Control Strategy for Half-Bridge Secondary LC Resonant Converter

In this paper, a half-bridge secondary LC resonant converter with the fixed on-time modulation (FTM) method as a step-down converter is proposed. When operating above the resonant frequency, the half-bridge secondary LC resonant converter can achieve full-range regulation within 2X frequency range and the voltage gain is independent of the load variations. Meantime, with the FTM method, zero-current switching turned off is achieved for all diodes while zero-voltage switching turned on is realized for all switches. The working principle, voltage gain and component stress of the half-bridge secondary LC resonant converter are discussed in detail. Moreover, the comparisons are done to show the advantages of the half-bridge primary LC resonant converter and secondary LC resonant converter respectively under different turns ratio. The simulation results are given to validate the theoretical analysis of the converter.