Design Of Server Power Supply Based On Digital Half Bridge LLC Resonant Converter

With the advent of the cloud era,the proportion of data center power consumption has increased significantly.In response to the national policy of energy conservation,emission reduction and green double carbon,the construction of green energy data center is an inevitable trend.The power supply quality of the server power supply plays an extremely important role in the stable operation of the data center.At the same time,in order to prevent the impact of power failure on data security,the server power supply needs to have the ability to output normally within a certain holding time.Therefore,it is of theoretical and practical significance to study the server power supply which can take into account the requirements of high efficiency,high power density and certain holding time at the same time.Compared with PWM DC converter,LLC resonant converter can meet the requirements of high efficiency and holding time at the same time.It has become the first choice of DC /DC converter topology in server power supply.Firstly,the working principle of discrete resonant capacitor half bridge LLC converter is analyzed from three modes: under resonance,over resonance and quasi resonance.The modal circuit diagram in one switching cycle under under resonance mode is analyzed in detail,and the working conditions and performance characteristics of each resonance mode are given.The gain function of resonant network is deduced,the coupling relationship of quality factor,unit value of resonant inductance and resonant cavity frequency is analyzed,the parameters of resonant network are optimized,and the theoretical losses of main components such as power switching devices,transformer and resonant inductor are further discussed.Secondly,for the discrete half bridge LLC converter,the advantages and disadvantages of bang bang charge control,charging current control and time shift control(TSC)are compared and analyzed.On this basis,an improved TSC digital control strategy is proposed.At the same time,the LLC circuit model of improved TSC control is built based on PLECS simulation software,verified by simulation,and the simulation results are given.The adaptive synchronous rectification control algorithm is also given to further improve the efficiency of LLC converter.Then,the Boost PFC circuit of the front stage of LLC converter is studied,and its control loop is normalized and control parameters are calculated based on digital average current control.In order to improve the dynamic performance of the converter,a variable bandwidth control method is proposed.The control algorithm has simple structure and is easy to implement in software.Finally,taking stm32g474 as the core controller,a 100 k Hz 1200 W half bridge LLC converter prototype is made.The main circuit,sampling circuit,control circuit and driving circuit of half bridge LLC converter are designed.The state machine flow of LLC resonant converter and the flow of improved TSC control software are compiled.The experimental results verify the good performance of the designed server DC / DC power supply.