Theoretical and numerical design of a wireless power transmission link with GaN-based transmitter and adaptive receiver

In this paper, we describe a rigorous theoretical approach to the circuit-level nonlinear design of an entire inductive resonant wireless power transfer (IR-WPT) system, including the transmitter and receiver nonlinear subsystems. Starting from a novel analytical characterization of the inductive resonant link, the system efficiency is parametrically computed as a function of a set of circuital parameters, including the power levels to be transferred. These quantities are then used as design goals inside the nonlinear optimization of the transmitter and receiver blocks. By adopting the last generation miniaturized enhanced-mode AlGaN/GaN-power field-effect transistor and fast Schottky diodes, a Class-D amplifier and a full-bridge rectifier followed by a switching dc-dc Buck converter that acts as load impedance transformer are designed in a single optimization process at 6.78 MHz. Thus, the transmitter and the receiver are directly connected by the IR two-port network, and the system is capable to adapt to variable distances between the resonators of the IR-WPT link. The choice of the Class-D topology for the transmitter and the adaptability of the active receiver enable to get rid of inter-stage matching networks, which can severely reduce the overall efficiency, especially in high power transfer environments. With the proposed IR-WPT system, up to 44 W of transferred power and a peak of 73% dc-to-dc efficiency were obtained with an input dc voltage of 30 V at a link distance of 5 cm. Numerical and experimental results are discussed, demonstrating the accuracy of the proposed design procedure.