Quarter Wavelength Surface Structures for Improved Operation in Unipolar Capacitive Power Transfer

Unipolar capacitive power transfer is a unique technique that enables power transmission over single conducting surfaces. The counter electrode is generally an earth ground that is physically isolated from users. This improves safety and alleviates many short-circuiting issues that a bipolar (two plate) capacitive system might encounter. Recent work has shown that by designing the unipolar capacitive receiver to operate in a standing wave resonance mode, surface voltages can be significantly lower with greater power transfer capacity and efficiency. One major challenge to this approach is the influence of surrounding objects which detune the receiver when in close proximity - ceasing power transfer to the receiver's attached load. Here we present a method to mitigate the detuning effect by incorporating a network of quarter wave structures under the power transfer surface. The quarter wave structures create a “wave-shaped” electric field distribution that is confined to a 0.3 m distance surrounding the surface. This greatly reduces the open-ended field emissions while lessening the detuning effect of the receiver from nearby objects. The efficiency and power transfer of the system is analyzed based on the operation of a 10 W LED filament lamp. The effects on the output parameters of the power supply in conjunction with the delivered power as the receiver is spatially varied is explored.