Research And Design Of White LED Driving Circuit Chip XDJ6375 Based On Charge Pump DC/DC

A kind of high efficiency white LED driver IC based on Charge Pump(DC/DC) is designed on the basis of the project"Theoretical research and design of key techniques for power management IC of Institute of Electronic CAD,Xidian University"in this thesis. The chip named as XDJ6375 is a high efficiency charge pump driving up to four white LEDs in the main display and up to two white LEDs in the sub-display with regulated constant current for uniform intensity. By utilizing adaptive 1X/1.5X Charge Pump modes and very-low-dropout current regulators, it achieves high efficiency over the full 1-cell lithiumbattery input voltage range. The circuit design of the subblocks of XDJ6375 has been finished now. The simulation and test results indicate the design of this chip is successful. The design project has passed the acceptance check.This thesis makes deep and systemic analysis to the basic principles of white LED and analyzed basic theories of four kinds of white LED driver, which including: (1).Parallel connection driving with constant voltage output adding adjusted resistance; (2).Parallel connection driving with single constant current resource adding adjusted resistance;(3).Parallel connection driving with many constant current resources;(4).In series driving with increasing voltage by inductance. Having analyzed theory of switched-capacitor DC/DC converts, we designed a kind of high efficiency white LED driver IC based on Charge Pump with the first mode of power mangment in the way of driving LED with Charge Pump and adjusted resistance.The detailed system design and the circuit designs of the key sub-blocks of XDJ6375 are given in this paper. And the simulation of all functions and electrical characteristics are presented. As a result of the excellent system design, the transient response speed of the chip becomes more faster. By adopting the technologies of synchronous rectification, double operation mode and the CMOS circuit, the efficiency of this chip is up to 92%. To improve the reliability of the chip, many protection circuits such as thermal shutdown and over voltage protection are designed.