Comprehensive Analysis of Filter Inductor Topology on Common-Mode Conducted Emissions in Buck and Boost Converters

Abstract:
Improvements in wide-bandgap semiconductor performance are exacerbating common-mode emissions and electromagnetic compatibility issues in dc-dc converters. This paper applies a general common-mode modeling approach to rigorously identify emissions sources and the effects of typical filter inductor design asymmetry in buck and boost converters. Analysis of the resulting common-mode equivalent models corroborates the established benefit of balancing the filter inductors for the boost converter. In contrast, it is shown why the same balanced design greatly increases emissions in the buck converter using straightforward circuit analysis techniques. Finally, a set of empirical tests are conducted utilizing a prototype 1-kW GaN-based converter system to validate the model predictions and analysis.