Capacitive power transfer (CPT) has garnered significant interest in recent years, driven by efforts to enhance power and efficiency. This article presents advancements in CPT technology, focusing on the design of a novel five-plate coupler and the optimization of CPT systems. The proposed five-plate coupler features single-side shielding, which aims to simplify design complexity and reduce costs while maintaining performance. This study characterizes the five-plate coupler and compares its performance to traditional even-numbered plate configurations, highlighting the differences between odd and even plate designs and the unique characteristics of asymmetric couplers. In addition, the factors influencing efficiency are investigated, and an optimization method for CPT systems with asymmetric couplers is proposed to enhance the overall system performance. Experimental validation includes the development of a 5-kW prototype CPT system with a 100 mm airgap, achieving an impressive efficiency of 96.5%. These findings underscore the potential of the proposed design and optimization approach to set new benchmarks for CPT systems, facilitating their broader application in high-power scenarios.

Wireless power transfer (WPT) is more convenient and safer than conductive charging for power consumer electronics, biomedical devices, transportation systems, etc. Inductive power transfer is the most widely studied and commercialized WPT technique; however, capacitive power transfer (CPT) is becoming an attractive alternative, offering better misalignment tolerance and lower cost and weight. The electrical-field-resonance-based six-plate coupler system is one of the most typical configurations for high-performance CPT systems, but the associated large number of circuit parameters is always a critical issue for system design. In this article, a parameter optimization method is proposed for this topology. The ratio of the reactive power in the compensation network to the system transferred power is set as the main optimization goal. To solve the high-order optimization problem, a two-stage method is proposed to significantly reduce the optimization complexity while providing the optimized parameters of the whole system. To verify the effectiveness of this method, a 3-kW, 1-MHz CPT system with a 16-pF coupling capacitor is built. Both the simulation and experimental results show that the optimized parameters effectively improve the system efficiency, experimentally achieving 95.7% dc–dc overall efficiency under a 100-mm gap distance at the rated power.

Wireless power transfer technology is being widely used in electric vehicle wireless-charging applications, and foreign object detection (FOD) is an important module that is needed to satisfy the transmission and safety requirements. FOD mostly includes two key parts: metal object detection (MOD) and living object detection (LOD), which should be implemented during the charging process. In this paper, equivalent circuit models of a metal object and a living object are proposed, and the FOD methods are reviewed and analyzed within a unified framework based on the proposed FOD models. A comparison of these detection methods and future challenges is also discussed. Based on these analyses, detection methods that employ an additional circuit for detection are recommended for FOD in electric vehicle wireless-charging applications.

In this letter, we introduce a novel hybrid wireless power transfer (HWPT) coupler that efficiently integrates magnetic and electric field transmission channels within a single structure using a comb-shaped design. For the first time, this design places electric field coupling plates between two magnetic field coils, while ensuring unobstructed magnetic flux passage and minimizing eddy current losses. This approach significantly enhances overall efficiency and power transfer capability. First, the design methodology of the coupler is elaborated, and a comprehensive analysis of its characteristics is provided. In addition, an equivalent model of the HWPT system with double-LC compensation is established, and the system's output power is derived. An experimental prototype with coupler dimensions of 600 mm × 600 mm and a transmission distance of 150 mm was constructed. The system successfully achieved an output power of 2.2 kW with a dc–dc efficiency of 92.6%, verifying the effectiveness of the proposed structure in reducing losses caused by the integration of magnetic and electric fields.

Wireless charging technologies are widely used in electric vehicles (EVs) due to their advantages of convenience and safety. Conventional wireless charging systems often use planar circular or square spiral windings, which tend to produce strong electric fields (E-fields), leading to electromagnetic interference (EMI) and potential health risks. These standard coil configurations, while efficient in energy transfer, often fail to address the critical balance between E-field emission reduction and power transfer effectiveness. This study presents an “Alternating Voltage Phase Coil” (AVPC), an innovative coil design that can address these limitations. The AVPC retains the standard dimensions of traditional square coils (400 mm in length and width, with a 2.5 mm wire diameter and 22 turns), but introduces a novel current flow pattern called Sequential Inversion Winding (SIW). This configuration of the winding significantly reduces E-field emissions by altering the sequence of current through its loops. Rigorous simulations and experimental evaluations have demonstrated the AVPC’s ability to lower E-field emissions by effectively up to 85% while maintaining charging power. Meeting stringent regulatory standards, this advancement in the proposed coil design method provides a way for WPT systems to meet stringent regulatory standards requirements while maintaining transmission capability.

This paper introduces a perfectly symmetrical planar spiral receiving coil (PS-coil) for large-space wireless power transfer (WPT) systems, designed to significantly reduce electric field (E-field) exposure. The coil’s structure utilizes multiple symmetrically wound spiral wires, replacing traditional single-wire coils. This symmetry facilitates distributed and precise capacitor compensation, effectively mitigating the effects of parasitic capacitance and associated E-field exposure. The PS-coil preserves the magnetic field (H-field) distribution while significantly reducing E-field emissions, allowing for greater power reception within the limits set by the International Commission on Non-Ionizing Radiation Protection guidelines (2020). Finite element simulations indicate that at an effective current of 6 A, the PS-coil achieves a local specific absorption rate (SAR) of 0.72 W/kg at a 1 cm distance—80% lower than traditional designs and well below the 2 W/kg guideline. Finally, a prototype model, comparable in size to an iPad, confirms that the calculated inductance is within 2% of the measured values, with a self-resonance frequency 38% higher than that of traditional coils. Tests in a large space, 3 m in diameter and 2.4 m high, demonstrate that the PS-coil can transmit over 200 W with 54.8% efficiency. Additionally, comparisons of traditional coils with the proposed PS-coil under the same conditions indicated an 18.9 dB reduction in E-field exposure.