201007662 九、發明說明： 【發明所屬之技術領域】 本發明是有關於一種畫素電路，特別是指一種可補償 一薄膜電晶體之臨界電壓變異及補償一有機發光二極體因 材料老化而造成亮度衰減之畫素電路。 【先前技術】 現今，利用有機發光二極體（OLED )來當作光源，已 是相當普遍的應用。而有機發光二極體的亮度是依照流過其 上的驅動電流來決定’因此，對於一用以驅動該有機發光二 極體之驅動電路而言，其中的電晶體與該有機發光二極體在 製程上的相關因素的變化，往往都會影響到該有機發光二極 體的發光效能，針對各種因素對於有機發光二極體的影響說 明如下： 一、 電晶體臨界電壓： 因為一面板長時間使用或是因為製程差異將會造 成該臨界電壓值的變異，將會使得流經該有機發光二 極體的驅動電流產生變化’因此該有機發光二極體的 發光亮度將會受到影響，當該面板中的多數畫素電路 皆受到該臨界電壓值變異所影響時，容易使得該面板 看起來的亮度不均勻或是發生有時較亮有時較暗等亮 度不穩定的問題產生。 二、 驅動電路之電源電壓： 當應用於一大尺寸面板上時，隨著訊號線的拉長 ，内阻逐漸增加，將使得該驅動電路之電源電壓發生 201007662 衰減效應，稱之為IR-drop效應，該效應將導致該驅動 電流下降，因而使得該大尺寸面板亮度不均勻的情況 〇 三、有機發光二極體老化效應： 由於材料老化的現象，有機發光二極體在長時間操作 下，可能會發生電壓降逐漸上升而影響到該驅動電流的大 小。因此，若因長時間操作造成有機發光二極體老化，進 而使得其發光效率下降，那即便是該驅動電流符合預期， 也無法產生預期的亮度。若是發生在RGB三色的發光效率 下降程度不同，更會發生色偏的問題。 針對以上因素，目前已有相關技術與以改善，如： 2007年加拿大滑鐵盧大學於IEEE Journal of Display Technology 中所提出的「AMOLED pixel circuit with electronic compensation of luminance degradation」' 2005 年韓國漢城大學於IEEE Electron Device Letter中所提出的 「A new a-Si:H TFT pixel circuit compensating the threshold voltage shift of a-Si:H TFT and OLED for active matrix OLED」，及2005年台灣交通大學於IEEE/OSA Journal of Display Technology 中所提出的「A new pixel circuit for driving organic light emitting diodes with low temperature polycrystalline thin film transistors」。 在該等相關前案中，為了解決上述各種因素造成的問 題，往往導致電路結構太過複雜，使得該畫素電路内具有 較多的元件數量，就會導致開口率的降低，並影響該有機 201007662 / 發光二極體的發光效率。因此，如何有效改善各種因素造 成的問題，同時又可以降低對於該有機發光二極體發光效 率的影響，是相當重要的議題。 【發明内容】 因此，本發明之目的是提供一種晝素電路，包含： 一有機發光二極體，具有一陽極及一陰極；及 一驅動電路，包括： 一第一電晶體’及一第二電晶體，每一電晶體具 _ 有一第一端、一第二端，及一決定該第一端及該第二 端是否導通的控制端； 一電容； 一資料電壓開關；及 一參考電壓開關； 其中’該有機發光二極體之陽極電連接於一第一電源 電壓’該第一電晶體之第二端與該第二電晶體之第二端、 該第二電晶體之控制端、該有機發光二極體之陰極電連接 ❹ ，該第一電晶體之控制端與該電容之一端電連接，該第二 電晶體之第一端與該電容之另一端電連接，該第一電晶體 之第一端與一第二電源電壓電連接，該資料電壓開關接收 一資料電壓，並接受一第一控制訊號的控制，以決定是否 - 輸出該資料電麼到該第一電晶體之控制端，該參考電壓開 關接收一參考電壓，並接受一第二控制訊號的控制，以決 定是否輸出該參考電壓到該第二電晶體之第—端。 此外’本發明另一目的是，提供一種驅動電路，包含 7 201007662 一第一電晶體，及一第二電晶體，每一電晶體具有一 第一端、一第二端，及一決定該第一端及該第二端是否導通 的控制端； 一電容； 一資料電壓開關；及 一參考電壓開關； 其中’該第一電晶體之第二端與該第二電晶體之第二 端、該第二電晶體之控制端電連接，該第一電晶體之控制端 與該電容之一端電連接，該第二電晶體之第一端與該電容之 另端電連接，該第一電晶趙之第一端與一第二電源電壓電 連接，該資料電壓開關接收一資料電壓，並接受一第一控制 訊號的控制，以決定是否輸出該資料電壓到該第一電晶體之 控制端，該參考電壓開關接收一參考電壓，並接受一第二控 制訊號的控制，以決定是讀出該參考電壓到該第二電晶體 之第一端。 本發明之另—目較，提供—種畫素電路，包含 一發光元件，具有一陽極及一陰極；及 一驅動電路，包括： 電晶體，每一電晶體具 決定該第一端及該第二 一第一電晶體，及一第二 有一第一端、一第二端，及— 端是否導通的控制端； 一電容； 一資料電壓開關；及 201007662 一參考電壓開關； 其中，該發光元件之陽極電連接於一第一電源電壓， 該第一電晶體之第二端與該第二電晶體之第二端、該第二 電晶體之控制端、該發光元件之陰極電連接，該第一電晶 體之控制端與該電容之一端電連接，該第二電晶體之第— 端與該電容之另一端電連接，該第一電晶體之第一端與一 第二電源電壓電連接，該資料電壓開關接收一資料電壓， 並接受一第一控制訊號的控制，以決定是否輸出該資料電 ❹ 壓到該第一電晶體之控制端，該參考電壓開關接收一參考 電壓，並接受一第二控制訊號的控制，以決定是否輸出該 參考電壓到該第二電晶體之第一端。 【實施方式】 有關本發明之前述及其他技術内容、特點與功效，在 以下配合參考圖式之一個較佳實施例的詳細說明中，將可 清楚的呈現。 、 參閱圖1，本發明之較佳實施例包含一有機發光二極體 ® ( 〇LED ) 8及一驅動電路9，該驅動電路9包括一第一電 晶體91、一第二電晶體92、一電容95、一資料電壓開關 98,及一參考電壓開關99,其中，在本實施例中該資料電 壓開關98是一第三電晶體93，而該參考電壓開關99是一 第四電晶體94。該第一至該第四電晶體91〜94是N型薄膜 電晶體（TFT )。其中’每一電晶體91〜94包括一第一端、 一第二端及一決定該第一段與該第二端是否導通之控制端 ’該有機發光一極體8具有一陽極及一陰極。 9 201007662 該第—電晶體91之第二端與該第二電晶體92之第二 〜 端、該第二電晶體92之控制端、該有機發光二極體8之陰 極電連接（以下稱為A點）；該第一電晶體91之控制端與 該電容95之一端、該第三電晶體93之第二端電連接（以 下稱為B點）；該第二電晶體92之第一端與該電容95之另 一端、該第四電晶體94之第二端電連接（以下稱為c點） 該第電曰曰體91之第一端與一第二電源電壓Vss電連接 ，該第三電晶體93之控制端接收一第一控制訊號Vseu， 該第三電晶體93之第一端接收一資料電壓Vdata，該第四 _ 電晶體94之控制端接收一第二控制訊號VsEL2，該第四電 日日體94之第一端接收一參考電壓vREF，該有機發光二極體 8之陽極電連接於一第一電源電壓VDD。 該較佳實施例之時序圖如圖2所示，可以分為三個階 段： I· 資料輸入階段： 聯合參閱圖1、2’該第一控制訊號vSEL1與該第二控 制訊號VSEL2設定為高電位，該參考電壓VREF設定為低參⑩ 考電位Vref_l ’因此，該第三與第四電晶體93、94會被導 通，因為此時VREF_L與VDATA皆為低電位，所以該電容95 之跨壓V95會經由Vref端與VDATA端放電，其等效電路圖 如圖3所示。 當該電容95放電一段時間之後，C點的電壓持續下降 ，直到C點與A點的電壓差大於該第二電晶體92之臨界電 壓值時Vth，92時（因為該第二電晶體92之閘極電壓與A點 10 201007662 v 電連接），該第二電晶體92將會被導通’此時，進入補償 階段。 II·補償階段： 回復參閱圖1、2,當該第二電晶體92被導通之後’該 第二控制訊號VSEL2設定為低電位，因此，該第四電晶體94 會被關閉’此時，因為該第二電晶體92之閘極電壓電連接 到A點，因此’該電容95之一端（即C點）會持讀充電至 Vg，92 — VTH 92，等效電路圖如圖4所示，因此，^點的電麼 ® 可以表示如下： = VC,92 - ^TH,92 = ^A~ Kh,92 = ^DD ~ ^OLED ~ ^TH,92 其中’ VOLED為該有機發光二極體8之端電麼。 同時’因為該第三電晶體93被導通’因此該資料電壓 vdata將會被傳送至b點。 當c點電壓被充電至Vdd—v〇led_VtH92之後，因為 φ 該第二電晶體92之閘極電壓與源極電壓差v加，92又小於該 第一電晶體之臨界電壓VTH,92，因此，該第二電晶體92將 再度關閉，並進入發先階段。值得注意的是，由於該電容 95沒有放電路徑可供放電，因此在進入發光階段前，該電 谷之電壓V95為B點電壓VB與C點電壓Vc間的電壓差， 如下式所示： V95 = =VDATA ~(VDD-vOLED-vm^)^vDATA _v〇D +v〇LED +Vth^ 為了後續說明方便’我們假設此時C點的電壓為〇， 11 201007662 而 B 點的電壓為 VdaTA— VdD + V〇LED + VtH,92。 III.發光階段： 聯合參閱圖1、2’該參考電壓Vref設定為南參考電位 VREF_H，同時將該第一控制訊號VSEL1設定為低電位，使得 該第三電晶體93被關閉，之後，再將該第二控制訊號 Vs EL2設定為南電位’使得該第四電晶體92被導通’因此， 該高參考電位Vref_h將會傳送至C點，同時，該電容95之 另一端（即B點）之電壓會等量跳躍至乂以^+乂^以一 VdD +V〇LED +VtH,92，同時B點電壓Vb亦為該第一電晶體之 閘極電壓VG，91，等效電路圖如圖5所示，因此，會產生一 由該有機發光二極體8流至該第一電晶體91第二端之驅動 電流Idrive為： ^OLED = ^9l(^GS,91 ~ ^Τ«,9ΐ) =^9l(^G,91 — ^5,91 — ^ΓΗ,9ΐ) =K91(VREF _H +V〇ATA ~VDD +V〇LE〇 +VTH 92 —^77/,91 — ^ss) 根據上述的公式，若是假設該第一電晶體91與該第二 電晶體92具有相同的臨界電壓，也就是說V TH，91=VtH，92 ; _ 此外*當該南參考電位Vref_h設定為與該第'電源電壓 VDD相同之電壓時且Vss為OV，則上述之公式可以簡化成 如下所示： ^OLED = ^9\ ^DATA + ^OLED ) 根據上述的電流公式可以知道，流經有機發光二極體8 的驅動電流I OLED 與該等第一、第二電源電壓VDD、Vss，及 12 201007662 該第—電晶體91的臨界電壓vTH,91無關。因此，在發光階 段時’流經有機發光二極體8的驅動電流i0LED僅僅由該資 料電壓vDATA大小來決定，此外，當vOLED因為該有機發光 一極體8材料的老化而增加時，相對的也會提高該有機發 光一極體8的電流量i〇LED，因此，可以補償該有機發光二 極體8因為材料老化而造成亮度衰減的現象。 值得注意的是’本實施例除了用於驅動該有機發光二 極體8之外’也可以用於驅動其他受電流驅動的發光元件 ’例如.發光二極體（LED) ’且該等電晶體91~94除了是 N型TFT之外，也可以是N型金屬氧化物半導體（pM〇s ) 〇 本實施例採用電路模擬的方式以驗證補償效果。圖6 是藉由輸入各種不同的資料電壓值’假設電路中之電晶體 分別具有-0.3伏特、〇伏特、+〇 3伏特的臨界電壓變異時， 該有機發光二極體之驅動電流與資料電壓的轉移曲線圖。 由圖6中，可以觀察到習知的驅動電流會根據不同的臨界 電壓變異而有相當大的變化，這種現象會造成有機發光二 極體的發光亮度不穩定或是不易控制的缺點，相對而言， 本實施例的驅動電流對於臨界電壓變異所產生的變化，就 穩定很多，換言之’本發明之驅動電流幾乎不受臨界電壓 變異的影響。 參閱圖7’假設當-有機發光二極體長時間操作下，因 材料發生老化導致該有機發光二極體的電壓降v〇l印隨之上 升時，由圖中可以觀察到，在本實施例中，該有:發光二 13 201007662 極體之驅動電流亦隨之增加’因此，可以補償該有機發光 二極體因老化而造成的亮度衰減。 由於本發明之驅動電流I〇LED僅與該資料電壓Vdata& 該有機發光二極體之電壓降V_A小有關，因此，相較於 習知之設計本發明具有下列優點： 具有補償該臨界電壓Vth變異的特性·201007662 IX. Description of the invention: [Technical field of the invention] The present invention relates to a pixel circuit, in particular to a method for compensating for a critical voltage variation of a thin film transistor and compensating for an organic light-emitting diode due to aging of the material. A pixel circuit with reduced brightness. [Prior Art] Nowadays, the use of an organic light-emitting diode (OLED) as a light source has been a fairly common application. The brightness of the organic light emitting diode is determined according to the driving current flowing therethrough. Therefore, for a driving circuit for driving the organic light emitting diode, the transistor and the organic light emitting diode are included. The change of related factors in the process often affects the luminous efficacy of the organic light-emitting diode. The effects on various organic light-emitting diodes are as follows: 1. The critical voltage of the transistor: Because of the long-term use of a panel Or because the process variation will cause the variation of the threshold voltage value, the driving current flowing through the organic light emitting diode will change. Therefore, the brightness of the organic light emitting diode will be affected when the panel When most of the pixel circuits are affected by the variation of the threshold voltage value, it is easy to cause the panel to appear uneven in brightness or a problem of brightness instability such as sometimes brighter and sometimes darker. Second, the power supply voltage of the drive circuit: When applied to a large-size panel, as the signal line is elongated, the internal resistance is gradually increased, which will cause the power supply voltage of the drive circuit to have an attenuation effect of 201007662, called IR-drop. Effect, this effect will cause the driving current to drop, thus making the brightness of the large-sized panel uneven. Third, the aging effect of the organic light-emitting diode: due to the phenomenon of material aging, the organic light-emitting diode is operated under a long time, It may happen that the voltage drop gradually rises to affect the magnitude of the drive current. Therefore, if the organic light-emitting diode is aged due to long-term operation, and thus the luminous efficiency is lowered, even if the driving current is as expected, the desired brightness cannot be produced. If the luminous efficiency of the three colors of RGB is different, the problem of color shift will occur. In view of the above factors, there are related technologies and improvements, such as: "AMOLED pixel circuit with electronic compensation of luminance degradation" proposed by the University of Waterloo in Canada in 2007. Seoul University of Korea in IEEE Electron "A new a-Si: H TFT pixel circuit compensating the threshold voltage shift of a-Si: H TFT and OLED for active matrix OLED", and 2005 Taiwan Jiaotong University in IEEE/OSA Journal of Display "A new pixel circuit for driving organic light emitting diodes with low temperature polycrystalline thin film transistors". In these related cases, in order to solve the problems caused by the above various factors, the circuit structure is often too complicated, so that the number of components in the pixel circuit has a large number of components, which leads to a decrease in the aperture ratio and affects the organic 201007662 / Luminous efficiency of light-emitting diodes. Therefore, how to effectively improve the problems caused by various factors and at the same time reduce the influence on the luminous efficiency of the organic light-emitting diode is a very important issue. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a halogen circuit comprising: an organic light emitting diode having an anode and a cathode; and a driving circuit comprising: a first transistor 'and a second a transistor, each of the transistors has a first end, a second end, and a control end that determines whether the first end and the second end are conductive; a capacitor; a data voltage switch; and a reference voltage switch Wherein the anode of the organic light emitting diode is electrically connected to a first power supply voltage, the second end of the first transistor and the second end of the second transistor, the control end of the second transistor, a cathode of the organic light emitting diode is electrically connected, and a control end of the first transistor is electrically connected to one end of the capacitor, and a first end of the second transistor is electrically connected to another end of the capacitor, the first transistor The first end is electrically connected to a second power voltage, the data voltage switch receives a data voltage, and receives control of a first control signal to determine whether to output the data to the control end of the first transistor , the The reference voltage switch receives a reference voltage and receives control of a second control signal to determine whether to output the reference voltage to the first terminal of the second transistor. In addition, another object of the present invention is to provide a driving circuit comprising 7 201007662 a first transistor, and a second transistor, each transistor having a first end, a second end, and a determining the first a control end of whether the one end and the second end are conductive; a capacitor; a data voltage switch; and a reference voltage switch; wherein 'the second end of the first transistor and the second end of the second transistor, the The control end of the second transistor is electrically connected, the control end of the first transistor is electrically connected to one end of the capacitor, and the first end of the second transistor is electrically connected to the other end of the capacitor, the first electric crystal Zhao The first end is electrically connected to a second power voltage, and the data voltage switch receives a data voltage and receives control of a first control signal to determine whether to output the data voltage to the control end of the first transistor. The reference voltage switch receives a reference voltage and receives control of a second control signal to determine that the reference voltage is read to the first end of the second transistor. According to another aspect of the present invention, a pixel circuit includes a light-emitting element having an anode and a cathode, and a driving circuit comprising: a transistor, each of the transistors determining the first end and the first a first transistor, and a second control terminal having a first terminal, a second terminal, and a terminal; a capacitor; a data voltage switch; and a 201007662 reference voltage switch; wherein the light component The anode is electrically connected to a first power supply voltage, and the second end of the first transistor is electrically connected to the second end of the second transistor, the control end of the second transistor, and the cathode of the light emitting element. a control terminal of the transistor is electrically connected to one end of the capacitor, and a first end of the second transistor is electrically connected to the other end of the capacitor, and a first end of the first transistor is electrically connected to a second power voltage. The data voltage switch receives a data voltage and receives control of a first control signal to determine whether to output the data voltage to a control terminal of the first transistor, the reference voltage switch receiving a reference voltage, Receiving a second control signal to the control to determine whether to output the reference voltage to the first terminal of the second transistor. The above and other technical contents, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments. Referring to FIG. 1 , a preferred embodiment of the present invention includes an organic light emitting diode ( 〇 LED ) 8 and a driving circuit 9 . The driving circuit 9 includes a first transistor 91 and a second transistor 92 . A capacitor 95, a data voltage switch 98, and a reference voltage switch 99, wherein in the embodiment, the data voltage switch 98 is a third transistor 93, and the reference voltage switch 99 is a fourth transistor 94. . The first to fourth transistors 91 to 94 are N-type thin film transistors (TFTs). Wherein each of the transistors 91 to 94 includes a first end, a second end, and a control end that determines whether the first stage and the second end are conductive. The organic light-emitting body 8 has an anode and a cathode. . 9 201007662 The second end of the first transistor 91 is electrically connected to the second end of the second transistor 92, the control end of the second transistor 92, and the cathode of the organic light emitting diode 8 (hereinafter referred to as A point); the control end of the first transistor 91 is electrically connected to one end of the capacitor 95 and the second end of the third transistor 93 (hereinafter referred to as point B); the first end of the second transistor 92 The other end of the capacitor 95 is electrically connected to the second end of the fourth transistor 94 (hereinafter referred to as point c). The first end of the first electrode body 91 is electrically connected to a second power voltage Vss. The control terminal of the third transistor 93 receives a first control signal Vseu, the first terminal of the third transistor 93 receives a data voltage Vdata, and the control terminal of the fourth transistor 94 receives a second control signal VsEL2. The first end of the fourth electric day body 94 receives a reference voltage vREF, and the anode of the organic light emitting diode 8 is electrically connected to a first power supply voltage VDD. The timing diagram of the preferred embodiment is shown in FIG. 2, and can be divided into three phases: I. Data input phase: Referring to FIG. 1, 2', the first control signal vSEL1 and the second control signal VSEL2 are set to be high. The potential, the reference voltage VREF is set to a low reference voltage Vref_l ' Therefore, the third and fourth transistors 93, 94 will be turned on, because VREF_L and VDATA are both low at this time, so the voltage across the capacitor 95 V95 will discharge through the Vref terminal and the VDATA terminal. The equivalent circuit diagram is shown in Figure 3. After the capacitor 95 is discharged for a period of time, the voltage at point C continues to drop until the voltage difference between point C and point A is greater than the threshold voltage value of the second transistor 92, Vth, 92 (because the second transistor 92 The gate voltage is electrically connected to point A 10 201007662 v), and the second transistor 92 will be turned on 'at this time, entering the compensation phase. II. Compensation phase: Referring back to FIGS. 1 and 2, after the second transistor 92 is turned on, the second control signal VSEL2 is set to a low potential, and therefore, the fourth transistor 94 is turned off. The gate voltage of the second transistor 92 is electrically connected to point A, so that one end of the capacitor 95 (ie, point C) will be read and charged to Vg, 92 - VTH 92, and the equivalent circuit diagram is as shown in FIG. The electric point of ^, can be expressed as follows: = VC, 92 - ^TH, 92 = ^A~ Kh, 92 = ^DD ~ ^OLED ~ ^TH,92 where 'VOLED is the organic light-emitting diode 8 What is the power? At the same time 'because the third transistor 93 is turned on', the data voltage vdata will be transmitted to point b. After the voltage at point c is charged to Vdd_v〇led_VtH92, since the gate voltage and the source voltage difference v of the second transistor 92 are increased by φ, 92 is smaller than the threshold voltage VTH, 92 of the first transistor, The second transistor 92 will be turned off again and enter the initial stage. It is worth noting that since the capacitor 95 has no discharge path for discharging, the voltage V95 of the valley is the voltage difference between the voltage V of point B and the voltage of point C, before entering the light-emitting phase, as shown in the following equation: V95 ==VDATA ~(VDD-vOLED-vm^)^vDATA _v〇D +v〇LED +Vth^ For the convenience of the following description, we assume that the voltage at point C is 〇, 11 201007662 and the voltage at point B is VdaTA— VdD + V〇LED + VtH, 92. III. Illumination phase: Referring to FIG. 1 and FIG. 2', the reference voltage Vref is set to the south reference potential VREF_H, and the first control signal VSEL1 is set to a low potential, so that the third transistor 93 is turned off, and then The second control signal Vs EL2 is set to a south potential 'so that the fourth transistor 92 is turned on'. Therefore, the high reference potential Vref_h will be transmitted to the C point, and the other end of the capacitor 95 (ie, point B) The voltage will jump to the same amount to ^ 乂 ^ to a VdD + V 〇 LED + VtH, 92, while the B point voltage Vb is also the gate voltage of the first transistor VG, 91, the equivalent circuit diagram is shown in Figure 5. As shown, a driving current Idrive flowing from the organic light emitting diode 8 to the second end of the first transistor 91 is generated as follows: ^OLED = ^9l (^GS, 91 ~ ^Τ«, 9ΐ) =^9l(^G,91 — ^5,91 — ^ΓΗ,9ΐ) =K91(VREF _H +V〇ATA ~VDD +V〇LE〇+VTH 92 —^77/,91 — ^ss) According to the above The formula assumes that the first transistor 91 has the same threshold voltage as the second transistor 92, that is, V TH, 91 = VtH, 92; _ additionally * when the south reference potential Vref_h is set to When the voltage of the first power supply voltage VDD is the same and Vss is OV, the above formula can be simplified as follows: ^OLED = ^9\ ^DATA + ^OLED ) According to the above current formula, it can be known that the organic light flows through The driving current I OLED of the diode 8 is independent of the first and second power supply voltages VDD, Vss, and 12 201007662, the threshold voltage vTH, 91 of the first transistor 91. Therefore, the driving current i0LED flowing through the organic light-emitting diode 8 is determined only by the magnitude of the data voltage vDATA during the light-emitting phase, and further, when the vOLED is increased due to the aging of the organic light-emitting body 8 material, the opposite The current amount i 〇 LED of the organic light-emitting body 8 is also increased, and therefore, the phenomenon that the organic light-emitting diode 8 is attenuated due to aging of the material can be compensated for. It should be noted that 'this embodiment can be used to drive other current-driven light-emitting elements 'for example, light-emitting diodes (LEDs)' and these transistors can be used in addition to driving the organic light-emitting diodes 8 91~94 may be an N-type metal oxide semiconductor (pM〇s) in addition to the N-type TFT. This embodiment uses a circuit simulation method to verify the compensation effect. Figure 6 shows the driving current and data voltage of the organic light-emitting diode by inputting various data voltage values 'assuming that the transistors in the circuit have a threshold voltage variation of -0.3 volts, volts volts, + 〇3 volts, respectively. Transfer curve. From Fig. 6, it can be observed that the conventional driving current has a considerable change according to different threshold voltage variations, which may cause the luminance of the organic light emitting diode to be unstable or difficult to control. In other words, the driving current of the present embodiment is much more stable with respect to changes in the threshold voltage variation. In other words, the driving current of the present invention is hardly affected by the critical voltage variation. Referring to FIG. 7', it is assumed that when the organic light-emitting diode is operated for a long time, the voltage drop of the organic light-emitting diode is increased due to aging of the material, as can be observed from the figure, in this embodiment. In the example, the light source has a luminous current of 13 201007662. Therefore, the brightness of the organic light-emitting diode due to aging can be compensated for. Since the driving current I 〇 LED of the present invention is only related to the voltage drop V_A of the data voltage Vdata & the organic light emitting diode, the present invention has the following advantages compared with the conventional design: having the compensation of the threshold voltage Vth variation Characteristics·
當一面板在長時間操作下或是因為製程上的差異 ，所產生的臨界電壓VTH差異，可能會影響該有機發 光一極體8上的驅動電流I0LED大小，進而造成一面板 上發光亮度的不均勻或是不穩定的情形，然而利用本 發明畫素電路之面板，可以避免因臨界電壓vTH的變 異所造成的亮度問題。 一、能應用於大尺寸面板上： 由於本發明之畫素電路的驅動電流i〇led與第一、 第二電源電壓VDD、VSS無關，因此，當應用於大尺寸 面板時’可能因為訊號線過長所引起的IR_dr〇p效應， 將不會影響該驅動電流IOLED，因此，不會對該有機發 Ο 光一極體8的發光亮度造成影響。 三、不會影響該有機發光二極體8的發光效率：When a panel is operated for a long time or because of a difference in the process, the difference in the threshold voltage VTH generated may affect the driving current I0LED on the organic light-emitting body 8, thereby causing the brightness of the light on one side of the board. Uniform or unstable, however, with the panel of the pixel circuit of the present invention, the brightness problem caused by the variation of the threshold voltage vTH can be avoided. 1. It can be applied to a large-sized panel: Since the driving current i〇led of the pixel circuit of the present invention is independent of the first and second power supply voltages VDD and VSS, when applied to a large-sized panel, it may be due to a signal line. The IR_dr〇p effect caused by the excessive length will not affect the driving current IOLED, and therefore, the luminance of the organic light-emitting body 8 will not be affected. Third, it will not affect the luminous efficiency of the organic light-emitting diode 8:
由於本發明之畫素電路的驅動電流1〇1^〇與該有機 發光一極體的電壓降V〇LED有關’因此’當一使用本畫 素電路為光源之面板，内部發生有機發光二極體因為 -長久使用而產生材料老化，進而使得該有機發光二極 體的電壓降VOLED上升時，將會使得該驅動電流IOLED 14 201007662 - 纟1¾著上升，因此，該有機發光二極體的亮度將不會 隨著材料老化而衰減，進而保持穩定的發光效率，因 此，當本發明之畫素電路應用於RGB顯示裝置時可 以避免因A RGB三色發光二極體因為出現發光效率不 一致而導致色偏的問題發生。 四、元件數量較少： 相較於習知之設計，本發明僅僅利用四個電晶體 與一個電容，凡件數量相對而言較少，因此對於該有 〇 機發光二極體的開口率影響較小，也就是說，本發明 可以有效降低對於該有機發光二極體發光效率的影響 〇 綜上所述，本發明之實施例可以確保畫素電路中該驅 動電流將不會受到臨界電壓變異、IR_dr〇p效應及有機發光 二極體老化等因素而改變，同時，又可有效降低對於該有 機光二極體發光效率的影響程度，因此確實能達成本發明 之目的。 _ 惟以上所述者，僅為本發明之較佳實施例而已，當不 能以此限定本發明實施之範圍，即大凡依本發明申請專利 範圍及發明說明内容所作之簡單的等效變化與修飾，皆仍 屬本發明專利涵蓋之範圍内。 【圖式簡單說明】 圖1是本發明之較佳實施例之電路示意圖； 圖2是該較佳實施例之時序圖； 圖3是該較佳實施例之資料輸入階段之等效電路示意 15 201007662 |g| · 圍， 圖4是該較佳實施例之補償階段之等效電路示意圖； 圖5是該較佳實施例之發光階段之等效電路示意圖； 圖6是不同資料電壓對於不同臨界電壓變異之轉移曲 線圖；及 圖7是該有機發光二極體電壓降與驅動電流之對應關 係圖。Since the driving current of the pixel circuit of the present invention is related to the voltage drop of the organic light emitting body V〇LED, "therefore, when a panel using the pixel circuit as a light source is used, an organic light emitting diode is generated internally. When the material ages due to long-term use, and the voltage drop of the organic light-emitting diode VOLED rises, the driving current IOLED 14 201007662 - 纟13⁄4 rises, and therefore, the brightness of the organic light-emitting diode It will not attenuate with the aging of the material, thereby maintaining stable luminous efficiency. Therefore, when the pixel circuit of the present invention is applied to an RGB display device, it is possible to avoid the inconsistent luminous efficiency due to the occurrence of the A RGB three-color light-emitting diode. The problem of color shift occurs. Fourth, the number of components is small: Compared with the conventional design, the present invention only uses four transistors and one capacitor, and the number of parts is relatively small, so the influence on the aperture ratio of the LED light-emitting diode is relatively small. Small, that is, the present invention can effectively reduce the influence on the luminous efficiency of the organic light emitting diode. As described above, embodiments of the present invention can ensure that the driving current in the pixel circuit will not be subjected to the threshold voltage variation, The IR_dr〇p effect and the aging of the organic light-emitting diode change, and at the same time, the degree of influence on the luminous efficiency of the organic photodiode can be effectively reduced, so that the object of the present invention can be achieved. The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, that is, the simple equivalent changes and modifications made by the scope of the present invention and the description of the invention. All remain within the scope of the invention patent. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a preferred embodiment of the present invention; FIG. 2 is a timing diagram of the preferred embodiment; FIG. 3 is an equivalent circuit diagram 15 of the data input stage of the preferred embodiment. FIG. 4 is an equivalent circuit diagram of the compensation phase of the preferred embodiment; FIG. 5 is an equivalent circuit diagram of the illumination phase of the preferred embodiment; FIG. 6 is a different data voltage for different criticalities. The transfer curve of the voltage variation; and FIG. 7 is a corresponding relationship between the voltage drop of the organic light emitting diode and the driving current.
16 201007662 ·- 【主要元件符號說明】 8 ，* ……·有機發光二極體 <· X φ Κ « …-第四電晶體 9… "* μ < 4驅動電路 9 5 f" * * …電容 91 *· ………第一電晶體 9 8 …" +…資料電壓開關 92 - .....…第二電晶體 99..... —參考電壓開關 93· .......第三電晶體16 201007662 ·- [Description of main component symbols] 8 ,* ......·organic light-emitting diodes<· X φ Κ « ...-fourth transistor 9... "* μ < 4 drive circuit 9 5 f" * * ...capacitor 91 *· .........first transistor 9 8 ..." +... data voltage switch 92 - ........ second transistor 99..... - reference voltage switch 93 ... ....third transistor
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