Active gate switching control of IGBT to improve efficiency in high power density converters

Insulated gate bipolar transistor (IGBT) power semiconductors are widely employed in industrial applications. This power switch capability in high voltage blocking and high current-carrying has expanded its use in power electronics. However, efficiency improvement and reducing the size of products is one of main tasks of engineers in recent years. In order to achieve high-density power converters, attentions are focused on the use of fast IGBTs. Therefore, for achieving this desire the trend is designing more effective IGBT gate drivers. In gate drive (GD) controlling, the main issue is maintaining transient behavior of the MOS-channel switch in well condition; when it switches fast to reduce losses. It is well known that fast switching has a direct effect on the efficiency improvement; meanwhile, it is the major reason of appearing electromagnetic interference (EMI) problems in switched-mode power converters. Nowadays the most expectant of an active gate driver (AGD) is actively adjusting the switching transient through simple circuit implementation. Usually its performance is compared with the conventional gate driver (CGD) with fixed driving profile. As a result a proposed AGD has the capability of increasing the switching speed while minimizing the switching stress. Different novel active gate drivers (as feed-forward and closed-loop topologies) have been designed and analysed in this study. To improve the exist trade-off between switching losses and EMI problem, all effective factors on this trade-off are evaluated and considered in proposed solutions. Theoretical developments include proposed controlling methods and simulated efficiency of IGBTs switching control. The efficiency improvement has been pursued with considering EMI study in the proposed active gate controller. Experimental tests have been conducted to verify the design and validate the results. Beside technical aspects, cost study has also considered in the closed-loop GD. The proposed gate drivers are simple enough to allow its use in real industrial applications.Los semiconductores de potencia (IGBT) se emplean ampliamente en aplicaciones industriales. La capacidad de este interruptor de bloqueo en alta tensión y conducción de alta corriente ha ampliado su uso en la electrónica de potencia. Sin embargo, la mejora de la eficiencia y la reducción del tamaño de los convertidores de potencia es una de las tareas principales de los ingenieros de diseño. Para lograr convertidores de potencia de alta densidad y eficiencia, se requiere el uso de IGBT rápidos. Por lo tanto, la tendencia es diseñar controladores de puerta para IGBT más efectivos. En el control de la unidad de puerta (GD), el problema principal es mantener el comportamiento transitorio del conmutador del canal MOS bajo control, cuando conmuta a lata frecuencia para reducir las pérdidas. Es bien sabido que la conmutación rápida tiene un efecto directo en la mejora de la eficiencia; Sin embargo, la alta frecuencia de conmutación es la razón principal de la aparición de problemas de interferencia electromagnética (EMI) en los convertidores de potencia de modo conmutado. En la actualidad, la acción más directa para un controlador de puerta activo (AGD) consiste en el ajuste activo del transitorio de conmutación a través de la implementación de un circuito simple. Para evaluar su eficiencia, su rendimiento se compara con el controlador de puerta convencional (CGD) con perfil de conducción fijo. Los resultados muestran que la propuesta de AGD tiene la capacidad de aumentar la velocidad de conmutación mientras minimiza el stress. En este estudio se han diseñado y analizado diferentes controladores de puerta activa novedosos (como topologías de control en avance y de bucle cerrado). Para mejorar el balance existente entre la reducción de pérdidas y los problemas de EMI, todos los factores que afectan a las pérdidas y la EMI se evalúan y se consideran en las soluciones propuestas. Los desarrollos teóricos incluyen el análisis y desarrollo de los métodos de control propuestos, la simulación de la operación del control de conmutación del IGBT, y la validación experimental. Además de los aspectos técnicos de eficiencia y emisiones electromagnéticas, el estudio de costes también se ha considerado en los análisis de AGD. Los resultados muestran que los controladores de puerta propuestos son lo suficientemente eficientes y económicos como para permitir su uso en aplicaciones industriales realesPostprint (published version

Utilizing Microbiome Approaches for Antibiotic Resistance Analysis; an Ocular Case Evaluation

Background: Metaorganism or microbial communities of eukaryotic organisms provide an inclusive set of functions related to immunity, host metabolism, and stress tolerance. Ocular microbiota refers to pathogenic and commensal microorganisms in or on the eye. On the one hand, antibiotic treatment can give rise to pathogen overgrowth due to an imbalance of microbiota and cause various ophthalmic diseases. On the other, antibiotic therapy is considered the leading cause of antibiotic resistance. The present study aimed to describe the bacterial community changes following antibiotic treatment in the ocular surface microbiome. Material and Methods: In this scenario, we evaluated the composition of thirteen canine ocular microbiomes during treatment with a typical mixture of antibiotics, neomycin-polymyxin-bacitracin. Microbiome taxonomy and downstream bacterial richness and evenness were analyzed using microbiome bioinformatics platforms. Results: Accordingly, bacterial taxonomy at the level of phyla and genus was mapped, and alter of antibiotic resistance genes  werereported. An increase in the Staphylococcus genus traced during the time and one month following antibiotic treatment. Bacterial network, alpha, and beta diversity indicated a significant microbiota change at the genus level. Conclusion: This study highlights the effect of commonly used ocular antibiotics on commensal microbiota and the emergence of the antibiotic-resistant genus

A Simple Closed-Loop Active Gate Voltage Driver for Controlling diC/dt and dvCE/dt in IGBTs

The increase of the switching speed in power semiconductors leads to converters with better efficiency and high power density. On the other hand, fast switching generates some consequences like overshoots and higher switching transient, which provoke electromagnetic interference (EMI). This paper proposes a new closed-loop gate driver to improve switching trajectory in insulated gate bipolar transistors (IGBTs) at the hard switching condition. The proposed closed-loop gate driver is based on an active gate voltage control method, which deals with emitter voltage (VEe) for controlling diC/dt and gets feedback from the output voltage (vCE) in order to control dvCE/dt. The sampled voltage signals modify the profile of the applied gate voltage (vgg). As a result, the desired gate driver (GD) improves the switching transients with minimum switching loss. The operation principle and implementation of the controller in the GD are thoroughly described. It can be observed that the new GD controls both dvCE/dt and diC/dt accurately independent of the variable parameters. The new control method is verified by experimental results. As a current issue, the known trade-off between switching losses and EMI is improved by this simple and effective control method.Postprint (published version

A novel active gate driver for improving SiC MOSFET switching trajectory

The trend in power electronic applications is to reach higher power density and higher efficiency. Currently, the wide band-gap devices such as silicon carbide MOSFET (SiC MOSFET) are of great interest because they can work at higher switching frequency with low losses. The increase of the switching speed in power devices leads to high power density systems. However, this can generate problems such as overshoots, oscillations, additional losses, and electromagnetic interference (EMI). In this paper, a novel active gate driver (AGD) for improving the SiC MOSFET switching trajectory with high performance is presented. The AGD is an open-loop control system and its principle is based on gate energy decrease with a gate resistance increment during the Miller plateau effect on gate-source voltage. The proposed AGD has been designed and validated through experimental tests for high-frequency operation. Moreover, an EMI discussion and a performance analysis were realized for the AGD. The results show that the AGD can reduce the overshoots, oscillations, and losses without compromising the EMI. In addition, the AGD can control the turn-on and turn-off transitions separately, and it is suitable for working with asymmetrical supplies required by SiC MOSFETs.Postprint (author's final draft

Impact of Distribution Channel Innovation on the Performance of Small and Medium Enterprises

Impact of innovation in distribution channel functions on firm performance, particularly among export-oriented, agro-based small and medium enterprises (SMEs) is under researched. Based on this literature gap, the present study examines the impact of distribution channel innovation on SMEs performance in Indonesia. A total of 120 samples were collected from export-oriented, agro based manufacturing SMEs in Yogyakarta and the surrounding areas, Java. Using a regression analysis, the findings show that innovation in assortment, information sharing and transportation coordination had positive and significant relationships with firm performance. This study also found that distribution channel effectiveness mediated the relationship between innovation in assortment and transportation coordination and firm performance. All this finding is crucial for firms, who intend to remain competitive in the global market. Future studies, however, should consider many other factors that may influence firm performance in the agro-based industry.Key words: Distribution channel; Innovation; Effecti veness; Performance; SMEs; Indonesi

Advancing Compressive Strength Prediction in Self-Compacting Concrete via Soft Computing: A Robust Modeling Approach

Self-Compacting Concrete (SCC) is a unique type of concrete that can flow and fill spaces without the need for vibrating compaction, resulting in a dense and uniform material. This article focuses on predicting the compressive strength of SCC using Artificial Neural Networks. Specifically, the study employs multilayer perceptrons with back-propagation learning algorithms, which are commonly used in various problem-solving scenarios. The study covers essential components such as structure, algorithm, data preprocessing, over-fitting prevention, and sensitivity analysis in MLPs. The input variables considered in the research include cement, limestone powder, fly ash, ground granulated blast furnace slag, silica fume, rice husk ash, coarse aggregate, fine aggregate, water, super-plasticizer, and viscosity-modifying admixtures. The target variable is the compressive strength. Through a sensitivity analysis, the study evaluates the relative importance of each parameter. The results demonstrate that the AI-based model accurately predicts the compressive strength of self-compacting concrete

Translation, Linguistic Validation, and Cultural Adaptation of the Bladder Cancer Index (BCI) Questionnaire Into the Persian (Farsi) Language and Comparing it With WHO Quality of Life Questionnaire: An Observational Study

Objective: Whether ileal conduit diversion (ICD) or orthotopic neobladder (ONB) urinary diversion provides better quality of life (QoL) is still under debate. The Bladder Cancer Index (BCI) is a specific tool for bladder cancer (BCa) patients, providing reliable results in previous studies. A validated Farsi version of the BCI concerning cultural aspects could help Farsi-speaking clinicians gain more reliable feedback on QoL following urinary diversion. Materials and methods: Based on WHO suggestions, we translated the BCI questionnaire into the Persian language. Then, we performed a cross-sectional study on BCa patients who underwent ICD or ONB urinary diversion. We compared their QoL via BCI and WHO questionnaires. Chi-square and independent t-tests were used where appropriate. Results: The content validity ratio and the content validity indexes were 1 and 0.8-1.0, respectively. Of 57 participants, six patients (10.5%) were women. The ICD was performed for 38 (66.7%) and ONB diversion for 19 (33.3) participants. The mean age of ICD and ONB was 68.71 ± 7.40 and 64.28 ± 8.34 years, respectively (p-value: 0.055). In all sub-domains of BCI, except bowel habits, the mean scores were higher in the ICD group. A significant difference between ICD and ONB groups was found regarding urinary function (p-value<0.001). There was no significant difference between ICD and ONB groups in none of the domains of the WHO questionnaire. Conclusion: The QoL of ICD and ONB patients did not differ significantly. Even ICD may be superior in ritual purification, while the psychological status of ONB patients was better.

Sentinel lymph node biopsy in upper tract urothelial cancers: an experience with intraoperative radiotracer injection

Background: The feasibility of the sentinel node mapping in upper tract urothelial cancers (UTUC) was evaluated, using a radiotracer as the mapping material. Material and methods: To identify the sentinel lymph nodes, 37 MBq of [99mTc] phytate was injected in five patients with the renal pelvis or ureter cancer, who were candidates for ureterectomy and lymphadenectomy. The radiotracer was injected in a peritumoral fashion following the surgical exposure of the tumour. The sentinel lymph nodes were detected using a handheld gamma probe. Results: By intraoperatively injecting the radiotracer immediately after surgical exposure of the tumour, at least one sentinel lymph node could be detected in each patient, and the detection rate was 100%. The location of sentinel nodes was in the paracaval, renal hill, retro-aortic, para-aortic, common iliac, and external iliac areas, which was dependent on the tumour location. No false-negative case was identified. Conclusions: Sentinel node mapping is feasible in UTUC. Injection technique (intra-vesical approach vs peri-tumoral injection after exposure of the tumour) and location of the tumour (proximal vs distal) may affect the technique’s feasibility