Experimental Comparison of Discrete Cascode GaN-GaN and Single e-GaN in High-Frequency Power Converter

International audienceThis paper describes the analysis and experimental test of a discrete cascode GaN-GaN intended for high-frequency power converters. The proposed configuration takes advantages of both the high switching frequency capabilities of GaN-HEMTs and the robustness of depletion-mode GaN devices. Experimental tests compare the designed cascode GaN-GaN with an equivalent single enhancement-mode GaN device. The test is carried out in a boost converter of 400V-400W-30MHz. This power converter topology allows comparing both configurations in a demanding hard-switching condition. Experimental results suggest that at high-power and high-frequency the proposed cascode configuration can lead to performance improvements in the power converter selected for the test. These improvements arise from the reduced Miller-effect and the lower gate current of the cascode GaN-GaN

Performance Analysis of RL Damper in GaN-Based High-Frequency Boost Converter

International audienceThis paper analyzes a high-frequency GaN-based boost converter considering an RL damper to mitigate critical oscillations. This work aims contributing with graphical correlations between power converter signals and root trajectories of the characteristic equation in the main oscillation loop. Results provide insights about the RL damper design to improve the power converter performance. A technical contribution shows that the highest efficiency depends on the lowest L and the highest R of the RL damper able to produce a damping operation. Additionally, simulation results demonstrate the improvement of the GaN-HEMT operation and reliability using an RL damper in a boost converter topology. An experimental GaN-based boost converter validates the developed study

Distributed electrothermal modeling methodology for MOS gated power devices simulations

Currently electro-thermal simulations performed with 3D FEM simulators like ANSYS or COMSOL Multiphysics are limited to an imposed current flow through resistive materials. However, in the case of power MOS gated transistors like VDMOS transistors or IGBT, the channel resistance evolves with the gate voltage. This phenomenon is usually neglected in ON-state applications but seems to be determinant in switching application. Furthermore all the MOS cells of the transistors are not at the same temperature. This paper deals with a methodology that could allow taking into account the impact of the gate control and the MOS cells current distribution during 3D FEM electro-thermal simulations

Worst Case Heavy Ion Testing Conditions for Normally Off GaN-Based High Electron Mobility Transistor

The paper presents two alternatives SEE testing conditions on GaN power devices to investigate for the worst case that are switching and high tilt beam condition. Results obtained are discussed with the help of TCAD modeling

Combined Bacterial Meningitis and Infective Endocarditis: When Should We Search for the Other When Either One is Diagnosed?

Auteurs groupes collaboratifs AEPEI study group & the COMBAT study groupInternational audienc

Characteristics, management, and prognosis of elderly patients with COVID-19 admitted in the ICU during the first wave: insights from the COVID-ICU study

International audienceBackground: The COVID-19 pandemic is a heavy burden in terms of health care resources. Future decision-making policies require consistent data on the management and prognosis of the older patients (> 70 years old) with COVID-19 admitted in the intensive care unit (ICU). Methods: Characteristics, management, and prognosis of critically ill old patients (> 70 years) were extracted from the international prospective COVID-ICU database. A propensity score weighted-comparison evaluated the impact of intubation upon admission on Day-90 mortality. Results: The analysis included 1199 (28% of the COVID-ICU cohort) patients (median [interquartile] age 74 [72–78] years). Fifty-three percent, 31%, and 16% were 70–74, 75–79, and over 80 years old, respectively. The most frequent comorbidities were chronic hypertension (62%), diabetes (30%), and chronic respiratory disease (25%). Median Clinical Frailty Scale was 3 (2–3). Upon admission, the PaO2/FiO2 ratio was 154 (105–222). 740 (62%) patients were intubated on Day-1 and eventually 938 (78%) during their ICU stay. Overall Day-90 mortality was 46% and reached 67% among the 193 patients over 80 years old. Mortality was higher in older patients, diabetics, and those with a lower PaO2/FiO2 ratio upon admission, cardiovascular dysfunction, and a shorter time between first symptoms and ICU admission. In propensity analysis, early intubation at ICU admission was associated with a significantly higher Day-90 mortality (42% vs 28%; hazard ratio 1.68; 95% CI 1.24–2.27; p < 0·001). Conclusion: Patients over 70 years old represented more than a quarter of the COVID-19 population admitted in the participating ICUs during the first wave. Day-90 mortality was 46%, with dismal outcomes reported for patients older than 80 years or those intubated upon ICU admission

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

BackgroundWe previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in similar to 80% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P=1.1x10(-4)) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70[95%CI 1.3-8.2], P=2.1x10(-4)). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR=19.65[95%CI 2.1-2635.4], P=3.4x10(-3)), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR=4.40[9%CI 2.3-8.4], P=7.7x10(-8)). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10(-5)).ConclusionsRare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old