A Wireless Power Transfer System with Robust Primary-Sided Current Based on the Self-Excited Inverter

In this paper, a self-excited inverter is utilized to construct the inversion stage of the wireless power transfer (WPT) system without the PWM generator and digital signal processor, which could dramatically simplify the hardware structure. Meantime, soft-switching and automatic frequency tracking could be achieved without additional strategies which also decrease the complexity in control. Generally, in a WPT system, the current of primary-sided coils is expected to be kept constant despite the variation of load, which is helpful to achieve the constant voltage (CV) or constant current (CC) output of the WPT system. Accordingly, the parallel-series (PS) resonance topology is utilized to achieve the high robustness of the primary-sided current without additional compensation networks. The analysis and design procedure for the WPT system are provided and a low-power prototype is built. The simulation and experimental results validate the design of the WPT system. When the load resistor changes from 30Ω to 10 Ω, the fluctuation of primary-sided current is only 4.3%, and a dc–dc transfer efficiency of 85.82% with a 9-cm distance and 73.16-W output power is reached.