thermal coupling model is constructed based on the three-dimensional structure of the SiC device. Optimized operating parameters and environmental parameters are input, and the transient temperature field distribution at m time points is obtained through simulation. The heat conduction path from the transient heating region to the steady-state region is extracted, and the steady-state region heated by transient heat conduction is marked as the affected region. The maximum temperature reduction ratio (the ratio of the temperature difference before and after transient region optimization to the maximum temperature before optimization) and the affected area reduction ratio (the ratio of the difference in affected area before and after optimization to the area before optimization) are calculated and weighted to form a comprehensive optimization coefficient. If the coefficient is greater than or equal to the threshold, the optimization is deemed effective; otherwise, the iterative adjustment strategy is returned. The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A SiC device based high efficiency rectifier thermal management method, characterized by: The method comprises the following steps: Collecting the temperature distribution of SiC devices in the high-efficiency rectifier under full load conditions, and obtaining the transient temperature rise area and the steady temperature rise area by analyzing the temperature change range; Collecting the global voltage and local voltage of the SiC device, determining whether a global avalanche phenomenon occurs by comparing the global voltage change rate with a typical value, if so, calculating the thermal-electric coupling coefficient by the local voltage and the temperature, extracting the avalanche breakdown source candidate grid area and locating the local avalanche origin point, and determining the specific position of the avalanche breakdown origin point; According to the thermal-electric coupling coefficient and the spatial overlap ratio, the spatial overlap degree is outputted, and it is judged whether the transient temperature rise is caused by the avalanche breakdown phenomenon, if the transient temperature rise is caused by the avalanche breakdown, the avalanche breakdown protection optimization is triggered; After implementing the avalanche breakdown protection optimization, the heat conduction path of the transient temperature rise area to the steady temperature rise area is predicted by the thermal coupling model, the steady temperature rise area which is heated by the transient heat conduction of the transient temperature rise area is marked as the affected area, the temperature changes of the transient temperature rise area and the affected area before and after optimization are analyzed, the comprehensive optimization coefficient is outputted, and the optimization effect is evaluated.

2. A high efficiency rectifier thermal management method for SiC based devices according to claim 1, characterized by: The process of obtaining the transient temperature rise area and the steady temperature rise area is: The surface of the SiC device is divided into several areas in a grid format, the temperature value of each area at the collection time is obtained, the temperature change rate corresponding to the adjacent collection time of each area is calculated, and the temperature rise time is obtained based on the temperature change rate; The temperature rise time with the temperature change rate greater than the temperature change rate limit value is regarded as the transient temperature rise, and the temperature rise time with the temperature change rate less than or equal to the temperature change rate limit value is regarded as the steady temperature rise; The ratio of the number of temperature rise times of the transient temperature rise to the total number of collection times is calculated as the transient temperature rise time ratio, if greater than the transient temperature rise time ratio, it is the transient high temperature area, and if less than or equal to the transient temperature rise time ratio, it is the steady temperature rise area.

3. A high efficiency rectifier thermal management method for SiC based devices according to claim 2, characterized by: The process of obtaining the temperature rise time is: During the collection period, for each area, the collection time with a positive temperature change rate is extracted as the temperature rise time.

4. The SiC device based high efficiency rectifier thermal management method of claim 1, wherein: The process of determining whether a global avalanche phenomenon occurs is: A global voltage is detected by a parallel detection circuit connected between the source and the drain of the SiC device, and a global voltage change rate is calculated, that is, the difference between the global voltages at adjacent collection times divided by the difference between the adjacent collection times; If the voltage change rate is greater than the typical value, it is determined that a global avalanche phenomenon is triggered.

5. The SiC device based high efficiency rectifier thermal management method of claim 1, wherein: The process of locating the local avalanche origin point is: A micro-voltage probe is arranged on the surface area of the SiC device to detect the local voltage, the voltage difference between adjacent micro-voltage probes is calculated, and a voltage gradient vector is constructed; The transient temperature rise area is mapped to the surface coordinate system of the SiC device; The occurrence time of the triggered global avalanche phenomenon is obtained, the local voltage of all micro-voltage probes and the temperature value of the corresponding grid area are extracted; The thermal-electric coupling coefficient is calculated, and the grid area with a coupling coefficient greater than the coupling coefficient threshold value is determined as the avalanche breakdown source candidate grid area; The voltage change values of all micro-voltage probes are sorted, and the grid where the micro-voltage probe with the largest voltage change value is located is regarded as the avalanche origin point.

6. A high efficiency rectifier thermal management method for SiC based devices as claimed in claim 1, wherein: The process of outputting the spatial overlap degree is An overlapping grid area total area is obtained by acquiring an avalanche breakdown related region and a transient temperature rise region, and a ratio of the overlapping grid area total area to a transient temperature rise region total area is calculated to obtain an overlapping area proportion; A thermal-electric coupling coefficient corresponding to the overlapping grid area total area is averaged to obtain a thermal-electric coupling coefficient average value; The overlapping area proportion and the thermal-electric coupling coefficient average value are fused to output a spatial overlap degree.

7. The SiC device based high efficiency rectifier thermal management method of claim 1, wherein: The process of determining whether the transient temperature rise is caused by the avalanche breakdown phenomenon is as follows: If the spatial overlap degree is greater than or equal to a spatial overlap degree threshold value, it is determined that the transient temperature rise is caused by the avalanche breakdown phenomenon, and an avalanche breakdown protection optimization process is triggered.

8. The SiC device based high efficiency rectifier thermal management method of claim 1, wherein: The process of obtaining the affected region is as follows: Based on a three-dimensional structure model of the SiC device, a transient thermal coupling model is constructed, and optimized SiC device operating parameters and environmental parameters are input to output a transient temperature field, a heat flux density, a conduction path, and a temperature change rate; The transient temperature field distribution at the optimized time points is obtained through thermal coupling model simulation; The heat flow direction of each grid area is calculated from the transient temperature rise region as a starting point; Along the heat flow direction, grid nodes with a heat flux density greater than a heat flux density threshold value are screened to form a continuous heat conduction path, and heat flow conduction from the transient temperature rise region to the steady temperature rise region is extracted; Based on the heat conduction path and the temperature change, the steady region that is heated due to transient heat conduction is marked as an affected region.

9. The SiC device based high efficiency rectifier thermal management method of claim 1, wherein: The process of evaluating the optimization effect is as follows: If the comprehensive optimization coefficient is greater than or equal to a comprehensive optimization coefficient threshold value, it is determined that the optimization is effective; if the comprehensive optimization coefficient is less than the comprehensive optimization coefficient threshold value, it is determined that the optimization is ineffective, and iterative optimization is performed, that is, the avalanche breakdown protection optimization strategy is returned to adjust until the comprehensive optimization coefficient is greater than or equal to the comprehensive optimization coefficient threshold value.

10. The SiC device based high efficiency rectifier thermal management method of claim 1, wherein: The process of obtaining the comprehensive optimization coefficient is as follows: For the transient temperature rise region, the highest temperature value in all transient temperature rise regions before optimization and the highest temperature value in all transient temperature rise regions after optimization are obtained, a difference value is calculated, and a ratio of the difference value to the highest temperature value in all transient temperature rise regions before optimization is calculated to obtain a highest temperature reduction ratio; For the affected region, the affected region area before optimization and the affected region area after optimization are obtained, a difference value is calculated, and a ratio of the difference value to the affected region area before optimization is calculated to obtain an affected area reduction ratio; The highest temperature ratio and the affected area reduction ratio are fused to output a comprehensive optimization coefficient.

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