The Internet of Things (IoT) connects billions of smart devices through wireless sensor networks (WSNs). However, to ensure the power supply for numerous passive devices in a WSN, it is necessary to replace batteries periodically, which will undoubtedly increase maintenance costs. This study proposes a capacitive coupling structure that is different from the previous capacitive power transfer (CPT) structures. The proposed structure can allow the positional variation of the receiver, and multiple receivers to be charged at the same time. Both theoretical and experimental results demonstrate that the power transmission is less affected by the positional variation of the pickup plates in the vertical and horizontal directions. In this study, all coupling capacitors between the plates are considered and the equivalent circuit model is derived. Further output characteristics of the circuit are derived and analysed. The dimensions of the structure are designed and simulated by using the EM full wave simulation. A prototype is designed to verify that a battery can be charged based on capacitive coupling. A 60 mAh rechargeable lithium‐ion button battery is fully charged in 250 min, and the output power is ∼36 mW during charging.

A 6.78-MHz wireless power transfer (WPT) system can achieve a long transmission distance, which is based on magnetically coupled resonant technology. Due to its high quality factor coils, the system performance is greatly affected by position displacement. In this paper, a weakly coupled and distance-insensitive WPT system with a dual-coupled L-type matching network was proposed. To improve displacement tolerance, the proposed system used a dual mutual inductance matching network, which did not require feedback to change capacitance or inductance dynamically. To remain lightweight, printed multi-coils without ferrites were used. To obtain a higher efficiency over a weakly coupled distance, a series of parameters were optimized, i.e., the optimal dimension, the matching distance, and the real center. To verify the output performance in X/Y/Z-axis displacements, a prototype with a maximum output power of 50 W was created, and a DC–DC efficiency of 75%–81% was achieved in a Z-axis displacement of ±15 mm and in an X/Y-axis displacement of ±20 mm.

In high-frequency wireless power transfer (WPT) applications, Class D, E, and F inverters are most widely used. Class DE inverters combine the respective advantages of Class D and Class E inverters. However, the Class DE inverter is sensitive to changes in impedance, which can easily lead to the loss of soft switching characteristics, thereby reducing efficiency. In this paper, an impedance-matching compensation design method is proposed to expand the high-efficiency region of the Class DE inverter by matching impedance and parameters. The effect of the method on the zero-voltage switching (ZVS) characteristic of Class DE inverters is analyzed in detail. The proposed WPT system maintains a constant voltage and zero phase angle by employing PS/PS compensation topology. Theoretical analysis shows that the impedance can be compressed for the design of resonant network impedance, and the method can expand the high-efficiency region with a reasonable choice of parameters to match the phase. Finally, a 500 kHz, 1 kW WPT prototype was constructed with a coupling factor of 0.25–0.4 and a load range of 30–80 Ω. The inverter’s efficiency exceeds 95%, with optimal efficiency reaching 97.3%. The system efficiency is greater than 87%.