Type of Document Master's Thesis Author Qu, Song Author's Email Address firstname.lastname@example.org URN etd-022199-114952 Title Non-Intrinsic Differential-Mode Noise in Switching Power Supplies and Its Implications to EMI Filter Design Degree Master of Science Department Electrical and Computer Engineering Advisory Committee
Advisor Name Title Chen, Dan Y. Committee Chair Borojevich, Dushan Committee Member Huang, Alex Q. Committee Member Keywords
- Switching Power Supply
Date of Defense 1999-02-12 Availability unrestricted AbstractABSTRACT
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 .
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
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.
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