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 k Omega, 0.4-0.8, and 1.4- mu H , respectively.