The Design Of LED Driver Based On BUCK For Automobile

In recent years,high power light-emitting-diode(LED)with its high light efficiency,low energy consumption,long service life,fast response performance advantages,leads to an LED lighting field an unprecedented revolution.LED driver circuit determines the brightness of LED lights,service life,system conversion efficiency and stability,and becomes the research hot spot.In the essay,the designed LED circuit apply pulse duration modulation under a fixed frequency,with Current peak value detect module,which is applicable to automobile lighting,could work efficiently from the temperature-40~125 ?,under the 8~42V input voltage,and it has high conversion efficiency and high precision of output current.First,using band gap principle create bias current,designed a regulating circuit in advance with negative feedback,makes the input power supply voltage range of regulating circuit in advance is8~42V,to provide stable working voltage for benchmark source circuit and linear regulator.It makes sure the LED driver can work normally at 8~42V of the input voltage range.Then,using since the sharing biased source gate current mirror structure.According to the NMOS tube's different electrical conductivity of the threshold area,the linear zone and saturated zone,create positive temperature coefficient current.According to the poly silicon high resistance and N-well resistor package series resistance.It can replace the linear zone NMOS tube,and create negative temperature coefficient current complement for positive temperature coefficient current.Designed a novel summation type CMOS reference current source with high precision and low temperature drift,to provide lower bias current,and reduce the power of LED driver control circuit,and improve the conversion efficiency of LED driver.Last,using Pre suppression circuit get more stable for regulating circuit output voltage.According to MOS tube's temperature characteristic at the threshold area,designed a benchmark voltage source with high voltage rejection ratio and high precision.It provides high precision of the reference voltage and improves the precision of output current.The schematic diagram designing and pre-simulation was applied by Cadence device.Ofwhich,the LED circuit is with 8-42 v input voltage,drive1-9 diodes,the output current is400 m A,the highest transfer efficiency is up to 97.7%.The highest output current accuracy is0.78%.In which,the input voltage is higher than 36 v,drive 6-9 diodes,the output current is400 m A,the lowest transfer efficiency could also up to 92.9%in the simulation.In the power supply voltage is 40 V,driver 9 LEDs,the output current is 400 mA,the LED driver system conversion efficiency was 95.8%,the output current precision is 1.75%.Then,completed LED driver current the overall layout design and post-simulation,layout area of925.3×826.8?m2,the consequence of post-simulation is almost the same with the consequence of pro-simulation.The simulation show that the design of the low current reference current source and high precision reference voltage source effectively improve the system conversion efficiency and the precision of output current.