Pulse Width Modulation-based White Led Driver Chip Design

Nowadays the problems of energy sources and environment become more and more serious, semiconductor lighting has won people' s attention for its unique attributes of low energy consumption, low pollution , long life and high efficiency. As the quality of power LED improves and the cost of power LED reduce, semiconductor lighting will replace incandescent and fluorescent lighting gradually. With the development of power LED the research of its driving IC has also been greatly accelerated.The main research of the topic is to design a driving IC, which drives 3W LED by pulse width modulations. This IC provides a pulse current for two LED in series. By feedback circuits the driving current can modulate pulse width automatically and keeps the value of average current constant. The driving IC is consisted of a bandgap reference, a saw tooth wave generator, an error amplifier, a low-pass filter, a comparator and an on-chip power MOSFET. Besides, a new power MOSFET structure, which use N-well as its drain drift region, called Extended Drain NMOSFET, is suggested to improve NMOS breakdown voltage. The simulation result show that the breakdown voltage is boosted to about 16V and can fill the requirement of driving two power LED in series.The chip is fabricated in CSMC 5V 0. 6um double poly, double metal CMOS process. The average of the driving current is designed to 350mA. When voltage supply changes by 10%, the variance of the average driving current can be controlled within the range of 5%. When ambient temperature varies from 0℃ to 80℃, the variance of the average driving current can also be controlled within the range of 5%. The power efficiency of the chip is designed to larger than 80%.The first chapter introduces characteristics of LED and development of LED drivers;The second chapter covers the analysis of circuits design of the driving IC above;Chapter 3 is mainly about the layout design ofthe chip, it also presents the design of power MOSFET;the lastchapter emphasizes on the test results of the chip, and some analysis will be given according to the test results.