T24.2 - A 1kW, 6.78MHz GaN Series-Series WPT Using 3D Packaging for Low Parasitic and Thermal Integration Achieving 2kW/in³

Wireless power transfer at multi-MHz frequencies is of growing interest for applications such as automated guided vehicles (AGVs), where compact size, high efficiency, and reliable operation are critical. This work presents the design and experimental validation of a compact 6.78 MHz, 1 kW wireless power transfer system operating without active cooling. A Class-D GaN inverter and decoupling network are integrated using a 3D packaging approach that reduces power-loop parasitics while providing broadband decoupling. Aluminum screw terminals serve as both low-impedance HV interconnects and heat spreaders for the power stage. A series–series resonant topology is used that reduces passive component count, whereas the gate driver is powered directly from the DC bus. The prototype demonstrates stable operation over a wide power range of 58 W upto 1045 W with end-to-end peak efficiency of above 90%, indicating a compact and scalable solution for wireless charging of mobile platforms.