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1、液晶显示器驱动原理For : NBLCM F.A. TeamAuthor: Jessica _ LinDate:2009/1/8液晶显示操作原理液晶显示操作原理TFT-LCDTFT-LCD驱动原理驱动原理Storage Capacitor (Cst)Feed-through与Vcom补偿液晶极性反转驱动与FlickerGamma调整常见的问题常见的问题 Q & AOutline液晶显示操作原理图像组成RedGreenBlueWhiteGray Scale 0816243240485663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2
2、8x 28x 28= 16,777,216LCD可显示的颜色数目TFTPolarizer偏光板 CFPolarizer偏光板 PCB灯管LC cellTFT-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偏光板LCD如何控制亮度EGDSTFT-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Scan Line扫描线Data Line讯号线Response TimeVonVoffDrivingsignalLCD opticresponseRes
3、ponse time of MVA test cellTrTfGDSData lineScan lineVstVcomClcCstCgsVgVdVsTFT 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 frameevenframe16.67mstimeVcomVcomVgVdVsVVghVglFeed-through:V = (Vgh - Vgl) * Cgs / (Cgs + Cst + Clc)1 line1 frameFeed-throughGDSData lineScan lineVs
4、t VcomClcCstCgsVgVdVsScan line signaldata line signalLC所见电压CF电极电压Transmittance+V-VIdeal VcomV+V-VTransmittanceVdVsVcomOptimized VcomTransmittanceData VoltageData 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Flickertime16.67msVcom正负极性电压不均衡正负极性亮度不均衡Flicker调整调整VcomVcom有效果有效果但整片
5、但整片panelpanel的的VcomVcom并非完全一样并非完全一样!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 power-Reduced flicker-Lower vertical cross-talk-Sensitive to horizontal
6、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液晶极性反转驱动液晶极性反转驱动+-+-+-+-+-+-+-+2 line inversion-+-+-+-+-+-+-+-Higher power-Minimu
7、m flicker-High image qualityWhat Is Gamma CurveRedGreenBlueWhiteGray Scale 0816243240485663The gamma curve is the curve that presents the luminance ofeach gray scale.LGray scaleTimingControllerData DriverTFT-LCD PanelScan DriverRGB pixelSTHSTVDC/DCConverterGammaCorrectionVccTTLRSDSTTLLVDSTMDSTFT-LCD
8、驱动电路简介GAMMATCONDC/DCInput Signal (LVDS)TAB ICTFT-LCD驱动电路TFT LCD PanelTHE EDNTHANKS FOR YOUR ATTENDANCE5.常见的问题常见的问题 1. Flicker2. Cross Talk3. Image Sticking4. 3-level VGH的作用1.Flicker产生的原因+ - + -+ - + - + - +- + - + - + -+ - + - + - +- + - + - + -+ - + - + - +- + - + - + -+ - + - + - +- + - +Frame 1Fr
9、ame 1Frame 2Frame 2如何破解FlickerPattern (2 line inversion)+ - + -+ - + - + - +- + - + - + -+ - + - + - +- + - + - + -+ - + - + - +- + - + - + -+ - + - + - +- + - +Frame 1Frame 1Frame 2Frame 22.CrossTalk产生的原因2.1 Vaa 电压不稳2.2 ScanPulse overlapeScan NScan N+1Scan NScan N+1Scan NScan N+1Scan NScan N+1可由OE控
10、制3.Image StickingAns:加速VGL放电至GND因若ScanPulse的准位维持在VGL,其漏电流很小4. 3-level Scan Pulse的功用VGHVGLVfh= V xCgdCgd+ Clc| CstVAns: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 Process1.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
