Steady-State Analysis of Isolated Class-E$^2$ Converter Outside Nominal Operation

This paper presents a steady-state analysis of the isolated class-E
²
converter outside nominal operation. By transforming the isolated class-E
²
converter into the typical topology of the class-E inverter, the switching patterns can be comprehended on the parameter spaces easily. The output power and the power-conversion efficiency can be expressed as functions of circuit parameters such as coupling coefficient of the transformer, load resistance, and operating frequency. The class-E
²
wireless power transfer (WPT) system was designed and implemented in this paper for verifying the analytical expressions. The analytical predictions of system performance against coupling-coefficient and load-resistance variations agreed with PSpice simulation and experimental results quantitatively, which showed the validity of the analytical expressions. Comparisons between the class-E
²
and classD-E WPT systems are shown along with their discussions. Additionally, two application examples of the analytical expressions are introduced in this paper, which shows the usefulness of the analytical equations.