Self-Heating Induced Instability of a Non-Linear Inductor in a SMPS: a Case Study

This paper proposes a case study to show that the non-linear operation of a power inductor in a SMPS can induce instability of the control system leading to overheating of the inductor beyond its allowable temperature and to an excessive peak of the maximum current. The case study is performed by a commercial ferrite inductor employed in a synchronous boost converter encompassing a control system to adjust the duty cycle, assuring a constant output voltage. The thermal transient is described by the time domain waveforms and thermal images

GaN and SiC Device Characterization by a Dedicated Embedded Measurement System

This work proposes a comparison among GaN and SiC device main parameters measured with a dedicated and low-cost embedded system, employing an STM32 microcontroller designed to the purpose. The system has the advantage to avoid the use of expensive laboratory measurement equipment to test the devices, allowing to obtain their behavior in operating conditions. The following KPIs (Key Performance Indicators) are measured and critically compared: threshold voltage, on-resistance and input capacitance. All the measurements are carried out in a short time interval and on a wide range of switching frequencies, ranging from 10 kHz to 1 MHz. This investigation is focused on the deviation of the figures of merit when the switching frequency changes, since it is crucial for wide-bandgap devices. The devised, low-cost, microcontroller unit allows high flexibility and system portability, while the employed equivalent-time sampling technique overcomes some issues related to the need of high sampling frequency. It allows good performances with common microcontroller embedded AD converters. To validate the proposed system, the obtained results have been compared with the time-domain waveforms acquired with a traditional laboratory oscilloscope and a study of the system’s measurement errors has been carried out. Results show that GaN devices achieve a higher efficiency with respect to SiC devices in the considered range of switching frequencies. The on-resistance exhibited by GaN devices shows, as expected, an increase with frequency, which happens to switching losses, too. On the other hand, GaN devices are more sensitive to parasitic effects and the high dV/dt, due to the reduced switching times, can excite unwanted ringing phenomena

NON-LINEAR INDUCTOR CONTRIBUTION TO HARMONIC SPECTRUM IN POWER CONVERTERS

The paper investigates the harmonic content in DC/DC power converters where the inductor is operated in the non-linear region. This operation is often exploited to use lighter and cheaper inductors; as a drawback, an increasing number of harmonics is noticeable. A theoretical analysis is proposed. It is based on a polynomial model of the inductor used in a boost converter. Results are given by the spectra of the output voltage performed on a circuit prototype

Non-Linear Inductors Characterization in Real Operating Conditions for Power Density Optimization in SMPS

The exploitation of power inductors outside their linear region in switching converters can be achieved by raising the current until a decrease in the inductance can be noticed. This allows using a smaller magnetic core, increasing the power density of the converter. On the other hand, a detailed description of the magnetization curve including the temperature is required. Since this information is often not included in the inductor’s datasheets, this paper shows how to identify the behavior of an inductor when it is operated up to saturation and its temperature rises. In order to characterize the inductor in real operating conditions, a dedicated measurement rig was developed. It consists of a switching converter that encompasses the inductor under test and is controlled by a virtual instrument developed in LabVIEW. The characterization system was tested by retrieving the inductance and the magnetization curves vs. current for two commercial inductors at core temperatures up to 105 °C. The magnetic core was then characterized by the saturation current vs. inductance, obtaining an expression for the whole family of inductors sharing the same core. Finally, we experimentally analyzed the thermal transient of the inductors in operating conditions, confirming the fundamental role of the temperature in changing the current profiles and the core saturation condition

Molecular Analysis of Prothrombotic Gene Variants in Venous Thrombosis: A Potential Role for Sex and Thrombotic Localization

Background: Requests to test for thrombophilia in the clinical context are often not evidence-based. Aim: To define the role of a series of prothrombotic gene variants in a large population of patients with different venous thromboembolic diseases. Methods: We studied Factor V Leiden (FVL), FVR2, FII G20210A, Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, beta-fibrinogen -455 G>A, FXIII V34L, and HPA-1 L33P variants and PAI-1 4G/5G alleles in 343 male and female patients with deep vein thrombosis (DVT), 164 with pulmonary embolism (PE), 126 with superficial vein thrombosis (SVT), 118 with portal vein thrombosis (PVT), 75 with cerebral vein thrombosis (CVT) and 119 with retinal vein thrombosis (RVT), and compared them with the corresponding variants and alleles in 430 subjects from the general population. Results: About 40% of patients with DVT, PE and SVT had at least one prothrombotic gene variant, such as FVL, FVR2 and FII G20210A, and a statistically significant association with the event was found in males with a history of PE. In patients with a history of PVT or CVT, the FII G20210A variant was more frequent, particularly in females. In contrast, a poor association was found between RVT and prothrombotic risk factors, confirming that local vascular factors have a key role in this thrombotic event. Conclusions: Only FVL, FVR2 and FII G20210A are related to vein thrombotic disease. Other gene variants, often requested for testing in the clinical context, do not differ significantly between cases and controls. Evidence of a sex difference for some variants, once confirmed in larger populations, may help to promote sex-specific prevention of such diseases

Progress in Violet Light-Emitting Diodes Based on ZnO/GaN Heterojunction

Progress in light-emitting diodes (LEDs) based on ZnO/GaN heterojunctions has run into several obstacles during the last twenty years. While both the energy bandgap and lattice parameter of the two semiconductors are favorable to the development of such devices, other features related to the electrical and structural properties of the GaN layer prevent an efficient radiative recombination. This work illustrates some advances made on ZnO/GaN-based LEDs, by using high-thickness GaN layers for the p-region of the device and an ad hoc device topology. Heterojunction LEDs consist of a quasicoalesced non-intentionally doped ZnO nanorod layer deposited by chemical bath deposition onto a metal–organic vapor-phase epitaxy -grown epitaxial layer of p-doped GaN. Circular 200 μm-sized violet-emitting LEDs with a p-n contact distance as low as 3 μm exhibit a turn-on voltage of 3 V, and an emitting optical power at 395 nm of a few microwatts. Electroluminescence spectrum investigation shows that the emissive process can be ascribed to four different recombination transitions, dominated by the electron-hole recombinations on the ZnO side

Intralabyrinthine Schwannoma of the Intravestibular Subtype: A Difficult Diagnosis

Intralabyrinthine schwannoma is a rare, slow-growing, benign tumor that affects the most terminal portions of the vestibular and cochlear nerves. It can be located in the vestibule, cochlea, or semicircular canals. In 2004, Kennedy et al proposed a classification system which recognized 7 subtypes of intralabyrinthine schwannoma; in 2013, Abel et al1 modified the Kennedy classification,2 which included intracochlear, intravestibular (IV), intravestibulocochlear, transmodiolar, transmacular, transotic, and tympanolabyrinthine, to also include translabyrinthine, tumors extending into the CPA, and tumors not otherwise specified. They also proposed to rename intralabyrinthine schwannoma as primary inner ear schwannoma to permit clear subsite categorization. Patients usually have nonspecific symptoms, including hearing loss, tinnitus, and only single episode of vertigo. Among the resulting symptoms, the most frequent is hearing loss, which affects 95% of the patients. Most times, this loss is slow and progressive, but it may be sudden or fluctuating. Less common symptoms include tinnitus (51%), imbalance (35%), vertigo (22%), and ear fullness (2%), which may be present alone or in combination.3-7 We report a rare case of a patient with hearing loss and single episode of vertigo secondary to the intralabyrinthine schwannoma of the IV subtype

Implementation and Comparison of SiC and GaN switches for EV Fast Recharging Systems

Wide bandgap material-based devices allow faster switching frequency and exhibit smaller losses than traditional Si devices; nevertheless, a complete understanding of the functioning of these new devices remains poorly understood. A fast battery charger for electric vehicles based on a converter employing SiC and GaN devices is here reported Besides, these two technologies are experimentally compared, in the same layout, to highlights their performance in terms of electrical dynamic and electromagnetic compatibility

Immunohistochemical localization and mRNA expression of matrix Gla protein and fetuin-A in bone biopsies of hemodialysis patients

n/

The role of nasal washes in CF patients affected by chronic rhinosinusitis

Cystic Fibrosis (CF) presents multiorgan manifestations that include chronic rhinosinusitis (CRS) with or without nasal polyposis. Nasal washes (NWs) are widely used in clinical practice especially in CF patients, although their effectiveness on Ear Nose Throat (ENT) symptoms is controversial. In this study we evaluate the performance and the safety of a NWs solution, with or without surfactant, to reduce symptoms and bacterial load. Materials and methods We enrolled 20 CF patients (mean age: 27,6 years) with CRS, confirmed by nasal endoscopy. All patients, colonized by Pseudomonas Aeruginosa, performed daily a NW by physiological solution or by saline solution with surfactant (Naridek). All patients, at the time of enrollment, filled out a sinonasal questionnaire (SANQ11) and they received instructions for proper washing. During follow-up, we evaluated the reduction of the bacterial load in the nasal lavage. We assess the nasal cavities by endoscopy (2.7 mm 30° rigid endoscope - Storz, Tuttlingen, Germany) according to a modified Lund Kennedy endoscopic scoring system: - rhinorrhea (present = 0, mild = 1, purulent = 2); - edema, and hyperemia (absent = 0, mild = 1 or severe =2) - nasal mucosa (eutrophic = 1; hyperemic = 2; dystrophic = 3); - left and right turbinate hypertrophy (none = 0; mild = 1; medium = 2; and serious = 3). All subjects underwent the Sniffin’Sticks to evaluate the olfactory performance. Results Twelve patients completed 4 months of treatment: 6 patients performed the treatment with Naridek and 6 patients with physiological solution. Due to the small sample size, the scores were added together to have an overall indication of the treatment. (Table1) Nasal endoscopy ENT signs score Olfactory performance SNAQ 11 Naridek V1 80 72* 169 197** Naridek V4 15* 15* 159 98** Physiological solution V1 68 61 151 166 Physiological solution V4 52 39 159 152 *P<0.05 ** p< 0,01 The bacterial colonization in NWs shows no statistically significant difference. However, in 2 patients, we detected a reduction of the bacterial load. While there was no difference in the saline-treated group. Conclusions Considering our small sample we can only draw some great deal to think about: - treatment with NWs allows an improvement of the ENT symptoms and is well tolerated by patients. These data are confirmed by the ENT signs score and by the reduction of the SNAQ11 score in both treatment arms; - the solution with surfactant (Naridek) significantly improves the ENT signs and decreases the nasal endoscopy and the SNAQ11 scores; - no benefit was detected at the evaluation of olfactory performance. In conclusion, even if further confirmations are necessary on broader cases, it seems to emerge as significant the role of surfactant in the therapeutic advantage of NWs