Research On DC/DC Converter With Wide Input Voltage And High Power Density Based On Magnetic Integration Technology

With the continuous enrichment of electrical equipment in modern life,people have put forward higher requirements for power supply performance.Power electronic converters are required to maintain good stability and performance under wide input voltage conditions in some special applications.For a wide input voltage range of 50-400 V,this thesis summarizes the improved schemes and topologies proposed by scholars at home and abroad,and proposes a two-stage soft switching converter with two-stage phase-shift Boost and half-bridge LLC based on magnetic integration technology.The scheme uses variable modal control to achieve high efficiency and high power density applications under wide input conditions.The working principle of the two-stage converter proposed in this thesis is elaborated in detail.For the pre-stage converter,this thesis deeply analyzes the working mechanism of the pre-stage converter under phase-shift control.In order to ensure the soft switching characteristics,the inductor current ripple is minimized to determine the best operating mode.A more in-depth analysis is performed in this mode,including modal analysis,current ripple analysis,loss analysis,etc.,and the necessary and sufficient conditions for achieving soft switching characteristics are given..The correctness of the theoretical analysis is verified in the simulation experiment.In addition,a brief analysis of the half-bridge LLC resonant converter in the rear stage is introduced,including modal analysis,gain characteristic analysis,etc.,and the influence of the resonance parameters on the characteristics of the LLC resonant converter under wide input conditions is analyzed.It shows that the performance of the converter is difficult to maintain good under too wide input conditions,and it needs to set the pre-stage for pre-regulationBased on theoretical analysis and according to the performance index requirements,the main parameters of the circuit are designed,including the inductance and coupling coefficient of the coupled inductor,the resonant cavity parameters of the latter halfbridge LLC circuit,and the selection of switching devices.Based on the magnetic integration technology,the Max Well simulation software is used to optimize the design of the three-column coupling inductance of the front-stage converter,and the analysis and design of the LLC integrated magnetics of resonance inductance and transformer.According to the above hardware circuit parameters,the theoretical efficiency of the converter is calculated.Further,to achieve good steady-and dynamic characteristics of the system,according to the small-signal model of the dual-phase phase-shift Boost circuit and the half-bridge LLC resonant circuit,the control loops are designed for the pre-stage and post-stage converters,respectively.The closed-loop simulation system model is established in the PLECS simulation software to verify the effectiveness of the controller to the dynamic characteristics of the system.At the same time,a soft switching strategy based on hysteresis interval is also used to realize stable and fast switching of converter modes.Finally,a digital control system based on DSP is designed,and the impact of control delay on system stability is analyzed.The discrete domain simulation analysis is performed on the designed digital controller nn the PLECS to verify the effectiveness of the controller.