Multiple dipole receiving coils for 2-D omnidirectional wireless mobile charging under wireless power zone

Multiple dipole receiving (Rx) coils, which are applicable to ubiquitous mobile device charging applications, are newly proposed in this paper. By using the proposed Rx coils, any mobile devices equipped with the proposed Rx coil can be freely charged regardless of direction anywhere and at any time in wireless power zone, where a uniformly distributed magnetic flux environment is provided for wireless power transfer. For high induced voltage in the proposed Rx coils, multiple dipole coils are used to reduce the leakage magnetic flux through the air for x-and y- axes under the given structure, considering the quantity of the core. An aluminum plate was adopted in the proposed Rx coils so that the electro-magnetic field (EMF) would not exceed the permitted international guideline, i.e., ICNIRP guideline. The inductance variation due to adjacent of the conductors is analyzed and quality factor of the Rx coil is designed to guarantee high voltage gain regardless of proximity of conductors. A detailed analysis and design procedure of the proposed Rx coils are established. For experimental verifications, the size of Samsung Galaxy Note was implemented for a prototype, where the induced voltages V_x = V_y = 9.2 V for x- and y-axes were obtained at B_0y = 20 μT and the magnetic flux was reduced by 40% over the aluminum plate for human safety. 1.0 W continuous power transfer was achieved by y-axis of the proposed Rx coils, which is quite enough to recharge the mobile device in the proposed ubiquitous wireless power zone.