A Load-Independent Choke-Less Class-E Power Amplifier for 6.78-MHz Wireless Power Transfer

Class E power amplifier (PA) is a single-switch inverter widely used in high-frequency applications. In the Class E PA topology, a large enough choke inductor is required to maintain a constant input current. This bulky choke inductor reduces the PA's energy density and introduces extra losses. To eliminate the influence of this choke inductor and make the system more compact, a load-independent choke-less power amplifier topology for wireless power transfer (WPT) application is proposed. The waveform characteristics are derived analytically. A load-independent design method is introduced to guarantee the high efficiency of the inverter under any loading condition. A WPT system is implemented to verify the load-independent design concept.