An Inductor-Less Capacitor-Less Synchronous Piezoelectric-Electromagnetic Hybrid Energy Harvesting Platform with Coil-Sharing Scheme

Abstract

Along with the rise of the Internet of Things (IoT) and edge artificial intelligence (AI), energy harvesting provides a promising sustainable power solution for these edge devices. Piezoelectric (PE) and electromagnetic (EM) transducers are two major ways to harvest ambient vibration energy [1-6]. For PE harvesters, various active rectifiers [7-14] were proposed to improve energy extraction, such as synchronous switch harvesting on inductor (SSHI) rectifiers. However, using high-quality off-chip inductors increases system volumes and costs, while using on-chip (or off-chip) switched capacitors increases chip areas (or system sizes) in addition to a relatively lower overall efficiency. For an EM harvester [15,16], it can be rectified by a boost converter [16] by reusing the EM coil as the inductor. However, off-chip inductors are still required for power conditioning in other DC-DC and regulation stages. Prior works combined these two transducers to harvest more energy from one kinetic source [17]. Unfortunately, all prior structures require additional off-chip inductors or capacitors for different stages, from the rectification to output regulation, as shown in Fig. 31.1.1. It is interesting to think that if the inherent coil of EM harvester can be used for its own boost conversion, why it cannot be used in all other blocks of the whole system, such as PE energy rectification, DC-DC conversion, and output regulations, to eliminate the need for any power components.