Soft-switching failure analysis and countermeasures for synchronous rectification of CLLC converter
Synchronous rectification ( SR) is an effective method to improve the operational efficiency of CLLC resonant converters,However,due to factors such as parasitic capacitance of power transistors,there is a risk of soft-switching failure in SR.To achieve both SR and soft-switching simultaneously,based on uncontrolled rectification on the secondary of the converter,the failure reasons of the SR soft-switching under different operating states were analyzed,as well as the effective range of soft-switching implementation.A digital control method for SR under different operating states was proposed,which can improve the operating range of SR while ensuring the implementation of SR soft-switching,thereby ensu-ring the operating efficiency of the converter in different operating states.At the same time,the calcula-tion method for the ON and OFF times of SR under different operating states was improved,so that the control of SR does not require the participation of current sensors and other additional hardware circuits,and can be applied to bidirectional CLLC resonant converters that originally did not have SR control relat-ed hardware.An experimental platform was built to verify effectiveness of the proposed method.