Characterization and Modeling of Ceramic Capacitor Losses Under Large Signal Operating Conditions

Abstract

Recent work on hybrid switched-capacitor converters has 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 often under large dc voltage bias. Yet, capacitor characterization is typically done only with small signal excitation, and under low or no dc bias, yielding highly inaccurate loss models. This work presents a technique for obtaining detailed loss characterizations of MLCCs under more realistic operating conditions through a carefully designed calorimetric setup. Experimental results from several types of MLCCs are presented over a wide range of operating conditions. Finally, a linear model is presented to accurately estimate MLCC losses.

Steady-State Analysis of Series-Capacitor Buck Converters in Discontinuous Capacitor Voltage Mode

“…The extent of imbalance and the critical values of flying capacitance below which imbalance occurs are important in the design of a compact a reliable converter, particularly if flying capacitors are implemented with technologies that exhibit degradation over time, such as class II multi-layer ceramic chip capacitors [16], [17]. In this section, analytic expressions for the critical capacitances are derived, along with the resulting steady-state solution in this regime of operation.…”