Mechanism of Current Imbalance in LLC resonant converter with Center Tapped Transformer

In recent years, the LLC resonant converter with a center-tapped transformer has been widely used due to its high power density and high efficiency features in the Factory Automation which requires the low output voltage and high output current. However, the imbalanced secondary current for each half cycle occurs, and it cause a problem of reliability degradation associated with the high current. In this paper, the mechanism of imbalanced current is investigated focusing on the effects of coupling coefficient of the center-tapped transformer. This mechanism has been confirmed by experiments.