A high-frequency inverter architecture for providing variable compensation in wireless power transfer systems

This paper introduces a new high-frequency inverter architecture that can compensate for coupling variations in wireless power transfer (WPT) systems, while operating at a fixed frequency and maintaining high efficiency. This architecture, termed the variable compensation inverter (VCI), comprises multiple high-frequency inverters feeding a lossless resonant network, with the inputs of the inverters fed by controllable voltages. By appropriately controlling the input voltages of the individual inverters and their relative phase-shift, the VCI can maintain near-resistive, and slightly inductive, loading of the inverters even as the reactance of the WPT coupler changes; hence, providing compensation while maintaining zero-voltage and near-zero-current switching. The VCI also ensures that the output power of the WPT system is maintained at a fixed level even during coupling variations. A prototype VCI is designed, built and tested with a 1.5-MHz 65-W capacitive WPT system for laptop charging applications. The system is able to fully compensate for up to 50% lateral misalignments in the capacitive coupler while maintaining a fixed output power level of 65 W and achieving 82% efficiency.