The Most Important Concept In EMI Diagnosis

Focus:

EMI topics have been studied to the point where the underlying issues are understood, techniques for dealing with EMI are well established, and this knowledge is readily available to the engineering community. Nevertheless, EMI engineers still feel frustrated at times with theories and real world measurements. One of the sources of this frustration is the conflict between the log scaling required to measure and assess EMI and the engineer’s “linear” mindset. It is important for engineers to adapt to log scales in order to apply EMI theories on diagnostic techniques effectively, gain valuable experience in these areas, and to obtain more consistent results. This article discusses some common mistakes that engineers make in interpreting log-scale EMI measurements, explains why different engineers performing similar measurements draw different conclusions about the causes of the EMI, why the search for a “dominant” noise source is counterproductive, and describes a more effective approach to addressing EMI issues in power supply designs. The author uses power supply EMI models and simulations to illustrate the discussion.

What you’ll learn:

• How to diagnose sources of EMI in power supply designs
• How to correctly interpret log-scale EMI measurements

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Author & Publication:

Franki Poon, PowerELab, Shatin, N.T., Hong Kong, How2Power Today, Sep 15 2014

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