Abstract:Cardiac pacemakers, reliant on lithium batteries, necessitate frequent surgical replacements due to limited capacity. Magnetically coupled resonant wireless power transfer (MCR-WPT) technology holds substantial potential for implanted medical devices, but challenges such as transmission efficiency and safety require resolution. In the MCR-WPT system, the composite compensation topology enhances system robustness under offset conditions while meeting constant voltage or constant current output requirements. However, the independent inductance contributes to an increased volume, constraining its application in implantable devices. To address this issue, this paper proposes a wireless power transmission system for cardiac pacemakers based on the LCC-LCC magnetically integrated printed spiral coil (PSC), achieved by incorporating the compensation inductor into the main coil in concentric circles. By constructing a coil model to analyze the impact of turn width and turn spacing on the transmission efficiency of PSC under a fixed filling ratio, the optimal PSC structure is determined. Simulation models for non-integrated and integrated coupling mechanisms are established, and the magnetic field distribution is calculated under lateral and angle offset conditions. Concurrently, a comparison is made between the non-integrated MCR-WPT system and the integrated MCR-WPT system. Experimental results demonstrate that the integrated structure exhibits superior anti-offset capability and transmission efficiency compared to the non-integrated counterpart. At a frequency of 6.78 MHz, the integrated MCR-WPT system achieves a transmission efficiency of 68.1% and an output power of 1.28 W. In comparison with the non-integrated structure, the integrated structure shows a 5.8% increase in transmission efficiency and a 0.39 W boost in output power. In the offset experiment, a horizontal offset of 20 mm for the receiver results in a notable enhancement in the transmission efficiency of the integrated MCR-WPT system, rising from 19.5% to 36.8% compared to the non-integrated MCR-WPT system. Similarly, for receiver offsets at 15° and 30° angles, the transmission efficiency of the integrated MCR-WPT system surpasses that of the non-integrated counterpart significantly. In these instances, the transmission efficiency escalates from 33.7% to 59.6% at 15° and from 19.7% to 32.3% at 30°. Furthermore, a three-dimensional model of the human upper body is constructed for the safety assessment of the system. The simulation includes the analysis of the distribution of electric field intensity and SAR (specific absorption ratio) value in the human body during wireless charging. Results indicate that during the operation of the MCR-WPT system, the peak values of electric field intensity and SAR value in human tissue are 41.688 V/m and 0.725 1 W/kg, respectively. These values fall below the ICNIRP guidelines and IEEE standards. The international radiation safety limit standard proposed by the standard aligns with safety specifications, affirming that the system meets electromagnetic safety requirements during charging. This paper integrates independent inductance into the main coil in a coil form, effectively reducing system volume and enhancing integration. This offers valuable insights for the exploration of a wireless charging system for cardiac pacemakers utilizing PSC as a magnetic coupling integrated structure. Additionally, it contributes positively to advancing the standardized production of implantable energy transfer systems, facilitating progress in system productization.
陈伟华, 宋宇航, 闫孝姮, 姚金姝, 葛帅帅. 心脏起搏器无线电能传输LCC-LCC磁集成印刷螺旋线圈研究[J]. 电工技术学报, 2024, 39(17): 5289-5299.
Chen Weihua, Song Yuhang, Yan Xiaoheng, Yao Jinshu, Ge Shuaishuai. Research on Wireless Power Transmission for Cardiac Pacemakers Using LCC-LCC Magnetic Integrated Printed Spiral Coil. Transactions of China Electrotechnical Society, 2024, 39(17): 5289-5299.
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