This study investigates the exploitation of MOSFET-based AC switches in capacitive impedance matching networks (IMNs) for inductive wireless power transfer (WPT). The IMN optimum capacitance has been chosen for a 200 kHz resonant frequency. The activation of the 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 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.

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This paper investigates the development of a passive elliptical planar coil for extending the horizontal transmission distance in an inductive transmitter-receiver wireless-power transfer system (WPT). The passive base coil partially overlaps the transmitter coil and extends the horizontal wireless link between the transmitter and receiver. The base coil models investigated are divided into three categories based on their length. Moreover, for each length category, the optimum number of turns is determined. All proposed models are analysed through the electromagnetic simulation (EMF) software Ansys-Maxwell and Simplorer as well as validated experimentally. For the entire analysis, the maximum efficiency principle is followed in this system. Therefore, impedance matching networks are used across all three terminals in order to tune the system to the operating frequency of 200 kHz to achieve maximum efficiency. The maximum achievable efficiency is determined for each coil prototype (in both simulation and experiment) and the results are compared. The extent to which the EMF software is a valuable tool in developing a planar passive base for an inductive WPT system is discussed. Overall, the proposed concept behind the passive base coil is proved to be successful in extending the horizontal distance between the transmitter and receiver.