Sensing Movable Receiving Coils by Detection of AC Current Changes on the Primary Side of a Multi-Coil System

Abstract

Position detection is very important for inductive power transfer systems with movable receivers, in order to switch off inactive coils and to reach a high efficiency. The solution presented in this paper is based on the measurement of the current amplitudes in sending coils, which show a significant difference between no targets, metallic targets and receiving coils. A galvanically separated circuit is designed to implement the new method by transforming the current of the sending coils to a DC voltage and then comparing it to the detection threshold. Finite element simulations were carried out to predict the value of the detection threshold. Both simulation and experimental results show that the circuit fulfils the detection requirements with high precision and high detection height. The proposed method represents a smart, efficient and low cost detection technique for inductive systems with a movable receiver, independently on position and speed.