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CN1122165A - Device for restoring threshold voltage drift of amorphous silicon thin film transistor device - Google Patents

Device for restoring threshold voltage drift of amorphous silicon thin film transistor device Download PDF

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CN1122165A
CN1122165A CN 94191947 CN94191947A CN1122165A CN 1122165 A CN1122165 A CN 1122165A CN 94191947 CN94191947 CN 94191947 CN 94191947 A CN94191947 A CN 94191947A CN 1122165 A CN1122165 A CN 1122165A
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李学能
胡戴春
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Prime View Hk Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • 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
    • G09G3/34—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 by control of light from an independent source
    • G09G3/36—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 by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0243—Details of the generation of driving signals
    • G09G2310/0254—Control of polarity reversal in general, other than for liquid crystal displays
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/041—Temperature compensation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G09G2320/048—Preventing or counteracting the effects of ageing using evaluation of the usage time
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • 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
    • G09G3/34—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 by control of light from an independent source
    • G09G3/36—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 by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3614—Control of polarity reversal in general

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Thin Film Transistor (AREA)

Abstract

A method is provided for restoring the threshold voltage V of a thin film amorphous silicon transistor (12) deposited on a substrate (10)thDuring use, a gate voltage is applied to each transistor (12) to cause a voltage VthDrift over time. The apparatus detects when the LCD display (10) is not in use, and generates a control signal V when the LCD display is not in useg voltage Vg 'of opposite polarity, and applying Vg' to the transistor gate of the LCD display (10) to make VthDrifts in a direction opposite to the drift caused by Vg', thereby maintaining an effective drive voltage to the transistors of the LCD display (10).

Description

复原非晶硅薄膜晶体管器件 阈值电压漂移的装置Device for recovering threshold voltage drift of amorphous silicon thin film transistor device

本发明一般涉及关于非晶硅(α—Si：H)薄膜晶体管(TFT)器件的阈值电压漂移复原装置。更具体地说，本发明涉及在诸如数据驱动器和扫描驱动器电路那样的LED显示器中或者在象素开关元件中使用的α—Si：HTFT器件。The present invention generally relates to a device for restoring threshold voltage drift of amorphous silicon (α-Si:H) thin film transistor (TFT) devices. More particularly, the present invention relates to α-Si:HTFT devices used in LED displays such as data driver and scan driver circuits or in pixel switching elements.

因为非晶硅TFT有良好的开关特性，所以它们广泛地用于有源矩阵LCD显示器。然而，阈值电压Vth在工作时漂移，显示出非晶硅的不稳定，象温度和施加电压那样的因素可能在利用LCD显示器期间引起它的特性变化。通过研究发现，阈值电压随时间漂移是由于栅偏压引起的。当器件在越来越高的温度条件下工作时，将加速阈值电压的漂移。Since amorphous silicon TFTs have good switching characteristics, they are widely used in active matrix LCD displays. However, the threshold voltage V th drifts during operation, showing the instability of amorphous silicon, and factors such as temperature and applied voltage may cause its characteristics to change during utilization of an LCD display. It is found through research that the threshold voltage drifts with time due to gate bias. When the device is operated under higher and higher temperature conditions, the threshold voltage drift will be accelerated.

当用图形表示时，阈值电压Vth可以由横座标(TFT的栅电压Vg)与TFT漏电流的平方根沿纵座标的交叉点来限定。在LCD显示器运行中，比Vth大的栅压Vg是提供足以驱动LCD显示器的TFT象素元件的电流所必需的。整个期间的Vth的漂移以及其随着温度增加而加速的现象减少了栅、源之间的有效驱动电压，还减少了源、漏电流Ids，这导致了LCD TFT显示器性能的降低。When represented graphically, the threshold voltage Vth may be defined by the intersection of the abscissa (the TFT's gate voltage Vg) and the square root of the TFT leakage current along the ordinate. In LCD display operation, a gate voltage Vg greater than Vth is necessary to provide sufficient current to drive the TFT pixel elements of the LCD display. The drift of V th during the whole period and its acceleration as the temperature increases reduces the effective driving voltage between the gate and the source, and also reduces the source and drain current Ids, which leads to a decrease in the performance of the LCD TFT display.

因此，在LCD显示器使用期内，保持阈值Vth稳定是很重要和所希望的，因为Vth的漂移使Vg不能正常把开关象素TFT。Therefore, it is very important and desirable to keep the threshold V th stable during the life of the LCD display, because the drift of V th makes Vg unable to normally switch the pixel TFT.

例如，如图1所示，当把正40伏直流电压在25℃时加到TFT栅极上约15小时，阈值电压可能漂移6—7伏。如图2所示，在把具有50％占空度的30伏交流脉冲加到TFT栅极大约88小时的情况下，Vth可能漂移大约5伏。阈值电压漂移的方向取决于一给定TFT的栅源间电压的正负号。当把负的直流电压加到TFT栅极一定时间周期时，则产生一负的阈值电压漂移。例如，如图1所示，当把负的20伏电压加到TFT栅极时，Vth漂移大约为负的2.3伏。For example, as shown in FIG. 1, when a positive 40V DC voltage is applied to the TFT gate at 25°C for about 15 hours, the threshold voltage may drift by 6-7V. As shown in FIG. 2, in the case where a 30 volt AC pulse with a 50% duty cycle is applied to the TFT gate for about 88 hours, Vth may drift by about 5 volts. The direction of threshold voltage shift depends on the sign of the gate-source voltage for a given TFT. When a negative DC voltage is applied to the TFT gate for a certain period of time, a negative threshold voltage shift is generated. For example, as shown in FIG. 1, when a negative 20 volts is applied to the TFT gate, the V th shifts by about a negative 2.3 volts.

通常用于描述Vth漂移ΔVth的方程可以如下所示：The equation usually used to describe the V th shift ΔV th can be shown as follows:

ΔVth＝Aexp(-Ea/KT)(logt)αVgβ其中，A是常数，K是波尔兹曼常数，T是TFT的绝对温度，t是偏压Vg加到TFT栅极的时间。激活能数值Ea，参数α和β是通过实验利用公知的最小二乘方近似法最佳获得的，因为这些参数取决于非晶硅样品和显示器中使用的绝缘体的性质。ΔV th =Aexp(-Ea/KT)(logt) α Vg β where A is a constant, K is Boltzmann's constant, T is the absolute temperature of the TFT, and t is the time when the bias voltage Vg is applied to the gate of the TFT. The activation energy value Ea, the parameters α and β are best obtained experimentally using the known least squares approximation, since these parameters depend on the properties of the amorphous silicon sample and the insulator used in the display.

上述方程清楚地表示Vth与温度、时间、栅电压之间的依从关系。解释这种现象的理论之一是ΔVth是由于氮化物所俘获的电荷引起的。另一种理论是由非晶硅膜的积累层中产生亚稳的Si悬挂键所引起的。The above equation clearly shows the dependence of V th on temperature, time, and gate voltage. One of the theories to explain this phenomenon is that ΔV th is due to the charge trapped by the nitride. Another theory is caused by the generation of metastable Si dangling bonds in the accumulation layer of the amorphous silicon film.

在TFT—LCD于80℃运行大约10,000小时后，观察到大约4伏的电压漂移。通常，为了保持足够大的驱动电流，在显示器使用期内，要求ΔVth小于2伏。在象投影式TV那样的苛刻应用中，TFT处于恒定的高温状态，ΔVth在较短时期内就变得比较明显。ΔVth会达到相当大的其它应用包括飞机制造业和汽车制造业。After the TFT-LCD was operated at 80°C for about 10,000 hours, a voltage drift of about 4 volts was observed. Generally, in order to maintain a sufficiently large driving current, ΔV th is required to be less than 2 volts during the display lifespan. In harsh applications like projection TV, where the TFT is at a constant high temperature, ΔV th becomes more pronounced in a shorter period of time. Other applications where ΔV th can be quite large include aircraft manufacturing and automotive manufacturing.

在TFT—LCD显示器运行中，由于α—SiTFT的迁移率低，故需要高的栅电压Vg以便产生足够大的电流来驱动显示器的象素元件或其它元件。Vth的漂移减少了栅源之间的有效驱动电压，从而减少了源漏电流Ids，导致性能降低。因此非常希望在显示器使用期间保持低的Vth。In the operation of TFT-LCD display, due to the low mobility of α-SiTFT, a high gate voltage Vg is required to generate a large enough current to drive the pixel elements or other elements of the display. The drift of Vth reduces the effective driving voltage between gate and source, thereby reducing the source-drain current Ids, resulting in performance degradation. It is therefore highly desirable to maintain a low Vth during display use.

有几种公知方法可以减少和/或减慢阈值电压Vth的漂移。一种公知方法是采用高温退火减慢阈值电压的偏移，例如，在高温炉中把LCD显示器烘焙一预定时间。然而，在TFT—LCD显示器被装配好后再使它退火，那是不实际的，并且费用昂贵。There are several known methods to reduce and/or slow down the drift of the threshold voltage Vth . One known method is to slow down the threshold voltage shift by high temperature annealing, for example, baking the LCD display in a high temperature oven for a predetermined time. However, it is impractical and expensive to anneal the TFT-LCD display after it has been assembled.

控制ΔVth的另一种方法是减少所加的栅电压Vg，因为ΔVth正比于Vg。然而，由于非晶硅TFT的迁移率低，所以要求高的栅电压以便产生足够的电流来驱动其它的元件。所以，低的栅电压将导致于LCD显示器性能的大大降低。Another way to control ΔV th is to reduce the applied gate voltage Vg, because ΔV th is proportional to Vg. However, due to the low mobility of amorphous silicon TFTs, a high gate voltage is required in order to generate sufficient current to drive other elements. Therefore, a low gate voltage will result in greatly reduced performance of the LCD display.

第三种方法采用负偏压使正漂移Vth“返回”。此方法是在不激励TFT的扫描线时把栅压加到扫描线上。该方法为了使Vth的漂移减到最小而需要进行复杂的分析，这是因为对所加的负栅压的幅度和时间间隔有实际的限制。其原因是，对于每一帧，每个扫描线都必需在1/60秒内开启。这使得为了具有适当漂移的Vth值而需要的电路很复杂。A third method uses a negative bias to "return" a positive drift V th . This method is to apply gate voltage to the scanning line when the scanning line of the TFT is not excited. This approach requires complex analysis to minimize V th drift because of practical limitations on the magnitude and time interval of the applied negative gate voltage. The reason for this is that for each frame, each scan line must be on within 1/60 of a second. This complicates the circuitry required to have a properly shifted Vth value.

因此，本发明的目的是提供一种装置，用于改良非晶硅TFT—LCD显示器的阈值电压漂移的复原。It is therefore an object of the present invention to provide a device for improved recovery of threshold voltage drift of amorphous silicon TFT-LCD displays.

本发明的另一个目的是提供一种简单易行的装置，以便减小阈值电压的漂移。Another object of the present invention is to provide a simple and easy means to reduce the drift of the threshold voltage.

本发明的又一个目的是提供一种装置，用于在TFT—LCD显示器关闭和不被使用的同时复原阈值电压的漂移。Yet another object of the present invention is to provide a means for recovering the drift of the threshold voltage while the TFT-LCD display is turned off and not in use.

本发明提供一种用于复原薄膜非晶硅晶体管的阈值电压Vth的装置，所述晶体管淀积在一个显示器的衬底上，在使用期间将一个栅压Vg加到各晶体管上而引起Vth随时间而增加，该装置包括：The present invention provides an apparatus for restoring the threshold voltage Vth of thin-film amorphous silicon transistors deposited on a substrate of a display, during use a gate voltage Vg is applied to each transistor to cause V th increases over time, the device consists of:

检测部件，其可操作地与显示器相连接，用于检测何时显示器不在使用；detection means, operatively connected to the display, for detecting when the display is not in use;

电压产生部件，其可操作地与所述检测部件相连接，用于在不利用显示器时产生与Vg极性相反的电压Vg′，其中，voltage generating means, operatively connected to said detecting means, for generating a voltage Vg' opposite in polarity to Vg when the display is not utilized, wherein,

仅当显示器不用时，才把所述电压Vg′旋加到显示器晶体管的栅极上面，使Vth随时间减小，从而保持显示器的该次执行中有效的驱动电压。由此，保持对LCD显示器象素元件的有效驱动电压。Only when the display is not in use, the voltage Vg' is applied to the gate of the display transistor, so that Vth decreases with time, so as to maintain the effective driving voltage in this execution of the display. Thus, an effective drive voltage to the pixel elements of the LCD display is maintained.

结合下列附图将更清楚地理解本发明的这些和其它目的。These and other objects of the present invention will be more clearly understood in conjunction with the following drawings.

图1是TFT阈值电压漂移与所加栅电压的曲线图。Figure 1 is a graph of TFT threshold voltage shift versus applied gate voltage.

图2是工作88小时后TFT阈值电压漂移的曲线图。Fig. 2 is a graph of TFT threshold voltage drift after working for 88 hours.

图3是施加负20伏电压16小时后TFT阈值电压复原的曲线图。FIG. 3 is a graph showing recovery of TFT threshold voltage after 16 hours of negative 20 volts application.

图4是本发明用于控制Vth的装置的方框图。Fig. 4 is a block diagram of the apparatus for controlling V th of the present invention.

图2表示对一非晶硅体管的栅极加30V交流电，大约经过88小时后，典型的阈值电压漂移情况。由图2可见，在这88小时的使用期间，Vth漂移大约为5伏。Figure 2 shows the typical threshold voltage drift after about 88 hours of applying 30V AC to the gate of an amorphous silicon transistor. It can be seen from Figure 2 that the V th drift was about 5 volts during this 88 hours of use.

图3是本发明提供的阈值电压复原的曲线图。图3表示在关闭TFT—LCD显示器期间，TFT的栅极加负20伏电压大约16小时后，Vth复原到离初始Vth大约不超出0.9伏，如果在较长时间和/或把较高负电压施加到栅电极上，则可使阈值电压完全复原到初始Vth。FIG. 3 is a graph of threshold voltage recovery provided by the present invention. Figure 3 shows that when the TFT-LCD display is turned off, after a negative 20 volt voltage is applied to the gate of the TFT for about 16 hours, the V th recovers to about 0.9 volts from the initial V th . Applying a negative voltage to the gate electrode can completely restore the threshold voltage to the initial V th .

可以根据显示器的用途设计加到TFT器件栅极的负DC电压的幅度和持续时间。The magnitude and duration of the negative DC voltage applied to the gate of the TFT device can be designed according to the application of the display.

图4公开了本发明的复原电路的方框图。示出了其上淀积了薄膜晶体管1 2的TFT玻璃衬底10。衬底10上还表示出有一个、温度传感器14，最好为热电偶、二极管或者电阻传感器，它可以直接淀积在衬底10上，也可以固定在显示器中，以使该传感器与衬底10相邻接。电压产生电路16连接到TFT12的栅极上。计时器、温度传感器和检测电路18连接到温度传感器14和电压产生电路16上，用于控制电路16的运行。Figure 4 discloses a block diagram of the recovery circuit of the present invention. A TFT glass substrate 10 on which a thin film transistor 12 is deposited is shown. Also shown on the substrate 10 is a temperature sensor 14, preferably a thermocouple, diode or resistance sensor, which can be directly deposited on the substrate 10, or fixed in the display, so that the sensor is in contact with the substrate. 10 adjacent. The voltage generating circuit 16 is connected to the gate of the TFT 12 . The timer, temperature sensor and detection circuit 18 is connected to the temperature sensor 14 and the voltage generating circuit 16 for controlling the operation of the circuit 16 .

提供一电路20，用于在使用TFT12时指示检测电路18。电路20包括一正常开启的继电器22和on/OFF开关24。当开启开关24时，使常开继电器22闭合，由此能使检测电路18激励计时器开始检测LCD显示器的使用。也就是说，检测电路18检测继电器22何时开启。于是，电路18使电路16能仅当它检测到LCD显示器处于不工作状态时，把一电压Vg′加到TFT12的栅极上，以便引起Vth在与LCD显示器处于工作状态时由Vg所引起的漂移方向相反的方向漂移。A circuit 20 is provided for instructing the detection circuit 18 when the TFT 12 is used. Circuit 20 includes a normally open relay 22 and on/off switch 24 . When the switch 24 is turned on, the normally open relay 22 is closed, thereby enabling the detection circuit 18 to activate the timer to start detecting the use of the LCD display. That is, the detection circuit 18 detects when the relay 22 is turned on. Thus, the circuit 18 enables the circuit 16 to apply a voltage Vg' to the gate of the TFT 12 only when it detects that the LCD display is in an inoperative state, so as to cause Vth to be caused by Vg when the LCD display is in an active state. Drift in the opposite direction to the drift direction.

在利用本发明期间，可以以固定的时间和固定的幅度简单地把电压Vg′施加到非晶硅晶体管12的栅极上面，以便稳定地每当LCD处于关闭状态就使电压阈值的漂移偏移。During utilization of the present invention, the voltage Vg' can simply be applied to the gate of the amorphous silicon transistor 12 for a fixed time and a fixed amplitude to stably offset the drift of the voltage threshold whenever the LCD is off. .

本发明的新颖方法需要下列步骤：检测LCD显示器处于关闭状态的时间的步骤；仅仅当显示器处于关态时，把一负偏压加到TFT晶体管的栅极以便复原LCD显示器在工作状态期间产生的阈值电压漂移。该方法还包括下述步骤：在LCD显示器处于关闭状态一预定的时间周期内把恒定值的负电压加到TFT晶体管的栅极上面。The novel method of the present invention requires the following steps: a step of detecting when the LCD display is in the off state; only when the display is in the off state, applying a negative bias voltage to the gate of the TFT transistor in order to restore the LCD display generated during the active state threshold voltage drift. The method further includes the step of: applying a negative voltage of constant value to the gate of the TFT transistor for a predetermined period of time when the LCD display is in the off state.

在另一个实施例中，该方法还包括下述步骤：按下述方程式把一负电压加到TFT晶体管的栅极持续一段时间In another embodiment, the method further comprises the step of: applying a negative voltage to the gate of the TFT transistor for a period of time according to the following equation

ΔVth＝Aexp(-Ea/KT)(logt)αVβ ΔV th = Aexp(-Ea/KT)(logt) α V β

如此，公开了涉及非晶硅TFT器件的关于使阈值电压漂移复原的方法和装置。特别是在把该器件用于数据驱动器和扫描驱动器电路或者象素开关元件中的LCD显示器时。仅当LCD显示器处于关态或者未被使用时，这种新颖的方法和装置利用LCD显示部件中本身产生的负电压信号并把该负电压信号加到非晶硅TFT的栅极上。这种方法和装置将使器件的阈值漂移复原，从而增强了运行能力和延长了显示器的使用寿命。Thus, disclosed are methods and apparatus relating to recovery of threshold voltage drift involving amorphous silicon TFT devices. Especially when using the device in LCD displays in data driver and scan driver circuits or pixel switching elements. The novel method and apparatus utilizes a negative voltage signal generated in the LCD display unit itself and applies the negative voltage signal to the gate of the amorphous silicon TFT only when the LCD display is off or not in use. The method and apparatus will restore the threshold drift of the device, thereby enhancing the operation capability and prolonging the service life of the display.

但是，在更高级的应用方面，为了更精确地计算需要加到晶体12上的电压Vg的幅度和时间，能通过其计算值包括衬底10的温度的电路18来计算LCD显示器处于关态时加于其上的适当电压和所需的时间。上述计算在诸如HD—TV投影等应用中可能是必需的，这种应用中TFT被暴露于相当高的温度下。However, in more advanced applications, in order to more accurately calculate the magnitude and time of the voltage Vg that needs to be applied to the crystal 12, the circuit 18 whose calculated value includes the temperature of the substrate 10 can be used to calculate when the LCD display is in the off state. Appropriate voltage applied to it and required time. The above calculations may be necessary in applications such as HD-TV projection, where TFTs are exposed to relatively high temperatures.

Claims (8)

1. threshold voltage V who is used to restore the thin film amorphous silicon transistor (12) on the substrate (10) that is deposited on display ThDevice, and causing V ThBetween the operating period of Zeng Jiaing gate voltage Vg is added on each transistor in time, this device comprises:
Be operably connected to the detection part (18) on the display, be used to detect the time of not using display;
Be operably connected to the voltage production part (16) of detection part, be used for when not using display, produce and the opposite polarity voltage Vg ' of Vg, wherein,
Only when display does not use, voltage Vg ' is added on the transistor gate of display, is used to make V ThReduce in time, keep thus this time of display carry out in effective driving voltage.
2. according to a kind of device of claim 1, wherein:
Detection part (18) comprises and is used to detect the parts that display (10) is in the time quantum of user mode; And
Only in obsolete a period of time of display voltage Vg ' is added on transistor (12) grid, the amplitude of described voltage is proportional to the time quantum that display is in user mode.
3. according to a kind of device of claim 2, wherein:
Pick-up unit (18) comprises the parts that are used for detecting its temperature in display (10) is in time of user mode; And
The amplitude that the temperature of voltage Vg ' when being in user mode with display is directly proportional applies a period of time.
4. according to the device of claim 3, wherein, temperature detection part (18) comprises that one is deposited on the temperature sensor (14) on the display substrate (10).
5. according to the device of claim 3, wherein, temperature detection part (18) comprises the temperature sensor with the display substrate adjacency.
6. according to the device of claim 5, wherein, temperature sensor (14) is to be selected from a kind of in one group that is made of thermopair, diode and electric resistance sensor.
7. according to the device of claim 1, wherein, voltage production part (16) comprises battery supply.
8. according to any one described device in the aforementioned claim, wherein, display (10) is a LCD.
CN 94191947 1993-04-30 1994-05-10 Device for restoring threshold voltage drift of amorphous silicon thin film transistor device Pending CN1122165A (en)

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