White LED Driver Ic Design

With its high efficiency, energy saving, environmental protection, long life and high reliability,high-power LED is gradually replacing traditional incandescent lamp, fluorescent light the next generation. With the improved performance of high-power LED lighting and production cost reductions, its field of application, by some of the brightness of less demanding areas of landscape lighting, extends to the general white lighting. At the same time, with supporting research and development of the power type LED driver ICs and because of the increasing popularity of power LED applications, LED has been significantly developed.In this paper, the series saturation constant current driver IC is designed to provide a constant drive current when the power supply voltage or ambient temperature changes for the high-power LED. The constant current control circuitry and power-driven MOS transistors is integrated on the same chip so as to make the power devices and control circuitry compatible with integrated design.Firstly, according to the functional of the chip, the overall structure of the drive circuit was designed, and then following the functions the sub-module was also designed, which contained three high-gain amplifiers, a thermal shutdown protection module, and a high precision band-gap reference with 93.5 ppm /℃temperature coefficient in order to maintain LED's brightness.Based on the circuit theory analysis and circuit module design, CSMC 0.5μm CMOS process is used and the cadence software emulation is made. The average of the driving current is designed to 350mA. When the power supply voltage changes 10%, the change of high-power white LED lighting variation on the average current is required to be within 5%: When the ambient temperature changes from 0℃to 80℃, the change of the average current does not exceed 5%; the efficiency of entire control circuit power supply is more than 80%.