CN109215591A - 一种外部补偿电路及驱动方法 - Google Patents
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- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
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- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
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- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
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- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
- G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
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Abstract
一种外部补偿电路及驱动方法,其中电路包括薄膜晶体管T1、T2、T3;所述晶体管T1的源端与数据电压Vdata信号或感应线信号连接,控制端与扫描信号连接,漏端与T2的控制端连接,所述T2的源端与工作电压VDD连接,漏端接地,T2的源端与控制端之间还设置有电容C1;所述T2的漏端还与T3的漏端连接,T3的源端接T1的源端,T3的控制端接感应门信号。解决现有技术中OLED现实出现残影及TFT容易恶化的问题。
Description
技术领域
本发明涉及液晶面板显示领域,尤其涉及一种液晶面板克服残影的外部补偿电路。
背景技术
有机发光二极管(Organic Light Emitting Diode,OLED)依驱动方式可分为被动式矩阵驱动(Passive Matrix OLED,PMOLED)和主动式矩阵驱动(Active Matrix OLED,AMOLED)两种。其中,PMOLED是当数据未写入时并不发光,只在数据写入期间发光。这种驱动方式结构简单、成本较低、较容易设计,主要适用于中小尺寸的显示器。
一般的,AMOLED显示器需要通过显示驱动芯片将处理器或外部接口送来的数字显示信息转换为模拟信号来控制面板上的像素电路进而显示图像。OLED非线性的光电特性会对显示效果造成不良的影响,因此驱动芯片里集成有GAMMA电压产生模块,产生校正过的GAMMA电压,以此来消除OLED非线性光电特性的影响,将实际图像尽可能真实的显示出来。
OLED的亮度随流过的电流密度增加而增加,目前主要采用的技术是通过编码AMOLED显示面板中的由薄膜晶体管组成的像素驱动电路中的驱动管的电压来控制通过OLED器件的电流从而控制亚像素点的显示亮度,但是OLED器件老化后即使流过相同大小的电流,OLED发光的亮度与新像素相比也会下降,所以老化后OLED对应于像素驱动电路的曲线响应发生改变。
因此除考虑显示面板由于TFT不匹配而造成的显示不均匀,及TFT老化对显示效果的影响,也要考虑OLED器件本身老化所带来的影响,目前一般为采用内部补偿的方式,但内部补偿电路需要在sub Pixel上做5~7颗TFT和至少一颗电容,随着PPI越来越高,单位像素面积变小,很难在如此小的像素面积内布局如此多颗TFT,同时也对制程难度要求较高,良率会下降。
相对地外部补偿电路所需TFT数目较少,往往只需要3颗TFT,IC通过sense电流或电压对写入讯号重新编辑从而实现像素补偿;其像素的空间布局要求较低,同时可以补偿TFT和OLED器件;但是一般的外部补偿电路无法补偿TFT操作期间的磁滞效应造成的画面残影。
发明内容
为此,需要提供一种能够解决液晶面板显示过程中由于TFT薄膜晶体管的磁滞效应带来的画面残影,补偿由于device的恶化造成的显示质量问题。
为实现上述目的,发明人提供了一种外部补偿电路,包括薄膜晶体管T1、T2、T3;所述晶体管T1的源端与数据电压Vdata信号或感应线信号连接,控制端与扫描信号连接,漏端与T2的控制端连接,所述T2的源端与工作电压VDD连接,漏端接地,T2的源端与控制端之间还设置有电容C1;所述T2的漏端还与T3的漏端连接,T3的源端接T1的源端,T3的控制端接感应门信号。
进一步地,所述T2的漏端通过二极管接地。
一种外部补偿电路驱动方法,适用于上述外部补偿电路,包括数据电压、扫描驱动电压,在扫描驱动电压使能阶段开始之前,数据电压变为第一电压值,并持续至扫描驱动电压使能阶段开始,随后数据电压变为第二电压值,在扫描驱动电压使能阶段结束前,数据电压变为第三电压值,第三电压值持续至扫描驱动电压结束;第三电压值为使像素工作的数据写入电压,第一电压值小于第三电压值,第二电压值小于第一电压值。
进一步地,所述第二电压值为零或负压。
区别于现有技术,上述技术方案本发明相对与传统的外部像素补偿电路结构,有以下两个优点:可补偿device的恶化造成的显示质量问题,解决外部补偿电路难以克服残影的状况;最后其驱动方式可以缓解driving TFT的恶化。
附图说明
图1为具体实施方式所述的3T1C外部补偿电路图;
图2为具体实施方式所述的TFT电性磁滞效应示意图;
图3为具体实施方式所述的3T1C外部补偿电路图;
图4为具体实施方式所述的3T1C外部补偿电路驱动信号图。
具体实施方式
为详细说明技术方案的技术内容、构造特征、所实现目的及效果,以下结合具体实施例并配合附图详予说明。
图1是目前采用的3T1C结构的外部补偿电路,有3颗TFT,分别是T1、T2和T3,一颗电容C1,两个驱动讯号scan,面板级间扫描信号和sense gate信号,1条数据讯号Vdata和1条sense line信号。其主要的工作原理:1.display阶段:scan讯号依次打开T1,电压储存在电容C1电极上的A点,A点电压是driving TFT T2开启,从而驱动OLED发光,显示图像信息;2.sense和补偿阶段:在开机或关机时间段,Scan依次打开,data讯号写入,sense scan依次打开,探测OLED device阳极电压或流过的电流,根据探测状况,做出mapping图,根据探测结果,数据讯号会重新写入,以便显示的均匀性。该电路架构和相对的IC虽然可以补偿TFT和OLED device的恶化,当由于TFT电性的磁滞效应引起的显示异常时(如残影)却无法补偿。
图2是TFT电性的磁滞效应,如果某一像素的灰阶从L255变为L127时,A点(对应图1)的电压由有高变低,对应的TFT是反扫曲线(图2),假设L127的data驱动电压是3V,最终L127灰阶对应的是图2中曲线的b点。相对地如果另一像素的灰阶是从L0灰阶变化到L127灰阶时,对应的TFT是正扫曲线,最终L127灰阶对应的是图2中曲线的f点,由于TFT电性的磁滞效应,b和f点的电流不一样,这会造成OLED面板显示异常,如残影等。
为了解决上述的OLED面板残影的问题,在图3所述的实施例中,我们给出了本发明的3T1C架构图,包括薄膜晶体管T1、T2、T3;所述晶体管T1的源端与数据电压Vdata信号或感应线信号连接,控制端与扫描信号连接,漏端与T2的控制端连接,所述T2的源端与工作电压VDD连接,漏端接地,T2的源端与控制端之间还设置有电容C1;所述T2的漏端还与T3的漏端连接,T3的源端接T1的源端,T3的控制端接感应门信号。相对一般3T1C外部电路架构,本发明会减少1条sense line讯号,采用data line和sense line共用一条讯号线,其主要的工作原理:1.display阶段:scan讯号依次打开T1,电压储存在电容C1电极上的A点,A点电压使driving TFT T2开启,从而驱动OLED发光,显示图像信息;2.sense和补偿阶段:在开机或关机时间段,Scan依次打开,data讯号写入后,scan关闭,A点保持电位;画面保持不变;sensescan依次打开,此时的讯号线选为sense line,探测OLED device阳极电压或流过的电流,根据探测状况,做出mapping图,根据mapping图,数据讯号会重新写入,以便显示的均匀性。该电路架构和相对的IC就可以补偿TFT和OLED device的恶化,为了更好的补偿,本发明需sense R(L0、L64、L128、L188和L255)、G(L0、L64、L128、L188和L255)、B(L0、L64、L128、L188和L255)和灰阶(L0、L64、L128、L188和L255)画面等20个pattern画面。
图3中本发明的3T1C架构可减少一条sense line,同时为了降低TFT的磁滞效应引起的显示质量下降,本发明要求data驱动讯号分为两部分,如图4所示,为本发明的一种外部补偿电路驱动方法,适用于上述外部补偿电路,包括数据电压Vdata、扫描驱动电压Scan,在扫描驱动电压使能阶段开始之前,数据电压变为第一电压值,并持续至扫描驱动电压使能阶段开始,随后数据电压变为第二电压值,在扫描驱动电压使能阶段结束前,数据电压变为第三电压值,第三电压值持续至扫描驱动电压结束;第三电压值为使像素工作的数据写入电压,第一电压值小于第三电压值,第二电压值小于第一电压值。
在scan打开过程中,有两个过程:1.对A点首先充到较低电位,将driving TFT T2处于off状态,2.然后data电位变为要写入的讯号,进而将数据讯号写入A点,driving TFTT2打开,OLED被驱动到显示的亮度。在scan打开过程中,A点首先被电位重置,然后写入到想要的电位,这使得TFT只工作如图1的正扫曲线,就不会因上一帧讯号的差异对本帧像素显示造成影响。
为了更好地实现本发明消除残影的技术目的,在进一步地的实施例中,所述第二电压值即重置阶段的点位a可以为零或负压。data电位中的重置讯号电位a是可控,因driving TFT T2在工作时间受到栅极的正偏压stress,故在重置阶段A点加一个合适点的负电压a可使driving TFT T2受到栅极负偏压,可有效缓解TFT的恶化状况,提高显示质量的可靠性。重置阶段的电压a因根据实测中TFT的特性合理的设定。
需要说明的是,尽管在本文中已经对上述各实施例进行了描述,但并非因此限制本发明的专利保护范围。因此,基于本发明的创新理念,对本文所述实施例进行的变更和修改,或利用本发明说明书及附图内容所作的等效结构或等效流程变换,直接或间接地将以上技术方案运用在其他相关的技术领域,均包括在本发明的专利保护范围之内。
Claims (4)
1.一种外部补偿电路,其特征在于,包括薄膜晶体管T1、T2、T3;所述晶体管T1的源端与数据电压Vdata信号或感应线信号连接,控制端与扫描信号连接,漏端与T2的控制端连接,所述T2的源端与工作电压VDD连接,漏端接地,T2的源端与控制端之间还设置有电容C1;所述T2的漏端还与T3的漏端连接,T3的源端接T1的源端,T3的控制端接感应门信号。
2.根据权利要求1所述的外部补偿电路,其特征在于,所述T2的漏端通过二极管接地。
3.一种外部补偿电路驱动方法,其特征在于,适用于权利要求1或2所述的外部补偿电路,包括数据电压、扫描驱动电压,在扫描驱动电压使能阶段开始之前,数据电压变为第一电压值,并持续至扫描驱动电压使能阶段开始,随后数据电压变为第二电压值,在扫描驱动电压使能阶段结束前,数据电压变为第三电压值,第三电压值持续至扫描驱动电压结束;第三电压值为使像素工作的数据写入电压,第一电压值小于第三电压值,第二电压值小于第一电压值。
4.根据权利要求3所述的外部补偿电路驱动方法,其特征在于,所述第二电压值为零或负压。
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CN108053793A (zh) * | 2017-12-15 | 2018-05-18 | 京东方科技集团股份有限公司 | 显示装置、显示基板及显示补偿方法和装置 |
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CN104050923A (zh) * | 2014-04-08 | 2014-09-17 | 友达光电股份有限公司 | 像素电路及采用此像素电路的显示设备 |
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