Synchronized Switch Magnetic Harvesting: A nonlinear interface for power transfer and energy harvesting

With the spread of wireless autonomous devices, for instance in the framework of the Internet of Things (IoT), ensuring reliable power supply for the good operations of these systems has become a particular issue to tackle. In that view, providing such energy wirelessly or using ambient energy sources through energy harvesting is an attractive option to ensure the long-term operations of autonomous sensors and sensor networks without jeopardizing their flexibility. To this end, electromagnetic medium is a premium choice, due to the good power densities that can be reached at the centimeter scale. Yet, electromagnetic energy harvesting and medium-range electromagnetic Wireless Power Transfer feature relatively low coupling and raise interfacing issues due to the low voltage output of the receiving coil. To address these two issues, this paper introduces a nonlinear switching principle for significantly enhancing the extracted power/energy from the transducer while boosting the output voltage magnitude. The proposed scheme, inspired by piezoelectric energy harvesting, consists in briefly inverting the current of the electromagnetic transducer, leading both to a current magnification and phase shift yielding a significant improvement in the energy conversion capabilities. While nonlinear switching schemes have already been proposed in the literature, the approach exposed in this study allows undertaking the issue of ensuring current inversion through the use of a proper rectification scheme, significantly boosting the power, while enhancing the voltage output magnitude for limiting losses in the electric interface. With both of these advantages combined, it is shown that the proposed scheme permits a significant power gain compared to the standard approach.