Dissertations / Theses on the topic 'Planar transformers'

Over the last decade, fossil fuel prices have significantly increased due to the dependency on hydrocarbon energy sources for transportation and electricity generation. In order to solve power generation issues, most governments in the world have heavily promoted the installation of roof top solar photovoltaic (PV) in domestic low voltage and commercial high voltage distribution networks. In addition, Electric Vehicles (EVs) have been introduced to substitute the hydrocarbon fuelled transportation which is required to provide high mileage and affordable prices. Currently, EVs have been charged with the utilisation of plug-in AC and DC chargers to charge their battery bank. To expand their range, EVs are required to have larger energy storage batteries, which leads to higher costs and limits their adoption in society. Furthermore, plug-in chargers require manual operation to connect to EVs, which may create health and safety issues such as electric shock and fire. Wireless Charging Systems (WCS) have the potential to minimise both these major concerns by offering frequent charge while the EV is in stationary or dynamic modes. Frequent charge to the EVs at the car park, traffic signal and on the roads brings indefinite charging options which can dramatically reduce the battery bank size. However, improvements in some of the challenging factors such as health and safety, power levels and power efficiency requires further investigation to create a user-friendliness of the WCS for EVs. This thesis deals with the investigation of concerning issues which are limiting the development of Wireless Electric Vehicle Charging Systems (WEVCS) from becoming a part of the electrified transportation system. Currently available wireless power transfer technology for the EVs has been studied including wireless transformer structures with a variety of ferrite shapes. WEVCS are associated with many health and safety issues, which have been discussed with the current developments in international standards. Two major applications; static and dynamic WEVCS, have been explained with up-to-date progress from research laboratories, universities and industries. A variety of laboratory prototypes have been developed with the help of calculation and simulation methods, and verified with experimental techniques. Firstly, High Frequency Wireless Planar Transformers (HFWPT) are used to investigate the flux leakages and other electromagnetic compatibility (EMC) problems which are associated with the wireless charging system’s efficiency. The HFWPT was designed using the bifilar winding concept on a PCB. An LLC resonant converter has been designed to improve the conversion efficiency with a maximized air gap. Assisted by a near-field scanner, the magnetic field has been analysed with and without a magnetic ferrite core at resonant frequency. The magnetic ferrite core in this arrangement is used to minimize flux leakages and to increase the magnetizing impedance. In addition, EMC computer modeling and simulation techniques are employed to investigate the magnetic flux distribution and associated EMC problems such as stray fluxes and hot spots. A finite element method (FEM) has been used to calculate the magnetic field. The effect of the planar magnetic ferrite cores on magnetic flux distribution has been investigated by using three designs. The first design has the ferrite core only at the primary side, the second draft has a planar core on the primary and secondary side, and the third design has a U-shape magnetic core for the primary and secondary side. A new proposed design is introduced to minimize flux leakages and reduce hot spots, in order to improve the flux distribution and to increase the magnetizing impedance. Poor considerations of leakage flux between the primary and secondary coils may cause complications for persons with a pacemaker or any other life supporting electronic devices. Two scenarios are investigated via computational simulation. Firstly, a simulation of a person with an electronic biomedical implant device standing beside a car during the charging process through the WCS is investigated. Secondly, a person is walking or standing over the primary coil area of the WCS when the system is not in charging mode. Both of these scenarios include an investigation of four different versions of magnetic core configurations, to examine the outer magnetic flux distribution as well as the power distribution of the WCS by using a FEM simulation. Another concerning issue is the lower power transfer efficiency of WCS for EVs in comparison to the plug-in due to the poor coupling between the transmitter and receiver charging pads. In order to solve the problem, in-wheel WCS for EVs have been introduced with a concept proven laboratory prototype, which can operate in static and dynamic applications. The coupling coefficient is dependent on the thickness of the tire rubber and the transmitter installation height underneath the road surface. A variety of scenarios have been applied to study the in-build steel belt (IBSB) tire effect on the wireless power transfer for the static and dynamic cases. FEM simulation has been performed to investigate the magnetic flux distribution and leakage fluxes due to IBSB in the vehicle’s tire. Finally, the Wireless Vehicle to Grid (W-V2G) concept has been presented to solve future instability issues on the distribution networks created by unscheduled feedback power from renewable energy sources (RES). In addition, W-V2G can provide a platform to transfer power wirelessly in both directions: grid to vehicle and vehicle to grid where the EV’s battery can be a back-up of additional energy storage to reduce the peak demand energy requirements. A 3.7 kW wireless transformer for a single phase W-V2G prototype, and a high efficiency compact filter inductor for a D-StatCom inverter in the three phase 30 kVA W-V2G have been built with the utilisation of calculation and simulation methods. Both prototypes have been constructed and validated with experimental methods. Currently, a 3.7 kW W-V2G prototype is under development, and will be finished in future with complete systems analysis and results.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Eng & Built Env<br>Science, Environment, Engineering and Technology<br>Full Text

The object of the study is a superconducting film magnetic flux transformer comprising two square shaped loops with the tapering active strips and a magnetosensitive film element between them. It is shown that splitting of the active strips into parallel micro- and nanosized superconducting branches and slits increases the gain factor of the transformer, i. е., the concentration of an external magnetic field on the magnetosensitive element, by a factor of more than six. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35455

This report presents a project that has been made to present the design of a planar transformer as a part of a series loaded resonant DC/DC converter in a power unit. The design is based on an existing transformer that is not planar and so the characteristics of the transformer is translated into a planar version. A multilayer printed circuit board (PCB) design was made to fit a chosen magnetic ferrite core that was chosen based on the magnetic characteristics of the old core. Calculations were made for the loss of both core and windings and the final results show that it is possible to design a planar transformer from a traditional transformer.

The increased power consumption and power density demands of modern technologies have increased the technical requirements of DC/DC and AC/DC power supplies. In this regard, the primary objective of the power supply researcher/engineer is to build energy efficient, high power density converters by reducing the losses and increasing the switching frequency of converters respectively. Operating the converter circuits at higher switching frequencies reduces the size of the passive components such as transformers, inductors, and capacitors, which results in a compact size, weight, and increased power density of the converter. Therefore, the thesis work is focussed on the design, analysis and evaluation of isolated converters operating in the 1 - 5MHz frequency region with the assistance of the latest semi conductor devices, both coreless and core based planar power transformers designed in Mid Sweden University and which are suitable for consumer applications of varying power levels ranging from 1 – 60W. In high frequency converter circuits, since the MOSFET gate driver plays a prominent role, different commercially available MOSFET gate drivers were evaluated in the frequency range of 1 - 5MHz in terms of gate drive power consumption, rise/fall times and electromagnetic interference (EMI) and a suitable driver was proposed. Initially, the research was focused on the design and evaluation of a quasi resonant flyback converter using a multilayered coreless PCB step down transformer in the frequency range of 2.7 – 4MHz up to the power level of 10W. The energy efficiency of this converter is found to be 72 - 84% under zero voltage switching conditions (ZVS). In order to further improve the energy efficiency of the converter in the MHz frequency region, the new material device GaN HEMT was considered. The comparisons were made on a quasi resonant flyback DC-DC converter using both the Si and GaN technology and it was found that an energy efficiency improvement of 8 – 10% was obtained with the GaN device in the frequency range of 3.2 – 5MHz. In order to minimize the gate drive power consumption, switching losses and to increase the frequency of the converter in some applications such as laptop adapters, set top box (STB) etc., a cascode flyback converter using a low voltage GaN HEMT and a high voltage Si MOSFET was designed and evaluated using a multi-layered coreless PCB transformer in the MHz frequency region. Both the simulation and experimental results have shown that, with the assistance of the cascode flyback converter, the switching speeds of the converter can be increased with the benefit of obtaining a significant improvement in the energy efficiency as compared to that for the single switch flyback converter. In order to further maximize the utilization of the transformer, to reduce the voltage stress on MOSFETs and to obtain the maximum power density from the converter circuit, double ended topologies were considered. Due to the lack of high voltage high side gate drivers in the MHz frequency region, a gate drive circuitry utilizing the multi-layered coreless PCB signal transformer was designed and evaluated in both a half-bridge and series resonant converter (SRC). It was found that the gate drive power consumption using this transformer was around 0.66W for the frequency range of 1.5 - v 3.75 MHz. In addition, by using this gate drive circuitry, the maximum energy efficiency of the SRC using multilayered coreless PCB power transformer was found to be 86.5% with an output power of 36.5W in the switching frequency range of 2 – 3MHz. In order to further enhance the energy efficiency of the converter to more than 90%, investigations were carried out by using the multiresonant converter topology (LCC and LLC), novel hybrid core high frequency planar power transformer and the GaN HEMTs. The simulated and experimental results of the designed LCC resonant converter show that it is feasible to obtain higher energy efficiency isolated DC/DC converters in the MHz frequency region. The peak energy efficiency of the LCC converter at 3.5MHz is reported to be 92% using synchronous rectification. Different modulation techniques were implemented to regulate the converter for both line and load variations using a digital controller. In order to realize an AC/DC converter suitable for a laptop adapter application, consideration was given to the low line of the universal input voltage range due to the GaN switch limitation. The energy efficiency of the regulated converter operating in the frequency range of 2.8 – 3.5MHz is reported to be more than 90% with a load power of 45W and an output voltage of 22V dc. In order to determine an efficient power processing method on the secondary side of the converter, a comparison was made between diode rectification and synchronous rectification and optimal rectification was proposed for the converters operating in the MHz frequency range for a given power transfer application. In order to maintain high energy efficiency for a wide load range and to maintain the narrow switching frequency range for the given input voltage specifications, the LLC resonant converter has been designed and evaluated for the adapter application. From the observed results, the energy efficiency of the LLC resonant converter is maintained at a high level for a wide load range as compared to that for the LCC resonant converter. Investigations were also carried out on isolated class E resonant DC-DC converter with the assistance of GaN HEMT and a high performance planar power transformer at the switching frequency of 5MHz. The simulated energy efficiency of the converter for the output power level of 16W is obtained as 88.5% which makes it feasible to utilize the designed isolated converter for various applications that require light weight and low profile converters. In conclusion, the research in this dissertation has addressed various issues related to high frequency isolated converters and has proposed solution by designing highly energy efficient converters to meet the current industrial trends by using coreless and core based planar transformer technologies along with the assistance of GaN HEMTs. With the provided solution, in the near future, it is feasible to realize low profile, high power density DC/DC and AC/DC converters operating in MHz frequency region suitable for various applications.<br>High Frequency Switch Mode Power Supplies

Over the recent years many people have been trying to reduce the size and weight of magnetic components and thus the overall system [ 19 ]. One attempt at this is to increase the switching frequency of the system. However, this attempt has its limitations due to increased device switching losses. Device limitations usually confine this frequency to lower value than is desired. An effective approach, reducing the size and weight is to use the planar magnetics for possible integration with the power circuit and thus eliminating the associated interconnections. Planar magnetics uses the printed circuit board as the windings. This will allow the magnetic component to be implemented into the circuit. The integration of the magnetic components and power circuit will decrease the number of connections, reduce the height, and ensure the parasitic repeatability. Having external connections can cause problems in the system. In this case the system must carry a large amount of current. The connections can cause heating from resistance and inductance of the connection. The planar approach also will decrease the height of the system. This is because the planar magnetic cores have a higher surface area with a decreased height. This can reduce the height of the system by 25 %- 50 % [ 19 ]. The parasitic repeatability is also a very important factor. In many cases the typology relies on the parasitic elements for energy storage. Since, the parasitic elements are mainly a result from the geometry of the system; and the planar system has the windings made from the printed circuit board, the parasitic elements will be very consistent through the manufacturing process. For topologies that rely on the parasitic elements for soft switching, the planar design can incorporate parasitic elements with the leakage components for the soft-switching requirement. This thesis redefines the conventional term of leakage inductance as the sum of a set of lumped parasitic inductances and the transformer leakage inductance for the integrated planar magnetics and inverter power circuitry. For the conventional non-integrated transformer, either planar or non-planar, the leakage inductance is defined between two terminals of the transformer. However, for the integrated planar magnetics, the new lumped parasitic and leakage inductance should include the inverter switch and dc bus interconnections. The transformer was first designed using a closed-form solution for a known geometry with different copper thickness. The calculated leakage inductance was then verified with finite element analysis and the impedance analyzer measurement. It was found that the theoretical calculation and the finite element analysis results agreed very well, but the measurement was more than one order of magnitude higher. This prompted the study of interconnect parasitics. With geometrical structure and proper termination and lumping, a set of parasitic inductances were defined, and the results were verified with measurements of both impedance analyzer and phase-shifted modulated full-bridge inverter testing. In addition to parasitic inductance analysis, the flux distribution and associated thermal performance of the planar structure were also studied with finite element analysis. The resulting plots of flux distribution and temperature profile indicate the key locations of mechanical mounting and heat sinking. Overall the thesis covers essential design considerations in electrical, mechanical, and thermal aspects for the planar magnetics integration.<br>Master of Science

Ce travail concerne la conception, la réalisation et la caractérisation d’un transformateur de commande pour interrupteurs de puissance à grille isolée, le transformateur assurant l’isolation galvanique entre étage de commande et circuit de puissance. L’objectif du travail n’était pas de répondre à un cahier des charges précis mais de développer une nouvelle voie technologique pour la réalisation de transformateur planaire intégrable. Les principales caractéristiques d’un tel transformateur sont : - une inductance élevée (rapport inductance/surface occupée le plus grand possible) ; - des résistances séries faibles ; - un couplage capacitif entre primaire et secondaire le plus faible possible. Ces contraintes nous ont conduits à étudier un transformateur planaire à couches magnétiques dont les enroulements primaire et secondaire sont enterrés dans le matériau magnétique afin de réduire l’entrefer. La structure Face to Face a été retenue avec un décalage de 45° entre enroulements primaire et secondaire. Après une étude en simulation, chaque enroulement enterré dans un matériau ferrite a été réalisé séparément puis assemblé pour donner naissance au transformateur. De très nombreuses étapes technologiques : micro usinage laser femtoseconde, dépôts de cuivre par pulvérisation cathodique, photolithographie, planarisation, gravure chimique … ont été mises en oeuvre. Le transformateur ainsi réalisé est constitué d’un empilement de couches magnétiques, conductrices et isolantes. Il a été caractérisé des très basses fréquences jusqu’à plusieurs dizaines de MHz. Les résultats de mesure obtenus sont proches des résultats de simulation, la bande passante du transformateur s’étendant de 20kHz à 7MHz<br>This work concerns the design, realization and characterization of a control transformer for insulated gate power switches, the transformer providing galvanic isolation between driving stage and power circuits. The aim of the work was not to respond to a precise specification but to develop a new technological path for the realization of an integrable planar transformer. The main characteristics of such transformer are: - high inductance (ratio of inductance / area occupied as large as possible); - low series resistances; - a capacitive coupling between primary and secondary as small as possible. These constraints guided us to study a planar transformer with magnetic layers whose primary and secondary windings are buried in the magnetic material in order to reduce the air gap. The Face to Face structure was chosen with a 45 ° offset between primary and secondary windings. After a numerical study, windings buried in a ferrite material were fabricated separately and then assembled to give rise to the transformer. Many technological steps: femtosecond laser micromachining, copper deposits by sputtering, photolithography, planarization, chemical etching ... have been implemented. Thus, the transformer produced consists of a stack of magnetic, conductive and insulating layers. It has been characterized from very low frequencies up to several tens of MHz. The measurement results obtained are close to simulation results, the bandwidth of the transformer extending from 20 kHz to 7 MHz

This master's thesis describes the development of switching power supply with planar transformer. Deals with selection of a suitable integrated circuit together with the topology, a purchase of prototype for the reference measurements and debugging its own power supply. Further design and implementation of planar transformer and in the final implementation, debugging, and measurment's its own prototype. Power supply was fully functional and reached the expected parameters.

This thesis focuses on the design issues of the multiple-output boost full-bridge converter, which is constructed by cascading the boost regulator with the inductor-less full-bridge converter. The design of the boost regulator has been proposed briefly with component selection and compensator design. After that, the inductor-less full-bridge converter is analyzed extensively. In the first place, the operation principle of the inductor-less full-bridge converter is introduced. Later, the effect of parasitic resistance and inductance is analyzed in an L-R series circuit model as step-response, which relates the drop of output voltage to the load current. Then, the effects of the dc blocking capacitor for the unbalanced load condition and unbalanced duty cycle are tackled. The theoretical results are compared with the experimental results and the simulation results to verify the relationship between the output voltage drop and load current. The overall efficiency of the converter is tested under various conditions. <p> The design of the planar transformer is critical to limit the profile of the converter and the leakage phenomenon. A planar transformer fit for the inductor-less full-bridge converter is designed and analyzed in 3D FEA software. An N-port transformer model is proposed to implement the inductance matrix into the leakage inductance matrix for circuit analysis. Based on this N-port model several measurements to extract the parameters in this model are proposed, where only the impedance analyzer is needed. Finally, the effects of trace layout and encapsulation on breakdown voltage in PCB are summarized from experimental results.<br>Master of Science

The advent and proliferation of planar technologies for power converters are driven in part by the overall trends in analog and digital electronics. These trends coupled with the demands for increasingly higher power quality and tighter regulations raise various design challenges. Because inductors and transformers constitute a rather large part of the overall converter volume, size and performance improvement of these structures can subsequently enhance the capability of power converters to meet these application-driven demands. Increasing the switching frequency has been the traditional approach in reducing converter size and improving performance. However, the increase in switching frequency leads to increased power loss density in windings and core, with subsequent increase in device temperature, parasitics and electromagnetic radiation. An accurate set of reduced-order modeling methodologies is presented in this work in order to predict the high-frequency behavior of inductors and transformers. Analytical frequency-dependent expressions to predict losses in planar, foil windings and cores are given. The losses in the core and windings raise the temperature of the structure. In order to ensure temperature limitation of the structure is not exceeded, 1-D thermal modeling is undertaken. Based on the losses and temperature limitation, a methodology to optimize performance of magnetics is outlined. Both numerical and analytical means are employed in the extraction of transformer parasitics and cross-coupling. The results are compared against experimental measurements and are found to be in good accord. A simple near-field electromagnetic shield design is presented in order to mitigate the amount of radiation. Due to inadequacy of existing winding technology in forming suitable planar windings for PCB application, an alternate winding scheme is proposed which relies on depositing windings directly onto the core.<br>Master of Science

The following work deals with a design of switched mode power supply. In this essay, there is detailed description of non-isolated and isolated topologies of SMPS, used in industry. Next, there are calculations for design and analysis which are needed for space design. There will also be selected devices, which could be used in final device. Based on experience and ECSS requirements, there will be chosen parameters of SMPS, which could be then used as a module for future space design. Chosen topology of SMPS will be created as engineering model assembled with commercial components. One part of this work is dedicated to design and realization of planar transformer and coupled inductor.

Tato disertační práce se věnuje studiu částečných výbojů (PD) způsobených poklesem spolehlivosti a životnosti elektronických zařízení a systémů. Diagnostika PD je dnes známá metoda pro vysoké napětí u vysoko-výkonných zařízení. V případě elektronických zařízení PD testování není ale běžně používáná metoda, přestože je zde také potenciál pro vysoké elektrické zatížení vzhledem k velmi krátké vzdálenosti. Tato práce je zaměřena na vyšetřování PD činnosti u elektronických zařízení. Bylo navrženo a provedeno pracoviště pro diagnostiku PD v elektronických zařízeních. Pracovní frekvence se pohybuje od několika stovek Hz až 100 kHz. Maximální amplituda PD testovaného napětí je vyšší než 10 kV. Navzdory jednoduché konstrukci toto zařízení přináší vysokou spolehlivost měření. Více než 300 PD testů bylo provedeno na různých elektronických zařízeních a elektronických součástí,např. na planárních transformátorech a elektronických komponentách používaných při vysoko-napěťových měničích

Cette thèse porte sur l'intégration du con-vertisseur DC-DC entre les batteries haute et basse tension (400V / 14V), avec un chargeur embarqué monophasé présent dans l'architecture du véhicule électrique. Dans cette intégration, les deux convertis-seurs sont bidirectionnels et l’isolation galvanique est nécessaire entre les trois sources d'énergie. Dans une première partie de cette étude, nous sommes focali-sés sur le développement d’un convertisseur DC-DC à trois ponts.Le convertisseur DC-DC proposé est un convertisseur bidirectionnel alimenté en courant à résonance pa-rallèle permettant de réaliser des commutations à zéro de tension sur toute la plage de puissance. Grace à la « recopie de tension », le dimensionne-ment du transformateur permet la réalisation d’unestructure beaucoup plus compacte par rapport à d’autres convertisseurs à résonance. Dans la deu-xième partie de ce travail, les caractéristiques du convertisseur sont étudiées afin d’optimiser la stra-tégie de commande et de fonctionnement. Le dé-veloppement d’un transformateur planar est réalisé en respectant les normes pour les véhicules élec-triques et pour minimiser les inductances de fuite. L’étude de la répartition de courant dans les couches connectées en parallèle est faite de façon à éviter la présence de points chauds en haute fré-quence. Le prototype et les résultats finaux sont présentés pour valider le convertisseur à 3 ponts. Après avoir analysé les résultats, quelques proposi-tions sont faites pour améliorer les résultats dans les futurs travaux<br>This dissertation focuses on the integration of two power electronic converters present in the electric vehicle (EV) architecture – the DC-DC con-verter interfacing the high and low voltage batteries (400V/14V) and the onboard charger (OBC). A three-port current-fed parallel resonant topology with zero voltage switching capability is developed. The con-verter allows bidirectional power flow between the three energy sources with high efficiency in both conversion modes, DC-DC and OBC while ensuring galvanic isolation.A compact three-winding planar transformer is de-signed based on EV industry requirements, empha-sizing the minimization of leakage inductances. In this design, the unequal currentsharing phenomenon between parallel-connected layers is addressed to ensure a homogeneous cur-rent distribution and eliminate the risks of thermal hotspots formation.A 7kW experimental prototype has been con-structed and tested, validating the analysis and op-eration of the proposed topology. Some sugges-tions and propositions are provided for future work aiming at efficiency improvement of the converter

Avec un encombrement minimal et rendement de 99% les transformateurs planars haute fréquence sont des solutions technologiques importantes pour les systèmes de conversion et de conditionnement de l'énergie électrique en électronique de puissance. L'objectif de l'étude consiste à rechercher un modèle du composant permettant à la fois de simuler son comportement dans un circuit d'électronique de puissance et d'optimiser ses performances lors de sa conception. Les modèles proposés prennent en compte les propriétés physiques et géométriques du composant. Les validations sont basées sur des confrontations avec les mesures. Une autre motivation forte de ce travail est que les modélisations numériques doivent prendre en compte simultanément les effets des courants induits et les capacités parasites, ce qui conduit, en haute fréquence, à des besoins prohibitifs en termes de capacité mémoire ou de temps de calcul. En se limitant aux transformateurs planar. La modélisation (dite LEEC) présentée ici s'appuie sur une discrétisation à échelle intermédiaire : spire par spire, c'est-à-dire couche par couche. Elle assemble deux approches analytiques déjà introduites par l'équipe : la première traite les aspects électrocinétiques (incluant les courants induits) et magnétiques et l'autre les aspects électrostatiques. Les circuits à constantes localisées basés sur la méthode LEEC montrent un très bon accord avec toutes les mesures jusqu'à 40 MHz. Des outils numériques sont aussi développés pour faciliter l'obtention de ces différents circuits en partant : soit de la description du composant, soit de mesures d'impédances. Pour compléter, la représentation des capacités d'un transformateur quelconque, développée en plusieurs étapes par l'équipe, est résumée et des précautions expérimentales originales appliquées à l'impédancemétrie sont exposées dans le détail. D'autres travaux visant à élargir le champ d'application de la méthode LEEC sont également présentés.

The recent application of semiconductor materials, such as GaN, to power electronics has led to the development of a new generation of devices, which promise lower losses, higher operating frequencies and reductions in equipment size. The aim of this research is to study the capabilities of emerging GaN power devices, to understand their advantages, drawbacks, the challenges of their implementation and their potential impact on the performance of power converters. The thesis starts by presenting the development of a simple model for the switching transients of a GaN cascode device under inductive load conditions. The model enables accurate predictions to be made of the switching losses and provides an understanding of the switching process and associated energy flows within the device. The model predictions are validated through experimental measurements. The model reveals the suitability of the cascode device to soft-switching converter topologies. Two GaN cascode transistors are characterised through experimental measurement of their switching parameters (switching speed and switching loss). The study confirms the limited effect of the driver voltage and gate resistance on the turn-off switching process of a cascode device. The performance of the GaN cascode devices is compared against state-of-the-art super junction Si transistors. The results confirm the feasibility of applying the GaN cascode devices in half and full-bridge circuits. Finally, GaN cascode transistors are used to implement a 270V - 28V, 1.5kW, 1 MHz phase-shifted full-bridge isolated converter demonstrating the use of the devices in soft-switching converters. Compared with a 100 kHz silicon counterpart, the magnetic component weight is reduced by 69% whilst achieving a similar efficiency of 91%.

Dans l’aéronautique et plus précisément dans les avions tout électrique, l’objectif visé est de réduire les masses et volumes des composants. Pour cela, les actionneurs électriques remplacent progressivement les actionneurs hydrauliques et mécaniques. Ces actionneurs électriques ont besoin d’être commandés ; le projet THOR (projet européen dans lequel s’inscrit cette thèse) vise entre autres à développer un étage de commande permettant de piloter des interrupteurs de puissance. Les interrupteurs étant situés à proximité directe de l’étage driver et les tensions de sorties pouvant atteindre 3 kV, une isolation galvanique est obligatoire. Anciennement, les optocoupleurs étaient utilisés pour assurer l’isolation galvanique dans les étages de commande. Cependant, afin de pouvoir utiliser ces composants dans un environnement thermique contraignant et assurer une meilleure intégration, les opto-coupleurs ne sont plus adaptés et sont remplacés par des transformateurs. Dans ce contexte, s’inscrivent les travaux de cette thèse où l’objectif principal est de développer, réaliser et caractériser des transformateurs planaires intégrables répondant au cahier des charges THOR. Dans un premier temps, un état de l’art sur les différentes technologies de fabrication de transformateurs planaires est établi avant de choisir la technologie et les matériaux utilisés dans ces composants. Dans un deuxième temps, on s’intéresse au choix et au dimensionnement du transformateur. Deux structures répondant au cahier des charges THOR ont été retenues et dimensionnées à l’aide d’un logiciel de simulation (HFSS) : une structure entrelacée et une structure ‘face to face’. Ces deux structures ont été réalisées et caractérisées à l’aide d’un LCRmètre en basse fréquence et d’un Analyseur Vectoriel de Réseaux (VNA) en haute fréquence. Pour les deux structures, la caractérisation a permis de vérifier les valeurs des inductances magnétisantes supérieures à 1 μH souhaitées par le projet THOR et des facteurs de couplages supérieurs à 0,9 déterminées par simulation. D’autres paramètres importants du cahier des charges ont été également extraits à savoir la capacité interbobinage où des capacités inférieures à quelques pF ont été obtenues et des résistances d’enroulement inférieures à 10 Ω ont été relevées<br>In aeronautics and more specifically in an all-electric aircraft, the main objective is to reduce the mass and volume of the components. For this, the electric actuators gradually replace hydraulic and mechanical actuators. These electric actuators need to be commanded; THOR project (European project supporting this thesis) aims to develop a control stage to command the power switches. The switches are located in the direct vicinity of the driver stage with an output voltage that can reach up to 3 kV hence the need for a galvanic isolation. Formerly, the opto-couplers were used to provide galvanic isolation in the control stages. However, in order to use these components in thermal constraining environment and ensure better integration, opto-couplers are no longer appropriate and are replaced by transformers. In this context, the main objective of this thesis is to develop, realize and characterize integrated planar transformers that meet the THOR specifications. At first a state of art on the different manufacturing technologies of planar transformers is established before choosing the technology and the materials used in the fabrication of our planar transformers. In a second step, we are interested in the choice and size of the transformer structure. Two structures that met the THOR specifications were selected and resized using a simulation software (HFSS). Finally, these two structures were realized and characterized using an RLC-meter at low frequency and a Vector Network Analyzer (VNA) at high frequency. For both structures, the characterization allowed to verified the magnetizing inductance greater than 1 μH desired by the THOR project and a coupling factor greater than 0,9 obtained par simulations. Other important parameters were also extracted namely the inter-winding capacity where less than few pF wasobtained and the windings resistance has been identified less than 10 Ω

Submitted by Cristhiane Guerra (cristhiane.guerra@gmail.com) on 2017-01-26T13:30:08Z No. of bitstreams: 1 arquivototal.pdf: 7840328 bytes, checksum: 74229a382309ea0fcf42de5818cc899a (MD5)<br>Made available in DSpace on 2017-01-26T13:30:08Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 7840328 bytes, checksum: 74229a382309ea0fcf42de5818cc899a (MD5) Previous issue date: 2016-08-25<br>The aim of this work deals with the analysis of the mutual interaction between flow and magnetic fields that develops in a parallel-plate channel as soon as an external magnetic field is applied transversely to the plates. The fluid, electrically conductive, enters the channel under any velocity profile and will have its natural development within the channel changed by the applied magnetic field. With a coupled two-way interaction, the field will also be affected by the flow. The study of these interactions will be made from the two-dimensional version of the steady-state Navier-Stokes equations in the stream function formulation, coupled with the transport equation of the magnetic field. The solution of the governing equations will be obtained by the Generalized Integral Transform Technique (GITT). The results obtained for the velocity field, magnetic field and temperature field, as well as the associated scalar functions, are produced and compared with the literature on the basis of the main parameters of government: Reynolds number (Re), magnetic Reynolds number (Rem) and Hartmann number (Ha). In order to illustrate the consistency of the generalized integral transform technique, convergence analysis, are also performed and presented.<br>O objetivo do presente trabalho trata da análise da interação mútua escoamento/campo magnético que se desenvolve no interior de um canal de placas planas e paralelas ao se aplicar um campo magnético externo transversal. O fluido, eletricamente condutor, entra no canal sob um perfil qualquer de velocidade, e terá seu desenvolvimento natural afetado pelo campo magnético aplicado. Com uma interação acoplada de duas vias, o campo também será afetado pelo escoamento. O estudo dessas interações será efetuado a partir de uma formulação bidimensional das equações de Navier-Stokes, na formulação em função corrente, para escoamento em regime permanente, acoplada à equação de transporte do campo magnético. A solução das equações governantes será obtida através da Técnica da Transformada Integral Generalizada (GITT). Os resultados obtidos para o campo de velocidade e campo magnético, bem como suas funções escalares associadas, são produzidos e comparados aos da literatura em função dos principais parâmetros de governo: número de Reynolds (Re), número de Reynolds magnético (Rem) e número de Hartmann (Ha). Com o objetivo de ilustrar a consistência da técnica da transformada integral generalizada, análises de convergência são também efetuadas e apresentadas.

Made available in DSpace on 2014-12-17T14:58:04Z (GMT). No. of bitstreams: 1 MariaGOR_DISSERT.pdf: 1839301 bytes, checksum: 7f08c7ee57fc0bc1f8282eb165223c37 (MD5) Previous issue date: 2010-11-12<br>Universidade Federal do Rio Grande do Norte<br>The main goal of the present work is related to the dynamics of the steady state, incompressible, laminar flow with heat transfer, of an electrically conducting and Newtonian fluid inside a flat parallel-plate channel under the action of an external and uniform magnetic field. For solution of the governing equations, written in the parabolic boundary layer and stream-function formulation, it was employed the hybrid, numericalanalytical, approach known as Generalized Integral Transform Technique (GITT). The flow is sustained by a pressure gradient and the magnetic field is applied in the direction normal to the flow and is assumed that normal magnetic field is kept uniform, remaining larger than any other fields generated in other directions. In order to evaluate the influence of the applied magnetic field on both entrance regions, thermal and hydrodynamic, for this forced convection problem, as well as for validating purposes of the adopted solution methodology, two kinds of channel entry conditions for the velocity field were used: an uniform and an non-MHD parabolic profile. On the other hand, for the thermal problem only an uniform temperature profile at the channel inlet was employed as boundary condition. Along the channel wall, plates are maintained at constant temperature, either equal to or different from each other. Results for the velocity and temperature fields as well as for the main related potentials are produced and compared, for validation purposes, to results reported on literature as function of the main dimensionless governing parameters as Reynolds and Hartman numbers, for typical situations. Finally, in order to illustrate the consistency of the integral transform method, convergence analyses are also effectuated and presented<br>O prop?sito do estudo desenvolvido nesse trabalho est? relacionado com a din?mica do escoamento incompress?vel, laminar, em regime permanente, com transfer?ncia de calor, de um fluido newtoniano condutor el?trico, no interior de um canal de placas planas paralelas, submetido a um campo magn?tico externo uniforme. Para a solu??o das equa??es de governo, modeladas atrav?s da formula??o parab?lica de camada limite em fun??o corrente, foi empregado o m?todo h?brido, num?rico-anal?tico, conhecido como T?cnica da Transformada Integral Generalizada (GITT). O escoamento analisado ? sustentando por um gradiente de press?o e assume-se que o campo magn?tico externo, aplicado na dire??o normal ao escoamento, permanece uniforme, muito maior do que quaisquer outros campos gerados em outras dire??es, n?o sendo, dessa forma, influenciado por nenhum efeito magn?tico interno. Para avaliar a influ?ncia do campo magn?tico sobre o desenvolvimento t?rmico e hidrodin?mico desse problema de convec??o for?ada, e tamb?m para fins de valida??o da metodologia de solu??o adotada, foram empregados dois tipos de condi??es de contorno para o campo de velocidade na entrada no canal: perfil uniforme e perfil parab?lico do escoamento sem campo magn?tico completamente desenvolvido. Para o problema t?rmico, por outro lado, empregou-se apenas o perfil uniforme de temperatura na entrada do canal e considerou-se que as placas se mant?m ? temperatura constante, iguais ou diferentes uma da outra. Resultados para os campos de velocidade, temperatura e potenciais correlatos s?o produzidos e comparados aos da literatura em fun??o dos principais par?metros de governo, a saber, n?mero de Reynolds, n?mero de Hartmann e par?metro el?trico, para algumas situa??es t?picas. Com o objetivo de ilustrar a consist?ncia da t?cnica da transformada integral generalizada, an?lises de converg?ncia s?o tamb?m efetuadas e apresentadas

The presented thesis is focused on knowledge extension in the area of partial discharge measurements and evaluation at frequencies higher than 1 kHz. The thesis includes the design and set up of the measuring workplace equipped for measuring partial discharges, including the methodology of the measuring and calibration procedures necessary for the achievement of reproducible results. Another part of the thesis deals with the technology of acoustical and electromagnetic sensors convenient for the diagnostics and localization of partial discharges in devices, that work at voltages above 500 V. Electrical circuits that enable data evaluation by using the signal from a sensor working on amplitude analysis principle were developed. For PD detection a PC controlled measuring device working on amplitude analysis principle had to be designed and realized. The possibilities of the workplace have been demonstrated in the process of development of the insulating systems for pulse transformers. Thesis results can significantly contribute to a higher quality of newly designed electronic devices and systems working at voltages above 500 V.

Made available in DSpace on 2014-12-17T14:55:34Z (GMT). No. of bitstreams: 1 GeorgeDFA_Capa_ate_pag15.pdf: 8968407 bytes, checksum: 05f7b40d8df8312cf173aaad3ec43f83 (MD5) Previous issue date: 2006-08-04<br>Recently, planar antennas have been studied due to their characteristics as well as the advantages that they offers when compared with another types of antennas. In the mobile communications area, the need for this kind of antennas have became each time bigger due to the intense increase of the mobile communications this sector. That needs of antennas which operate in multifrequency and wide bandwidth. The microstrip antennas presents narrow bandwidth due the loss in the dielectric generated by radiation. Another limitation is the radiation pattern degradation due the generation of surface waves in the substrate. In this work some used techniques to minimize the disadvantages (previously mentioned) of the use of microstrip antennas are presented, those are: substrates with PBG material - Photonic Bandgap, multilayer antennas and with stacked patches. The developed analysis in this work used the TTL - Transverse Transmission Line method in the domain of Fourier transform, that uses a component of propagation in the y direction (transverse to the direction real of propagation z), treating the general equations of electric and magnetic field as functions of Ey and Hy. One of the advantages of this method is the simplification of the field equations. therefore the amount of equations lesser must the fields in directions x and z be in function of components Ey and Hy. It will be presented an brief study of the main theories that explain the superconductivity phenomenon. The BCS theory. London Equations and Two Fluids model will be the theories that will give support the application of the superconductors in the microfita antennas. The inclusion of the superconductor patch is made using the resistive complex contour condition. This work has as objective the application of the TTL method to microstrip structures with single and multilayers of rectangular patches, to obtaining the resonance frequency and radiation pattern of each structure<br>Recentemente as antenas planares t?m despertado interesses devido ?s suas caracter?sticas, assim como pelas vantagens que oferecem quando comparadas com os demais tipos de antenas. Na ?rea de comunica??es m?veis a necessidade de antenas desse tipo tem-se tornado cada vez maior devido ao intenso crescimento desse setor, necessitando de antenas que operem em multifreq??ncia e em banda larga. As antenas de microfita apresentam largura de banda estreita devido ?s perdas no diel?trico geradas pela irradia??o. Outra limita??o ? a degrada??o do diagrama de irradia??o devido ? gera??o de ondas de superf?cie no substrato. Neste trabalho s?o apresentadas algumas t?cnicas usadas para tentar minimizar as desvantagens (citadas acima) do uso de antenas de microfita, sendo elas: substratos com material PBG - Photonic Bandgap, antenas em multicamadas e a utiliza??o de patches fabricados de materiais supercondutores. As an?lises desenvolvidas neste trabalho foram realizadas com a utiliza??o do m?todo LTT - Linha de Transmiss?o Transversa no dom?nio da transformada de Fourier, que utiliza uma componente de propaga??o na dire??o y (transversa ? dire??o real de propaga??o z), tratando assim as equa??es gerais dos campos el?tricos e magn?ticos em fun??es de Ey e Hy. Uma das vantagens desse m?todo ? a simplifica??o das equa??es de campo, pois a quantidade de equa??es ? menor devido os campos nas dire??es x e z ficarem em fun??o das componentes Ey e Hy. Ser? apresentado um breve estudo das principais teorias que explicam o fen?meno da supercondutividade. As teorias BCS, Equa??es de London e modelo dos Dois Fluidos ser?o as teorias que dar?o suporte a aplica??o dos supercondutores nas antenas microfita. A inclus?o do patch supercondutor ? feita utilizando-se a condi??o de contorno complexa resistiva. Este trabalho tem como objetivo a aplica??o do m?todo LTT ?s estruturas de microfita

Cette thèse a pour objectif de reproduire au mieux un champ sonore enregistré par une antenne de microphones au moyen d'un réseau de sources secondaires. Pour y parvenir, nous avons dans un premier temps réalisé une étude approfondie des représentations harmoniques et intégrales des champs sonores. Dans un deuxième temps, nous avons mis au point des algorithmes qui utilisent la représentation du champ sonore en ondes planes pour effectuer l'analyse et la synthèse.L'algorithme d'analyse proposé est un algorithme de formation de voies donnant une solution analytique au problème de la minimisation du repliement. Le problème de l'optimisation de la géométrie de l'antenne est aussi abordé. L'algorithme utilisé pour la synthèse est un algorithme flexible pour l'égalisation dans un contexte multicanal, qui permet de réduire les artefacts des méthodes traditionnelles, tels que le pré-écho et le post-écho. Finalement, l'efficacité de ces algorithmes d'analyse et de synthèse est démontrée par des simulations et validée par des manipulations.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2017<br>This research has considered an idealistic non-interleaved planar transformer wherein only the electromagnetic parasitic capacitive and inductive elements arising out of the transformer geometry are taken into account, without considering material limitations. A suitable model for the planar transformer is used to analyse its frequency and power transfer characteristics; this model was validated by three dimensional electromagnetic simulations of various planar transformer structures in FEKO simulation software. The capacitive and inductive parasitics in this model have been found to be functions of the dielectric thickness. The theoretical bandwidth for the planar transformer is defined in this research as a function of dielectric thickness. The effect of dielectric thickness of the transformer windings on the bandwidth of the transformer is analysed, based on the premise that the inherent parasitic capacitive and inductive elements would affect the transfer characteristics of the transformer. Upon conclusion of this analysis, it is found that the dielectric thickness of a planar transformer can be optimised such as to present an optimised bandwidth. A closed form analytic expression for the optimum dielectric thickness value is derived and presented in this research. In a design example of a 4:1 50W transformer presented in this research, it has been shown that the bandwidth can be improved by 384%, along with a power density improvement of 45%, upon choosing of an optimum dielectric thickness of 0.156mm to replace a standard 0.4mm thick dielectric. It should be noted that the results derived in this research are purely theoretical, justified by many idealisations and assumptions that are argued throughout the research. It is thus expected that practical results should at best approach the theoretical results, due to the known non-ideal nature of reality.<br>CK2018

碩士<br>國立臺灣大學<br>應用力學研究所<br>91<br>In this thesis, the micro-inductors and micro-transformers with arrayed magnetic cores were devised and fabricated in two ways. First, 0.35μm 1P4M (single poly quadri-metal, SPQM) standard CMOS was used to design and fabricate micro-inductors and micro-transformers. Then, MEMS post-process was performed in order to enhance component performance. Through combination of CMOS and MEMS technology, the ultimate aim was the integration of traditional off-chip passive components and micro electronic circuits to achieve the concept of system on a chip (soc). Second, the masks were designed, and the fabrication process can be compatible with standard CMOS process. The spiral micro-inductors include 1.5, .2.5, 3.5, 5.5 turns with varying width. Finally, the thick copper metal was electroplated to reduce the resistance. In this research, highly permeability material (Ni-20% and Fe-80%) has been successfully evaporated onto the inductors. Micro-inductors and micro-transformers with arrayed magnetic cores have better inductance and quality factor than those with air core. Then the arrayed magnetic cores will enhanced the performance of micro-inductors and micro-transformers.

碩士<br>國立臺北科技大學<br>電機工程系電力電子產業碩士專班<br>107<br>The purpose of this thesis is to investigate the loss of the planar transformer which is used for phase-shifted full-bridge converter. Using ANSYS Maxwell simulation software, the leakage inductance, winding loss and core loss of the transformer with six different types are analyzed. The simulation results show that the total loss of the planar transformer with a turn ratio of 2：2 is 3.33 W, and the total loss of the interleaved winding of 3：3 is 11.38 W. The experimental results show that the phase-shifted full-bridge converter using sandwich 2：2 is 83.47 % at 60% load and the highest efficiency is 85.50 % at full load.

M.Ing.<br>Low profile power electronics components are currently in great demand. The rapid advances in semiconductor and micro-electronics technology during the last ten years have played a major role in the creation of this demand. These advances are in turn driven by the need for compact design in computing, communication, consumer electronic goods and control systems with direct consequences in power supply design and manufacture. The study covered by this thesis involves the design, manufacture and thermal analysis of a planar inductor, which is a typical planar power electronics component. First, a throughout literature survey of planar magnetics revealed that satisfactory experimental procedures for the thermal analysis of passive power electronic components under operating conditions representative of modern applications are seldomly applied. Secondly, a computer based field-solver program and analytical methods are used to design and analyse a planar inductor. The applicability of different methods for determination of low power loss in passive components is discussed next. Finally, an experimental method suitable for low power loss determination is proposed and investigated. This method can be used in the analysis of inductors or capacitors of different sizes. It has a wide spectrum of application due to the advantages of frequency independence and different possible power levels.

碩士<br>中華大學<br>電機工程學系(所)<br>97<br>In this report, a RJ-45 filter’s design and simulate is presented, how to minimize the thickness and areas of filter bank is the crucial issue of the future high speed Ethernet devices and equipments. We will study the planar integrated transformer technology for RJ-45 filter bank of RJ-45 network product.

碩士<br>國立中山大學<br>電機工程學系研究所<br>96<br>This thesis is mainly composed of two parts. The first part is to introduce the planar transformer-based circuits and their applications. The mixed-mode S parameters and the grounding effects for planar transformers are discussed. A physical model has been developed for modeling the planar transformers. In the second part, a new coil winding technique for planar transformers has been presented to realize a high-efficiency planar transformer with arbitrary turn ratio for power-split/combine and phase-shift applications. Especially, the power-split/combine architecture based on a planar transformer of cellular shape is first presented in this thesis, enabling various kinds of passive components to be widely realized using the integrated passive device processes. As an example, this thesis proposes a design procedure for high-efficiency balun component. Firstly, design a high Q transformer that considers the load impedance effects. Secondly, design the ground reference for un-balanced signal on the virtual ground symmetry axis for balanced signals. Thirdly, design impedance matching networks for minimizing un-balanced and balanced port return losses. Then, a high performance planar transformer-based balun design can be done.

碩士<br>國立彰化師範大學<br>電機工程學系<br>101<br>Abstract For the sake of convenience and use of electricity and other security purposes, contactless energy transfer system has been used in a lot of various load, such as cell phone chargers. Because of cell-phone unmistakable wave of prosperity, therefore, this paper is to design contactless distribution of the transformer as the main objective of uniform magnetic field. Coil type is the common linear and helical bundles of two, and its magnetic field distribution were concave and convex distribution, respectively. As a result, it will cause non-uniform distribution of magnetic field. Therefore, in this thesis, linear and helical bundles are combined as hybrid coil, in order to perform a flatter distribution of the magnetic field. There are two charging platform is designed, some characteristic are measured, the magnetic field, mutual inductance quantity and power measurement. NoiseKen EPS-3000 is used to analysis and measured the hybrid coil field distribution, respectively. A Pick-up coil is designed to measuring power output, which the maximum output power is up to 1.2 W. The experimental results show the uniform magnetic field distribution is achieved. The prototype circuit could be used a reference guide. Keywords: Contactless Power Transfer, Hybrid Coil Design, Vertical Magnetic Field Uniform Distribution

碩士<br>元智大學<br>電機工程學系<br>99<br>The study in this thesis is related to a wireless charger system based on planar PCB windings. This wireless charger system consists of energy supply module, energy receiver and charge circuit. The planar PCB windings are used as transformers for energy transfer from the supply module to the receiver; in particular, the multilayer hexagonal PCB windings are employed to generate uniform magnetic flux over the surface of the planar PCB windings to enhance the energy transfer efficiency. The kernel technique includes the connection and arrangement of the PCB windings. In this study, the major innovative concept is to make wireless charger module scalable regardless of the load size, positions and orientation. Also provided are the equivalent circuit and model for optimal power delivery. The system is implemented and measured with DC 12V supply voltage, 100 KHz operating frequency and charging power 1.15W with delivery efficiency 8%. A test of the system is performed on a mobile phone.

碩士<br>國立臺灣科技大學<br>電子工程系<br>106<br>Magnetic components are the main source of power losses in high step-down LLC resonant converters. Therefore, to achieve high efficiency and high power density, improving the magnetic element is an important issue. Ferrite cores with high permeability and low core loss are widely used in high-frequency switching power supplies. The core loss mainly results from hysteresis loss and eddy current loss. Therefore, this thesis aims to analyze and optimize the structure of ferrite cores using Maxwell software to implement the Finite Element Method (FEM). Changing the distribution of magnetic flux density to reduce core loss results in a tradeoff design between the volume and loss of magnetic core. Then, the transformer can be optimized to achieve high circuit efficiency. Finally, a 750-W LLC resonant converter prototype with specifications of 380-V input voltage, 12-V output voltage, and 500-kHz switching frequency is implemented and tested to verify the feasibility of different architectures on transformer cores.

碩士<br>國立彰化師範大學<br>電機工程學系<br>107<br>In this study, a contactless power transmission system based on a coreless PCB transformer is developed for the application of the electric scooter’s battery charging. The overall system is mainly divided into two parts: a charging end module and a battery end module. The two windings of the PCB transformer are integrated into the charging and battery modules respectively. The overall size of the modules and the core power losses can be reduced by using the coreless PCB transformer. The LCL resonance compensation topology for the coreless PCB transformer is adopted for the future development of bidirectional power conversion. On the secondary side, the full-bridge diode rectifier is used to convert the high-frequency AC power into a DC power source. After analyzing and simulating the characteristics of the LCL resonance compensation topology, it can be found that the secondary side output current is also almost constant when the primary side voltage is fixed. As a result, a DC converter is integrated into the secondary side to control the battery charging power. In the proposed control strategy, the control signal transmission between the primary and secondary sides is not required, which can reduce the system cost and the controller complexity. A prototype with 100W rated power of the proposed contactless power transmission system is implemented. The input 48V DC power is converted into 12V power for charging the battery. The constant-current/constant-voltage charging method with 14.4V/6.9A is adopted. The efficiency of the developed system is about 71% for the battery charging. From the experimental results, the validity and performance of the proposed system are both verified.

碩士<br>國立中央大學<br>電機工程學系在職專班<br>101<br>With the requirement of Power Factor (PF) are being set to standards, commercial electrical products must pass globally recognized standards such as the European EN61000-3-2 and the Energy Star Program Requirements to be sold around the globe. Under the consideration for minimum Total Harmonic Distortion (THD) and maximum PF, the Boost Power Factor Correction (PFC) topology is used to meet the demands for applications with a 400 V high voltage output. To take advantage in the recent advance in planar passive components, a planar ferrite core transformer is used with the proposed Boost PFC circuit, which allows high power density and decreases the overall volume of the system. This thesis begins with the discussion regarding the relationship and physical significance between THD and PF. Comparisons between passive and active PFC circuits, Buck PFC circuits and Boost PFC circuits, single stage PFC circuits and multi stage PFC circuits, are given respectively. This thesis also compares the differences in circuit operation regarding the continuity of transformer current. The operations of each circuit blocks are given in detail, and a small-signal model is derived for analysis. The metal core planar transformer technology is also introduced. Finally, in order to verify the design proposed in this thesis, circuit simulation and actual measurement are conducted. Simulation results suggest that the proposed PFC circuit provides sufficient PF and THD ratings for many major international standards under various input voltage and output loading conditions. Its high power conversion efficiency also satisfies the need for commercial electrical products requiring high input voltage and demands high power consumption.

碩士<br>國立臺北科技大學<br>電機工程系電力電子產業碩士專班<br>106<br>The purpose of this thesis is to investigate the parasitic capacitance and stray inductance of planar transformer which is used for GaN-based high frequency half bridge converter. The parasitic capacitance and stray inductance will result in more relevant loss and high spike under high switching frequency operation. To solve these issues, planar transformer is designed and its parasitic capacitance and stray inductance are analyzed using finite element tools.The designed and analyzed results are confirmed by measured results. A half-bridge resonant converter using GaN devices and the designed planar transformer is implemented and controlled by digital controller. The design specifications of half bridge resonant converter include: input DC voltage of 400V, output voltage of 12V, total power rating of 600W, switching frequency of 480 kHz ~ 620 kHz. Simulation and experimental results show that the maximum efficiency is up to 95.79%. These results confirm the design and implementation.

碩士<br>國立臺灣科技大學<br>電子工程系<br>107<br>This paper proposes an isolated DC-DC converter for cloud servers. With a switching frequency in the range of MHz, an LLC resonant converter is selected that can achieve zero voltage switching over the full load range. It replaces the traditional switch components with wide bandgap devices, like GaN, to reduce the turn-off loss of the power components. This paper proposes a new half-turn transformer structure, which uses magnetic flux cancellation to reduce the core loss. The secondary winding is a half-turn to achieve a fractional winding that maintains a winding ratio of 16:1. Solving the problem of increasing the volume of the fractional-circle transformer in previous research, the new half-turn transformer can simultaneously achieve the goal of reducing core loss and volume while increasing power density. Parametric form is used to calculate the core loss and copper loss to achieve an optimized design in the limited circuit layout area. The magnetic simulation software Maxwell of ANSYS is used to verify the circuit behavior with a planner transformer, which conforms to the previous design theory. Finally, the implemented 800-W LLC resonant converter with the proposed design switches at 1 MHz, has an input voltage of 380 V and an output voltage of 12 V, achieves a maximum efficiency of 95.21%, and has a power density of 55 W/cm3.

碩士<br>國立中山大學<br>通訊工程研究所<br>97<br>This thesis at first introduces planar transformers and their applications to RF circuits. A method is given to validate the impedance transformation and calculate the insertion loss for a transformer with unequal turn windings. A physical lumped-element model has been established for a planar transformer-based balun implemented using integrated passive device technology. This thesis next presents CMOS power combiner designs with two differential ports and one single-ended port. Such designs equivalently integrate two baluns and one single-ended power combiner into a single circuit and therefore have the advantages of saving chip area and reducing insertion loss. In addition, the designs consider an annular ground structure to achieve lower insertion loss or better balance property. Finally, this thesis presents a balun using a stacked coil transformer in an organic build-up substrate. For this purpose, a complete design flow and an impedance matching technique have been given.

L'athérosclérose est une maladie vasculaire complexe qui affecte la paroi des artères (par l'épaississement) et les lumières (par la formation de plaques). La rupture d'une plaque de l'artère carotide peut également provoquer un accident vasculaire cérébral ischémique et des complications. Bien que plusieurs modalités d'imagerie médicale soient actuellement utilisées pour évaluer la stabilité d'une plaque, elles présentent des limitations telles que l'irradiation, les propriétés invasives, une faible disponibilité clinique et un coût élevé. L'échographie est une méthode d'imagerie sûre qui permet une analyse en temps réel pour l'évaluation des tissus biologiques. Il est intéressant et prometteur d’appliquer une échographie vasculaire pour le dépistage et le diagnostic précoces des plaques d’artère carotide. Cependant, les ultrasons vasculaires actuels identifient uniquement la morphologie d'une plaque en termes de luminosité d'écho ou l’impact de cette plaque sur les caractéristiques de l’écoulement sanguin, ce qui peut ne pas être suffisant pour diagnostiquer l’importance de la plaque. La technique d’élastographie vasculaire non-intrusive (« noninvasive vascular elastography (NIVE) ») a montré le potentiel de détermination de la stabilité d'une plaque. NIVE peut déterminer le champ de déformation de la paroi vasculaire en mouvement d’une artère carotide provoqué par la pulsation cardiaque naturelle. En raison des différences de module de Young entre les différents tissus des vaisseaux, différents composants d’une plaque devraient présenter différentes déformations, caractérisant ainsi la stabilité de la plaque. Actuellement, les performances et l’efficacité numérique sous-optimales limitent l’acceptation clinique de NIVE en tant que méthode rapide et efficace pour le diagnostic précoce des plaques vulnérables. Par conséquent, il est nécessaire de développer NIVE en tant qu’outil d’imagerie non invasif, rapide et économique afin de mieux caractériser la vulnérabilité liée à la plaque. La procédure à suivre pour effectuer l’analyse NIVE consiste en des étapes de formation et de post-traitement d’images. Cette thèse vise à améliorer systématiquement la précision de ces deux aspects de NIVE afin de faciliter la prédiction de la vulnérabilité de la plaque carotidienne. Le premier effort de cette thèse a été dédié à la formation d'images (Chapitre 5). L'imagerie par oscillations transversales a été introduite dans NIVE. Les performances de l’imagerie par oscillations transversales couplées à deux estimateurs de contrainte fondés sur un modèle de déformation fine, soit l’ « affine phase-based estimator (APBE) » et le « Lagrangian speckle model estimator (LSME) », ont été évaluées. Pour toutes les études de simulation et in vitro de ce travail, le LSME sans imagerie par oscillation transversale a surperformé par rapport à l'APBE avec imagerie par oscillations transversales. Néanmoins, des estimations de contrainte principales comparables ou meilleures pourraient être obtenues avec le LSME en utilisant une imagerie par oscillations transversales dans le cas de structures tissulaires complexes et hétérogènes. Lors de l'acquisition de signaux ultrasonores pour la formation d'images, des mouvements hors du plan perpendiculaire au plan de balayage bidimensionnel (2-D) existent. Le deuxième objectif de cette thèse était d'évaluer l'influence des mouvements hors plan sur les performances du NIVE 2-D (Chapitre 6). À cette fin, nous avons conçu un dispositif expérimental in vitro permettant de simuler des mouvements hors plan de 1 mm, 2 mm et 3 mm. Les résultats in vitro ont montré plus d'artefacts d'estimation de contrainte pour le LSME avec des amplitudes croissantes de mouvements hors du plan principal de l’image. Malgré tout, nous avons néanmoins obtenu des estimations de déformations robustes avec un mouvement hors plan de 2.0 mm (coefficients de corrélation supérieurs à 0.85). Pour un jeu de données cliniques de 18 participants présentant une sténose de l'artère carotide, nous avons proposé d'utiliser deux jeux de données d'analyses sur la même plaque carotidienne, soit des images transversales et longitudinales, afin de déduire les mouvements hors plan (qui se sont avérés de 0.25 mm à 1.04 mm). Les résultats cliniques ont montré que les estimations de déformations restaient reproductibles pour toutes les amplitudes de mouvement, puisque les coefficients de corrélation inter-images étaient supérieurs à 0.70 et que les corrélations croisées normalisées entre les images radiofréquences étaient supérieures à 0.93, ce qui a permis de démontrer une plus grande confiance lors de l'analyse de jeu de données cliniques de plaques carotides à l'aide du LSME. Enfin, en ce qui concerne le post-traitement des images, les algorithmes NIVE doivent estimer les déformations des parois des vaisseaux à partir d’images reconstituées dans le but d’identifier les tissus mous et durs. Ainsi, le dernier objectif de cette thèse était de développer un algorithme d'estimation de contrainte avec une résolution de la taille d’un pixel ainsi qu'une efficacité de calcul élevée pour l'amélioration de la précision de NIVE (Chapitre 7). Nous avons proposé un estimateur de déformation de modèle fragmenté (SMSE) avec lequel le champ de déformation dense est paramétré avec des descriptions de transformées en cosinus discret, générant ainsi des composantes de déformations affines (déformations axiales et latérales et en cisaillement) sans opération mathématique de dérivées. En comparant avec le LSME, le SMSE a réduit les erreurs d'estimation lors des tests de simulations, ainsi que pour les mesures in vitro et in vivo. De plus, la faible mise en oeuvre de la méthode SMSE réduit de 4 à 25 fois le temps de traitement par rapport à la méthode LSME pour les simulations, les études in vitro et in vivo, ce qui pourrait permettre une implémentation possible de NIVE en temps réel.<br>Atherosclerosis is a complex vascular disease that affects artery walls (by thickening) and lumens (by plaque formation). The rupture of a carotid artery plaque may also induce ischemic stroke and complications. Despite the use of several medical imaging modalities to evaluate the stability of a plaque, they present limitations such as irradiation, invasive property, low clinical availability and high cost. Ultrasound is a safe imaging method with a real time capability for assessment of biological tissues. It is clinically used for early screening and diagnosis of carotid artery plaques. However, current vascular ultrasound technologies only identify the morphology of a plaque in terms of echo brightness or the impact of the vessel narrowing on flow properties, which may not be sufficient for optimum diagnosis. Noninvasive vascular elastography (NIVE) has been shown of interest for determining the stability of a plaque. Specifically, NIVE can determine the strain field of the moving vessel wall of a carotid artery caused by the natural cardiac pulsation. Due to Young’s modulus differences among different vessel tissues, different components of a plaque can be detected as they present different strains thereby potentially helping in characterizing the plaque stability. Currently, sub-optimum performance and computational efficiency limit the clinical acceptance of NIVE as a fast and efficient method for the early diagnosis of vulnerable plaques. Therefore, there is a need to further develop NIVE as a non-invasive, fast and low computational cost imaging tool to better characterize the plaque vulnerability. The procedure to perform NIVE analysis consists in image formation and image post-processing steps. This thesis aimed to systematically improve the accuracy of these two aspects of NIVE to facilitate predicting carotid plaque vulnerability. The first effort of this thesis has been targeted on improving the image formation (Chapter 5). Transverse oscillation beamforming was introduced into NIVE. The performance of transverse oscillation imaging coupled with two model-based strain estimators, the affine phase-based estimator (APBE) and the Lagrangian speckle model estimator (LSME), were evaluated. For all simulations and in vitro studies, the LSME without transverse oscillation imaging outperformed the APBE with transverse oscillation imaging. Nonetheless, comparable or better principal strain estimates could be obtained with the LSME using transverse oscillation imaging in the case of complex and heterogeneous tissue structures. During the acquisition of ultrasound signals for image formation, out-of-plane motions which are perpendicular to the two-dimensional (2-D) scan plane are existing. The second objective of this thesis was to evaluate the influence of out-of-plane motions on the performance of 2-D NIVE (Chapter 6). For this purpose, we designed an in vitro experimental setup to simulate out-of-plane motions of 1 mm, 2 mm and 3 mm. The in vitro results showed more strain estimation artifacts for the LSME with increasing magnitudes of out-of-plane motions. Even so, robust strain estimations were nevertheless obtained with 2.0 mm out-of-plane motion (correlation coefficients higher than 0.85). For a clinical dataset of 18 participants with carotid artery stenosis, we proposed to use two datasets of scans on the same carotid plaque, one cross-sectional and the other in a longitudinal view, to deduce the out-of-plane motions (estimated to be ranging from 0.25 mm to 1.04 mm). Clinical results showed that strain estimations remained reproducible for all motion magnitudes since inter-frame correlation coefficients were higher than 0.70, and normalized cross-correlations between radiofrequency images were above 0.93, which indicated that confident motion estimations can be obtained when analyzing clinical dataset of carotid plaques using the LSME. Finally, regarding the image post-processing component of NIVE algorithms to estimate strains of vessel walls from reconstructed images with the objective of identifying soft and hard tissues, we developed a strain estimation method with a pixel-wise resolution as well as a high computation efficiency for improving NIVE (Chapter 7). We proposed a sparse model strain estimator (SMSE) for which the dense strain field is parameterized with Discrete Cosine Transform descriptions, thereby deriving affine strain components (axial and lateral strains and shears) without mathematical derivative operations. Compared with the LSME, the SMSE reduced estimation errors in simulations, in vitro and in vivo tests. Moreover, the sparse implementation of the SMSE reduced the processing time by a factor of 4 to 25 compared with the LSME based on simulations, in vitro and in vivo results, which is suggesting a possible implementation of NIVE in real time.