A Bidirectional Autonomous High-Frequency Wireless Power Transfer System With Constant Voltage Output Against Load and Coupling Variations

This article proposes a high-frequency bidirectional wireless power transfer (BD-WPT) system that achieves soft-switching, synchronous rectification, and a constant voltage (CV) output over a wide range of operating conditions. The system employs autonomous current-fed push–pull converters as the inverter on the transmitter (Tx) side and the rectifier on the receiver (Rx) side. Tx and Rx circuits are configured symmetrically across the magnetic couplers, enabling a reversible power flow by changing the dc source and load so that the system can facilitate a bidirectional power transfer. Theoretical analysis demonstrates that the proposed resonant system can achieve a unity voltage gain and deliver a constant output voltage, even when the load, coupling, and coil inductance vary simultaneously. The inverter gate-drive circuits are designed to enable dynamic zero-voltage soft-switching at high frequencies. Circuit simulations and experimental results show that the system can maintain soft-switching while providing a stable output voltage close to the input of 20 V, with load, coupling, and Tx-Rx coil inductance ranges between $40 \Omega $ –2 $\text{k}\Omega $ , 0.4–0.8, and 1.4– $1.8 \mu \text{H}$ , respectively.