An inductive wireless charger for electric vehicle by using LLC resonance with matrix ferrite core group

A wireless LLC charger using primary-side resonance to achieve magnetic inductive coupling with matrix core set (MCS) is proposed for power transfer to electric vehicle. The MCS consists of usual low cost ferrite core in matrix form, including transmitter MCS (TX MCS) and receiver MCS (RX MCS), in which both two MCSs are expected to be coupling close in proximity. Although the leakage inductance may result in inevitable poor coupling between TX MCS and RX MCS, the LLC resonator can effectively absorb it to be a resonant element to eliminate harmonic noise. In order to facilitates analysis, a transconductance G_m(jω) instead of the usual voltage gain G_v(jω) is presented to clearly describe the LLC behavior that can be depicted by load trace continuous in or between Region 1 and Region 2 of DC characteristics without interruption. In addition, the modeling of TX-RX transformer with MCS is conducted for the analysis of LLC resonance to power transfer. Finally, a scale-down 450-W wireless LLC charger for a 24-V battery in electric vehicle is experimented to assess the described the power transfer behavior. The experimental results successfully achieve nearly 90% resonant power transfer and meet the expected performance for feasibility.