Based On Efficient Adaptive Charge Pump White Led Driver Circuit

Portable electronic devices such as cellular phone and MP4 are becoming more and more popular, and there is great demand for Li-battery power management chips. White color LED driver based on charge pump has the advantage of being inductance-less, less outer component, high system efficiency, lower cost and shorter smaller lighter thinner. So it has played a key role in low power and medium power management application.A white color LED driver based on high efficiency adaptive charge pump using 0.6μm CMOS technology is presented in this paper. It is a cooperative program from a company. According to the variation of Li-battery voltage and white color LED, it uses fractional (1X/1.5X/2X) conversion to increase efficiency and linear mode to generate the lowest possible ripple. This chip can provide current for 5 backlight LED and 2 flash LED at the same time from a 2.7V to 5.5V input. The maximum current is 30mA and 200mA respectively. A serial control interface is used to enable, disable, and set the LED drive current for 16-level and 32-level scale LED brightness control. The chip has a thermal management system for protection in the event of a short-circuit condition on any of the output pins. Built-in tri-mode soft-start circuitry prevents excessive inrush current on power switch during start-up.This paper first presents basic operating principles of 1.5X and 2X charge pump, then introduces control mode and key performance parameters of different kinds of charge pump. Through topology selection,switch implementation,loop stability analysis and system efficiency evaluation, this paper chose appropriate charge pump architecture. What's more, this paper presents circuit design and simulation analysis of several sub-modules, such as oscillator,mode selector,error amplifier and power selector.Based on charge pump analysis and sub-modules design, HSPICE is used to simulate and analyze whole chip key specification. The simulation results show that the chip function and important specification meets the design goals.