Design of Class-E<sup>2</sup> Wireless Power Transfer System Considering Parasitic Capacitances of Switching Devices and Coupling Coils

In this paper, we present an accurate design approach for a class-E2 wireless power transfer (WPT) system to enhance efficiency. The design takes into account the effects of nonlinear parasitic capacitances in switching devices, linear parasitic capacitances of coupling coils, and the forward drop voltage of the diode on the system's performance. To address the discontinuities in the measured data of nonlinear parasitic capacitances in switching devices, spline interpolation is used. A design example is also given along with its simulation and experimental results. All the switch-voltage waveforms meet the class-E zero-voltage-switching/zero-derivative-switching (ZVS/ZDS) conditions. Moreover, the simulated and experimental results closely match the numerical predictions, confirming the validity of the proposed design given in this paper.