This paper presents a unified and systematic design approach for class-EF2wireless power transfer (WPT) systems capable of operating at high frequencies with power transmission efficiency. The proposed approach models the class-EF2inverter, class-EF2rectifier, and inductive coupling network as a single integrated system. An analytical framework is developed to capture the interdependencies among circuit elements and enable deterministic design values without empirical tuning. To validate the approach, a 6.78 MHz class-EF2WPT prototype is designed, simulated, and experimentally implemented. The simulated and measured waveforms show good agreement with analytical predictions, including the realization of the class-E Zero-Voltage-Switching / Zero-Derivative-Switching (ZVS/ZDS) conditions. A power transmission efficiency of 84.3% is achieved without any tuning, demonstrating the practicality and robustness of the proposed approach. The proposed approach enables efficient and predictable system design, advancing the feasibility of next-generation wireless energy link.

In Dynamic Wireless Power Transfer, it is essential to detect the vehicle, control the switching of the transmission coil, and transmit high power during low coupling to the vehicle. This is because standby loss occurs when power is applied to the transmission coil when the vehicle is not present. Therefore, this paper proposes a method to reduce standby losses and to send high power to the vehicle by using SP-PS circuit and capacitor switching. Consequently, vehicle detection was achieved without additional sensors, standby power loss was reduced by approximately 50% compared to the Double-LCC method, and sufficient receiving power was obtained—although it decreased by about 10% compared to the S-S method in simulations.

This paper presents an enhanced parasitic component model for spiral air-core inductors in MHz load-independent single-input multiple-output (SIMO) wireless power transfer (WPT) systems. The model improves upon previous designs by incorporating inductance, parasitic capacitance, and both parallel and series parasitic resistances, accounting for dielectric and copper losses. A prototype system featuring a load-independent class-EF inverter and multiple class-D rectifiers is developed to validate the model, demonstrating strong agreement between theoretical predictions and experimental results. The model ensures Zero-Voltage-Switching (ZVS) at the transmitter and constant output voltages at all receivers, offering a reliable framework for high-precision, high-frequency load-independent SIMO WPT system design.

This paper presents an easy-to-use analytical design approach of the load-independent class-E inverter at any duty ratio. By using the analytical approach, it is possible to maintain the amplitude of the output voltage and the operation of the zero-voltage switching. Additionally, a design example is given along with its LTspice simulation and laboratory experiment. The LTspice simulation and laboratory experiment waveforms are in good agreement with the analytical ones even load variations. Moreover, all the switch-voltage waveforms satisfy the ZVS condition. These results showed that the proposed approach and analytical expressions are available and effective.