LED Drive Mode And Core Algorithm

Characteristics of LED including long service lifetime, high photo-electricityefficiency, fast response speed, strong anti-vibration capability, energy saving,eco-friendly and so on, make it become the focus of research and application in presentlighting field. But heavy luminance decrease produced by the variation ofOperating-Junction-Temperature (Tj) makes LED lighting generalization slow downand one of the main solutions to this problem is to improve the drive efficiency. So it isthe key for LED research and application to design out the drive mode which can matchwith the LED self-properties and reduce its Tj simultaneously.This article combines LED characteristics with its drive modes. In condition of novariation of the performance indicators such as luminous intensity, color temperatureand so on, the Self-Adaptive Pulse Current Control (SAPCC) drive mode which canreduce LED Tj and improve the utilization rate of electrical energy is proposed and themodel of the corresponding self-adaptive fuzzy PID controller is designed. Details areas follows:(1) Analyze the domestic and overseas research status of LED drive, includingLED development history, characteristics, classifications, application and prospects;make analysis of the present application and technology situation of LED drive, and itsexisting problems; summarize the development tendency of LED drive.(2) Begin with LED semi-conducting properties; research its emitting principle andreasons of the luminance decrease; analyze its I-V, I-V-L, I-V-T, and service lifetimeequations; expound LED electrical, lighting and thermal properties and primaryparameters; Summarize several kinds of present representative LED drive circuits,including goals and principles of LED drive design, the drive classifications, and typicalLED constant current drive circuits.(3) Analyze LED self-characteristics in different drive modes; targeted with theoperating illumination intensity, the SAPCC drive mode is proposed based on the PWMtechnology; the overall structure is designed; the key parameters are analyzed; and theimplementation scheme is made out.(4) Make1W white LED as the research object, set up the experimental platform,conduct the constant current and PWM drive experiments, verify the relationshipbetween drive parameters and working characteristics in experiments is consistent withthe theoretical analysis; make1W white LED and the drive circuit as a generalized controlled object, utilize the experimental data of PWM drive, establish themathematical model of the system in which duty-ratio is the input and light intensity isthe output, verify the accuracy of the established model.(5) Based on the PID control technology, aimed at the properties of the SAPCCdrive mode and established mathematical model, the conventional and self-adaptivefuzzy PID control model are designed in Simulink environment of MATLAB accordingto the systematical properties, and the system simulation is conducted.The simulation results illustrate that the self-adaptive fuzzy PID control model canrealize that the input duty-ratio of the SAPCC system is self-adaptively adjusted and theoutput light intensity keeps at the set value. Compared with the conventional PIDcontrol model, the self-adaptive fuzzy PID control model has faster response speed,higher steady-state performance, and stronger anti-jamming capability; furthermore ithas certain intellectualized function.Innovations of this article includes:(1) propose the Self-Adaptive Pulse CurrentControl drive mode;(2) Design the self-adaptive fuzzy PID control model based on theSAPCC drive mode.