A Comprehensive Sensitivity Evaluation of a GaN Based Class ᶲ2 Inverter at Very High Frequency (VHF)

This paper evaluates the sensitivity of a class ᶲ2 inverter to component tolerances and PCB parasitic elements when switching at very high frequency (VHF: 30MHz-300MHz). The class ᶲ2 is a single transistor resonant inverter topology with low transistor voltage stress and fast transient response. Previous work has demonstrated its virtues at VHF and its use in different applications such as wireless power transfer or plasma etching. When switching at very high frequency, a small variation of component values in their tolerance range may have a significant impact on the class ᶲ2 inverter behavior. Additionally, at VHF, passive component values become of the same order of magnitude as PCB parasitic elements. In order to assess the sensitivity to component variations and PCB parasitic elements, a 30MHz 30W class ᶲ2 inverter using GS61004B from GaN Systems is designed and simulated with LTSpice. A prototype is then built in order to validate the simulation model. Once the LTSpice model verified, a Worst Case analysis is performed with component tolerances of 5%, 10% and 20% and the class ᶲ2 inverter behavior is recorded. Critical PCB parasitic elements are then identified, and their maximum acceptable value is determined using the Worst Case analysis.