An Improved Ground Stability in Shielded Capacitive Wireless Power Transfer

A shielded capacitive power transfer (S-CPT), a method of wireless power transmission (WPT) in which using electric field resonant (EFR) with an improved ground stability is proposed in this paper. The feature of ground stability can be succeeded simultaneously by using 1:1 Ruthroff transmission line transformer (TLT) balun. The unbalanced condition from the power source is converted to the balanced condition by the transformer. The analytical study of the shield plate voltage stability is also described both the simulation and hardware experiment. By using Spice software, with the proposed system, the simulation results show the constant zero voltage value from the shield plate to the ground. An experiment was conducted for validations of the proposed S-CPT with balun at 6.78 MHz resonant frequency. A measured shield voltage was compared under the unbalanced and balanced condition with the value of 20 V (peak to peak) and steadily of 5 V (peak to peak). An enhancement of the shield voltage ground stability is developed successfully with 75% of swing voltage reduced by the implementation of the TLT balun.