Abstract
Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This article 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.
Highlights
W IRELESS power transfer (WPT) has become rather ubiquitous because of its advantages in applications such as consumer electronic products, portable devices, robotics, electric vehicles, and biomedical implants [1]–[6]
Compared to conventional omnidirectional WPT systems with multiple Tx coils connected to multiple power sources, we propose a single Tx coil fed by a single power source without any active control of amplitude or phase, which will greatly reduce the complexity and cost
Based on the above investigations of the proposed 2-D omnidirectional WPT system, it is clear that the proposed Tx coil is a superior candidate consumer applications, such as portable and mobile wireless charging, in terms of the performance and the omnidirectionality
Summary
W IRELESS power transfer (WPT) has become rather ubiquitous because of its advantages in applications such as consumer electronic products, portable devices, robotics, electric vehicles, and biomedical implants [1]–[6]. The main objective of this work is to introduce a new coil structure that can yield a truly 2-D omnidirectional WPT without any blind spots, not requiring any active control or tuning This enables Rx devices to be charged equivalently at any angular positions around the Tx antenna. Compared to conventional omnidirectional WPT systems with multiple Tx coils connected to multiple power sources, we propose a single Tx coil fed by a single power source without any active control of amplitude or phase, which will greatly reduce the complexity and cost. A new cylindrical Tx coil structure is proposed to transfer power in 2-D omnidirectional space such that receivers can be placed or moved freely without compromising power delivery To achieve this goal, we configure magnetic field in an unusual manner by guiding the current flows in two opposite directions of two parallel helical coils. A context of a consumer application with the SAR validation is described in Section IV, followed by conclusions
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