This diploma thesis deals with analysis of function and subsequent construction of a quasi-resonant DC / DC converter 300 V / 50 V for an output of about 1.5 kW. The aim of this work is to test and describe the behavior of an experimental converter at various operating parameters. In the theoretical part, resonant circuits are described, as well as our connection of the resonant converter. Based on the used topology and the simulated behavior of the converter, the individual components of the power circuit and its control and excitation circuit are designed in Chapters 4 and 5. The sixth chapter deals with the construction and testing of the converter, including a description of its behavior. The last chapter contains technical documentation.

The master's thesis covers in its first parts origins and consequnces of the switching losses, basic principles of the various resonant tanks and resonant DC/DC converters. Afterwards the innovative approach of the multiperiod modulation is presented. The main advantages of this kind of modulation include very wide zero current switching region and lowering the switching frequency as the output voltage decreases. In the remaining part of the thesis a prototype converter design is described.

This thesis deals with the issue of switching power supply in terms of noise ratios in the output voltage. In the theoretical part analyzes the basic principle of classical and resonant topology switching power converters in terms of output voltage ripple and switching noise. There are also some possibilities of compensation to minimize switching noise and output ripple. The second part describes the custom design a low noise switching power supply, which is composed of an active power factor corrector, power converters and ripple limiter. The main power converter is designed as an LLC resonant converter. The last part deals with the actual construction of the proposed source, its measurement and presentation of the results.

This master’s thesis deals with the design of the switching power supply on the principle of high frequency converter. The goal of this thesis is construction of converter which is using GaN MOSFET transistors and SiC diodes for switching. The converter uses two switch forward power supply topology. Unusually high switching frequency was chosen for the design with power transformer with open magnetic core. The outcome of this work is functional converter which is primarily intended for educational and demonstrational purposes. Multiple parts of this converter are divided into individual blocks, which can be further used for construction of other types of switching converters.

Le but de cette thèse est de concevoirun chargeur de véhicule électrique avec une fortedensité de puissance car il doit être embarqué dansle véhicule. La thèse se focalise sur le deuxièmeétage du chargeur qui comporte un transformateur.Cet élément représente une part importante du volumetotal du convertisseur.Pour réaliser cela, une nouvelle technologie de transistorsest utilisée : les transistors GaN. Ces composantsinduisent des pertes par commutation plusfaibles que les transistors classiquement utilisés cequi permet d’augmenter la fréquence de découpage.Cette fréquence est un levier pour améliorer la densitéde puissance des convertisseurs. Cependant lafréquence est également responsable de pertes dansd’autres composants comme le transformateur et lesinductances. Pour augmenter efficacement cette densité, la topologie du convertisseur doit être conçuepour réduire les contraintes sur ces composants.La thèse comporte trois parties. Tout d’abord, lecomportement des transistors GaN est évalué etdifférentes topologies sont analysées pour en déduireune structure de chargeur qui minimise les pertesdans le transformateur. Ensuite, un dimensionnementcompact de transformateur est réalisé à l’aide d’uneétude paramétrique et des simulations par élémentsfinis. Enfin, un prototype de ce deuxième étage duchargeur est réalisé et testé pour évaluer ses performanceset son volume / Improvement of power density is a bigchallenge for embedded electric vehicle chargers.Goal of the study is to reduce the volume of the DCDCcharger which contains a bulky transformer. Thekey point is to use wide band gap transistors (GaN) toincrease the charger switching frequency. High switchingfrequency can improve power density but theinconvenient is the increase of switching and transformerlosses. The PhD dissertation is organized inthree steps. First step is the definition of a charger topology.This topology is optimized to reduce transformerlosses. Second part of the study is the theoreticaldesign of a high power density transformer. A completetransformer parametric model is presented withFinite Element Analysis. Third part present the prototypeand test results of the charger DC-DC. Electricalbehavior, volume and efficiency results are discussedin this part.Universit ´

La transmission d’énergie par induction est devenue un sujet extrêmement porteur compte tenu du contexte géopolitique et environnemental du moment ; ainsi que des possibilités technologiques. Les enjeux de l’alimentation électrique d’un véhicule en roulant sont importants : réduction de la taille de la batterie embarquée, du poids et du coût du véhicule, limitation des importations de cellules de batteries et réduction des importations pétrolières au profit d’investissements locaux et extension du rayon d’action des véhicules électriques voire hybrides rechargeables pouvant aller d’un simple bonus à un rayon d’action infini selon le dimensionnement de l’infrastructure.La solution développée utilise le vecteur magnétique. Elle fait donc appel à des bobines faiblement couplés qui impliquent de fortes inductances de fuite et des chutes de tensions associées hors du commun. Un nouveau type de convertisseur « continu-continu » a été imaginé afin de répondre à ces contraintes. Celui-ci se fonde sur le concept de symétrie ; l’analyse détaillée basée sur les diagrammes de Fresnel, a conduit à l’élaboration d’un fonctionnement particulier qui a été appelé la « recopie de tension ». Le prototype réalisé fonctionne avec un entrefer réaliste de 15 centimètres, une tolérance au décentrage de +/-50% sur l’axe longitudinal, une tension de sortie stable avec de faibles pertes malgré d’importantes variations de couplage. Le tout sans aucune communication entre la partie au sol et la partie mobile. Ces résultats permettent d’envisager sérieusement un fonctionnement en roulant.Celui-ci nécessite de pouvoir séquencer l’alimentation d’une multitude de bobines de petite taille enfouies sous la chaussée, au bon moment et à la bonne position. La mise en court-circuit résonnant des bobines inactive permet d’utiliser la mesure des courants pour déterminer précisément l’instant d’activation de la bobine suivante. Cette solution originale, qui s’affranchi de tout capteur de position, conserve la propriété de recopie de tension et le principe de dimensionnement développés dans la première partie. / Inductive power transfer has become a flourishing subject, considering the current geopolitical and environmental situation and the new technological possibilities. The electric road may lead to important and valuable consequences: extended range for electric vehicles and even hybrids, from a simple bonus to an infinite range, depending on the infrastructure set up, down-sized on-board batteries, reduction of the weight and cost of the vehicle and lowered importations of both battery cells and oil for the benefit of local investments .The solution developed uses a magnetic medium for the transfer. Therefore, it involves loosely coupled coils, implying inevitably strong leakage inductances and outstanding associated voltage drops. A new type of DC-DC converter was imagined to answer those issues. It is based on the concept of symmetry; a detailed analysis conducted with phasor diagrams leads to a specific working principle, which has been named the “voltage copying”. Thus, the DC/DC converter designed works with a realistic air-gap of 15 centimeters, a longitudinal tolerance to displacement up to +/-50% and a stable output voltage with low losses despite large coupling variations. And it all works without any communication between the ground part and the mobile part. These results make a dynamic charging seriously worth investigating.It requires to sequence the power supply of a multitude of small coils buried beneath the road surface, at the right time and for the right position. Putting inactive coils in a resonant short-circuit mode enables to use current measures to precisely detect the switching time from one coil to the next. This original solution, free of any position sensor, does not prevent the specific “voltage copying” property and the design principles developed in the first part.

With the development of information technology, power management for telecom and computer applications become a large market for power supply industries. To meet the performance and reliability requirement, distributed power system (DPS) is widely adopted for telecom and computer systems, because of its modularity, maintainability and high reliability. Due to limited space and increasing power consumption, power supplies for telecom and server systems are required to deliver more power with smaller volume. As the key component of DPS system, front-end AC/DC converter is under the pressure of continuously increasing power density. For conventional industry practices, some limitations prevents front-end converter meeting the power density requirement. In this dissertation, different techniques have been investigated to improve power density of front-end AC/DC converters. For PFC stage, at low switching frequency, PFC inductor size is large and limits the power density. Although increasing switching frequency can dramatically reduce PFC inductor size, EMI filter size might be larger at higher switching frequency because of the change of noise spectrum. Since the relationship between EMI filter size and PFC switching frequency is unclear for industry, PFC circuits always operate with switching frequency lower than 150 kHz. Based on the EMI filter design method, together with a simple EMI noise prediction model, relationship between EMI filter corner frequency and PFC switching frequency was revealed. The analysis shows that switching frequency of PFC circuit should be higher than 400 kHz, so that both PFC inductor and EMI filter size can be reduced. Although theoretical analysis and experimental results verify the benefits of high switching frequency PFC, it is essential to find a suitable topology that allows high switching frequency operation while maintains high efficiency. Three PFC topologies, single switch PFC, three-level PFC with range switch and dual Boost PFC, were evaluated with analysis and experiments. By using advanced semiconductor devices, together with proposed control methods, these topologies could achieve high efficiency at high switching frequency. Thus, the benefits of high frequency PFC can be realized. In front-end converter, large holdup time capacitor size is another barrier for power density improvement. To meet the holdup time requirement, bulky holdup time capacitor is normally used to provide energy during holdup time. Holdup time capacitor requirement can be reduced by using wider input voltage range DC/DC converte. Because LLC resonant converter can realized with input voltage range without sacrificing its normal operation efficiency, it becomes an attractive solution for DC/DC stage of front-end converters. Moreover, its small switching loss allows it operating at MHz switching frequency and achieves smaller passive component size. However, lack of design methodology makes the topology difficult to be implemented. An optimal design methodology for LLC resonant converter has been developed based on the analysis on the circuit during normal operation condition and holdup time. The design method is verified by a 1 MHz switching frequency LLC resonant converter with 76W/in3 power density. When front-end converter operates at high switching frequency, negative effects of circuit parasitics become more pronounced. By integrating active devices together with their gate drivers, Active Integrated power electronics module (IPEM) can largely reduce circuit parasitics. Therefore, switching loss and voltage stress on switching devices can be reduced. Moreover, IPEM concept can be extended into passive integration and EMI filter integration By using this power integration technology, power density and circuit performance of front-end converter can be improved, which is verified by theoretical analysis and experimental results. / Ph. D.

The advent of wide band-gap semiconductors in power electronics has led to the scope of efficient power conversion being pushed further than ever before. This development has allowed for systems to operate at higher and higher voltages than previously achieved. One area of consideration during this high voltage transition is the synchronous rectifier, which is traditionally designed as an afterthought. Prior research in synchronous rectifiers have been limited to low voltage, high current converters. There is practically no research in high voltage synchronous rectification. Therefore, this dissertation focuses on discovering the unknown nuances behind high voltage synchronous rectifier design, and ultimately developing a practical, scalable solution. There are three main issues that must be addressed when designing a high voltage synchronous rectifier: (1) high voltage sensing; (2) light load effects; (3) accuracy. The first hurdle to designing a high voltage SR system is the high voltage itself. Traditional methods of synchronous rectification (SR) attempt to directly sense voltage or current, which is not possible with high voltage. Therefore, a solution must be designed to limit the voltage seen by the sensing mechanism without sacrificing accuracy. In this dissertation, a novel blocking solution is proposed, analyzed, and tested to over 1-kV. The solution is practical enough to be implemented on practically any commercial drain-source SR controller. The second hurdle is the light load effect of the SR system on the converter. A large amount of high voltage systems utilize a LLC-based DC transformers (DCX) to provide an efficient means of energy conversion. The LLC-DCX's attractive attributes of soft-switching and high efficiency allure many architects to combine it with an SR system. However, direct implementation of SR on a LLC-DCX will result in a variety of light load oscillation issues, since the rectifier circuitry can excite the resonant tank through a false load transient phenomena. A universal limiting solution is proposed and analyzed, and is validated with a commercial SR controller. The final hurdle is in optimizing the SR system itself. There is an inherent flaw with drain-source sensing, namely parasitic inductance in the drain-source sense loop. This parasitic inductance causes an error in the sensed voltage, resulting in early SR turn-off and increased losses through the parallel diode. The parasitic will always be present in the circuit, and current solutions are too complex to be implemented. Two solutions are proposed depending on the rectifier architecture: (1) multilevel gate driving for single switch rectifiers; (2) sequential parallel switching for parallel switch rectifiers. In summary, this dissertation focuses on developing a practical and reliable high voltage SR solution for LLC-DCX converters. Three main issues are addressed: (1) high voltage sensing; (2) light load effects; (3) accuracy. Novel solutions are proposed for all three issues, and validated with commercial controllers. / Doctor of Philosophy / High voltage power electronics are becoming increasing popular in the electronics industry with the help of wide band-gap semiconductors. While high voltage power electronics research is prevalent, a key component of high voltage power converters, the synchronous rectifier, remains unexplored. Conventional synchronous rectifiers are implemented on high current circuits where diode losses are high. However, high voltage power electronics operate at much lower current levels, necessitating changes in current synchronous rectifier methods. This research aims to identify and tackle issues that will be faced by both systems and IC designers when attempting to implement high voltage synchronous rectifiers on LLC-DCXs. While development takes planes on a LLC-DCX, the research is applicable to most resonant converters and applications utilizing drain-source synchronous rectifier technology. This dissertation focuses primarily on three areas of synchronous rectifier developments: (1) high voltage compatibility; (2) light load effects; (3) accuracy. The first issue opens the gate to high voltage synchronous rectifier research, by allowing high voltage sensing. The second issue explores issues that high voltage synchronous rectifiers can inadvertently influence on the LLC-DCX itself - a light load oscillation issue. The third issue explores novel methods of improving the sensing accuracy to further reduce losses for a single and parallel switch rectifier. In each of these areas, the underlying problem is root-caused, analyzed, and a solution proposed. The overarching goal of this dissertation is to develop a practical, low-cost, universal synchronous rectifier system that can be scaled for commercial use.

The major achievements of this work are based on two categories: (A) introduction of an advanced simulation technique in both time domain and frequency domain, and (B) realistic and reliable models for converters applicable to analysis of alternative transmission systems. The proposed modeling-methodology using a combination of model quadratization and quadratic integration (QMQI) is demonstrated as a more robust, stable, and accurate method than previous modeling methodologies for power system analyses. The quadratic-integration method is free of artificial numerical-oscillations exhibited by trapezoidal integration (which is the most popularly used method in power system analyses). Artificial numerical oscillations can be the direct reason for switching malfunction of switching systems. However, the quadratic-integration method has a natural characteristic to eliminate fictitious oscillations with great simulation accuracy. Also, model quadratization permits nonlinear equations to be solved without simplification or approximation, leading to realistic models of nonlinearities. Therefore, the QMQI method is suitable for simulations of network systems with nonlinear components and switching subsystems. Realistic and reliable converter models by the application of the QMQI method can be used for advanced designs and optimization studies for alternative transmission systems; they can also be used to perform a comprehensive evaluation of the technical performance and economics of alternative transmission systems. For example, the converters can be used for comprehensive methodology for determining the optimal topology, kV-levels, etc. of alternative transmission systems for wind farms, for given distances of wind farms from major power grid substations. In this case, a comprehensive evaluation may help make more-informed decisions for the type of transmission (HVAC, HVDC, and LFAC) for wind farms.

Les dispositifs DBD se répandent dans un grand nombre d’applications industrielles. Utilisés depuis plus de 150 ans pour la production d’ozone afin de décontaminer l’eau à grande échelle, ils ont depuis la fin du XXème siècle investi les domaines du traitement de surface polymère, du dépôt de couche mince sur substrat et de l’émission lumineuse pour la décontamination ainsi que la médecine. Ces dispositifs sont mis en oeuvre avec un générateur électrique dont les caractéristiques impactent fortement la qualité de la décharge. Ce travail s’inscrit en partie dans le cadre du développement d’une application de traitement de surface à pression atmosphérique. Il aborde la problématique de l’augmentation de la vitesse de dépôt de couche mince au travers des paramètres de l’alimentation électrique. Plus précisément, ce travail s’intéresse aux apports d’une alimentation en courant rectangulaire et aborde également les problématiques liées à la conception et à la fabrication de ce convertisseur. En particulier, une grande attention est portée sur l’étude du transformateur élévateur, car au travers de ses éléments parasites capacitifs, ce dernier peut limiter le transfert de puissance entre la source électrique et le dispositif DBD. Un deuxième aspect de cette étude consiste à entrevoir l’intérêt que revêtent deux convertisseurs statiques dédiés à l’alimentation de dispositifs DBD. Le premier consiste en une alimentation résonante en régime de conduction discontinue dont la particularité est de posséder trois degrés de liberté (fréquence, tension d’entrée et largeur d’impulsion), ce qui lui confère un intérêt exploratoire. Le second convertisseur consiste en une alimentation résonante haute tension et haute fréquence permettant l’éviction du transformateur élévateur, et mettant en oeuvre des interrupteurs au nitrure de gallium (GaN) afin d’atteindre une fréquence de fonctionnement supérieure au mega-Hertz avec un faible niveau de pertes. / DBD devices are widely used in industrial applications. 150 years ago, they were only employed in ozoners for water decontamination. In recent decades, the progress of knowledge and technology allowed to use them in many other applications like surface treatment, medical applications and light emission. Actually, these devices are supplied with an electrical source which parameters can strongly impact the discharge behaviour. An important part of this work comes within the framework of the development of an atmospheric pressure surface treatment involving DBDs. The issue of the influence of the generator's electrical parameters on the treatment speed is discussed. In particular, this work focuses on the merits of a rectangular shaped current source concerning the behavior of an atmospheric pressure discharge in nitrogen ; the problems related to the design and the fabrication of such a converter are highlighted. The design of the high voltage transformer is then described in detail since its lumped elements play an important role as they can strongly limit the power transfer between the electrical source and the DBD device. A second aspect of this work is to establish the interests of two particular power converters. The first one is a resonant converter operating in a discontinuous conduction mode ; its merits is to exhibit three degrees of freedom (input voltage, frequency, current pulse width) instead of two, which is a tremendous asset for exploring purposes. The second one is a high-frequency resonant converter where a resonant inductance and the DBD device structural capacitances are used instead of a high voltage transformer to perform the voltage amplification, which circumvents the issue related to the transformer parasitic elements. This converter is based on GaN HEMT switches in order to reach a low semiconductor losses level and a fairly high operating frequency (above the mega-Hertz).