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Organic Light-Emitting Diode (Oled) Display Panel, Oled Display Device and Method for Driving the Same

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Organic Light-Emitting Diode (Oled) Display Panel, Oled Display Device and Method for Driving the Same (19) TZZ¥__T (11) EP 3 147 894 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 29.03.2017 Bulletin 2017/13 G09G 3/3225 (2016.01) G09G 3/3233 (2016.01) (21) Application number: 16190336.4 (22) Date of filing: 23.09.2016 (84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • NA, Se-Hwan GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO 10895 Gyeonggi-do (KR) PL PT RO RS SE SI SK SM TR • LEE, Jae-Young Designated Extension States: 07350 Seoul (KR) BA ME • KIM, Mi-Jung Designated Validation States: 06923 Seoul (KR) MA MD (74) Representative: Viering, Jentschura & Partner (30) Priority: 25.09.2015 KR 20150136459 mbB Patent- und Rechtsanwälte (71) Applicant: LG Display Co., Ltd. Am Brauhaus 8 Yeongdeungpo-gu 01099 Dresden (DE) Seoul 07336 (KR) (54) ORGANIC LIGHT-EMITTING DIODE (OLED) DISPLAY PANEL, OLED DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME (57) Disclosed herein are an OLED display panel (410) further including a switching transistor (T-SW) for controlling application of supply voltage (VDD_EL) in the initializing interval of a pixel (P), an OLED display device including the same, and a method for driving the same. The OLED display panel (410) avoids a short-circuit be- tween supply voltage VDD_EL and reference voltage Vref to thereby reduce initialization voltage applied to the gate terminal of the driving transistor T_dr. The OLED display device can achieve various effects such as im- proved response characteristics of pixels by reducing de- viation in the initial voltage used in sampling. EP 3 147 894 A1 Printed by Jouve, 75001 PARIS (FR) 1 EP 3 147 894 A1 2 Description the switching transistor T_sw is connected to a scan line, and the drain electrode of the switching transistor T_sw CROSS REFERENCE TO RELATED APPLICA- is connected to a terminal of the storage capacitor C. The TION(S) switching transistor T_sw is turned on when a scan signal 5 Scan is applied via the scan line to allow data voltage to [0001] This application claims priority from Republic of be applied to the storage capacitor C. Korea Patent Application No. 10-2015-0136459 filed on [0011] The source electrode of the first transistor T1 is September 25, 2015. connected to a reference voltage line Vref and the gate electrodeof the first transistorT1 is connectedto an emis- BACKGROUND 10 sion control line, and the drain electrode of the first tran- sistor T1 is connected to the terminal of the storage ca- 1. Technical Field pacitor C. The first transistor T1 is turned on when an emission control signal EM is applied via the emission [0002] The present disclosure relates to an organic control line to allow reference voltage Vref to be applied light-emitting diode (OLED) display panel, an OLED dis- 15 to the terminal of the storage capacitor C. play device including the same, and a method for driving [0012] The source electrode of the second transistor the same. More specifically, the present disclosure re- T2 is connected to the other terminal of the storage ca- lates to an OLED display panel further including a switch- pacitor C, the gate electrode of the second transistor T2 ing transistor for controlling application of supply voltage is connected to the scan line, and the drain electrode of in the initializing interval of a pixel, an OLED display de- 20 the second transistor T2 is connected to the drain elec- vice including the same, and a method for driving the trode of the driving transistor T_dr. same. [0013] The source electrode of the third transistor T3 isconnected to the drainelectrode ofthe driving transistor 2. Description of the Related Art T_dr, the gate electrode of the third transistor T3 is con- 25 nected to the emission control line, and the drain elec- [0003] As the information-oriented society evolves, trode of the third transistor T3 is connected to the anode various demands for display devices are ever increasing. electrode of the OLED. Recently, a variety of flat display devices such as liquid- [0014] The source electrode of the fourth transistor T4 crystal display (LCD) devices, plasma display panel is connected to the anode electrode of the OLED, the (PDP) devices, and organic light-emitting diode (OLED) 30 gate electrode of the fourth transistor T4 is connected to display devices have been utilized. the scan line, and the drain electrode of the fourth tran- [0004] Among these, an OLED display device is ad- sistor T4 is connected to the reference voltage Vref line. vantageous over other flat display devices in that it can [0015] The source electrode of the driving transistor be driven with low voltage, can be made thinner, has T_dr is connected to the supply voltage VDD_EL termi- good viewing angle and fast response speed, and so on. 35 nal, the gate electrode of the driving transistor T_dr is Accordingly, OLED display devices find more and more connected to the other terminal of the storage capacitor applications. C, and the drain electrode of the driving transistor T_dr [0005] FIG. 1 is a circuit diagram of a pixel of an OLED is connected to the drain electrode of the second tran- display device in the related art, FIG. 2 is a timing chart sistor T2. While the driving transistor T_dr is turned on, for driving the pixel, and FIG. 3 is a graph showing re- 40 current flows to the OLED so that the OLED emits light. sponse time (R/T) characteristics according to different [0016] The intensity of the light emitted from the OLED initializing time intervals. is proportional to the amount of the current flowing in the [0006] FIG. 1 is an equivalent circuit diagram of a pixel OLED, and the amount of the current flowing in the OLED of an OLED display device in the related art, which has is proportional to the magnitude of the data voltage DATA the typical 6T1C (six transistors and one capacitor) struc- 45 applied to the gate electrode of the driving transistor T_dr. ture. [0017] In this manner, the OLED display device can [0007] Referring to FIG. 1, the pixel of the typical OLED display a variety of images by applying data voltages display device includes six transistors, one capacitor, an having different magnitudes to the pixel areas to display OLED, etc. different gradations. [0008] That is, in the pixel area, first to fourth transistors 50 [0018] The storage capacitor C holds data voltage DA- T1 to T4, a switching transistor T_sw, a driving transistor TA for a frame to regulate the amount of the current flow- T_dr, a storage capacitor C, and an OLED may be ing in the OLED and maintains the gradation displayed formed. by the OLED. [0009] The first to fourth transistors T1 to T4, the [0019] FIG. 2 is a timing chart for driving the OLED switching transistor T_sw and the driving transistor T_dr 55 display device of FIG. 1. may be p-type transistors. [0020] Referring to FIG. 2, it can be seen that the emis- [0010] The source electrode of the switching transistor sion control signal EM is deactivated immediately after T_sw is connected to a data line, the gate electrode of the scan signal Scan is applied. In doing so, data ad- 2 3 EP 3 147 894 A1 4 dressing and Vth (threshold voltage) compensation are vide an OLED display panel further including a switching carried out. In particular, the time period in which both of transistor for controlling application of supply voltage the emission control signal EM and the scan signal Scan VDD_EL in the initializing time interval of a pixel, an are in on-state is the initializing time interval I of the pixel. OLED display device including the same, and a method It is noted that since the transistors are P type transistors, 5 for driving the same. the emission control signal EM and scan signal Scan are [0029] It is another aspect of the present disclosure to active and in the on-state when they are logic low, and provide an OLED display panel with improved response they are deactivated and in the off-state when they are characteristics of pixels by way of avoiding a short-circuit logic high. between supply voltage VDD_EL and reference voltage [0021] For the pixel having the 6T1C structure de-10 Vref to thereby reduce initialization voltage applied to the scribed above with reference to FIG. 1, all of the transis- gate terminal of the driving transistor T_dr. tors are turned on during the initializing time interval I in [0030] It is yet another aspect of the present disclosure which both of the emission control signal EM and the to provide an OLED display panel with improved re- scan signal Scan are in on-state. sponse characteristics by increasing the initialization [0022] In other words, the gate electrodes of all of the 15 time interval of pixels, an OLED display device including transistors T_sw, T_dr and T1 to T4 disposed in the pixel the same, and a method for driving the same. receive the emission control signal EM or the scan signal [0031] As described above, the OLED display device Scan directly or indirectly, and thus all of the transistors having the typical 6T1C pixel structure has the problem remain turned on during the time interval I in which the that response time delay occurs due to deviation in the scan signal is applied on the scan line, and the signal on 20 initial voltage used in sampling, especially when the the emission control line EM is in an on-state.
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