Adaptive impedance-matching network for wireless power transfer system with off-center receiver

In this paper a problem of degradation of energy transfer efficiency due to the displacement of the receiver with respect to the transmitter is discussed. The relative position or the distance between the receiving and transmitting resonators affects on their input impedances that is followed by energy loss arising from impedance mismatching. Thus, it was proposed that such negative effect could be compensated using adjustable matching networks in the transmitter. All components of the considered matching circuit are realized as a set of lumped elements switched by transistors. It was demonstrated that such system allows varying the input impedance of the resonator in a wide range. Simulations and experimental investigation were performed for the system, which consists of the transmitting and receiving resonators with 12 mm spacing between them. Energy transfer efficiency was measured for two matching circuits (with constant and tunable components). Particularly it has been shown that the performance of the proposed adaptive impedance-matching network becomes higher alongside with displacement of the receiver and transmitter.