Study And Design Of High Power LED Driver

LED is glamorous since the inception of the 20th century, it is a new type of semiconductor solid-state light sources which owns high efficiency, energy saving, environmental protection, long life, flexible application and can be controled easily, etc., so it is a typical of green lighting source. With the urban construction and the rapid development of electronic information industry, the need of light for people is increasing.LED's product development, research and production have become a very attractive prospect sunrise industry. It has been widely used in light,traffic lights, large LED display, LCD backlight and city's night lighting. In recent years, global energy is becoming more tension and global warming and environmental's protection under mounting pressure make that the use of LED semiconductor lighting has been recognized as an important means of saving and environmental protection, China has become the world's largest production of lighting appliances States and major exporting countries. With the urgent demand for LED lighting, the application on LED backlighting about notebooks, LCD TV backlighting, automotive lighting applications will soon be massive. The nonlinear characteristics of LED make that they should be powered with constant current driver, a good drive power be connected with the entire system stability and reliability.In this paper, I have studyed and designed a simple constant current driver circuit with high precision and high efficiency under the electrical properties of LED.The circuit uses BUCK topology with adjustable frequency, adjustable drive current and adjustable light (analog dimming and PWM dimming) feature.It is suitable for high power LED light string, the current drive capability can be adjustable between10mA ~ 1.2A, constant current control accuracy within±4%, input voltage range is among 4V ~ 30V. It is suitable for 5V, 12V, 24V DC power supply's applications.This paper outlines the research at home and abroad LED drive current situation and development trends and then describes the electrical properties of LED and LED driver analyzes the topology and control, and then, a simple structure with a cost advantage for high-power LED driver chip is designed, the driver chip includes voltage reference module includes,the oscillator module, the peak current sampling circuit module, PID compensation circuit, driver circuit module, logic modules and over-temperature protection module function modules. Design experience based on each sub-module functions and performance parameters of analysis, research, optimization. PID compensation circuit is used to improve the LED constant current accuracy.Globalfoundries 0.35um CMOS process is used in the design. Circuit design and layout design of the PWM constant current driver IC are finished in Candence. Finally, silicon was successful. Then I tested and validated the chip, found it accords with the pre-design requirements. Finally, this paper describes the results of the driver chip, including functional and performance testing, and then the applications are briefly introduced.