The Engineer’s Guide To EMI In DC-DC Converters (Part 14): Behavioral Noise Modeling

Focus:

EMI modeling usually involves the characterization of noise sources and the essential coupling paths, and these models can be physics-based or behavioral models. The latter enable faster and more stable simulations. Part 14 of this series provides an introduction to and overview of behavioral EMI models, where a compact association of noise sources and impedances identifies the dc-dc converter and its external EMI behavior. This article will discuss two types of behavioral models—two-terminal (one-port), decoupling-mode models and three-terminal (two-port) models. Since the latter type provides greater accuracy, details on how to extract parameters for the three-terminal models will be presented. There are two methods for extracting these parameters—one involves taking measurements across the converter’s input terminals with shunt impedances attached and power applied to the converter, the other involves measurement of converter input impedances with power removed. Both methods will be described here. The article concludes by comparing DM and CM noise predictions obtained for a three- terminal model of a 50-W buck converter with bench measurements.

What you’ll learn:

• How to create two-terminal and three-terminal behavioral EMI models of dc-dc converters
• How to extract parameters for three-terminal behavioral EMI models of dc-dc converters

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Author & Publication:

Timothy Hegarty, Texas Instruments, Phoenix, Ariz., How2Power Today, Aug 14 2020

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