A mixer device conduction mode threshold adaptive adjustment method based on temperature feedback

Abstract

The application discloses a kind of hybrid device conduction mode threshold self-adaptive adjustment method based on temperature feedback, belong to new energy automobile inverter technical field.The present application includes sampling, temperature of SIC MOSFET and temperature of IGBT are calculated in turn, the inflection point voltage of SIC MOSFET conduction resistance resistance and IGBT is calculated, switching current threshold is obtained, finally, switching of switch element conduction mode according to established rule.The present application dynamically adjusts switching current threshold I knee , so that under high temperature condition, hybrid power device can enter by conduction mode 2 under lower load current, and IGBT can effectively share the thermal load of SIC MOSFET.This method realizes the dynamic balance of heat distribution between devices, reduces the thermal stress of SIC MOSFET, while ensuring the thermal reliability of the system without increasing overall power loss.

Description

Technical Field

[0001] This invention relates to the field of inverter technology for new energy vehicles, and provides a method for adaptive adjustment of the conduction mode threshold of hybrid devices based on temperature feedback. It is applicable to the performance optimization requirements of SiC MOSFET / IGBT hybrid devices under dynamic loads. Background Technology

[0002] With the rapid development of new energy power generation, electric vehicle drive systems, and industrial frequency conversion equipment, the market demand for power semiconductor solutions that combine high-frequency switching capabilities, high-voltage and high-current handling capabilities, and cost-effectiveness is becoming increasingly urgent. IGBTs and SiC MOSFETs connected in parallel form hybrid devices, aiming to achieve a breakthrough in technical and economic efficiency by optimizing device synergy: the IGBT handles steady-state high current, reducing losses with its low on-state voltage drop, while the SiC MOSFET is responsible for high-frequency switching, improving system efficiency with its low switching losses. By rationally designing the conduction mode, the load-carrying capacity of the SiC MOSFET can be improved while reducing the switching losses of the IGBT. However, this hybrid device suffers from uneven heat distribution. Although the thermal conductivity of SiC material is much higher than that of Si material, the area of ​​the SiC MOSFET chip is generally smaller than that of the IGBT, resulting in higher heat flux density and increased thermal resistance. Therefore, the heat dissipation capacity of the SiC MOSFET is usually weaker than that of the IGBT. Switching losses are concentrated on the SiC MOSFET, causing its temperature to be much higher than that of the IGBT, which can easily damage the SiC MOSFET.

[0003] Currently, several papers have proposed solutions to the problem of uneven heat distribution in hybrid switching causing damage to SiC MOSFETs due to temperature fluctuations. The approach involves dynamically adjusting the switching loss distribution to transfer the switching losses originally borne by the SiC MOSFET to the IGBT, thereby achieving a more uniform heat distribution. For example: The article, titled "Active Gate Delay Time Control of Si / SiC Hybrid Switch for Junction Temperature Balance Over a Wide Power Range," by Zongjian Li, Jun Wang, Linfeng Deng, Zhizhi He, Xin Yang, and Bing Ji, published in *IEEE Transactions on Power Electronics*, May 2020, Vol. 35, No. 5, pp. 5354-5365, describes a method that uses a PID controller to dynamically adjust the turn-off delay based on the junction temperature difference of the device to redistribute losses and maintain thermal balance over a wide power range. However, this method has significant drawbacks: first, the control accuracy is highly dependent on the mathematical model, and parameter drift caused by device aging or process deviations can lead to model inaccuracies; second, the complex real-time iterative calculations place extremely high demands on the chip's computing power, increasing hardware costs; and third, the indirect estimation based on case temperature suffers from thermal hysteresis, making it difficult to effectively cope with rapid load transients.

[0004] The article, titled "Adaptive Gate Delay-Time Control of Si / SiC Hybrid Switch for Efficiency Improvement in Inverters," by Zishun Peng, Jun Wang, Zeng Liu, Zongjian Li, Daming Wang, and Yuxing Dai, published in *IEEE Transactions on Power Electronics*, March 2021, Vol. 36, No. 3, pp. 3437-3449, improves junction temperature balance by adjusting gate delay, but has significant drawbacks: first, it relies excessively on thermal resistance model parameters, failing to adapt to parameter drift caused by device aging and process variations; second, it is based on a steady-state model, lacking closed-loop regulation capability to cope with load transients; and third, it relies on case temperature detection and complex loss calculations, increasing system computing power and hardware costs.

[0005] The article, titled "A Comprehensive Thermal Management Method for Si / SiC Hybrid Devices Based on Coordinated Control of SiC On-State Ratio and Switching Frequency," by Han Shuo, Tu Chunming, Long Liu, Xiao Fan, Xiao Biao, and Guo Qi, published in the *Proceedings of the Chinese Society for Electrical Engineering*, 2024, Vol. 45, No. 13, pp. 5241-5255, describes a method that controls switching losses by adjusting the switching frequency and simultaneously adjusts the on-state ratio of SiC MOSFETs to transfer conduction losses, thus achieving coordinated smoothing of junction temperature fluctuations. However, this method requires interpolation using a three-dimensional lookup table to calculate the junction temperature, placing high demands on the controller's storage space and computing power. Furthermore, it does not describe the real-time performance on low-end MCUs, limiting its application in low-cost systems.

[0006] The article titled "Research on Drive Circuit for Junction Temperature Balance Based on Silicon / Silicon Carbide Hybrid Parallel Devices" by Tan Lingqi, Wu Yiding, Chen Zhiqiao, et al., *Journal of Power Supply*, October 22, 2025, and "Active Temperature Control of Si / SiC Hybrid Parallel Structure" by Yin Geng, He Zhizhi, Li Zongjian, et al., *Journal of Power Supply*, May 2021, Vol. 19, No. 3, pp. 3-19, addresses the junction temperature imbalance problem by employing either "fixed timing control" or "closed-loop control based on thermal models." However, both methods have significant drawbacks: the former relies on offline testing to set a fixed drive delay, making it unable to adapt to load fluctuations and changes in operating conditions, lacking dynamic adjustment capabilities; the latter, although introducing a loss model and case temperature feedback, suffers from severe thermal hysteresis due to its indirect temperature measurement method, failing to respond promptly to transient thermal shocks.

[0007] In summary, the following problems still exist in the existing technology: 1. Lack of dynamic adaptability and limited flexibility: Some technologies (such as fixed timing control and steady-state model-based methods) use fixed control parameters or are designed only for steady-state conditions. They cannot be dynamically adjusted according to load fluctuations or real-time changes in operating conditions, resulting in poor control performance in wide power ranges or variable load scenarios.

[0008] 2. Strong model dependence and parameter drift: Most existing technologies rely heavily on accurate mathematical models or thermal resistance models. However, due to factors such as device aging and process variations, the on-resistance of SiC MOSFETs can vary. Drift can occur, causing the preset model to become inaccurate, which in turn affects control accuracy and lacks the ability to adapt to parameter changes. Summary of the Invention

[0009] The technical problems to be solved by this invention include the uneven heat distribution of hybrid power devices under dynamic load conditions, and the technical challenges of thermal stress concentration, decreased reliability, and even device failure caused by the significantly higher junction temperature of SiC MOSFETs compared to IGBTs. Specifically, this invention provides a method for adaptive adjustment of the conduction mode threshold of hybrid devices based on temperature feedback. This method comprehensively considers the on-resistance value of the SiC MOSFET.R ds With IGBT inflection point voltage V f Both modes exhibit characteristics that change in real time with junction temperature. The current switching threshold between conduction mode 1 and conduction mode 2 is dynamically adjusted. I knee This method enables hybrid power devices to preferentially enter conduction mode 2 under lower load currents at high temperatures, and allows the IGBT to effectively share the thermal load of the SiC MOSFET. This achieves dynamic equilibrium of heat distribution between devices, reduces the thermal stress on the SiC MOSFET, and does not increase overall power loss while ensuring system thermal reliability.

[0010] The technical solution of the present invention is as follows.

[0011] An adaptive adjustment method for the conduction mode threshold of a hybrid device based on temperature feedback, wherein the circuit involved in the adjustment method comprises a switching element and a load connected in series. The circuit consists of a ground loop, where the switching element is a hybrid device composed of a SiC MOSFET and an IGBT; the adjustment method, under scenarios with continuously changing loads, adjusts based on the current temperature and the on-resistance value of the SiC MOSFET. and the inflection point voltage of IGBT The conduction mode of the switching element is adjusted in real time according to the switching cycle; any switching cycle in which the switching element operates is recorded as the current switching cycle, and the adjustment steps for the current switching cycle are as follows: Step 1: Sample the current flowing through the SiC MOSFET I MOS Current flowing through the IGBT I IGBT Voltage drop across the hybrid device The instantaneous power loss of the SiC MOSFET was calculated. and the instantaneous loss of IGBT ; Step 2: Calculate the temperature of the SiC MOSFET in the circuit. With the temperature of IGBT ; Step 3, based on the temperature of the SiC MOSFET and the temperature of IGBT The on-resistance of the SiC MOSFET was calculated. and the inflection point voltage of IGBT ; Step 4, based on the on-resistance value of the SiC MOSFET and the inflection point voltage of IGBT The switching current threshold of the conduction mode is calculated. , ; Step 5, when the load Changes cause load current in the circuit During fluctuations, the switching mode of the switching element is switched according to the following rules: If Then the control switching element switches to conduction mode 1, and its switching state is that only the SiC MOSFET is turned on; if If the switching element is switched to conduction mode 2, its switching state is IGBT conduction, and the SiC MOSFET is turned off after the IGBT conduction.

[0012] Preferably, the instantaneous power loss of the SiC MOSFET in step 1 and the instantaneous loss of IGBT The formula for calculation is: ; .

[0013] Preferably, the temperature of the SiC MOSFET in step 2 With the temperature of IGBT The formula for calculation is: ; ; in, Indicates ambient temperature. This indicates the thermal resistance from the SiC MOSFET junction to the environment. This indicates the thermal resistance between the IGBT junction and the environment. Indicates the heat capacity of a SiC MOSFET. Indicates the heat capacity of the IGBT. This indicates the temperature of the SiC MOSFET at the end of the previous switching cycle. This indicates the temperature of the IGBT at the end of the previous switching cycle. This indicates the duration of a switching cycle from heating to cooling.

[0014] Preferably, the on-resistance of the SiC MOSFET in step 3 is... and the inflection point voltage of IGBT The calculation formulas are as follows: ; ; in, To be in harmony with ambient temperature The corresponding SiC MOSFET on-resistance value,A The on-resistance value of the SiC MOSFET Fitting coefficients as a function of temperature To be in harmony with ambient temperature The corresponding IGBT inflection point voltage, B The inflection point voltage of the IGBT Fitting coefficients as a function of temperature.

[0015] Compared with existing methods that determine turn-on and turn-off delay times and switching frequencies based on load current, the advantages of this invention are as follows: 1. It achieves dynamic and balanced distribution of thermal stress in hybrid devices, significantly improving the reliability of the system under high dynamic loads.

[0016] This invention calculates the junction temperature of the SiC MOSFET and IGBT in real time and dynamically updates the on-resistance of the SiC MOSFET based on the temperature. and the inflection point voltage of IGBT This adaptively adjusts the switching threshold current between conduction mode one and conduction mode two. Under high temperature or heavy load conditions, this method enables the system to preferentially enter conduction mode two at lower load currents, prompting the IGBT to share the current of the SiC MOSFET earlier. I MOS This effectively solves the overheating problem caused by the small chip area and high thermal resistance of SiC MOSFETs, avoids thermal stress concentration, and prevents device failure due to local overheating without increasing overall losses.

[0017] 2. It overcomes the limitations of traditional fixed parameter control and improves the control strategy's adaptability and response speed to device parameter drift.

[0018] Unlike existing technologies that rely on offline test data or fixed thermal resistance models, this invention employs a thermal capacity method incorporating SiC MOSFETs. and the heat capacity of IGBT A transient temperature rise / fall mathematical model is developed, and the effect of temperature on the electrical parameters, including the on-resistance of the SiC MOSFET, is fed back in real time. and the inflection point voltage of IGBT This closed-loop feedback mechanism effectively compensates for parameter drift caused by device aging, manufacturing process deviations, or changes in ambient temperature. Furthermore, by calculating electrical parameters instead of using external sensors for temperature measurement, it eliminates detection lag caused by heat conduction, enabling rapid response to rapidly changing load transients without requiring additional temperature detection hardware, thus balancing low cost and high performance. Attached Figure Description

[0019] Figure 1 This is a flowchart of the present invention.

[0020] Figure 2 This is a control diagram for the present invention.

[0021] Figure 3 This is a comparison chart of the junction temperature of the hybrid device under existing conduction strategies and the conduction strategy of the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] Figure 2 This is a control diagram of the present invention, which also shows the circuit topology involved in the present invention. As can be seen from the diagram, the circuit involved in the adjustment method of the present invention consists of a switching element and a load connected in series. The circuit consists of a ground circuit, in which the switching element is a hybrid device composed of SiC MOSFETs and IGBTs.

[0024] exist Figure 2 On, load It is an adjustable resistor. V dc This is a DC voltage. In this embodiment, V dc It is 500V and has a switching frequency of 10K.

[0025] Figure 1 This is a flowchart of the present invention. Figure 1 and Figure 2 As can be seen, the present invention provides a method for adaptive adjustment of the conduction mode threshold of a hybrid device based on temperature feedback. The circuit involved in this adjustment method consists of a switching element and a load connected in series. The circuit consists of a ground circuit, in which the switching element is a hybrid device composed of SiC MOSFETs and IGBTs.

[0026] The aforementioned adjustment method, under scenarios with continuously changing loads, adjusts the current temperature and the on-resistance of the SiC MOSFET. and the inflection point voltage of IGBT The conduction mode of the switching element is adjusted in real time according to the switching cycle; any switching cycle in which the switching element operates is recorded as the current switching cycle, and the adjustment steps for the current switching cycle are as follows: Step 1: Sample the current flowing through the SiC MOSFET I MOS Current flowing through the IGBT I IGBT Voltage drop across the hybrid device The instantaneous power loss of the SiC MOSFET was calculated. and the instantaneous loss of IGBT .

[0027] In this embodiment, the instantaneous power loss of the SiC MOSFET described in step 1 and the instantaneous loss of IGBT The formula for calculation is: ; .

[0028] Step 2: Calculate the temperature of the SiC MOSFET in the circuit. With the temperature of IGBT .

[0029] In this embodiment, the temperature of the SiC MOSFET With the temperature of IGBT The formula for calculation is: ; ; in, Indicates ambient temperature. This indicates the thermal resistance from the SiC MOSFET junction to the environment. This indicates the thermal resistance between the IGBT junction and the environment. Indicates the heat capacity of a SiC MOSFET. Indicates the heat capacity of the IGBT. This indicates the temperature of the SiC MOSFET at the end of the previous switching cycle. This indicates the temperature of the IGBT at the end of the previous switching cycle. This indicates the duration of a switching cycle from heating to cooling.

[0030] In this embodiment, considering actual application conditions, the influence of the heat sink and thermally conductive insulating pad on the heat conduction path is taken into account, and the following is adopted: =7°C / W, =0.001 J / K. Furthermore, based on the analysis of differences in device physical structure, the chip area of ​​an IGBT is typically 3 to 5 times that of a SiC MOSFET at the same voltage and current rating. A larger chip area means greater heat capacity and wider heat conduction channels. To truly reflect the improvement in heat dissipation capacity due to this physical characteristic, we take... =6°C / W, =0.00167 J / K, to demonstrate its superior transient thermal tolerance compared to SiC MOSFETs.

[0031] Step 3, based on the temperature of the SiC MOSFET and the temperature of IGBT The on-resistance of the SiC MOSFET was calculated. and the inflection point voltage of IGBT .

[0032] In this embodiment, the on-resistance of the SiC MOSFET and the inflection point voltage of IGBT The calculation formulas are as follows: ; ; in, To be in harmony with ambient temperature The corresponding SiC MOSFET on-resistance value, A The on-resistance value of the SiC MOSFET Fitting coefficients as a function of temperature To be in harmony with ambient temperature The corresponding IGBT inflection point voltage, B The inflection point voltage of the IGBT Fitting coefficients as a function of temperature.

[0033] In this embodiment, This information is derived from the datasheet of the selected SiC MOSFET model. 20mΩ A Provided by the device datasheet - The curve shows that A= 0.00028. This information is derived from the datasheet of the selected IGBT model. 0.8V, B The results were obtained through static characteristic experiments on the hybrid device. B= 0.002.

[0034] Step 4, based on the on-resistance value of the SiC MOSFET and the inflection point voltage of IGBT The switching current threshold of the conduction mode is calculated. , .

[0035] Step 5, when the load Changes cause load current in the circuit During fluctuations, the switching mode of the switching element is switched according to the following rules: If Then the control switching element switches to conduction mode 1, and its switching state is that only the SiC MOSFET is turned on; if If the switching element is switched to conduction mode 2, its switching state is IGBT conduction, and the SiC MOSFET is turned off after the IGBT conduction.

[0036] In this embodiment, the switching of the conduction mode of the switching element is completed by the drive controller.

[0037] To demonstrate the technical effects of this invention, Figure 2 A circuit with a DC voltage of 500V and a switching frequency of 10KHz, which adopts the control strategy proposed in this invention, was simulated.

[0038] Figure 3 The simulation results show the temperature difference waveforms between the SiC MOSFET and IGBT junctions, obtained from the existing control strategy and the control strategy of this invention. Figure 3 As can be seen, the control strategy of this invention automatically lowers the threshold at high temperatures, prompting the system to enter the cooperative mode earlier and utilizing IGBT shunt to prevent thermal runaway of the SiC MOSFET. The solid line in the figure shows that the temperature difference between the SiC MOSFET and IGBT junction using the control strategy proposed in this invention reached approximately 4.7°C at the end of the simulation. Compared with the existing technology controlling the temperature difference between the SiC MOSFET and IGBT junction (28.7°C as shown by the dashed line in the figure), the temperature difference between the SiC MOSFET and IGBT junction in the system is reduced by approximately 85.7%. This directly proves that this invention effectively alleviates the problem of excessive heat concentration in the SiC MOSFET due to the large temperature difference between the SiC MOSFET and IGBT junction, improving the system's safety margin and reliability.

Claims

1. A method for adaptive adjustment of the conduction mode threshold of a hybrid device based on temperature feedback, wherein the circuit involved in the method comprises a switching element and a load connected in series. A circuit consisting of a ground plane and a switching element, wherein the switching element is a hybrid device composed of SiC MOSFETs and IGBTs; characterized in that... The aforementioned adjustment method, under scenarios with continuously changing loads, adjusts the current temperature and the on-resistance of the SiC MOSFET. and the inflection point voltage of IGBT The conduction mode of the switching element is adjusted in real time according to the switching cycle; any switching cycle in which the switching element operates is recorded as the current switching cycle, and the adjustment steps for the current switching cycle are as follows: Step 1: Sample the current flowing through the SiC MOSFET I MOS Current flowing through the IGBT I IGBT Voltage drop across the hybrid device The instantaneous power loss of the SiC MOSFET was calculated. and the instantaneous loss of IGBT ; Step 2: Calculate the temperature of the SiC MOSFET in the circuit. With the temperature of IGBT ; Step 3, based on the temperature of the SiC MOSFET and the temperature of IGBT The on-resistance of the SiC MOSFET was calculated. and the inflection point voltage of IGBT ; Step 4, based on the on-resistance value of the SiC MOSFET and the inflection point voltage of IGBT The switching current threshold of the conduction mode is calculated. , ; Step 5, when the load Changes cause load current in the circuit During fluctuations, the switching mode of the switching element is switched according to the following rules: If Then the control switching element switches to conduction mode 1, and its switching state is that only the SiC MOSFET is turned on; if If the switching element is switched to conduction mode 2, its switching state is IGBT conduction, and the SiC MOSFET is turned off after the IGBT conduction.

2. The method for adaptive adjustment of the conduction mode threshold of a hybrid device based on temperature feedback as described in claim 1, characterized in that, Instantaneous power loss of the SiC MOSFET described in step 1 and the instantaneous loss of IGBT The formula for calculation is: 。 3. The method for adaptive adjustment of the conduction mode threshold of a hybrid device based on temperature feedback as described in claim 1, characterized in that, The temperature of the SiC MOSFET mentioned in step 2 With the temperature of IGBT The formula for calculation is: in, Indicates ambient temperature. This indicates the thermal resistance from the SiC MOSFET junction to the environment. This indicates the thermal resistance between the IGBT junction and the environment. Indicates the heat capacity of a SiC MOSFET. Indicates the heat capacity of the IGBT. This indicates the temperature of the SiC MOSFET at the end of the previous switching cycle. This indicates the temperature of the IGBT at the end of the previous switching cycle. This indicates the duration of a switching cycle from heating to cooling.

4. The method for adaptive adjustment of the conduction mode threshold of a hybrid device based on temperature feedback as described in claim 1, characterized in that, Step 3: SiC MOSFET on-resistance and the inflection point voltage of IGBT The calculation formulas are as follows: in, To be in harmony with ambient temperature The corresponding SiC MOSFET on-resistance value, A The on-resistance value of the SiC MOSFET Fitting coefficients as a function of temperature To be in harmony with ambient temperature The corresponding IGBT inflection point voltage, B The inflection point voltage of the IGBT Fitting coefficients as a function of temperature.

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