Design and Optimization of Resonance-Based Efficient Wireless Power Delivery Systems for Biomedical Implants

• Published in: IEEE transactions on biomedical circuits and systems Vol. 5; no. 1; pp. 48 - 63
• Main Authors: RamRakhyani, A K, Mirabbasi, S, Mu Chiao
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.02.2011; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Biomedical implants; Coils; coupling coefficient; Couplings; Design; Driver circuits; Efficiency; Energy transfer; Implants; Inductance; inductive wireless power links; power transmission efficiency; Prototypes; Resistance; Resonance; resonance-based power delivery; Studies; telemetry; Wire; wireless power transfer
• ISSN: 1932-4545; 1940-9990
• DOI: 10.1109/TBCAS.2010.2072782

Resonance-based wireless power delivery is an efficient technique to transfer power over a relatively long distance. This technique typically uses four coils as opposed to two coils used in conventional inductive links. In the four-coil system, the adverse effects of a low coupling coefficient between primary and secondary coils are compensated by using high-quality (Q) factor coils, and the efficiency of the system is improved. Unlike its two-coil counterpart, the efficiency profile of the power transfer is not a monotonically decreasing function of the operating distance and is less sensitive to changes in the distance between the primary and secondary coils. A four-coil energy transfer system can be optimized to provide maximum efficiency at a given operating distance. We have analyzed the four-coil energy transfer systems and outlined the effect of design parameters on power-transfer efficiency. Design steps to obtain the efficient power-transfer system are presented and a design example is provided. A proof-of-concept prototype system is implemented and confirms the validity of the proposed analysis and design techniques. In the prototype system, for a power-link frequency of 700 kHz and a coil distance range of 10 to 20 mm, using a 22-mm diameter implantable coil resonance-based system shows a power-transfer efficiency of more than 80% with an enhanced operating range compared to ~40% efficiency achieved by a conventional two-coil system.