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1、液晶显示器驱动原理,For:NBLCM F.A.TeamAuthor:Jessica _ LinDate: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FlickerGamma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,垂直偏光板,玻璃电极,玻璃电极,液晶,水平
2、偏光板,LCD如何控制亮度,E,TFT-LCD制造流程,TFT-LCD驱动原理,Response TimeStorage 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,Drivingsignal,LCD opticresponse,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,液晶必须以交流信号驱动否则液晶将受破坏,odd frame,e
3、venframe,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 Voltage,Data Voltage,调整Vcom可补偿V各灰阶Clc不一样大,各阶最佳Vco
4、m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 horizontal and vertical cross-talk,Row inversion,Higher
5、 powerReduced flickerLower vertical cross-talkSensitive to horizontal cross talk,液晶极性反转驱动,液晶极性反转驱动,Column inversion,Lower powerReduced flickerLower horizontal cross-talk,Dot inversion,Higher powerMinimum flickerHighest image quality,液晶极性反转驱动,液晶极性反转驱动,2 line inversion,Higher powerMinimum flickerHigh
6、image quality,What Is Gamma Curve,The gamma curve is the curve that presents the luminance ofeach 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 1.Flicker2.Cross Talk3.Image Sticking4.3-level VGH的作用,1.Flicker产
7、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 generator2.Know the I/F(TTL,LVDS,TMDS)3.Know the connector pin define4.Light on5.Fail analysis6.Find the wrong sourcea.Power Check(Vaa,Vcom,Vgh,Vgl,Vcc)b.Signal Check(The abnormal display)7.Timing Analysis,
