Characterization of capacitors for power circuit decoupling applications

Increase in switching speeds of power semiconductors have resulted in the need for decoupling capacitors to be placed across the DC bus, intimate to the semiconductor module in power converter circuits. These capacitors prevent overvoltages across the power semiconductor devices during switching transients. Moreover, they also reduce the high frequency content of the current flowing through the power circuit interconnection, thereby reducing electromagnetic interference. Various types of capacitors typically used for these applications include: metallized polypropylene film; foil and metallized polypropylene film; multilayer film; multilayer ceramic; and metallized polycarbonate. The parasitic properties of these capacitors including their ESR and ESL play an important role in proper application. The objective of this paper is to present a detailed characterization of the application and comparison of the various capacitors for DC bus decoupling. Characterization methodology, simulation results and design guidelines are presented in the paper.