BPN555: Power Transfer Over a Capacitive Interface


The simplicity and low cost of capacitive interfaces makes them very attractive for wireless charging stations. Major benefits include low electromagnetic radiation and the amenability of combined power and data transfer over the same interface. We present a capacitive power transfer circuit using series resonance that enables efficient high frequency, moderate voltage operation through soft-switching. An included analysis predicts fundamental limitations on the maximum achievable efficiency for a given amount of coupling capacitance and is used to find the optimum circuit component values and operating point. Automatic tuning loops ensure the circuit operates at the optimum frequency and maximum efficiency over a wide range of coupling capacitance and load conditions. An example interface achieves near 80% efficiency at 3.7W with only 63 pF of coupling capacitance. An automatic tuning loop adjusts the frequency from 2 to 8 MHz to allow for a wide range of alignment conditions. On- off modulation is used to maintain efficiency at light loads.

Project end date: 08/17/12

Publication date: 
February 1, 2012
Publication type: 
BSAC Project Materials (Final/Archive)
PREPUBLICATION DATA - ©University of California 2012

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