6.78 MHz Compact Wireless Power Transfer System with Voltage Conversion from 400 V to 48 V and Integrated PCB Coils

This paper presents the design and measurement results of a wireless power transfer (WPT) system for industrial applications. The system operates at a high switching frequency of 6.78 MHz, enabling compact coil integration into a printed circuit board (PCB). The resonant circuit is based on the LLC topology, which utilizes the mutual and stray inductances of the transmitter and receiver coils. The system achieves a power transfer of up to 450 W while reducing the input voltage from 400 V to a practical on-board voltage of 48 V. The peak efficiency is 90% at 350 W. Full zero voltage switching (ZVS) is achieved, reducing switching losses and allowing passive cooling. The innovative design combines functionality with space efficiency, making it suitable for various industrial applications.