A Flat-Top Single-Ended Resonant Converter With Low Switch Voltage Stress

This article proposes a flat-top single-ended resonant converter (SERC) for wireless charger with the merit of low switch voltage stress, by introducing a parallel LC network in series with the primary switch. A characteristics analysis of the proposed SERC is performed in time domain, obtaining the zero-voltage-switching condition, power transfer capacity expression, and the time requirement to achieve an ideal voltage cancelling. Due to the injected third harmonic, the voltage waveform of the switch can be shaped into a near trapezoid or a saddle shape. From the perspective of waveform superposition, we derive the conditions for the minimum switch voltage stress and the flat-top waveform of switch voltage. Finally, a 1900-W prototype is built to verify the theoretical analysis. The experimental results show that the proposed converter achieved a flat-top switch voltage waveform and the voltage stress of 2.12 times the input voltage at full load, compared to that of 2.65 times the input voltage for the conventional one. Besides, the maximum efficiency is also increased to 93.33% from 92.32%.