The Modified FHA and Simplified Time-doamin Analysis methodologies for LLC Resonant Converter

This paper proposed two modified analysis methodologies based on the fundamental harmonics approximation (FHA) and Simplified Time Domain Analysis (STDA). The equivalent output resistance of resonant tank in discontinuous conduction mode (DCM) is derived, and this modified FHA (MFHA) shows more accuracy than FHA in DCM, especially when the working frequency is far away from series resonant frequency. In the meantime, the modified STDA (MSTDA) is proposed based on MFHA and STDA, which is also more accurate as the working frequency is close to the series resonant frequency. Finally, a prototype was built according to the proposed parameter design process and the two modified analysis methodologies were validated to be more accurate than FHA compared with the experiment results.