Design and optimization of a power inductive link

The wireless power transfer efficiency plays an important role in design of implantable biomedical devices. There are some important constraints in the design, such as the size of the implantable coil as well as the power delivered to the implant. In this context, this paper presents the design of two planar spiral coils coupled by air used to transferring energy wirelessly. The geometric constraints of the application are determined to define the dimensions of the coils. These parameters along with the working frequency of the system are applied to a procedure that results in the equivalent electrical model characterization of the coils, as well as mutual inductance. A capacitor matching network is then determined in order to optimize two objective functions: efficiency of the whole link and power transferred to the load. Since in a practical application the values of the capacitors are discrete and limited to a commercial series of values, we developed a numerical procedure to conduct a search of the best results of both objective functions. This network is characterized by being made up of a series-parallel network at both the input and output. The sequence of this work includes the development of an oscillator used as the primary voltage source and the experimental evaluation of the entire system.