Research On High Brightness LED Driver Of Automotive Headlamp

As the fourth generation lighting source, LED has many merits such as large luminous efficiency, long life, fast response and environment protection, etc. It has begun to replace conventional light sources in many applications. LED applied to automotive headlamp will effectively improve its life, efficiency and light quality, it also does good to environment protection and restricts greenhouse effect.First, the paper describes the merits of LED compared to other lighting sources as automotive headlamp and gives an overview of the development of LED and its power supply. Then a spec of the driver of automotive daytime running lights is given, and detailed description of the features of the driver is made. Third, three power supplies are designed respectively based on special IC, general IC, and DSP, and the key circuits are researched and designed. For the special IC scheme, MAX16831 is used to control the Flyback convertor to realize the current constant and PWM dimming of LED, For the general IC scheme, LM5022 is used to control the Boost convertor to realize a similarly high quality driver with low cost. On this basis, the control principle of PWM dimming of common IC is focused on, and the factors of PWM dimming ratio is analysed, and making use of anolog switches in series to the compensation network and soft-start pin is proposed to improve the dimming ratio, and a 10W experimental prototype is made to verify the feasibility of the design. For the DSP scheme, dsPIC30f2020 is used to control the Flyback convertor to realize the driving requirements, and the principles and realization of the quasi-resonant soft-switching of Flyback is focused on to improve the efficiency of the power supply. The current sharing problem of multi-channel LED in parallel is reseached on, and an optimized high efficiency design is proposed. A 10W experimental prototype is made to verify the feasibility of the design. At last, a conclusion is gived.