Modeling and analysis of class-E zero-voltage switching amplifier at any grading coefficient and duty ratio

Abstract

This paper introduces the class-E power amplifier with only the MOSFET nonlinear drain-to-source parasitic capacitance as a shunt capacitance for the class-E sub-nominal condition, i.e., zero-voltage-switching (ZVS) condition at any grading coefficient m of the MOSFET body junction diode and any duty ratio D. The obtained analytical expressions for waveforms and design equations show that the grading coefficient m and the duty ratio D can be used as the adjustment parameters, which increases the degree of the design freedom by two. The switch-voltage waveform does not satisfy the class-E switching condition when the grading coefficient m is different from the design specifications, which resulted in the power conversion efficiency degradation. On the other hand, the duty ratio D is determines the location of the class-E switching conditions. Therefore, the grading coefficient m and the duty ratio D are important parameters to satisfy the class-E sub-nominal condition. Although, the maximum operating frequency and the output power capability are affected by the duty ratio D, only the maximum operating frequency is affected by the grading coefficient m. We obtained the analytical expressions, which are validated by PSpice simulations and laboratory experiments that the grading coefficient m is considered. The measurement and PSpice simulation results agreed with the analytical expressions quantitatively, which show the validity of our analytical expressions.