Increased Piezoelectric Coupling Force in Autoparametric Excitation Harvester connecting to Self-powered Series and Parallel Synchronized Switch Harvesting on Inductor (SSHI) Interfaces

We experimentally investigate the relationship between the electromechanical coupling states, and the optimal resistive load, output power, and harvester's displacement in the high output autoparametric excitation harvester connecting to the self-powered series and parallel synchronized switch harvesting on inductor (SSHI) interfaces. The piezoelectric coupling force increases as the acceleration and the resistive load increases, because the electromechanical coupling states enhances, as well as the piezoelectric voltage increases by the SSHI technique. The increased piezoelectric coupling force suppresses the harvester's displacement, which leads to the shift in the optimal resistive load and the decrease in the output power. In our autoparametric excitation harvester, the parallel SSHI interface can achieve high output power at low acceleration, while the series SSHI can achieve high output power at high acceleration. The maximum output power of 3.1 mW was obtained at acceleration of 2.4 m/s(2) (0.24G) by the series SSHI interface, from the overall harvester's size 56x56x70 mm(3).