Coupling-Independent Capacitive Wireless Power Transfer With One Transmitter and Multiple Receivers Using Frequency Bifurcation

Abstract

Capacitive wireless power transfer utilizes capacitive coupling to transfer electrical energy wirelessly. Due to the nature of the coupling, it is seen as a well-suited technique for single input multiple outputs configurations. For these systems, optimal solutions for power transfer and efficiency exist, however, with variation in distance or alignment, the coupling varies and as a result, these optimal solutions vary. Therefore, there is a need for coupling-independent approaches to keep these systems within their optimal operating conditions. In this work, we propose a frequency-agile mode, using frequency bifurcation, that allows for a nearly coupling-independent power transfer and efficiency regime for a capacitive wireless power transfer system with one transmitter and multiple receivers. The conditions for bifurcation are described and analytical expressions for the power and transducer gains are determined. It is shown that, when operating at the secondary resonances, nearly constant efficiency and power transfer to the load can be achieved. An experimental setup was realized and the results validate the theoretical results, showcasing a coupling-independent efficiency and power output with a more than four-fold increase in output power at the cost of less than $5\%$ reduction in absolute efficiency.