Llc Resonant Full-bridge Parallel Current Switching Power Supply

With the development of soft-switching and current sharing, large capacity and high-frequency power supplies have become an important research field of power electronics. To meet the requirements of large capacity power supply on performance, weight, size, efficiency and reliability, this thesis mainly researches on main circuit structure of high efficiency and the control of paralleling current sharing, then develops an electric locomotive intelligent charger system.The large capacity battery charger, used by AC driving electric locomotive, is required high-efficiency with more than 90 percents. It is impossible to satisfy this requirement by using hard-switching technique. According to characteristic of large capacity and high-efficiency, a novel full-bridge named LLC resonant converter is adopted to design this power supply. The focus and difficulties of using this converter are the selection of the parameters of resonant components. Through detailed analysis on properties of frequency, short-circuit and no-load, a method on designing the parameters of LLC full bridge resonant converter based on an equivalent linear model is proposed in this thesis.This charger with 5 power modules paralleled together, can output 150 Ampere current, each with 30 Ampere current. Firstly,based on design requirements, the components parameters are selected and the correctness of these parameters is checked by simulation using a soft-ware named SABER; then the design of other parameters in the main circuit of the entire power module is achieved; Besides, a common PWM control IC named SG2525 is used as the control center to realize PFM control. By working on ZVS (Zero-Voltage Switch) soft-switching and high-frequency state, the aim of high conversion efficiency and smaller size of the power module has been achieved.Through the analysis of several current sharing methods and parallel circuit, master-slave current sharing method is used based on CAN bus,which improves the anti-interference ability of the system.Then a monitoring module is designed to monitor the power modules and the overall output. The design of CAN bus interface and man-machine interface makes the power system more intelligent and practical.Accordingly, it is succeed to parallel all the power modules together.Finally, experiment results of the power modules and the parallel operation of the power system are provided, which prove the correctness of the theory and the rationality of the design methods.