Flyback Switching Power Supply Design And Conducted EMI Suppression

In the era of rapid development of science and technology,power supply plays a key role and is an essential part of ensuring reliable and stable operation of electrical devices.Among them,the switching power supply is favored for its outstanding advantages such as high efficiency,small size,light weight and energy saving.and it is suitable for the environment of environmental protection and energy saving in today's society,so it has been widely used.However,with the increase of switching frequency of switching power supply,electromagnetic interference(EMI)has become a problem that must be paid attention to.Among them,conducted EMI is particularly prominent.Therefore,how to suppress electromagnetic interference(especially conducted EMI)has become a hot topic.Firstly,this paper introduces several commonly used topological structures of the switching power supply.Through analysis and comparison,the flyback converter is selected as the switching power supply topology,and the power PWM control circuit selects the current control mode.Secondly,based on the characteristics of the flyback converter,a four-way output flyback switching power supply is designed based on the control chip UC3842.The internal structure of UC3842 is briefly described.The design of its peripheral circuits and other sub-circuits of the system is introduced in detail.and briefly explained the working process of the system,based on this,the overall schematic diagram of the system circuit was drawn using Altium Designer software,and the PCB design was carried out.And then the causes and mechanisms of electromagnetic interference of switching power supply are analyzed.Several common methods for suppressing conducted EMI are introduced.The basic design principles and parameter settings of EMI power filter are expounded.The differential mode common mode combined EMI filter is designed in detail.To suppress the conducted EMI generated in the power grid,thereby improving the electromagnetic interference resistance of the power supply.Finally,the Saber software is used to model and simulate the designed switching power supply.The functional test experiment of the final prototype was carried out,and the measurement data after the test experiment was analyzed.It is verified by experimental data that all the parameters of the designed switching power supply meet the requirements,and the output can be stable,and good performance.