High gain, load-tolerant self-powered series-parallel Synchronized Switching technique for piezoelectric energy harvesting

In the framework of autonomous wireless devices ( e.g. , sensors) powered by energy available from their surrounding environment, this article exposes a technique combining the so-called series and parallel Synchronized Switch Harvesting on Inductor (SSHI) approaches for piezoelectric energy harvesting. More specifically, the proposed circuit consists in switching the piezoelectric element on two inductors, one in series between the piezoelement and the energy extraction stage (rectifier bridge) and the other one in parallel with the rectifier. This, therefore, allows several energy transfer processes to occur per half period, even when the switching process is finished. Based on numerical analysis supported by experimental validations, it is shown that such a technique permits a significant widening of the effective load and rectified voltage ranges, but also, under particular conditions, a power output magnification that is even larger than in the sole SSHI case.