We know, led the luminous intensity and forward current IF is almost a linear relationship, an increase of forward current IF can increase the luminous intensity. However, led a PD value of the maximum power consumption limit, PD = VF × IF (VF is the forward voltage drop), if the earth had more than the maximum increase in PD when IF Er Shi, led overheat damage. In order to enhance the luminous intensity to develop a medium-power led (usually a few hundred mW), its working current of up to 70mA. In recent years, in order to further improve the luminous intensity to develop a high-power led, its power is generally 1-10W (there are also greater than 10W). Its operating current is generally 350-700mA, some up to more than 1A.