Performance enhancement of multi-resonant high-Q converters using a variable resonator element

Abstract

The basic resonant converters such as SRC, PRC, and SPRC are widely used in high frequency switching converters because of their simple control strategy and efficient soft-switching performance. However, in case of the loosely-coupled contactless power transfer applications, the power stage design requires a multiple resonant (high-order) topology to acquire high-Q for the optimized performance of the converter. However, the characteristic response of the multiple-resonant tank becomes highly sensitive to temperature variations and coil misalignments due to high-Q design (very sharp impedance curve). Therefore, even a small variation in one of the resonant element leads to mismatch in the resonant frequencies of the multi-resonant converter. Because of this reason, the overall efficiency of the converter drops down. The failure of soft switching and presence of significant reactive power loss on the resonant circuits contribute to the additional power loss on the power stage. The effect of resonant mismatch in multiple-resonant converter has been addressed in this paper. As a solution to this problem, this paper proposes a simple and cost-effective variable resonant element for the multiple resonant converters to enhance the overall performance of the system at all operating conditions. The feasibility of the proposed technique has been validated through hardware implementation and the results are compared with conventional approach. The results prove that the proposed variable resonant element can be applied successfully to enhance the performance of the system. © 2017 IEEE.