The Design Of Piecewise Linear LED Driver

LED(Light Emitting Diode) is known to be the fourth generation light sourse due to its energy-saving environmental protection high efficiecy and long life. LED driver has made rapid and great development because it’s one of the most important parts of the LED products.A piecewise constant current LED driver is designed in this paper.The piecewise constant current LED driver is completed with high effciency,high power factor and simple extranal circuit by improving the traditional linear constant current LED driver and avoiding electrolytic capacitors for its high cost,large footprint and low reliability.Following aspects are included in my paper:1.The basic principle of LEDs’ and LED drivers’.The architecture of the piecewise linear constant current is proposed and the theoreticak derivation is done.2.The modules of the piecewise linear constant current LED driver chip’s is designed and simulated by using the Cadence Spectre in order to make each module wrok in accordance with expectations.Modules in the paper include bandgape reference module,power module,PWM dimming module,analog dimming module,over temperature module,over voltage module,LDMOS driver module,the bias voltage module and so on.The specific circuit implementations of all the modules are given.What’s more,some modules describles the mainstream implementations and other implementations.Finally all the modules are tested by Cadence Spectre simulations.3.The simulation of the all the circuit in the piecewise linear constant LED drver integreted chip. After the completion of the design and simulation of each module in the piece wise linear constant current LED driver chip,the overall circuit is simulated. The protection function and dimming function is also verified,which includes over temperature shutdonw protection, analog dimming,PWM dimming,tempeature compesation,over voltage protection.The simulation results of this chip is compatible with AC 220 V,AC 110 V.The maximum current of LEDs is 36 mA and the maximum regulation current of overtemperature module is 19 mA.When the voltage amplitude ranges within 20%,the overvoltage protection makes the maximum current 25.91 mA.