Autonomous Polyphase Current-Fed Push-Pull Resonant Converter Based on Ring Coupled Oscillators

This paper presents an autonomous polyphase current-fed push-pull resonant converter without the need of monitoring and controlling its phase delays. Although the method is valid for multiple phases, a three-phase system is studied to show that accurate 120° phase shift can be realized by coupling three identical magnetic coils of a resonant converter with zero voltage switching (ZVS). Unlike the conventional converters, the proposed converter achieves a full-autonomous operation with automatic startup, full resonance at ZVS, and accurate dynamic balancing between the phases without any additional detection and control. A prototype of a three-phase system operating at 73.5 KHz has been built, and both simulation and practical results have demonstrated that the proposed converter can generate good quality sinusoidal waveforms with ZVS operation and precise phase delays. The proposed converter can be used for polyphase inductive power transfer systems where a generation of a rotating/travelling magnetic field is required.