An Efficient and Compact Supply for Electroactive Polymers

New trends in electroactive-polymers (EAP) based devices for soft actuators and for electrocaloric cooling revive studies on compact, efficient, reversible and low power supply. High electrode resistance, high voltage and small capacitance of EAPs represent a major hindrance for an efficient charge/discharge. Because Joule losses in EAP are entwined with the voltage profile of the converter, we study an inductor based coupling, focusing on a multistep voltage profile produced by a Solid-State Marx Modulator. The energy stored in the inductor, its volume, and the efficiency of the charge/discharge process are studied as a function of the number of steps and of the RLC damping factor. Furthermore, to avoid detrimental current surge related to resonance, a pre and post charge protocol are implemented. The tradeoff between inductor size, efficiency and the number of steps is discussed using an analytical model, and through comparison with measurements performed using a specifically developed Solid-State Marx Modulator. This study shows that the multistep charge of EAPs represents an efficient tool for tackling the Joule losses vs. volume reduction issue offering a key tool to guide the design of the new generation of EAP based devices.