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The need for smaller and more efficient power supplies steadily grows. Many power supplies incorporate high-frequency dc-to-dc switching converters to meet these demands. Recently, a new class of switching converters has been introduced which can operate at very high frequencies to further reduce size and increase efficiency. They are called quasi-resonant converters. Previously, the dc characteristics of many of these converters had been determined, assuming ideal components and circuit operating conditions. However, as the frequency of operation increases, the circuit behavior becomes less ideal causing changes in the expected characteristics. This is because resistive losses, semiconductor junction capacitances, and other parasitic (undesirable) elements become more pronounced at higher frequencies. This thesis investigates the effects of parasitic elements on the dc characteristics of several zero-current-switched, buck-derived quasi-resonant converters. For the quasi-resonant buck converter, it is demonstrated that for certain operating conditions the dc voltage gain can increase when parasitic losses are increased. Design guidelines are given for maximizing this converter's efficiency. Various forward quasi-resonant topologies are investigated, and the effects of parasitic elements on circuit operation are highlighted. A dc analysis is performed for the secondary-resonance forward converter, which has not previously been analyzed. This converter can operate either in full-wave or half-wave mode. Its dc voltage gain in full-wave mode is less sensitive to load variations than other resonant forward topologies that only operate in half-wave mode. / Master of Science

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The purpose of a solid state transformer (SST) is to use power electronic converters to mimic the operation of the conventional distribution transformer. These power electronic converters are proposed to overcome the disadvantages of the conventional distribution transformer. The advantages of a SST include near perfect voltage regulation and harmonic isolation between the primary and secondary windings of the transformer. This thesis discusses the design and development of the different converters in a solid state transformer (SST). A prototype modular back-to-back converter is developed for the input and isolation stage of the SST. The isolation stage consists of a high voltage DC-DC converter, which transfers power across the isolation barrier of the SST. This stage is evaluated in the laboratory with special attention being paid to the efficiency of the converter. The second aspect that this thesis addresses is the output stage of the SST, namely a three phase inverter. The discussion of the output stage focuses on the losses occurring in the inverter. The switching device losses are calculated by means of an adapted numerical method as opposed to using conventional analytical methods. The presented numerical method is compared to the existing analytical method and the findings are discussed. A double loop control strategy is implemented for the output stage inverter. The inner current loop utilizes a predictive control strategy. The control analysis of the double loop controller is discussed and evaluated in the laboratory. All the converters that are discussed in this thesis are evaluated in the laboratory and the relevant measurements are included. / AFRIKAANSE OPSOMMING: Die doel van ’n drywingselektroniese transformator (DET) is om drywingselektroniese omsetters te gebruik om die werking van die konvensionele distribusietransformator na te boots. Hierdie drywingselektroniese omsetters word voorgestel ten einde die nadele van die konvensionele distribusietransformator te bowe te kom. Die voordele van ’n DET sluit in: feitlik perfekte regulering van spanning en harmoniese isolasie tussen die primˆere en sekondˆere windings van die transformator. Hierdie tesis bespreek die ontwerp en ontwikkeling van die verskillende omsetters in ’n drywingselektroniese transformator (DET). ’n Prototipe modulˆere rug-aan-rug-omsetter word ontwikkel vir die intree- en isolasiefase van die DET. Die isolasiefase bestaan uit ’n hoogspanning- GS-GS omsetter, wat drywing oor die isolasiegrens van die DET heen oordra. Hierdie omsetter word in die laboratorium ge¨evalueer met besondere aandag aan die doeltreffendheid van die omsetter. Die tweede aspek waarna in hierdie tesis gekyk word, is die uittreefase van die DET, naamlik ’n driefaseomsetter. Die bespreking van die uittreefase fokus egter op die verliese wat in die omsetter voorkom. Die verliese van die skakelaars word bereken deur middel van ’n aangepaste numeriese metode teenoor die gebruik van konvensionele analitiese metodes. Die numeriese metode wat aangebied word, word vergelyk met die bestaande analitiese metode en die bevindings word bespreek. ’n Dubbellus-beheerstrategie word vir die uittreefase-omsetter ge¨ımplementeer. Die binneste stroomlus word ge¨ımplementeer deur van ’n voorspelbare beheerstrategie gebruik te maak. Die beheeranalise van die dubbellusbeheerder word bespreek en in die laboratorium ge¨evalueer. Al die omsetters wat in hierdie tesis bespreek word, word in die laboratorium ge¨evalueer en die relevante metings word ingesluit.

Bakalauro dabą „Elektros srovės, geometrinės optikos, atomo branduolio fizikos mokomieji bandymai ir jų loginė analizė“ susideda iš įvado, 3 skyrių, išvadų ir 28 literatūros šaltinių. Darbo apimtis 66 puslapiai. Pirmoje ir antroje dalyje apžvelgiama pedagogikos ir psichologijos literatūros šaltinių analizė. Trečioje dalyje yra aprašomi XII klasės fizikos kurso mokomieji bandymai ir jų loginės samprotavimo schemos iš: • Elektros srovės (9 eksperimentai). • Geometrinės optikos (8 eksperimentai). • Atomo branduolio fizikos (5 eksperimentai). Samprotavimo schemos planai padeda mokiniams: suprasti demonstracinio bandymo esmę, nustatyti priežasties – pasekmės ryšius ir priklausomybę, gretinti sąlygas ir išvadas, apibendrinti rezultatus, daryti išvadas. / Bachelor's work „Educational Experiments of Electric Current, Geometrical Optics, Atomic Nuclear Physics and Their Logical Analysis” consists of an introduction, 3 chapters, conclusions and 28 references. Working amount 66 pages. In first and second part gives an overview of pedagogy and psychology analysis of literature source. In third part is described education experiments of physics and their logical reasoning schemes of XII class from: • Electric Current (9 experiments). • Geometrical Optics (8 experiments). • Atomic Nuclear Physics (5 experiments). Reasoning schemes help students to: understand the nature of the demo task, determine cause – effect relationships and dependencies, compare conditions and findings, summarize the results, do conclusions.

Power dissipation of integrated circuits is the most demanding issue for very large scale integration (VLSI) design engineers, especially for portable and mobile applications. Use of multiple supply voltages systems, which employs level converter between two voltage islands is one of the most effective ways to reduce power consumption. In this thesis work, a unique level converter known as universal level converter (ULC), capable of four distinct level converting operations, is proposed. The schematic and layout of ULC are built and simulated using CADENCE. The ULC is characterized by performing three analysis such as parametric, power, and load analysis which prove that the design has an average power consumption reduction of about 85-97% and capable of producing stable output at low voltages like 0.45V even under varying load conditions.

M. Tech. (Engineering: Electrical, Department Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology / The global trends towards energy efficiency have facilitated the need for technological advancements in the design and control of power electronic converters for energy processing. The proposed design is intended to make the practical implementation of converters easier. The development of a universal bidirectional galvanic isolated switch module will be used to drive any MOSFET or IGBT in any position in any topology whether the load is AC or DC. Semiconductor switches are required and are also integrated for fast switching times in power converter applications The structure of the power switch module consists of an opto-coupler which will provide an isolation barrier for maximum galvanic isolation between the control circuitry and power stage. It also consists of a high performance gate drive circuit for high speed switching applications with a floating supply. / Telkom South Africa Ltd, TFMC Pty Ltd, M-TEC, THRIP

This work presents a new energy saving technique for modern digital designs. We propose Time Interleaved Multi-Rail (TIMR) - a method for providing two dynamic supply rails to a circuit. This technique uses the first supply rail to mask the transition delay while changing the voltage of the second rail. We examine the design of TIMR as well as the implementation and considerations. We propose a number of control schemes that range from traditional DVFS to "race to sleep". This thesis also shows simulations of the technique using a existing voltage regulator in order to find the time and energy overhead of implementing the design. We find a 100μs switching time delay and 118μJ energy overhead associated with changing the voltage rail. This work concludes with comparisons to current energy saving techniques. / Graduation date: 2012