Frequency Bifurcation Conditions for Capacitive Wireless Power Transfer with Multiple Receivers

Capacitive wireless power transfer applies the electric field to transport energy from a transmitter to a receiver. However, if the distance between transmitter and receivers varies, the efficiency or power transfer is reduced for a system with a fixed load. By applying the bifurcation phenomenon, the system can be operated in a coupling-independent regime, resulting in a (nearly) constant efficiency or power transfer at fluctuating coupling. However, a future need can be expected to charge multiple devices simultaneously by a single transmitter. Unfortunately, the conditions for which frequency bifurcation occurs are not yet determined for capacitive wireless power transfer with multiple receivers. In this work, these constraints are analytically determined. A quartic equation is found that expresses the bifurcation conditions for a general capacitive wireless power transfer system. If the receivers are identical, the condition reduces to a quadratic equation. Finally, the analytical results are illustrated by a numerical example.