PLF Design for DC-DC Converters Based on Accurate IL Estimations

Abstract

Even though today’s electromagnetic compatibility (EMC) standards and measurement techniques set specific limitations and a clear methodology to measure the conducted emissions (CE) of equipment under tests (EUTs), the design methodology of a suitable power-line filter (PLF) to solve non-compliance is, in general, neither accurate nor efficient. This is due to different reasons, such as unknown actual load and line impedances, unknown dominant mode in the CE, and/or inappropriate instrumentation for the appropriate measurements. The objective of this paper is to investigate if different topologies of switching mode power supplies (SMPSs) lead to different PLF structures. For the sake of exemplification, the analysis is focused on switched-mode DC-DC converters. From an EMC point of view, these devices can be completely modeled by means of Scattering (S)–parameter and CE measurements. Additionally, an analysis of their circuit models has been performed to allow a better comprehension of their characterization. In this paper, the circuit models of three different types of DC-DC converters are presented, and their component values (including nonlinearities and parasitic effects introduced by the actual behavior of the circuit elements) are estimated using the S-parameter characterization. Then, a new methodology for PLF design, based on accurate insertion loss (IL) estimations, is applied to obtain the optimal PLF for one of the converters. This methodology is experimentally tested and validated.