A method for in situ high-bandwidth junction temperature estimation of insulated-gate bipolar transistors is introduced in this paper. The method is based on the acquisition of the gate voltage plateau during turn- on . It can be related to the junction temperature at any known device current, that can be effectively approximated using existing phase current measurements. This allows fast overtemperature protection of the power device or even active thermal cycle reduction via thermal control. This paper discusses, first, the physical mechanisms leading to the temperature sensitivity of the gate voltage plateau. Second, a rigorous sensitivity analysis of the gate voltage plateau is conducted. It allows to determine the maximal estimation error and provides information about the suitability of this method for various devices and applications. Finally, a sensing circuitry is presented, which allows accurate gate voltage plateau sensing every switching period as well as an easy integration into the gate driver. The performance of the proposed method is experimentally demonstrated with the sensing circuitry on a double pulse test bench over a wide operation range.

IGBT Junction Temperature Estimation via Gate Voltage Plateau Sensing

Electrothermal modeling of silicon carbide (SiC) power devices is frequently performed to estimate the device temperature in operation, typically assuming a constant thermal conductivity and/or heat capacity of the SiC material. Whether and by how much the accuracy of the resulting device temperature prediction under these assumptions is compromised has not been investigated so far. Focusing on high-temperature operating conditions as found under short circuit (SC), this paper presents a comprehensive analysis of thermal material properties determining the temperature distribution inside SiC power mosfet s. Using a calibrated technology computer-aided design (TCAD) electrothermal model, it is demonstrated that the temperature prediction of SiC power devices under SC operation when neglecting either the top metallization or the temperature dependence of the heat capacity is inaccurate by as high as 25%. The presented analysis enables to optimize compact electrothermal models in terms of accuracy and computational time, which can be used to assess the maximum temperature of SiC power mosfet s in both discrete packages and multichip power modules exposed to fast thermal transients. A one-dimensional thermal network of a SiC power mosfet is proposed based on the thermal material properties, the size of the active area of the device, and its thickness.

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Accurate Temperature Estimation of SiC Power mosfet s Under Extreme Operating Conditions

This paper proposes a methodology for active thermal control of power electronic modules in ac applications, which includes a loss manipulation unit, a thermal observer structure, and an active thermal cycle reduction algorithm. It aims to reduce the thermo-mechanical strain in the inter-connects of the module in order to enhance its reliability and lifetime. The loss manipulation unit operates in a minimally invasive manner by manipulating adaptive gate resistances and the pulsewidth modulation frequency. This allows the individual thermal control of multiple devices within a power module, which has not been achieved in prior work. A thermal observer structure that estimates averaged junction temperatures by combination of a thermal model and sensor information is introduced. The observer technology makes this paper the first to realize closed-loop control of averaged temperatures achieving an increased robustness and insensitivity to modeling errors. A key element of the active thermal cycle reduction algorithm is the virtual heat sink that derives feasible and stress-relieving thermal trajectories. The trajectories are applied with a unique thermal feedback control that smoothly manipulates the averaged junction temperature of the power module even in the presence of loss manipulation limits. The active thermal control methodology is evaluated experimentally with a state-of-the-art insulated-gate bipolar transistor (IGBT) power module.

Methodology for Active Thermal Cycle Reduction of Power Electronic Modules

This paper presents a methodology for real-time monitoring of 3-D temperature distributions and device losses within power electronic modules. It allows precise thermal management, empirical lifetime prognosis, and detection of critical degradation of the power module. By effective combination of thermal 3-D finite difference modeling, parametric loss models, and model truncation techniques, a compact thermal real-time model is derived. It enables the computation of device losses and temperatures at critical locations within a power module, e.g., at the devices, solder interfaces or the base plate, on a conventional digital signal processor. The real-time model as well as real-time junction temperature information are combined in a new Luenberger-style observer structure. Applying bandwidth partitioning, the observer estimates the temperatures throughout the power module every switching period and averaged over one excitation period with nearly zero lag, even if the junction temperature measurement exhibits delays and has noisy signals. Furthermore, it estimates errors in the loss prediction process that can be tracked over the lifetime of the power module to detect degradation of the devices or the power module. The observer and its features are experimentally evaluated under realistic operating conditions on a load emulator using a state-of-the-art automotive power module.

Monitoring 3-D Temperature Distributions and Device Losses in Power Electronic Modules

The electrification of the transportation sector is moving on at a fast pace. All car manufacturers have strong programs to electrify their car fleet to fulfill the demands of society and customers by offering carbon-neutral technologies to bring goods and persons from one location to another. Power electronics technology is, in this evolution, essential and also in a rapid development technology-wise. Some of the introduced technologies are quite mature, and the systems designed must have high reliability as they can be quite complicated from an electrical perspective. Therefore, this article focuses on the reliability of the used power electronic systems applied in electric vehicles (EVs) and hybrid EVs (HEVs). It introduces the reliability requirements and challenges given for the power electronics applied in EV/HEV applications. Then, the advances in power electronic components to address the reliability challenges are introduced as they individually contribute to the overall system reliability. The reliability-oriented design methodology is also discussed, including two examples: an EV onboard charger and the drive train inverter. Finally, an outlook in terms of research opportunities in power electronics reliability related to EV/HEVs is provided. It can be concluded that many topics are already well handled in terms of reliability, but issues related to complete new technology introduction are important to keep the focus on.

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Reliability of Power Electronic Systems for EV/HEV Applications

In this work, the spatial electro-thermal modeling and simulation of power electronic modules is discussed. It is shown how physical and mathematical modeling techniques can be combined to obtain a compact time-efficient electro-thermal simulation framework for power electronic modules. The accuracy of the modeling framework is demonstrated based on experiments. It can be used for the fast calculation of the temperature distribution of a power module in an electric vehicle over driving cycles. The spatial temperature information allows to effectively estimate the lifetime of the power module.

Spatial Electro-Thermal Modeling and Simulation of Power Electronic Modules

In this work the spatial electro-thermal modeling of power electronic modules is discussed. It is shown how physical and mathematical modeling techniques can be combined to obtain a compact time efficient electro-thermal simulation framework for power electronic modules. The framework can be used to evaluate the transient temperature distribution of a power module in an electric vehicle over driving cycles. Based on the simulated temperature distribution the lifetime of the power module can be estimated using various aging laws. The simulation and lifetime estimation is demonstrated as an example for a Hybridpack2 inverter module. Finally, a design parameter study is carried out, which evaluates different module design options with respect to their impact on reliability.

Spatial electro-thermal modeling and simulation of power electronic modules

The increasing demand for higher power device utilization and reliability in power electronic systems is driving the integration of condition monitoring and active control in power electronic systems. With thermal heat dissipation being the limiting factor of module lifetime and performance, thermal real-time monitoring is key in this transition. However, this requires the availability of highly accurate and high-bandwidth temperature information with minimal phase lag. This paper reviews key methods for temperature extraction in power modules: temperature sensing, thermal estimators and thermal observers. While previous research has examined individual techniques of these methods in great detail, this paper presents a methodological overview that provides insight to how different technologies may contribute to next generation thermal monitoring solutions. In this context, the paper discusses how different technologies can be effectively combined to improve their overall performance. It finally discusses key challenges that must be addressed such that minimally invasive temperature sensing and thermal monitoring become an industrial practice in the future of power electronics.

Reviewing Thermal Monitoring Techniques for Smart Power Modules

This paper discusses active thermal cycle reduction techniques for power electronic modules. These reduce the thermomechanical strain in the interconnects of the power module leading to an enhanced reliability and lifetime. For this purpose, a model based control algorithm is presented, which allows controlling the temperature of the devices within one half bridge. It uniquely uses a virtual heat sink to determine feasible trajectories for active thermal cycle reduction. This concept is the first to explicitly handle the limitations of the loss manipulation process for a multi-device module. Loss manipulation is realized least invasively by online manipulation of the gate resistance only. For temperature estimation with zero lag, a spatial observer structure is used. It demonstrates the feasibility of observer based active thermal control. The complete control algorithm is validated experimentally with a three phase power module on a load emulator using realistic load cycles.

Lukas A. Ruppert

Papers

Spatial Electro-Thermal Modeling and Simulation of Power Electronic Modules

Methodology for Active Thermal Cycle Reduction of Power Electronic Modules

Spatial electro-thermal modeling and simulation of power electronic modules

Reviewing Thermal Monitoring Techniques for Smart Power Modules

Active thermal cycle reduction of power modules via gate resistance manipulation