CN202917146U - Pixel circuit and display apparatus - Google Patents

Abstract

Translated fromChinese

本实用新型公开了一种像素电路和显示装置，涉及显示领域，可有效地补偿耗尽型或增强型驱动TFT阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异。所述像素电路包括：发光元件；驱动薄膜晶体管，漏极输入电源电压信号；第一薄膜晶体管，漏极与驱动薄膜晶体管的源极相连，源极与发光元件相连，栅极接收第一控制信号；第二薄膜晶体管，源极接收数据信号，漏极与驱动薄膜晶体管栅极相连，栅极接收扫描信号；第三薄膜晶体管，源极接收参考电压信号，栅极接收扫描信号；第四薄膜晶体管，源极与第三薄膜晶体管漏极相连，漏极与驱动薄膜晶体管的栅极及第二薄膜晶体管漏极相连，栅极接收第二控制信号；电容。

The utility model discloses a pixel circuit and a display device, which relate to the display field and can effectively compensate the non-uniformity and drift of the threshold voltage of a depletion-type or enhanced-type driving TFT, and the current difference caused by the non-uniformity of an OLED. The pixel circuit includes: a light emitting element; a driving thin film transistor, the drain of which inputs a power supply voltage signal; a first thin film transistor, the drain of which is connected to the source of the driving thin film transistor, the source is connected to the light emitting element, and the gate receives the first control signal ; The second thin film transistor, the source receives the data signal, the drain is connected to the gate of the driving thin film transistor, and the gate receives the scanning signal; the third thin film transistor, the source receives the reference voltage signal, and the gate receives the scanning signal; the fourth thin film transistor , the source is connected to the drain of the third thin film transistor, the drain is connected to the gate of the driving thin film transistor and the drain of the second thin film transistor, and the gate receives the second control signal; a capacitor.

Description

Translated fromChinese

像素电路和显示装置Pixel circuit and display device

技术领域technical field

本实用新型涉及显示领域，尤其涉及一种像素电路和显示装置。 The utility model relates to the display field, in particular to a pixel circuit and a display device. the

背景技术Background technique

有机发光二极管(Organic Light Emitting Diode，OLED)为电流驱动主动发光型器件，因其具有自发光、快速响应、宽视角和可制作在柔性衬底上等独特特点，以OLED为基础的有机发光显示预计今后几年将成为显示领域的主流。 Organic Light Emitting Diode (OLED) is a current-driven active light-emitting device, because of its unique characteristics such as self-illumination, fast response, wide viewing angle and can be fabricated on a flexible substrate, OLED-based organic light-emitting display It is expected to become the mainstream in the display field in the next few years. the

有机发光显示的每个显示单元，都是由OLED构成的，有机发光显示按驱动方式可分为有源有机发光显示和无源有机发光显示，其中有源有机发光显示是指每个OLED都由薄膜晶体管(Thin Film Transistor，TFT)电路来控制流过OLED的电流，OLED和用于驱动OLED的TFT电路构成像素电路。 Each display unit of an organic light-emitting display is composed of OLEDs. According to the driving method, organic light-emitting displays can be divided into active organic light-emitting displays and passive organic light-emitting displays. Active organic light-emitting displays mean that each OLED is composed of A thin film transistor (Thin Film Transistor, TFT) circuit is used to control the current flowing through the OLED, and the OLED and the TFT circuit used to drive the OLED constitute a pixel circuit. the

一种典型的像素电路如图1所示，包括2个TFT晶体管，1个电容和1个OLED，其中开关管T2将数据线上的电压传输到驱动管T1的栅极，驱动管T1将这个数据电压转化为相应的电流，供给OLED器件，其电流可表示为： A typical pixel circuit is shown in Figure 1, including 2 TFT transistors, 1 capacitor and 1 OLED, in which the switch tube T2 transmits the voltage on the data line to the gate of the drive tube T1, and the drive tube T1 transfers this The data voltage is converted into the corresponding current, which is supplied to the OLED device, and its current can be expressed as:

${\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>OLED</span>OLED</span>}}<span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>2</span>2</span>}}{\mathrm{<span><span>\&mu;</span>\&mu;</span>}}_{\mathrm{<span><span>n</span>no</span>}}<span><span>\&CenterDot;</span>\&CenterDot;</span>\mathrm{<span><span>Cox</span>Cox</span>}<span><span>\&CenterDot;</span>\&CenterDot;</span>\frac{\mathrm{<span><span>W</span>W</span>}}{\mathrm{<span><span>L</span>L</span>}}<span><span>\&CenterDot;</span>\&Center\; Dot;</span>{<span><span>(</span>(</span>\mathrm{<span><span>Vgs</span>Vgs</span>}<span><span>-</span>-</span>\mathrm{<span><span>Vth</span>Vth</span>}<span><span>)</span>)</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>2</span>2</span>}}{\mathrm{<span><span>\&mu;</span>\&mu;</span>}}_{\mathrm{<span><span>n</span>no</span>}}<span><span>\&CenterDot;</span>\&CenterDot;</span>\mathrm{<span><span>Cox</span>Cox</span>}<span><span>\&CenterDot;</span>\&Center\; Dot;</span>\frac{\mathrm{<span><span>W</span>W</span>}}{\mathrm{<span><span>L</span>L</span>}}<span><span>\&CenterDot;</span>\&CenterDot;</span>{<span><span>(</span>(</span>\mathrm{<span><span>Vdata</span>Vdata</span>}<span><span>-</span>-</span>\mathrm{<span><span>Voled</span>Voled</span>}<span><span>-</span>-</span>\mathrm{<span><span>Vth</span>Vth</span>}<span><span>)</span>)</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>)</span>)</span>$

其中，Vgs为驱动管T1栅极和源极之间的电势差，μ_n为载流子迁移率，Cox为栅绝缘层电容，W/L为晶体管宽长比，Vdata为数据电压，Voled为OLED的工作电压，Vth为驱动管T1的阈值电压，由上式可知：如果不同像素单元之间的Vth不同或者Vth随时间发生漂移，则流过OLED的电流存在差异，影响显示效果，另外，OLED器件的非均匀性引起OLED工作电压不同时，也会导致电流差异。 Among them, Vgs is the potential difference between the gate and source of the drive transistor T1, μ_n is the carrier mobility, Cox is the capacitance of the gate insulating layer, W/L is the transistor width-to-length ratio, Vdata is the data voltage, and Voled is the OLED Vth is the threshold voltage of the driving tube T1. It can be known from the above formula: if the Vth of different pixel units is different or Vth drifts with time, there will be differences in the current flowing through the OLED, which will affect the display effect. In addition, the OLED When the non-uniformity of the device causes the OLED operating voltage to be different, it will also cause the current difference.

目前，用于补偿Vth非均匀性、漂移和OLED非均匀性造成的电流差异的像素电路有多种，但通常都采用将驱动TFT置为如图2所示的二极管连接的方式来实现，而这种结构只适用于增强型的TFT，而对于耗尽型TFT，因当Vgs＝0时仍然可以导通，因此TFT储存的电压中不包含阈值电压Vth的信息，所以对于耗尽型TFT，现有像素电路无法进行补偿阈值电压的非均匀性造成的电流差异。 At present, there are various pixel circuits for compensating the current difference caused by Vth non-uniformity, drift and OLED non-uniformity, but they are usually implemented by placing the driving TFT in a diode connection as shown in Figure 2, and This structure is only applicable to enhancement-type TFTs, but for depletion-type TFTs, because it can still be turned on when Vgs=0, the voltage stored in the TFT does not contain the information of the threshold voltage Vth, so for depletion-type TFTs, Existing pixel circuits cannot compensate current differences caused by non-uniformity of threshold voltages. the

实用新型内容Utility model content

本实用新型所要解决的技术问题在于提供一种像素电路和显示装置，可以有效地补偿耗尽型或增强型TFT驱动管的阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异，从而提升显示装置的显示效果。 The technical problem to be solved by the utility model is to provide a pixel circuit and a display device, which can effectively compensate the non-uniformity and drift of the threshold voltage of the depletion-type or enhancement-type TFT drive tube, and the current difference caused by the non-uniformity of the OLED, Thus, the display effect of the display device is improved. the

为达到上述目的，本实用新型的实施例采用如下技术方案： In order to achieve the above object, the embodiments of the present utility model adopt the following technical solutions:

一种像素电路，其特征在于，包括： A pixel circuit, characterized in that, comprising:

发光元件； light emitting element;

用于驱动所述发光元件的驱动薄膜晶体管，其漏极输入电源电压信号； A driving thin film transistor for driving the light-emitting element, the drain of which is input with a power supply voltage signal;

第一薄膜晶体管，其源极与所述发光元件相连接，其漏极与所述驱动薄膜晶体管的源极相连接，其栅极接收第一控制信号； The source of the first thin film transistor is connected to the light-emitting element, the drain is connected to the source of the driving thin film transistor, and the gate receives the first control signal;

第二薄膜晶体管，其源极接收数据信号，其漏极与所述驱动薄膜晶体管的栅极相连接，其栅极接收扫描信号； The second thin film transistor, its source receives the data signal, its drain is connected to the gate of the driving thin film transistor, and its gate receives the scan signal;

第三薄膜晶体管，其源极接收参考电压信号，其栅极接收所述扫描信号； The third thin film transistor, its source receives the reference voltage signal, and its gate receives the scanning signal;

第四薄膜晶体管，其源极与所述第三薄膜晶体管的漏极相连接，其漏极与所述驱动薄膜晶体管的栅极及所述第二薄膜晶体管的漏极相连接，其栅极接收第二控制信号； The fourth thin film transistor, its source is connected to the drain of the third thin film transistor, its drain is connected to the gate of the driving thin film transistor and the drain of the second thin film transistor, and its gate receives second control signal;

电容，所述电容的一极板连接至第一节点，另一极板连接至第二节点，所述第一节点为所述第一薄膜晶体管漏极与所述驱动薄膜晶体管源极的连接点，所述第二节点为所述第四薄膜晶体管源极与所述第三薄膜晶体管漏极的连接点。 a capacitor, one plate of the capacitor is connected to the first node, and the other plate is connected to the second node, and the first node is the connection point between the drain of the first thin film transistor and the source of the driving thin film transistor , the second node is a connection point between the source of the fourth thin film transistor and the drain of the third thin film transistor. the

所述驱动薄膜晶体管为N型薄膜晶体管。 The driving thin film transistor is an N-type thin film transistor. the

可选地，所述薄膜晶体管为耗尽型薄膜晶体管，或者增强型薄膜晶体管。 Optionally, the thin film transistor is a depletion type thin film transistor, or an enhancement type thin film transistor. the

可选地，所述发光元件为有机发光二极管。 Optionally, the light emitting element is an organic light emitting diode. the

本实用新型还提供一种显示装置，设置所述的任一的像素电路。 The utility model also provides a display device, which is provided with any of the pixel circuits described above. the

本实用新型提供的像素电路和显示装置，将电容的一端连接至驱动薄膜晶体管的源极(第一节点)，另一端连接至驱动薄膜晶体管的栅极和参考电压，并通过第四薄膜晶体管和第三薄膜晶体管分别控制电容是接通驱动薄膜晶体管的栅极还是参考电压。每帧图像显示过程都包括：预充、补偿和保持发光三个阶段。预充阶段：第一薄膜晶体管导通，第一节点储存的电荷释放，使第一节点的电压拉低；补偿阶段：第三、五薄膜晶体管导通，对第一节点充电，结果第一节点的电压中包含驱动薄膜晶体管阈值电压的信息；保持发光阶段：第四薄膜晶体管导通，电容连接在至驱动薄膜晶体管的栅源极之间，驱动薄膜晶体管的栅源电压保持不变，驱动薄膜晶体管驱使发光元件发光，其电流大小与驱动薄膜晶体管的阈值电压、以及发光元件两端电压无关，因此，可有效地补偿耗尽型或增强型TFT驱动管的阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异，从而提升显示装置的显示效果。 In the pixel circuit and the display device provided by the utility model, one end of the capacitor is connected to the source (first node) of the driving thin film transistor, and the other end is connected to the gate of the driving thin film transistor and the reference voltage, and through the fourth thin film transistor and The third thin film transistor respectively controls whether the capacitor is connected to the gate of the driving thin film transistor or the reference voltage. The image display process of each frame includes three stages: pre-charging, compensation and maintaining light emission. Pre-charging stage: the first thin film transistor is turned on, and the charge stored in the first node is released, so that the voltage of the first node is pulled down; Compensation stage: the third and fifth thin film transistors are turned on, charging the first node, and as a result, the first node The voltage contains the information of the threshold voltage of the driving thin film transistor; keep the light emitting stage: the fourth thin film transistor is turned on, the capacitor is connected to the gate source of the driving thin film transistor, the gate source voltage of the driving thin film transistor remains unchanged, and the driving thin film transistor The transistor drives the light-emitting element to emit light, and its current has nothing to do with the threshold voltage of the driving thin film transistor and the voltage across the light-emitting element. Therefore, it can effectively compensate for the non-uniformity and drift of the threshold voltage of the depletion-type or enhancement-type TFT drive tube, and The current difference caused by OLED non-uniformity improves the display effect of the display device. the

附图说明Description of drawings

图1为现有像素电路的结构示意图； FIG. 1 is a schematic structural diagram of an existing pixel circuit;

图2(a)、(b)分别为增强型TFT和耗尽型TFT补偿方法原理图； Figure 2(a) and (b) are the schematic diagrams of enhancement TFT and depletion TFT compensation methods respectively;

图3为本实用新型实施例提供的像素电路示意图一； Fig. 3 is the first schematic diagram of the pixel circuit provided by the embodiment of the utility model;

图4为本实用新型实施例中像素电路的控制时序图； Fig. 4 is the control timing diagram of the pixel circuit in the utility model embodiment;

图5为本实用新型实施例中像素电路的驱动方法流程图； Fig. 5 is the driving method flowchart of pixel circuit in the utility model embodiment;

图6为本实用新型实施例中提供的像素电路示意图二； Fig. 6 is the second schematic diagram of the pixel circuit provided in the embodiment of the utility model;

图7为本实用新型实施例中另一像素电路的示意图； Fig. 7 is the schematic diagram of another pixel circuit in the utility model embodiment;

图8为本实用新型实施例中另一像素电路的控制时序图。 FIG. 8 is a control timing diagram of another pixel circuit in the embodiment of the present invention. the

具体实施方式Detailed ways

本实用新型实施例提供一种像素电路和显示装置，可以有效地补偿耗尽型或增强型TFT驱动管的阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异，从而提升显示装置的显示效果。 The embodiment of the utility model provides a pixel circuit and a display device, which can effectively compensate the non-uniformity and drift of the threshold voltage of the depletion-type or enhancement-type TFT drive tube, and the current difference caused by the non-uniformity of the OLED, thereby improving the display device. display effect. the

下面结合附图对本实用新型实施例进行详细描述。此处所描述的具体实施方式仅仅用以解释本实用新型，并不用于限定本实用新型。 The embodiment of the utility model will be described in detail below in conjunction with the accompanying drawings. The specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model. the

需要说明的是，对于液晶显示领域的晶体管来说，漏极和源极没有明确的区别，因此本实用新型实施例中所提到的晶体管的源极可以为晶体管的漏极，晶体管的漏极也可以为晶体管的源极。 It should be noted that for transistors in the field of liquid crystal display, there is no clear distinction between the drain and the source, so the source of the transistor mentioned in the embodiment of the present invention can be the drain of the transistor, and the drain of the transistor It can also be the source of a transistor. the

实施例 Example

本实用新型实施例提供一种像素电路，如图3所示，该电路包括： The embodiment of the utility model provides a pixel circuit, as shown in Figure 3, the circuit includes:

发光元件； light emitting element;

用于驱动发光元件的驱动薄膜晶体管T5，其漏极输入电源电压信号ELVDD； The driving thin film transistor T5 used to drive the light-emitting element, its drain input power supply voltage signal ELVDD;

第一薄膜晶体管T1，其源极与发光元件相连接，其漏极与驱动薄膜晶体管T5的源极相连接，其栅极接收第一控制信号EM； The source of the first thin film transistor T1 is connected to the light-emitting element, its drain is connected to the source of the driving thin film transistor T5, and its gate receives the first control signal EM;

第二薄膜晶体管T2，其源极接收数据信号DATA，其漏极与驱动薄膜晶体管T5的栅极相连接，其栅极接收扫描信号SCAN； The second thin film transistor T2, its source receives the data signal DATA, its drain is connected to the gate of the driving thin film transistor T5, and its gate receives the scanning signal SCAN;

第三薄膜晶体管T3，其源极接收参考电压信号VREF，其栅极接收扫描信号SCAN； The third thin film transistor T3, its source receives the reference voltage signal VREF, and its gate receives the scanning signal SCAN;

第四薄膜晶体管T4，其源极与第三薄膜晶体管T3的漏极相连接，其漏极与驱动薄膜晶体管T5的栅极及第二薄膜晶体管T2的漏极相连接，其栅极接收第二控制信号PR； The source of the fourth thin film transistor T4 is connected to the drain of the third thin film transistor T3, the drain is connected to the gate of the driving thin film transistor T5 and the drain of the second thin film transistor T2, and the gate receives the second control signal PR;

电容C1，电容的一极板连接至第一节点N1，另一极板连接至第二节点N2，所述第一节点N1为第一薄膜晶体管T1漏极与驱动薄膜晶体管T5源极的连接点，所述第二节点N2为第四薄膜晶体管T4源极与第三薄膜晶体管T3漏极的连接点。 Capacitor C1, one plate of the capacitor is connected to the first node N1, and the other plate of the capacitor is connected to the second node N2, the first node N1 is the connection point between the drain of the first thin film transistor T1 and the source of the driving thin film transistor T5 , the second node N2 is a connection point between the source of the fourth thin film transistor T4 and the drain of the third thin film transistor T3. the

上面本实用新型所述像素电路由5个薄膜晶体管，1个电容组成。其中，优选地，驱动薄膜晶体管T5为N型薄膜晶体管，此外，驱动薄膜晶体管T5既可以选择耗尽型也可以选择增强型。本实用新型的优越性就在于，本实用新型补偿电路中的驱动薄膜晶体管T5无论选择增强型还是耗尽型，驱动管的阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异均能得到较好的补偿。另外，除驱动薄膜晶体管T5之外的其余薄膜晶体管只起到开关作用，N型或P型都可以，耗尽型或增强型也都可以，不做限定。 The above described pixel circuit of the utility model is composed of 5 thin film transistors and 1 capacitor. Wherein, preferably, the driving thin film transistor T5 is an N-type thin film transistor. In addition, the driving thin film transistor T5 can be selected as either a depletion type or an enhancement type. The advantage of the utility model is that, regardless of whether the driving thin film transistor T5 in the compensation circuit of the utility model chooses the enhancement type or the depletion type, the non-uniformity and drift of the threshold voltage of the driving tube, and the current difference caused by the non-uniformity of the OLED are uniform. get better compensation. In addition, the other thin film transistors except the driving thin film transistor T5 only function as switches, either N-type or P-type, depletion-type or enhancement-type, and are not limited. the

因此，在本实用新型实施例中，所述各薄膜晶体管的具体型号(即各薄膜晶体管是N型或P型，是耗尽型或增强型)并不能用于限定补偿电路，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，对各薄膜晶体管的选型变化及因选型变化产生的连接变动，也在本实用新型的保护范围之内。 Therefore, in the embodiment of the present utility model, the specific models of the thin film transistors (that is, whether each thin film transistor is N-type or P-type, depletion-type or enhancement-type) cannot be used to define the compensation circuit. As far as technical personnel are concerned, on the premise of not paying creative labor, the type selection change of each thin film transistor and the connection change caused by the type selection change are also within the protection scope of the present invention. the

图3中所示5个薄膜晶体管(T1～T5)均为N型薄膜晶体管，为便于制造，优选地，采用相同规格的N型薄膜晶体管。其中，可选地，驱动薄膜晶体管T5可以是N型耗尽型薄膜晶体管，也可以是N型增强型薄膜晶体管(具体补偿过程见下文)。其中，可选地，所述发光元件为有机发光二极管(OLED)。 The five thin film transistors ( T1 - T5 ) shown in FIG. 3 are all N-type thin film transistors. For ease of manufacture, preferably, N-type thin film transistors of the same specification are used. Wherein, optionally, the driving thin film transistor T5 may be an N-type depletion-type thin-film transistor, or an N-type enhancement-type thin-film transistor (see below for the specific compensation process). Wherein, optionally, the light emitting element is an organic light emitting diode (OLED). the

本实施例提供的像素电路，可以有效地补偿耗尽型或增强型TFT驱动管的阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异(具体原理性阐述见下文)，从而提升显示装置的显示效果，下面对该像素电路的具体工作过程进行详细的原理性阐述。 The pixel circuit provided by this embodiment can effectively compensate the non-uniformity and drift of the threshold voltage of the depletion-type or enhancement-type TFT drive tube, and the current difference caused by the non-uniformity of the OLED (see below for the specific principle), thereby improving For the display effect of the display device, the specific working process of the pixel circuit will be explained in detail below. the

上述像素电路采用如图4所示控制时序，其每帧图像显示过程都包 括：预充(I)、补偿(II)和保持发光(III)三个阶段，如图5所示，具体包括： The above-mentioned pixel circuit adopts the control timing as shown in Figure 4, and the image display process of each frame includes: pre-charging (I), compensation (II) and three stages of maintaining light emission (III), as shown in Figure 5, specifically including :

步骤101、预充阶段(I)，扫描信号SCAN开启第二薄膜晶体管T2和第三薄膜晶体管T3，数据信号DATA输入驱动薄膜晶体管T5的栅极，使驱动薄膜晶体管T5关断，同时第二控制信号PR关断第四薄膜晶体管T4，第一控制信号EM开启第一薄膜晶体管T1，第一节点N1储存的电荷通过发光元件OLED释放，第一节点N1的电压降低。 Step 101, precharge phase (1), the scan signal SCAN opens the second thin film transistor T2 and the third thin film transistor T3, and the gate of the data signal DATA inputs the driving thin film transistor T5, makes the driving thin film transistor T5 turn off, and the second control The signal PR turns off the fourth thin film transistor T4, the first control signal EM turns on the first thin film transistor T1, the charge stored in the first node N1 is released through the light emitting element OLED, and the voltage of the first node N1 decreases. the

在预充阶段(I)，扫描信号SCAN、第一控制信号EM为高电平，第二控制信号PR为低电平，数据信号DATA输出一个低压信号(VL)，此时5个薄膜晶体管中，T2、T3和T1导通，T4关断，数据信号DATA中的低压信号(VL)使驱动薄膜晶体管T5关断，第一节点N1储存的电荷通过发光元件OLED释放(其实质为T1导通，电容C1放电)，第一节点N1的电压降低，直至第一节点N1的电压达到VL-Vth。其中，VL为驱动薄膜晶体管T5此时的栅极电压，Vth为薄膜晶体管T5的阈值电压。为保证能加载上数据信号，设计时要保证VL-Vth的电压值低于最低灰阶的驱动电压。 In the pre-charge phase (I), the scanning signal SCAN and the first control signal EM are at high level, the second control signal PR is at low level, and the data signal DATA outputs a low-voltage signal (VL). At this time, among the five thin film transistors , T2, T3 and T1 are turned on, T4 is turned off, the low-voltage signal (VL) in the data signal DATA turns off the driving thin film transistor T5, and the charge stored in the first node N1 is released through the light-emitting element OLED (its essence is that T1 is turned on , the capacitor C1 is discharged), the voltage of the first node N1 decreases until the voltage of the first node N1 reaches VL-Vth. Wherein, VL is the gate voltage of the driving thin film transistor T5 at this time, and Vth is the threshold voltage of the thin film transistor T5. In order to ensure that data signals can be loaded, it is necessary to ensure that the voltage value of VL-Vth is lower than the driving voltage of the lowest gray scale during design. the

在预充阶段(I)过程中会有电荷流经发光元件OLED，会对发光元件产生影响，为了确保只有在发光阶段有电流通过OLED，可选地，如图6所示，可以在OLED的两边增加一薄膜晶体管(T6)及控制该薄膜晶体管开启的控制信号(EM2)，该薄膜晶体管(T6)的漏极接地，在预充阶段通过控制信号(EM2)控制该薄膜晶体管(T6)的开启释放第一结点N1储存的电荷，从而提高OLED使用寿命。 During the pre-charging phase (I), there will be charges flowing through the light-emitting element OLED, which will have an impact on the light-emitting element. In order to ensure that only in the light-emitting phase, there is current through the OLED. Optionally, as shown in Figure 6, the OLED can be A thin-film transistor (T6) and a control signal (EM2) for controlling the opening of the thin-film transistor are added on both sides, and the drain of the thin-film transistor (T6) is grounded. Turning on releases the charge stored in the first node N1, thereby improving the service life of the OLED. the

步骤102、补偿阶段(II)，第二薄膜晶体管T2和第三薄膜晶体管T3继续保持导通状态，数据信号DATA输入驱动薄膜晶体管的栅极，开启驱动薄膜晶体管T5，同时第四薄膜晶体管T4继续保持关断状态，第一控制信号EM关断第一薄膜晶体管T1，电源电压信号ELVDD通过驱动薄膜晶体管T5向第一节点N1充电，使第一节点N1的电压升高； Step 102, compensation phase (II), the second thin film transistor T2 and the third thin film transistor T3 continue to maintain the on state, the data signal DATA is input to the gate of the driving thin film transistor, and the driving thin film transistor T5 is turned on, while the fourth thin film transistor T4 continues to Keep the off state, the first control signal EM turns off the first thin film transistor T1, and the power supply voltage signal ELVDD charges the first node N1 by driving the thin film transistor T5, so that the voltage of the first node N1 increases;

补偿阶段(II)，扫描信号SCAN仍为高电平，第二、第三薄膜晶体管T2、T3继续保持导通状态；第二控制信号PR仍为低电平，第四薄膜晶体管T4继续保持关断状态；第一控制信号EM为低电平，第一薄膜晶体管T1关断；数据信号DATA为当前图像帧的数据电压(灰阶驱动电压)Vdata，输入驱动薄膜晶体管T5的栅极，驱动薄膜晶体管T5的第一节点N1电压保持预充阶段(I)结束时的电压VL-Vth，驱动薄膜晶体管T5的栅源电压Vgs＝Vdata+Vth-VL，由于Vdata＞VL，因此Vgs＞Vth驱动薄膜晶体管T5开启，此时，电源电压信号ELVDD通过驱动薄膜晶体管T5向第一节点N1充电(其实质是T5导通，向电容C1充电)，直至第一节点N1的电压等于Vdata-Vth。注意这一补偿过程与Vth的正负无关，因为ELVDD＞Vdata，驱动薄膜晶体管T5源极会一直充电到Vdata-Vth，此时驱动薄膜晶体管T5的栅源电压Vgs＝Vdata-(Vdata-Vth)＝Vth，使得T5处于临界导通点，因此，这里无论驱动薄膜晶体管T5是耗尽型还是增强型，第一节点N1的电压均可达到Vdata-Vth，所以本实用新型提供的像素电路对于增强型还是耗尽型的驱动TFT都适用，都可有效地补偿驱动TFT阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异，适用性更广。 In the compensation stage (II), the scanning signal SCAN is still at a high level, and the second and third thin film transistors T2 and T3 continue to be turned on; the second control signal PR is still at a low level, and the fourth thin film transistor T4 continues to be turned off. off state; the first control signal EM is low level, and the first thin film transistor T1 is turned off; the data signal DATA is the data voltage (gray-scale driving voltage) Vdata of the current image frame, which is input to the gate of the driving thin film transistor T5 to drive the thin film The first node N1 voltage of the transistor T5 maintains the voltage VL-Vth when the precharge phase (I) ends, and the gate-source voltage Vgs=Vdata+Vth-VL of the driving thin film transistor T5, because Vdata>VL, so Vgs>Vth drives the thin film The transistor T5 is turned on. At this time, the power supply voltage signal ELVDD is charged to the first node N1 by driving the TFT T5 (in essence, T5 is turned on to charge the capacitor C1) until the voltage of the first node N1 is equal to Vdata-Vth. Note that this compensation process has nothing to do with the positive or negative of Vth, because ELVDD>Vdata, the source of the driving thin film transistor T5 will always be charged to Vdata-Vth, at this time the gate-source voltage of the driving thin film transistor T5 Vgs=Vdata-(Vdata-Vth) =Vth, so that T5 is at the critical conduction point, therefore, here no matter whether the driving thin film transistor T5 is depletion type or enhancement type, the voltage of the first node N1 can reach Vdata-Vth, so the pixel circuit provided by the utility model is useful for enhancing Both depletion-type and depletion-type driving TFTs are applicable, and both can effectively compensate the non-uniformity and drift of the threshold voltage of the driving TFT, as well as the current difference caused by the non-uniformity of the OLED, and the applicability is wider. the

补偿阶段(II)结束时，电容C1的电荷量Q为： At the end of the compensation phase (II), the charge Q of the capacitor C1 is:

Q＝C(V2-V1)＝C·(VREF+Vth-Vdata)-----------(2) Q＝C(V2-V1)＝C·(VREF+Vth-Vdata)-----------(2) 

其中，V1为第一节点N1此时的电压，等于Vdata-Vth；V2为第二节点N2此时的电压，等于参考电压VREF。 Wherein, V1 is the voltage of the first node N1 at this time, which is equal to Vdata-Vth; V2 is the voltage of the second node N2 at this time, which is equal to the reference voltage VREF. the

步骤103、保持发光阶段(III)，扫描信号SCAN关断第二薄膜晶体管T2和第三薄膜晶体管T3，驱动薄膜晶体管T5继续保持导通状态，同时第二控制信号PR开启第四薄膜晶体管T4，第一控制信号EM开启第一薄膜晶体管T1，所述电容保持所述驱动薄膜晶体管的栅源电压不变，所述薄膜晶体管驱使所述发光元件发光。 Step 103, keep the light-emitting stage (III), turn off the second thin film transistor T2 and the third thin film transistor T3 by the scan signal SCAN, drive the thin film transistor T5 to continue to be in the on state, and at the same time turn on the fourth thin film transistor T4 by the second control signal PR, The first control signal EM turns on the first thin film transistor T1, the capacitor keeps the gate-source voltage of the driving thin film transistor constant, and the thin film transistor drives the light emitting element to emit light. the

保持发光阶段(III)中，扫描信号SCAN为低电平，第二控制信号 PR和第一控制信号EM为高电平，因此，第二薄膜晶体管T2、第三薄膜晶体管T3关断，第一薄膜晶体管T1和第四薄膜晶体管T4导通，电容C1连接在驱动薄膜晶体管T5的栅源之间，电容C1存储的电荷保持不变，驱动薄膜晶体管T5的栅源电压Vgs也保持不变，因此，驱动薄膜晶体管T5保持导通，驱使OLED发光，随着OLED电流趋于稳定，第一节点N1的电压变为OLED两端的电压Voled，由于电容C1的自举效应， In the light-emitting phase (III), the scan signal SCAN is low level, the second control signal PR and the first control signal EM are high level, therefore, the second thin film transistor T2 and the third thin film transistor T3 are turned off, and the first thin film transistor T3 is turned off. The thin film transistor T1 and the fourth thin film transistor T4 are turned on, the capacitor C1 is connected between the gate source of the driving thin film transistor T5, the charge stored in the capacitor C1 remains unchanged, and the gate source voltage Vgs of the driving thin film transistor T5 also remains unchanged, so , driving the thin film transistor T5 to keep on, driving the OLED to emit light, as the OLED current tends to be stable, the voltage of the first node N1 becomes the voltage Voled at both ends of the OLED, due to the bootstrap effect of the capacitor C1,

V2-Voled＝VREF+Vth-Vdata V2-Voled＝VREF+Vth-Vdata

V2＝Voled-Vdata+VREF+Vth----------(3) V2＝Voled-Vdata+VREF+Vth----------(3) 

第四薄膜晶体管T4导通，因此，第二节点N2和第三节点N3点的电压均变为：Voled-Vdata+VREF+Vth。 The fourth thin film transistor T4 is turned on, therefore, the voltages of the second node N2 and the third node N3 both become: Voled-Vdata+VREF+Vth. the

驱动薄膜晶体管T5的栅源电压Vgs保持为VREF+Vth-Vdata，此时驱动薄膜晶体管T5的电流为： The gate-source voltage Vgs of the driving thin film transistor T5 is maintained at VREF+Vth-Vdata, and the current driving the thin film transistor T5 is:

${\mathrm{<span><span>I</span>I</span>}}_{\mathrm{<span><span>OLED</span>OLED</span>}}<span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>2</span>2</span>}}<span><span>\&CenterDot;</span>\&CenterDot;</span>{\mathrm{<span><span>\&mu;</span>\&mu;</span>}}_{\mathrm{<span><span>n</span>no</span>}}<span><span>\&CenterDot;</span>\&CenterDot;</span>\mathrm{<span><span>Cox</span>Cox</span>}<span><span>\&CenterDot;</span>\&CenterDot;</span>\frac{\mathrm{<span><span>W</span>W</span>}}{\mathrm{<span><span>L</span>L</span>}}<span><span>\&CenterDot;</span>\&Center\; Dot;</span><span><span>[</span>[</span>\mathrm{<span><span>VREF</span>VREF</span>}<span><span>-</span>-</span>\mathrm{<span><span>Vdata</span>Vdata</span>}<span><span>+</span>+</span>\mathrm{<span><span>Vth</span>Vth</span>}<span><span>-</span>-</span>\mathrm{<span><span>Vth</span>Vth</span>}{<span><span>]</span>]</span>}^{\mathrm{<span><span>2</span>2</span>}}$

$<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>4</span>4</span>}<span><span>)</span>)</span>$

$<span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>2</span>2</span>}}<span><span>\&CenterDot;</span>\&Center\; Dot;</span>{\mathrm{<span><span>\&mu;</span>\&mu;</span>}}_{\mathrm{<span><span>n</span>no</span>}}<span><span>\&CenterDot;</span>\&CenterDot;</span>\mathrm{<span><span>Cox</span>Cox</span>}<span><span>\&CenterDot;</span>\&Center\; Dot;</span>\frac{\mathrm{<span><span>W</span>W</span>}}{\mathrm{<span><span>L</span>L</span>}}<span><span>\&CenterDot;</span>\&Center\; Dot;</span>{<span><span>[</span>[</span>\mathrm{<span><span>VREF</span>VREF</span>}<span><span>-</span>-</span>\mathrm{<span><span>Vdata</span>Vdata</span>}<span><span>]</span>]</span>}^{\mathrm{<span><span>2</span>2</span>}}$

由上式可知，驱动薄膜晶体管T5的电流，只与参考电压和数据电压有关，与阈值电压Vth和OLED两端的电压Voled无关，因此可消除了驱动薄膜晶体管阈值电压非均匀性、漂移以及OLED电气性能非均匀性的影响。 It can be seen from the above formula that the current driving the thin film transistor T5 is only related to the reference voltage and the data voltage, and has nothing to do with the threshold voltage Vth and the voltage Voled across the OLED, so it can eliminate the non-uniformity, drift and OLED electrical voltage of the driving thin film transistor. Effects of performance non-uniformity. the

本实施例的第二种具体实施方式中，如图7所示，像素电路的5个薄膜晶体管(T1～T4)均选用P型薄膜晶体管，驱动薄膜晶体管T5仍为N型薄膜晶体管，电路图控制时序图如图8所示，除了数据信号DATA，扫描信号SCAN、第一控制信号EM和第二控制信号PR与图4中的控制时序均相反，除此之外，该像素电路的具体工作过程及补偿推理过程大致类似，在此不再详述。 In the second specific implementation of this embodiment, as shown in Figure 7, the five thin film transistors (T1-T4) of the pixel circuit all use P-type thin film transistors, and the driving thin film transistor T5 is still an N-type thin film transistor. The timing diagram is shown in Figure 8. Except for the data signal DATA, the scanning signal SCAN, the first control signal EM and the second control signal PR are all opposite to the control timing in Figure 4. In addition, the specific working process of the pixel circuit It is roughly similar to the reasoning process of compensation and will not be described in detail here. the

现有像素电路的补偿功能，通常通过将驱动TFT置为如图2所示的二极管连接的方式来实现，但这种结构只适用于增强型的TFT，而对于耗尽 型TFT，因当Vgs＝0时仍然可以导通，因此TFT储存的电压中不包含阈值电压Vth的信息，所以对于耗尽型TFT无法进行补偿阈值电压的非均匀性造成的电流差异。 The compensation function of the existing pixel circuit is usually realized by placing the driving TFT in a diode connection as shown in Figure 2, but this structure is only applicable to the enhancement type TFT, and for the depletion type TFT, because when Vgs = 0, it can still be turned on, so the voltage stored by the TFT does not contain the information of the threshold voltage Vth, so the current difference caused by the non-uniformity of the threshold voltage cannot be compensated for the depletion TFT. the

而本实用新型提供的像素电路从上述推理过程可看出，是利用电容C1的存储电压包含阈值电压Vth的信息进行补偿，在补偿阶段(II)，因ELVDD＞Vdata，驱动薄膜晶体管T5源极会一直充电到Vdata-Vth，此时驱动薄膜晶体管T5的栅源电压Vgs＝Vdata-(Vdata-Vth)＝Vth，使得T5处于临界导通点，第一节点N1的电压等于Vdata-Vth，而这一补偿过程与Vth的极性无关，因此，这里无论驱动薄膜晶体管T5是耗尽型还是增强型，第一节点N1的电压均可达到Vdata-Vth。在保持发光阶段(III)利用电容C1存储的电荷不变，T5的栅源电压Vgs也保持为VREF一(Vdata-Vth)不变，从而使驱动薄膜晶体管T5的电流，只与参考电压和数据电压有关，与阈值电压Vth和OLED两端的电压Voled无关。 And the pixel circuit provided by the utility model can be seen from the above-mentioned reasoning process, is to utilize the storage voltage of electric capacity C1 to contain the information of threshold voltage Vth to carry out compensation, in compensation stage (II), because ELVDD>Vdata, drive thin film transistor T5 source It will be charged to Vdata-Vth, at this time, the gate-source voltage Vgs=Vdata-(Vdata-Vth)=Vth of the driving thin film transistor T5, so that T5 is at the critical conduction point, the voltage of the first node N1 is equal to Vdata-Vth, and This compensation process has nothing to do with the polarity of Vth, therefore, no matter whether the driving thin film transistor T5 is depletion mode or enhancement mode, the voltage of the first node N1 can reach Vdata-Vth. In the stage of maintaining light emission (III), the charge stored in the capacitor C1 remains unchanged, and the gate-source voltage Vgs of T5 also remains unchanged at VREF-(Vdata-Vth), so that the current of the driving thin film transistor T5 is only related to the reference voltage and data It is related to the voltage and has nothing to do with the threshold voltage Vth and the voltage Voled across the OLED. the

因此，本实用新型提供的像素电路对于增强型还是耗尽型的TFT都适用，都可有效地补偿TFT阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异，适用性更广。 Therefore, the pixel circuit provided by the utility model is applicable to both enhanced TFTs and depletion TFTs, and can effectively compensate TFT threshold voltage non-uniformity and drift, as well as current differences caused by OLED non-uniformity, and has wider applicability. the

本实用新型实施例还提供了一种显示装置，其设置有上述的任意一种像素电路。由于所述像素电路可有效地补偿耗尽型或增强型驱动TFT阈值电压非均匀性、漂移，以及OLED非均匀性导致的电流差异，因此本实施例所述显示装置亮度均一，显示效果更好。所述显示装置可以为：液晶面板、电子纸、OLED面板、手机、平板电脑、电视机、显示器、笔记本电脑、数码相框、导航仪等任何具有显示功能的产品或部件。 The embodiment of the present utility model also provides a display device, which is provided with any one of the above-mentioned pixel circuits. Since the pixel circuit can effectively compensate the non-uniformity and drift of the threshold voltage of the depletion-type or enhancement-type driving TFT, and the current difference caused by the non-uniformity of the OLED, the display device described in this embodiment has uniform brightness and better display effect. . The display device may be any product or component with a display function such as a liquid crystal panel, an electronic paper, an OLED panel, a mobile phone, a tablet computer, a television, a monitor, a notebook computer, a digital photo frame, a navigator, and the like. the

本实用新型实施例所述的技术特征，在不冲突的情况下，可任意相互组合使用。 The technical features described in the embodiments of the utility model can be used in combination with each other arbitrarily if there is no conflict. the

以上所述，仅为本实用新型的具体实施方式，但本实用新型的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本实用新型揭露 的技术范围内，可轻易想到变化或替换，都应涵盖在本实用新型的保护范围之内。因此，本实用新型的保护范围应所述以权利要求的保护范围为准。 The above is only a specific embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, and any skilled person familiar with the technical field can easily think of changes or changes within the technical scope disclosed by the utility model. Replacement should be covered within the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims. the

Claims (5)

1. an image element circuit is characterized in that, comprising:

Light-emitting component;

Be used for driving the driving thin film transistor (TFT) of described light-emitting component, its drain electrode input supply voltage signal;

The first film transistor, its source electrode is connected with described light-emitting component, and its drain electrode is connected with the source electrode of described driving thin film transistor (TFT), and its grid receives the first control signal;

The second thin film transistor (TFT), its source electrode reception of data signal, its drain electrode is connected with the grid of described driving thin film transistor (TFT), and its grid receives sweep signal;

The 3rd thin film transistor (TFT), its source electrode receives reference voltage signal, and its grid receives described sweep signal;

The 4th thin film transistor (TFT), its source electrode is connected with the drain electrode of described the 3rd thin film transistor (TFT), and its drain electrode is connected with the grid of described driving thin film transistor (TFT) and the drain electrode of described the second thin film transistor (TFT), and its grid receives the second control signal;

Electric capacity, one pole plate of described electric capacity is connected to first node, another pole plate is connected to Section Point, described first node is the tie point of described the first film transistor drain and described driving thin film transistor (TFT) source electrode, and described Section Point is the tie point of described the 4th thin film transistor (TFT) source electrode and the drain electrode of described the 3rd thin film transistor (TFT).

2. image element circuit according to claim 1 is characterized in that,

Described driving thin film transistor (TFT) is the N-type thin film transistor (TFT).

3. image element circuit according to claim 1 is characterized in that,

Described thin film transistor (TFT) is the depletion type thin film transistor (TFT), perhaps the reinforced membranes transistor.

4. each described image element circuit is characterized in that according to claim 1-3,

Described light-emitting component is Organic Light Emitting Diode.

5. a display device is characterized in that, is provided with each described image element circuit of claim 1-4.

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