RMS Current based Automated Optimal Design Tool for LLC Resonant Converters

LLC resonant converters are used in renewable energy applications to achieve high power efficiency conversions between different energy sources, buses, and energy storage elements. The traditional design methods for LLC resonant converters are based on the simple frequency domain analysis (FDA). However, the accuracy of FDA is not satisfactory, especially at wide voltage range applications. Considering the flexible power control requirements for photovoltaic systems, a wide voltage range operation is desired for the DC/DC converter. To overcome the drawbacks of traditional FDA method in wide range applications, the time domain analysis is adopted to achieve accurate analysis of LLC converters in this paper. Efficiency is normally selected as the optimization objective, where the circuit components and an accurate power loss model are required beforehand. To achieve a more general optimal design method for LLC converters, a simple root-mean-square (RMS) current and time domain analysis based optimal design method is proposed. The optimal design is achieved by minimizing the converter RMS current and ensuring some key design considerations. Moreover, an automated design tool for the proposed method is developed. Finally, a 2.5 kW experimental prototype is built with the estimated optimal circuit parameters. Experimental results under different operating conditions are demonstrated and the results are consistent with the theoretical analysis.