Analysis and Design of an Isolated Current Source Class-E Inverter With Significant Harmonics

This article presents an isolated current source class-E inverter topology with load-independent zero-voltage switching. If harmonics were neglected (thanks to high quality factor), the current source behavior would be maintained at any load as reported in the literature. When harmonics are significant, the load current starts to vary with the load. This article aims to predict the load range with a soft current source defined by a small load current variation (5% in the example), considering the impact of harmonics. To obtain the accurate load current variation with the load resistance, the time-invariant multifrequency modeling (TIMF) method is utilized to solve the steady-state solution without numerical iteration. The switch and its paralleled shunt capacitor are modeled as a single component to treat the discontinuous state of the capacitor. The modified TIMF modeling provides a direct solution of the RMS load current and resonant capacitor's voltage stress, enabling general guidance of the coupled inductors design considering the tradeoff between load range and voltage stress. Three 10 V input, 0.6 Arms output, and 16.4 W maximum power prototypes were built with different load ranges. A maximum 47:1/30:1 load range for 10%/5% output current variation was achieved.