Design Of LED Driver With Step Dimming Function Based On Primary-side Feedback Single Stage Flyback

The emergence of the LED lighting brings new innovation to the world lighting market,it has high efficiency,energy saving,long life and other significant characteristics.LED driver supply technology was in continuous improvement also along with the market changes.In power supply design,the miniaturization,low cost,and meet IEC61000-3-2 Class C and the United States energy star lighting standard is the trend of the times.This thesis presents the design and implementation of a step dimming LED power supply which based on primary side regulated flyback AC-DC,the main contents are as follows:(1)This paper introduces the luminescence principle and basic properties of LED light-emitting diodes,the topology of the LED drive power supply and LED dimming methods.Make a comparison between the two levels of PFC and single-stage PFC circuit.Design a new step dimming circuit which used in primary-side feedback single stage flyback topology,that detecting the wall switch signal,and then implement brightness adjustment from 100% to 50% to20%.(2)Mainly analyses the constant current output,quasi-resonant operation mode and high power factor control of primary-side feedback single stage flyback.Aprimary side feedback single stage flyback power supply was designed by using SYPH83 A chip.And introduce high frequency transformer design,power supply circuit design,clamp circuit design,EMI power filter circuit design and key components selection in detail.(3)Utilises a step-dimming control circuit,and do the analysis for that it is compatible with PSR topology.Then introduce the key components selection in detail.(4)Finally,a prototype was developed and passed the relevant test.High power factor,high efficiency,step dimming function and strong pratical value were achieved.