Comparative Analysis of Class-E and Class-Φ₂ Inverters for 13.56 MHZ Wireless Power Transfer Systems

This paper compares the efficiency of wireless power transfer (WPT) [1] systems based on class-E [2] and class$\Phi_{2}$ inverters [3]. Both systems aim to achieve high power and efficiency in a compact form by employing resonant inductive coupling and integrating GaN switches, which perform well at the very high frequency (VHF) of 13.56 MHz. Although the class- $\Phi_{2}$ inverter demonstrates slightly lower efficiency for simulation results, it compensates with reduced switch stress, making it more advantageous when it comes to handling increased input voltage and power. Experimental results from fabricated prototypes confirm these findings, reinforcing the initial conclusions drawn from simulations.