A Symmetrical Winding Pattern for Common-Mode Noise Reduction in Inductive Power Transfer Systems

In high-power inductive power transfer (IPT) systems, ferrite layer and grounded shielding layer are usually adopted to mitigate the magnetic- and electric- field exposed to the environment. However, with substantial parasitic capacitance between the planar winding and the shielding layer, severe common-mode (CM) noise is generated with the excitation of high dv/dt along the planar windings. As a result, significant CM electromagnetic interference (EMI) is created, affecting the normal operation of nearby electronic equipment. In this letter, symmetry circuit is applied to mitigate the CM noise in IPT systems. To realize a fully symmetrical propagation path and enhance CM noise cancellation, a symmetrical pattern of planar winding is proposed to reduce the CM noise without additional component. A 3-kW IPT system is built in the lab, and the proposed symmetry circuit with symmetrical pattern of planar winding can achieve 30 dB of CM noise reduction, improving the electromagnetic compatibility of the IPT systems.