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1、液晶显示器驱动原理,For : NBLCM F.A. Team Author: Jessica _ Lin Date:2009/1/8,液晶显示操作原理 TFT-LCD驱动原理 Storage Capacitor (Cst) Feed-through与Vcom补偿 液晶极性反转驱动与Flicker Gamma调整 常见的问题 Q & A,Outline,液晶显示操作原理,图像组成,对6 bit显示器而言, 共可以显示26x 26x 26= 262,144 对8 bit显示器而言, 共可以显示28x 28x 28= 16,777,216,LCD可显示的颜色数目,TFT-LCD结构示意图,光源,垂
2、直偏光板,玻璃电极,玻璃电极,液晶,水平偏光板,LCD如何控制亮度,E,TFT-LCD制造流程,TFT-LCD驱动原理,Response Time Storage Capacitor (Cst) Feed-through与Vcom补偿 Flicker与液晶极性反转驱动 Gamma调整,Response Time,Von,Voff,Driving signal,LCD optic response,Response time of MVA test cell,Tr,Tf,TFT LCD Cell,让液晶显示器正确显示 如何充电到正确的电压准位? 如何保持正确的电压准位?,液晶极性反转驱动,液晶必
3、须以交流信号驱动 否则液晶将受破坏,odd frame,even frame,16.67ms,time,Vcom,Vcom,Vg,Vd,Vs,V,Vgh,Vgl,Feed-through: V = (Vgh - Vgl) * Cgs / (Cgs + Cst + Clc),1 line,1 frame,Feed-through,Scan line signal,data line signal,LC所见电压,CF电极电压,Transmittance,V,+V,-V,Transmittance,Vd,Vs,Vcom,Optimized Vcom,Transmittance,Data Voltag
4、e,Data Voltage,调整Vcom可补偿V 各灰阶Clc不一样大,各阶最佳Vcom值也会不一样 适当调整各灰阶正负极性电压,使各阶最佳Vcom值尽量接近,Flicker,time,16.67ms,Vcom,正负极性电压不均衡 正负极性亮度不均衡 Flicker 调整Vcom有效果 但整片panel的Vcom并非完全一样!,Applied voltage shifts,液晶极性反转驱动,Frame inversion,- Lower power - Sensitive to flicker due to lack of spatial averaging - Sensitive to h
5、orizontal and vertical cross-talk,Row inversion,Higher power Reduced flicker Lower vertical cross-talk Sensitive to horizontal cross talk,液晶极性反转驱动,液晶极性反转驱动,Column inversion,Lower power Reduced flicker Lower horizontal cross-talk,Dot inversion,Higher power Minimum flicker Highest image quality,液晶极性反转
6、驱动,液晶极性反转驱动,2 line inversion,Higher power Minimum flicker High image quality,What Is Gamma Curve,The gamma curve is the curve that presents the luminance of each gray scale.,TFT-LCD驱动电路简介,GAMMA,TCON,DC/DC,Input Signal (LVDS),TAB IC,TFT-LCD驱动电路,TFT LCD Panel,THE EDN,THANKS FOR YOUR ATTENDANCE,5.常见的问题
7、 1. Flicker 2. Cross Talk 3. Image Sticking 4. 3-level VGH的作用,1.Flicker产生的原因,Frame 1,Frame 1,Frame 2,Frame 2,如何破解FlickerPattern (2 line inversion),Frame 1,Frame 1,Frame 2,Frame 2,2.CrossTalk产生的原因 2.1 Vaa 电压不稳,2.2 ScanPulse overlape,可由OE 控制,3.Image Sticking,Ans: 加速VGL放电至GND 因若Scan Pulse的准位维持在VGL, 其漏电
8、流很小,4. 3-level Scan Pulse的功用,VGH,VGL,V,Ans: 同一个画面各dot的Vfh愈小 愈容易找到一组Vcom去满足画面中 各dot,其Flickler现象愈小,5.Debug Process,1.Get a good test fixture: 6/8 bit pattern generator 2.Know the I/F (TTL,LVDS,TMDS) 3.Know the connector pin define 4.Light on 5.Fail analysis 6.Find the wrong source a.Power Check (Vaa,Vcom,Vgh,Vgl,Vcc) b.Signal Check (The abnormal display) 7.Timing Analysis,