Research And Design Of LED Driver In Automotive

With the maturity of automotive market, automotive electronic products have been more and more important. This paper has researched and designed one LED driver which is suitable for automotive application. Its supply voltage is25V and working temperature is at range of-40～150℃.This LED driver was designed by using peak-current PWM control mode. The system with PWM control is working at fixed frequency. It is reliable and has simple structure. With peak current detecting, the system is easier to be stable with simple compensation network.There are protecting blocks for over temperature detecting, over current detecting, short output detecting and over voltage detecting. It is suitable for market application. There are also other feature functions:1) frequency selecting function. The frequency of system clock can be set from110kHz to550kHz;2) chip synchronization. You can make differenct chips work at the same frequency;3) dimming function. There are linear dimming and digital dimming. Linear dimming will change the color of LED light while digital dimming not.4) HICCUP protection. It is used to avoid recovering the system by error.5) two output voltages,5.5V and1.8V, which can provide output current of12mA and0.5mA respectively.This design is based on one advanced process, CSMC0.18um25V BCD process. Its shortest channel length is0.18um. It provides both high voltage components which can work at voltage of25V and low voltage comonpents which work at voltage of1.8V.The power MOSFET is not integrated in the chip, so it can be used in Buck, Boost or Buck-Boost. The simulation is based on Boost and the compensation circuit is also outside the chip. All the functions defined in SPEC has been achieved and the effiency of system is also proved to be good, which can reach94.69%.The layout has been finished and the area is1.3×0.8mm2.