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 this paper, a WPT system that can switch between constant current (CC) and constant voltage (CV) in a single circuit is proposed. In the proposed WPT system, the CC and CV modes are achieved by varying the on-duty ratio of the buck converter. In addition, the proposed system also keeps the zero-voltage switching against coil misalignment and load variations without any information feedback from the rectifier to the inverter. This is because the load-independent behavior is built into the proposed system. The experimental results are consistent with the analytical predictions, which show the validity of the proposed circuit design strategy and the derived analytical expressions. Under rated conditions, the output power was 36.9 W and the power conversion efficiency was 86 % at the operating frequency of 6.78 MHz.

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 proposes the load-independent (LI) class-E frequency multiplier along with a unified circuit analysis method with the LI class-E amplifier. A circuit-parameter determination strategy is presented to achieve LI operation and maximum power output capability at the rated condition. We designed the class-E amplifier and frequency doubler using the unified analytical expressions. Both the implemented circuits achieved the LI operation, namely constant output voltage amplitude and zero-voltage switching against load variations without any control. The experimental results showed quantitative agreements with the analysis results, namely waveforms and power conversion efficiency, which indicates the validity of the derived analytical expressions and design procedure.

This paper proposes a load-independent high-frequency wireless power transfer (WPT) system for multiple receivers with a single transmitter. The proposed system achieves zero-voltage switching (ZVS) at the transmitter and constant output voltages at all the receivers against load variations without any control. Moreover, the proposed system keeps the load-independent operation even when the number of receivers changes. The circuit analysis for the proposed WPT system is given. Experimental verifications for the proposed WPT systems with two receivers were conducted, which showed the effectiveness. The implemented WPT system achieved a peak efficiency of 83.4% at 6.78 MHz and total output power of 50 W.

This paper presents a simulator-based design-optimization software for high-frequency power-electronics circuits, which consists of the heuristic algorithm, magnetic-component design tool, and commercial simulator, SPICE. Because we can use the SPICE component library, the software suggests high-accurate design results, and the experimental adjustments can be reduced. Besides, by using the heuristic algorithm, the optimization algorithm converges stably. The magnetic-component design tool provides a precise estimation of the power losses, which is important for high-frequency power-electronics circuit designs. As an example, we design the class-DE inverter by applying the developed software, which shows the usefulness of the software.

This study proposes a self-tuned series resonant power oscillator capable of load-independent operation. The proposed power oscillator has a self-tuning feedback loop that provides a gate-driving voltage with a constant phase shift and amplitude. Therefore, it is robust against component tolerances in a series resonant filter. It is also robust against load variations owing to its load-independent design. Consequently, it maintains a high-efficiency and constant AC output against load variations and component tolerances. Experimental results demonstrated the effectiveness of the proposed power oscillator.

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.

This paper presents a novel design procedure based on analysis for the class -Φ2 inverter at any duty ratio, taking into account the fundamental-frequency and harmonic components of the input current, output current, and injection current. By using the proposed design procedure, the design values for satisfying the class-E zero-voltage switching/zero-derivative switching (ZVS/ZDS) conditions of the class -Φ2 inverter can be achieved without applying any tuning process. A design example is given along with its LTspice simulation and laboratory experiment at 20.5 W output power and 6.78 MHz operating frequency. The analytical predictions agreed with experimental and LTspice-simulation results quantitatively, which showed the validity of analytical expressions given in this paper.

This paper presents a novel analysis procedure for the class E oscillator. A design example is given along with the LTspice-simulation and experimental waveforms. All the switch-voltage waveforms from the LTspice simulation and circuit experiment satisfy the class E zero-voltage switching (ZVS) and zero-voltage-derivative-switching (ZVDS) conditions. It is seen from the LTspise-simulation and experimental results that the analytical prediction agreed with the simulated and experimental ones quantitatively, which validated the accuracy and effectiveness of the proposed design procedure. The efficiency achieved 94.6 % at 7.8 W output power and 1 MHz operating frequency.

This paper presents a high-speed resonant driver for silicon carbide (SiC) MOSFET, which is based on the class-E inverter. Gate-to-source resistance and input capacitance of SiC MOSFET are included in the resonant circuit of the driver for avoiding the driving-signal strain. Additionally, clamp diodes are added to the output filter in the proposed driver, which makes a square-waveform-like driving signal. The design example along with experimental waveforms is shown in this paper. It was possible in the laboratory experiments to drive the SiC MOSFET at 7 MHz and 13 MHz frequencies with satisfying the zero-voltage switching condition, which showed validity and effectiveness of the proposed driver and its design procedure.

This paper presents a design procedure for wireless power transfer (WPT) systems based on the class-E2 dc-dc converter, taking into account inductive coupling-coil optimizations. The WPT system model is formulated as an equivalent circuit model by expressing the inductive coupled part as a transformer with low-coupling coefficient and equivalent resistances of primary and secondary coils. By using the circuit model, the dc-to-dc efficiency can be obtained analytically. The dc-to-dc efficiency, which is a cost function for optimization, is expressed as functions of physical parameters, such as coil size, wire type, and number of turns. The particle swarm optimization (PSO) is applied for reduction of the computational complexity compared with previous design method [1] and maximization of the cost function in this paper. Experimental results showed the validity and the usefulness of the proposed design procedure.

This paper presents a RIC-WPT system with class-E inverter and class-DE rectifier along with its analytical design procedure. By using the class-E inverter as a transmitter and the class-DE rectifier as a receiver, the designed WPT system can achieve a high power-delivery efficiency because of the class-E ZVS/ZDS conditions in both the inverter and the rectifier. In the experimental results, the system achieved 73.0 % overall efficiency at 9.87 W (50 Ω) output power, coil distance 10 cm, and 1 MHz operating frequency. The experimental results showed good agreement with the design specifications, which indicates the validity of the design procedure.

This paper presents a resonant inductive coupling wireless power transfer (RIC-WPT) system with a class-E2dc-dc converter along with its analytical design procedure. By using the class-E inverter as a transmitter and the class-E rectifier as a receiver, the designed WPT system can achieve a high power-conversion efficiency because of the class-E ZVS/ZDS conditions satisfied in both the inverter and the rectifier. In the simulation results, the system achieved 65.9 % overall efficiency at 5 W (50 Ω) output power, coil distance 30 cm, and 5 MHz operating frequency. Additionally, the simulation results showed good agreement with the design specifications, which indicates the validity of the design procedure.

This paper proposes an inductive coupled wireless power transfer (WPT) system with class-DE transmitter and class-E rectifier along with numerical design procedure. The proposed WPT system can achieve high power-transfer efficiency at high-frequencies because both the transmitter and the rectifier satisfy the class-E ZVS/ZDS conditions. By using numerical design procedure, it is possible to design the WPT system without analysis of the circuit and consideration of the impedance matching. By carrying out the circuit experiment, the validity of the design procedure and effectiveness of the proposed WPT system were confirmed. The laboratory measurement showed the 90.4 % overall power-transfer efficiency with 100 W output at 500 kHz operating frequency.

This paper presents analytical expressions of the MOSFET-parasitic-capacitance effects on the output envelope of the EER transmitter, taking into account the MOSFET linear gate-to-drain and nonlinear drain-to-source parasitic capacitances in the class-E amplifier. The analysis is useful to predict the behavior of the EER transmitter using the class-E amplifier. It is shown that the envelope of the output voltage is not in proportion to the dc-supply voltage due to the MOSFET-parasitic-capacitance effects. Additionally, the driving voltage waveform affects the output-voltage amplitude and phase shift between the driving voltage and the output voltage.

This paper gives analytical expressions for the output power and the power conversion efficiency of the class-E power amplifier outside the class-E ZVS/ZDS switching conditions. The analytical predictions agreed with the experimental results quantitatively, which indicates the validity of the analytical expressions. Moreover, a design example applying the analytical expressions for the power conversion efficiency is given. By using the analytical expressions, it is possible to design the class-E amplifier, which improves the power conversion efficiency compared with that of the class-E amplifier satisfying the class-E ZVS/ZDS conditions.

In this paper, we present analytical expressions for the waveforms and design equations for achieving the ZVS/ZDS conditions in the class-E power amplifier, taking into account the gate-to-drain parasitic capacitance of the MOSFET. We also give a design example along with PSpice simulation and experimental results. The voltage waveforms obtained from both the PSpice simulation and the circuit experiment achieved the class-E ZVS/ZDS conditions completely, which verify the analytical expressions. The results in this paper indicate that it is important to consider the effect of the MOSFET gate-to-drain capacitance for achieving the class E ZVS/ZDS conditions. The experimental power conversion efficiency achieved 92.8 % at output power Po= 4.06 W and operating frequency f = 7 MHz.