Wireless Power Transfer for Battery Powering System

The LCL topology (formed by an LC tank with a transmitting coil) is extensively utilized in wireless power transfer (WPT) systems with the features of a constant resonant current and ability to disconnect load abruptly. However, it requires high input voltage, which limits its utilization in battery powering scenarios (12~24 V). A current-fed inverter (CFI) is applied to the LCL-S (a compensation capacitor in series with the receiving coil) WPT systems to boost the input voltage, thereby getting a higher resonant current in the transmitting side (Tx). To facilitate the voltage regulation in the receiving side (Rx), a semi-active bridge (SAB) is introduced into the system, which further boosts the output voltage by a lower frequency switching at different duty ratios. Rigorous mathematical analysis of the proposed system is carried out and design guidelines are subsequently derived. Moreover, a power loss reduction is realized by zero voltage switch (ZVS) of the four switches in the Tx which are deduced and presented. Simulations and experiments are added to verify the proposed system. Consequently, a 93.3% system efficiency (DC-to-DC efficiency) is obtained using the proposed topology. Optimization techniques for a higher efficiency are included in this study.