Research On LED Photo-electro Properties And The Drive Control Strategy

LED is one of the fourth generation of electric light sources,which is a typical energy saving,green environmental lighting source.LED lighting technology is a multidisciplinary technology,because it involves semiconductor physics,optics,electronics,thermology and so on.In this paper,the development of LED lighting technology and its research significance are elaborated.The characteristics of LED and the relationship among them are introduced in the thesis,which include the properties of electricity,optics and heat.In this thesis,The study of a novelty single-stage PFC circuit and its new control strategy is also introduced.Based on the existing photo-electro-thermal theory,the LED thermal network model is established and the function between the junction temperature of LED and the ambient temperature is proposed.Through the Taylor Series Expansion,there is a linear relationship between the input power and the forward current of LED approximately,when the forward current is limited in a specific range.At the same time,the expressions of the heating coefficient and the luminous efficacy are both deduced.Based on the above deductions,the photo-electro-thermal LED model with the two variables,the forward current and the ambient temperature has been established.Based on bivariate LED photo-electro-thermal model,the relationship between the forward voltage and the temperature of the LED chip is studied,and the heating coefficient model on the forward voltage and the temperature is established.On the foundation of the deductions above,the bivariate photo-electro LED model,whose variables are forward voltage and forward current,is derived.The study involves a single LED chip modeling and multiple LED chips modeling,and there is a good agreement between the experiment and the modelBased on the proposed bivariate LED photo-electro model,a constant flux control strategy is proposed after the analysis of the constant current control.Both the impactions of forward current and junction temperature to the luminous flux are studied.To keep the luminous flux constant,the voltage value of LED chip should be sampled firstly,then,the current value will be changed as the bivariate LED photo-electro model.The results of Simulation and experiment show that the control of the constant luminous flux strategy is more effective than that of the constant current strategy.Finally,a buck and dual flyback integrated leakage inductance energy feedback single-stage PFC circuit is presented in this thesis,and the detailed analysis and deduction of this topology have been introduced.At the same time,there is an experiment comparision between the dual switch flyback circuit with leakage inductance feedback and the traditional dual flyback circuit.The experiment results show thatWhen the input voltage is 220V,at the full load,the efficiency of leakage inductance energy feedback of dual switch flyback circuit is 87.6%,and the efficiency of the conventional dual switch flyback circuit is 85.7%.