Reduction of electromagnetic interference due to electric field coupling on printed circuit board
The broad applications of power electronic equipment improve the power factor and efficiency of the power converters, but they also generate electromagnetic noise to pollute the environment and the power system network. The development of power filter technology provides an effective solution towards the power frequency harmonics. Through its research, this thesis contributes to the development of high frequency electromagnetic interference (EMI) in switch mode power supply (SMPS).
Traditional EMI reduction technologies relies on filtering and shielding, which are generally applied to the product by simple design rules or integrated simulation software. The high voltage switching characteristics of the switch mode power supply and the near field electric coupling between the PCB traces have a significant impact on the final EMI emission of the product. A novel approach technique to reduce such the electric coupling is mandatory.
This thesis describes the measurement method used to assess the electric field coupling and the level of significance. The measurement result confirms the contribution of the electric coupling in the overall EMI generated from the SMPS. Extensive experiments verify the effectiveness of EMI reduction techniques.
A thorough analysis on the electric field models of the PCB traces concludes the capacitance effect determines a high portion of the EMI generated from the SMPS. Nevertheless, the calculation of capacitance is time consuming. Any alternation in the geometry of the circuit requires the whole system to be re-calculated the whole system. During the experimental stage, a de-coupled field calculation closely resembles the
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capacitance. The index of the electric field coupling is then defined as the "Coupling Index". It comprises the benefits fast calculation and independence of the changes in the PCB geometry.
Utilising the "Coupling Index", a computer simulation tool is developed to provide a quantitative comparison on the noise coupling as well as the EMI as a result of electric field coupling. On the whole, the simulation tool combined with artificial intelligence forms an integrated simulation software with automatic trace routing. The software optimises the effects of the electric field coupling between the PCB traces to reduce the EMI generation.
In summary, this thesis demonstrates the EMI due to electric field coupling in SMPS and develops an automatic software package to reduce the coupling effect with the aid of artificial software. This contributes to the ultimate PCB auto-routing tools with all EMI parameters taken into consideration.
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School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:electromagnetic interference electronic circuits noise
Date of Publication:01/01/2002