Load position detection and validation on variable-phase contactless energy transfer desktops

Abstract

In this paper, a method for locating and validating different load devices placed on a variable-phase CET desktop is presented. The CET desktop consists of multiple embedded primary coils, which have the ability to power small electronic devices, such as cellular phones, music players, and PDA's laying on its surface. Here, only the three primary coils closest to the load device are used to transfer power, and it is thus important for the system to correctly locate the positions of the load devices laying on the table. The presented method can detect the positions, and distinguish between three different types of objects placed on the table, namely, valid resonant load devices, conductive materials and ferrites. The objects are detected through the process of ldquoscanningrdquo which involves energizing each coil for a short duration of time, while measuring its impedance. Each object type influences the coil impedance in a different manner, which can be detected by the CET system. In this way, the object positions and types can be accurately estimated. The system is implemented, and various load detection experiments are performed on the prototype. The results show measurable and predictable changes in the coil impedances, and the system is able to correctly locate and identify all the objects placed on the CET desktop.