published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 163-183).

This work presents the modeling and analysis of EMI and thermal performance for switch power supply by using the CAD tools. The methodology and design guidelines are developed. By using a boost PFC circuit as an example, an equivalent circuit model is built for EMI noise prediction and analysis. The parasitic elements of circuit layout and components are extracted analytically or by using CAD tools. Based on the model, circuit layout and magnetic component design are modified to minimize circuit EMI. EMI filter can be designed at an early stage without prototype implementation. In the second part, thermal analyses are conducted for the circuit by using the software Flotherm, which includes the mechanism of conduction, convection and radiation. Thermal models are built for the components. Thermal performance of the circuit and the temperature profile of components are predicted. Improved thermal management and winding arrangement are investigated to reduce temperature. In the third part, several circuit layouts and inductor design examples are checked from both the EMI and thermal point of view. Insightful information is obtained. / Master of Science

Conducted Electromagnetic Interference (EMI) is a major cause of concern in switchmode power supplies (SMPS) which commonly use standard pulsewidth modulation (PWM). In this thesis, Sigma-Delta (����) modulation is proposed as an alternative switching technique to reduce conducted EMI from SMPS. The result of using ���� modulation is a spread in the spectrum of the conducted emissions so that large concentrations of power at discrete frequencies are avoided. Experimental time-domain waveforms and spectra of the switching function from first-order and second-order ���� modulators are presented to prove the viability of the scheme in EMI mitigation. These modulators are then applied to an off-the-shelf computer power supply and experimental results using FCC-specified methods show a reduction of roughly 5-10dB in EMI emissions over standard PWM modulators. / Graduation date: 1999

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (ℓ. 164-173)

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 14, 2008) Vita. Includes bibliographical references.

Dissertation (Ph.D.)--Auburn University, / Abstract. Vita. Includes bibliographic references (p.109-113).

Thesis (M.S. in electrical engineering)--Washington State University, December 2006. / Includes bibliographical references (p. 57-59).

Electromagnetic Interference (EMI) problems in switching power supplies have been traditionally treated with cut-and-try approaches. In recent years, advancement has been made to better understand the problems and minimize the cut-and-try portion of the design process. However, there are still phenomena difficult to explain in many practical design situations. Often, the problems may be solved by luck but many puzzles remain unsolved. If not fully understood, these puzzles are very likely to come back to haunt the designers. According to the conventional theory, there are two modes of noise: the Differential-Mode (DM) noise and the Common-Mode (CM) noise. Recently, a new noise-coupling mode called Non-Intrinsic Differential-Mode (NIDM) noise was uncovered accidentally in the process of explaining certain EMI filter action [1]. This phenomenon has never been thoroughly studied. The focus of the present thesis is to investigate the NIDM phenomenon and its implications to practical EMI filter design issues. The generation mechanism and basic characteristics of this phenomenon will be briefly reviewed, which is crucial to the understanding of the remaining parts of the research. Two essential diagnostic tools are introduced. One is the DM/CM noise separator and the other is the zero-span mode operation of a spectrum analyzer. The results of the investigation will be presented. The results will be presented using practical examples, which tie the phenomenon to filter design issues. In some examples, explanations are given to dispel the puzzles commonly encountered in the practice. A filter design procedure is suggested for off-line power supplies. This procedure incorporates the NIDM phenomenon into an existing design procedure. Only first-order and second-order filter topologies are included in the discussion. / Master of Science