Design and Analysis of LCC-S Wireless Power Transfer Systems Considering Load-Dependent Leakage Magnetic Field

This article analyzes the characteristics of the harmonic components in wireless power transfer (WPT) systems depending on load in the LCC -S topology. In a WPT system, the equivalent load can be changed depending on the charging state. Depending on the equivalent load, the operation of the rectifier can be divided into two modes. The first is continuous conduction mode (CCM), and the second is discontinuous conduction mode (DCM). The harmonic characteristics in CCM and DCM operation were each analyzed. The electromagnetic field (EMF) level is the largest when the output power was the largest. However, the electromagnetic interference (EMI) level is largest when the magnitude of the load was at the boundary between CCM and DCM. In practical WPT systems, a dc–dc converter is used for output voltage regulation, and by using the converter, the equivalent load can be changeable. A design method to suppress the leakage magnetic field is proposed in terms of EMF and EMI. Through simulation and experiment, we verified when EMF and EMI levels have the largest value. Also, the effect of suppressing the leakage magnetic field was verified by changing the value of the equivalent load.