Research On Power Supply For Tunnel Lighting Of Character-free Electrolytic Capacitor

The service life of a tunnel lighting lamp,that is LED,is about 10 years,while the traditional LED driver’s life using electrolytic capacitors is usually less than 5 years.The difference in the service life between them causes an increase in lighting costs.At the same time,traditional control methods have the problems of large volume and high complexity.According to the above two problems,the main contents of this paper are as follows in combination with the actual working conditions of tunnel lighting:Firstly,in view of the short life of electrolytic capacitors,the advantages and disadvantages of different power supply structures are analyzed.Combined with the characteristics of large usage,low cost and long life of the tunnel lighting power supply,a novel long-life LED driver structure controled by digital controller is designed to reduce the capacity of the power balance capacitor through theoretical calculations,the structure model of the power supply is established and the output characteristics of the stability,power factor and response speed of the power supply under different output power conditions are obtained by simulation.The results show that the required capacitance value is greatly reduced under the stable operation of the power supply and the required capacitance value of novel LED driver is declined drastically under the stable operation.Secondly,the control circuit,measurement circuit,constant current control circuit and drive circuit with stm32f407vet6 as the control core are designed.The parameters of circuit components are calculated and the corresponding components are selected and the AP method is used to design the high frequency transformer for power supply,and the magnetic field distribution of the transformer under stable working condition is analyzed;The control system with PI control as the main closed-loop control algorithm is designed,including the functions of measurement,constant current control and start-up buffer.Finally,the overall schematic diagram and PCB of the power supply are designed by using Altium designer,and the prototype of the power supply is completed;The input power factor,output efficiency and output current ripple rate of the power supply under different loads are tested;Compared with the simulation results,the variation of input power factor,output efficiency and output current ripple rate under different loads are analyzed.