Wireless Power Systems Design for Implantable Biomedical Devices

技术驱动型社会的日常需求，专注于创新和不断重新发明我们日常生活中使用的几乎所有产品，导致了我们在上个世纪经历的巨大进步。年复一年，我们不断地从一个被认为是“完美”的产品转变为更好的产品。从固定电话到移动电话，再到便携式电脑，一切都在不断变化和发展。随着需求的不断推动技术进步，无线电源最近已成为许多应用中最迫切的需求之一，从汽车到消费电子，也涵盖了军事和医疗保健等领域。这个博士项目的出发点旨在解决植入式生物医学设备领域与无线充电相关的主要挑战。这与EPSRC在工程和医疗保健技术战略主题下的电力电子研究领域一致。最初的研究将侧重于评估起搏器用户的健康和安全风险，旨在证明现有感应电力传输系统与ICNIRP 1998和BSI 60601/45502中规定的排放限值的兼容性。与其他无线电力传输系统最显著的区别之一是在靠近接收器线圈的金属体的存在。这影响了无线电源链路优化的多种设计选择，从优化线圈几何形状以实现两个线圈的最大耦合到质量因子的优化。由于起搏器本体，接收器线圈的等效质量因子降低，这意味着需要以更高的频率运行，以使链路效率达到合理的值；这导致了在ISM频段兆赫范围内运行的无线电源系统的发展，主要集中在6.78 MHz， 13.56 MHz和27.12 MHz。小线圈在体内位置的不确定性和周围有机物质的存在会导致耦合系数的显著降低。这一方面不仅与效率损失有关，而且还会影响发射机侧的正确工作。由于耦合因子可能有很大的变化，因此会对初级侧的反射阻抗产生重大影响，从而导致调谐问题。我们的目标是研究同步整流作为该问题的潜在解决方案，本质上是复制具有门开关信号的DC-AC逆变器架构，其从发射机侧持续运行90度相移。其中一个主要的挑战在于高频同步系统的实际实现，该系统能够产生高精度的门信号，最大限度地减少潜在相位不匹配造成的损失。博士研究项目的这一特定方面具有很高的潜力和多功能性，可以在广泛的低耦合系统中找到应用。这项技术不仅易于转移，而且还可以通过相位控制，任意切换系统两侧从发射器到接收器的工作模式，为高频双向无线充电提供一个有趣的起点。考虑到无线电源的广泛应用和可优化的方面，我相信这项研究有可能为现有和新兴技术的增强提供新的和有趣的结果。

The daily demand of a technology-driven society, focused on innovation and continuous re-invention of almost every product we use in our daily life has led to the tremendous amount of progress we have experienced in the last century. We have continuously shifted, year after year, from a product that was considered "perfect" to something even better. From landline, to mobile phones, to portable computers, everything keeps changing and evolving. With this continuous technological progress driven by demand, wireless power has recently become one of the most urgent needs in many applications, ranging from automotive to consumers electronic, also covering sectors such as military and healthcare.The starting point of this PhD project aims to tackle the main challenges associated with Wireless Power Charging in the field of Implantable Biomedical Devices.This is in line with the EPSRC research area of Power Electronics, under the strategic themes of Engineering and Healthcare Technologies.The initial research will focus on assessment of health and safety risks for Pacemaker users, aiming to prove compatibility of existing inductive power transfer systems with the emissions limits stated in ICNIRP 1998 and BSI 60601/45502.One of the most significant differences from other Wireless Power Transfer systems is the presence of a metallic body in close proximity of the receiver coil. This affects multiple design choices for the optimization of wireless power links, ranging from optimal coil geometry for maximum coupling of the two coils to quality factor's optimization. A reduction of the equivalent quality factor of the receiver coil due to the pacemaker body implies the need of operating at a higher frequency to bring the link efficiency to reasonable values; this leads to the development of Wireless Power system that operate in the ISM band Mega-Hertz range, focusing mainly on 6.78 MHz, 13.56 MHz and 27.12 MHz.The uncertainty in the position of a small coil inside the body and the presence of surrounding organic material can lead to a significant decrease in coupling factor. This aspect is not only relevant in terms of efficiency loss, but can also affects correct operation of the transmitter side. Because of the potentially big variation in coupling factor, there will be a significant effect on reflected impedance to the primary side, leading to tuning issues. We aim to investigate synchronous rectification as a potential solution to this issue, essentially replicating a DC-AC inverter architecture with a gate-switching signal constantly operating with a 90 degrees phase shift from the transmitter's side. One of the main challenges of this lays in the practical implementation of a high frequency synchronization system that is capable to produce a high-precision gate signal, minimizing losses from potential phase mismatches.This specific aspect of the PhD research project has a high potential and versatility, finding applications in a wide range of low-coupling systems. Not only this technology is easily transferable, but it could also be an interesting starting point for high frequency bidirectional wireless power charging through phase control, arbitrarily switching the operating mode of either of the two sides of the system from transmitter to receiver.Given the wide amount of applications and optimizable aspects in the discussed topics of wireless power, I believe this research has the potential of offering new and interesting results for the enhancement of both pre-existing and emerging technologies.