A Step Toward High Temperature Intelligent Power Modules Using 1.5kV SiC-BJT

International audienceLooking back to the development of inverters using SiC switches, it appears that SiC devices do not behave like their silicon counterparts. Their ability to operate at high temperature makes them attractive. Developing drivers suitable for 200˚C operation is not straightforward. In a perspective of high integration and large power density, it is wise to consider a monolithic integration of the driver parts for the sake of reliability. Silicon is not suitable for high ambient temperature; silicon-on-insulator offers better performances and presents industrial perspectives. The paper focuses on a SiC BJT driver: it processes logical orders from outside, drives adequately the BJT to turn it either on or off, monitors the turn-off and turn-on state of the device, and acts accordingly to prevent failure. SiC BJT imposes specific performances different from the well known ones of SiC JFET or MOSFET. The paper addresses a preliminary analysis of a SOI driver, anticipating the behavior of SiC-BJT and the change in behavior at high temperature. A discret driver as been design and fabricated. Elementary functionnal blocks have been validated, and a BJT conveter successfully operated at high temperature with high efficiency (η = 88%)

Avalanche Diodes with Low Temperature Dependence in 4H-SiC Suitable for Parallel Protection

International audienceAvalanche diodes have been fabricated on 4H-SiC substrate. These diodes show an abrupt avalanche voltage of about 59 V which corresponds to the calculated theoretical one using our previously determined impact ionization coefficients. This avalanche voltage increases by as small as 3.7 mV/K over the investigated temperature range (150K-420K)

Characterization of a 4H-SiC High Power Density Controlled Current Limiter

International audienceMost of silicon devices such as Schottky diode, MOSFET, MESFET have been realized in SiC and show good electrical and thermal characteristics [1]. Considering fault current limiters for serial protection, a lot of structures exists [2, 3], from conventional fuses to other complex systems such as circuit breakers, mechanical switches. Up to now, few specific SiC-current limiter were described [4, 5]. This paper presents experimental characterization of a bi-directional current limiter structure based on a vertical SiC VJFET

Characterization of a 4H-SiC High Power Density Controlled Current Limiter

International audienceCritical steps for the fabrication of SiC devices are thermal annealing and metal ohmic contact formation. Metal annealing effect on the electrical characteristics of the current limiter underlines the necessity to control this device fabrication step. Measurements of contact resistivity as a function of temperature demonstrate the stability of the N type Ni/SiC contact in the range of 175 K-450 K as its value remains constant around 40 µΩ.cm 2. Post implantation annealing effect on the sheet resistance (Rsh) shows that a 1700°C/30 min annealing gives better trade off in terms of dopant activation and surface roughness. High power density has been measured up to 600 V. Current thermal stability has been measured for an applied drain to source voltage of 100 V and exhibits high power density capabilities of SiC VJFET as a controlled current limiter. Introduction

Silicon Carbide Controlled Current Limiter, Current Limitation Strategies, Foreseen Applications and Benefits

International audienceThe expansion of electricity networks (distribution of energy, telecommunication), strongly contributed to increase the risks of appearance of defects, such as surge or overload. This multiplicity and complexity of electric networks, the need to have reliable systems favoured the development of serial protection devices. Fuse solution allows an efficient and total protection but requires to replace an element in case of failure. Therefore, other solutions have been investigated. Complex systems have been developed, all based on serial compensation, such as supra-conductor material, GTO MOV combination ... Indeed, because of the strong energy appearance during a short circuit, it is necessary to limit and to dissipate the energy of the short circuit, under high bias. This constraint leads to a feasibility study of a current limiter in 4H silicon carbide (4H-SiC). A VJFET structure was retained focusing on a nominal current of IN = 1 A and a nominal voltage of VN = 690 V. The device was optimised, taking into account SiC excellent physical properties. The VJFET was designed checking the trade-off between a low on-resistance value, high voltage capability and the highest gate transconductance value. A first batch of component was made, validating the bi-directional limitation function in both current and voltage mode, (VMAX = 970 V). The efficiency of the protection was validated, demonstrating the capacity of a component to react very quickly (t < 1 µs). Using such a device is very suitable in several applications (protection against short circuit, transient over current…) as it will allow to reduce transient phenomena and thus increase the efficiency and lifetime of the whole system

Hemiarthroplasty versus reverse shoulder arthroplasty in 4-part displaced fractures of the proximal humerus: Multicenter retrospective study

Introduction: Complex 4-part fractures of the proximal humerus are one of the most difficult fractures to manage. For several years, reverse total arthroplasty (RSA) has been proposed as an alternative to hemiarthroplasty (HA) when internal fixation is insufficient. The goal of this study was to compare the short and intermediate term results of these 2 different types of arthroplasty. Materials and methods: In a retrospective, multicenter study, 57HA and 41 RSA were reviewed after a follow-up of at least 2 years. The clinical evaluation was based on the absolute and adjusted Constant scores, Simple shoulder value (SSV) and the quick-DASH scores. The radiological assessment included standard radiological tests. Results: After a mean follow-up of 39 months, the RSA group had a significantly higher adjusted Constant score than the HA group (83% vs 73%, respectively P = 0.02). However, there was no significant difference in the absolute Constant score, the quick-DASH or the SSV scores. Active anterior elevation was better in the RSA group, while internal rotation was better in the HA group (130◦ vs 112◦, P = 0.01; sacrum vs L3, P = 0.03). There was no significant difference in external rotation (28◦ vs 23◦, P = 0.31). The rate of complications was higher in the HA group than in the RSA group (24% vs 10%, P = 0.01). The radiological rate of union of the greater tuberosity was similar in both groups (70%) and scapular notching was found in 23% of the RSA group. Conclusion: The short and intermediate term clinical outcomes are better with RSA than with HA. The complication rate is higher with HA. Nevertheless, scapular notching occurred in more than 20% of patients with RSA, suggesting that care should be taken when using this prosthesis in young, active patients

Four-part fractures treated with a reversed total shoulder prosthesis: Prospective and retrospective multicenter study. Results and complications

Introduction: The reversed shoulder prosthesis is becoming the gold standard for cases of complex fracture of the proximal humerus after 70 years of age. Material and methods: The French Society of Orthopaedic and Traumatology Surgery (SOFCOT) conducted a prospective and retrospective multicenter study to evaluate the results of the reversed shoulder prosthesis implanted in patients with a four-part fracture in nine centers. In the retrospective study (n = 41 patients, 78 years of age, 14% ASA grade 3, 21% associated fractures) and in the prospective study (n = 32 patients, 79 years of age, 37% ASA grade 3, 21% associated fractures) evaluation by independent surgeons was conducted to measure the QuickDASH score, the Constant score, the SSV (subjective shoulder value), and complications to correlate these measurements with radiological results. Results: In both studies, use of an autograft (75%) to perform an osteosuture of tuberosities (90%) and no postoperative immobilization (75%) were similar. In the retrospective study at 39 months (range: 24–62 months) of follow-up, the QuickDASH reached 28 (range: 0–59), the Constant scores (raw Constant = 57, weighted Constant = 83.4%), and SSV 75 (range: 35–100). Complications after the 1st month (7%) were nonunion or ossifications. In the prospective study at 11 months (range: 5–16.5 months) of follow-up, the QuickDASH reached 40 (range: 1–75), the Constant scores 50 (raw Constant) and 74.6% (weighted Constant), and SSV 69 (range: 10–100). Complications after the 1st month (21%) were stiffness and dislocation, with two patients who underwent revision surgery. In both studies, early complications reached 6% (palsy, dislocation). Conclusion: This double (retrospective and prospective) study confirms the good results with a low level of complications of the reversed implant in cases of fracture but with osteosuture of tuberosities

Formation par projet et opportunité d'accès à distance à des ressources pédagogiques

National audienceLorsque l'apprentissage par projet couvre plusieurs thématiques, il apparaît que les étudiants sont d'autant plus sensibles à la qualité des ressources mises à disposition et à leur disponibilité. L'évaluation des étudiants est contrastée entre leur plébiscite du contenu de la formation et leur critique des ressources. L'accès à distance à de telles ressources répond à une partie de la problématique. La communication décrit une première expérience de formation par projet qui débouche sur une mise à disposition à distance d'un lot de ressources, assistée d'une pédagogie adaptée. Fort de cette expérience, une seconde proposition est présentée dans un contexte différent mais où des contraintes similaires persistent sur les ressources. La discussion fera l'objet d'un poster avec démonstration sur machine (PR). Il est évident que les propositions mises en oeuvre sont maintenant connues, mais peu usitées en fait, et elles sont applicables à d'autres contextes. Si l'opportunité d'accessibilité à distance de ressources est une réponse à une partie importante des faiblesses des retours d'expérience décrits ici, il n'est pas envisagé de formation à distance, problématique très différente

Research Progresses in Understanding the Pathophysiology of Moyamoya Disease

Background: The pathogenesis of moyamoya disease (MMD) is still unknown. The detection of inflammatory molecules such as cytokines, chemokines and growth factors in MMD patients' biological fluids supports the hypothesis that an abnormal angiogenesis is implicated in MMD pathogenesis. However, it is unclear whether these anomalies are the consequences of the disease or rather causal factors as well as these mechanisms remain insufficient to explain the pathophysiology of MMD. The presence of a family history in about 9-15% of Asian patients, the highly variable incidence rate between different ethnic and sex groups and the age of onset support the role of genetic factors in MMD pathogenesis. However, although some genetic loci have been associated with MMD, few of them have been replicated in independent series. Recently, RNF213 gene was shown to be strongly associated with MMD occurrence with a founder effect in East Asian patients. However, the mechanisms leading from RNF213 mutations to MMD clinical features are still unknown. Summary: The research on pathogenic mechanism of MMD is in its infancy. MMD is probably a complex and heterogeneous disorder, including different phenotypes and genotypes, in which more than a single factor is implicated. Key Message: Since the diagnosis of MMD is rapidly increasing worldwide, the development of more efficient stratifying risk systems, including both clinical but also biological drivers became imperative to improve our ability of predict prognosis and to develop mechanism-tailored interventions. (C) 2016 S. Karger AG, BaselPeer reviewe