9W White LED Constant Current Driver IC Design

Solid semiconductor lighting source as the fourth-generation light source, with its high efficiency, low power cost, environmental protection, small size, long life and other characteristics has received increasing attention.With the high-power high-brightness white LED(Light Emitting Diode) lighting increased performance and lower manufacturing costs, it ranges from small area lighting, backlighting, decorative lights and other areas to road lighting, tunnel lighting and other lighting extension. It can easy to see that high-power white LED is gradually replacing incandescent, fluorescent and other traditional light source applications. Due to high-power white LED special electrical and optical properties, need to drive the circuit to work properly, therefore, with the increased use of power type LED, the corresponding driver IC R&D has also been developed.In this paper, research and design a dual series constant-current white LED driver chip. The chip can provide a constant current for each of two-way high-power white LED at the case of a certain temperature and supply voltage fluctuations.The circuit includes control module and power driver module. Control module includes three parts as band-gap reference voltage source, sampling feedback circuit, the control circuit, in which reference voltage generated by band-gap reference voltage source is send to the sampling feedback circuit as the detection voltage and reference voltage. Sampling feedback circuit feedbacks change information of the output current. Through the control circuit inhibiting the output current changes so that current is kept constant. Design of this power-driven module is the most important part of the circuit; this issue of the three kinds of power tube output structure has been compared, finally using bent-gate MOSFET structure as the output power. The design structure avoids the shortcoming of avalanche prone of the Net grill, and reduces the chip area occupied. The chip circuit implementation of the control circuit and power devices compatible with the design This design uses CSMC 0.5μm mixed-signal CMOS process; the process has the double-poly triple-metal process. Chip is a dual power supply and hybrid connections of high power white LED, so that the chip power conversion efficiency of 87.5%. When the power supply voltage changes by 10%, the variance of output drive current is 4.6%. When temperature varies from 0℃~ 100℃, the rate of output drive current change is 3.8%, and the two output currents can be achieved a better match.Chips designed can be used for backlight lighting of mobile phone, electric torch and other general lighting and portable lighting products. Optimization through basic improvements can be achieved overheating protection, over-voltage protection and ESD(Electrostatic Discharge) protection to make it more perfect performance, availability and further enhanced.