Research on the Formation Principle and Suppression Method of Switch Spike Voltage in Reverse LLC Resonant Converter

The bi-directional LLC resonant converter cannot realize the ZCS of the primary side when working in the reverse mode, which will generate a large spike voltage at both ends of the switch tube of the reverse primary side. Combined with the working mode of reverse LLC, this paper explains the causes of reverse spike voltage and oscillation in detail through time domain analysis, and improves the control method of reverse LLC resonant converter to make the resonant current participate in the resonance of the excitation inductor, so as to reduce the turn-off current and suppress the spike voltage and oscillation on both sides of the switch tube. Finally, the effectiveness of the synchronous rectification control strategy is verified by the simulation and experiment of 12V/125A1.5KW reverse LLC.