Design Of Wide Input-voltage Range And High Accuracy Of Constant Current Control IC Applied In LED Driver

White-light LED, which has more and more varieties of applications due to its advantages of energy saving, environmental protection and high efficiency, is considered as one of the most promising high & new technologies in the 21st century. For this reason, an LED-driving controller with excellent performance is paid more attention to nowadays.Firstly, the white-light LED's characteristics of electricity, optics and temperature are introduced in this paper, and three LED-driver circuits and the mechanism of PWM constant-current modulation are presented as well.Secondly, with the high-voltage BCD process of NUVOTON 0.5um5V40V, a high voltage buck LED-driving controller is designed for a constant LED current with high accuracy based on the Cadence software. This controller can be applied with dc-input in a range of 18V~450V, and can provide with an output current as high as 1A to drive hundreds of small-powering LEDs in serial and parallel in the fields of backlighting LED driver, signal LED lighting and so on.For a constant current with high accuracy in a full range of input, a new peak-current compensation technology is applied through the comparision of sensing current and the technology of PWM constant-current modulation. Additionally, the working frequency of the controller is made to be programmable as well as the function of over-temperature protection. The short-circuit protection and under-voltage protection are also added for the safety and reliability of the controller. Moreover, digital and linear analog light-dimming function is designed to meet its demand in certain applications. Finally, the layout of this LED-driving controller is realized according to its circuit, and then the total post-simulation is completed with a satisfactory result to meet the defined technological parameters.