Cauer Circuit-based Equivalent Model for Transformers in LLC Resonant Converters

Abstract:
LLC resonant converters have been widely used as power converters owing to their high efficiency. The conventional equivalent circuits cannot accurately evaluate the transformer losses in LLC resonant converters since they consider only the resistance and inductance within a single frequency. This paper presents an equivalent circuit based on a Cauer circuit to accurately evaluate the transformer losses in LLC converters. The proposed circuit exhibits frequency-dependent impedance characteristics and is integrated into a converter for comparison with the conventional circuits. The efficiency measurements indicate that the proposed circuit achieves a more accurate loss estimation, which closely concurs with the measured values, whereas conventional circuits tend to overestimate the efficiency. This demonstrates the effectiveness of the proposed equivalent circuit in performing a precise loss distribution analysis, making it a valuable tool for improving the accuracy and efficiency of LLC converter designs.