Rapid Wireless Capacitor Charging Using a Multi-Tapped Inductively-Coupled Secondary Coil
Author(s)Mercier, Patrick Philip; Chandrakasan, Anantha P.
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This paper presents an inductive coupling system designed to wirelessly charge ultra-capacitors used as energy storage elements. Although ultra-capacitors offer the native ability to rapidly charge, it is shown that standard inductive coupling circuits only deliver maximal power for a specific load impedance which depends on coil geometries and separation distances. Since a charging ultra-capacitor can be modeled as an increasing instantaneous impedance, maximum power is thus delivered to the ultra-capacitor at only a single point in the charging interval, resulting in a longer than optimal charging time. Analysis of inductive coupling theory reveals that the optimal load impedance can be modified by adjusting the secondary coil inductance and resonant tuning capacitance. A three-tap secondary coil is proposed to dynamically modify the optimal load impedance throughout the capacitor charging interval. Measurement results show that the proposed architecture can expand its operational range by up to 2.5 × and charge a 2.5 F ultra-capacitor to 5 V upwards of 3.7 × faster than a conventional architecture.
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
IEEE Transactions on Circuits and Systems I Regular Papers
Institute of Electrical and Electronics Engineers (IEEE)
Mercier, Patrick P., and Anantha P. Chandrakasan. “Rapid Wireless Capacitor Charging Using a Multi-Tapped Inductively-Coupled Secondary Coil.” IEEE Transactions on Circuits and Systems I: Regular Papers 60, no. 9 (September 2013): 2263–2272.
Author's final manuscript