A physical RC network model for electro-thermal analysis of a multichip SiC power module

This paper is concerned with the thermal models which can physically reflect the heat-flow paths in a lightweight three-phase half bridge, two-level SiC power module with 6 MOSFETs and can be used for coupled electro-thermal simulation. The finite element (FE) model was first evaluated and calibrated to provide the raw data for establishing the physical RC network model. It was experimentally verified that the cooling condition of the module mounted on a water cooler can be satisfactorily described by assuming the water cooler as a heat exchange boundary in the FE model. The compact RC network consisting of 115 R and C parameters to predict the transient junction temperatures of the 6 MOSFETS was constructed, where cross-heating effects between the MOSFETs are represented with lateral thermal resistors. A three-step curve fitting method was especially developed to overcome the challenge for extracting the R and C values of the RC network from the selected FE simulation results. The established compact RC network model can physically be correlated with the structure and heat-flow paths in the power module, and was evaluated using the FE simulation results from the power module under realistic switching conditions. It was also integrated into the LTspice model to perform the coupled electro-thermal simulation to predict the power losses and junction temperatures of the 6 MOSFETs under switching frequencies from 5 kHz to 100 kHz which demonstrate the good electro-thermal performance of the designed power module

Compact electrothermal reliability modeling and experimental characterization of bipolar latchup in SiC and CoolMOS power MOSFETs

In this paper, a compact dynamic and fully coupled electrothermal model for parasitic BJT latchup is presented and validated by measurements. The model can be used to enhance the reliability of the latest generation of commercially available power devices. BJT latchup can be triggered by body-diode reverse-recovery hard commutation with high dV/dt or from avalanche conduction during unclamped inductive switching. In the case of body-diode reverse recovery, the base current that initiates BJT latchup is calculated from the solution of the ambipolar diffusion equation describing the minority carrier distribution in the antiparallel p-i-n body diode. For hard commutation with high dV/dt, the displacement current of the drain-body charging capacitance is critical for BJT latchup, whereas for avalanche conduction, the base current is calculated from impact ionization. The parasitic BJT is implemented in Simulink using the Ebers-Moll model and the temperature is calculated using a thermal network matched to the transient thermal impedance characteristic of the devices. This model has been applied to CoolMOS and SiC MOSFETs. Measurements show that the model correctly predicts BJT latchup during reverse recovery as a function of forward-current density and temperature. The model presented, when calibrated correctly by device manufacturers and applications engineers, is capable of benchmarking the robustness of power MOSFETs

A methodology to determine reliability issues in automotive SiC power modules combining 1D and 3D thermal simulations under driving cycle profiles

Current environmental concerns and fuel scarcity are leading to the progressive introduction of Electric Vehicles (EV) in the global fleet vehicle population. This requires significant design and research efforts from scientific community and industry to provide reliable automotive electric propulsion systems. The power modules used for automotive traction inverters can be considered as central elements of such systems. As they are subject to high electro-thermal stress during operation, Design-for-Reliability (DfR) approaches should be adopted. Thus, accurate models for electro-thermal simulations are relevant since the early design stages. However, such simulations become highly time consuming and complex when accurate thermal characterization through standardized or real driving conditions needs to be provided. In this context, this work proposes a simulation methodology that combines real-time simulation for electro-thermal characterization of the whole EV propulsion system, using a 1D equivalent thermal impedance circuit, in conjunction with 3D FEM thermal simulation. In this way, an accurate thermal characterization of the power module under driving cycles with long duration (of hundreds of seconds) can be obtained without computing heavy 3D FEM simulations. The proposed procedure allows to simplify and speed up the early design stages while maintaining high accuracy in the results.This work has been supported by the Department of Education, Linguistic Policy and Culture of the Basque Government within the fund for research groups of the Basque university system IT978-16, by the Government of the Basque Country within the research program ELKARTEK as the project ENSOL (KK-2018/00040), and by the program to support the education of researches of the Basque Country PRE_2017_2_0008

A physics-based compact model of SiC power MOSFETs

The presented compact model of SiC power MOSFETs is based on a thorough consideration of the physical phenomena which are important for the device characteristics and its electrothermal behavior. The model includes descriptions of the dependence of channel charge and electron mobility on the charge of interface traps and a simple but effective calculation of the voltage-dependent drain resistance. Comparisons with both physical 2-D device simulations and experiments validate the correctness of the modeling approach and the accuracy of the results

Global electro-thermal modelling and circuit-type simulation of SiC Mosfet power devices in short-circuit operation for critical system analysis

International audienceThe purpose of this paper is to present, for the first time, a global transient electrothermal model and simulation results of commercially recent silicon carbide (SiC) power MOSFET devices. The developed models aim is faithfully transposing specifically experimental short-circuit (SC) behaviour of the studied components, ready-to-use for the analysis of an inverter-leg malfunctioning. After extensive experimentation, a thermal model of the SiC die allows to develop models of gate-leakage current and drain-source current during SC. After verifying the robustness of the proposed models, an original circuit-type with an easy implementation is performed using a commercial circuit simulation tool