A Synchronous Piezoelectric–Electromagnetic Hybrid Energy Harvesting Platform With Coil-Sharing Scheme

Abstract

Vibration energy harvesting is a promising power solution for autonomous wireless sensor nodes, particularly in volume-constrained Internet-of-Things (IoT) applications. Piezoelectric (PE) and electromagnetic (EM) transducers are widely used to convert vibration energy into electrical power. While hybrid PE–EM harvesters can deliver higher output power to support self-sustained systems, existing implementations invariably rely on at least one off-chip inductor for either PE bias-flip or dc–dc conversion, substantially increasing system volume. This article presents an inductor-less, capacitor-less PE–EM hybrid energy harvesting platform that eliminates this limitation. By leveraging the inherent phase synchronization between PE and EM sources, the proposed coil-sharing technique enables both bias-flip and dc–dc conversion without additional passive components, enabling the first fully integrated hybrid energy harvesting system. Fabricated in 0.18- $\mu $ m CMOS technology, the prototype delivers dual-regulated outputs at 1.8 and 5 V for multi-domain sensor nodes, achieving a maximum output power of 2.72 mW and a peak end-to-end (E2E) efficiency of 90%. These results highlight the platform’s potential for ultra-compact, high-performance energy harvesting in next-generation IoT applications.