Gao Han

This article presents a novel push-pull differential clamping Class E (PPDC-Class E) inverter and S/SP impedance compression compensation for wireless power transfer (WPT) systems. The proposed inverter incorporates voltage and current stress regulation and voltage-boosting capabilities, enabling configurable low stress levels and high voltage gain. Its auxiliary switches ensure load-independent zero-voltage switching (ZVS) and soft turn-off with minimal power dissipation. Furthermore, a systematic design approach for S/SP compensation is proposed to achieve impedance compression within WPT systems. Through parametric configuration, the voltage stress can be reduced to below $1.5~V_{DC}$ , the minimum current stress can approach $I_{DC}$ , and the AC voltage gain can exceed 3. Furthermore, the proposed S/SP compensation extends the ZVS load range of the inverter’s power switches. Finally, a 1-MHz, 500-W prototype has been constructed, confirming its effectiveness. The results demonstrate that the PPDC-Class E inverter exhibits wide-load-range ZVS operation and boost characteristics, with configurable switching voltage and current stresses through parameter selection. This inverter design achieves a peak efficiency of 97%.

In this paper, a novel secondary reconfigurable S/SP (R-S/SP) compensation network and parameter design method are proposed. The proposed compensation network can reconfigure the S/SP circuits by switching to implement load-independent constant-current mode (CCM) and constant-voltage mode (CVM), respectively, without the need for communication. The derivation of a generalized design methodology is given in detail based on the two-port network transfer matrix approach. By adjusting the parameter factors, the R-S/SP topology can maintain both the zero-voltage switch (ZVS) characteristic in the Class-D inverter’s wide load range and the stability of the voltage and current gains under misalignment tolerance. Also, the gains are tunable in this topology. Finally, a 0.6 MHz, 108 W inductive power transfer (IPT) prototype is developed with a CVM output of 72 V and a CCM output of 1.5 A. The experimental results show that load-independent switching of CCM and CVM can be implemented. The system can operate at a lateral offset of ±21%, with CCM gain fluctuations of less than 6.8% and CVM gain fluctuations of less than 9.9% over the full impedance range. The ZVS is realized throughout the process, and the system efficiency reaches 91.1% at maximum power.

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.

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 dual-band focused transmitarray antenna designed by using frequency selective surfaces (FSS) technique is proposed in this paper. Compared with the traditional transmitarray antenna, the proposed antenna has advantages of good ability to focus electromagnetic wave in the dual-band, high resistant of poor measurement environment and easy to process. The transmitarray consists of four identical metal phase shift layers, each of which is separated by an air gap. The elements distributed on metal layer are composed of a I-shaped slot at the center and four L-shaped slots with central symmetry. The change of I-shaped slot length affects the change of phase in low frequency band and the change of L-shaped slot length affects the change of phase in high frequency band. The mutual coupling between the two kinds of slots can be neglected. The proposed antenna consisting of a transmitarray and a feed has been analysed, simulated, and measured. The results show that the average focal spot diameter (SD) is 35.2 mm at 12 GHz and 24.5 mm at 18 GHz, and the dual-band focused transmitarray antenna can operate in two frequency bands 11.8-12.2 and 17.8-18.1 GHz. Simulated and measured results show that the proposed antenna has good concordance, making it possible for various microwave measurements.

Coaxial coupled structure of wireless power transfer, applied to high-precision instruments in aerospace, can eliminate interference sources by spatial isolation. For the optimization of the electromagnetic structure, a C-shaped magnetic structure is presented for both shielding electromagnetic simulation and improving coupling. By comparing of spiral and coaxial structures, an analysis is presented and validated in the effect of positional offset on inductive coupling, voltage gain, and efficiency. To obtain a stable and sufficient power supply, the prototype is implemented based on primary series-secondary series compensation topology with a maximum output power of 200 W, and a DC-DC efficiency of 82% is achieved.