Research On Program-Controlled Half Bridge High Power LED Driver Circuit

As a new generation of green light source,LED has been widely used in the field of lighting because of its advantages of environmental,safety,high luminous efficiency and long life.While the LED is widely used,the requirements for the reliability and efficiency of the LED drive power supply are becoming more and more high.At present,improving the switching frequency is an effective way to improve the power density of the driving power,reduce the volume of the driving power and improve the efficiency of the power supply.It is one of the core technologies to reduce switching loss and realize soft switching in high frequency working conditions.Compared with the PWM converter,the LLC resonant converter has the advantages of easy to realize ZVS zero voltage switching on the primary side,and ZCS zero current closure on the secondary side.The excitation inductance and resonant inductor are easy to integrate with the transformer to reduce the volume.It has the advantages of high switching efficiency,high power density,small volume and light weight.Therefore,LLC resonant converter as LED driving power has wide application space.In this paper,the topology of the LLC resonant converter is studied deeply,and a LED drive power supply for the half bridge LLC resonant converter is designed.Firstly,this paper introduces the development status of LED driving power,and selects half bridge LLC resonant converter as the DC/DC transformation part of LED drive circuit.As the research emphasis of this paper,it introduces its main working principle under three working modes.Then,based on the fundamental analysis method(FHA)modeling and analysis of half bridge LLC resonant converter for DC gain formula.Analyzing the impact of various parameters such as quality factor and inductance ratio,get the influence of each parameter on DC gain and the working efficiency.Then the thesis analyzes soft switching conditions.according to the above analysis,parameters of half bridge LLC resonant circuit is obtained,including the design of MOSFET,transformer,resonant capacitor,resonant inductor and so on.The computer simulation software is used to simulate the working state of different input voltage and different load.It is verified that the half bridge LLC resonant converter has correct parameter.It can realize soft switching in full load range.Finally,according to the previous theoretical basis,the control circuit,feedback circuit,rectifier filter circuit and auxiliary power circuit based on NCP1396 were designed.The design of a 100 W half bridge LED drive circuit is completed.Considering the application of some intelligent control fields,Bluetooth remote monitoring module is added to complete the program code design.Bluetooth module is used to realize the control of LED driving circuit by mobile phone,and it can monitor LED remotely.After the completion of the half bridge LED drive circuit,then the thesis test and analyze the experimental results to verify the rationality and correctness of the theoretical analysis.