An online junction temperature estimation and protection method and system for liquid-cooled power modules

Abstract

An online junction temperature estimation and protection method and system for liquid-cooled power modules, the method establishes a simplified thermal circuit model with the cooling liquid inlet temperature as the reference benchmark, calibrates a key "equivalent thermal resistance coefficient" through high-precision offline experiments, and then uses the easily measured temperature quantities (inlet water temperature and module NTC temperature) to achieve rapid estimation of the chip junction temperature with minimal calculation, and implement protection accordingly. The method and system make full use of existing sensors, without adding any hardware circuit, and can realize low-cost, high-time-efficiency junction temperature estimation, with greatly improved timeliness and reliability, and has wide universality.

Description

Technical Field

[0001] This invention relates to the field of power electronics and motor control technology, and in particular to an online junction temperature estimation and protection method and system for liquid-cooled power modules. Background Technology

[0002] With the increasing demands for power density and efficiency from electric vehicles and high-end industrial drive systems, motor controllers are evolving towards higher voltage, higher current, and higher frequency operation. Traditional silicon-based IGBTs, due to material limitations, are increasingly unable to meet the requirements in terms of switching losses and high-temperature performance. Wide-bandgap semiconductor devices such as silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs), with their superior performance, are gradually becoming the mainstream choice for high-power controllers.

[0003] However, devices such as SiC MOSFETs are extremely sensitive to their operating junction temperature. Although they can theoretically operate at higher temperatures, to ensure long-term reliability, the industry typically limits their maximum allowable junction temperature to between 175°C and 200°C. Once the junction temperature exceeds this limit, the device may experience irreversible rapid failure due to mechanisms such as accelerated gate oxide degradation and a sharp drop in channel mobility. Therefore, accurate and reliable junction temperature monitoring and protection of SiC power modules is a key technical bottleneck to ensure their safe operation and maximize their performance advantages.

[0004] Currently, the mainstream junction temperature monitoring and protection schemes mainly include the following categories, but all of them have significant drawbacks: 1. Temperature monitoring based on module-embedded negative temperature coefficient (NTC) thermistors: This is the most common method. However, NTC thermistors are typically sintered onto the metal substrate or heat sink of the power module, detecting the case temperature (T_case) or substrate temperature (T_ntc), rather than the junction temperature (T_j) of the power chip itself. Under drastically fluctuating loads, there is a huge dynamic temperature difference (up to tens of degrees Celsius) between the chip junction temperature and the case temperature. Monitoring only the case temperature will lead to severe delays, failing to capture junction temperature spikes in time. The junction temperature may have already exceeded limits and caused damage when the NTC temperature appears normal. This is the most significant drawback of existing technology.

[0005] 2. Online extraction method based on heat-sensitive electrical parameters: This method indirectly estimates the junction temperature by monitoring electrical parameters strongly correlated with junction temperature, such as on-state voltage drop Vds(on), threshold voltage, and turn-off voltage spikes. Although this type of method (often called the TSEP method) can get closer to the true junction temperature, the circuit design is complex, requiring additional precision sampling, injection, and isolation circuits, which increases the system cost and size. Moreover, the measurement is susceptible to parasitic parameters and electromagnetic interference, and its stability in complex automotive environments is challenged.

[0006] 3. Computational methods based on complex thermal network models or finite element analysis: This method establishes a detailed thermal model involving multiple layers of materials (chip, solder, substrate, heat sink), inputs power consumption and cooling boundary conditions, and calculates the junction temperature in real time. While theoretically accurate, this method is computationally intensive and heavily relies on thermal model parameters (such as thermal resistance and thermal capacity of each layer), which are difficult to obtain accurately and age over time. Although research has focused on improving computational efficiency, it remains difficult to apply in low-cost embedded controllers with high real-time performance requirements.

[0007] The table below compares the limitations of existing major technical solutions:

[0008] In conclusion, existing technologies cannot achieve a good balance between real-time performance, accuracy, ease of engineering, and cost. Summary of the Invention

[0009] In view of the shortcomings of the prior art, this disclosure provides an online junction temperature estimation and protection method and system for liquid-cooled power modules, which can realize online junction temperature estimation and reliable protection with minimal computational overhead by utilizing existing low-cost sensors. It is applicable to liquid-cooled power modules in automotive-grade or industrial-grade motor controllers that adopt liquid cooling (such as water cooling) heat dissipation methods, including silicon carbide (SiC) power modules, as well as other types of power modules, such as insulated gate bipolar transistor (IGBT) modules.

[0010] The core purpose of this disclosure is: Without adding extra hardware circuitry and costs, the junction temperature of the power chip can be quickly and effectively estimated online using only the existing NTC sensor in the power module and the inlet water temperature sensor of the cooling system. Construct a dual protection logic that integrates "junction temperature estimation" and "temperature difference monitoring" to improve the reliability and robustness of the protection system; A standardized offline thermal resistance coefficient calibration process is established, enabling this method to be accurately adapted to different types of SiC (including SiCMOSFET) or IGBT power modules, thus possessing versatility and mass production capability.

[0011] The overall approach is as follows: A simplified thermal path model with the coolant inlet temperature as a reference is established. A key "equivalent thermal resistance coefficient" is calibrated through high-precision offline experiments. Then, the chip junction temperature is quickly estimated online with minimal computation using easily measurable temperature parameters (inlet water temperature and module NTC temperature), and protection is implemented accordingly.

[0012] Specifically, the online junction temperature estimation and protection method for liquid-cooled power modules provided in this disclosure includes the following steps: S1. Establish a simplified thermal circuit model with the coolant inlet temperature as the reference. S2, the "equivalent thermal resistance coefficient" is calibrated through high-precision offline experiments; S3 collects the inlet temperature of the coolant and the NTC temperature of the power module in real time, quickly estimates the chip junction temperature, and implements protection accordingly.

[0013] Furthermore, the model described in step S1 is: Using the coolant inlet temperature as a unified and stable temperature reference point for the entire heat dissipation path, the total thermal pressure drop of the liquid junction is characterized by the difference ΔT between the NTC temperature of the hottest spot of the power module and the coolant inlet temperature, and a lumped coefficient, i.e., the equivalent thermal resistance coefficient K. The highest junction temperature of the chip is expressed as:

[0014] Among them, T cool_in This refers to the inlet temperature of the coolant.

[0015] Furthermore, step S2 specifically includes: Experimental preparation: Use a dedicated sample of the power module model to be calibrated. The sample should have an infrared observation window or an openable cover design to ensure that the infrared thermal imager can directly observe the chip surface. Setting up a test platform: Install the power module in a controllable liquid cooling system. The system must be able to accurately set and record the inlet water temperature T. cool_in Apply a controllable DC or pulsed current I to the power module. load Simulates different power losses; synchronously and with high precision, acquires the temperature T of all NTC devices. ntc ; Steady-state data acquisition: in multiple locations with different (T) cool_in , I load The combined steady-state operating points were tested, and at each steady-state point, after ensuring thermal equilibrium, the results were recorded synchronously. Setting value T cool_in ; The highest measured temperature of NTC was T. ntc_max ; The highest junction temperature T of the chip was directly read by an infrared thermal imager. j_actual , as a reference for "truth value"; Data processing and fitting: Collecting sufficient data points (T cool_in , T ntc_max , T j_actual According to the core thermal model formula constructed in step S1: T j_actual = T cool_in + K * (T ntc_max - T cool_inThe optimal equivalent thermal resistance coefficient K is obtained by fitting the data.

[0016] Furthermore, step S3 specifically includes: Data Acquisition and Preprocessing: Real-time acquisition of coolant inlet temperature T cool_in And all NTC temperatures; calculate the maximum value T of all available NTC temperature values. ntc_max ; Core calculation: Calculate the temperature difference ΔT = T ntc_max - T cool_in Subsequently, the coefficient K obtained from offline calibration is used to calculate the online estimated junction temperature:

[0017] Threshold protection decision: Main protection based on model estimation: when T j_est ≥ Preset junction temperature protection threshold T j_th The protection will be triggered immediately upon activation. Furthermore, the threshold protection decision in step S3 also includes: Auxiliary protection based on direct measurement: When ΔT ≥ preset temperature difference threshold ΔT th At the same time, protection is also triggered; where ΔT th The ΔT setting is based on the typical value of the junction temperature when it is close to the maximum allowable junction temperature in the calibration data.

[0018] An online junction temperature estimation and protection system for liquid-cooled power modules, applying the above method, mainly includes: Inlet liquid temperature sensor: Installed at the inlet of the power module cooling channel to measure the inlet temperature of the coolant in real time; Built-in NTC sensor: The NTC integrated inside the power module is used to monitor the temperature of the module substrate; Microcontroller unit: Used to acquire the temperature values ​​of the inlet liquid temperature sensor and the NTC in the module, and to execute the chip junction temperature fast estimation and protection logic.

[0019] Compared with the prior art, the beneficial effects of this disclosure are: ① to achieve low-cost and high-time-efficiency junction temperature estimation: fully utilize existing sensors, without adding any hardware circuits, the online calculation is only one subtraction and one multiplication, the computational overhead is minimal, and it can run in real time on any microcontroller; ② The timeliness and reliability of protection are greatly improved: Compared with only monitoring the NTC temperature, this method can reflect the junction temperature change trend earlier through model calculation. The dual protection strategy constitutes a more complete safety defense line. ③ Possesses engineering-acceptable accuracy and mass production capability: Through standardized offline infrared calibration, thermal model parameters are "tailor-made" for each module model, effectively compensating for individual differences, so that the online estimation results have practical accuracy and are suitable for large-scale mass production; ④ High versatility: This method does not depend on the physical characteristics of specific devices and can be seamlessly transferred to various high-power power electronic devices that use liquid cooling, such as on-board chargers and DC-DC converters. Attached Figure Description

[0020] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments of this disclosure taken in conjunction with the accompanying drawings, in which the same reference numerals generally represent the same components.

[0021] Figure 1 The following is a system architecture and flowchart for online junction temperature estimation and protection based on this disclosure. Detailed Implementation

[0022] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0023] This disclosure provides a method and system for online junction temperature estimation and protection of liquid-cooled power modules. The overall idea is as follows: establish a simplified thermal path model with the coolant inlet temperature as a reference, calibrate a key "equivalent thermal resistance coefficient" through high-precision offline experiments, and then use easily measurable temperature parameters (inlet water temperature and module NTC temperature) online to quickly estimate the chip junction temperature with minimal computation, and implement protection accordingly.

[0024] In one exemplary implementation: According to the present disclosure, an online junction temperature estimation and protection system for a liquid-cooled power module is as follows: Figure 1 As shown. The required hardware consists of standard components for modern liquid-cooled motor controllers, requiring no additional circuitry. ① Inlet water temperature sensor: Installed at the inlet of the power module cooling channel to measure the inlet temperature T of the coolant in real time. cool_in .

[0025] ② Built-in NTC sensor: The power module has an integrated NTC sensor for monitoring the module substrate temperature. The controller collects all available NTC temperature values ​​(such as T). ntc_u , T ntc_v , Tntc_w ).

[0026] ③ Microcontroller unit: responsible for executing algorithms and protection logic.

[0027] Core algorithm flow: (1) Offline calibration of equivalent thermal resistance coefficient K (key preprocessing) Accurate acquisition of coefficient K is fundamental to ensuring the accuracy of online estimation, and its standardized process is as follows: Experimental preparation: Use a dedicated sample of the power module (such as a three-phase full-bridge SiC module) of the model to be calibrated. The sample should have an infrared observation window or an openable cover design to ensure that the infrared thermal imager can directly observe the chip surface.

[0028] Setting up a test platform: Install the module on a controllable liquid cooling system. The system must be able to accurately set and record the inlet water temperature T. cool_in A controllable DC or pulsed current is applied to the module to simulate different power losses. The temperature of all NTC devices is simultaneously and accurately acquired. ntc .

[0029] Steady-state data acquisition: in multiple locations with different (T) cool_in , I load The combined steady-state operating points were tested. At each steady-state point, after ensuring thermal equilibrium, the results were recorded synchronously. T cool_in (Settings) T ntc_max (Measured highest temperature of NTC) T j_actual (The highest junction temperature of the chip, directly read by an infrared thermal imager, is used as a "true value" reference).

[0030] Data processing and fitting: Collecting sufficient data points (T cool_in , T ntc_max , T j_actual According to the core thermal model formula of the present invention: T j_actual =T cool_in + K * (T ntc_max - T cool_in Using mathematical methods such as linear regression, the optimal equivalent thermal resistance coefficient K is fitted. This K value encapsulates the complex heat transfer characteristics from the chip junction to the coolant inlet and will be stored as a fixed parameter in the software of the mass production controller for this module model.

[0031] Online real-time junction temperature estimation and protection The online process is extremely simple and suitable for high-speed operation in microcontrollers: 1) Data Acquisition and Preprocessing: Real-time acquisition of coolant inlet temperature T cool_inAnd all NTC temperatures. Calculate T ntc_max = max(T ntc_u , T ntc_v , T ntc_w Choosing the maximum value is based on the worst-case design principle and aims to protect the hottest chip in the module.

[0032] 2) Core calculation: Calculate the temperature difference ΔT = T ntc_max -T cool_in Subsequently, the coefficients K obtained from offline calibration are called, and one multiplication and one addition operation are performed to obtain the online estimated junction temperature:

[0033] The physical meaning of this formula is: based on the coolant inlet temperature, plus the equivalent temperature rise caused by power loss, after being adjusted by the coefficient K.

[0034] 3) Dual threshold protection decision: Main protection (based on model estimation): when T j_est ≥ Preset junction temperature protection threshold T j_th (For example, 165°C, which is the maximum junction temperature margin) will trigger protection immediately.

[0035] Auxiliary protection (based on direct measurement): Simultaneously, when ΔT ≥ preset temperature difference threshold ΔT j_th At that time, protection is also triggered. ΔT j_th It can be set based on the typical ΔT value near the maximum allowable junction temperature in the calibration data. This path serves as redundancy and a safety backup, providing direct protection against temperature anomalies when model estimates deviate due to extreme conditions.

[0036] The key technical point in this embodiment is: 1. Simplified thermal circuit model based on "inlet water temperature reference + single ΔT" The core concept of this embodiment is to abandon the complex multi-layer dynamic thermal network and innovatively propose using the coolant inlet temperature as a unified and stable temperature reference point for the entire heat dissipation path. The total thermal pressure drop to the liquid junction is characterized by an easily measurable key temperature difference ΔT (the difference between the module's hottest NTC temperature and the inlet water temperature) and a lumped coefficient K, laying the foundation for extremely low online computational cost.

[0037] 2. Offline coefficient calibration method based on direct measurement by infrared thermal imager This is key to simplifying the model for engineering and ensuring accuracy. This embodiment proposes a standardized offline calibration process: directly measuring the junction temperature of the actual chip using an infrared thermal imager, synchronously correlating it with the inlet water temperature and NTC temperature, and then using regression analysis to fit a unique equivalent thermal resistance coefficient K. This method is direct and objective, "encapsulating" the complex manufacturing tolerances and thermal coupling within the module in the calibration value.

[0038] 3. Dual Temperature Inputs and Maximization Selection Logic The online algorithm requires only two standard temperature signals and uses the maximum NTC temperature value, ensuring that the protection targets the weakest point and improving safety.

[0039] 4. Construction of a dual threshold protection strategy Two parallel and independent protection paths are proposed and protected: "estimated junction temperature exceeding the limit" and "direct temperature difference exceeding the limit". The former is an active and predictive protection; the latter is a passive safety redundancy based on direct measurement. The combination of the two significantly improves system reliability.

[0040] 5. Universality of the solution This method is universally applicable, not only to three-phase full-bridge power modules, but also, by adjusting the NTC selection logic (e.g., selecting only one or two NTCs), to other topologies such as half-bridge modules and single-transistor modules. The calibration method makes it inherently applicable to power devices made of various semiconductor materials such as SiC MOSFETs, IGBTs, and GaN HEMTs.

[0041] The above technical solutions are merely exemplary embodiments of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the specific embodiments of the present invention. Therefore, the methods described above are merely preferred and not restrictive.

Claims

1. A method for online junction temperature estimation and protection of liquid-cooled power modules, characterized in that, Includes the following steps: S1. Establish a simplified thermal circuit model with the coolant inlet temperature as the reference. S2, the "equivalent thermal resistance coefficient" is calibrated through high-precision offline experiments; S3 collects the inlet temperature of the coolant and the NTC temperature of the power module in real time, quickly estimates the chip junction temperature, and implements protection accordingly.

2. The method according to claim 1, characterized in that, The model mentioned in step S1 is: Using the coolant inlet temperature as a unified and stable temperature reference point for the entire heat dissipation path, the total thermal pressure drop of the liquid junction is characterized by the difference ΔT between the NTC temperature of the hottest spot of the power module and the coolant inlet temperature, and a lumped coefficient, i.e., the equivalent thermal resistance coefficient K. The highest junction temperature of the chip is expressed as: Among them, T cool_in This refers to the inlet temperature of the coolant.

3. The method according to claim 2, characterized in that, Step S2 specifically includes: Experimental preparation: Use a dedicated sample of the power module model to be calibrated. The sample should have an infrared observation window or an openable cover design to ensure that the infrared thermal imager can directly observe the chip surface. Setting up a test platform: Install the power module in a controllable liquid cooling system. The system must be able to accurately set and record the inlet water temperature T. cool_in Apply a controllable DC or pulsed current I to the power module. load Simulates different power losses; synchronously and with high precision, acquires the temperature T of all NTC devices. ntc ; Steady-state data acquisition: in multiple locations with different (T) cool_in , I load The combined steady-state operating points were tested, and at each steady-state point, after ensuring thermal equilibrium, the results were recorded synchronously. Setting value T cool_in ; The highest measured temperature of NTC was T. ntc_max ; The highest junction temperature T of the chip was directly read by an infrared thermal imager. j_actual , as a reference for "truth value"; Data processing and fitting: Collecting sufficient data points (T cool_in , T ntc_max , T j_actual According to the core thermal model formula constructed in step S1: T j_actual = T cool_in + K * (T ntc_max - T cool_in The optimal equivalent thermal resistance coefficient K is obtained by fitting the data.

4. The method according to claim 2 or 3, characterized in that, Step S3 specifically includes: Data Acquisition and Preprocessing: Real-time acquisition of coolant inlet temperature T cool_in And all NTC temperatures; calculate the maximum value T of all available NTC temperature values. ntc_max ; Core calculation: Calculate the temperature difference ΔT = T ntc_max - T cool_in Subsequently, the coefficient K obtained from offline calibration is used to calculate the online estimated junction temperature: Threshold protection decision: Main protection based on model estimation: when T j_est ≥ Preset junction temperature protection threshold T j_th When this happens, protection is immediately triggered.

5. The method according to claim 4, characterized in that, The threshold protection decision in step S3 also includes: Auxiliary protection based on direct measurement: When ΔT ≥ preset temperature difference threshold ΔT th At the same time, protection is also triggered; where ΔT th The ΔT setting is based on the typical value of the junction temperature when it is close to the maximum allowable junction temperature in the calibration data.

6. An online junction temperature estimation and protection system for a liquid-cooled power module using the method described in any one of claims 1-5, characterized in that, include: Inlet liquid temperature sensor: Installed at the inlet of the power module cooling channel to measure the inlet temperature of the coolant in real time; Built-in NTC sensor: The NTC integrated inside the power module is used to monitor the temperature of the module substrate; Microcontroller unit: Used to acquire the temperature values ​​of the inlet liquid temperature sensor and the NTC in the module, and to execute the chip junction temperature fast estimation and protection logic.

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