Capacitor-less Wireless Power Transfer for Low Frequency Band Application

Abstract

Wireless power transfer (WPT) systems are employed in in-motion power supply applications for electric vehicles and related technologies. However, the use of resonant capacitors to achieve coil resonance often results in increased weight and cost. To address this issue, this study investigates a capacitor-less WPT system by incorporating a magnetic composite material with a high dielectric constant into the coil structure. This approach enhances both inductance and parasitic
capacitance, thereby reducing the resonant frequency. A finite element method (FEM) analysis was conducted to evaluate surface electric charge distributions, and the inductance, capacitance, and resonant frequency of the coil were subsequently calculated. The coil embedded with the magnetic composite material exhibited an inductance of 30 µH and a capacitance of 2.33 nF, yielding a resonant frequency of 601 kHz. Although this represents a reduction, the value remains higher than the target frequency of approximately 85 kHz commonly used in automotive in-motion WPT systems. Further
optimization of coil dimensions and structure is required to meet this specification.