液晶显示器驱动系统详解.ppt

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1、主动矩阵式液晶显示器AM-LCDsTFT LCDs等效电路Row DriversColumn DriverArrangement of Color FilterR G B R G BR G B R G BR G B R G BRBG RGBRBGRBG RGBRBGRBG RGBRBGRGGBRGGBRGGBRGGBRGW BRGW BRGW BRGW BStripeTrianglePixel Structure of TFT LCDsCs on Common与Cs on Gate架构液晶画素TFTGate LineData LineCsCs液晶画素TFTCommonCommonGate Li

2、neData LineCsCs Cs onCommonCs on GateTiming Chart of TFT LCDsFrame TimeGate123NTimeTFT LCDs Driving MethodColumn InversionDot InversionRow InversionFrame InversionDirect Driving of TFT LCDs DC Biasof CommonGrayScale VoltageV0V1V2V3V4V5V6V7V7V6V5V4V3V2V1V01Frame/1 LineAC Modulation Addressing of TFT

3、LCDsV0V1V2V3V4V5V6V7V7V6V5V4V3V2V1V0Common WaveformGraylevel Voltage1Frame/1 LineTFT LCDs的电光效应Direct AddressingTFT LCDs的电光效应AC AddressingTFT LCDs Driving Waveform Cs on Common(一)TFT LCD驱动波形(Cs on Common,Common=DC Bias)TFT LCDs Driving Waveform Cs on Common(二)TFT LCDs Driving Waveform Cs on GateTFT电容

4、效应的影响PixelCgdCgsCsdCsdbCsdb液晶电容的效应液晶电容CLC 会随液晶作用电压的改变而变化，因此在驱动液晶时会有残存的DC成份，其所造成的影响：Image Sticking.Picture Flicker.液晶作用电压大时，液晶分子趋向平行电场方向排列：液晶作用电场小时，液晶分子趋向垂直电场方向排列：二阶驱动方式的效应CsClcCgdCsdCgsVctCh(N-1)Ch(N)Vs垂直影像讯号水平扫描讯号Vg水平扫描讯号VgVshVslVstVthVth正极性驱动负极性驱动负极性驱动正极性驱动数据驱动芯片输出讯号电位液晶画素电位Vct=Vst-VpVpBlack(+)Whi

5、te(+)White(+)Black(+)Black(-)Black(-)White(-)White(-)TFT补偿驱动法Ch(N-1)Ch(N)Vst=Vct影像讯号波形Vs水平脉波扫描波形VgeVgeVghlCh(N-1)Ch(N)Vst影像讯号波形VsVge(+)Vge(-)VghlVghl3Level Addressing4Level Addressing3Level AddressingB(+)W(-)B(-)W(+)正极性负极性Vst=VctB(+)B(-)W(+)W(-)B(+)W(-)B(-)W(+)Vp=CgdVghl/Ct正极性负极性正极性Ct=Cs+Clc+Cgd负极性C

6、sVge/CtCsVge/Ct4Level AddressingVst=VctB(+)B(-)B(-)B(+)W(+)W(+)W(-)W(-)B(+)W(-)B(-)W(+)Vp(+)Vp(-)Vp=CgdVghl/CtCsVge(-)/CtCsVge(+)/Ct正极性负极性正极性负极性Ct=Cs+Clc+CgdCs on Gate电压补偿方式经由Cs将前一条水平脉波的补偿波形耦合到动作的液晶画素,补偿Cgd造成的电压漂移及改善液晶画素内的直流电电压残余.经由TFT的Cgd造成的电压漂移经由TFT的Cgd造成的电压漂移Comparsion of Addressing MethodHorizon

7、tal Line CrosstalkABCscCscCscTFT SubstrateColor Filter SubstrateHorizontal Area CrosstalkABVertical Area CrosstalkUpLowUpLowShading CrosstalkShading Crosstalk的抑制Gate Pulse的传递延迟Gate(Scan)Line的等效阻抗为一连串的串联 RC网络，因此 Gate Pulse在传递时会造成波形的传递延迟失真。RCRCRCRCN液晶画素边际电场效应(一)Reverse Tilt画素电极邻近电极共通电极VPVLVAVA VL:Disc

8、lination DisappearedVP LC Threshold VoltageReverse Tilt液晶画素边际电场效应(二)TFT水平驱动电极垂直驱动电极RubbingDirectionDisclinationLineReverse TiltDomain改善方法1.增加液晶分子的 预倾角(Pretilt Angle)2.增加Black Mask的 遮蔽面积驱动IC Scan DriverBidirectional Shift RegisterLevel Shift CircuitOutput BufferG1 G2 G3.STVRSTVLCPVR/LVDDDVSSDVDDAVSSA

9、STVRSTVLG1G2GxSerial In Serial Out Analog Data DriverSelectData jData j+1MultiplexerPro:Very simple.Fewer external connections.Con:Many analog inputs.Reduced pixel charging time.System Note:Sample clock:(Dot clock)/N,N Phases.Video Phase:NShift RegisterVideo InQiQi+1Variation on MultiplexerPro:Video

10、 Input.Con:Fast data line charging needed.Reduced pixel charging time.System Note:Shift Clock:(Dot Clock)/3 for Mono.Video Phase:3 for Mono.Sample and HoldSerial In Parallel OutAnalog Data Driver(一)Shift RegisterQiQi+1Qi+2Qi+3Video InTransferDouble Sample and Hold/Single PhaseSample NSample N+1Sampl

11、e N+2TTTNN+1N+2Out N-1Out NOut N+1Pro:Video Input.Small load on fast sample-and-holds.Full line time to charge pixel.Con:Complex analog circuit.Physical size.System Note:Shift Clock:Dot Clock.Video Phase:Single Phase.Serial In Parallel OutAnalog Data Driver(二)Shift RegisterQiQi+1Video InTransferDoub

12、le Sample and Hold/Multi-PhasePor:Reduced operation frequency.System Note:Video In:NVideo Phase:NShift Clock:(Dot Clock)/N.Digital Data Driver(一)Shift RegisterDACDACDACDACDAC SerialData BusDigital-to-analog ConvertersPor:Digital input.Con:Complex.Requires sufficient precision to correct for LC respo

13、nse variation.Shift RegisterCount Count Count Count CountRamp InSampled RampPor:Digital input.Programmable ramp.Con:Complex circuit.High speed digital circuits.Reduced pixel charging time.Digital Data Driver(二)Shift RegisterDecodeDecodeExternal Fixedvoltages1-of-n SelectorSimple DACPro:Digital input

14、.Programmable external voltages.Con:Complex circuit.High speed digital circuits.Many pass gates per data line.Digital Data Driver(三)All Digital CircuitGamma Correction of LCDXY取像组件取像电路显像电路显像组件摄像机测受像机测Analog Correction:2 3 Segment Approach.Digital Correction:External fixed voltage.Gamma Correction Si

15、mple CaseXY取像组件取像电路显像电路显像组件摄像机测受像机测TransmissionVoltageThe Block Diagram of the TFT LCD ModuleCCFL BacklightTFT-LCDPANELTiming ControllerScan DriverData DriverRGBCLKHsxVsxTFTLCD ModuleThe TFT LCD Module TypeClassified into two kinds by data driverAnalog type TFT-LCD moduleThe analog data driversThe a

16、nalog interface to PCOnly NECDigital type TFT-LCD moduleThe digital data driversThe ADC/LVDS/PanelLink interface to PCMainstreamThe Analog InterfaceGraphicsControllerTFT-LCDPANELTiming ControllerScan DriverAnalog Data DriverHsVsAnalogRGBAnalogRGBCLKHsxVsxPreAmpLevelShifterControllerPLLPCAnalog Modul

17、eTFTLCD ModuleOSDCCFL BacklightThe ADC InterfaceGraphicsControllerTFT-LCDPANELTiming ControllerScan DriverDigital Data DriverHsVsAnalogRGBDigitalRGBCLKHsxVsxADCBufferControllerPLLPCADC ModuleTFTLCD ModuleOSDCCFL BacklightThe LVDS/PanelLink InterfaceGraphicsControllerLVDS/PanelLinkTxLVDS/PanelLinkRxT

18、FT-LCDPANELTiming ControllerScan DriverCABLEClockHsVsDigitalRGBDigitalRGBClockHsVsPCTFT-LCD ModuleDigital Data DriverCCFL BacklightAnalog/ADC/LVDS/PanelLinkAnalog InterfaceTrue ColorSampling ErrorLow Edge SharpnessNoise in the Analog Signal TransmissionAnalog/ADC/LVDS/PanelLinkADC InterfaceMainstrea

19、m in the Desktop LCD Monitor InterfaceSampling ErrorLow Edge SharpnessNoise in the Analog Signal TransmissionEMI Issue for High Resolution FormatLow Image Quality and High CostAnalog/ADC/LVDS/PanelLinkLVDS InterfaceMainstream in the Notebook PC InterfaceHigh Edge SharpnessReducing EMI&Number of Cabl

20、e LineHigh Image Quality and Low CostShort Transmission Length&Low Noise MarginCompatible IssuePanelLink InterfaceApplication in the Desktop LCD Monitor InterfaceHigh Edge SharpnessReducing EMI&Number of Cable LineHigh Image Quality and Low CostSecond Supply Source IssueAnalog/ADC/LVDS/PanelLinkTFT

21、Module设计考虑(一)显示的影像讯号时序规格(Image Format)图框重复率(Frame Rate)水平扫描线扫描时间TFT的ION/IOFF电流水平扫描脉线的RC时间常数灰阶误差直流漂移TFT Module设计考虑(二)选择适合的驱动方式(Cs on Gate or COM)选择适合的极性转换方式驱动IC(Scan&Source)的选取TFT LCDs模块接口技术的选择大面积高分辨率TFT LCDs的开口率影响因素大尺寸面积增加水平驱动电极阻值增加水平驱动波形的时间常数增加水平扫描线减少液晶画素的有效充放电时间增加分辨率增加Cgd/CLC的比值增加Vgd 增加Reverse Til

22、tDomain与画素面积的比例增加Black Matrix的遮蔽面积降低画面质量增加水平驱动电极的宽度增加TFT的尺寸增加储存电容 CS 的面积降低开口率Plasma Addressing LCDsCathode-200VAnode0-200Negative ClowPositiveColumnFaraday DarkCathodeAnode-200V VirtualConnectionSamplingCapacitorAnalogSignalIn-Plane-Switch Mode LCDs偏光版解偏版液晶分子作用电极玻璃基板入射光作用电场方向出射光之极化状态 未加电场OFF状态 施加电场O

23、N状态出射光Vertical Alignment Mode LCDs未加电场OFF状态施加电场ON状态入射光偏光板液晶分子玻璃基板出射光之极化状态解偏板出射光Liquid Crystal ModesStrongly dependent on viewing angle低驱动电压视角窄小Off(White)On(Black)Slightly dependent on viewing angle广视角液晶反应速度慢Off(Black)On(White)画面对比低画面质量差Slightly dependent on viewing angle画面对比高广视角Off(Black)On(White)液晶反应速度快彩色画面显像佳TNIPSVA