Load-independent current output of inductive power transfer converters with optimized efficiency

Inductive power transfer (IPT) systems are resonant converters whose output characteristics are mostly load dependent. Conditions for ensuring a load-independent voltage-transfer ratio of an IPT system have been studied. However, load-independent current output can be more desirable for applications such as battery charging and LED driving. This paper studies the characteristics of IPT systems operating at different frequencies as transconductance converters. Operating frequencies for load-independent transconductance are explored, looking for optimal efficiency. The frequencies interested are found to facilitate the design of a current-output IPT converter with efficient power conversion. The analysis is supported by experimental results.