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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。
Design a negative charge pump low dropout current source white LED driver chip. Based on the negative charge pump principle, the parasitic resistance of the current regulating transistor and the ground pad in the conventional positive charge pump structure is eliminated, and the voltage drop of the current source in the current regulating module can reach an ultra-low voltage of 80 mV, thereby reducing the loss. The LED driver current is controlled by the pulse signal and the enable terminal design. It can provide 16 different constant driving currents in the range of 1.25 ~ 20 mA within the operating voltage of 2.8 ~ 5 V, realizing 16 different brightness dimming functions of the LED lamp. Charge pump output ripple almost does not affect the brightness and color of the LED. The design of the chip is completed with the CSMC 0.5μm CMOS process. The results of the chip test show that the maximum variation of the LED current is 0.4 mA and the test efficiency reaches 89.3% within the chip operating voltage range, meeting the requirements of high efficiency and stability.