A New Simplified Method and Design Guidelines for the Optimization of Push-Pull Class Φ ₂Converters for Wireless Power Transfer Applications

The complicated resonant operations of class Φ2 topology bring challenges for accurate design and performance optimization, hindering the full utilization potential of converters. Considering the narrow design freedom in traditional methods with almost fixed duty cycle D, this article widens the design options of push-pull class Φ2 converters through frequency-harmonic analysis. A full selection freedom of Din (0,0.5) is discussed analytically, providing ample space for optimization based on any required performance indices. From 1.98E5 analytical results, we found six numerical equations that fully decouple the interconnected relations between each circuit parameter and D. The proposed numerical method allows rapid circuit design and component selection with a high accuracy regardless of the system power or load voltage. Parasitic effects are discussed and incorporated into the design approach as correction steps. Finally, we introduce performance analysis based on an example wireless power transfer (WPT) system, providing in-depth studies on the optimization regarding efficiency, power output capability, and component selection. Experimental results validate the accuracy and efficiency of the proposed design method based on a 100-W WPT system at 6.78 MHz frequency. Both inverter and rectifier present load-independent soft-switching operations, with converter efficiency over 93%. The system provides 83% dc-dc efficiency at full load.