Improved wireless power transfer system utilizing a rectifier with nonlinear resistance compression characteristic

Owing to its reliability, flexibility and security, wireless power transfer (WPT) technology has been paid more and more attention to promote the popularity of electric vehicles. However, for the WPT system utilizing a bridge rectifier, when the load changes greatly, the coil coupling efficiency will decrease rapidly, and the power transmitted to the secondary side is insufficient under light load conditions. To address these vital problems, the bridge rectifier with a parallel inductance-capacitor network is proposed in this paper. Due to the nonlinear impedance transformation characteristics of the proposed rectifier, when the DC load changes, the variation range of the equivalent AC impedance can be suppressed at a proper range to improve the coil coupling effi-ciency. On the other hand, the equivalent AC load can be increased to enhance the power output capability under light load conditions. Moreover, there is no additional imaginary impedance introduced during the impedance transformation process, which guarantees the realization of soft switching within a wide load range. At the same time, the network parameters optimization is carried out based on an average efficiency algorithm. Finally, a WPT system with the proposed rectifier is built to verify the electric performance of the proposed structure. And the experimental results meet well with the theoretical analysis.