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A power supply is an essential part of all electronic devices. A switching mode power supply is a light weight power solution for most modern electronic equipment. The high frequency transformer is the backbone of modern switched mode power supplies. The skin effect and proximity effects are major problems in high frequency transformer design, because of induced eddy currents. These effects can result in transformers being destroyed and losing their power transferring function at high frequencies. Therefore, eddy currents are unwanted currents in high frequency transformers. Leakage inductance and the unbalanced magnetic flux distribution are two further obstacles for the development of high frequency transformers. Winding structures of power transformers are also a critical part of transformer design and manufacture, especially for high frequency applications. A new planar transformer with a helical winding structure has been designed and can maintain the advantages of existing planar transformers and significantly reduce the eddy currents in the windings. The maximum eddy current density can be reduced to 27% of the density of the planar transformer with meander type winding structure and 33% of the density of the transformer with circular spiral winding structure at an operating frequency of 1MHz. The voltage ratio of the transformer with helical winding structure is effectively improved to 150% of the voltage ratio of the planar transformer with circular spiral coils. With the evenly distributed magnetic flux around the winding, the planar transformer with helical winding structure is excellent for high frequency switching mode power supplies in the 21st Century.

Functional electrical stimulation (FES) devices have direct applications in the realm of rehabilitation engineering, physiotherapy, occupational therapy and medicine for research, diagnostic and therapeutic purposes. This thesis presents a novel electrical stimulator for use in a FES system. The stimulator produces regulated current pulses using two switched mode power supplies (SMPS) in series. The first power stage - a flyback converter - steps up the supply voltage using primary side digital control. The second power stage is a buck converter with output current hysteretic control. An output switched capacitor circuit shapes the current pulses. All pulse variables are programmable and various pulses can be formed for virtually any FES application. Compared to previous FES devices, the pulses generated here are sharper, have faster rise time and the amplitude and temporal characteristics are more tightly regulated. A single channel prototype system is implemented and experimental results are shown.

Functional electrical stimulation (FES) devices have direct applications in the realm of rehabilitation engineering, physiotherapy, occupational therapy and medicine for research, diagnostic and therapeutic purposes. This thesis presents a novel electrical stimulator for use in a FES system. The stimulator produces regulated current pulses using two switched mode power supplies (SMPS) in series. The first power stage - a flyback converter - steps up the supply voltage using primary side digital control. The second power stage is a buck converter with output current hysteretic control. An output switched capacitor circuit shapes the current pulses. All pulse variables are programmable and various pulses can be formed for virtually any FES application. Compared to previous FES devices, the pulses generated here are sharper, have faster rise time and the amplitude and temporal characteristics are more tightly regulated. A single channel prototype system is implemented and experimental results are shown.

This diploma thesis deals with design of welding power supply for MIG / MAG and MMA technique with continuous output current 120 A. The first, theoretical part is devoted to welding process technology, physical characteristics of electric arc and description of individual welding methods. The thesis also deals with the concept of power converter. The design of the switched-mode power supply is based on a full bridge topology. In order to implement advanced controls of welding power supply, the ARM Cortex M4 microprocessor was selected. Due to the large power consumption of the stepper motor for drive the welding wire, an auxiliary switched-mode power supply was also implemented. The documentation describing the realization of the welding power supply and the results of the measurements are in the last part of the thesis. The welding power supply was successfully revived and reached nominal parameters. Inert gas welding has not been tested yet, due to lack of time caused by extensive work in order to complete mechanical realization.

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.

The aim of this work was to design and construct a simple audio amplifier, which would be based of involvement and components used in switching power sources on the maximum degree (for example from usual ATX sources for computer). The main motivation for development is the existence of many old sources that do not use and big interest of users for the construction of home audio amplifiers for small and medium power. Amplifiers based on switching power sources with greater efficiency and less weight than comparable classic amplifiers (working in classes A, B or AB). Their disadvantage is the complicated design and introduction of distortion and spurious signals to the amplified signal. This work will be described a design of simple amplifier, which will minimize these negative effects. For shortcomings and wrong parameters this proposed involvement will be eventually described and implemented design of amplifier in class D.

Les travaux présentés ici proposent des convertisseurs d’énergie à haut rendement et très large dynamique de tension d’entrée, c'est-à-dire capables de fonctionner avec un rendement énergétique élevé sur une plage de tension d’entrée étendue (typiquement de 9V à 200V). De multiples tensions de réseaux sont standards dans l’industrie : elles sont spécifiques à un domaine (aéronautique, ferroviaire, …) et dépendent de la source primaire d’alimentation électrique (batterie d’accumulateurs, génératrice, …). Au sein d’un équipement embarqué, plusieurs réseaux peuvent cohabiter : une alimentation principale 110V et une alimentation de secours sur batterie 12V, par exemple. Le besoin de convertisseurs large dynamique d’entrée est donc une réalité, mais il n’existe sur le marché que peu de convertisseurs capables de réaliser une dynamique d’entrée supérieure à dix. Dans un premier temps, nous avons étudié les enjeux et les problématiques liés à la large dynamique d’entrée, afin de mieux cerner les limitations des topologies de puissance classiques. Nous avons ensuite traité le cas d’une architecture de conversion d’énergie de type série, dont nous avons amélioré le rendement énergétique grâce à l’utilisation de circuits d’aide à la commutation. Cette solution ayant des performances limitées, nous avons proposé de nouvelles architectures de convertisseurs DC/DC, de type parallèle, capables de supporter des dynamiques de tension d’entrée supérieures à vingt et ayant un rendement énergétique élevé (supérieur à 80%). Nous avons également étudié et mis en œuvre des stratégies de commande, numériques et analogiques, permettant de contrôler ces nouvelles topologies complexes. / Power converters are present in virtually every embedded system, but many standards of DC networks exist: the supply voltage is depending on how the power is generated (battery, alternator …) and can range from 12V to more than 115V. When an equipment must comply with a 110V main supply and 12V back-up supply, the use of a wide input voltage range DC/DC converter is mandatory. Since classical switched mode power converters cannot achieve simultaneously high efficiency and wide input voltage range, manufacturers rarely propose DC/DC converters with an input voltage range greater than 10. This work tackles the issue of wide input voltage power conversion. After discussing about designs trade off and problems that stem from a wide input range, we try to improve the overall efficiency of a classical buck-boost converter, by using non dissipative switching-aid circuits. We also proposed a novel two stages power converter capable of dealing with very wide input voltage ranges (more than 20), without a reduction of the power efficiency. Since those new converters are far more difficult to control, some theoretical analysis was performed and some practical tests were done using complex controls laws.

Orientador: Ernesto Ruppert Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T00:56:13Z (GMT). No. of bitstreams: 1 Dias_AgnaldoVieira_M.pdf: 2229736 bytes, checksum: 725a7fa267bc30780c457689e4356336 (MD5) Previous issue date: 2012 / Resumo: O estudo da utilização de conversores CC/CC isolados e elevadores de tensão para a alimentação de moduladores de pulsos é apresentado neste trabalho. Foi selecionada a topologia em ponte completa, dando-se enfoque ao problema das capacitâncias parasitas envolvidas no circuito, que aparecem de forma acentuada em transformadores elevadores de tensão e filtros indutivos de saída e são altamente indesejáveis quando se opera em regime chaveado. Essas capacitâncias são tratadas através de uma forma de amortecimento, onde a energia armazenada nas mesmas é devolvida à fonte primária ao final de cada semiciclo de chaveamento, tentando obter-se menor volume, maior rendimento e menor dissipação de calor no conversor. Além disso, um circuito de regulação de carga é utilizado para garantir uma maior estabilidade de pulso e contornar problemas típicos de moduladores de pulsos utilizados em radares, como o efeito de backswing. O modulador de pulsos utilizado como carga para esse sistema opera com uma tensão de alimentação de 1kV, frequência de repetição de pulsos (PRF) de 585Hz e consome uma potência da ordem de 2,1kW. O conversor CC/CC é alimentado por um barramento CC não regulado de 280V / Abstract: The study of high-voltage isolated DC/DC converters used to supply pulse modulators is presented on this dissertation. The Full Bridge topology was selected, focusing in problems caused by parasitic capacitances in the circuit. This characteristic, which appears sharply in high voltage transformers and in inductors of output filter, is highly undesirable when the circuit is operated in switching mode. These capacitances are handled using a soft commutation technique, where their stored energy are returned to the primary source in the end of each switching cycle, trying to get a low size, high efficiency and low heat dissipation in the converter. Moreover, a charging regulator circuit is used to ensure good pulse stability and avoid typical problems in the pulse modulators use, such as the backswing effect. The pulse modulator used as load for this converter operates with a supply voltage of 1kV, pulse repetition frequency (PRF) of 585Hz and consumes 2.1 kW. The converter input is supplied by a 280V unregulated DC bus / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

The following work deals with a design of power supply testbench with design of their replaceable modules and circuits for their measurement. The final product should be used for faster design and tuning of switching power supplies. In this essay, there is detailed description of switching power supplies, analysis of support circuits and calculations for design. Based on theoretical background and selected parameters, a connection concept will be created. This concept will be validated by a device that will consist of main board, changeable modules and measurement circuits.