Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [90]-92).

No description available.

No description available.

Thesis (Ph. D.)--Carleton University, 1996. / Includes bibliographical references. Also available in electronic format on the Internet.

M.Ing. (Electrical & Electronic Engineering) / The technology of the use of electronic devices as power switches is still being developed. Because of the increasing demand for low mass and cost, the switching frequency must be as high as possible. The limiting factor for the frequency is the energy loss which is dissipated in the semiconductor crystal during each switching-transient. If tllis switching loss can be reduced, a higher frequency can be obtained. The switching loss is due to the non-instantaneous switching process of the semiconductor device. For the reduction of this switching loss, the device must be switched as fast as possible via its control-electrode. Further improvement can be obtained through the use of snubber networks. This thesis considers the bipolar high-voltage transistor as a power switch. The unfavourable switching loci of the transistor- switch is discussed in chapter 1. In chapter 2 the basedrive during transistor turn-off is investigated, in order to reduce the turn-off time. The following chapters de;al with the use of snubber circuits, which relieve the transistor during turn-on and turn-off. The advantages, as well as the disadvantages and limitations of snubbers are discussed. After the linear turn-off and turn-on snubbers have been treated, the non-linear turn-on snubber, which uses a saturable inductor, will be considered from an experimental point of view. The results show that this snubber is very effective in relieving the transistor during turn-on. In chapter 7 the non-linear turn-off snubber is treated on an experimental as well as on a mathematical bas e . Cri teria, which must be satisfied for realisation of a practical nonlinear capacitor, is also laid down. Because of the fact that a first order snubber is always loading the transistor during the complimentary switchin,]-transient, chapter 8 deals with a second order snubber, which consists of both a capacitor and an inductor. Experimentally it was found that the turn-on time is reduced with the use of a turn-on snubber, while the turn-off time is increased with the use of a turn-off snubber. In chapter 9 the physical behaviour of the switching processes is investigated, after which the influences of the snubbers on the switching times is explained qualitatively...

Low-frequency noise has been measured on commercial power MOSFETs. These devices, fabricated with the VDMOS structure, exhibit a 1/f type noise spectrum. The interface state density obtained from noise measurements was compared with that obtained from the subthreshold-slope method. Reasonable agreement was found between the two measurements. The radiation effects on the noise power spectral density were also investigated. The results indicated that the noise can be attributed to the generation of interface traps near the Si-SiO₂ interface. The level of interface traps generated by radiation was bias dependent. The positive gate bias gave rise to the largest interface-trap density.

A simulation program has been developed to facilitate the investigation and analysis of power semiconductor devices under the reverse-bias condition. The electrostatic potential distribution is solved by using Poisson's equation alone, with particular attention to the neighborhood of avalanche breakdown. Because of its generality and efficiency, the program emerges as a powerful engineering tool for the design of power devices incorporating special junction termination techniques. Results are presented for a DMOS structure to illustrate the improvement in breakdown voltage when a field plate is applied. Numerical solution techniques for solving elliptic partial differential equations in a multi-material domain are discussed. The discretization of this domain is nonuniform in general due to its highly nonuniform physical parameters. By careful selection of grid lines near interfaces, the difference equation coefficients are considerably simplified. The resultant matrix of coefficients is symmetric even though Neumann boundary conditions are specified.

Thesis (Ph.D.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-21Bitstream added on 2014-06-13T20:29:10Z : No. of bitstreams: 1 melo_ga_me_ilha.pdf: 6893159 bytes, checksum: a70518b6cdac1869ab5705bc69904150 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta o desenvolvimento e implementação de um emulador para a característica estática de saída (Tensão versus Corrente) equivalente àquela de fontes de energia com células combustível. O emulador apresenta como vantagens, em relação à aquisição de uma FC, o baixo custo, o reduzido espaço físico e a flexibilidade via software para a implementação de diversas características baseadas em diferentes tipos de células combustível. Neste sentido, o emulador proposto permite a realização de ensaios preliminares durante a fase de projeto e os testes dinâmicos dos subsistemas de condicionamento de energia, sem a necessidade do acoplamento com o sistema de geração à células combustível, reduzindo-se os custos associados a estes testes laboratoriais. O emulador proposto consiste em um conversor Buck isolado Full-Bridge, com potência de saída de 2kW e alimentação via barramento de 400VCC, permitindo a emulação da característica nominal de saída de um conjunto de células tipo PEM (Proton Exchange Membrane - Membrana de Troca Protônica), em uma faixa de tensão de saída variando entre 32VCC e 72VCC, dependendo da corrente drenada pela carga. O circuito principal de controle é realizado através... / This work presents a design and implementation of an emulator to the static output characteristic (Voltage versus Current) that is similar to Fuel Cell generators. There are many advantages on using the Fuel Cell emulator. The emulator is cheaper, smaller and more flexible than the real Fuel Cell systems, because it is possible to emulate different characteristics through the use of a computer. In this context, a Fuel Cell emulator is proposed in this work in order to allow laboratory testes in the power conditioning system during its design and development stage. The proposed emulator is an insulated Full-Bridge converter with Buck operation, 2kW output power and 400VCC input voltage. This emulator achieves the output characteristic of a PEM (Proton Exchange Membrane) Fuel Cell stack with output voltage range of 32VCC to 72VCC, depending on the output current. The main control circuit is based on FPGA (Field Programmable Gate Array) and VHDL (Very High Speed Integrated Circuit Hardware Description Language) language. The experimental results demonstrate that the proposed emulator achieves the output static characteristic of the PEMFC Fuel Cell System and this output characteristic can be easily modified in order to obtain another desirable static... (Complete abstract click electronic access below)

Two MOS-Bipolar composite power semiconductor switching devices are proposed and experimentally demonstrated. These devices feature high voltage and high current capabilities, fast switching speeds, simple gate drive requirements, savings in chip area, reverse bias second breakdown ruggedness and large safe operating areas. Application characteristics of the devices for high frequency power inverter circuits are discussed. Monolithic integration of the two composite devices are also proposed. / Ph. D.