Design, analysis and implementation of class-E ZCS/ZCDS power amplifier for any duty ratio with nonlinear output parasitic capacitance

This paper gives the design and analysis approaches for the class-E power amplifier with a shunt inductor under the nominal conditions, i.e., zero-current switching (ZCS) and zero-current derivative switching (ZCDS), with taking into account the MOSFET nonlinear output parasitic capacitance at any duty ratio. Although, the class-E ZCS/ZCDS conditions obtained high-efficiency, but the switch-current waveform affected by the slope of the voltage across the MOSFET nonlinear drain-to-source parasitic capacitance during the switch-off state, which restricted the operating frequency. On the other hand, the duty ratio is an adjustment parameter to obtain high-frequency operation. Therefore, the duty ratio and the MOSFET nonlinear output parasitic capacitance are required to satisfy the class-E ZCS/ZCDS conditions. The verification of the proposed analysis expressions is performed by fabricating of the class-E power amplifier with the output power 13.2-W at the operating frequency 4-MHz, and the laboratory experiments are performed, which achieved 90.9 % power conversion efficiency. The validity of proposed analytical expressions had been proved by the achieved good agreement between waveforms obtained from the PSpice-simulations and circuit laboratory experiments, which satisfied both ZCS and ZCDS conditions.