On the Influence of the Parasitic Capacitance of a Bridge Rectifier on Series-Resonant Capacitive Wireless Power Transfer Systems

Capacitive wireless power transfer systems often rely on high frequency power converters and incorporate a resonant coupling link. The input capacitance of a bridge rectifier alters the overall power transfer of a capacitive power transfer system with a series-resonant transfer link. In this field, most analytic converter models are based on a representation of the rectifier as an equivalent resistance, thus neglecting the parasitic properties and the switching behavior of the rectifier. In this paper, studies on said issue are conducted by using a complex power and a time-domain approach. It is shown that through an extension of the capacitance at the rectifier input the transferred power can be increased. An optimal value for the rectifier input capacitance exists, thus maximizing the power. The rectifier capacitance creates an additional degree of freedom in the converter design, influences the soft switching behavior of the inverter, and may be used to improve robustness against a variation of the link capacitance.