Design of an inductively coupled wireless power system for moving receivers

Present-day commercial wireless inductive power transfer systems rely on a low frequency alternating magnetic field, generated by a transmitter coil and picked up by a receiver coil. In general, these inductively coupled coils are perfectly aligned, in order to obtain a constant high coupling factor. In some cases though, the receiver can move on a regular basis above the transmitter. This paper discusses a method to wirelessly power a device moving on a surface. The transmitter consists of a single coil that is significantly smaller than the operation radius of the moving receiver. Therefore, the receiver is not always in the range of the transmitter and the power transfer occurs intermittent. In order to provide the receiver with a constant energy supply, a supercapacitor buffer is implemented. When the receiver approaches the transmitter, the buffer is charged in a short period of time. Furthermore, a communication channel is set up from the power receiver to the power transmitter, enabling receiver identification and power management.