CN100363967C - pixel driving circuit of active organic light emitting display - Google Patents

pixel driving circuit of active organic light emitting display Download PDF

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CN100363967C
CN100363967C CNB2004100697445A CN200410069744A CN100363967C CN 100363967 C CN100363967 C CN 100363967C CN B2004100697445 A CNB2004100697445 A CN B2004100697445A CN 200410069744 A CN200410069744 A CN 200410069744A CN 100363967 C CN100363967 C CN 100363967C
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organic light
light emitting
pixel driving
driving circuit
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CN1588519A (en
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李国胜
张浥尘
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AUO Corp
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AU Optronics Corp
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Abstract

The invention relates to a pixel driving circuit of an active organic light emitting display, in particular to a current-driven active organic light emitting display which is provided with a plurality of pixel driving circuits with voltage driving design. The pixel driving circuit is connected in parallel to a comparison circuit, and the comparison circuit at least has an organic light emitting diode and a transistor, which are respectively corresponding to the organic light emitting diode and the transistor in the pixel driving circuit. Through the comparison circuit, the drive current value led into the pixel drive circuit and the comparison current value led into the comparison circuit generate a specific proportional relation.

Description

主动式有机发光显示器的象素驱动电路 Pixel driving circuit of active organic light emitting display

技术领域 technical field

本发明是关于一种主动式有机发光显示器(Active Matrix OrganicLight Emitting Diode,AMOLED)的象素驱动电路,尤其是一种电流驱动的主动式有机发光显示器的象素驱动电路。The present invention relates to a pixel drive circuit of an Active Matrix Organic Light Emitting Diode (AMOLED), in particular to a current-driven pixel drive circuit of an Active Matrix Organic Light Emitting Diode.

背景技术 Background technique

随着有机发光二极管(Organic Light Emitting Diode,OLED)制作技术的进步,利用有机发光显示器的制作技术也渐趋成熟。基本上,有机发光二极管是以陈列方式排列于有机发光显示器内,而为了驱动这些有机发光二极管以产生影像,目前所使用的方法主要可区分为简单矩阵式(Simple Matrix)与主动矩阵式(Active Matrix)两种。其中,又以主动矩阵式较能符合大尺寸或是高分辨率显示的需求。With the progress of organic light emitting diode (Organic Light Emitting Diode, OLED) production technology, the production technology of organic light emitting display is also becoming mature. Basically, organic light emitting diodes are arranged in an array in an organic light emitting display, and in order to drive these organic light emitting diodes to generate images, the methods currently used can be mainly divided into simple matrix (Simple Matrix) and active matrix (Active Matrix). Matrix) two kinds. Among them, the active matrix type can better meet the needs of large-size or high-resolution display.

请参照图1所示,是一典型电压驱动主动式有机发光显示器的象素的等效电路图。此象素包括一有机发光二极管OLED、一个晶体管T1、一个晶体管T2与一个电容C。其中,晶体管T1的源极是连接至一数据线(未图标),以通入驱动电压信号Vdata,而其栅极是连接至一扫描线(未图标)以通入扫描电位Scan。晶体管T2的源极是连接至有机发光二极管OLED的阳极,其漏极是连接至一电压准位Vdd,而其栅极是连接至晶体管T1的漏极。有机发光二极管OLED的阴极是连接至另一电压准位Vss。电容C的两端是分别连接至晶体管T2的栅极以及电压准位VddPlease refer to FIG. 1 , which is an equivalent circuit diagram of a pixel of a typical voltage-driven active organic light emitting display. The pixel includes an organic light emitting diode OLED, a transistor T1, a transistor T2 and a capacitor C. Wherein, the source of the transistor T1 is connected to a data line (not shown) to pass through the driving voltage signal V data , and its gate is connected to a scan line (not shown) to pass through the scanning potential Scan. The source of the transistor T2 is connected to the anode of the organic light emitting diode OLED, the drain thereof is connected to a voltage level V dd , and the gate thereof is connected to the drain of the transistor T1 . The cathode of the organic light emitting diode OLED is connected to another voltage level Vss. Both ends of the capacitor C are respectively connected to the gate of the transistor T2 and the voltage level V dd .

为了产生稳定的电流使有机发光二极管OLED维持稳定的发光亮度,当来自扫描线的扫描电位Scan为高电位时,晶体管T1是开启,以使驱动电压信号Vdata得以经由数据线输入晶体管T2的栅极与电容C。而当扫描电位Scan处于低电位时,晶体管T1将关闭,而驱动电压信号Vdata的电压准位与前述电压准位Vdd的压差Vcs,是储存于电容C内。在此情况下,晶体管T2的栅极与源极的跨压Vgs是相当于Vdd-Vdata。而此跨压Vgs与晶体管T2的临界电压(threshold voltage,Vt)的差值,是决定流经有机发光二极管OLED的电流I的的大小。In order to generate a stable current to maintain a stable luminance of the organic light emitting diode OLED, when the scanning potential Scan from the scanning line is at a high potential, the transistor T1 is turned on, so that the driving voltage signal V data can be input to the gate of the transistor T2 through the data line Pole and capacitor C. When the scanning potential Scan is at a low potential, the transistor T1 is turned off, and the voltage difference V cs between the voltage level of the driving voltage signal Vdata and the aforementioned voltage level V dd is stored in the capacitor C. In this case, the voltage V gs across the gate and source of the transistor T2 is equivalent to V dd −V data . The difference between the cross voltage V gs and the threshold voltage (Vt) of the transistor T2 determines the magnitude of the current I flowing through the organic light emitting diode OLED.

请参照图2所示,是一典型电流驱动主动式有机发光显示器的象素的等效电路图。此象素包括一有机发光二极管OLED、一个晶体管T1、一个晶体管T2、一个晶体管T3、一个晶体管T4、与一个电容C。其中,晶体管T1的源极是连接至一数据线(未图标),以通入一驱动电流信号Idata,栅极是连接至一扫描线(未图标),以通入扫描电位Scan,而漏极是连接至晶体管T2的源极。晶体管T2的栅极是连接至晶体管T4的栅极,而其漏极是连接至有机发光二极管OLED的阳极与晶体管T4的源极。晶体管T3的源极是连接至数据线以通入驱动电流信号Idata,栅极是连接至扫描线以通入扫描电位Scan,而其漏极是连接至晶体管T2的栅极与晶体管T4的栅极。晶体管T4的源极是连接至有机发光二极管OLED的阳极,其漏极是连接至一电压准位Vdd。有机发光二极管OLED的阴极是连接至另一电压准位Vss。电容C的两端是分别连接至晶体管T4的栅极以及有机发光二极管OLED的阳极。Please refer to FIG. 2 , which is an equivalent circuit diagram of a pixel of a typical current-driven active OLED display. The pixel includes an organic light emitting diode OLED, a transistor T1, a transistor T2, a transistor T3, a transistor T4, and a capacitor C. Wherein, the source of the transistor T1 is connected to a data line (not shown), so as to pass through a driving current signal I data , the gate is connected to a scan line (not shown), so as to pass through the scanning potential Scan, and the drain is connected to the source of transistor T2. The gate of the transistor T2 is connected to the gate of the transistor T4, and the drain thereof is connected to the anode of the organic light emitting diode OLED and the source of the transistor T4. The source of the transistor T3 is connected to the data line to feed the driving current signal Idata , the gate is connected to the scan line to feed the scanning potential Scan, and its drain is connected to the gate of the transistor T2 and the gate of the transistor T4 pole. The source of the transistor T4 is connected to the anode of the organic light emitting diode OLED, and the drain of the transistor T4 is connected to a voltage level Vdd. The cathode of the organic light emitting diode OLED is connected to another voltage level V ss . Both ends of the capacitor C are respectively connected to the gate of the transistor T4 and the anode of the organic light emitting diode OLED.

为了产生稳定的电流使有机发光二极管OLED维持稳定的发光亮度,扫描电位Scan是首先透过扫描线开启晶体管T1与T3,使驱动电流信号Idata提供至晶体管T2与电容C,而在电容C内形成一对应于此驱动电流信号Idata的电压准位Vcs。而当来自扫描线S1的扫描电位为低电位时,晶体管T1与T3是关闭。同时,由于晶体管T2与晶体管T4是位于相对应的镜射电路(mirror circuit)上(相对于电容C与有机发光二极管OLED而言)。因此,在晶体管T2与T4具有相同电特性的情况下,储存于电容C内的电压准位Vcs将会引致一与前述驱动电流信号Idata相当的电流I,经由晶体管T4提供至有机发光二极管OLED,而使其发光。In order to generate a stable current so that the organic light-emitting diode OLED maintains a stable luminance, the scanning potential Scan first turns on the transistors T1 and T3 through the scanning line, so that the driving current signal I data is provided to the transistor T2 and the capacitor C, and in the capacitor C A voltage level V cs corresponding to the driving current signal I data is formed. And when the scan potential from the scan line S1 is low, the transistors T1 and T3 are turned off. Meanwhile, since the transistor T2 and the transistor T4 are located on the corresponding mirror circuit (relative to the capacitor C and the organic light emitting diode OLED). Therefore, under the condition that the transistors T2 and T4 have the same electrical characteristics, the voltage level V cs stored in the capacitor C will cause a current I corresponding to the aforementioned driving current signal I data , which is provided to the OLED through the transistor T4 OLED, so that it emits light.

如前述,并请同时参照图1所示,在电压驱动的象素中,流经有机发光二极管的电流I的大小,是受到临界电压Vt所影响。又,晶体管T2在运作过程中,其临界电压Vt往往会因为内电荷的累积而上升,进而导致流经有机发光二极管OLED的电流I下降,而造成发光亮度降低。As mentioned above, and please also refer to FIG. 1 , in a voltage-driven pixel, the magnitude of the current I flowing through the OLED is affected by the threshold voltage Vt. Moreover, during the operation of the transistor T2, the threshold voltage Vt tends to increase due to the accumulation of internal charges, thereby causing the current I flowing through the organic light emitting diode OLED to decrease, resulting in a decrease in luminous brightness.

反之,在图2所示的电流驱动的象素中,流经有机发光二极管OLED的电流大小,是由驱动电流信号I所决定,而不会受到晶体管T2与T4的临界电压值的变动所影响。但是,为了提供电流驱动的特性,在此象素中必须设计四个晶体管T1,T2,T3,T4,而造成制作成本上升,以及象素开口率不佳。On the contrary, in the current-driven pixel shown in FIG. 2, the magnitude of the current flowing through the organic light-emitting diode OLED is determined by the driving current signal I, and will not be affected by the variation of the threshold voltage values of the transistors T2 and T4. . However, in order to provide current-driven characteristics, four transistors T1, T2, T3, and T4 must be designed in the pixel, resulting in increased manufacturing costs and poor pixel aperture ratio.

如何避免晶体管临界电压值的变动对于有机发光二极管的发光亮度的影响,同时减少象素内的电子元件数量以改善开口率,将对于有机发光显示器的发展,有极为重要的影响。How to avoid the impact of the variation of the threshold voltage of the transistor on the luminance of the OLED, and reduce the number of electronic components in the pixel to improve the aperture ratio will have a very important impact on the development of the OLED.

发明内容 Contents of the invention

本发明的主要目的是在于克服既有电流驱动有机发光显示器的象素,其开口率不佳的缺点,提出一种解决的手段。The main purpose of the present invention is to overcome the disadvantage of poor aperture ratio of the pixels of the existing current-driven organic light-emitting display, and to propose a solution.

本发明的另一目的是在于克服传统电压驱动有机发光显示器的象素,其发光亮度不易维持稳定的缺点,提出一种解决的手段。Another object of the present invention is to overcome the disadvantages of traditional voltage-driven organic light-emitting display pixels that the luminous brightness is difficult to maintain stable, and to propose a solution.

本发明是提供一种主动式有机发光显示器,其具有多个电压驱动设计的象素驱动电路,但却利用一驱动电流驱动这些象素驱动电路。此主动是有机发光显示器的特征在于,上述象素驱动电路是并联于一比对电路,而此比对电路至少具有一有机发光二极管与一晶体管,分别对应至象素驱动电路内的有机发光二极管与晶体管。透过此比对电路,即可使通入象素驱动电路的驱动电流值与通入比对电路的比对电流值产生一特定的比例关系。The present invention provides an active organic light-emitting display, which has a plurality of pixel driving circuits designed for voltage driving, but uses a driving current to drive these pixel driving circuits. The characteristic of this active organic light emitting display is that the above-mentioned pixel driving circuit is connected in parallel to a comparison circuit, and the comparison circuit has at least one organic light emitting diode and a transistor, respectively corresponding to the organic light emitting diodes in the pixel driving circuit with transistors. Through the comparison circuit, a specific proportional relationship can be generated between the driving current value passed into the pixel driving circuit and the comparison current value passed into the comparison circuit.

本发明还提供一种主动式有机发光显示器的象素驱动电路,所述驱动电路包括:至少一象素驱动电路,每一该象素驱动电路包括:一第一晶体管,其源极是连接至一数据线,其栅极是连接至一扫描线;一第二晶体管,其栅极是连接至该第一晶体管的漏极,该第二晶体管的漏极是通有一第一电压准位;一电容,其一第一端是连接至该第二晶体管的漏极,其一第二端是连接至该第一晶体管的源极与该第二晶体管的栅极;一有机发光二极管,其阳极是连接至该第二晶体管的源极,该有机发光二极管的阴极是通有一第二电压准位;至少一比对电路,电连接至该象素驱动电路,并且每一该比对电路包括:一比对晶体管,对应于该第二晶体管,其栅极与漏极是连接至该数据线;一比对有机发光二极管,对应于该有机发光二极管,其阳极是连接至该比对晶体管的源极,其阴极是通有该第二电压准位。The present invention also provides a pixel driving circuit for an active organic light emitting display, the driving circuit includes: at least one pixel driving circuit, each pixel driving circuit includes: a first transistor, the source of which is connected to A data line, the gate of which is connected to a scan line; a second transistor, whose gate is connected to the drain of the first transistor, and the drain of the second transistor is connected to a first voltage level; a capacitor, a first end of which is connected to the drain of the second transistor, and a second end of which is connected to the source of the first transistor and the gate of the second transistor; an organic light emitting diode, whose anode is Connected to the source of the second transistor, the cathode of the organic light-emitting diode is connected to a second voltage level; at least one comparison circuit is electrically connected to the pixel driving circuit, and each comparison circuit includes: a A comparison transistor, corresponding to the second transistor, whose gate and drain are connected to the data line; a comparison organic light emitting diode, corresponding to the organic light emitting diode, whose anode is connected to the source of the comparison transistor , the cathode of which is supplied with the second voltage level.

该第二电压准位是接地。The second voltage level is ground.

附图说明 Description of drawings

图1是一典型电压驱动主动式有机发光显示器的象素的等效电路图;FIG. 1 is an equivalent circuit diagram of a pixel of a typical voltage-driven active organic light-emitting display;

图2是一典型电流驱动主动式有机发光显示器的象素的等效电路图;2 is an equivalent circuit diagram of a pixel of a typical current-driven active organic light-emitting display;

图3是本发明主动式有机发光显示器的驱动电路,一较佳实施例的方块示意图;3 is a schematic block diagram of a preferred embodiment of the driving circuit of the active organic light emitting display of the present invention;

图4是图3中单一象素驱动电路与透过数据线并联于此象素驱动电路的一比对电路的等效电路图。FIG. 4 is an equivalent circuit diagram of a single pixel driving circuit in FIG. 3 and a comparison circuit connected in parallel to the pixel driving circuit through a data line.

符号说明:Symbol Description:

驱动电路~100Drive circuit ~ 100

数据驱动单元~120Data Drive Unit ~ 120

扫描驱动单元~140Scan drive unit ~ 140

电源供应单元~150Power supply unit ~ 150

象素驱动电路~160Pixel drive circuit ~ 160

数据线~122Data line ~ 122

扫描线142scan line 142

比对电路~180Comparison circuit ~ 180

电源线~152Power cord ~ 152

具体实施方式 Detailed ways

关于本发明的优点与精神可以借由以下的发明较佳的实施例详述及所附图式得到进一步的了解。The advantages and spirit of the present invention can be further understood through the following detailed description of preferred embodiments of the invention and the accompanying drawings.

请参照图3所示,是本发明的主动式有机发光显示器的驱动电路100,一较佳实施例的方块示意图。此驱动电路100包括一数据驱动单元120、一扫描驱动单元140、一电源供应单元150、多个象素驱动电路160与多个比对电路180。其中,各个象素驱动电路160是呈陈列排列。数据驱动单元120是透过多个数据线122,分别连接各行象素驱动电路160以及比对电路180。扫描驱动单元140是透过多个扫描线142,分别连接各列象素驱动电路160。电源供应单元150是提供各个象素驱动单元160驱动其内部的有机发光二极管发光所需要的电源。每一行象素驱动电路160的最下端,是透过数据线122耦接有一比对电路180。而此比对电路180是用以产生如同图2所示传统电流驱动的象素内的镜射电路的效果。Please refer to FIG. 3 , which is a schematic block diagram of a preferred embodiment of the driving circuit 100 of the active organic light emitting display of the present invention. The driving circuit 100 includes a data driving unit 120 , a scanning driving unit 140 , a power supply unit 150 , a plurality of pixel driving circuits 160 and a plurality of comparison circuits 180 . Wherein, each pixel driving circuit 160 is arranged in a row. The data driving unit 120 is connected to the pixel driving circuit 160 and the comparison circuit 180 of each row respectively through a plurality of data lines 122 . The scanning driving unit 140 is respectively connected to the pixel driving circuits 160 of each column through a plurality of scanning lines 142 . The power supply unit 150 provides the power required by each pixel driving unit 160 to drive its internal organic light emitting diodes to emit light. The bottom end of the pixel driving circuit 160 in each row is coupled to a comparison circuit 180 through the data line 122 . The comparison circuit 180 is used to produce the effect of the mirror circuit in the conventional current-driven pixel as shown in FIG. 2 .

请参照图4所示,是图3中单一象素驱动电路160,与透过数据线122并联于此象素驱动电路160的一比对电路180的等效电路图。如图中所示,此象素驱动电路160包括一第一晶体管T1、一第二晶体管T2、一电容C与一有机发光二极管OLED。其中,第一晶体管T1的源极是连接至数据线122,而栅极是连接至扫描线142。第二晶体管T2的栅极是连接至第一晶体管T1的漏极,而第二晶体管T2的漏极透过电源线152连接至电源供应单元150,以通入一第一电压准位Vdd。电容C的一端是连接至第二晶体管T2的漏极,而另一端是连接至第一晶体管T1的源极与第二晶体管T2的栅极。有机发光二极管OLED的阳极是连接至第二晶体管T2的源极,而其阴极是通有一第二电压准位Vss,该第二电压准位是接地。Please refer to FIG. 4 , which is an equivalent circuit diagram of a single pixel driving circuit 160 in FIG. 3 and a comparison circuit 180 connected in parallel to the pixel driving circuit 160 through the data line 122 . As shown in the figure, the pixel driving circuit 160 includes a first transistor T1, a second transistor T2, a capacitor C and an organic light emitting diode OLED. Wherein, the source of the first transistor T1 is connected to the data line 122 , and the gate is connected to the scan line 142 . The gate of the second transistor T2 is connected to the drain of the first transistor T1 , and the drain of the second transistor T2 is connected to the power supply unit 150 through the power line 152 for a first voltage level Vdd. One end of the capacitor C is connected to the drain of the second transistor T2, and the other end is connected to the source of the first transistor T1 and the gate of the second transistor T2. An anode of the organic light emitting diode OLED is connected to the source of the second transistor T2, and a cathode thereof is connected to a second voltage level Vss, and the second voltage level is grounded.

此比对电路180包括一比对晶体管Tm与一比对有机发光二极管OLEDm。其中,比对晶体管Tm是对应于象素驱动电路160内的第二晶体管T2,而此比对晶体管Tm的栅极是连接至数据线122,而其漏极亦是连接至数据线122。比对有机发光二极管OLEDm是对应于象素驱动电路160内的有机发光二极管OLED,并且,其阳极是连接至上述比对晶体管Tm的源极,而其阴极是通有上述第二电压准位Vss。The comparison circuit 180 includes a comparison transistor Tm and a comparison organic light emitting diode OLEDm. Wherein, the comparison transistor Tm corresponds to the second transistor T2 in the pixel driving circuit 160 , and the gate of the comparison transistor Tm is connected to the data line 122 , and its drain is also connected to the data line 122 . The comparison organic light emitting diode OLEDm is corresponding to the organic light emitting diode OLED in the pixel driving circuit 160, and its anode is connected to the source of the above comparison transistor Tm, and its cathode is connected to the above second voltage level Vss .

当一给定的驱动电流信号I输入比对电路180,则比对晶体管Tm的栅极与源极的跨压Vgs’与比对晶体管Tm临界电压Vt’的差(Vgs’-Vt’)也随之确定。而在此情况下,数据线122所具有的电压准位Vdata=Vgs’+Voled’+Vss。其中,Voled’是比对有机发光二极管OLEDm的阳极与阴极间的跨压。When a given drive current signal I is input into the comparison circuit 180, the difference between the cross voltage V gs' between the gate and the source of the comparison transistor Tm and the threshold voltage V t' of the comparison transistor Tm (V gs' -V t' ) is also determined accordingly. In this case, the voltage level of the data line 122 is V data =V gs' +V oled' +V ss . Wherein, V oled' is the cross voltage between the anode and the cathode of the comparative organic light emitting diode OLEDm.

在此同时,一扫描电位是透过扫描线142输入象素驱动电路160内以开启第一晶体管T1,借以在电容C内储存第一电压准位Vdd与上述数据线122的电压准位Vdata的压差。在此情况下,第二晶体管T2的栅极与源极的跨压Vgs是相当于Vdata-Voled-Vss,其中Voled是此有机发光二极管OLED的阳极与阴极间的跨压。At the same time, a scanning potential is input into the pixel driving circuit 160 through the scanning line 142 to turn on the first transistor T1, so as to store the first voltage level Vdd and the voltage level V data of the data line 122 in the capacitor C. pressure difference. In this case, the voltage V gs across the gate and source of the second transistor T2 is equivalent to V data -V oled -V ss , where V oled is the voltage across the anode and cathode of the organic light emitting diode OLED.

由于数据线142所具有的电压准位Vdata=Vgs’+Voled’+Vss,而第二晶体管T2的栅极与源极的跨压Vgs=Vdata-Voled-Vss。因此,可以推算得知,第二晶体管T2的栅极与源极的跨压Vgs是相当于Vgs’-(Voled-Voled’)。而此跨压Vgs与第二晶体管T2的临界电压Vt的差值,即决定流经有机发光二极管OLED的电流I’的的大小。Since the voltage level of the data line 142 is V data =V gs' +V oled' +V ss , the voltage across the gate and source of the second transistor T2 is V gs =V data -V oled -V ss . Therefore, it can be estimated that the voltage Vgs across the gate and source of the second transistor T2 is equivalent to V gs' -(V oled -V oled' ). The difference between the cross voltage V gs and the threshold voltage Vt of the second transistor T2 determines the magnitude of the current I′ flowing through the organic light emitting diode OLED.

由前述,可知本发明的驱动电路,其特色在于:From the foregoing, it can be seen that the drive circuit of the present invention is characterized in that:

由于比对有机发光二极管OLEDm与有机发光二极管OLED具有近似的运作时间,因此,二者的阳极与阴极间跨压的上升情况也相类似,也就是说Voled约等于Voled’。而如前述,第二晶体管T2的栅极与源极的跨压Vgs=Vgs’-(Voled-Voled’),可以推知,第二晶体管T2的栅极与源极的跨压Vgs是相当于比对晶体管Tm的栅极与源极的跨压Vgs’。又,比对晶体管Tm的栅极与源极的跨压Vgs’是受到驱动电流信号I所决定,而第二晶体管的栅极与源极的跨压Vgs的大小是决定了流经有机发光二极管OLED的电流I’的大小。因此,本发明可以直接由驱动电流信号I决定流经有机发光二极管的电流I’大小,而避免了有机发光二极管OLED的跨压变化对于电流I’的大小的影响。Since the organic light-emitting diode OLEDm and the organic light-emitting diode OLED have similar operation times, the voltage rises between the anode and the cathode are also similar, that is to say, V oled is approximately equal to V oled′ . As mentioned above, the voltage across the gate and source of the second transistor T2 is V gs =V gs' -(V oled -V oled' ), it can be deduced that the voltage across the gate and source of the second transistor T2 V gs is equivalent to the cross-voltage V gs′ between the gate and the source of the comparison transistor Tm. Also, the cross voltage V gs' between the gate and source of the comparison transistor Tm is determined by the driving current signal I, and the magnitude of the cross voltage V gs between the gate and source of the second transistor determines the flow through the organic The magnitude of the current I' of the light-emitting diode OLED. Therefore, the present invention can directly determine the magnitude of the current I' flowing through the organic light emitting diode according to the driving current signal I, and avoid the influence of the voltage change across the organic light emitting diode OLED on the magnitude of the current I'.

由于比对晶体管Tm与第二晶体管T2具有近似的运作时间,二者的临界电压Vt’与Vt的上升幅度也相类似。又如上述,第二晶体管T2的栅极与源极的跨压Vgs是相当于比对晶体管Tm的栅极与源极的跨压Vgs’。因此,比对晶体管Tm与第二晶体管T2,其栅极与源极的跨压与临界电压的差(Vgs-Vt)与(Vgs’-Vt’)是相当。由此可知,在比对晶体管T2与第二晶体管Tm的沟道的宽长比(W/L)相同的情况下,流经有机发光二极管OLED的电流I’大小并不会受到临界电压Vt与Vt’上升的影响,而会与驱动电流信号I的大小相同。Since the comparison transistor Tm and the second transistor T2 have similar operation times, the threshold voltage V t′ and the rising range of V t of the two are also similar. As mentioned above, the voltage V gs across the gate and source of the second transistor T2 is equivalent to the voltage Vg s′ across the gate and source of the comparative transistor Tm. Therefore, comparing the transistor Tm and the second transistor T2, the difference between the gate-source cross voltage and the threshold voltage (V gs −V t ) is equivalent to (V gs′ −V t′ ). It can be seen that, under the condition that the channel width-to-length ratio (W/L) of the comparison transistor T2 and the second transistor Tm are the same, the magnitude of the current I' flowing through the organic light emitting diode OLED will not be affected by the critical voltage V t With the effect of V t' rising, it will be the same as the magnitude of the driving current signal I.

如上述,在第二晶体管T2与比对晶体管Tm,其栅极与源极的跨压与临界电压的差(Vgs-Vt)与(Vgs’-Vt’)大小相当的情况下。比对晶体管Tm与第二晶体管T2的沟道的宽长比将会影响驱动电流信号I与电流I’的比例关系。举例来说,若是比对晶体管Tm的沟道的宽长比为第二晶体管T2的沟道的宽长比的两倍时,在相同的跨压下(即Vgs约略等于Vgs’),流经比对晶体管Tm的驱动电流信号I约略为流经第二晶体管T2的电流I’的二倍。而利用此概念,即便是在低发光亮度的情况下(即流经象素驱动电路160中第二晶体管T2的电流I’微弱的情况下),在数据线122中仍然可以维持相对较大的驱动电流信号I,以对象素驱动电路160的电容C提供足够快的充电速度,确保电容C充电至预设的电位值。As mentioned above, in the second transistor T2 and the comparison transistor Tm, the difference (V gs -V t ) between the gate and the source and the threshold voltage is equivalent to (V gs' -V t' ) . Comparing the channel width-to-length ratios of the transistor Tm and the second transistor T2 will affect the proportional relationship between the driving current signal I and the current I′. For example, if the channel width-to-length ratio of the comparison transistor Tm is twice the channel width-to-length ratio of the second transistor T2, under the same cross voltage (that is, V gs is approximately equal to V gs' ), The driving current signal I flowing through the comparison transistor Tm is approximately twice the current I' flowing through the second transistor T2. And using this concept, even in the case of low luminance (that is, the current I' flowing through the second transistor T2 in the pixel driving circuit 160 is weak), the data line 122 can still maintain a relatively large The current signal I is driven to provide a fast enough charging speed for the capacitor C of the pixel driving circuit 160 to ensure that the capacitor C is charged to a preset potential value.

如第三与四图所示,本发明的驱动电路100虽然是利用电流驱动,但是,各个象素驱动电路160只需要两个晶体管T1与T2,而非如图2的传统电流驱动的象素,必须使用四个晶体管。因此,本发明的驱动电路100的设计可以提升各个象素的开口率。As shown in the third and fourth figures, although the drive circuit 100 of the present invention is driven by current, each pixel drive circuit 160 only needs two transistors T1 and T2, rather than the conventional current-driven pixel of FIG. , four transistors must be used. Therefore, the design of the driving circuit 100 of the present invention can increase the aperture ratio of each pixel.

Claims (6)

1.一种主动式有机发光显示器的象素驱动电路,其特征在于所述驱动电路包括:1. A pixel drive circuit for an active organic light emitting display, characterized in that the drive circuit comprises: 至少一象素驱动电路,每一该象素驱动电路包括:At least one pixel driving circuit, each pixel driving circuit includes: 一第一晶体管,其源极是连接至一数据线,其栅极是连接至一扫描线;A first transistor, its source is connected to a data line, its gate is connected to a scan line; 一第二晶体管,其栅极是连接至该第一晶体管的漏极,该第二晶体管的漏极是通有一第一电压准位;a second transistor, the gate of which is connected to the drain of the first transistor, and the drain of the second transistor is connected to a first voltage level; 一电容,其一第一端是连接至该第二晶体管的漏极,其一第二端是连接至该第一晶体管的源极与该第二晶体管的栅极;a capacitor, a first terminal of which is connected to the drain of the second transistor, and a second terminal of which is connected to the source of the first transistor and the gate of the second transistor; 一有机发光二极管,其阳极是连接至该第二晶体管的源极,该有机发光二极管的阴极是通有一第二电压准位;An organic light emitting diode, the anode of which is connected to the source of the second transistor, and the cathode of the organic light emitting diode is connected to a second voltage level; 至少一比对电路,电连接至该象素驱动电路,并且每一该比对电路包括:At least one comparing circuit is electrically connected to the pixel driving circuit, and each comparing circuit includes: 一比对晶体管,对应于该第二晶体管,其栅极与漏极是连接至该数据线;a comparison transistor, corresponding to the second transistor, whose gate and drain are connected to the data line; 一比对有机发光二极管,对应于该有机发光二极管,其阳极是连接至该比对晶体管的源极,其阴极是通有该第二电压准位。A comparison organic light emitting diode, corresponding to the organic light emitting diode, its anode is connected to the source of the comparison transistor, and its cathode is connected to the second voltage level. 2.根据权利要求1所述的一种主动式有机发光显示器的象素驱动电路,其特征在于:该比对晶体管与该第二晶体管的沟道的宽长比是具有一特定的比例关系。2 . The pixel driving circuit of an active organic light emitting display according to claim 1 , wherein the channel width-to-length ratios of the comparison transistor and the second transistor have a specific proportional relationship. 3.根据权利要求1所述的一种主动式有机发光显示器的象素驱动电路,其特征在于:该比对晶体管与该第二晶体管的沟道的宽长比是相同。3 . The pixel driving circuit of an active organic light emitting display according to claim 1 , wherein the channel width-to-length ratios of the comparison transistor and the second transistor are the same. 4.根据权利要求1所述的一种主动式有机发光显示器的象素驱动电路,其特征在于:每一个该比对电路是对应至该数据线。4. The pixel driving circuit of an active organic light emitting display according to claim 1, wherein each comparison circuit is corresponding to the data line. 5.根据权利要求1所述的一种主动式有机发光显示器的象素驱动电路,其特征在于:该第一电压准位是经由一电源线提供至该第二晶体管。5. The pixel driving circuit of an active organic light emitting display according to claim 1, wherein the first voltage level is provided to the second transistor through a power line. 6.根据权利要求1所述的一种主动式有机发光显示器的象素驱动电路,其特征在于:该第二电压准位是接地。6. The pixel driving circuit of an active organic light emitting display according to claim 1, wherein the second voltage level is grounded.
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