Enhanced Power-Delivered-to-Load Through Planar Multiple-Harmonic Wireless Power Transmission

In this brief, a method is presented to enhance the amount of power delivered to load (PDL) by making use of three-harmonic wireless power transmission while it does not occupy larger area than a conventional single-coil system. The proposed system consists of three inductive links each one tuned at a harmonic of the operating frequency. A single power amplifier supplies all of them. Therefore, the sum of the currents flowing through the secondary-side coils becomes almost square-wave and PDL will be 32.5% greater than that of a conventional single-coil system when both systems are supplied with the same voltage source. The parasitic inter-couplings between the coils deform the current waveform and make the PDL enhancement unachievable. Thus, a perpendicular 8-shaped coils structure is proposed to diminish these parasitic couplings and all the coils can be planar and coaxial. A laboratory prototype has been fabricated on printed circuit board operating at the frequency of 200 kHz. The experimental results confirm that the PDL is enhanced from 1.93 to 2.5 W by employing the proposed technique rather than a single-coil system.