Efficiency Improvement on LLC Resonant Converter Using Integrated LCLC Resonant Transformer

This paper presents the efficiency improvement on the comparative half-bridge LLC resonant converter using the integrated LCLC resonant transformer. The conventional isolated LLC converter demands large leakage inductance to attain high power factor for the resonant tank. However, the large leakage inductance requires more turns of the transformer to sustain sufficient magnetizing inductance. As a result, high number of turns causes more copper loss and lower efficiency for the LLC resonant transformer. In order to reduce the demanded leakage inductance, a resonant capacitor can be connected in parallel to the magnetizing inductor through an auxiliary winding as an LCLC resonant transformer. Finally, the resonant transformer of a commercial 300 W LLC resonant converter is converted as an integrated LCLC resonant transformer with lower leakage inductance for efficiency comparison.