Inductive Wireless Power Transfer at 100MHz with Wide Load Range and Constant Output Current

Power conversion at 100MHz is important to miniaturization and integration, which is critical in wireless power transfer (WPT) for Peer-to-Peer (P2P) charging in consumer electronics and Internet of Things (IoT). Design and implementation at this frequency is challenging in selecting active devices, passive components, gate drivers, and circuit topologies along with compensation networks, which are crucial for WPT systems capable of a wide load range.This paper articulates the design of a 100MHz inductive wireless power transfer system using current-mode class D converters both for the transmitter and receiver. An equivalent model for the symmetric CMCD WPT system is derived and used to show purely resistive input impedance, wide load range, and constant output current with the tuned compensation networks obtained from the previously published current-controlled-voltage-source (CCVS) model. Uniqueness of solution and sensitivity to parameters is analyzed for the compensation networks, which provides a guide for hardware designers. Finally, a prototype of a 100MHz symmetric CMCD WPT system is built and used to verify the characteristics with the designed compensation networks under different loading conditions and input voltages. A prototype of a symmetric CMCD WPT system was demonstrated to achieve 2.7W output power, nearly 70% end-to-end drain efficiency, and nearly 60% total efficiency when including gating loss.