KR20070027861A - Driver circuit for oled(organic light emitting diodes - Google Patents
Driver circuit for oled(organic light emitting diodes Download PDFInfo
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- KR20070027861A KR20070027861A KR1020050079718A KR20050079718A KR20070027861A KR 20070027861 A KR20070027861 A KR 20070027861A KR 1020050079718 A KR1020050079718 A KR 1020050079718A KR 20050079718 A KR20050079718 A KR 20050079718A KR 20070027861 A KR20070027861 A KR 20070027861A
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3275—Details of drivers for data electrodes
- G09G3/3283—Details of drivers for data electrodes in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3216—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using a passive matrix
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2310/00—Command of the display device
- G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
- G09G2310/0243—Details of the generation of driving signals
- G09G2310/0248—Precharge or discharge of column electrodes before or after applying exact column voltages
Abstract
Description
도 1은 종래의 PM(Passive Matrix) 유기EL 표시장치의 데이타 구동부를 도시한 것이다.1 illustrates a data driver of a conventional PM (Passive Matrix) organic EL display device.
도 2는 본 발명의 일실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.2 illustrates a data driver of a PM organic EL display device according to an exemplary embodiment of the present invention.
도 3은 도 2에 도시된 데이터 구동부의 타이밍(Timing)도를 도시한 것이다.FIG. 3 illustrates a timing diagram of the data driver shown in FIG. 2.
도 4는 본 발명의 다른 실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.4 illustrates a data driver of a PM organic EL display device according to another exemplary embodiment of the present invention.
도 5는 본 발명의 다른 실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.5 illustrates a data driver of a PM organic EL display device according to another exemplary embodiment of the present invention.
도 6은 본 발명의 다른 실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.6 illustrates a data driver of a PM organic EL display device according to another exemplary embodiment of the present invention.
도 7은 본 발명의 일실시예에 따른 AM(Active Matrix) 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.7 illustrates a data driver of an AM (active matrix) organic EL display device according to an exemplary embodiment of the present invention.
도 8은 종래의 유기 EL 표시장치와 본 발명의 일실시예에 따른 유기 EL 표시장치의 데이터 구동부에서의 전류변화율을 나타낸 것이다.8 shows a current change rate in a conventional organic EL display device and a data driver of an organic EL display device according to an embodiment of the present invention.
<도면의 주요 부분에 대한 부호의 설명><Explanation of symbols for the main parts of the drawings>
10: 구동열 20: 유기 EL 패널10: driving heat 20: organic EL panel
R41, R51: 가변저항부 R52: 고정저항부R41, R51: Variable resistor section R52: Fixed resistor section
본 발명은 유기 EL(electro-luminescence)소자들을 사용하는 유기 EL 표시장치에 관한 것으로서, 더욱 상세하게는 데이타 구동부의 회로 구조에 관한 것이다.BACKGROUND OF THE
일반적으로, 유기 EL 소자들을 사용하는 발광 표시장치는 유기 EL 소자들이 매트릭스형태로 배치된다. 유기EL소자들은, 예를 들면 행들의 소자들을 주사선구동회로(행구동회로)에 의해 열방향으로 순차적으로 주사하고 행구동회로에 의해 선택된 특정 행의 소자들에 구동전류를 선택적으로 공급함으로써 발광된다. In general, in a light emitting display device using organic EL elements, organic EL elements are arranged in a matrix form. The organic EL elements emit light, for example, by sequentially scanning the elements of the rows in the column direction by the scan line driver circuit (row driver circuit) and selectively supplying the driving current to the elements of a particular row selected by the row driver circuit.
구동전류는 데이터선구동회로(열구동회로)에 의해 공급된다. 이러한 유기 EL표시장치는 백라이트(backlight)를 요하지 않는 자가발광표시장치이다.The drive current is supplied by the data line driver circuit (column driver circuit). Such an organic EL display device is a self-luminous display device that does not require a backlight.
여기서, 구동전류는 소자들간의 공정 및 주변요건에 따라 특성의 변화가 생기게 되고, 이러한 특성변화는 채널간의 전류편차를 발생시킨다.Here, the driving current is changed in characteristics depending on the process and peripheral requirements between the elements, this characteristic change generates a current deviation between the channels.
채널간의 전류편차는 표시 화면의 휘도 불균일이나, 암선 또는 명선을 발생시키는 요인이 된다.The current deviation between the channels is a factor that causes uneven brightness of the display screen and dark lines or bright lines.
따라서, 최근에는 인접 채널간의 전류편차를 해소시키기 위해서 유기 EL 표 시장치의 구동부의 미러단에 보상용 피드백 저항을 연결하여 사용한다.Therefore, in recent years, in order to solve the current deviation between adjacent channels, a compensation feedback resistor is connected to the mirror end of the driving unit of the organic EL display device.
도 1은 종래의 PM(Passive Matrix) 유기EL 표시장치의 데이타 구동부를 도시한 것이다.1 illustrates a data driver of a conventional PM (Passive Matrix) organic EL display device.
도 1에 도시된 바와 같이, 유기EL 표시장치의 데이타 구동부는 데이터선구동회로(열구동회로, 20)이며, 유기 EL 표시장치의 구동부의 미러단에 보상용 피드백 저항들(R11, R12 … R1n)이 연결되고, 유기 EL 소자들(D11, D12 … D1n)로 구성된 유기 EL 패널(10)이 열구동을 위한 스위치들(S11, S12 … S1n)에 의해 연결된다.As shown in Fig. 1, the data driver of the organic EL display device is a data line driver circuit (column driver circuit 20), and compensation feedback resistors R11, R12, ... R1n are provided at the mirror end of the driver of the organic EL display device. Are connected, and the
여기서, 피드백 저항들(R11, R12 … R1n)은 트랜지스터들(PM11, PM12 … PM1n)의 문턱전압(Vth)의 변화에 따른 트랜지스터간의 전류편차를 줄이는 역할을 담당하게 된다.Here, the feedback resistors R11, R12, ... R1n play a role of reducing the current deviation between transistors according to the change of the threshold voltage Vth of the transistors PM11, PM12, ... PM1n.
그러나, 종래의 피브백 저항은 고정값을 갖는 고정저항을 사용한다. 이러한 고정저항의 사용은 다음과 같은 문제를 야기시키게 된다.However, the conventional feedback feedback uses a fixed resistor having a fixed value. The use of such a fixed resistor causes the following problems.
유기 EL 소자들(D11, D12 … D1n)의 구동 시, 즉 전류 구동을 할 경우 프리차지(Precharge) 기간이 존재한다. 프리차지 기간의 전류값은 디스플레이 기간의 전류값에 비해 최대 10배까지 증가하게 된다. A precharge period exists when the organic EL elements D11, D12, ... D1n are driven, that is, when the current is driven. The current value of the precharge period is increased up to 10 times compared to the current value of the display period.
따라서, 기존의 고정된 저항을 사용하게 될 경우 프리차지 기간에 노드(N11, N12 … N1n)에서의 전압강하가 디스플레이 기간에서의 전압강하 보다 최대 10배까지 증가하므로, 트랜지스터들(PM11, PM12 … PM1n)이 선형영역으로 들어가게 되어 전류 미러 회로로서의 정상적인 동작을 하기가 어렵게 되는 문제가 있게 된다. Therefore, when the existing fixed resistor is used, the voltage drops at the nodes N11, N12 ... N1n increase up to 10 times the voltage drop in the display period in the precharge period, so that the transistors PM11, PM12... PM1n) enters the linear region, which makes it difficult to operate normally as a current mirror circuit.
본 발명에 따른 유기 EL 표시장치의 구동회로를 제안하는 목적은, 유기 EL 표시장치의 채널간의 전류 편차를 줄이는 데에 있다.An object of the present invention is to reduce a current variation between channels of an organic EL display device.
본 발명의 다른 목적은, 유기 EL 표시장치의 프리차지 기간 동안에 피드백 저항에 의한 전압강하가 상대적으로 너무 커지는 것을 방지하기 위한 구동회로를 제공하는 데 있다.Another object of the present invention is to provide a driving circuit for preventing the voltage drop caused by the feedback resistor from becoming too large during the precharge period of the organic EL display device.
상술한 과제를 해결하기 위한 본 발명에 따른 유기 EL(Electro Luminescence) 표시장치의 구동회로는, 구동 인접 채널간의 전류편차를 줄이기 위해 전류미러단에 피드백용 저항을 설치하되, 상기 유기 EL 표시장치의 프리차지(Precharge) 기간에 상기 저항에 의한 전압강하가 커지는 것에 능동적으로 대응이 가능하도록, 상기 저항은 가변소자로 형성하는 것을 특징으로 한다.In order to solve the above-mentioned problems, a driving circuit of an organic electroluminescence (EL) display device according to the present invention is provided with a feedback resistor in a current mirror stage in order to reduce a current deviation between adjacent driving channels. The resistor may be formed of a variable element so as to be able to actively respond to the increase in the voltage drop caused by the resistor during the precharge period.
여기서, 상기 가변소자는 MOSFET(Metal-Oxide-Semiconductor Field Effect Transistor)인 것이 바람직하다.Here, the variable element is preferably a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor).
여기서, 상기 가변소자는 하나 이상의 MOSFET이 병렬 연결되어 구성되는 것이 바람직하다.Here, the variable element is preferably configured by one or more MOSFETs connected in parallel.
여기서, 상기 하나 이상의 MOSFET는 채널폭(W) 및 채널길이(L)가 동일한 트랜지스터인 것이 더욱 바람직하다.Here, the at least one MOSFET is more preferably a transistor having the same channel width (W) and channel length (L).
여기서, 상기 가변소자는 고정저항값을 갖는 고정저항부와 가변저항값을 갖 는 가변정항부가 병렬 연결되어 구성되는 것이 바람직하다.Here, the variable element is preferably composed of a fixed resistance portion having a fixed resistance value and a variable constant portion having a variable resistance value are connected in parallel.
또한, 본 발명에 따른 유기 EL(Electro Luminescence) 표시장치의 구동회로는, 구동 인접 채널간의 전류편차를 줄이기 위해 전류미러단에 피드백용 저항을 설치하되, 상기 유기 EL 표시장치의 프리차지(Precharge) 기간에 상기 저항에 의한 전압강하가 커지는 것에 능동적으로 대응이 가능하도록, 상기 저항과 병렬로 스위치를 연결하여 상기 스위치의 스위칭에 의해 바이패스되는 것을 특징으로 한다.In addition, in the driving circuit of the organic EL display device according to the present invention, in order to reduce the current deviation between driving adjacent channels, a feedback resistor is provided at the current mirror stage, and the precharge of the organic EL display device is performed. The switch may be bypassed by switching the switch by connecting the switch in parallel with the resistance so as to actively respond to the increase in the voltage drop caused by the resistance in the period.
여기서, 상기 스위치는 BJT(Bipolar Junction Transistor) 또는 CMOS(Complementary Metal Oxide Semiconductor)로 구현되는 것이 바람직하다.Here, the switch is preferably implemented with a Bipolar Junction Transistor (BJT) or a Complementary Metal Oxide Semiconductor (CMOS).
이하, 첨부된 도면을 참조하여 본 발명에 따른 바람직한 실시예를 상세히 설명하고자 한다.Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
본 발명에 따른 유기 EL 표시장치의 구동회로에 사용되는 트랜지스터는 MOSFET 트랜지스터를 활용한다. MOSFET 트랜지스터는 게이트에 인가되는 전압의 크기 및 극성에 따라서, 소오스로부터 드레인으로 또는 그 역으로 흐르는 전류의 양 및 방향이 결정되는 특성을 갖는다. 이러한 증폭 소자로는 바이폴라 정션 트랜지스터(BJT), 정션 전계 효과 트랜지스터(JFET), 금속 산화막 반도체 전계 효과 트랜지스터(MOSFET) 및 금속 반도체 전계 효과 트랜지스터(MESFET) 등이 있다.The transistor used in the driving circuit of the organic EL display device according to the present invention utilizes a MOSFET transistor. MOSFET transistors have the property of determining the amount and direction of current flowing from source to drain or vice versa, depending on the magnitude and polarity of the voltage applied to the gate. Such amplification elements include bipolar junction transistors (BJTs), junction field effect transistors (JFETs), metal oxide semiconductor field effect transistors (MOSFETs), and metal semiconductor field effect transistors (MESFETs).
이하의 설명에서는 MOSFET을 중심으로 설명하고자 한다. 비록, 본 명세서에서는 MOSFET을 중심으로 설명하나, 본 발명의 개념과 범위가 MOSFET으로 한정되는 것은 아니다. 또한, 이하의 설명에서는 P형 MOSFET를 중심으로 설명하지만, 본 발 명의 개념을 N형 MOSFET에도 적용할 수 있음은 당업계에 자명하다.In the following description, the description will focus on the MOSFET. Although described herein with reference to the MOSFET, the concept and scope of the present invention are not limited to the MOSFET. In addition, the following description focuses on the P-type MOSFET, but it is apparent in the art that the concept of the present invention can be applied to the N-type MOSFET.
도 2는 본 발명의 일실시예에 따른 PM(Passive Matrix) 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.2 illustrates a data driver of a passive matrix (EL) organic EL display device according to an embodiment of the present invention.
도시된 바와 같이, 유기EL 표시장치의 데이타 구동부는 데이터선구동회로(열구동회로, 20)이며, 유기 EL 표시장치의 구동부의 미러단에 보상용 피드백 가변저항들(PM31, PM32 … PM3n)이 연결되고, 유기 EL 소자들(D21, D22 … D2n)로 구성된 유기 EL 패널(10)이 열구동을 위한 스위치들(S21, S22 … S2n)에 의해 연결된다.As shown, the data driver of the organic EL display device is a data line driver circuit (column driver circuit 20), and compensating feedback variable resistors PM31, PM32, PM3n are connected to the mirror terminal of the driver of the organic EL display device. Then, the
여기서, 가변저항들(PM31, PM32 … PM3n)은 구동 트랜지스터들(PM21, PM22 … PM2n)의 문턱전압(Vth)의 변화에 따른 트랜지스터간의 전류편차를 줄이는 역할을 담당하게 된다.Here, the variable resistors PM31, PM32... PM3n play a role of reducing the current deviation between transistors according to the change of the threshold voltage Vth of the driving transistors PM21, PM22.
유기 EL 소자들((D21, D22 … D2n)의 밝기는 흐르는 전류량에 의해서 결정된다. 따라서, 같은 계조(Gray)에서는 동일한 전류가 흐르도록 하는 것이 바람직하다. 구동 트랜지스터들(PM21, PM22 … PM2n)의 문턱전압(Vth)인 드레인-소스간 ㅈ전압(Vds)의 변화에 따라 전류차가 크지 않도록 하기 위해서 구동 트랜지스터들(PM21, PM22 … PM2n)은 포화 영역에서 동작하도록 한다. The brightness of the organic EL elements (D21, D22, ... D2n) is determined by the amount of current flowing. Therefore, it is preferable that the same current flows in the same gray (Gray) driving transistors PM21, PM22, PM2n. The driving transistors PM21, PM22... PM2n operate in the saturation region so that the current difference does not become large due to the change of the drain-source voltage Vds, which is the threshold voltage Vth of.
이때 흐르는 구동 트랜지스터들(PM21, PM22 … PM2n)의 드레인-소스간 전류(Ids)는 다음 수학식 1과 같다.The drain-source current Ids of the driving transistors PM21, PM22... PM2n flowing at this time are represented by
(단,P1,P2,P3에서 몸체 효과는 무시하였다.)(But body effects are ignored in P1, P2, and P3.)
여기서,μp는 정공반전층에서 정공의 이동도이고, Cox는 단위면적당 산화막 캐패시턴스이며, W는 채널폭이고, L은 채널길이이고, VN는 노드(N21, N22 … N2n) 전압이며, Vth는 트랜지스터의 문턱전압이다.Where μ p is the mobility of holes in the hole inversion layer, Cox is the oxide capacitance per unit area, W is the channel width, L is the channel length, V N is the node (N21, N22… N2n) voltage, Vth Is the threshold voltage of the transistor.
이상적인 경우 각각의 구동 트랜지스터들(PM21, PM22 … PM2n)의 Vth는 동일하여야 하지만 공정상의 불규칙에 의해서 변화가 생기게 된다. 이러한 변화는 전류의 편차를 발생시킨다. 즉, 각각의 구동 트랜지스터들(PM21, PM22 … PM2n)의 Ids 차가 발생하게 된다.In an ideal case, the Vth of each of the driving transistors PM21, PM22... PM2n should be the same, but a change occurs due to process irregularities. This change causes a deviation of the current. That is, the difference in Ids of each of the driving transistors PM21, PM22... PM2n is generated.
구동 트랜지스터(PM21)의 Vth가 ΔVth1 만큼의 전압변화가 생겼을 경우, 위 수학식 1에서 |Vth|가 증가하기 때문에 궁극적으로 Ids는 ΔIds1만큼 감소하게 된다. When Vth of the driving transistor PM21 is changed by ΔVth1, Ids ultimately decreases by ΔIds1 because | Vth | is increased in
ΔIds1만큼 감소는 노드(N21)에서의 전압은 기존에 비해서 ΔIds1*R1 만큼 증가하게 된다. 이는 수학식 1에서 VN1+(ΔIds1*R1 )-Vdata 만큼 전압을 증가시키게 되고 다시 Ids1의 전류가 증가하게 된다. 즉 공정상의 불균일에 의한 Vth의 변화가 가변저항 R1(PM23)의 피드백 효과에 의해서 감소되게 된다.The decrease by ΔIds1 causes the voltage at the node N21 to increase by ΔIds1 * R1 as compared with the conventional one. This increases the voltage by V N1 + (ΔIds1 * R1) -Vdata in
또한, 가변저항(PM23)은 Vcontrol의 값에 의해 가변값을 갖으며 동작된다.In addition, the variable resistor PM23 is operated with a variable value by the value of Vcontrol.
이러한, 가변값을 갖는 가변저항(PM23)은 다음과 같은 역할을 수행한다.The variable resistor PM23 having a variable value performs the following role.
도 3을 참조하여 설명하면, 일반적으로 유기 EL 표시장치는 홀드기간, 방전기간, 프리차지(Precharge) 기간 및 디스플레이 기간의 과정을 거치게 되는데, 프 리차지 기간에는 디스플레이(Display) 기간에 비해 전류가 최대 10배까지 필요하게 된다. Referring to FIG. 3, in general, an organic EL display device undergoes a process of a hold period, a discharge period, a precharge period, and a display period. In the precharge period, the current is larger than the display period. Up to 10 times is needed.
즉, 전류가 최대 10배까지 흐르게 되면, 노드(N21) 지점에서 프리차지 기간에는 디스플레이(Display) 기간에 비해 전압강하가 최대 10배까지 생기는 것을 의미한다. 이렇게 되면 트랜지스터(PM21)이 선형 영역으로 들어가기 때문에 정확한 전류 구동을 하기가 어렵다.That is, when the current flows up to 10 times, it means that the voltage drop occurs up to 10 times in the precharge period at the node N21 compared to the display period. In this case, since the transistor PM21 enters the linear region, accurate current driving is difficult.
따라서, 프리차지 기간 동안에는 Vcontrol 전압을 가변시켜 가변저항(PM23)의 저항값을 가변시켜준다. 즉 도 3에 도시된 바와 같이, 프리차지 기간 동안에 디스플레이 기간 동안의 제어전압 보다 낮은 제어전압을 인가한다.Therefore, the voltage value of the variable resistor PM23 is varied by varying the Vcontrol voltage during the precharge period. That is, as shown in FIG. 3, a control voltage lower than the control voltage during the display period is applied during the precharge period.
선형 영역에서 가변저항(PM23)의 저항값은 다음 수학식 2와 같이 표현된다.The resistance value of the variable resistor PM23 in the linear region is expressed by
여기서, Ron은 선형 영역에서의 가변저항값이고, μp는 정공반전층에서 정공의 이동도이고, Cox는 단위면적당 산화막 캐패시턴스이며, W는 채널폭이고, L은 채널길이이고, Vdd는 전원전압이며, Vcontrol은 제어전압이며, Vth는 트랜지스터의 문턱전압이다.Where Ron is the variable resistance in the linear region, μ p is the mobility of holes in the hole inversion layer, Cox is the oxide capacitance per unit area, W is the channel width, L is the channel length, and Vdd is the power supply voltage. Vcontrol is the control voltage and Vth is the threshold voltage of the transistor.
저항의 값은 대략 50uA의 전류가 흐를 경우, 노드(N21)에서 1V 이상의 전압강하가 생기도록 하는 것이 바람직하게 된다. The value of the resistance is preferably such that a voltage drop of 1V or more occurs at the node N21 when a current of approximately 50uA flows.
따라서, 가변저항(PM23, PM24 … PM2m)은 구동 트랜지스터(PM21, PM22 … PM2n)의 공정변화에 따른 불균일에 의한 각 채널간의 전류편차를 감소시켜 주는 피드백 저항으로서의 효과와, 프리차지 기간에서의 큰 전압강하를 방지하기 위한 효과를 가지게된다.Accordingly, the variable resistors PM23, PM24 ... PM2m have an effect as a feedback resistor that reduces current deviation between channels due to unevenness caused by process variations of the driving transistors PM21, PM22 ... PM2n, and has a large effect in the precharge period. It has an effect to prevent the voltage drop.
도 4는 본 발명의 다른 실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.4 illustrates a data driver of a PM organic EL display device according to another exemplary embodiment of the present invention.
도시된 바와 같이, 도 4은 도 2에 도시된 유기 EL 표시장치와 동일한 구조를 갖되, 가변저항부(R41)만이 다른 형태를 갖으며, 구동열의 1열만을 도시한 것이다.As shown in FIG. 4, FIG. 4 has the same structure as the organic EL display device shown in FIG. 2, but only the variable resistor portion R41 has a different form, and shows only one column of the driving column.
이러한 가변저항부(R41)는 가변저항의 저항값을 작게하기 위하여 트랜지스터(PM42, PM43 … PM4n)를 복수개 사용한 것이다. The variable resistor portion R41 uses a plurality of transistors PM42, PM43 ... PM4n to reduce the resistance of the variable resistor.
여기서, 구동부에 사용된 구동 트랜지스터(PM41)는 레이아웃(layout)상에서 매칭(matching)이 중요하기 때문에 가변저항으로 사용된 트랜지스터(PM42, PM43 … PM4n)의 채널폭(W) 및 채널길이(L)의 값을 동일하게 하는 것이 바람직하다.Here, since matching of the driving transistor PM41 used in the driving unit is important in layout, the channel width W and the channel length L of the transistors PM42, PM43 ... PM4n used as the variable resistors are important. It is preferable to make the value of equal.
도 5는 본 발명의 다른 실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.5 illustrates a data driver of a PM organic EL display device according to another exemplary embodiment of the present invention.
도시된 바와 같이, 도 5는 도 2에 도시된 유기 EL 표시장치와 동일한 구조를 갖되, 저항부만이 다른 형태를 갖으며, 구동열의 1열만을 도시한 것이다.As shown in FIG. 5, FIG. 5 has the same structure as the organic EL display device shown in FIG. 2, but only the resistance portion has a different form, and shows only one column of the driving column.
저항부는 가변저항부(R51)와 고정저항부(R52)가 병렬 연결된 구조를 갖는다.The resistor unit has a structure in which the variable resistor unit R51 and the fixed resistor unit R52 are connected in parallel.
여기서, 고정저항부(R52)는 저항값을 크게 하기 위해서 사용되며, 고정전압(Vset)에 의하여 제어된다. 반대로, 가변저항부(R52)는 저항값을 작게 하기 위해 서 사용된다. 즉, 이러한 구조는 저항의 가변 범위를 크게할 수 있어 본 발명을 구현하는데 있어 최적의 효과를 얻는 것이 가능하게 된다.Here, the fixed resistor portion R52 is used to increase the resistance value and is controlled by the fixed voltage Vset. On the contrary, the variable resistor portion R52 is used to reduce the resistance value. That is, such a structure can increase the variable range of the resistance, thereby obtaining an optimum effect in implementing the present invention.
도 6은 본 발명의 다른 실시예에 따른 PM 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.6 illustrates a data driver of a PM organic EL display device according to another exemplary embodiment of the present invention.
도시된 바와 같이, 도 6은 도 2에 도시된 유기 EL 표시장치와 동일한 구조를 갖되, 저항부만이 다른 형태를 갖는다.As shown, FIG. 6 has the same structure as the organic EL display shown in FIG. 2, except that only the resistance portion has a different form.
도시된 바와 같이, 저항부는 피드백 저항(R61, R62 … R6n)과 각각 병렬 연결된 바이패스(Bypass) 스위치(S71,S72 … S7n)을 연결한 구조를 갖는다. As shown, the resistor unit has a structure in which feedback resistors R61, R62 ... R6n are connected to bypass switches S71, S72 ... S7n connected in parallel, respectively.
여기서, 피드백 저항(R61, R62 … R6n)값은 바이패스 스위치(S71,S72 … S7n)가 온되는 경우에는 피드백 저항(R61, R62 … R6n)이 바이패스가 되기 때문에 저항이 아주 작아지게 된다. 프리차지 기간에는 바이패스 스위치(S71,S72 … S7n)를 도통시켜 저항값을 작게 하고, 디스플레이 기간에는 바이패스 스위치(S71,S72 … S7n)를 오픈시켜 저항값을 증가시킨다. Here, the feedback resistors R61, R62 ... R6n have a very small resistance because the feedback resistors R61, R62 ... R6n are bypassed when the bypass switches S71, S72 ... S7n are turned on. In the precharge period, the bypass switches S71, S72 ... S7n are conducted to decrease the resistance value, and in the display period, the bypass switches S71, S72 ... S7n are opened to increase the resistance value.
여기서, 피드백 저항(R61, R62 … R6n)은 상대적으로 큰 저항값을 갖도록 하는 것이 바람직하며, 저항의 배치는 레이아웃상 매칭을 고려해서 설정하는 것이 더욱 바람직하다.Here, it is preferable that the feedback resistors R61, R62, ... R6n have a relatively large resistance value, and the arrangement of the resistors is more preferably set in consideration of layout matching.
바이패스 스위치(S71,S72 … S7n)는 BJT(Bipolar Junction Transistor) 또는 CMOS(Complementary Metal Oxide Semiconductor)로 구현하는 것이 바람직하다.Bypass switches (S71, S72… S7n) are preferably implemented with a Bipolar Junction Transistor (BJT) or Complementary Metal Oxide Semiconductor (CMOS).
도 7은 본 발명의 일실시예에 따른 AM(Active Matrix) 유기 ＥＬ 표시장치의 데이터 구동부를 도시한 것이다.7 illustrates a data driver of an AM (active matrix) organic EL display device according to an exemplary embodiment of the present invention.
도 7에 도시된 AM(Active Matrix) 유기 ＥＬ 표시장치의 데이터 구동부는 도 2에 도시된 PM 유기 ＥＬ 표시장치의 데이터 구동부와 유사한 구조를 갖는다.The data driver of the AM (active matrix) organic EL display shown in FIG. 7 has a structure similar to that of the data driver of the PM organic EL display shown in FIG. 2.
다른 점은 구동부(PM71, PM72 … PM7n) 및 가변저항(PM81, PM82 … PM8n)을 제어하는 데이터 구동 전압(Vdata_1, Vdata_2 … Vdata_n) 및 제어전압(Vc_1, Vc_2 … Vc_n)이 각 구동열(20) 마다 개별적인 제어가 이루어지게 된다.The difference is that the data driving voltages Vdata_1, Vdata_2 ... Vdata_n and the control voltages Vc_1, Vc_2 ... Vc_n controlling the driving units PM71, PM72. Each control is controlled individually.
또 다른 점은 유기 EL 패널(10)의 유기 EL 소자를 발광시키기 위한 스위치(S71, S72 … S7n)가 유기 EL 패널(10) 내부에 위치하게 된다.Another point is that switches S71, S72 ... S7n for emitting the organic EL elements of the
결국, 도 7에 도시된 AM 유기 ＥＬ 표시장치의 데이터 구동부에 구현되는 가변저항들(PM81, PM82 … PM8n)의 구성, 작용 및 효과는 도 2에 도시된 PM 유기 ＥＬ 표시장치의 데이터 구동부에 구현되는 가변저항들(PM31, PM32 … PM3n)과 동일하다.As a result, the configuration, operation, and effect of the variable resistors PM81, PM82 ... PM8n implemented in the data driver of the AM organic EL display shown in FIG. 7 are implemented in the data driver of the PM organic EL display shown in FIG. The same as the variable resistors PM31, PM32 ... PM3n.
도 8은 종래의 유기 EL 표시장치와 본 발명의 일실시예에 따른 유기 EL 표시장치의 데이터 구동부에서의 전류변화율을 나타낸 것이다.8 shows a current change rate in a conventional organic EL display device and a data driver of an organic EL display device according to an embodiment of the present invention.
도시된 그래프의 실험조건은 50uA의 전류가 흐를 경우 저항 뒷단의 각 노드에서의 전압강하가 대략 1V 내외로 보상했을 경우 보상 후 전류변화율(그래프의 실선)이 종래의 보상 전 전류변화율(그래프의 점선)이 대략 50% 이상 감소되게 된다.The experimental condition of the graph shown is that if 50uA current flows, the voltage change at each node behind the resistor is compensated to be about 1V. After compensation, the current change rate (solid line of the graph) is the conventional current change rate before compensation (dotted line of the graph). ) Will be reduced by approximately 50% or more.
본 발명의 유기 EL 표시장치의 구동회로에 따르면, 유기 EL 표시장치의 채널간의 전류 편차를 줄여 휘도의 불균일, 명암선을 발생시키지 않는 유기 EL 표시장 치를 제공하는 것이 가능하게 된다.According to the driving circuit of the organic EL display device of the present invention, it becomes possible to provide an organic EL display device which does not generate unevenness in brightness and dark and dark lines by reducing current variation between channels of the organic EL display device.
또한, 유기 EL 표시장치의 프리차지 기간 동안에 피드백 저항에 의한 전압강하가 상대적으로 너무 커지는 것을 방지하기 위한 구동회로를 제공하는 것이 가능하게 된다.In addition, it becomes possible to provide a driving circuit for preventing the voltage drop caused by the feedback resistor from becoming too large during the precharge period of the organic EL display device.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100923347B1 (en) * | 2007-02-12 | 2009-10-22 | 엘지디스플레이 주식회사 | Organic Light Emitting Display Apparatus |
| US10475386B2 (en) | 2017-06-30 | 2019-11-12 | Lg Display Co., Ltd. | Display panel and electroluminescence display using the same |
| KR20200122502A (en) * | 2019-04-18 | 2020-10-28 | (주)팔콘시스템 | A Circuit For Eliminating Residual Current of Driving Transistor Using JFET |
| CN115985252A (en) * | 2022-11-30 | 2023-04-18 | 惠科股份有限公司 | Organic light emitting diode display panel, driving method thereof and display device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4092857B2 (en) * | 1999-06-17 | 2008-05-28 | ソニー株式会社 | Image display device |
| KR100446694B1 (en) * | 2001-07-16 | 2004-09-01 | 주식회사 자스텍 | Current Driving Apparatus for Electroluminescent Display Device using Current-Mirror |
| JP4595300B2 (en) | 2003-08-21 | 2010-12-08 | セイコーエプソン株式会社 | Electro-optical device and electronic apparatus |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100923347B1 (en) * | 2007-02-12 | 2009-10-22 | 엘지디스플레이 주식회사 | Organic Light Emitting Display Apparatus |
| US10475386B2 (en) | 2017-06-30 | 2019-11-12 | Lg Display Co., Ltd. | Display panel and electroluminescence display using the same |
| KR20200122502A (en) * | 2019-04-18 | 2020-10-28 | (주)팔콘시스템 | A Circuit For Eliminating Residual Current of Driving Transistor Using JFET |
| CN115985252A (en) * | 2022-11-30 | 2023-04-18 | 惠科股份有限公司 | Organic light emitting diode display panel, driving method thereof and display device |
| CN115985252B (en) * | 2022-11-30 | 2024-03-26 | 惠科股份有限公司 | Organic light emitting diode display panel, driving method thereof and display device |
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