High Efficiency Dual-Output LLC Resonant Converter with Synchronous Rectifier Control

A new dual-output converter with synchronous rectifier control is proposed. The main output of the proposed converter is regulated by pulse frequency modulation, similar to the standard LLC resonant converter. The auxiliary output is controlled by using synchronous rectifier (SR) control. The auxiliary output can be regulated by adjusting the overlapping duty ratio of SR, and the operation is similar to the boost converter under discontinuous conduction mode. The proposed converter can regulate the dual-output with multi-winding single transformer, and the feedback circuit for the auxiliary output is composed of simple analog circuit. Also, the proposed converter can achieve zero-voltage switching operation of SRs. Therefore, the proposed converter can obtain high power density and efficiency with tight regulation. Performance of the proposed converter is verified with an output1= 13 V/ 6.3 A and output2 = 65-83 V/ 2.25 A prototype.