Research On The Trajectory Control Of Full-bridge LLC Converter

With the emerging and fast development of Internet of artificial intelligence technology and 5G technology,the amount of data center and communication base station are increasing rapidly.The high efficiency and high reliability power supply architectures are one of the key technologies for these applicationsThe LLC resonant converter is widely used in telecom power supply and server power supply for its soft switching characteristic,high efficiency and low electrical stress,which converts the high DC input(400V)to a low DC bus with galvanic isolation.The commercial LLC controllers usually adopt pulse frequency modulation(PFM)for output regulation.There are still some issues for a Full-Bridge LLC converter which includes:the current overshoot during start-up with high input voltage;the slow response during load transient and the low efficiency during light load condition.To decrease the current overshoot during start-up period,the dissertation derivates a constant resonant current start-up method based on the analysis of LLC resonant converter in the state plane,and the impact of parasitic parameters are analyzed.Finally,a new constant current start-up method considering the parasitic parameters is proposed,which features high robustness and almost no current overshoot.To improve the load dynamic response of LLC converter,the one-cycle control is adopted to achieve one-step response for LLC converter.To solve the problems in light load condition,an adaptive constant frequency burst control strategy is proposed in this dissertation.The burst frequency is adaptive selected according to the load condition to keep it to an insensitive frequency for human.The light load efficiency is also improved.The experimental results from an 1kW prototype verifies the effectiveness of the proposed control methods.