Design, Based On Adaptive Constant-current Type Of Charge Pump White Led Driver

White LEDs have been widely used as backlight in portable electronic products. The most competition advantages of Charge-Pump ICs are less EMI, lower cost and less size. With the larger output current, the lower output resistance and the higher efficiency of the new-style Charge-Pump ICs, Charge-Pump ICs have been a popular choice as LED drivers. A LED driver based on adaptive charge pump with constant current is designed in this thesis. It is suitable for cell phones, digital cameras, MP3 players and other handhelds with color displays.Utilizing proprietary adaptive 1X/1.5X modes maintains the highest possible efficiency over the whole input voltage range. And the input and output ripples are reduced by"Linear"mode charge pump. LDO (Low-dropout) current regulators adjusting the current of LEDs independently maintain constant current for uniform intensity. The full-scale LED current is set by an external resistor, while on/off states are controlled by two digital inputs and brightness can also be selected by them as well as PWM (pulse-width modulation) signal does. The inrush current at turn-on is limited through the soft-start module. Besides, the circuit contains the functions of under-voltage protection, over-voltage protection and over-temperature protection.At first, basic theories and key parameters of the charge pump circuit and some methods of LED constant current driving are given. Then, based on the design guideline of LED drivers, the sub-blocks including LDO current regulator, under-voltage protection, power selector and soft start are designed. At last, the whole chip function simulation and typical performance characteristics simulation are presented. The simulation results indicate that the LED driver has achieved the design specification. Furthermore, the circuit principle analysis has been verified.This thesis is a production of the great combination of circuit principles nd simulation practices.