A Resonant DC-Link Converter with Wide-Range Soft-Switching and Enhanced Voltage Utilization for Wireless Power Transfer Applications

To address the urgent demands for high efficiency and a wide voltage operating range in wireless power transfer (WPT) systems for electric vehicles (EVs), this paper proposes a topology based on a resonant DC-link. Retaining the functions of single-stage power factor correction (PFC) and voltage boosting, this topology achieves soft-switching operation over a wide load range and effectively elevates the steady-state level of the DC bus voltage, thereby significantly improving the voltage utilization ratio and output capability of the inverter. Theoretical analysis demonstrates that the proposed scheme can maintain zero voltage switching (ZVS) conditions for main switches across wide input voltage and load ranges, reduce switching losses and electromagnetic interference (EMI), and simultaneously boost the DC voltage via the resonant peak to enhance the power transfer adaptability of the system. The effectiveness of the proposed topology is validated by a 3.3-kW WPT experimental prototype with a 15cm air gap, and experimental results show that the system attains a peak efficiency of 94.2% over the full load range. Compared with the scheme employing the Z-source resonant converter, the proposed topology exhibits remarkable advantages in soft-switching range, voltage boosting capability and efficiency, and thus provides a high-performance circuit and control solution for high-frequency and high-power WPT systems.