Optimized Parameters Design and Adaptive Duty-Cycle Adjustment for Class E DC-DC Converter With ON-OFF Control

The Class E dc-dc converter, with a simple topology and zero-voltage-switching (ZVS) for the power switch, can operate at a switching frequency of up to megahertz. In this paper, an optimized ZVS operation condition for minimizing the switch voltage stress, switch rms current, and switch voltage harmonic components is derived for the ON-OFF controlled Class E dc-dc converter by optimizing the time instant at which the switch voltage resonates back to zero. Based on this result, a step-by-step parameter design approach is proposed for a Class E dc-dc converter with a large input inductor, which avoids time-consuming simulations or complex numerical calculations. Then, a capacitance compensation approach is further proposed to extend the design results to a Class E dc-dc converter with a resonant input inductor. Furthermore, an adaptive duty-cycle adjustment scheme is proposed for reducing the reverse conduction loss of the power switch, thereby improving the conversion efficiency over the entire input voltage range. Finally, a prototype of a 20-MHz 10-W Class E dc-dc converter is built and tested in the laboratory, and experimental results are presented to verify the effectiveness of the proposed optimized parameter design approach and the adaptive duty-cycle adjustment scheme.