Research On The Topology Of Wide-Range Input Voltage Switching Mode Power Supply Based On SiC Power Devices

In recent years,sustained economic growth has promoted the vigorous development of the automobile industry.Electric vehicles have attracted wide attention because they can greatly alleviate the energy crisis and environmental deterioration.Input voltage fluctuations due to the bad working environment of on-board DC/DC converter,so the research of wide-range input voltage on-board DC/DC converter is very important to improve the performance of electric vehicle.LLC resonant converter has the advantages of soft switching,low electromagnetic interference and high power density.However,to achieve wide-range input voltage,the resonant converter needs to operate in a wide switching frequency range.This may lead to the loss of soft-switching characteristics that reduce the conversion efficiency.Based on the above,a high-efficiency resonant converter with wide-range input voltage in narrow switching frequency(0.81-1fo)is planned.By cascading Boost and LLC resonant converters and multiplexing a set of bridge arms,a composite LLC structure is formed.The three control modes of Pulse Frequency Modulation,Phase Shift Modulation and Pulse Width Modulation are combined organically.When the input voltage changes from low to high,the converter adopts Pulse Frequency Modulation,Phase Shift Modulation and Pulse Width Modulation in turn,which solves the problem that the efficiency of the converter is difficult to optimize in the wide-range input voltage under single control mode.In this paper,the principle and characteristics of each modulation mode are analyzed,and the gain of the converter is derived,and the optimal switching point is selected.At the same time,the parameters of passive devices are designed and optimized to reduce the loss and improve the efficiency.Then the loss analysis is carried out to guide the selection of power devices and efficiency optimization.To solve the problem of small signal modeling of LLC resonant converter,this paper uses the equivalent circuit diagram and Laplace transform to model the small signal of LLC resonant converter,and verifies the accuracy of modeling through Saber and SIMPLIS simulation platform.To meet the demand of high power density,and reduce the peripheral components of the chip,this paper designs a control chip suitable for wide-range input voltage,which integrates the module of Pulse Frequency Modulation,Phase Shift Modulation and burst mode.The design is verified by virtuoso spectre simulation tools,the layout design of the chip is completed,and the parasitic parameters are extracted.The results are consistent with the theory.Then after tape-out,the chip is packaged in COB and the corresponding PCB is designed for circuit testing.Finally,a prototype of input voltage 35-120 V,output 48 V,150W is made and debugged.Simulation and experimental measurement of current and voltage of key nodes in three control modes are completed.Experiments show the feasibility of a hybrid LLC resonant converter and the accuracy of loop small signal modeling.At the same time,the number of power semiconductor devices is reduced,and the resonant frequency is 800 k Hz,higher than that of other literatures,so the prototype has obvious advantages in low cost and power density.