Technology Research Of 40W Dimmable LED Driver

With the problems of the energy crisis and environmental pollution becoming increasinglyserious, LED as a green light, was payed more and more attention by its characteristics ofenergy-saving, environmental protection, high reliability, etc.,and will replace traditional lightingdevices to become the fourth generation light source.Due to the optical and electrical properties ofits own,LED needs a dedicated drive power to drive it.LED was needed to research and design aLED drive power with a high efficiency, high reliability to match the advantages of LED lightsource for energy saving, long life, high reliability and others. Currently, in order to more efficientlyachieve energy saving, dimmable LED drivers have become a major research field of LED lighting.The characteristics of the LED drive power and the drive programs was described,and thedevelopment status of the dimmable LED driver are discussed in this article.The key technologiesinvolved in the LED driver are also researched,such as dimming, power factor correction ,single-stage PFC flyback converter,step-down constant-current converter , EMC and other keytechnologies.Based on above technologies,a 40W dimmable LED driver was designer. In order toobtain high power factor and reduce costs, two-stage converter program was used:AC/DC stage and DC/DC converter stage. AC/DC stage was accomplished with single-stage PFC flyback converterto achieve power factor correction, and generates a constant voltage as the input voltage of DC/DCstage.DC/DC stage was accomplished with buck topology to achieve constant current for LEDdriving,and provides PWM dimming interface to achieve PWM dimming.At first, A comparativeanalysis of the advantages and application for three kind of dimming program, which include SCRdimming, analog dimming, PWM dimming dimming,was made, and then the PWM dimming wasproposed.Secondly,the fundamental and the key parameters of single-stage PFC flybackconstant-voltage circuit and step-down constant-current circuit were analyzed.Finally, consideringthe EMC design of LED driver,the causes of electromagnetic interference was analyzed,and thesuppression measures for electromagnetic interference was provided,while the surge current, peakvoltage suppression measures was also taken.At the end,the sample of 40W PWM dimmable LED driver was tested,while the performanceand the waveforms of key points were collected and analyzed.The test results show that the LEDdriver has many advantages, such as high power factor more than 0.9 and efficiency more than86.5%, 0%-100%’s dimming range, very small load regulation, and which can work stable.