Le chapitre 1 introduit le sujet et son contexte. Les verrous sont identifiés.Le chapitre 2 fait l’état de l’art sur la topologie des enroulements constituants le transformateur.Les points forts et les points faibles des différentes topologies sont discutés. Les différents matériaux nécessaires à la réalisation de transformateurs (conducteur, magnétique et isolant) satisfaisant les exigences sur la haute température et la haute fréquence sont identifiés.Enfin, je présenterai la méthode de fabrication LTCC qui constitue une alternative à la technologie développée dans ce mémoire.Le chapitre 3 traite de la modélisation et de la conception des transformateurs en définissant la structure et ses degrés de libertés. L’utilisation des calculs analytiques et de simulations par la méthode des éléments finis permettent d’évaluer des transformateurs à enroulements entrelacés et à enroulements concentriques avec une bonne précision. Le chapitre 4 présente les procédés technologiques permettant la fabrication collective de transformateurs sur substrat magnétique. Il s’agit de l’isolation du substrat, de la croissance électrolytique des enroulements et de l’assemblage final du transformateur.Le chapitre 5 présente les méthodes de caractérisations de différentes propriétés du transformateur : résistance des enroulements en continu, inductances propres d’un enroulement et capacité d’isolement entre enroulements primaire et secondaire. Ces caractérisations permettent de confirmer les calculs analytiques et les hypothèses sur lesquelles ils reposent ainsi que les simulations magnétostatique et électrostatique par éléments finis.Le chapitre 6 permettra de conclure sur les travaux réalisés dans le cadre de cette thèse et d’ouvrir des perspectives pour des travaux futurs / Chapter 1 introduces the topic and its associated context. Locks are identified.Chapter 2 is reviewing state of the art of winding topologies. Their strengths and weaknesses are discussed. Then, materials required for transformers microfabrication (conductors, magnetic material and insulation material) satisfying both high temperature and high frequency criteria are identified. Finally, LTCC fabrication process, an alternative to process used here, is presented.Chapter 3 discuss modelisation and design of transformers by defining the structures and its degrees of freedom. Analytical expressions and finite element analysis allows evaluation of interleaved transformer and tapped transformer within a good accuracy.Chapter 4 present technological process involved in batch-processed fabrication of transformers onto magnetic substrate. Processes are substrate insulation, conductors electrolytic growth of windings and final assembly of transformers.Chapter 5 present characterization methods of several properties of the transformers such as DC winding resistance, self-inductances of windings and isolation capacitance between primary and secondary winding. These characterizations confirm analytical expressions and their underlying hypothesis as well as magnetostatic and electrostatic finite element analysis.Chapter 6 concludes on work achieved during this PhD thesis and opens to further perspectives

This Master thesis deals with the design and implementation of the spinning head heating for the fibers manufacturing. The first part of this thesis compares the problems of spinning head heating by means of radiant heat and electromagnetic induction. The next part of the thesis deals with the design and implementation of the selected induction heating of the spinning head together with its partial peripherals. The thesis continues with the design of a controlled air flow through the chambre and design of reheating fibers. In the following part of the thesis, functionality tests and partial measurements are performed on the device. At the end, the measurement results are evaluated and compared.

abstract: As the world becomes more electronic, power electronics designers have continuously designed more efficient converters. However, with the rising number of nonlinear loads (i.e. electronics) attached to the grid, power quality concerns, and emerging legislation, converters that intake alternating current (AC) and output direct current (DC) known as rectifiers are increasingly implementing power factor correction (PFC) by controlling the input current. For a properly designed PFC-stage inductor, the major design goals include exceeding minimum inductance, remaining below the saturation flux density, high power density, and high efficiency. In meeting these goals, loss calculation is critical in evaluating designs. This input current from PFC circuitry leads to a DC bias through the filter inductor that makes accurate core loss estimation exceedingly difficult as most modern loss estimation techniques neglect the effects of a DC bias. This thesis explores prior loss estimation and design methods, investigates finite element analysis (FEA) design tools, and builds a magnetics test bed setup to empirically determine a magnetic core’s loss under any electrical excitation. In the end, the magnetics test bed hardware results are compared and future work needed to improve the test bed is outlined. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

<p>Tokom poslednje decenije efikasnost DC/DC konvertora, brzina odziva i snaga<br />koju mogu da isporuče ka potrošaču postali su značajan faktor prilikom<br />konstruisanja i izbora ovih kola. U mnogim istraživanjima je potvrđeno da<br />korišćenje višefaznih topologija, uzajamno sprezanje faza i simetrija faza<br />unutar kola igraju značajnu ulogu u unapređenju navedenih karakteristika DC/DC konvertora.<br />U ovoj disertaciji je predstavljen novi simetrični dizajn višefaznih<br />spregnutih induktora kod kojih svi namotaji dele jedno, zajedničko, feritno<br />jezgro. Projektovane strukture su analizirane u laboratorijskim uslovima u<br />frenkvencijskom opsegu od 50 kHz do 40 MHz, a merni rezultati su potvrđeni<br />simulacijama u specijalizovanom softveru. Uzorci su testirani u radnim<br />uslovima pomoću šestofaznog DC/DC buck konvertora. Rezultati testova su<br />pokazali da primena konstruisanih induktorskih struktura dovodi do<br />poboljšanja brzine odziva i porasta efikasnosti test kola.</p> / <p>In the last decade efficiency of DC/DC converters, transient response and<br />delivered power, become important factor in development and selecting<br />these circuits. Numerous researches confirm benefits of using multiphase<br />topologies, mutual coupling of phases and symmetry of phases in the circuit<br />of DC/DC converters.<br />In this dissertation, new symmetric designs of multiphase coupled inductors<br />placed in the same core have been presented. Designed structures have<br />been tested in laboratory conditions in frequency range from 50 kHz to 40<br />MHz, and results have been confirmed by simulations in specialized<br />software. Testing of samples in operating conditions have been performed<br />with six-phase buck converter circuit. These experiments confirm that<br />developed inductors improve transient response and efficiency of test circuit.</p>

Lighting consumes approximately 20-25% of the energy produced worldwide. LED based lighting is rapidly becoming the preferred choice over incandescent and fluorescent based lighting. LEDs have advantages such as high efficacy, long operating lifetime and excellent lumen maintenance. Therefore, to gain benefits from LEDs for lighting purposes, they must be driven with efficient drivers which maintain high LED efficacy and long LED lifetime. A review of existing LED drivers is done, and their advantages and drawbacks are identified. Existing fault-tolerant drivers are also reviewed. Several dimming methods and their effects on the LED efficacy and lifetime are investigated. As a result, a converter with coupled inductors, suitable as an LED driver which has high efficiency and can maintain high LED efficacy, incorporated with a high efficiency dimming method, is chosen. For the proposed LED driver, a comprehensive analysis on the effects of coupling type and coupling coefficient on converter performance is done. This is carried out to establish the best coupled inductor structure and coupling coefficient, for the proposed LED driver. The coupled inductor obtained is used to achieve high LED efficacy and also used to eliminate the need for an output filtering capacitor. This results in a highly compact, high efficiency and low cost LED driver. A lossless method of LED string current sensing is proposed, so that driver efficiency is not negatively impacted. The LED driver and a digital control system are designed, with the fault-tolerant feature incorporated. The LED driver and the control system are simulated and practically implemented. The results obtained show excellent LED driver performance. The fault-tolerant feature can enable the driver to operate under fault conditions, saving repair costs and down time. Additionally, a novel digitally controlled LED driver, which can drive several independent multiple LED loads, is proposed. This novel driver is simulated and practically implemented; with the results showing excellent driver performance. The novel LED driver can simplify and reduce costs of existing LED lighting systems. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

The non-isolated POL converters are widely used in computers, telecommunication systems, portable electronics, and many other applications. These converters are usually constructed using discrete components, and operated at a lower frequency around 200 ~ 600 kHz to achieve a decent efficiency at the middle of 80's%. The passive components, such as inductors and capacitors, are bulky, and they occupy a considerable foot-print. As the power demands increase for POL converters and the limited real estate of the mother board, the POL converters must be made significantly smaller than what they have demonstrated to date. To achieve these goals, two things have to happen simultaneously. The first is a significant increase in the switching frequency to reduce the size and weight of the inductors and capacitors. The second is to integrate passive components, especially magnetics, with active components to realize the needed power density. Today, this concept has been demonstrated at a level less than 5A and a power density around 300-700W/in3 by using silicon-based power semiconductors. This might address the need of small hand-held equipment such as PDAs and smart phones. However, it is far from meeting the needs for applications, such as netbook, notebook, desk-top and server applications where tens and hundreds of amperes are needed. After 30 years of silicon MOSFET development, the silicon has approached its theoretical limits. The recently emerged GaN transistors as a possible candidate to replace silicon devices in various power conversion applications. GaN devices are high electron mobility transistors (HEMT) and have higher band-gap, higher electron mobility, and higher electron velocity than silicon devices, and offer the potential benefits for high frequency power conversions. By implementing the GaN device, it is possible to build the POL converter that can achieve high frequency, high power density, and high efficiency at the same time. GaN technology is in its early stage; however, its significant gains are projected in the future. The first generation GaN devices can outperform the state-of-the-art silicon devices with superior FOM and packaging. The objective of this work is to explore the design of high frequency, high power density 12 V input POL modules with GaN devices and the 3D integration technique. This work discusses the fundamental differences between the enhancement mode and depletion mode GaN transistors, the effect of parasitics on the performance of the high frequency GaN POL, the 3D technique to integrate the active layer with LTCC magnetic substrate, and the thermal design of a high density module using advanced substrates with improved thermal conductivity. The hardware demonstrators are two 12 V to 1.2 V highly integrated 3D POL modules, the single phase 10 A module and two phase 20 A module, all built with depletion mode GaN transistors and low profile LTCC inductors. / Master of Science

Passive components are indispensable in the design and development of microchips for high-frequency applications. Inductors in particular are used frequently in radio frequency (RF) IC's such as low-noise amplifiers and oscillators. High performance inductor has become one of the critical components for voltage controlled oscillator (VCO) design, for its quality factor (Q) value directly affects the VCO phase noise. The optimization of inductor layout can improve its performance, but the improvement is limited by selected technology. Inductor performance is bounded by the thin routing metal and small distance from lossy substrate. On the other hand, the in-accurate inductor modeling further limits the optimization process. The on-chip inductor has been an important research topic since it was first proposed in early 1990's. Significant amount of study has been accomplished and reported in literature; whereas some methods have been used in industry, but not released to public. It is of no doubt that a comprehensive solution is not exist yet. A comprehensive study of previous will be first address. Later author will point out the in-adequacy of skin effect and proximity effect as cause of current crowding in the inductor metal. A model method embedded with new explanation of current crowding is proposed and its applicability in differential inductor and balun is validated. This study leads to a robust optimization routine to improve inductor performance without any addition technology cost and development.

A novel concept of on-chip bondwire inductors and transformers with ferrite epoxy glob coating is proposed, offering a cost effective approach to realize power systems on chip (PSoC) or System-in-Package (PSiP). The concept has been investigated both experimentally and with finite element modeling. Improvement in total inductance is demonstrated for multi-turn bondwire inductors over single bondwire inductors. The inductance and Q factor can be further boosted with coupled multi-turn inductor concept. Transformer parameters including self- and mutual inductance, and coupling factors are extracted from both modeled and measured S-parameters. More importantly, the bondwire magnetic components can be easily integrated into SoC manufacturing processes with minimal changes to the layout, and open enormous possibilities for realizing cost-effective, high current, high efficiency PSoC's or PSiP's. The design guidelines for single bondwire inductors as well as multi-turn inductors are discussed step by step in several chapters. Not only is the innovated concept for bondwire inductor with ferrite ink presented, but also the practical implementation and design rules are given. With all the well defined steps, people who want to use these bondwire inductors with ferrite ink in their PSoC research or products will find it as simple as using commercial inductors. Last but not least, the PSoC concept using a bondwire inductor is demonstrated by building the prototype of dc-dc buck converter IC as well as the whole package. IC and the whole function block are tested and presented in this work.

With solar power and other renewables set to take over the market in the coming decades, maximum power point tracking will be essential to optimizing power output. One underserved topic of research is the effect of inductor current ripple on performance of Maximum Power Point Tracking (MPPT) algorithms. Many new topologies are focused on decreasing the ripple from PV source to increase efficiency and power output. However, not much has been done to show ripple degrading performance of MPPT algorithms. This study uses a boost converter topology to test the performance of constant duty cycle step Perturb and Observe (PO), Incremental Conductance IC, and Constant Voltage (CV) PID over a range of inductor current ripple factor. Inductor current ripple is controlled solely by changing inductance. This study concluded that all three algorithms were quite robust and affected very little over an inductor current ripple factor range of 20% to 40%. One novel finding was increased duty cycle oscillation when the MPPT update and sample speed was faster than the boost converter response.

Energy distribution in a conventional magnetic component is generally not at a designer's disposal. In a conventional toroidal inductor, the energy density is inversely proportional to the square of the radius. Thus, a designer would be unable to prescribe uniform field distribution to fully utilize the inductor volume for storing magnetic energy. To address this problem a new inductor design, called a "constant-flux" inductor, is introduced in this thesis. This new inductor has the core and windings configured to distribute the magnetic flux and energy relatively uniformly throughout the core volume to achieve power density higher than that of a conventional toroidal inductor. The core of this new inductor design is made of concentric cells of magnetic material, and the windings are wound in the gaps between the cells. This structure is designed to avoid crowding of the flux, thus ensuring lower core energy losses. In addition, the windings are patterned for shorter length and larger area of cross-section to facilitate lower winding energy losses. Based on this approach, a set of new, constant flux inductor/transformer designs has been developed. This design set is based on specific input parameters are presented in this thesis. These parameters include the required inductance, peak and rms current, frequency of operation, permissible dc resistance, material properties of the core such as relative permeability, maximum permissible magnetic flux density for the allowed core loss, and Steinmetz parameters to compute the core loss. For each constant flux inductor/transformer design, the winding loss and core loss of the magnetic components are computed. In addition, the quality factor is used as the deciding criterion for selection of an optimized inductor/transformer design. The first design presented in this thesis shows that for the same maximum magnetic field intensity, height, total stored energy, and material, the footprint area of the new five-cell constant-flux inductor is 1.65 times less than that of an equivalent conventional toroidal inductor. The winding loss for the new inductor is at least 10% smaller, and core loss is at least 1% smaller than that in conventional inductors. For higher energy densities and taller inductors, an optimal field ratio of the dimensions of each cell (α = Rimin/Rimax) and a larger number of cells is desired. However, there is a practical difficulty in realizing this structure with a larger number of cells and higher field ratio α. To address this problem, an inductor design is presented that has a footprint area of a three-cell constant-flux inductor (α = 0.6) that is 1.48 times smaller in comparison to an equivalent conventional toroidal inductor. For the same maximum magnetic flux density, height, material, and winding loss, the energy stored in this new three-cell constant-flux inductor (α = 0.6) is four times larger than that of an equivalent conventional toroidal inductor. Finally, new designs for application-specific toroidal inductors are presented in this thesis. First, a constant-flux inductor is designed for high-current, high-power applications. An equivalent constant-flux inductor to a commercially available inductor (E70340-010) was designed. The height of this equivalent inductor is 20% less than the commercial product with the same inductance and dc resistance. Second, a constant-flux inductor design of inductance 1.2 µH was fabricated using Micrometal-8 for the core and flat wire of 0.97 mm x 0.25 mm for the conductor. The core material of this inductor has relative permeability < 28 and maximum allowed flux density of 3600 Gauss. The dc resistance of this new, constant flux inductor was measured to be 14.4 mΩ. / Master of Science