Design Of A High Power Factor And Constant Current Driving Chip For LED

Since the 21 st century,the process of industrialization and urbanization has been accelerating,and the problems of natural energy shortage and environmental pollution have become more and more serious.As a result,led,a green and environment-friendly lighting technology,has attracted extensive attention,and led driving technology applied to lighting system has made great progress.This paper studies the system architecture design and key technologies of high power factor led constant current drive chip,aiming at completing the design of primary feedback constant current drive chip which can provide high power factor,complete protection mechanism and low cost.Based on the analysis of led lighting principle,existing driving technology and power factor correction technology,this paper proposes a high power factor led constant current driving chip.After analyzing the shortcomings of the traditional led driving scheme with secondary feedback plus optocoupler,the primary feedback structure without optocoupler was chosen,which not only greatly reduced the circuit cost,but also made the circuit structure more excellent in constant current accuracy than that with secondary feedback plus optocoupler.Then this paper analyzes the factors that affect the accuracy of constant current,and designs a reasonable demagnetization detection module according to these factors.In addition,aiming at the problem of harmonic interference in led drive circuits,this paper proposes a single-stage active power factor correction scheme based on multiplier structure and peak current control mode.compared with the traditional passive power factor correction scheme,the power factor correction scheme proposed in this paper does not need large capacitance and inductance,so the circuit volume is greatly reduced,and the power factor correction performance is even better.On this basis,this paper also designed modules such as over-temperature protection and over-voltage protection to improve the reliability of the chip.Based on csmc 0.5 um BCD process,the high power factor and high precision primary feedback constant current driver chip designed in this paper is simulated with cadence hspiced tool,and the power supply voltage is 85 v ~ 265 v AC.The chip output current adjustment rate is less than 3.7 %,pf values are greater than 0.92,the total harmonic distortion is less than 24 %,and the system conversion efficiency is more than 82 %.The theory mentioned in this paper is of great significance to the research of constant current drive chip.the design and implementation of high power factor and high precision constant current drive chip based on primary feedback technology also has important commercial value and broad application prospect.