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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) - Surge current capability of SiC MOSFETs in AC distribution systems
摘要： Whereas short circuit current and time ratings for power converter applications are often stated by SiC device manufacturers, surge current capability for AC electrical apparatus applications are rarely available. This paper present the experimental validation of surge current capability of selected SiC devices for low voltage AC distribution system applications. Because AC electrical apparatus, such as relays, contactors, and circuit breakers, have a different set of system parameters and requirements compared to traditional power converter applications, power semiconductor devices need to be validated from a different point of view. In fact, robustness to inductive short circuit currents, inrush currents, short and long time overload are some of the basic requirements for the utilization of WBG devices for these applications. In this paper, we compare the performance of different SiC MOSFETs under different types of AC waveform conditions.
关键词： semiconductor device characterization,temperature measurement,solid state circuit breaker,WBG semiconductor devices,overload capability,surge current,SiC MOSFET,electrical apparatus
更新于2025-09-04 15:30:14
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Optical Sectioning Microscopy For Multilayer Structure With Micro-Scale Air Gaps Measurement
摘要： In this letter, we propose a new method based on the optical sectioning microscopy to characterize the multilayer structure with micro-scale air gaps. With this technique, sinusoidal fringe patterns having a predefined shifted phase produced by digital micro-mirror devices are illuminated onto the sample. The contrast response curve (CRC) of the reflected patterns along the scanning direction is determined by the phase-shifting algorithm while the object is scanned through the focus of the microscope. The maximum contrast value of the CRC occurs at the position where the sample is on the focal plane. The peak positions of the CRC are extracted through the Gaussian fitting and then implemented to achieve the surface topography and gap thickness distribution. To suppress the noise influence caused by the environment fluctuations or other factors, the frequency domain analysis (FDA) has been introduced in this work. The simulations and experiments are conducted to verify the feasibility of this technique, demonstrating the potential to be applied in such fields as semiconductor and biochip, where the air gap may play crucial roles.
关键词： thickness measurement,microscopy,surface topography
更新于2025-09-04 15:30:14
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99 % Efficient 10 kV SiC-Based 7 kV/400 V DC-Transformer for Future Data Centers
摘要： The power supply chain of data centers from the medium voltage (MV) utility grid down to the chip level voltage consists of many series connected power conversion stages and accordingly shows a relatively low ef?ciency. Solid-State Transformers (SSTs) could improve the ef?ciency by substantially reducing the number of power conversion stages and/or directly interfacing the MV AC grid to a 400 V DC bus, from where tens of server racks with a power consumption of several kilowatts could be supplied by individual SSTs. The recent development of SiC MOSFETs with a blocking voltage of 10 kV enables the realization of a simple and hence highly reliable two-stage SST topology, consisting of an AC/DC PFC recti?er and a subsequent isolated DC/DC converter. In this context, an isolated 25 kW, 48 kHz, 7 kV to 400 V series resonant DC/DC converter based on 10 kV SiC MOSFETs is realized and tested in this paper. To achieve zero voltage switching (ZVS) of all MOSFETs, a special modulation scheme to actively control the amount of the switched magnetizing current on the MV and LV side is implemented. Furthermore, the design of all main components and especially the electrical insulation of the employed medium frequency (MF) transformer is discussed in detail. Calorimetric ef?ciency measurements show that a full-load ef?ciency of 99.0 % is achieved, while the power density reaches 3.8 kW/L (63 W/in3).
关键词： ZVS,isolated DC/DC,medium-voltage transformer,10kV SiC MOSFETs,soft-switching,Medium-voltage,calorimetric measurement
更新于2025-09-04 15:30:14
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Considerations for Choosing Sensitive Element Size for Needle and Fiber-Optic Hydrophones I: Spatiotemporal Transfer Function and Graphical Guide
摘要： The spatiotemporal transfer function for a needle or reflectance-based fiber-optic hydrophone is modeled as separable into the product of two filters corresponding to frequency-dependent sensitivity and spatial averaging. The separable hydrophone transfer function model is verified numerically by comparison to a more general rigid piston spatiotemporal response model that does not assume separability. Spatial averaging effects are characterized by frequency-dependent “effective” sensitive element diameter, which can be more than double the geometrical sensitive element diameter. The transfer function is tested in simulation using a nonlinear focused pressure wave model based on Gaussian harmonic radial pressure distributions. The pressure wave model is validated by comparing to experimental hydrophone scans of nonlinear beams produced by three source transducers. An analytic form for the spatial averaging filter, applicable to Gaussian harmonic beams, is derived. A second analytic form for the spatial averaging filter, applicable to quadratic harmonic beams, is derived by extending the spatial averaging correction recommended by IEC 62127-1 Annex E to nonlinear signals with multiple harmonics. Both forms are applicable to all hydrophones (not just needle and fiber optic hydrophones). Simulation analysis performed for a wide variety of transducer geometries indicates that the Gaussian spatial averaging filter formula is more accurate than the Quadratic form over a wider range of harmonics. Additional experimental validation is provided in Part II. Readers who are uninterested in hydrophone theory may skip the theoretical and experimental sections of this paper and proceed to the Graphical Guide for practical information to inform and support selection of hydrophone sensitive element size (but might be well-advised to read the Introduction).
关键词： fiber optic,Acoustic output measurement,hydrophone,spatiotemporal transfer function,needle,spatial averaging
更新于2025-09-04 15:30:14
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Considerations for Choosing Sensitive Element Size for Needle and Fiber-Optic Hydrophones II: Experimental Validation of Spatial Averaging Model
摘要： Acoustic pressure can be measured with a hydrophone. Hydrophone measurements can underestimate incident acoustic pressure due to spatial averaging effects across the hydrophone sensitive element. The spatial averaging filter for a nonlinear focused beam is a low-pass filter that decreases monotonically from 1 to 0 as frequency increases from 0 to infinity. Experiments were performed to test an analytic model for the spatial averaging filter. Nonlinear pressure tone bursts were generated by three source transducers with driving frequencies ranging from 2.5 MHz to 6 MHz, diameters ranging from 19 mm to 64 mm, and focal lengths ranging from 38 mm to 89 mm. The nonlinear pressure fields were measured using four needle hydrophones with nominal geometrical sensitive element diameters of 200, 400, 600, and 1000 μm. The average root-mean-square difference (RMSD) between theoretical and experimental spatial averaging filters was 5.8 ± 2.6%.
关键词： fiber optic,Acoustic output measurement,hydrophone,spatiotemporal transfer function,needle,spatial averaging
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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Exploration of entropic uncertainty relation for two accelerating atoms immersed in a bath of electromagnetic field
摘要： The uncertainty principle as an elementary theory of quantum mechanics plays an important role in quantum information science. In this paper, we study the dynamics of quantum-memory-assisted entropic uncertainty relation for two accelerating atoms coupled with a bath of fluctuating electromagnetic field. The master equation that the system evolution obeys is firstly derived. We find that the mixedness is bound up with the entropic uncertainty. For equilibrium state, the tightness of uncertainty vanishes. For the initial maximum entangled state, the tightness of uncertainty experiences a slight increase and then declines to zero with evolution time. It is found that the greater acceleration makes the uncertainty faster reach a maximum value and stable value. For a fixed acceleration, the uncertainty with different two-atom separations converges to a fixed value. Furthermore, we utilize weak measurement reversal to manipulate the entropic uncertainty. Our explorations may suggest a method of probing entanglement, acceleration effect and vacuum fluctuation effect with entropic uncertainty.
关键词： Fluctuating electromagnetic field,Weak measurement reversal,Dynamics,Mixedness,Entropic uncertainty
更新于2025-09-04 15:30:14
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Performance comparison of Fabry-Perot and Mach-Zehnder interferometers for Doppler lidar based on double-edge technique
摘要： Compared with dual-channel Fabry-Perot interferometer (DFPI), dual-channel Mach-Zehnder interferometer (DMZI) is a new frequency discriminator for Doppler wind lidar based on double-edge detection. The double-edge frequency discrimination systems based on DFPI and DMZI in the wind lidar system are designed, respectively, and the detection principle is analyzed theoretically. Under certain simulation conditions, performances such as line-of-sight (LOS) wind velocity measurement sensitivities, signal-to-noise ratios (SNR) and LOS wind velocity measurement errors of both DFPI and DMZI systems are simulated and compared based on the U.S. standard atmospheric model. The simulation results show that for 1064nm aerosol system, the LOS wind velocity measurement sensitivity of the DMZI system is lower than that of DFPI system and the error is higher than that of DFPI system with the same dynamic wind velocity measurement range. Nevertheless, for 355nm atmospheric molecular system, DMZI system provides a factor of 1.33 times lower error in the LOS wind velocity than that of DFPI with an altitude of 30 km and the LOS wind velocity of 200m/s. Furthermore, in the LOS wind velocity range of -200m/s~+200m/s, the measurement error of DMZI system hardly increases with the increasing of wind speed. Therefore, the results of this study not only provide guidance for the selection of discriminators, but also provide theoretical support for the application of DMZI in the double-edge detection of atmospheric molecular lidar.
关键词： dual-channel Fabry-Perot interferometer,Doppler lidar,wind velocity measurement,dual-channel Mach-Zehnder interferometer,double-edge detection
更新于2025-09-04 15:30:14