359 research outputs found
On-line Junction Temperature and Current Synchronous Extraction for SiC MOSFETs With Electroluminescence Effect
Full text linkIn this letter, a junction-temperature and current extraction method is presented based on the electroluminescence mechanism of the SiC mosfet body diode. Starting from the observation of two characteristic peaks in the emitted light spectrum, we proved that the junction temperature and the drain current can be simultaneously measured. This novel method consists of decoupling the relationship between the intensity of the electroluminescence peaks, the current, and the temperature. Through this optical method with inherent electrical isolation, the junction temperature and current in the SiC chip can be simultaneously measured with high precision. The total error of the junction temperature estimation is within ±3 °C, and the error of the current estimation is about ±0.2 A.</p
Growth and Characterisation of Boron Rich Nanomaterials
Full text linkIn this study nanomaterials are grown in a solid state reaction at 1300C of boron, barium oxide and iron(II/III)oxide powders in an argon atmosphere. The nanomaterials are shown to be grown via vapour based method by growing the nanomaterials on a separate silicon wafer that has been sputtered with iron and placed downstream of the powders in the flow of argon. An area of the silicon wafer is kept free of iron by using a mask when sputtering the wafer. When nanomaterials are grown, the masked area remains free of nanomaterials. This shows that the presence of iron is vital for the nucleation of the nanomaterials and also indicates the possibility of growing these nanomaterials on targeted sites.
The nanomaterials produced are examined and it is found that we have a presence of amorphous, crystalline and multiple twinned nanowires. The evidence collected suggests that 70% of the nanowires are twinned. The single crystal nanowires can be identified as boron carbide by comparing to diffraction pattern simulations of a boron carbide unit cell. The twinned diffraction pattern is shown to be due to different segments of the nanowire being in different diffraction condition by using Dark Field imaging. The Twinned wires are also shown to have at least four segments in a cyclic [001] twinning orientation in simultaneous diffraction condition by comparing to a twinned structure constructed from simulations. Elemental analysis using Electron Energy Loss Spectroscopy and Energy Dispersive X-ray shows that the composition of the nanomaterials is mainly boron and carbon.
The role of the iron layer on the wafer is investigated to see how varying the thickness will affect the nanomaterials grown. It is successfully shown that an increase in the thickness of the iron layer results in a greater density of nanomaterials. However there is no great variation in the average diameter of the nanomaterials produced.
The absence of a visible signal for iron in the Elemental analysis of nanostructure covered silicon wafer shows that the amount of iron in the sample has decreased during the reaction. However iron is found in small amounts in droplet structures at the tips of nanomaterials this is different to work done on a similar system at 1100C. This suggests that the role of the iron in the growth of these nanomaterials at this temperature is not yet understood. However this work has confirmed that the iron is essential for the nucleation of the nanomaterials, but post nucleation growth that was previously assumed to be a conventional VLS growth may switch to an oxide assisted growth mode
Can NbO Keep nbo Topology under Electrons? –Unveiling Novel Aspects of Niobium Monoxide at the Atomic Scale
Full text linkA precise investigation of NbO has been carried out by advanced electron microscopy combined with powder and single crystal X-ray diffraction (XRD). The structure of pristine NbO has been determined as Pm-3 m space group (SG) with a = 4.211 Å and the positions of Nb and O at the 3c and 3d Wyckoff positions, respectively, which is consistent with previous report based on powder XRD data. Electron beams induced a structural transition, which was investigated and explained by combining electron diffraction and atomic-resolution imaging. The results revealed that the electron beam stimulated both Nb and O atom-migrations within each fcc sublattice, and that the final structure was SG Fm-3 m with a = 4.29 Å, Nb and O at the 4a and 4b with 75 % occupancy and same chemical composition. Antiphase planar defects were discovered in the pristine NbO and related to the structural transformation. Theoretical calculations performed by density functional theory (DFT) supported the experimental conclusions
Protection unit for wide bandgap power switching device and method for operating the wide bandgap power switching device
No full textThe invention relates to a method for operating a power switching device, particularly a wide bandgap power switching device, in a power application, particularly in a converter, comprising the steps of:- checking (S2) a transient voltage of or related to a voltage drop across the switching device (22, 23) against a predetermined first threshold (Vref1,UP, Vref1,LOW) ;- reducing (S3) conductivity of the switching device (22, 23) if it is determined that the value of the transient voltage exceeds the predetermined first threshold (Vref1,UP, Vref1,LOW);- after reducing the conductivity, checking (S4) the voltage drop across the switching device (22, 23);- deactivating (S5) the operation of the switching device (22, 23) if it is determined that the voltage drop is larger than a predetermined second threshold (Vref2,UP, Vref2,LOW).AVP-R-TTOAlternative title(s) : (de) Schutzeinheit für eine leistungsschaltvorrichtung mit breiter bandlücke und verfahren zum betrieb der leistungsschaltvorrichtung mit breiter bandlücke (fr) Unité de protection pour un dispositif de commutation de puissance à large bande interdite et procédé de fonctionnement du dispositif de commutation de puissance à large bande interdit
Centralized Short-Circuit Protection of SiC Modules Connected in Parallel
No full textDue to the low short circuit withstanding time, short-circuit protection (SCP) for SiC devices is challenging. The SCP is more difficult when multiple devices are connected in parallel, as the turn-off of one device locally may lead to the overstressing of others. To resolve this, a centralized SCP approach designed for parallel-connected devices is introduced. This method employs the instantaneous current from the common-source inductors in power modules as a key metric to simultaneously reduce the gate-source voltages across all devices. Additionally, the voltage drop across each power device is monitored to enable their timely turn-off. This two-stage strategy ensures a quick response and high noise immunity for SiC devices. The proposed approach, seamlessly integrated with the power converter's controller, has been experimentally validated in a three-phase converter.PE
Time-Conditioned Generative Modeling of Object-Centric Representations for Video Decomposition and Prediction
Full text linkWhen perceiving the world from multiple viewpoints, humans have the ability
to reason about the complete objects in a compositional manner even when an
object is completely occluded from certain viewpoints. Meanwhile, humans are
able to imagine novel views after observing multiple viewpoints. Recent
remarkable advances in multi-view object-centric learning still leaves some
unresolved problems: 1) The shapes of partially or completely occluded objects
can not be well reconstructed. 2) The novel viewpoint prediction depends on
expensive viewpoint annotations rather than implicit rules in view
representations. In this paper, we introduce a time-conditioned generative
model for videos. To reconstruct the complete shape of an object accurately, we
enhance the disentanglement between the latent representations of objects and
views, where the latent representations of time-conditioned views are jointly
inferred with a Transformer and then are input to a sequential extension of
Slot Attention to learn object-centric representations. In addition, Gaussian
processes are employed as priors of view latent variables for video generation
and novel-view prediction without viewpoint annotations. Experiments on
multiple datasets demonstrate that the proposed model can make object-centric
video decomposition, reconstruct the complete shapes of occluded objects, and
make novel-view predictions
Centralized Short-Circuit Protection of SiC Modules Connected in Parallel
No full textDue to the low short circuit withstanding time, short-circuit protection (SCP) for SiC devices is challenging. The SCP is more difficult when multiple devices are connected in parallel, as the turn-off of one device locally may lead to the overstressing of others. To resolve this, a centralized SCP approach designed for parallel-connected devices is introduced. This method employs the instantaneous current from the common-source inductors in power modules as a key metric to simultaneously reduce the gate-source voltages across all devices. Additionally, the voltage drop across each power device is monitored to enable their timely turn-off. This two-stage strategy ensures a quick response and high noise immunity for SiC devices. The proposed approach, seamlessly integrated with the power converter's controller, has been experimentally validated in a three-phase converter.</p
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