| Electric automobile is a typical case of new energy technology applications. But the question of on-board battery endurance has become an important factor of restricting its development. Along with the development of energy saving technology, LED's outstanding advantage of energy saving is showed in the field of conventional automobile lighting. By utilizing LED, which enjoys the advantages of lower energy consumption and higher light efficiency, as the headlight, the highest energy consumer in electric automobile lighting system, the poor power supply situation of electric automobile can be effectively improved. However, the special power environment of electric automobile cannot directly meet LED's constant current requirement. As a result, LED driver of good design performance, high efficiency and low cost, is the premise and foundation to realize the LED headlight of electric automobile. As an effective driving power, switching converter is widely used in all kinds of fields in the form of constant voltage power source. But due to LED's Optical-Electrical Characteristic, constant current power is needed for driving. As the result, desirable main circuit as well as control mode must be chosen, in order to realize the application of LED on electric automobiles.In this paper, the author selected single-ended primary inductance converter (SEPIC)under CCM condition as the main circuit, and peak current control as the control mode, according to the power supply feature of lithium iron phosphate battery pack, and thus the LED headlight driver of electric automobile constituted. In this paper, the author firstly made an introduction of traditional operation modes of SEPIC circuit, and found the critical operating point of main circuit by which the circuit can be ensured to operating stably under CCM, and then component's voltage and current stress in CCM SEPIC main circuit were analyzed. Secondly, in accordance with SEPIC circuit's feature of peak current control, the author built a small-signal model of current inner-loop by using switch network average model method, and thus the transfer function from control signal to output voltage has been gained. The stability of current inner-loop has then been analyzed, thus the stability condition of current inner-loop was obtained, and the selection principles of main circuit component parameters were confirmed. Then, the current sample collection unit was improved on the account of the constant current requirement of LED driver. Finally, according to the LED model as well as the power supply data of electric automobile lithium iron phosphate battery pack provided by the manufacturer, the simulation on designed LED driver was completed by Saber software.On the basis of theoretical analysis and simulation, the experimental sample of driver was made. In the end of paper, the design procedure and experimental results were represented, by which the correctness of theoretical analysis has been tested and verified.
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