Evaluation of Silicon Carbide Power MOSFET Short-circuit Ruggedness, and MMC-based High Voltage-step-down Ratio Dc/Dc Conversion PDF Download

Author: Diang Xing
Publisher:
ISBN:
Category : DC-to-DC converters
Languages : en
Pages : 0

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Silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) greater than 1.2 kV are attractive for medium-voltage (MV) power systems. Compared to traditional silicon (Si) based systems, designs utilizing SiC devices have shown improved performance. Due to improvements in SiC technology, there has been a great investment in the research and development of SiC devices, allowing for an increase in marketshare. Today, SiC MOSFETs have already become more readily available from many device manufacturers. The ruggedness of these devices against short-circuit (SC) events is becoming one of the major concerns for market acceptance. During a SC event, the device is stressed simultaneously with high drain-source voltage and high current, leading to adiabatic heating. This could result in device failure, thus compromising system operation. Industry and transportation applications require switching devices to sustain a considerable SC time to ensure reliable protection. Therefore, it is critical to characterize the SiC devices’ SC withstand time (SCWT), SC-induced degradation, and failure mechanisms. As these devices are being applied in MVDC systems, advantages like high power density and efficiency can be achieved. Circuit topologies of isolated high voltage-stepdown ratio dc/dc converters are studied. Among them, the square-wave modular multilevel converter (MMC) based topologies can have high operational flexibility to achieve voltage-step-down and frequency multiplication functions, which have significant implications for designs and applications. In a case study focusing on a 250-kW, 7-kV, MVDC energy storage system designed for improved grid resiliency, comparisons of numerical results are conducted among the MMC-based topologies. A scaled-down 10-kW prototype is presented later. The circuit parameters and failure modes are analyzed, and the design guidelines of the hardware components are introduced. This MV and medium-frequency (MF) converter can achieve 97.55% efficiency at the full load condition. The last part of this dissertation provides conclusions and outlooks for future work.

Author: Eial Awwad, Abdullah
Publisher: Universitätsverlag der TU Berlin
ISBN: 3798330964
Category : Technology & Engineering
Languages : en
Pages : 184

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Increasing demand for efficiency and power density pushes Si-based devices to some of their inherent material limits, including those related to temperature operation, switching frequency, and blocking voltage. Recently, SiC-based power devices are promising candidates for high-power and high-frequency switching applications. Today, SiC MOSFETs are commercially available from several manufacturers. Although technology affiliated with SiC MOSFETs is improving rapidly, many challenges remain, and some of them are investigated in this work. The research work in this dissertation is divided into the three following parts. Firstly, the static and switching characteristics of the state-of-the-art 1.2 kV planar and double-trench SiC MOSFETs from two different manufacturers are evaluated. The effects of different biasing voltages, DC link voltages, and temperatures are analysed. The characterisation results show that the devices exhibit superior switching performances under different operating conditions. Moreover, several aspects of using the SiC MOSFET’s body diode in a DC/DC converter are investigated, comparing the body-diodes of planar and double-trench devices. Reverse recovery is evaluated in switching tests considering the case temperature, switching rate, forward current, and applied voltage. Based on the measurement results, the junction temperature is estimated to guarantee safe operation. A simple electro-thermal model is proposed in order to estimate the maximum allowed switching frequency based on the thermal design of the SiC devices. Using these results, hard- and soft-switching converters are designed, and devices are characterised as being in continuous operation at a very high switching frequency of 1 MHz. Thereafter, the SiC MOSFETs are operated in a continuous mode in a 10 kW / 100-250 kHz buck converter, comparing synchronous rectification, the use of the body diode, and the use of an external Schottky diode. Further, the parallel operation of the planar devices is considered. Thus, the paralleling of SiC MOSFETs is investigated before comparing the devices in continuous converter operation. In this regard, the impact of the most common mismatch parameters on the static and dynamic current sharing of the transistors is evaluated, showing that paralleling of SiC MOSFETs is feasible. Subsequently, an analytical model of SiC MOSFETs for switching loss optimisation is proposed. The analytical model exhibits relatively close agreement with measurement results under different test conditions. The proposed model tracks the oscillation effectively during both turn-on and –off transitions. This has been achieved by considering the influence of the most crucial parasitic elements in both power and gate loops. In the second part, a comprehensive short-circuit ruggedness evaluation focusing on different failure modes of the planar and double-trench SiC devices is presented. The effects of different biasing voltages, DC link voltages, and gate resistances are evaluated. Additionally, the temperature-dependence of the short-circuit capability is evaluated, and the associated failure modes are analysed. Subsequently, the design and test of two different methods for overcurrent protection are proposed. The desaturation technique is applied to the SiC MOSFETs and compared to a second method that depends on the stray inductance of the devices. Finally, the benefits of using SiC devices in continuous high-frequency, high-power DC/DC converters is experimentally evaluated. In this regard, a design optimisation of a high-frequency transformer is introduced, and the impact of different core materials, conductor designs, and winding arrangements are evaluated. A ZVZCS Phase-Shift Full-Bridge unidirectional DC/DC converter is proposed, using only the parasitic leakage inductance of the transformer. Experimental results for a 10 kW, (100-250) kHz prototype indicate an efficiency of up to 98.1% for the whole converter. Furthermore, an optimized control method is proposed to minimise the circulation current in the isolated bidirectional dual active bridge DC/DC converter, based on a modified dual-phase-shift control method. This control method is also experimentally compared with traditional single-phase shift control, yielding a significant improvement in efficiency. The experimental results confirm the theoretical analysis and show that the proposed control can enhance the overall converter efficiency and expand the ZVZCS range. Die steigende Nachfrage nach Effizienz und Leistungsdichte bringt Si-basierte eistungsbauteile an einige inhärente Materialgrenzen, die unter anderem mit der Temperaturbelastung, der Schaltfrequenz und der Blockierspannung in Zusammenhang stehen. In jüngster Zeit sind SiC-basierte Leistungsbauelemente vielversprechende Kandidaten für Hochleistungs- und Hochfrequenzanwendungen. Aktuell sind SiC-MOSFETs von mehreren Herstellern im Handel erhältlich. Obwohl sich die Technologie der SiC-MOSFETs rasch verbessert, werden viele Herausforderungen bestehen bleiben. Einige dieser Herausforderungen werden in dieser Arbeit untersucht. Die Untersuchungen in dieser Dissertation gliedern sich in die drei folgenden Teile: Im ersten Teil erfolgt, die statische und die transiente Charakterisierung der aktuellen 1,2 kV Planarund Doubletrench SiC-MOSFETs verschiedener Hersteller. Die Auswirkungen unterschiedlicher Gatespannungen, Zwischenkreisspannungen und Temperaturen werden analysiert. Die Ergebnisse der Charakterisierung zeigen, dass die Bauteile überlegene Schaltleistungen unter verschiedenen Betriebsbedingungen aufweisen. Darüber hinaus wird der Einsatz der internen SiC-Bodydioden in einem DC/DC-Wandler untersucht, wobei die Unterschiede zwischen Planar- und Doppeltrench-Bauteilen aufgezeigt werden. Das Reverse-Recovery-Verhalten wird unter Berücksichtigung der Gehäusetemperatur, der Schaltgeschwindigkeit, des Durchlassstroms und der angelegten Spannung bewertet. Anhand der Messergebnisse wird die Sperrschichttemperatur geschätzt, damit ein sicherer Betrieb gewährleistet ist. Ein einfaches elektrothermisches Modell wird vorgestellt, um die maximal zulässige Schaltfrequenz auf der Grundlage des thermischen Designs der SiC-Bauteile abzuschätzen. Anhand dieser Ergebnisse werden hart- und weichschaltende Umrichter konzipiert und die Bauteile werden im Dauerbetrieb mit einer sehr hohen Schaltfrequenz von 1 MHz untersucht. Danach werden die SiC-MOSFETs im Dauerbetrieb in einem 10 kW / 100-250 kHz-Tiefsetzsteller betrieben. Dabei wird die Synchrongleichrichtung, die Verwendung der internen Diode und die Verwendung einer externen Schottky-Diode verglichen. Außerdem wird die Parallelisierung von SiC-MOSFETs untersucht, bevor die Parallelschaltung der verschiedenen Bauelemente ebenso im kontinuierlichen Konverterbetrieb verglichen wird. Es wird der Einfluss der häufigsten Parametervariationen auf die statische und dynamische Stromaufteilung der Transistoren analysiert, was zeigt, dass eine Parallelisierung von SiC-MOSFETs möglich ist. Anschließend wird ein analytisches Modell der SiC-MOSFETs zur Schaltverlustoptimierung vorgeschlagen. Das analytische Modell zeigt eine relativ enge Übereinstimmung mit den Messergebnissen unter verschiedenen Testbedingungen. Das vorgeschlagene Modell bildet die Schwingungen sowohl beim Ein- als auch beim Ausschalten effektiv nach. Dies wurde durch die Berücksichtigung der wichtigsten parasitären Elemente in Strom- und Gatekreisen erreicht. Im zweiten Teil wird eine umfassende Bewertung der Kurzschlussfestigkeit mit Fokus auf verschiedene Ausfallmodi der planaren und double-trench SiC-Bauelemente vorgestellt. Die Auswirkungen unterschiedlicher Gatespannungen, Zwischenkreisspannungen und Gate-Widerstände werden ausgewertet. Zusätzlich wird die temperaturabhängige Kurzschlussfähigkeit ausgewertet und die zugehörigen Fehlerfälle werden analysiert. Anschließend wird die Auslegung und Prüfung von zwei verschiedenen Verfahren zum Überstromschutz evaluiert. Die „Desaturation“-Technik wird auf SiC-MOSFETs angewendet und mit einer zweiten Methode verglichen, welche die parasitäre Induktivität der Bauelemente nutzt. Schließlich wird der Nutzen des Einsatzes von SiC-Bauteilen in kontinuierlichen Hochfrequenz-Hochleistungs-DC/DC-Wandlern experimentell untersucht. In diesem Zusammenhang wird eine Designoptimierung eines Hochfrequenztransformators vorgestellt und der Einfluss verschiedener Kernmaterialien, Leiterausführungen und Wicklungsanordnungen wird bewertet. Es wird ein unidirektionaler ZVZCS Vollbrücken-DC/DC-Wandler vorgestellt, der nur die parasitäre Streuinduktivität des Transformators verwendet. Experimentelle Ergebnisse für einen 10 kW, (100-250) kHz Prototyp zeigen einenWirkungsgrad von bis zu 98,1% für den gesamten Umrichter. Abschließend wird ein optimiertes Regelverfahren verwendet, welches auf einem modifizierten Dual-Phase-Shift-Regelverfahren basiert, um den Kreisstrom im isolierten bidirektionalen Dual-Aktiv-Brücken-DC/DC-Wandler zu minimieren. Diese Regelmethode wird experimentell mit der herkömmlichen Single-Phase-Shift-Regelung verglichen. Hierbei zeigt sich eine deutliche Effizienzsteigerung durch die neue Regelmethode. Die experimentellen Ergebnisse bestätigen die theoretische Analyse und zeigen, dass die vorgeschlagene Regelung den Gesamtwirkungsgrad des Umrichters erhöhen und den ZVZCS-Bereich erweitern kann.

Author:
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Category :
Languages : en
Pages : 12

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Our paper presents a comprehensive short-circuit ruggedness evaluation and numerical investigation of up-to-date commercial silicon carbide (SiC) MOSFETs. The short-circuit capability of three types of commercial 1200-V SiC MOSFETs is tested under various conditions, with case temperatures from 25 to 200 degrees C and dc bus voltages from 400 to 750 V. It is found that the commercial SiC MOSFETs can withstand short-circuit current for only several microseconds with a dc bus voltage of 750 V and case temperature of 200 degrees C. Moreover, the experimental short-circuit behaviors are compared, and analyzed through numerical thermal dynamic simulation. Specifically, an electrothermal model is built to estimate the device internal temperature distribution, considering the temperature-dependent thermal properties of SiC material. Based on the temperature information, a leakage current model is derived to calculate the main leakage current components (i.e., thermal, diffusion, and avalanche generation currents). Finally, numerical results show that the short-circuit failure mechanisms of SiC MOSFETs can be thermal generation current induced thermal runaway or high-temperature-related gate oxide damage.

Author: Victor Soler
Publisher:
ISBN:
Category :
Languages : en
Pages : 250

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A sustainable future requires efficient power electronic converters at any stage of the electrical energy consumption. Silicon carbide (SiC) is one of the most technologically advanced wide bandgap semiconductors that can outperform silicon limits for power devices. SiC power MOSFETs are of the greatest interest since they are unipolar gate-controlled switches with high blocking voltage capability and reasonably low specific on-resistance. The focus of this thesis is on the design optimisation and process technology refinement towards the improvement of high-voltage SiC MOSFETs. Previous developments in our group were taken as a reference for this work. The results of this research allowed the fabrication of large-area SiC power MOSFETs with voltage ranges targeting 1.7 kV up to 6.5 kV.The inherent properties of SiC entail challenging technological solutions to successfully integrate a power MOSFET of such high-voltage capability. To ensure suitable blocking capability, different planar edge termination structures have been designed, optimised by TCAD simulation and implemented on PiN diodes. The termination schemes considered are single-zone JTE, FGRs and a novel RA-JTE structure combining JTE with rings. RA-JTE design, with the lowest sensitivity to fabrication process deviations and a lower consumed area, achieved more than 90% of the ideal breakdown voltage and suitable blocking capability up to 6.5 kV.The optimisations performed on the unit-cell of the SiC power MOSFET target both the layout design and the fabrication process. The optimisation has been performed by TCAD modelling and experimental evaluation of specific test structures. Several techniques to improve the performance of the fabricated devices have been considered: i) the use of an offset retrograde p-body profile to provide an adequate Vth value while preventing p-body punch-through, ii) a submicronic self-aligned channel definition, iii) a boron treatment to the gate oxide to improve channel mobility, iv) a discrete location of the p-contact to reduce cell-pitch, v) the use of a lower-doped-source (LDS) to improve reliability, vi) the optimisation of the JFET area, and vii) the integration of gate runners to improve the switching performance. As a result of these investigations, a full mask-set were designed and used for processing wafers of several voltage-class in different batches. All the fabrication steps have been carried out at IMB-CNM cleanroom. The electrical characterisation of large-area devices has evidenced an optimal Vth in the range of 5 V, a proper gate control, and a good blocking capability. We obtained relatively high specific on-resistance due to the large cell pitch dimensions required by IMB-CNM cleanroom design rules as well as a still low channel mobility. Fabricated SiC MOSFETs are capable of switching at high bus voltages (tested up to 80% of the rated voltage). Although, their switching performance is limited by internal gate resistance. Fabricated devices have shown better short-circuit capability (>15 μs) than existing commercial devices, mainly due to the cell design considerations.The evaluation of electrical performance evidenced the successful functionality of the fabricated VDMOS up to 6.5 kV and validates our new RA-JTE termination design. On the other hand, the novel boron doping treatment to the gate oxide clearly demonstrated to improve the on-resistance of our devices in all voltage classes without affecting breakdown and short-circuit capabilities. Nevertheless, it strongly compromises stability and reliability at temperatures above 100 °C. These results show that the MOS interface quality is still the major issue for the development of reliable SiC power MOSFETs.Finally, alternative SiC structures have also been investigated to take advantage of the SiC superior material properties. These include a SiC IGBT showing conductivity modulation, and a preliminary SiC CMOS cell able to operate at high temperatures.

Author: Abdullah Eial Awwad
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Category :
Languages : en
Pages :

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This research focuses on the design, characterization, modeling and analysis of high voltage Silicon Carbide (SiC) metal-oxide-semiconductor field effect transistors (MOSFET), insulated gate bipolar transistors (IGBT) and emitter turn-off thyristors (ETO) to satisfy the stringent requirements of advanced power electronic systems. The loss information, frequency capability and switching ruggedness of these 10-kV SiC power devices are studied extensively in order to provide their application prospects in solid-state transformers (SST). Among 10-kV SiC power devices, SiC MOSFETs are of the greatest interest due to their lower specific on-resistance compared to silicon MOSFETs, and their inherently fast switching speed due to their majority carrier conduction mechanism. Therefore, 10-kV SiC MOSFETs are studied first in this dissertation. The characterization, modeling and analysis of 10-kV SiC MOSFETs were investigated extensively. The low losses and high switching frequency of 10-kV SiC MOSFETs were demonstrated in characterization study and a 4-kV 4 kW boost converter. The on-resistance of SiC MOSFETs increases rapidly with increased junction temperature and blocking voltage. This makes their conduction losses possibly unacceptable for applications where high DC supply voltages (more than 10-kV) and high temperature operation are used. This warrants the development of SiC bipolar devices (IGBTs and thyristors) to achieve smaller conduction losses due to the conductivity modulation of their thick drift layers, especially at elevated temperatures. Therefore, design, characterization and optimization of 10-kV SiC IGBT and ETO were dicussed. A 4H-SiC p-channel IGBT with improved conduction characteristics was developed and characterized experimentally as well as analyzed theoretically by numerical simulations. The device exhibited a differential on-resistance of 26 mOhm.cm^2 at a collector current density of 100 A/cm^2 at room temperature. An the SiC IGBT showed a turn-of.

Author: Xintong Lyu
Publisher:
ISBN:
Category : Silicon carbide
Languages : en
Pages : 102

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Silicon Carbide (SiC) power devices become popular in electric/hybrid vehicles, energy storage power converters, high power industrial converters, locomotive traction drives and electric aircrafts. Compared with its silicon counterparts, SiC metal oxide semiconductor field effect transistors (MOSFETs) feature higher blocking voltage, higher operating temperature, higher thermal conductivity, faster switching speed, and lower switching loss. This dissertation studies the medium voltage SiC power switch design, packaging, reliability testing and protection, aiming to achieve high power density low cost design with improved reliability. This work first investigates medium voltage SiC MOSFET short circuit capability and degradation under short circuit events. Lower short circuit energy is an effective approach to protect the medium voltage SiC MOSFET from catastrophic failure and slow down the device degradation under repeated over-current conditions. To ensure high efficiency operation under normal conditions and effective protection under short circuit condition, a three-step short circuit protection method is proposed. With ultra-fast detection, the protection scheme can quickly respond to the short circuit events and actively lower the device gate voltage to enhance its short circuit capability. Eventually, the conventional desaturation protection circuits confirm the faulty condition and softly turns off the device. Based on the 3300 V SiC MOSFET characteristic and circuit parameters, the protection circuit design guideline is provided. The exploration on the medium voltage SiC MOSFET packaging follows. To further increase the power density, the medium voltage SiC device packaging becomes a multi-disciplinary subject involving electrical, thermal, and mechanical design. Multi-functional package components are desired to deal with more than one concerns in the application. The relationship between electrical, thermal, and mechanical properties needs to be understood and carefully designed to achieve a fully integrated high-performance power module. The adoption of ceramic baseplate is assessed in the aspects of the insulation design, the thermal design, the power loop layout, the electromagnetic interference considerations, respectively. Mathematical models, simulations, and experimental results are presented to verify the analysis. The adoption of the medium voltage SiC MOSFETs in the various application is slowed by its unclear long-term reliability and high cost. The reliability issue can be mitigated by the aforementioned three-step protection method. An economic alternative for medium voltage power switch is the super-cascode structure. The super-cascode structure is composed of series connected low voltage MOSFET and normally-on junction gate field-effect transistors (JFETs). The voltage balancing among series connected devices is realized by the added capacitors and diodes. Circuit models during the switching transients are built. Based on the developed models, a method to optimize the voltage balancing circuit parameters is proposed. The analysis and optimization method are verified by the experimental results. Sensitivity analysis is conducted to see the impact of the capacitance tolerance. Conclusions and recommendations for future work are presented at the end of this dissertation.

Author: Peter Friedrichs
Publisher: John Wiley & Sons
ISBN: 9783527629084
Category : Science
Languages : en
Pages : 520

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Silicon Carbide - this easy to manufacture compound of silicon and carbon is said to be THE emerging material for applications in electronics. High thermal conductivity, high electric field breakdown strength and high maximum current density make it most promising for high-powered semiconductor devices. Apart from applications in power electronics, sensors, and NEMS, SiC has recently gained new interest as a substrate material for the manufacture of controlled graphene. SiC and graphene research is oriented towards end markets and has high impact on areas of rapidly growing interest like electric vehicles. This volume is devoted to high power devices products and their challenges in industrial application. Readers will benefit from reports on development and reliability aspects of Schottky barrier diodes, advantages of SiC power MOSFETs, or SiC sensors. The authors discuss MEMS and NEMS as SiC-based electronics for automotive industry as well as SiC-based circuit elements for high temperature applications, and the application of transistors in PV-inverters. The list of contributors reads like a "Who's Who" of the SiC community, strongly benefiting from collaborations between research institutions and enterprises active in SiC crystal growth and device development. Among the former are CREE Inc. and Fraunhofer ISE, while the industry is represented by Toshiba, Nissan, Infineon, NASA, Naval Research Lab, and Rensselaer Polytechnic Institute, to name but a few.

Author: Mohamed Torky
Publisher:
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Category :
Languages : en
Pages : 0

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Category :
Languages : en
Pages : 14

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Here we present a board-level integrated silicon carbide (SiC) MOSFET power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200°C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC MOSFET phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate driver and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225°C.