This study presents a symbolic method for the design of filter capacitors in DC–DC switching converters, using a combination of a ceramic and an electrolytic capacitor. Assuming that the overall capacitor is subject to a square wave-like current, and modelling each of the two parallel capacitors as the series of a capacitance C and a resistance R, analytical formulas are derived to express the ripple voltage on the capacitors and each of the two rms currents as a function of the capacitor parameters. For each fixed ceramic capacitor, an acceptability region for the electrolytic one can be drawn in the C–R electrolytic plane to represent the available set of capacitors, separating those feasible (complying with the design constraints, such as those on the ripple and rated voltage and on the rms currents) from the unfeasible ones. Four heuristic ranking functions are then used in a procedure aimed at selecting the optimal electrolytic/ceramic combinations among those feasible. PowerSim PSIM simulations validate the method and show its effectiveness for the design of mixed electrolytic/ceramic capacitor-based passive filters.
Designing a Mixed Electrolytic/Ceramic Filter Capacitor in DC-DC Converters
DE NARDO, ANTONIETTA;FEMIA, Nicola;ZAMBONI, Walter
2012
Abstract
This study presents a symbolic method for the design of filter capacitors in DC–DC switching converters, using a combination of a ceramic and an electrolytic capacitor. Assuming that the overall capacitor is subject to a square wave-like current, and modelling each of the two parallel capacitors as the series of a capacitance C and a resistance R, analytical formulas are derived to express the ripple voltage on the capacitors and each of the two rms currents as a function of the capacitor parameters. For each fixed ceramic capacitor, an acceptability region for the electrolytic one can be drawn in the C–R electrolytic plane to represent the available set of capacitors, separating those feasible (complying with the design constraints, such as those on the ripple and rated voltage and on the rms currents) from the unfeasible ones. Four heuristic ranking functions are then used in a procedure aimed at selecting the optimal electrolytic/ceramic combinations among those feasible. PowerSim PSIM simulations validate the method and show its effectiveness for the design of mixed electrolytic/ceramic capacitor-based passive filters.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
