Design of Wireless Power Transmission by Using Planar Magnetically Coupled Resonators

摘要

Wireless power technology could cut the last wire of portable devices, allowing users to recharge portable devices easily through the air. Wireless power technology can be divided into three categories: Inductive coupling techniques, Far-field techniques, and electromagnetic resonance techniques. Inductive coupling techniques can be very efficient, but the transmission distances are usually less than one centimetre. Far-field techniques can transfer power over kilometer distances, but they are usually not efficient. Electromagnetic resonance couplings have been proposed by MIT and named WiTricit. In a weak coupling at resonance, magnetic resonance couplings can transfer energy efficient at large air gap. However, the sizes of coils were too big to be equipped on any portable devices. In this paper, the feasibility of wireless charging system using planar magnetically coupled resonators to reduce the size has been designed and fabricated. The power system consists of a power resonator, a Tx resonator, a Rx resonator, and a load resonator. The Tx resonator and the Rx resonator have the same shape, and the dimension is 40mm x 40 mm x 0.1mm. The power resonator and load resonator have the same shape, and the dimension is 15mm x 15 mm x 0.1mm. A prototype wireless battery charger is used as an example to demonstrate its application. The results are verified with simulations using a commercial field solver (SONNET) as well as fabricated on printed circuit boards. The system has a power delivery of 0.5W at 13.56MHz. We measure the wireless power transfer efficiency of about 80.66% being achieved by magnetically coupled resonators at 25mm separations. Index terms - planar, wireless power, magnetic, resonance