Design Of3-channel Constant Current LDE Driver

LED is a kind of light resource with high efficiency, durability, and safety. LED is considered the fourth generation of light source which will replace traditional incandescent light and fluorescent light and become the primary light source in the future. Meanwhile, the technology of LED driver is making continuous progress. LED driver chip is the key part of the lighting system, so the research on LED driver is of great value. Due to people’s increasing demand for a better life, the research on LED driver is facing new challenges.This paper presents a design of a novel constant current LED driver for high power application. It can be used in occasions such as architectural lighting, entertainment lighting, backlighting, etc. The chip incorporates three-channel constant current circuitry to drive RGB LED strings. The maximum output current amounts to500mA and its current skew is±0.54%.There are two ways of dimming: linear dimming and PWM dimming. Users can set the value of the output current by adjusting the external resistors. They can also set the proportion of the RGB colors by adjusting the duty cycle of the enable signals. The two ways of dimming can be combined to control the grey scale and color manipulation. Furthermore, the chip incorporates a fault-detection system. If the ambient temperature exceeds111.8℃or open circuit occurs, the chip will release alarm signal. If the ambient temperature exceeds180.8℃, the chip will shut down all the output currents automatically.The fault-detection system has greatly improved the stability of the system.This LED driver chip is designed by CSMC0.8um BCD process. The design is verified by Cadence spectre simulator. The simulation results show that the design meets the expectation. The layout has been completed and its area is2939um×1469um.