Control Scheme for LLC Resonant Converter with Improved Performance Under Light Loads and Wide Input-Output Voltage Variation

A novel control scheme to improve the performance of LLC resonant mode controller under light load operation and wide input-output voltage variations is presented in this paper. Poor light load voltage regulation in the LLC resonant converter necessitates the use of burst control mode, which results in performance degradation under light loading conditions. The proposed control scheme uses an adaptive deadband technique that avoids the burst control mode even at extremely light loads resulting in continuous operation and thereby lower output voltage and current ripple, lower noise and higher efficiency. Furthermore, a neural-network-based compensator is proposed in this paper for improving the dynamic performance of the converter under varied operating conditions. Theoretical and simulation results are provided to show the advantages of the proposed control algorithms. A 200W-LLC resonant converter is used for experimental verification of the proposed control scheme.