负电荷泵LED驱动芯片的设计与实现

Design and Implementation of a Negative Charge Pump LED Driver Chip

设计了一种负电荷泵低压差电流源白光LED驱动芯片。基于负电荷泵原理,消除了传统正电荷泵结构中电流调整晶体管和地焊盘的寄生电阻,电流调节模块中电流源的压降可以达到80 mV的超低压状态,降低了损耗。采用脉冲信号和使能端设计控制LED驱动电流,可在2.8~5 V工作电压内提供1.25~20 mA范围内16个不同的恒定驱动电流,实现LED灯的16级不同亮度的调光功能。电荷泵的输出纹波几乎不会影响LED的亮度与色差。采用CSMC 0.5μm CMOS工艺完成了芯片的设计。流片测试结果显示,在芯片工作电压范围内,LED电流变化的最大差值为0.4 mA,测试效率达到89.3%,满足高效和稳定的应用要求。

A negative charge pump white LED driver chip with low dropout current source was designed.Based on the negative charge pump principle,the parasitic resistances of the current regulation transistor and the ground pad in the traditional positive charge pump structure were eliminated.The voltage drop of the current source in the current regulation module could reach the ultra low voltage state of 80 mV and the loss was reduced.The LED drive current was controlled by the pulse signal and enable pin design.In the 2.8-5 V operating voltage,16 different constant drive currents from 1.25 mA to20 mA were provided to achieve the 16 different brightness dimming levels function of the LED lamp.The output ripple of the charge pump hardly affected the brightness and chromatic aberration of the LED.The chip was designed by the CSMC 0.5 μm CMOS process.The chip test results indicate that the maximum difference between the current changes of the LED is 0.4 mA and the test efficiency reaches 89.3% in the operating voltage range of the chip,meeting the application requirements of high efficiency and stability.