Design and Analysis of Four-Plate Capacitive Couplers for Wireless Charging Systems

Capacitive power transfer (CPT) systems have become a popular alternative to inductive power transfer (IPT) systems owing to their unique features such as better misalignment tolerance, relatively inexpensive, and lightweight. However, the main concern with CPT is the low coupling capacitance (typically pico farads (pF) range) between transmitter and receiver plates due to the natural low permittivity in air. Consequently, the power transfer capability is limited, which makes CPT systems unsuitable for high-power large air gap applications. This paper investigates a new four-plate coupler structure with a dielectric medium on the transmitter and receiver plates. The proposed design of the CPT coupler increases the coupling coefficient and improves the power density of the coupler with a better misalignment tolerance. The effectiveness of the proposed CPT coupler is validated through ANSYS-Maxwell simulations. Furthermore, its performance is compared with other configurations in terms of electric field emissions, misalignment tolerance, and coupling capacitance values at a constant excitation.