Cylindrical Transmitting Coil for Two-Dimensional Omnidirectional Wireless Power Transfer

Abstract

Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This paper proposes a cylindrical-shaped coil, which can produce the homogeneous magnetic field in a plane. The coil consists of two helical windings, which are wound to guide the current in opposite directions. A single power source is used to excite the transmitter without any current amplitude or phase control circuits. Furthermore, since the parasitic capacitance of the coil is not negligible due to the complexity of the coil shape, we develop a general equivalent model with parasitic capacitance for the analysis of complex coils. The system efficiency of the proposed omnidirectional wireless power transfer device is validated by a practical experiment. The measured DC-to-DC efficiency of approximately 72.4% and the load power of 13 W are demonstrated for the proposed wireless charging system at 6.78 MHz operating frequency. Finally, we verify that the electromagnetic exposure satisfies the safety regulations.

Parasitic Capacitance Analysis in High-Frequency Wireless Power Transfer Systems

“…Calculation and simulation are conducted with R L = 50 Ω at frequency f = 6.78 MHz.The parameters of Tx coil, Rx coil are shown in Table I, referred to the actual equivalent values in [8]. The series compensation capacitors C 3 , C 4 are calculated according to Section A in order to achieve ZPA and maximum load power or maximum efficiency.…”

“…One effective solution for enhancing the transfer distance is to perform the WPT system at a higher frequency, in which a long distance can be achieved when maintaining the same power transfer capability [7]. However, in a high-frequency WPT system, the parasitic capacitance of the coil is significant and cannot be neglected [8]. In this paper, we focus mostly on the theoretical analysis of the WPT system with parasitic capacitance and introduce its great impact on the WPT system's operation.…”

Mid-range wireless power transfer: anapoles or magnetic dipoles?

“…Wireless power transfer (WPT) since 1980s [1] has been increasingly becoming an important technology for diverse applications, see e.g. [2][3][4]. Over the past decade, rapid proliferation of wireless devices has motivated accelerated advancements of wireless powering and charging technologies (see e.g.…”

Effective Midrange Wireless Power Transfer with Compensated Radiation Loss

“…In this short-range WPT regime, the power is transferred predominantly by the near fields, whereas the radiation is usually considered as a parasitic factor resulting in some radiation loss that decreases efficiency (see, e.g., Refs. [5][6][7][8][9][10][11][12]). In this regime it appears that it is desirable to suppress antenna radiation.…”