Low-voltage broadband piezoelectric vibration energy harvesting enabled by a highly-coupled harvester and tunable PSSHI circuit

This paper presents a system-level design approach for widening the bandwidth and lowering the operating voltage of a piezoelectric vibration energy harvesting system (PVEHS). The proposed strategy involves co-optimization of the two constituent parts: (1) a highly-coupled piezoelectric vibration energy harvesting device (PVEHD) and (2) a phase-shift tunable parallel-SSHI (PS-PSSHI) interface power-electronic circuit. First, we analyze the interaction between them to achieve an overall reduction of system voltage and to widen bandwidth. Next, a co-designed system is experimentally demonstrated to validate the analysis. The implemented PVEHS consists of (i) a customized PVEHD designed for high electromechanical coupling and well-separated short-circuit (f (SC)) and open-circuit (f (OC)) resonances, and (ii) a tunable PS-PSSHI circuit which has an active rectification with low voltage drop to increase system efficiency. The system achieves an output power of 148 mu W with a bandwidth of 81 Hz, an increase of 337% compared to conventional full-bridge rectifier. In addition, the system rectification voltage is lowered by 30% which makes it viable to power low-voltage Internet-of-Things sensor nodes.