Elimination Of Electrolytic Capacitors In LED Driver Based On Single-stage PFC Fly-back

With the continuous consumption of the earth's resources,as well as the increasing pollution,in the context of increasing productivity of science and technology,people pay more and more attentions to environmental protection,energy saving,low carbon.Light emitting diode(LED)as a solid light emitting element,due to the advantages of its green environmental protection,high luminous efficiency,long service life,less power consumption has been elected as the fourth generation light source in the world,so it has been widely used.LED as a low voltage high current driving PN junction light-emitting cold light source,photoelectric characteristics decide it needs special driving power supply circuit to supply power to it.In this thesis,LED drive power supply is researched,the work mainly includes:(1)through the analysis of the existing DC/DC power conversion technology and PFC technology,the single stage PFC fly-back is chosen as the topology of the LED drive power supply in this thesis;(2)A single stage PFC fly-back LED driver power supply based on L6562 is design,its rated output power is 25 W,the output current is constant current 900 mA,and the design process of each part of the drive power supply and the selection of components are described in detail;(3)The single stage PFC fly-back LED driver power supply output ripple contains 100 Hz low frequency ripple,a high capacity electrolytic capacitor is needed to get better ripple suppression effect,but high capacity electrolytic capacitors will result in decreased reliability of drive power,for which a new type of filter circuit is used.This filter circuit utilizing electromagnetic induction principle,realizing no electrolytic capacitor in the drive power.And the new filter circuit is simulated and analyzed in Saber power electronic simulation software,the results show that the new filter circuit is feasible;(4)In order to achieve the purpose of energy saving,the dimming circuit is designed in the LED drive power supply.The dimming circuit is using PWM dimming mode,including the control circuit module and drive circuit module two parts,LED can be achieved manual and automatic dimming;(5)A LED driving power supply with dimming function and no high electrolytic capacitor is fabricated and tested,the test results show that the single stage PFC fly-back LED drive power with novel transfer method ripple cancellation circuit can eliminate output ripple current in the main circuit,make the output current is constant.And the PF of the drive power is greater than 0.92 and the power efficiency is greater than 83%,the design requirements are met.Finally,the dimming function of the driving power is tested,the test results show that the dimming effect is good.