High Accuracy Calorimetric Measurements and Modeling of Ceramic Capacitor Losses Under Large Ripple Operation

Recent work on hybrid and resonant switched-capacitor converters, as well as on flying capacitor multi-level converters, have demonstrated exceptionally high efficiencies and power densities, through the use of multilayer ceramic capacitors (MLCCs). However, when used in such converters as the main energy transfer components, the capacitors experience high voltage and current ripple, under large dc bias. Yet, capacitor characterization today is typically done only with small signal excitation, and under low or no dc bias, yielding highly inaccurate loss models when the capacitor is used as the main energy transfer element. This work presents a technique for obtaining detailed loss characterizations of MLCCs under more realistic operating conditions, and presents experimental results from a number of different capacitors. Finally, several simple loss models are presented and compared which helps guide practicing engineers in the design of capacitor-based power converters.