Novel impedance matching method based on negative resistors for WPT

Abstract

In a wireless power transfer (WPT) system via coupled magnetic resonance, the transmission power and efficiency dramatically decrease with increased in the transfer distance and load variations. In the conventional impedance matching method, different resistors are matched by adjusting passive devices such as capacitors and inductors. The corresponding matching range changes with different topological network structures. In particular, there exists a matching forbidden zone. In this paper, a novel impedance matching method based on a negative resistor is proposed to match the impedance in the forbidden zone. First, the conventional impedance matching network is analyzed based on circuit theory. Then, the feasibility of the proposed method is verified. In addition, the receiving power obtained using the conventional matching method is compared with that obtained using the proposed method. It is theoretically verified that the novel method can break the upper power limit related to the conventional method, which realizes a higher receiving power. A prototype was built in the laboratory. Experimental results show the feasibility of the novel method. Moreover, derived simulation results were basically consistent with the experimental values, which also demonstrates the validity of the proposed method.