KR20070028859A - Electroluminescence device and method for driving thereof - Google Patents
Electroluminescence device and method for driving thereof Download PDFInfo
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- KR20070028859A KR20070028859A KR1020050083593A KR20050083593A KR20070028859A KR 20070028859 A KR20070028859 A KR 20070028859A KR 1020050083593 A KR1020050083593 A KR 1020050083593A KR 20050083593 A KR20050083593 A KR 20050083593A KR 20070028859 A KR20070028859 A KR 20070028859A
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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
- G09G3/3258—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 with pixel circuitry controlling the voltage across the light-emitting element
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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]
- G09G3/3266—Details of drivers for scan electrodes
Abstract
Description
도 1은 종래 액티브메트릭스형 유기전계발광소자의 구조도.1 is a structural diagram of a conventional active matrix organic light emitting device.
도 2는 박막트랜지스터의 문턱전압 및 전류의 경시 변화성을 나타내는 그래프.Figure 2 is a graph showing the variability of the threshold voltage and current of the thin film transistor over time.
도 3은 본 발명에 따른 전계발광소자의 구동부 회로도.3 is a circuit diagram of a driver of an electroluminescent device according to the present invention.
도 4는 도 3의 구동방법을 나타내는 도면.4 is a view showing a driving method of FIG.
도 5는 도 4에 따른 타이밍 차트를 나타내는 도면.5 shows a timing chart according to FIG. 4;
도 6은 본 발명에 따라 전계발광소자의 구동시간이 향상된 것을 나타낸 그래프.6 is a graph showing that the driving time of the electroluminescent device is improved according to the present invention.
<도면의 주요 부분에 관한 부호의 설명><Explanation of symbols on main parts of the drawings>
T2: 보상박막트랜지스터 T1: 스위칭박막트랜지스터T2: compensation thin film transistor T1: switching thin film transistor
T3: 구동박막트랜지스터 Cst: 저장커패시터T3: Driven Thin Film Transistor Cst: Storage Capacitor
OLED: 발광소자OLED: light emitting element
150: 제1 스캔라인 151: 제2 스캔라인 150: first scan line 151: second scan line
본 발명은 전계발광소자와 구동방법에 관한 것이다. The present invention relates to an electroluminescent device and a driving method.
종래의 액티브메트릭스형 유기전계발광소자(AMOLED; Active Matrix Organic Light Emitting Diodes )의 경우 박막트랜지스터(TFT; Thin Film Transistor ) 2개와 1개의 커패시터로 유기전계발광소자를 구동하는 구조(2T1C 구조라 함)를 갖는다.In the case of conventional Active Matrix Organic Light Emitting Diodes (AMOLED), a structure (called 2T1C structure) for driving an organic light emitting diode device using two thin film transistors (TFT) and one capacitor is referred to as an active matrix organic light emitting diode (AMOLED). Have
도 1과 도 2를 참조하여, 종래 액티브메트릭스형 유기전계발광소자에 대해서 설명하겠다.1 and 2, a conventional active matrix type organic light emitting display device will be described.
도 1은 종래 액티브메트릭스형 유기전계발광소자의 구조도이고, 도 2는 박막트랜지스터의 문턱전압 및 전류의 경시 변화성을 나타내는 그래프이다.1 is a structural diagram of a conventional active matrix type organic light emitting display device, and FIG. 2 is a graph showing variability of threshold voltage and current of a thin film transistor.
도 1은 전형적인 N-형 초박막트랜지스터를 이용한 액티브형유기발광소자로 2T1C 구조를 나타낸다.FIG. 1 shows a 2T1C structure as an active organic light emitting device using a typical N-type ultra-thin transistor.
제1 박막트랜지스터(B1)에는, 드레인단과 전원전압(Vdd) 사이에 유기전계발광소자(OLED)가 접속되고, 소스단이 접지전압(Vss)에 접속되며, 게이트단과 소스단에 저장커패시터(Cst)가 형성된다.An organic light emitting diode OLED is connected to the first thin film transistor B1 between the drain terminal and the power supply voltage Vdd, the source terminal is connected to the ground voltage Vss, and the storage capacitor Cst is connected to the gate terminal and the source terminal. ) Is formed.
제2 박막트랜지스터(B2)의 게이트단에는 게이트전압단(50)이 접속되고, 드레인단에 데이터전압단(60)이 접속되며, 소스단에 제1 박막트랜지스터(B1)의 게이트단과 저장커패시터(Cst)가 접속되는 구조를 갖는다.The
여기서, 게이트전압(50)에 의해 제2 박막트랜지스터(B2)의 게이트단에 전압이 인가되면, 제2 박막트랜지스터(B2)가 턴 온 되어, 제1 박막트랜지스터(B1)의 게 이트단에 데이터전압(60)이 인가되고, 이에 따라 저장커패시터(Cst)에 일정량의 전압이 저장된다.Here, when a voltage is applied to the gate terminal of the second thin film transistor B2 by the
이때, 제2 박막트랜지스터(B2)가 턴 오프 되더라도 저장커패시터(Cst)에 저장된 용량만큼의 시간 동안 유기전계발광소자(OLED)가 발광할 수 있게 된다.In this case, even if the second thin film transistor B2 is turned off, the organic light emitting diode OLED may emit light for the amount of time stored in the storage capacitor Cst.
즉, 데이타가 저장커패시터(Cst)에 저장되었다가 저장된 용량만큼의 시간 동안만큼 전류를 일정하게 구동할 수 있는 방식이다.That is, the data is stored in the storage capacitor Cst, and the current can be driven constantly for the amount of time stored therein.
그러나 여기서, 제1 박막트랜지스터(B1)는 거의 턴 온 되어 있는 상태이기 때문에 제1 박막트랜지스터(B1)가 지속적인 바이어스 스트레스 하에 놓여 있게 되고 이로 인해 문턱전압(Vth) 특성이 변하게 된다.However, since the first thin film transistor B1 is almost turned on, the first thin film transistor B1 is placed under continuous bias stress, thereby changing the threshold voltage Vth characteristic.
이 특성의 변화는 도 2를 참조하여, 유기전계발광소자의 휘도와 연관시켜서 수식 적으로 보면 다음과 같다.A change in this characteristic is as follows, referring to FIG. 2 and related to the luminance of the organic light emitting device.
Lmax : 최대 LuminanceL max : Maximum Luminance
Vth : 문턱전압 (Threshold Voltage)Vth: Threshold Voltage
Vgs : 게이트와 소스 간의 전압차 (Gate to Source Voltage Difference)Vgs: Gate to Source Voltage Difference
W : 채널 폭 (Channel Width)W: Channel Width
L : 채널 길이 (Channel Length)L: Channel Length
Cox : 채널 용량(Channel Capacitance)Cox: Channel Capacitance
a2 : OLED 발광영역 OLED Luminance Areaa 2 : OLED emission area OLED Luminance Area
전술한 "수학식 1"에서 Vgs는 제1 박막트랜지스터(B1)에 가해지는 외적 영향에 해당되고 문턱전압(Vth)이 증가하면 최대휘도(Lmax)가 감소한다는 것을 알 수 있다.In Equation 1, Vgs corresponds to an external influence applied to the first thin film transistor B1, and as the threshold voltage Vth increases, the maximum luminance Lmax decreases.
또한, 열화 전후, 제1 박막트랜지스터(B1)의 특정 Vgs에서 출력 커브 (Output Curve) 곡선과 유기전계발광소자(OLED)의 전류/전압 커브 (I-V Curve) 곡선의 변화에 의해서 IOLED의 동작점이 제1 지점(81)에서 제2 지점(82)으로 이동됨을 알 수 있게 된다.In addition, before and after deterioration, the operating point of the I OLED is changed due to a change in the output curve and the current / voltage curve of the organic light emitting diode OLED at specific Vgs of the first thin film transistor B1. It can be seen that the movement from the
여기서, 제1 박막트랜지스터(B1)의 동작점이 포화(Saturation) 구간에 있기 때문에 유기전계발광소자(OLED)의 구동전압 증가보다는 제1 박막트랜지스터(B1)의 문턱전압(Vth) 의 이동에 의한 전류감소에 의해 더욱 크게 영향받음을 알 수 있게 된다.Here, since the operating point of the first thin film transistor B1 is in the saturation period, the current due to the movement of the threshold voltage Vth of the first thin film transistor B1 rather than an increase in the driving voltage of the organic light emitting diode OLED. It can be seen that the reduction is more greatly affected.
또한, 종래에는 박막트랜지스터의 특성 불균일성 및 경시성 특성 변화에 기인하여 박막트랜지스터의 전류가 감소한다.In addition, conventionally, the current of the thin film transistor is reduced due to the variation in characteristics and the chronological characteristics of the thin film transistor.
이에 따라, 유기전계발광소자의 전류 감소로 인한 외부양자효율(External Quantum Efficiency) 감소 및 휘도 감소에 의해 액티브형유기발광소자 디스플레이 의 수명을 확보하기가 어렵고, 이에 따라 발생하는 제약 사항이 많게 되었다.As a result, it is difficult to secure the lifetime of the active organic light emitting diode display due to the reduction of the external quantum efficiency due to the decrease of the current of the organic light emitting diode and the decrease of the luminance, and thus, many restrictions arise.
한편, LTPS 박막트랜지스터(Low Temperature Poly Silicon TFT)의 경우는 레이저 결정화의 빔 경계부위 중첩에 의한 결정성 변화가 세로 선의 휘도 불균일 특성을 유발하는 등 많은 문제가 있었다.On the other hand, LTPS thin film transistors (Low Temperature Poly Silicon TFT) has a number of problems, such as the crystallinity change caused by the overlap of the beam boundary portion of the laser crystallization causes the luminance non-uniformity of the vertical line.
또한, 비정질(a-Si) 박막트랜지스터를 이용한 액티브메트릭스형 유기전계발광소자 디스플레이를 구현하기 위해서는 박막트랜지스터 소자의 특성 균일도는 양호하나, 안정성이 LTPS 박막트랜지스터 대비 대략 10000배나 떨어지기 때문에 수명에 특히 문제가 있었다.In addition, in order to implement an active matrix type organic light emitting display using an amorphous (a-Si) thin film transistor, the uniformity of the characteristics of the thin film transistor device is good, but the stability is about 10000 times lower than that of the LTPS thin film transistor. There was.
여기서, 비정질(a-Si) 박막트랜지스터가 열화 되는 원인은 약한 본딩 결점에 의한 결점에 의해 생기기도 한다.The deterioration of the amorphous (a-Si) thin film transistor may be caused by a defect caused by a weak bonding defect.
이로 인해 동일한 외적 영향이 가해진다 하더라도 비정질실리콘(a-Si)이나 질화실리콘(SiNx)의 경계접점 영역에 야기된 영향으로 문턱전압(Vth)이 이동하게 된다.As a result, even if the same external influence is applied, the threshold voltage Vth is shifted due to the influence caused in the boundary contact region of amorphous silicon (a-Si) or silicon nitride (SiNx).
이에 따라, 박막트랜지스터를 타고 흐르는 전류가 감소하는 기계적 결점생성으로 활성화 에너지가 낮아지는 문제점과 지속적인 바이어스 스트레스 하에 있는 구동에 의한 문제점이 있었음을 알게 된다.Accordingly, it is found that there is a problem that the activation energy is lowered due to the generation of mechanical defects in which the current flowing through the thin film transistor is reduced, and a problem due to driving under constant bias stress.
상술한 문제점을 해결하기 위한 본 발명의 목적은, 액티브메트릭스형 유기전계발광소자의 구동에 따라 초박막트랜지스터가 받는 바이어스 스트레스를 최소화하는 구동장치와 구동방법을 제공하여 초박막트랜지스터의 열화를 최소화하는데 그 목적이 있다.An object of the present invention for solving the above problems is to provide a driving device and a driving method for minimizing the bias stress applied to the ultra-thin transistor in accordance with the drive of the active matrix organic light emitting device to minimize degradation of the ultra-thin transistor. There is this.
또한, 본 발명의 목적은 초박막트랜지스터가 받는 바이어스 스트레스를 최소화하고, 유기전계발광소자에 흐르는 전류 유지율을 개선하여 디스플레이 장치의 휘도 감소 특성을 개선하는데 그 목적이 있다.In addition, an object of the present invention is to minimize the bias stress received by the ultra-thin film transistor, improve the current retention rate flowing through the organic light emitting device to improve the brightness reduction characteristics of the display device.
상술한 과제를 해결하기 위한 본 발명의 제1실시예에 따른 전계발광소자는, 전원전압과 접지전압 사이에 형성된 발광소자; 발광소자와 접지전압 사이에 형성된 구동박막트랜지스터; 데이터신호가 인가되는 데이터라인과 구동박막트랜지스터 사이에 형성되며, 게이트가 제1 스캔라인에 접속된 스위칭박막트랜지스터; 스위칭박막트랜지스터와 구동박막트랜지스터의 게이트 사이에 형성되며, 게이트가 제2 스캔라인에 접속된 보상박막트랜지스터; 및 구동박막트랜지스터의 게이트와 접지전압 사이에 형성되어 데이터신호를 저장하는 저장커패시터를 포함한다.An electroluminescent device according to a first embodiment of the present invention for solving the above problems is a light emitting device formed between a power supply voltage and a ground voltage; A driving thin film transistor formed between the light emitting element and the ground voltage; A switching thin film transistor formed between the data line to which the data signal is applied and the driving thin film transistor, and having a gate connected to the first scan line; A compensation thin film transistor formed between the switching thin film transistor and the gate of the driving thin film transistor, the gate of which is connected to the second scan line; And a storage capacitor formed between the gate and the ground voltage of the driving thin film transistor to store the data signal.
한편, 본 발명의 제2실시예에 따른 전계발광소자의 구동방법은, On the other hand, the driving method of the electroluminescent device according to the second embodiment of the present invention,
데이터라인의 데이터신호를 스위칭하여 공급하도록 제1 스캔라인에 신호를 인가하여 스위칭박막트랜지스터를 턴온 시키는 데이터공급준비단계; 제2 스캔라인에 신호를 인가하여 보상박막트랜지스터를 턴온 시켜 데이터신호를 구동박막트랜지스터의 게이트단에 공급하는 데이터공급단계; 데이터공급단계와 동시에 구동박막트랜지스터를 소정시간(T) 동안 구동할 수 있는 데이터전압이 저장커패시터에 저장되는 전압저장단계; 데이터공급단계에 의해 소정시간(T) 동안 구동박막트랜지스터가 턴온 되는 발광소자구동준비단계; 및 발광소자구동준비단계 이후, 전원전압을 공급 하여 구동박막트랜지스터가 턴온 되는 소정시간(T) 동안 상기 발광소자를 턴온 시키는 발광소자구동단계; 를 포함한다.A data supply preparation step of turning on the switching thin film transistor by applying a signal to the first scan line to switch and supply the data signal of the data line; A data supply step of applying a signal to the second scan line to turn on the compensation thin film transistor to supply a data signal to a gate terminal of the driving thin film transistor; A voltage storing step in which a data voltage capable of driving the driving thin film transistor for a predetermined time T is stored at the same time as the data supplying step; A light emitting element driving preparation step of turning on the driving thin film transistor for a predetermined time T by the data supply step; And a light emitting device driving step of turning on the light emitting device for a predetermined time T when the driving thin film transistor is turned on by supplying a power supply voltage after the light emitting device driving preparation step. It includes.
여기서, 본 발명을 적합하게 구성하기 위한 구성요소로, 구동박막트랜지스터, 스위칭박막트랜지스터 및 보상박막트랜지스터는, N-타입 모스트랜지스터인 것을 특징으로 한다.Here, as a component for properly configuring the present invention, the driving thin film transistor, the switching thin film transistor and the compensation thin film transistor are characterized in that the N-type morph transistor.
여기서, 본 발명의 발광소자는 유기전계발광소자인 것이고, 데이터신호는 데이터전류인 것이다.The light emitting device of the present invention is an organic light emitting device, and the data signal is a data current.
기타 실시 예들의 구체적인 사항들은 상세한 설명 및 도면들에 포함되어 있다.Specific details of other embodiments are included in the detailed description and drawings.
이하, 첨부된 도면을 참조하여 본 발명의 바람직한 실시 예를 상세히 설명하기로 한다.Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
<제1실시예>First Embodiment
도 3은 본 발명에 따른 액티브메트릭스형 전계발광소자의 구동부 회로도이다.3 is a circuit diagram of a driver of an active matrix type electroluminescent device according to the present invention.
도시된 바와 같이, 제1실시예에 따른 전계발광소자의 구동부는 다음과 같다.As shown, the driving unit of the electroluminescent device according to the first embodiment is as follows.
발광소자(OLED)는 전원전압(Vdd)과 접지전압(Vss) 사이에 형성된다.The light emitting device OLED is formed between the power supply voltage Vdd and the ground voltage Vss.
구동박막트랜지스터(T3)는 발광소자(OLED)와 접지전압(Vss) 사이에 형성된다.The driving thin film transistor T3 is formed between the light emitting element OLED and the ground voltage Vss.
스위칭박막트랜지스터(T1)는 데이터신호가 들어오는 데이터라인(ISIGNAL)과 접 속되며, 구동박막트랜지스터(T3) 와 발광소자(OLED)가 접속된 지점에 접속되고, 게이트가 제1 스캔라인(150)에 접속되어 형성된다.The switching thin film transistor T1 is connected to the data line I SIGNAL through which the data signal is input, and is connected to a point where the driving thin film transistor T3 and the light emitting element OLED are connected, and the gate is connected to the
보상박막트랜지스터(T2)는 발광소자(OLED), 스위칭박막트랜지스터(T1) 및 구동박막트랜지스터(T3)가 접속되는 지점에 접속되며, 게이트가 제2 스캔라인(151)에 접속되어 형성된다.The compensation thin film transistor T2 is connected to a point where the light emitting device OLED, the switching thin film transistor T1 and the driving thin film transistor T3 are connected, and a gate is connected to the
저장커패시터(Cst)는 보상박막트랜지스터(T2)와 구동박막트랜지스터(T3)가 접속되는 지점에 접속되며, 그 타단이 구동박막트랜지스터(T3)와 함께 접지전압(Vss)에 접속되어 형성된다.The storage capacitor Cst is connected to the point where the compensation thin film transistor T2 and the driving thin film transistor T3 are connected, and the other end thereof is connected to the ground voltage Vss together with the driving thin film transistor T3.
여기서, 발광소자(OLED)는 유기 전계발광소자이고, 구동박막트랜지스터(T3), 보상박막트랜지스터(T2) 및 스위칭박막트랜지스터(T1)는 N-타입 모스트랜지스터이다.Here, the light emitting device OLED is an organic electroluminescent device, and the driving thin film transistor T3, the compensation thin film transistor T2, and the switching thin film transistor T1 are N-type morph transistors.
전술한 본 발명의 구동장치는 3개의 박막트랜지스터와 1개의 커패시터를 이용하여 박막트랜지스터의 특성 불균일성 및 경시성 변화에 의해 박막트랜지스터를 통해 흐르는 전류의 감소를 해결하고자 한다.The driving device of the present invention described above uses three thin film transistors and one capacitor to solve the reduction of the current flowing through the thin film transistor due to the change in characteristics and nonuniformity of the thin film transistor.
이에 따라 전계발광소자는 전류감소로 인한 외부양자 효율 감소 및 휘도 감소를 방지함으로써 전계발광표시 장치의 수명을 확보하는 전류구동 방식이다.Accordingly, the electroluminescent device is a current driving method for securing the lifetime of the electroluminescent display device by preventing the reduction of the external quantum efficiency and the luminance due to the current decrease.
전술한 본 발명의 제1실시예는, 제1 스캔라인(150)에 게이트가 접속된 스위칭박막트랜지스터(T1)가 턴온되면, 데이터라인(ISIGNAL)의 데이터신호가 스위칭되어 보상박막트랜지스터(T2)와 구동박막트랜지스터(T3)가 접속된 지점으로 흐르게 된 다.According to the first embodiment of the present invention, when the switching thin film transistor T1 having a gate connected to the
이때, 제2 스캔라인(151)에 게이트가 접속된 보상박막트랜지스터(T2)를 턴온하여, 스위칭되어 들어온 데이터신호를 저장커패시터(Cst)에 저장시킨다.In this case, the compensation thin film transistor T2 having a gate connected to the
여기서, 저장커패시터(Cst)에 저장된 데이터신호는 전원전압(Vdd)이 인가되고 난 후에도 커패시터에 저장된 용량만큼 발광소자(OLED)를 구동할 수 있는 정도의 커패시터 용량을 갖는다.Here, the data signal stored in the storage capacitor Cst has a capacitor capacity that can drive the light emitting device OLED as much as the capacity stored in the capacitor even after the power supply voltage Vdd is applied.
한편, 제2 스캔라인(151)이 스캔됨에 따라, 스위칭박막트랜지스터(T1)와 보상박막트랜지스터(T2)를 통해 공급된 데이터 신호가 구동박막트랜지스터(T3)의 게이트에 인가되어 구동박막트랜지스터(T3)가 턴온 된다.Meanwhile, as the
이렇게 순차적으로 턴온 된 각각의 박막트랜지스터는 발광소자(OLED)를 구동하기 위한 준비단계라고 볼 수 있다.Each of the thin film transistors sequentially turned on may be regarded as a preparation step for driving the OLED.
이후, 스위칭박막트랜지스터(T1)가 턴오프 되는 시점에 전원전압(Vdd)이 발광소자(OLED)에 인가된다.Thereafter, the power supply voltage Vdd is applied to the light emitting device OLED at the time when the switching thin film transistor T1 is turned off.
인가된 전원전압(Vdd)의 전원은 발광소자(OLED)를 거쳐 구동박막트랜지스터(T3)를 통해 접지전압(Vss) 측으로 흐르게 되어 발광소자(OLED)가 발광하게 된다.The power of the applied power supply voltage Vdd flows to the ground voltage Vss side through the driving thin film transistor T3 through the light emitting device OLED, and the light emitting device OLED emits light.
여기서, 일반적으로 전원전압(Vdd)의 공급이 차단된 후에도 저장커패시터(Cst)에 저장된 데이터신호에 해당하는 전하량에 비례하는 만큼 발광소자(OLED)가 발광하게 된다.Here, the light emitting device OLED emits light in proportion to the amount of charge corresponding to the data signal stored in the storage capacitor Cst even after the supply of the power supply voltage Vdd is cut off.
한편, 종래와는 달리 스위칭박막트랜지스터(T1)에 보상박막트랜지스터(T2)를 두어 각기 다른 타이밍을 갖고 박막트랜지스터가 턴온이 되므로 박막트랜지스터가 턴온이 될 때 발생하는 스위칭잡음을 줄일 수도 있게 된다.On the other hand, unlike the prior art by placing the compensation thin film transistor (T2) in the switching thin film transistor (T1) has a different timing and the thin film transistor is turned on, it is possible to reduce the switching noise generated when the thin film transistor is turned on.
아울러, 저장커패시터(Cst)에 저장된 전하량에 의해 구동박막트랜지스터(T3)가 구동되어 발광소자(OLED)의 발광효율과 박막트랜지스터의 구동효율을 높일 수도 있게 된다.In addition, the driving thin film transistor T3 is driven by the amount of charge stored in the storage capacitor Cst, thereby increasing the luminous efficiency of the light emitting device OLED and the driving efficiency of the thin film transistor.
<제2실시예>Second Embodiment
도 4는 도 3의 구동방법을 나타내고, 도 5는 도 4에 따른 타이밍 차트를 나타내고, 도 6은 본 발명에 따라 전계발광소자의 구동시간이 향상된 것을 나타낸 그래프이다.4 shows the driving method of FIG. 3, FIG. 5 shows a timing chart according to FIG. 4, and FIG. 6 is a graph showing that the driving time of the electroluminescent device is improved according to the present invention.
여기서, 도 3에 도시된 전계발광소자의 구동부 회로도를 함께 참조하여 제2실시예에 따른 구동방법을 기술해 나가겠다.Here, the driving method according to the second embodiment will be described with reference to the circuit diagram of the driving unit of the electroluminescent element shown in FIG. 3.
먼저, 전계발광소자의 구동부는 다음과 같다.First, the driving unit of the electroluminescent element is as follows.
전원전압(Vdd)과 접지전압(Vss) 사이에 발광소자(OLED)가 형성되고, 발광소자(OLED)와 접지전압(Vss) 사이에 구동박막트랜지스터(T3)가 형성된다.The light emitting device OLED is formed between the power supply voltage Vdd and the ground voltage Vss, and the driving thin film transistor T3 is formed between the light emitting device OLED and the ground voltage Vss.
또한, 스위칭박막트랜지스터(T1)는 데이터신호가 인가되는 데이터라인(ISIGNAL)과 구동박막트랜지스터(T3) 사이에 형성되며, 게이트가 제1 스캔라인(150)에 접속된다.In addition, the switching thin film transistor T1 is formed between the data line I SIGNAL to which the data signal is applied and the driving thin film transistor T3, and a gate thereof is connected to the
보상박막트랜지스터(T2)는 스위칭박막트랜지스터(T1)와 구동박막트랜지스터(T3)의 게이트 사이에 형성되며, 게이트가 제2 스캔라인(151)에 접속된다.The compensation thin film transistor T2 is formed between the switching thin film transistor T1 and the gate of the driving thin film transistor T3, and the gate is connected to the
여기서, 저장커패시터(Cst)의 일단이 보상박막트랜지스터(T2)와 구동박막트 랜지스터(T3)의 게이트와 접속되고, 그 타단이 접지전압(Vss)에 접속되는 것을 포함하는 구조를 갖는다. Here, one end of the storage capacitor Cst is connected to the gates of the compensation thin film transistor T2 and the driving thin film transistor T3, and the other end thereof is connected to the ground voltage Vss.
이하, 도 4 내지 도 6을 참조하여 본 발명의 제2실시예에 따른 전계발광소자의 구동방법을 기술하겠다.Hereinafter, a method of driving an electroluminescent device according to a second embodiment of the present invention will be described with reference to FIGS. 4 to 6.
먼저, 데이터라인(ISIGNAL)의 데이터신호를 스위칭하여 공급하도록 제1 스캔라인(150)에 신호를 인가하면, 스위칭박막트랜지스터(T1)가 턴온 되어 데이터공급준비단계(S202)가 된다.First, when a signal is applied to the
이때, 스위칭박막트랜지스터(T1)가 턴온이 되므로, 데이터신호가 스위칭 되어 데이터신호가 공급될 준비가 된다.At this time, since the switching thin film transistor T1 is turned on, the data signal is switched and is ready to be supplied with the data signal.
여기서 스위칭박막트랜지스터(T1)가 턴온 되는 시간은 소정시간(T)으로 1 프레임 내에서 구동방법 또는 구동 시간에 따라 변동될 수 있는 것이다.In this case, the time at which the switching thin film transistor T1 is turned on may vary according to a driving method or a driving time within one frame at a predetermined time T.
이후, 제2 스캔라인(151)에 신호를 인가하면, 보상박막트랜지스터(T2)가 턴온 되어 스위칭박막트랜지스터(T1)를 통해 공급된 데이터신호가 보상박막트랜지스터(T2)를 통해 구동박막트랜지스터(T3)의 게이트 단에 공급되는 데이터공급단계(S203)가 된다.Subsequently, when a signal is applied to the
한편, 데이터공급단계(S203)와 동시에 저장커패시터(Cst)에 전하가 저장되는 전압저장단계(S204)가 된다.On the other hand, at the same time as the data supply step (S203) is a voltage storage step (S204) in which charge is stored in the storage capacitor (Cst).
여기서, 저장커패시터(Cst)에 저장되는 전하는 데이터전압으로 저장커패시터(Cst)에 저장된 데이터전압이 방전되면, 그 방전되는 데이터전압의 양에 따라 구동 박막트랜지스터(T3)가 소정시간(T) 동안 턴온 된다.Here, when the charge stored in the storage capacitor Cst is discharged as the data voltage and the data voltage stored in the storage capacitor Cst is discharged, the driving thin film transistor T3 is turned on for a predetermined time T according to the amount of the discharged data voltage. do.
이와 동시에, 차기 데이터공급단계(S203)가 이루어지기 전 동안, 구동박막트랜지스터(T3)가 턴온 되어 발광소자(OLED)를 켤 준비를 하는 발광소자구동준비단계(S205)가 된다.At the same time, before the next data supply step S203 is performed, the driving thin film transistor T3 is turned on to be a light emitting device driving preparation step S205 that prepares to turn on the light emitting device OLED.
발광소자구동준비단계(S205) 이후, 전원전압(Vdd)을 공급하면, 구동박막트랜지스터(T3)가 턴온 되어 있는 소정시간(T) 동안 발광소자(OLED)가 발광 되는 발광소자구동단계(S206)가 된다.After the light emitting device driving preparation step S205, when the power supply voltage Vdd is supplied, the light emitting device OLED light emitting device OLED emits light for a predetermined time T when the driving thin film transistor T3 is turned on (S206). Becomes
이때, 발광하는 발광소자(OLED)는 유기전계발광소자 이다.In this case, the light emitting diode OLED is an organic light emitting diode.
그러나 본 발명의 기술을 적용함에 있어서는 무기발광소자를 포함하며, 본 발명을 통해 달성할 수 있는 목적은 유기전계발광소자에 한정되지는 않는다.However, in applying the technology of the present invention includes an inorganic light emitting device, the object that can be achieved through the present invention is not limited to the organic light emitting device.
여기서, 발광소자(OLED)가 발광하는 소정시간(T)은 다음의 세 가지에 의해 결정될 수 있다.Here, the predetermined time T during which the light emitting device OLED emits light may be determined by the following three methods.
첫째, 구동박막트랜지스터(T3)가 턴온 되어 있는지 여부와 둘째, 저장커패시터(Cst)가 구동박막트랜지스터(T3)의 게이트에 적정 데이터전압을 인가하고 있는지 여부와 셋째, 전원전압(Vdd)이 인가되고 있는지 여부이다.First, whether the driving thin film transistor T3 is turned on. Second, whether the storage capacitor Cst is applying an appropriate data voltage to the gate of the driving thin film transistor T3. Third, the power supply voltage Vdd is applied. Whether or not.
여기서, 제2실시예에 따른 전계발광소자의 구동방법에 있어서 각각의 소정시간(T)은 도 4와 도 5를 참조하여 보면 다음과 같이 설명된다.Here, each predetermined time T in the method of driving the electroluminescent device according to the second embodiment will be described as follows with reference to FIGS. 4 and 5.
데이터공급준비단계(S202)에서 스위칭박막트랜지스터(T1)가 턴온 되는 구간으로는, 1 프레임이 시작되는 시점을 시초로 하여 데이터공급단계(S203)의 보상박막트랜지스터(T2)와 중첩이 되는 구간으로 설정될 수 있다.As the section in which the switching thin film transistor T1 is turned on in the data supply preparation step (S202), it is a section overlapping with the compensation thin film transistor (T2) in the data supply step (S203) at the beginning of one frame. Can be set.
여기서, 보상박막트랜지스터(T2)가 턴온 되는 구간은 1 프레임 내에서 스위칭박막트랜지스터(T1)가 턴온 되는 구간에 포함되거나 또는 중첩하여 설정할 수 있다.Here, the section in which the compensation thin film transistor T2 is turned on may be included in or overlapping with the section in which the switching thin film transistor T1 is turned on in one frame.
이와 동시에, 전압저장단계(S204)에서 보상박막트랜지스터(T2)가 턴온이 됨과 함께 저장커패시터(Cst)는 커패시터 용량에 비례하여 데이터전압이 저장된다.At the same time, in the voltage storing step S204, the compensation thin film transistor T2 is turned on and the storage capacitor Cst stores the data voltage in proportion to the capacitor capacity.
결국, 이것은, 데이터라인(ISIGNAL)으로부터 공급된 신호가 단절되더라도 구동박막트랜지스터(T3)를 소정시간(T) 동안 충분히 구동할 수 있는 정도이다.As a result, this is such that the driving thin film transistor T3 can be sufficiently driven for a predetermined time T even when the signal supplied from the data line I SIGNAL is cut off.
여기서, 소정시간(T)은 저장커패시터(Cst)의 용량과 비례하는 것이다.Here, the predetermined time T is proportional to the capacity of the storage capacitor Cst.
발광소자구동준비단계(S205)에서는 보상박막트랜지스터(T2)가 턴온 됨과 동시에 구동박막트랜지스터(T3)가 턴온이 되어 실질적으로 발광소자(OLED)를 구동할 준비가 된 상태가 된다.In the light emitting device driving preparation step (S205), the compensation thin film transistor T2 is turned on and the driving thin film transistor T3 is turned on to be substantially ready to drive the light emitting device OLED.
즉, 전술한 구간까지 인 발광소자구동준비단계(S205)는 도 5의 (200)에 해당하는 구간이 되고, 이에 해당하는 단계까지는 발광소자(OLED)가 데이터라인(ISIGNAL)으로부터 들어온 데이터에 의해 발광 되기 위한 준비단계가 되는 것이다.That is, the light emitting device driving preparation step (S205) up to the above-described section becomes the section corresponding to (200) of FIG. 5, and until the corresponding step, the light emitting device OLED is applied to data received from the data line I SIGNAL . It is to be a ready step to be emitted by.
이후, 발광소자구동단계(S206)에서 전원전압(Vdd)를 인가함에 따라 발광소자(OLED)가 발광을 하게 되는데, 도 5를 참조하여 보듯이 여기서 발광 되는 구간은(300)에 해당하게 된다.Subsequently, the light emitting device OLED emits light as the power supply voltage Vdd is applied in the light emitting device driving step S206. As shown in FIG. 5, the light emitting device OLED corresponds to 300.
앞서 전술하였듯이 데이터신호가 공급되지 않더라도 구동박막트랜지스터(T3)는 저장커패시터(Cst)에 저장된 데이터전압이 게이트에 인가되어 저장커패시터 (Cst)의 저장된 용량만큼인 소정시간(T) 동안 구동할 수 있게 된다.As described above, even when the data signal is not supplied, the driving thin film transistor T3 is applied with a data voltage stored in the storage capacitor Cst to the gate so that the driving thin film transistor T3 can be driven for a predetermined time T corresponding to the stored capacity of the storage capacitor Cst. do.
한편, 전술한 본 발명의 구동 방법은, 스위칭박막트랜지스터(T1)와 보상박막트랜지스터(T2)가 턴온이 되는 시점이 동시에 일어나지 않음으로, 스위칭에 의한 잡음(노이즈)이 발생하는 문제를 줄일 수 있게 된다.On the other hand, in the above-described driving method of the present invention, since the timing at which the switching thin film transistor T1 and the compensation thin film transistor T2 are turned on at the same time does not occur, it is possible to reduce the problem of noise (noise) due to switching. do.
게다가, 박막트랜지스터가 받는 바이어스 스트레스를 최소화하여 박막트랜지스터의 신뢰성을 향상시킬 수 있게 된다.In addition, it is possible to improve the reliability of the thin film transistor by minimizing the bias stress applied to the thin film transistor.
전술한 제1실시예와 제2실시예를 참조하고, 도 6에 도시된 바와 같이 유기전계발광 표시장치의 전류 유지율 차이는 다음과 같게 됨을 이해할 수 있겠다.Referring to the first and second embodiments described above, it can be understood that the difference in current retention of the organic light emitting display device is as follows.
도시된 도면은, 초기 전류 유지율의 경시성 변화 차이를 모식화 한 것으로서, 본 발명이 전류에 의한 구동이므로 박막트랜지스터를 항상 일정한 전류로 구동할 수 있도록 하고 있음을 나타낸다.The illustrated figure is a model of the difference in change of the initial current retention over time, and shows that the present invention is driven by a current so that the thin film transistor can be always driven with a constant current.
이에 따라, 전계발광 표시장치를 구동하는 구동시간이 종래에는 (401) 지점이었지만, 본 발명은 대략 (403)지점 정도로 향상됨을 전술한 기술의 내용을 보아 알 수 있게 된다.Accordingly, although the driving time for driving the electroluminescent display is conventionally (401) point, it can be seen from the foregoing description that the present invention is improved to approximately (403) point.
또한, 제2 스캔라인(151)과 보상박막트랜지스터(T2)에 의해 구동박막트랜지스터(T3)가 구동이 되므로, 전류 감소율이 개선되고 발광소자(OLED)에 흐르는 전류 유지율을 개선함으로써 휘도 감소 특성을 개선할 수 있게 된다.In addition, since the driving thin film transistor T3 is driven by the
아울러, 각 박막트랜지스터는 전류를 이용하여 안정하게 구동되며, 소자의 신뢰성 개선과 수명향상 효과가 있을 수 있게 된다.In addition, each thin film transistor is driven stably using a current, thereby improving the reliability and lifespan of the device.
이상 첨부된 도면을 참조하여 본 발명의 실시 예를 설명하였지만, 상술한 본 발명의 기술적 구성은 본 발명이 속하는 기술 분야의 당업자가 본 발명의 그 기술적 사상이나 필수적 특징을 변경하지 않고서 다른 구체적인 형태로 실시될 수 있다는 것을 이해할 수 있을 것이다. 그러므로 이상에서 기술한 실시 예들은 모든 면에서 예시적인 것이며 한정적인 것이 아닌 것으로서 이해되어야 하고, 본 발명의 범위는 상기 상세한 설명보다는 후술하는 특허청구범위에 의하여 나타내어지며, 특허청구범위의 의미 및 범위 그리고 그 등가 개념으로부터 도출되는 모든 변경 또는 변형된 형태가 본 발명의 범위에 포함되는 것으로 해석되어야 한다.Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the above-described technical configuration of the present invention may be embodied in other specific forms by those skilled in the art to which the present invention pertains without changing its technical spirit or essential features. It will be appreciated that it may be practiced. Therefore, the exemplary embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.
상술한 본 발명의 구성에 따르면, 액티브메트릭스형 유기전계발광소자의 구동에 따라 초박막트랜지스터가 받는 바이어스 스트레스를 최소화하는 구동장치와 구동방법을 제공하여 초박막트랜지스터의 열화를 최소화하는 효과가 있다.According to the configuration of the present invention described above, by providing a driving device and a driving method for minimizing the bias stress applied to the ultra-thin transistor in accordance with the drive of the active matrix organic light emitting device has the effect of minimizing the degradation of the ultra-thin transistors.
또한, 초박막트랜지스터의 열화를 최소화하여 디스플레이 장치의 수명을 향상시키고, 휘도 감소 특성을 개선하는 효과가 있다.In addition, there is an effect of minimizing deterioration of the ultra-thin transistor to improve the life of the display device, and to improve the brightness reduction characteristics.
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| US10714503B2 (en) | 2009-07-03 | 2020-07-14 | Semiconductor Energy Laboratory Co., Ltd. | Display device including transistor and manufacturing method thereof |
| US11257847B2 (en) | 2009-07-03 | 2022-02-22 | Semiconductor Energy Laboratory Co., Ltd. | Display device including transistor and manufacturing method thereof |
| US11637130B2 (en) | 2009-07-03 | 2023-04-25 | Semiconductor Energy Laboratory Co., Ltd. | Display device including transistor and manufacturing method thereof |
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