The Key Technology Of White LED Display Backlighting Driver

White LED, as the best choice of backlighting of color LCD, has been widely applied to portable electronic fields, such as mobile phone, digital camera MP3 and so on. In the recent years mobile phone has renewed continually and become more and more popular, all these impel output of white LED and its driver uprush. In order to meet the requirements of different input voltage, different output current and different series number LED from the market, So R&D on white LED driver has become the hotspot of power supply market.The White LED driver's main function is providing constant current, and now it has become the key point of the power management field. Using step-up DC/DC converter to drive White LED is a major method for portable applications. The design of the step-up DC/DC converter Chip, with the current mode PWM control and synchronous rectification, is introduced in this thesis.Based on requirement of this design, a current-mode PWM controller and nonsynchronous rectifier mode technology are used to increase the transient response and stability. The basic principles of slope compensation and oscillator are discussed, the corresponding circuits and the simulation results are also given In this design, A window comparator oscillator core structure has been used to ensure precision; piecewise linear compensation has been used in Current slope compensation to ensure a suitable compensation under different load intensity.Finally, Hspice simulation results of the whole Chip are given: 1 MHz swithing frequency. Up to 8 LEDs at 25 mA and the highest conversion efficiency of 86% can all be achieved. The chip can be timely protected by the 2.6 V under voltage protection function. Analog Direct-PWM and brightness adjustment functions can also be achieved. Simulation results show that the chip has achieved the expected demand.