Reactive Shielding Method for Wireless Power Transfer Systems with High Power Transfer Efficiency using Frequency Split Phenomena

EMI reduction could be achieved using the method suggested by the wireless power transmission system. Leakage magnetic fields occur in the process of transmitting power wirelessly from the transmitter part to the receiver part. This leakage magnetic field negatively affects the human body or other electronic devices. The previous reactive shielding method could reduce the leakage magnetic field, but it had the disadvantage of reducing the power transfer efficiency (PTE). Using frequency split phenomena from the over-coupling, the reactive shielding method can reduce the EMI components with high PTE WPT system. In this paper, a reactive shielding method that can reduce the magnetic field while increasing PTE is proposed. In addition, a method for calculating a coupling coefficient for designing a structure in which magnetic field reduction can be maximized is also proposed. The theoretical analysis based on each part’s impedance strongly correlates with the measurement results. As a result of the experiment, the PTE is increased by about 3.9%, and EMI components at odd harmonic frequency can be reduced by up to 8.85 dB in a 20 W-WPT system. Also, the proposed method can be applied when the other WPT system to be shielded is determined.