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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Evaluation of GaN Based Multilevel Converters
摘要： With the significant reduction in board space occupied by the smaller GaN transistors, topologies that require a greater number of active devices as a tradeoff for reduced passive size, the main barrier to higher density, have become attractive. Switched capacitor multilevel converters are good examples of topologies that can effectively reduce or eliminate passive components. Two GaN based proof-of-concept designs (three-level converters), one for a low voltage (LV) 48 V server application and the other for a higher voltage (HV) 400 V power factor correction (PFC) circuit are discussed in this paper. As a result of using lower figure-of-merit (FOM) devices, significant efficiency gains are observed for the LV and HV converters developed in this paper compared to a two-level topology. Smaller passive size (mainly inductors) also provides a significant increase in power density for the LV converter. A startup scheme is discussed which eliminates the need for extraneous control loops or high voltage rated devices for the top switch. Finally, an electrical performance comparison is also shown for a two-stage intermediate bus architecture (IBA) developed with the GaN based three-level converter for the front end and a high frequency GaN-based second buck stage for 48 V to 1 V point-of-load (PoL) conversion. Two choices of intermediate bus voltage are investigated: 12 V and 6 V. Each bus voltage demonstrates its advantage in a certain range of load current.
关键词： efficiency,DC-DC converter,GaN,Startup,power density,IBC,Multilevel
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - High Voltage GaN Switch Reliability FIT rates and PPM reliability based on standards from: Joint Electron Device Engineering Council (JEDEC), Automotive Electronics Council (AEC) and German Electrical and Electronic Manufacturers' Association (ZVEI)
摘要： Adoption of any semiconductor technology by the power conversion market requires the understanding of fundamental failure modes, acceleration factors and reliability statistics. This study shows how GaN products from Transphorm can meet this challenge, especially in the critical High Voltage Off State (HVOS) reliability stress test. The anticipated failure rate during a product’s first 10 to 20 years of use is of particular interest as it has direct impact on warranty costs. This market requirement can be addressed by testing to failure statistically significant samples of devices, and analyzing the data with appropriate models. The methods developed for measuring GaN reliability on large samples will be discussed, which are wholly based on existing industrial and automotive standards. The resulting data can be used to supplement qualification testing results when the failure modes and acceleration factors are well understood.
关键词： GaN,FIT,PPM,HEMT,acceleration factor,power electronics,reliability
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Substrate Bias Effect on E-Mode GaN-on-Si HEMT Cos<inf>s</inf> Losses
摘要： Previous work found large COSS losses in GaN-on-Si HEMTs used in soft-switched, MHz-frequency power converters. Here, we use a back-gate bias between the source and Si substrate to investigate the capacitance characteristics of commercially-available GaN HEMTs. The small-signal capacitance is reduced significantly – up to 2× for a 650 V HEMT and 4× for a 100 V HEMT – indicating that the drain-substrate capacitance is a significant portion of the total output capacitance. This portion of the capacitance appears responsible for trapping-detrapping with time constants on the order of seconds. We verify this by testing the 100 V GaN HEMT in the Sawyer-Tower circuit with negative substrate bias, finding that COSS losses are reduced by up to 30% compared to the shorted substrate condition.
关键词： Sawyer-Tower circuit,COSS losses,capacitance characteristics,GaN-on-Si HEMTs,substrate bias
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - C-V Measurement under Different Frequencies and Pulse-mode Voltage Stress to Reveal Shallow and Deep Trap Effects of GaN HEMTs
摘要： In this work, the influence of interface traps at the Si3N4/ (GaN) /AlGaN interface and carbon-related buffer traps on AlGaN/GaN-on-silicon high electron mobility transistors (HEMTs) has been studied using high-frequency capacitance-voltage (HFCV) and quasi-static C-V (QSCV) measurement. The correlation between Ron degradation and two different traps distributions subjected to different operation conditions have been investigated. Deep-level traps from the hole-emission process of carbon-related buffer have been activated by high drain voltage under off-state in pulse-mode condition and shallow-level traps from interface states are observed with an increase in gate voltage under on-state.
关键词： Traps,GaN HEMTs,Pulse-mode Stress,C-V measurement
更新于2025-09-04 15:30:14
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Asymmetry of the Defect Structure of Semipolar GaN Grown on Si(001)
摘要： The defect structure of a thick (~15 μ m) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.
关键词： transmission electron microscopy,semipolar GaN,threading dislocations,hydride–chloride vapor phase epitaxy,defect structure
更新于2025-09-04 15:30:14