This thesis focuses mainly on the techniques to achieve high-performance top-emitting OLEDs, regarding device efficiency and lifetime for both non-inverted and inverted structures. It is thus organized as follows: In Chapter 2, the basic physics of organic semiconductor materials are reviewed, including the electronic properties of organic semiconductor materials, molecular excitations and their electronic transitions etc., which are believed to be critical for understanding of the work. Then, the general device physics of OLEDs are reviewed in detail, which includes almost every important electrical and optical process involved in the device. Finally, techniques and methods used to improve the device performance are summarized, which includes electrical doping of charge carrier transport layers. In Chapter 3, all organic materials, experimental techniques, and characterization methods used in this study are briefly described. In the following Chapter 4, techniques that are used for device optimization of non-inverted top-emitting OLEDs are discussed. Also, the mechanism of light outcoupling enhancement by a capping layer is discussed there. In the last part of Chapter 4, the influence of the optical device structure on the intrinsic quantum yield of the emitters is studied. Chapter 5 is focused on inverted top-emitting OLEDs, which are believed to be better applicable with current mainstream n-type amorphous silicon thin film transistor (TFT) technology. In this Chapter, the organic/metal and metal/organic interfaces are investigated in detail and their influence on device performance is discussed. In Chapter 6, the degradation of top-emitting OLEDs is studied, with a focus on the influence of electrode material and electrode thickness on the lifetime of top-emitting devices.

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Position estimation using only active phase voltage and current is presented to perform high accuracy position sensorless control of a SRM drive. By extracting the amplitude of the first switching harmonic terms of phase voltage and current for a PWM period through Fourier analysis, flux-linkage and position are estimated without external hardware circuitry such as a modulator and demodulator, resulting in increasing cost, as well as large position estimation error produced when the motional back emf is ignored near zero speed. Hence the proposed position estimation scheme covers the entire speed range including the standstill under various loads and it has high resolution information depending on switching frequency. Fourier series and Fast Fourier transform are employed to decompose the phase voltage and current into its first switching harmonic. A two-phase SRM drive system, consisting of an asymmetrical converter and a conventional closed-loop PI current controller, is utilized to validate the performance of the proposed position estimation scheme in comprehensive operating conditions. The estimated values very closely track the actual values in dynamic simulations and experiments. It is shown that the proposed position estimation scheme using Fourier analysis is sufficiently accurate and works satisfactorily at various operating points. This research also proposes an accurate self-inductance measurement method. In general, when applying circulating currents within the body of a ferromagnetic material under conditions of a time varying magnetic flux, the effects of eddy current losses and resistance changes due to heating decrease the magnetic field strength and thereby the reduced magnetic field decreases the magnetic flux-linkage of SRM. These losses make a challenge to the measurement of magnetic characteristics of SRM. These motives lead to propose a measurement methodology based on 60 Hz sinusoidal excitation using a variable AC power supply, which provides an alternative to time domain integration approaches for self-inductance or flux-linkage measurement as well as eliminates error arising from thermal and eddy currents effects. The validation of the proposed method is verified with the correlation between the measurement and FEA results of flux-linkage. Furthermore, this research proposes the solutions for low cost and high efficiency drive systems, consisting of a split AC converter and a two-phase SRM. Its performance is analyzed and verified with experiments at the rated speed under various loads. It is believed that this drive system combined with the proposed position estimation scheme using Fourier analysis is a strong contender to be a low cost motor drive system with single switch per phase having comparable efficiency and acoustic noise level as an asymmetric drive system. / Ph. D.

With the development of solar energy, power conversion systems responsible for energy delivering from photovoltaic (PV) modules to ac or dc grid attract wide attentions and have significantly increased installations worldwide. Modular power conversion system has the highest efficiency of maximum power point tacking (MPPT), which can transfer more solar power to electricity. However, this system suffers the drawbacks of low power conversion efficiency and high cost due to a large number of power electronics converters. High-power density can provide potentials to reduce cost through the reduction of components and potting materials. Nowadays, the power electronics converters with the conventional silicon (Si) based power semiconductor devices are developed maturely and have limited improvements regarding in power conversion efficiency and power density. With the availability of wide bandgap devices, the power electronics converters have extended opportunities to achieve higher efficiency and higher power density due to the desirable features of wide bandgap devices, such as low on-state resistance, small junction capacitance and high switching speed. This dissertation focuses on the application of wide bandgap devices to the dc-dc power conversion for the modular PV applications in an effort to improve the power conversion efficiency and power density. Firstly, the structure of gallium-nitride (GaN) device is studied theoretically and characteristics of GaN device are evaluated under testing with both hard-switching and soft-switching conditions. The device performance during steady-state and transitions are explored under different power level conditions and compared with Si based devices. Secondly, an isolated high-efficiency GaN-based dc-dc converter with capability of wide range regulation is proposed for modular PV applications. The circuit configuration of secondary side is a proposed active-boost-rectifier, which merges a Boost circuit and a voltage-doubler rectifier. With implementation of the proposed double-pulse duty cycle modulation method, the active-boost-rectifier can not only serve for synchronous rectification but also achieve the voltage boost function. The proposed converter can achieve zero-voltage-switching (ZVS) of primary side switches and zero-current-switching (ZCS) of secondary side switches regardless of the input voltages or output power levels. Therefore, the proposed converter not only keeps the benefits of highly-efficient series resonant converter (SRC) but also achieves a higher voltage gain than SRC and a wide range regulation ability without adding additional switches while operating under the fixed-frequency condition. GaN devices are utilized in both primary and secondary sides. A 300-W hardware prototype is built to achieve a peak efficiency of 98.9% and a California Energy Commission (CEC) weighted efficiency of 98.7% under nominal input voltage condition. Finally, the proposed converter is designed and optimized at 1-MHz switching frequency to pursue the feature of high-power density. Considering the ac effects under high frequency, the magnetic components and PCB structure are optimized with finite element method (FEM) simulations. Compared with 140-kHz design, the volume of 1-MHz design can reduce more than 70%, while the CEC efficiency only drops 0.8% at nominal input voltage condition. There are also key findings on circuit design techniques to reduce parasitic effects. The parasitic inductances induced from PCB layout of primary side circuit can cause the unbalanced resonant current between positive and negative half cycles if the power loops of two half cycles have asymmetrical parasitic inductances. Moreover, these parasitic inductances reflecting to secondary side should be considered into the design of resonant inductance. The parasitic capacitances of secondary side could affect ZVS transitions and increase the required magnetizing current. Because of large parasitic capacitances, the dead-time period occupies a large percentage of entire switching period in MHz operations, which should be taken into consideration when designing the resonant frequency of resonant network. / Doctor of Philosophy / Solar energy is one of the most promising renewable energies to replace the conventional fossils. Power electronics converters are necessary to transfer power from solar panels to dc or ac grid. Since the output of solar panel is low voltage with a wide range and the grid side is high voltage, this power converter should meet the basic requirements of high step up and wide range regulation. Additionally, high power conversion efficiency is an important design purpose in order to save energy. The existing solutions have limitations of narrow regulating range, low efficiency or complicated circuit structure. Recently, the third-generation power semiconductors attract more and more attentions who can help to reduce the power loss. They are named as wide band gap devices. This dissertation proposed a wide band gap devices based power converter with ability of wide regulating range, high power conversion efficiency and simple circuit structure. Moreover, this proposed converter is further designed for high power density, which reduces more than 70% of volume. In this way, small power converter can merge into the junction box of solar panel, which can reduce cost and be convenient for installations.

With the development of information technology, the market for power management of telecom and computing equipment keeps increasing. Distributed power systems are widely adopted in the telecom and computing applications for the reason of high performance and high reliability. Recently industry brought out aggressively high efficiency requirements for a wide load range for power management in telecom and computing equipment. High efficiency over a wide load range is now a requirement. On the other hand, power density is still a big challenge for front-end AC/DC converters. For DPS systems, front-end AC/DC converters are under the pressure of continuous increasing power density requirement. Although increasing switching frequency can dramatically reduce the passive component size, its effectiveness is limited by the converter efficiency and thermal management. Technologies to further increase the power density without compromising the efficiency need to be studied. The industry today is also at the beginning of transferring their design from analog control to full digital control strategy. Although issues are still exist, reducing components count, reducing the development cycle time, increasing the reliability, enhancing the circuit noise immunity and reducing the cost, all of these benefits indicate a great potential of the digital control. This thesis is focusing on how to improve the efficiency and power density by taking the advantages of the digital control. A novel Ï /2 phase shift two Channel interleaving PFC is developed to shrink the EMI filter size while maintain a good efficiency. A sophisticated power management strategy that associates with phase shedding and adaptive phase angle control is also discussed to increase the efficient for the entire load range without compromising the EMI filter size. The method of current sampling is proposed for Ï /2 phase shift two Channel interleaving PFC and multi-channel adaptive phase angle shift PFC is proposed to accurately extract the average total current information. A noise free current sampling strategy is also proposed that adjusting the sampling edge according to duty cycle information. An isolated ZVS dual boost converter is proposed to be the DC/DC stage of the front-end converter. This PWM converter has similar performance as the LLC resonant converter. It has hold up time extension capability without compromising the normal operation efficiency. It can achieve ZVS for all the switches. The current limit and SR implementation is much easier than LLC. State plane method, which potentially can be extent to other complex topologies, is used to fully study this circuit. All the operation modes are understood through the state plane method. The best operation mode is discovered for the front end applications. Light load efficiency is improved by the proposed pulse skipping method to guarantee the ZVS operation meanwhile reduce the switching frequency. Current limit operation is also proposed to restrict a best operation mode by fully taking the advantage of digital control that precisely control the circuit under the over current condition. High efficiency high power density is achieved by new topology, innovative interleaving, and the sophisticated digital control method. / Master of Science

Les fortes capacités actuelles et envisagées des futurs liens satellites de communication pour la 5G conduisent les signaux traités dans les charges utiles à présenter simultanément d'importantes variations d'amplitude (PAPR>10dB) et de très larges bandes passantes instantanées (BW>1GHz). A l'intérieur du sous-système d'émission hyperfréquence, le fonctionnement du module d'amplification de puissance se trouve très contraint par les formes d'ondes véhiculées, il se présente comme l'un des postes de consommation énergétique des plus importants, et ayant le plus d'impact sur l'intégrité du signal émis. Dans ce contexte, les fonctions dédiées au traitement numérique des signaux et couramment implémentées par le processeur numérique (telles que le filtrage, la canalisation, et éventuellement la démodulation et la régénération des signaux bande de base) embarquées dans les charges utiles, représentent une solution à fort potentiel qui permettrait de relâcher les contraintes reportées sur la fonction d'amplification de puissance afin de gérer au mieux la ressource électrique allouée. Ces travaux de thèse proposent d'étudier les potentialités d'amélioration du fonctionnement en rendement et linéarité d'un amplificateur de type Doherty à double entrée de gamme 20W en technologie GaN et fonctionnant en bande C. La combinaison des signaux de puissance sur la charge RF est optimisée par une distribution optimale des signaux en amplitude et phase à l'entrée par des moyens numériques de génération. Dans un premier temps une méthodologie de conception large bande d'un amplificateur Doherty est introduite et validée par la conception d'un démonstrateur en bande C. Dans un second temps, l'outil expérimental permettant l'extraction des lois optimales de distribution d'amplitude et de phase RF est présenté en détail, et la caractérisation expérimentale du dispositif en double entrée est réalisée puis comparée aux simulations. Finalement, en perspective à ces travaux, une étude préliminaire des potentialités de l'architecture Doherty à double entrée pour la gestion d’une désadaptation de la charge de sortie (gestion de TOS) est menée et des résultats sont mis en avant. / The high capabilities of current and future 5G communication satellite links lead the processed signals in the payloads to simultaneously exhibit large amplitude variations (PAPR>10dB) and wide instantaneous bandwidths (BW>1GHz). Within the microwave transmission subsystem, the operation of the power amplification stage is highly constrained by the transmitted waveforms, it is one of the most energy-consuming module of the payload affecting as well the integrity of the transmitted signal. In this context, the functions dedicated to digital signal processing and currently implemented by the digital processor (such as filtering, channeling, and possibly the demodulation and regeneration of baseband signals) embedded in the payloads, represent a potential solution that would reduce the constraints reported on the power amplification function and help to manage the allocated power ressource. This work proposes a study on the capability of dual input power amplifier architectures in order to manage the efficiency-linearity trade-off over a wide bandwidth. This study is carried out on a 20W GaN Doherty demonstrator operating in C band. The combination of the output signals on the RF load is managed by an optimal amplitude and phase distribution that is digitally controlled at the input. Firstly, a wideband design methodology of Doherty amplifier is introduced and validated on a C band demonstrator. In a second time the experimental tool allowing the extraction of amplitude and phase input distributions is presented, the dual input characterization is achieved and compared with simulation results. Finally, in perspective of this work, a preliminary study of the capabilities of the digital Doherty for the management of an output load mismatch (VSWR management) is carried out and the results are put forward.

O presente trabalho objetiva, a partir de dados coletados dos motores elétricos em regime de trabalho, dar sua contribuição ao estudo de conservação de energia elétrica numa planta industrial. Apresenta-se o motor elétrico trifásico de indução e as diversas questões relativas ao seu uso industrial, para então, demonstrarem os parâmetros elétricos obtidos. Elaborou-se um trabalho de campo, que possibilita à análise da eficiência energética no uso de motores elétricos em uma fábrica de papel e cosméticos. A partir de medidas dos parâmetros elétricos como: corrente e tensão, mais os dados de catálogos do fabricante, chegaram-se aos valores de rendimento, fator de potência e fator de utilização, para diversas condições de carga dos motores. Caso o fator de utilização seja inferior a 75%, um estudo comparativo permitirá as decisões de substituição dos motores super dimensionados. Os dados são usados para as seguintes análises: qual a possível conservação de energia elétrica para cada setor, se os motores fossem substituídos por unidades de alto rendimento?; qual a viabilidade de cada setor realizar as trocas imediatas por motores de alto rendimento?; qual à economia de energia elétrica por setores em (R$/dia), utilizando motores de alto rendimento?; em quanto tempo obteríamos o retorno desse investimento? Alguns recursos de informática foram utilizados nos cálculos realizados. Os resultados indicam que o potencial de conservação de energia elétrica em motores deve ser melhor explorado e de forma mais consciente. / The objective of the present research, from a data set of electric motor collected in a regimen of work, give its contribution to the study on industrial electrical motors’ energy saving. It present the three-phase induction motor, the various issues of its industrial use and the electric parameter set collected are then presented. Field of work was elaborated, wich allowed the analysis of the energy efficiency in the use of electric engines in industry of paper and cosmetics. Given the measurements of current and tension, plus the data from the manufacter’s catalogs, values of efficiency were obtained, power factor and utilization factor, for diverse conditions of engine load. But in case the utilization factor is less than 75%, a comparative study allowed the decisions of substitution of the poorly dimensioned engines. The data are analyzed in ways: 1)What would be the energy save to each sector, if motors were changed for high efficient units? 2)What would be the viable to each sector to replace immediately the existing motors for high efficient? 3)What would be the energy save to each sector in (R$/day), using high efficient motors? 4)How much time would be the return of the investiment?. Some resources of computer technology were used in the calculations. The results showing the electric energy saving potential in motor would be better use to advantage and more conscientions form.

O presente trabalho objetiva, a partir de dados coletados dos motores elétricos em regime de trabalho, dar sua contribuição ao estudo de conservação de energia elétrica numa planta industrial. Apresenta-se o motor elétrico trifásico de indução e as diversas questões relativas ao seu uso industrial, para então, demonstrarem os parâmetros elétricos obtidos. Elaborou-se um trabalho de campo, que possibilita à análise da eficiência energética no uso de motores elétricos em uma fábrica de papel e cosméticos. A partir de medidas dos parâmetros elétricos como: corrente e tensão, mais os dados de catálogos do fabricante, chegaram-se aos valores de rendimento, fator de potência e fator de utilização, para diversas condições de carga dos motores. Caso o fator de utilização seja inferior a 75%, um estudo comparativo permitirá as decisões de substituição dos motores super dimensionados. Os dados são usados para as seguintes análises: qual a possível conservação de energia elétrica para cada setor, se os motores fossem substituídos por unidades de alto rendimento?; qual a viabilidade de cada setor realizar as trocas imediatas por motores de alto rendimento?; qual à economia de energia elétrica por setores em (R$/dia), utilizando motores de alto rendimento?; em quanto tempo obteríamos o retorno desse investimento? Alguns recursos de informática foram utilizados nos cálculos realizados. Os resultados indicam que o potencial de conservação de energia elétrica em motores deve ser melhor explorado e de forma mais consciente. / The objective of the present research, from a data set of electric motor collected in a regimen of work, give its contribution to the study on industrial electrical motors’ energy saving. It present the three-phase induction motor, the various issues of its industrial use and the electric parameter set collected are then presented. Field of work was elaborated, wich allowed the analysis of the energy efficiency in the use of electric engines in industry of paper and cosmetics. Given the measurements of current and tension, plus the data from the manufacter’s catalogs, values of efficiency were obtained, power factor and utilization factor, for diverse conditions of engine load. But in case the utilization factor is less than 75%, a comparative study allowed the decisions of substitution of the poorly dimensioned engines. The data are analyzed in ways: 1)What would be the energy save to each sector, if motors were changed for high efficient units? 2)What would be the viable to each sector to replace immediately the existing motors for high efficient? 3)What would be the energy save to each sector in (R$/day), using high efficient motors? 4)How much time would be the return of the investiment?. Some resources of computer technology were used in the calculations. The results showing the electric energy saving potential in motor would be better use to advantage and more conscientions form.