一种应用于AMOLED的宽电压摆幅高精度伽马校正电路设计

Design of a wide voltage swing high-precision Gamma correction circuit for AMOLED

针对AMOLED显示驱动芯片对高精度、低功耗的应用需求,设计了一种宽电压摆幅、高精度、具有温度补偿功能的伽马校正电路。电路通过幅值调节和斜率调节,并微调关键点,从而改变DAC输出曲线,更好地拟合灰阶-电压曲线实现高精度。通过使用轨到轨输入级及基于亚阈值跨导恒定设计的输出缓冲器电路保证了宽输入电压范围,采用Cascode Miller补偿结构以降低补偿电容大小,提高稳定性和响应速度。电路使用了温度补偿结构以平衡温度变化对灰阶电压带来的影响。仿真结果表明在UMC 80 nm的工艺下,在输入电压为0.2~6.3 V的范围内,设计的伽马校正电路的响应时间在20μs,电路输出电压的误差在3 mV以内。性能基本不受温度影响,满足了分辨率为1080×2160的AMOLED驱动芯片的设计需求。

Aiming at the application requirements of AMOLED display driver chips for high precision and low power consumption,a Gamma correction circuit with wide voltage swing,high precision and temperature compensation is designed.The circuit uses amplitude adjustment and slope adjustment,fine-tune key points to change the DAC output curve,and better fitting the grayscale-voltage curve to achieve high accuracy.By using rail-to-rail input stage and output buffer circuit based on constant sub-threshold transconductance design,a wide input voltage range is guaranteed.Cascode Miller compensation structure is used to reduce the size of the compensation capacitor and improve stability and response speed.The circuit uses a temperature compensation structure to balance the effect of temperature changes on the gray-scale voltage.The simulation results show that under the UMC 80 nm process,within the range of 0.2~6.3 V input voltage,the response time of the designed Gamma correction circuit is 20μs,and the error of the circuit output voltage is within 3 mV.The performance is basically not affected by temperature and meets the design requirements of AMOLED driver chips with a resolution of 1080×2160.