6.78 MHz loosely coupled inductive wireless power transfer with series-parallel resonators

In a recent trend, near distance wireless power transfer (WPT) for low-power applications has increased exponentially. However, issues such as high harmonic content at the input side of the transmission coil and very low WPT efficiency are persistent. Therefore, a new magnetic resonance WPT (MRWPT) system has been proposed to overcome the aforementioned issues. This paper introduces an LC compensated half-bridge class-D inverter, which minimizes the harmonic content from the input source and makes the MOSFET of the inverter perform zero voltage switching. Simultaneously, a matching capacitor is connected between the resonant coil and the compensated inverter to suppress the reactive power loss. In addition, a series-parallel (SP) structured resonance coil has been introduced for low-power applications due to its high-efficiency WPT capability in near and mid-range distances. The introduced structure acts as a current source-transmitting resonator and a voltage source receiving resonator, which ensures the guaranteed resonance regardless of load variations. The performance of the proposed MRWPT system is analyzed using two-port scattering or S-parameter in the high-frequency structure simulation (HFSS) of ANSYS software. To validate the performance of the simulated system, an experimental 7 W setup has been designed to charge a mobile device.