Comparative Analysis of Class-D, Class-E ,and Class EF Inverter Topologies for Multi-Megahertz

This paper presents a comparative analysis between Class-D, Class-E and Class-EF power amplifiers for inductive Power Transfer (IPT) systems that operate at multimegahertz frequencies such as 6. 78MHz and 13. 56MHz. The design guidelines of all topologies along with components selection are presented. An open-loop system for each topology is built in LT-Spice simulator for verification and all classes are designed to feed a constant power load of 30W. Input DC voltage, total voltage stress and total current stress of all utilized switching devices, and efficiency are measured in the comparison between all topologies. Also, the soft switching operation for all topologies is obtained and validated for fair comparison to work effectively in the mentioned high frequency. The main feature of Class D is the simplicity of the passive elements design and operation. However, it has additional switch compared to class E. In contrast, Class E has higher efficiency between all counterparts with using one switching device but needs carful design criterion to solve dependent load issue. Finally, Class EF PA has a complex design process and has many component counts.