Efficiency-wise optimal design methodology of LCLC converter for wide input voltage range applications

Abstract

LCLC converter is an LLC-based, four-element resonant topology, which has been proved to achieve high voltage gain and high efficiency. Such trait makes LCLC converter specifically suitable for wide-input-voltage-range DC/DC applications. Currently, LCLC converter lacks a design method targeting at optimal efficiency over a wide input voltage range. In fact, due to the complexity, efficiency itself is seldom used as optimization criterion even for LLC designs. In this paper, a systematic methodology is proposed to optimize the efficiency at different input voltage levels for LCLC converter. Three mathematical programs (developed in MATLAB) are employed respectively to find all resonant parameter combinations that critically achieve the required voltage gain; precisely analyze the current stress in time domain; and comprehensively calculate the losses in the power circuit including magnetic components. The programs will automatically generate the optimal parameter design with highest weighted efficiency at desired input voltage levels, as well as the magnetic components construction with specified types and sizes of core and conductor. Besides, this method can be extended to other topologies for wide voltage range applications. To verify the effectiveness of the proposed optimal design method, the function of the mathematical tools will be carefully explained in this paper; and a step-by-step design will be demonstrated as an example. Simulation will be included to verify the accuracy of the method.