Coil System Optimization for Transcutaneous Energy Transfer Systems

This paper presents a design procedure for positioning tolerant air coil systems with maximum quality factor of the secondary coil. One design objective of transcutaneous energy transfer systems is a robust power supply to the implanted components. A varying coupling factor can significantly affect the transferred power, which potentially leads to the requirement of complex monitoring and control circuits. The proposed design procedure eliminates the variation of the coupling factor of a planar, rotationally symmetrical coil in lateral direction. This is achieved only by adjusting individual winding positions of the primary coil. The winding distribution of the secondary coil is adjusted for its maximum achievable efficiency. The design steps, based on analytical modeling, are described in detail. The results show that the coupling factor of a coil system with radii of 40 mm and 25 mm on primary and secondary side, respectively, can be kept almost constant for a lateral misalignment of over 50% of the secondary coil's radius.