A Mathematical Model for Self-Priming Circuits: Getting the Most From a Dielectric Elastomer Generator

A dielectric elastomer generator (DEG) can be used for converting mechanical energy from natural motion sources, such as walking, waves, trees, etc., into electrical energy. A DEG is comprised of a soft and flexible dielectric elastomer (DE) capacitor, a priming circuit (PC), which transfers high potential charge onto/off the DE electrodes, and a power extraction circuit that harvests the generated power. To generate power, the PC must charge and discharge the DE in synchronization with the DE's capacitance change. A simple circuit to do this exists: the self-priming circuit (SPC). The SPC consists of diodes and capacitors that passively switch between charge delivery and charge receiving states in synchronization with the DE's capacitance change. Until now, there has been no understanding of how to design an SPC in order to maximize harvested energy from the DE. A new mathematical model for an SPC is presented, leading to design and optimization. An accuracy of 0.1% between model, simulation, and experiment over five cycles is obtained, once losses are taken into consideration. The behavior of the SPC is shown to be related to the maximum and minimum capacitances of the DE, but is unaffected by the exact shape of the capacitance waveform.