Intracycle Gapless Core Desaturation via Crisscross Switches for Maximal Magnetic Energy Harvesting

Current-transformer-based (CT-based) magnetic energy harvesting (EH) extracts energy from ac current-induced magnetic fields, outperforming other ambient EH methods in harvested energy level and predictability. As a result, it emerges as a suitable power supply for self-powering low-power devices like embedded systems, sensor nodes, Internet-of-Things (IoT), and cyber-physical systems (CPS). Prior studies indicated that optimal EH occurs when the magnetic core operates in a suitably saturated state as the magnetically stored energy in a physical core volume increases as the core approaches saturation. However, the actual power transfer electrically ceases once the core reaches full saturation and no current circulates through loads. This article introduces an innovative desaturation strategy, using four bidirectional switches in a crisscross pattern to alter the core voltage direction and prevent magnetic saturation, to enhance EH level. This study also examines the impact of various factors such as load voltage, the count of EH windows, and primary current on the harvested energy, aiming to find the optimal load voltage for maximum energy. Through circuit simulations and experiments, the proposed method shows the harvested energy is significantly increased, exceeding six times the output of basic systems relying on passive rectifiers. Moreover, our new method demonstrates distinctive EH traits, wherein energy extraction quadratically increases with the primary current, unlike conventional methods where energy extraction scales linearly with the primary current. This advantage allows a significantly denser energy harvester to be built under higher magnetic field configurations.