This paper investigates the exploitation of MOSFET based AC switches in capacitive impedance matching networks (IMN) for inductive wireless power transfer (WPT). The IMN optimum capacitance has been chosen for a 200 kHz resonant frequency. The activation of tuning capacitor on the tuning branch is achieved with the use of MOSFET AC switches in order for the WPT system to achieve maximum power transfer efficiency. The MOSFET AC switch is modelled as an internal parasitic resistor and capacitor connected in parallel. A WPT analytical model is developed to study the effects of the MOSFET’s parasitic elements on the WPT system’s efficiency and is verified experimentally. Various MOSFET switches and relays have been implemented as the IMN switching elements and compared when tested under the same conditions. It is concluded that MOSFET AC switches which have low on-resistances and small parasitic capacitances are desirable as they have a smaller impact on the efficiency. Additionally, parasitic capacitances of MOSFET AC switches need careful consideration for different resonant frequencies as they can affect the overall IMN tuning capacitance especially when they are turned off. Comparing to commonly used relay switches, MOSFET based AC switches have similar switching performance but are significantly smaller in size.

中文翻译：

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电感式无线功率传输系统中的电容性阻抗匹配网络中基于MOSFET的交流开关的开发

本文研究了在电容性阻抗匹配网络（IMN）中基于MOSFET的交流开关在电感式无线功率传输（WPT）中的开发。已为200 kHz谐振频率选择了IMN最佳电容。为了使WPT系统获得最大的功率传输效率，可通过使用MOSFET交流开关来激活调谐分支上的调谐电容器。MOSFET交流开关建模为并联的内部寄生电阻器和电容器。开发了一种WPT分析模型来研究MOSFET寄生元件对WPT系统效率的影响，并进行了实验验证。各种MOSFET开关和继电器已实现为IMN开关元件，并在相同条件下进行测试时进行了比较。结论是，具有低导通电阻和小的寄生电容的MOSFET AC开关是可取的，因为它们对效率的影响较小。此外，MOSFET AC开关的寄生电容需要仔细考虑不同的谐振频率，因为它们会影响整个IMN调谐电容，尤其是当它们关断时。与常用的继电器开关相比，基于MOSFET的AC开关具有相似的开关性能，但尺寸明显较小。