The Study Of LED Navigation Constant Current Power System

Airport lighting system had the important security for pilot landing and taking off in the evening,and the core of airport lighting system is constant current dimming system.At present,the silicon controlled rectifier and the AC-DC-AC dimming was used most in Chinese airport,because the silicon controlled rectifier and power diode were used in the system.Current of the AC side in system was distortion and led to harmonic pollution.Using LC filter will cause difficulty of the big volume filter to design.What's more,incandsecent lamp were used the most in lighting load in airport.The luminous efficiency and environment issue was not as good as LED.With the development of power electronics;new energy technology,it was possible for researching the high quality LED dimming power system,by the background of navigation LED constant current dimming system in this paper,the topology and control method of constant current dimmer and LED driver of navigation system was studied.The first part of paper analyzed the AC-DC-AC dimmer of front-end in navigation LED constant dimming power system,Aiming at disadvantage of the traditional AC-DC-AC dimmer.the non-controlled rectifier in front-end of AC-DC-AC dimmer was replaced by current source rectifier,analyzed the working theory of dimmer based on current source rectifier,and then established the large signal mode in dq coordinate system and the steady state equation was solved.the double closed loop control was used and suitable disturbance eliminating and active damping was added in rectifier part of dimmer also,it can decrease the steady state error and THD in AC side,and analyzed the control loop in DC-AC part of the dimmer.All of the analysis were verified by simulation.The second part of paper introduced theory of LED power based on topology of Boost-PFC and Flyback in the back-end dimming system,by comparing features of CCM and CRM in Boost-PFC,QR and DCM in Flyback,the advantages and disadvantages were found in different power level.and then established the small signal mode in CCM to analyze control loop,At last,all of the Boost-PFC and Flyback were verified by simulation.At last,based on the project,the 75 W LED constant current dimmer of the biggest output power was designed,main work for 75 W LED constant current dimmer were schematic design;PCB design,EMC design by EN55022 Class B,the integrated critical-mode PFC and quasi-resonant current-mode PWM controller FAN6921 MR was used in this project,AP4310 was used for error amplifier,and STC89C52 RC mircocontroller was used for dimming.The biggest current can get to 2.1A,biggest output voltage can get to 36 V.this plan was verified by a 75 W prototype.