High Efficiency Capacitive Piezoelectric Energy Harvesting Interfaces

Piezoelectric energy harvester (PEH) is one of the most promising candidate for ambient vibration energy scavenging for ubiquitous miniaturized Internet of Things (IoT) devices. Due to the PEH inherent capacitance, the extractable AC-DC electrical power in traditional PEH interface using full-bridge rectifier (FBR) is limited. Existing PEH interfaces generally employ non-linear techniques such as the parallel-synchronized-switch harvesting-on-inductor (P-SSHI) and fractional open circuit technique to enhance the extracted power and achieve efficient maximum power point tracking (MPPT). However, they typically require bulky external high-Q inductors to extend the damping duration while inducing excessive device voltage stress during MPPT. This seminar will focus on the development of recent inductor-less PEH interfaces exploiting only capacitors for flipping the PEH voltage for energy extraction improvement. It will first cover the basic operations of capacitive PEH interfaces and provide the fundamental analysis on its performance limits. The design tradeoffs between the achievable extracted 2019-2021 CASS Distinguished Lecturer Roster energy and the different loss mechanisms will be outlined. System level implementation of maximum power point tracking (MPPT) and output voltage regulation will also be discussed.