High frequency full-bridge Class-D inverter using eGaN® FET with dynamic dead-time control

Wireless Power Transmission Systems (WPTSs) that use capacitive or inductive coupled resonators need to be designed at MHz frequencies to avoid large passive components. The advent of high-frequency high-power enhancement-mode Gallium Nitride (eGaN) FETs has made the idea of MHz switch-mode power inverters with higher efficiency compared to linear power amplifiers more realizable. One of the major challenges of this type of inverter is how to maintain soft switching through Zero Voltage Switching (ZVS) over a full range of output power control. This paper presents a ZVS Class-D full-bridge inverter designed at 13.56 MHz with dynamic dead-time control to maintain smooth transition while linearly controlling the output power. Simulation results and ZVS analysis presented show that dynamically changing the dead-time during input voltage control can prevent large current spikes and associated high switching loss on the switches.