Display devices

Abstract

The present disclosure relates to a display device. The display device includes: a first pixel including a first organic light-emitting diode; an initialization voltage generator for generating a first initialization voltage to be supplied to an anode of the first organic light-emitting diode; and a timing controller including a first lookup table recording a plurality of first initialization voltage values ​​corresponding to a plurality of maximum brightnesses, the timing controller being configured to determine a value of the first initialization voltage based on received information related to a target maximum brightness and the first lookup table.

Description

[0001] This application is a divisional application of the invention with the application date of October 11, 2018, application number 201811182498.2 and name “Display device and driving method thereof”.

[0002] Cross-reference to related applications

[0003] This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0144924, filed on November 1, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Technical Field

[0004] Aspects of some example embodiments of the present disclosure relate to a display device and a driving method thereof. Background Art

[0005] With the development of information technology, the importance of display devices as a connection medium between users and information has increased. Therefore, display devices such as liquid crystal display devices, organic light emitting display devices, and plasma display panels are increasingly used.

[0006] Among these display devices, organic light emitting display devices display images using organic light emitting diodes that generate light through recombination of electrons and holes. Organic light emitting display devices have a relatively high response speed and are driven with relatively low power consumption.

[0007] The organic light emitting display device displays a target image to a user by writing a data voltage representing a target grayscale in each pixel and allowing a plurality of organic light emitting diodes to emit light corresponding to the data voltage.

[0008] Typically, the plurality of organic light emitting diodes are configured to include a red organic light emitting diode, a blue organic light emitting diode, and a green organic light emitting diode. Since the organic materials of the organic light emitting diodes have different band gaps, the plurality of organic light emitting diodes emit light having different wavelengths.

[0009] The amount of driving current supplied to organic light emitting diodes of multiple colors can be set differently according to the emission efficiency of such organic materials. For example, a relatively small driving current can be supplied to an organic light emitting diode of a color having an organic material with high emission efficiency.

[0010] However, under low brightness conditions where the magnitude of the driving current is very small, a relatively long period of time may be required to charge the capacitor of the corresponding organic light emitting diode, and therefore, a color drag phenomenon may occur in which the corresponding organic light emitting diode emits light later than organic light emitting diodes of other colors.

[0011] The above information disclosed in this Background section is only for enhancement of understanding of the background technology and therefore it may contain information that does not constitute prior art. Summary of the Invention

[0012] Some example embodiments include a display device capable of eliminating or alleviating a color drag phenomenon by controlling an initialization voltage according to a brightness condition, and a driving method of the display device.

[0013] According to some example embodiments of the present disclosure, a display device includes: a first pixel including a first organic light-emitting diode; an initialization voltage generator configured to generate a first initialization voltage to be supplied to an anode of the first organic light-emitting diode; and a timing controller including a first lookup table, in which a plurality of first initialization voltage values ​​corresponding to a plurality of maximum brightnesses are recorded, and the timing controller is configured to determine the value of the first initialization voltage based on received information related to a target maximum brightness and the first lookup table.

[0014] The plurality of first initialization voltage values ​​may be obtained by adding a first offset value to a value of a first power voltage to be supplied to the cathode of the first organic light emitting diode.

[0015] Each of the first offset values ​​may be inversely proportional to a magnitude of a corresponding maximum brightness.

[0016] The plurality of maximum brightnesses may include a reference maximum brightness. The first offset value at the reference maximum brightness may be 0.

[0017] The first offset value corresponding to a first maximum brightness group exceeding the reference maximum brightness among the plurality of maximum brightnesses may be less than 0.

[0018] The first offset value corresponding to a second maximum brightness group smaller than the reference maximum brightness among the plurality of maximum brightnesses may be greater than 0.

[0019] The first power voltage may be inversely proportional to the magnitude of the target maximum brightness.

[0020] The first power voltage may have a specific voltage value when the target maximum brightness corresponds to the reference maximum brightness, and have a voltage value lower than the specific voltage value when the target maximum brightness corresponds to the first maximum brightness group.

[0021] The first power voltage may have a voltage value equal to or greater than a specific voltage value when the target maximum brightness corresponds to the second maximum brightness group.

[0022] The second power voltage supplied to the anode electrode of the first organic light emitting diode may have a fixed value regardless of the target maximum brightness.

[0023] The display device may further include a second pixel including a second organic light-emitting diode (OLED) having an organic material having a bandgap different from that of the organic material of the first OLED. The timing controller may further include a second lookup table having a plurality of second initialization voltage values ​​corresponding to a plurality of maximum brightness levels recorded therein, and the timing controller may be configured to determine the value of the second initialization voltage based on received information related to the target maximum brightness and the second lookup table. The initialization voltage generator may be configured to generate the second initialization voltage to be supplied to the anode of the second OLED.

[0024] Multiple first initialization voltage values ​​can be obtained by adding a first offset value to the value of the first power voltage to be supplied to the cathode of the first organic light emitting diode, and multiple second initialization voltage values ​​can be obtained by adding a second offset value to the value of the first power voltage to be supplied to the cathode of the second organic light emitting diode.

[0025] The plurality of maximum brightnesses may include a reference maximum brightness. The first offset value and the second offset value at the reference maximum brightness may be zero.

[0026] A first offset value corresponding to a first maximum brightness group exceeding a reference maximum brightness among the plurality of maximum brightnesses may be less than 0, and a second offset value corresponding to the first maximum brightness group may be less than the first offset value.

[0027] A first offset value corresponding to a second maximum brightness group smaller than the reference maximum brightness among the plurality of maximum brightnesses may be greater than 0, and a second offset value corresponding to the second maximum brightness group may be smaller than the first offset value.

[0028] The first power voltage may have a specific voltage value when the target maximum brightness corresponds to the reference maximum brightness, and the first power voltage may have a voltage value lower than the specific voltage value when the target maximum brightness corresponds to the first maximum brightness group.

[0029] The first power voltage may have a voltage value equal to or greater than a specific voltage value when the target maximum brightness corresponds to the second maximum brightness group.

[0030] The second power voltage supplied to the anode of the first organic light emitting diode and the anode of the second organic light emitting diode may have a fixed value regardless of the target maximum brightness.

[0031] According to aspects of the present disclosure, a method for driving a display device is provided, the method including: receiving, by a timing controller, information related to a target maximum brightness; determining, by the timing controller, a value of a first initialization voltage corresponding to the target maximum brightness using a first lookup table constructed in the timing controller; initializing, by an initialization voltage generator, an amount of charge accumulated in a first organic light emitting diode of a first pixel by supplying the first initialization voltage to an anode of the first organic light emitting diode; and allowing the first organic light emitting diode to emit light corresponding to a target grayscale having a brightness equal to or less than the target maximum brightness.

[0032] A plurality of first initialization voltage values ​​corresponding to a plurality of maximum luminances may be recorded in the first lookup table.The plurality of first initialization voltage values ​​may be obtained by adding a first offset value to a value of a first power voltage to be supplied to a cathode of the first organic light emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Aspects of some example embodiments will be described more fully hereinafter with reference to the accompanying drawings; however, these embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art.

[0034] In the accompanying drawings, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being "between two elements," that element can be the only element between the two elements, or one or more intermediate elements may also be present. Throughout the text, the same reference numerals refer to the same elements.

[0035] Figure 1 are diagrams illustrating display devices according to some example embodiments of the present invention.

[0036] Figure 2 is a diagram illustrating a first pixel according to some example embodiments of the present invention.

[0037] Figure 3 is a graph illustrating a first initialization voltage when a target maximum brightness is equal to a reference maximum brightness according to some example embodiments of the present invention.

[0038] Figure 4 is a graph illustrating a first initialization voltage when a target maximum brightness is greater than a reference maximum brightness according to some example embodiments of the present invention.

[0039] Figure 5 is a graph illustrating a first initialization voltage when a target maximum brightness is less than a reference maximum brightness according to some example embodiments of the present invention.

[0040] Figure 6 is a diagram illustrating examples of a first initialization voltage, a first power voltage, and a second power voltage according to a target maximum brightness according to some example embodiments of the present invention.

[0041] Figure 7 are diagrams illustrating display devices according to some example embodiments of the present invention.

[0042] Figure 8 is a diagram illustrating embodiments of a pixel unit according to some example embodiments of the present invention.

[0043] Figure 9 is a diagram illustrating another embodiment of a pixel unit according to some example embodiments of the present invention.

[0044] Figure 10 is a diagram illustrating the color dragging phenomenon.

[0045] Figure 11 is a diagram illustrating a first pixel and a second pixel according to some example embodiments of the present invention.

[0046] Figure 12 is a graph illustrating a first initialization voltage and a second initialization voltage when a target maximum brightness is equal to a reference maximum brightness according to some example embodiments of the present invention.

[0047] Figure 13 is a graph illustrating a first initialization voltage and a second initialization voltage when a target maximum brightness is greater than a reference maximum brightness according to some example embodiments of the present invention.

[0048] Figure 14 is a graph illustrating a first initialization voltage and a second initialization voltage when a target maximum brightness is less than a reference maximum brightness according to some example embodiments of the present invention. DETAILED DESCRIPTION

[0049] Hereinafter, aspects of some example embodiments are described in more detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present disclosure. The present disclosure can be implemented in various forms and is not limited to the example embodiments described in this specification.

[0050] In order to clearly describe the present disclosure, some irrelevant or repeated descriptions may be omitted, and the same reference numerals are used to designate the same or similar components throughout the specification. Therefore, the same reference numerals may be used in different drawings to identify the same or similar elements.

[0051] In addition, for better understanding and convenience of description, the size and thickness of each component illustrated in the drawings are arbitrarily shown, but the present disclosure is not limited thereto. For clarity of expression, the thickness of several parts and regions is exaggerated.

[0052] Figure 1 are diagrams illustrating display devices according to some example embodiments of the present invention.

[0053] refer to Figure 1 , a display device according to some example embodiments of the present invention includes a processor 9, a driver IC 10, a scan driver 20, an emission control driver 30, a pixel unit 40, and a DC-DC converter 50. The driver IC 10 may include a timing controller 11, an initialization voltage generator 12, and a data driver 13.

[0054] The processor 9 may be a general-purpose processing device. For example, the processor 9 may be an application processor (AP) of a mobile phone. As another example, the processor 9 may be a host system.

[0055] The processor 9 may supply control signals and image signals required for displaying an image to the driver IC 10. For example, the control signals may include a data enable signal, a vertical synchronization signal, a horizontal synchronization signal, a target maximum brightness, and the like.

[0056] The target maximum brightness may be the brightness at the maximum grayscale to be displayed in the current display device. When the grayscale of one pixel in the image signal for one frame is defined as unit image data, the unit image data may have, for example, 8 bits. When the unit image data has 8 bits, 256 grayscales may be expressed. The minimum grayscale (grayscale 0) may be the darkest, and the maximum grayscale (grayscale 255) may be the brightest. At this time, when all pixels of the pixel unit 40 emit light having the maximum grayscale, the brightness may be defined as the target maximum brightness.

[0057] According to some example embodiments of the present invention, the unit of the target maximum brightness is specified as nits. That is, the pixel unit 40 can display a partially (spatially) dark and bright image according to the image signal, or display a dark and bright image according to the frame (time). However, the maximum brightness of the image is limited by the target maximum brightness.

[0058] The target maximum brightness may be set manually when a user manipulates the display device, or automatically using an algorithm linked to an illuminance sensor, for example.

[0059] The timing controller 11 converts the control signals and image signals supplied from the processor 9 to suit the specifications of the drive IC 10 , and supplies the required control signals and image signals to the scan driver 20 , the emission control driver 30 , and the data driver 13 .

[0060] In this embodiment, the timing controller 11 includes a first lookup table LUT1 in which a plurality of first initialization voltages corresponding to a plurality of maximum brightnesses are recorded. The timing controller 11 can determine the value of the first initialization voltage based on received information related to the target maximum brightness and the first lookup table LUT1. In some embodiments, the first lookup table LUT1 can exist outside the timing controller 11.

[0061] The initialization voltage generator 12 can generate at least one initialization voltage. For example, the first initialization voltage can be supplied to the anode of the organic light-emitting diode included in the pixel to initialize the amount of charge accumulated in the organic light-emitting diode. In addition, for example, the third initialization voltage can be supplied to the gate terminal of the driving transistor included in the pixel to initialize the amount of charge accumulated in the gate electrode of the driving transistor. In this embodiment, the third initialization voltage is not separately defined, but can have a fixed value. For example, when the first offset value is 0, the third initialization voltage can have a value equal to the value of the first initialization voltage.

[0062] In this embodiment, the initialization voltage generator 12 may generate a first initialization voltage having a predetermined value and supply the generated first initialization voltage to the anode of the first organic light emitting diode of the first pixel. Figure 2 Further details of the first pixel, the first organic light emitting diode, and the first initialization voltage are described in more detail.

[0063] The data driver 13 generates data voltages to be supplied to the plurality of data lines D1, D2, ..., and Dm by receiving a control signal and an image signal from the timing controller 11. The data voltages generated in pixel row units may be simultaneously supplied to the plurality of data lines D1, D2, ..., and Dm according to an output control signal included in the control signal.

[0064] The scan driver 20 generates scan signals to be supplied to the plurality of scan lines S0, S1, S2, ..., and Sn by receiving control signals from the timing controller 11. In an embodiment, the scan driver 20 may sequentially supply the scan signals to the plurality of scan lines S0, S1, S2, ..., and Sn. For example, the control signal CONT1 may include a gate start pulse GSP and a plurality of gate clock signals, and the scan driver 20 may be configured in the form of a shift register to generate the scan signals in a manner such that the gate start pulse is sequentially transferred to the next stage circuit under the control of the gate clock signal.

[0065] The emission control driver 30 can supply emission control signals for determining the emission periods of the plurality of pixels PX11, PX12, ..., PX1m, PX21, PX22, ..., PX2m, ..., PXn1, PXn2, ..., and PXnm to the emission control lines E1, E2, ..., and En. For example, each pixel may include an emission control transistor, and the flow of current through the organic light emitting diode may be determined based on the on / off switching of the emission control transistor to control the emission of the organic light emitting diode. In some embodiments, the emission control driver 30 may be configured as a sequential emission type emission control driver that allows light to be emitted sequentially from each pixel row. In another embodiment, the emission control driver 30 may be configured as a simultaneous emission type emission control driver that allows light to be emitted from all pixel rows simultaneously.

[0066] The DC-DC converter 50 can generate multiple power voltages using a power supply. For example, the DC-DC converter 50 can generate a first power voltage and a second power voltage to be used in each pixel. In this embodiment, the first power voltage is less than the second power voltage. Figure 1 In the first embodiment, the initialization voltage generator 12 is illustrated as being spaced apart from the DC-DC converter 50. However, in another embodiment, the initialization voltage generator 12 may be built into the DC-DC converter 50. In yet another embodiment, at least a portion of the DC-DC converter 50 may be built into the driver IC 10.

[0067] The pixel unit 40 may include a plurality of pixels PX11, PX12, ..., PX1m, PX21, PX22, ..., PX2m, ..., PXn1, PXn2, ..., and PXnm. Each pixel may be coupled to a corresponding data line and a corresponding scan line and receive a data voltage input corresponding to a scan signal. Each pixel allows an organic light emitting diode to emit light corresponding to the input data voltage, and thus, the pixel unit 40 displays an image screen.

[0068] Figure 2 is a diagram illustrating a first pixel according to some example embodiments of the present invention.

[0069] Reference Figure 2 , the first pixel PXij includes a plurality of transistors M1 , M2 , M3 , M4 , M5 , M6 and M7 , a storage capacitor Cst1 and a first organic light emitting diode OLED1 .

[0070] Hereinafter, a circuit configured with a P-type transistor is described as an example. However, those skilled in the art can design a circuit configured with an N-type transistor by changing the polarity of the voltage applied to the gate terminal of the transistor. Similarly, those skilled in the art can design a circuit configured with a combination of a P-type transistor and an N-type transistor. A P-type transistor is generally referred to as a transistor in which the amount of current flowing through the transistor increases when the voltage difference between the gate terminal and the source terminal increases in a negative direction. An N-type transistor is generally referred to as a transistor in which the amount of current flowing through the transistor increases when the voltage difference between the gate terminal and the source terminal increases in a positive direction. The transistor can be configured in various forms, such as a thin film transistor (TFT), a field effect transistor (FET), and a bipolar junction transistor (BJT).

[0071] One electrode of the transistor M1 may be coupled to the other electrode of the transistor M5, the other electrode of the transistor M1 may be coupled to one electrode of the transistor M6, and the gate electrode of the transistor M1 may be coupled to the other electrode of the storage capacitor Cst1. The transistor M1 may be referred to as a first drive transistor. The amount of drive current flowing between the second power voltage ELVDD and the first power voltage ELVSS is determined by the potential difference between its gate electrode and source electrode.

[0072] One electrode of the transistor M2 may be coupled to the data line Dj, the other electrode of the transistor M2 may be coupled to the one electrode of the transistor M1, and the gate electrode of the transistor M2 may be coupled to the scan line Si of the current stage. The transistor M2 may be referred to as a first scan transistor. If a scan signal of an on level is applied to the scan line Si of the current stage, the transistor M2 allows the data voltage of the data line Dj to be applied to the first pixel PXij.

[0073] One electrode of the transistor M3 may be coupled to the other electrode of the transistor M1, the other electrode of the transistor M3 may be coupled to the gate electrode of the transistor M1, and the gate electrode of the transistor M3 may be coupled to the scan line Si of the current stage. If a scan signal of a conduction level is applied to the scan line Si of the current stage, the transistor M3 may allow the transistor M1 to be diode-coupled.

[0074] One electrode of the transistor M4 may be coupled to the gate electrode of the transistor M1, the other electrode of the transistor M4 may be coupled to the third initialization voltage VINT3, and the gate electrode of the transistor M4 may be coupled to the scan line S(i-1) of the previous stage. In another embodiment, the gate electrode of the transistor M4 may be coupled to another scan line. If a scan signal of an on-level is applied to the scan line S(i-1) of the previous stage, the transistor M4 allows the amount of charge accumulated in the gate electrode of the transistor M1 to be initialized by supplying the third initialization voltage VINT3 to the gate electrode of the transistor M1.

[0075] One electrode of transistor M5 may be coupled to the second power voltage ELVDD, the other electrode of transistor M5 may be coupled to the one electrode of transistor M1, and the gate electrode of transistor M5 may be coupled to emission control line Ei. One electrode of transistor M6 may be coupled to the other electrode of transistor M1, the other electrode of transistor M6 may be coupled to the anode of first organic light emitting diode OLED1, and the gate electrode of transistor M6 may be coupled to emission control line Ei. Transistors M5 and M6 may be referred to as emission control transistors. If an emission control signal of an on level is applied to emission control line Ei, transistors M5 and M6 form a current path between second power voltage ELVDD and first power voltage ELVSS, allowing first organic light emitting diode OLED1 to emit light.

[0076] One electrode of the transistor M7 may be coupled to the anode of the first organic light emitting diode OLED1, the other electrode of the transistor M7 may be coupled to the first initialization voltage VINT1, and the gate electrode of the transistor M7 may be coupled to the scan line Si of the current stage. In another embodiment, the gate electrode of the transistor M7 may be coupled to another scan line. If a scan signal of an on level is applied to the scan line Si of the current stage, the transistor M7 allows the amount of charge accumulated in the first organic light emitting diode OLED1 to be initialized by supplying the first initialization voltage VINT1 to the anode of the first organic light emitting diode OLED1.

[0077] An anode electrode of the first organic light emitting diode OLED1 may be coupled to the other electrode of the transistor M6, and a cathode electrode of the first organic light emitting diode OLED1 may be coupled to the first power voltage ELVSS. Figure 2 In FIG. 1 , the capacitance Co1 may be illustrated in order to describe the amount of charge accumulated in the first organic light emitting diode OLED1 .

[0078] Figure 3 is a graph illustrating a first initialization voltage when a target maximum brightness is equal to a reference maximum brightness in the first embodiment.

[0079] As described above, the first initialization voltage VINT1 is generated from the initialization voltage generator 12. In this embodiment, the first initialization voltage VINT1 can be changed according to the target maximum brightness L_tar. For example, the timing controller 11 can search for a first initialization voltage value corresponding to the target maximum brightness L_tar among a plurality of first initialization voltage values ​​corresponding to a plurality of maximum brightnesses in the first lookup table LUT1, and pass the searched first initialization voltage value to the initialization voltage generator 12. The initialization voltage generator 12 can generate the first initialization voltage VINT1 according to the passed first initialization voltage value.

[0080] In this embodiment, the plurality of first initialization voltage values ​​are obtained by adding a first offset value OFFSET1 to the value of the first power voltage ELVSS. Each of the first offset values ​​OFFSET1 may be approximately inversely proportional to the magnitude of the corresponding maximum brightness.

[0081] The plurality of maximum brightnesses in the first lookup table LUT1 may include a reference maximum brightness L_ref. The first offset value OFFSET1 at the reference maximum brightness L_ref may be 0. That is, when the target maximum brightness L_tar is equal to the reference maximum brightness L_ref, the value of the first power voltage ELVSS may be substantially equal to the value of the first initialization voltage VINT1.

[0082] exist Figure 3 In the description, the case where the target maximum brightness L_tar corresponds to the reference maximum brightness L_ref will be given as an example. Figure 2 Driving method of the first pixel PXij.

[0083] At time t1, the data voltage DATA(i-1)j of the pixel row of the previous stage is applied to the data line Dj, and the scan signal of the on level (low level) is applied to the scan line S(i-1) of the previous stage.

[0084] Since the scan signal of the off level (high level) is applied to the scan line Si of the current stage, the transistor M2 is in the off state, and the data voltage DATA(i-1)j of the pixel row of the previous stage is blocked from being applied to the first pixel PXij.

[0085] At this time, since the transistor M4 is in the on state, the third initialization voltage VINT3 is applied to the gate electrode of the transistor M1, so that the amount of charge accumulated in the gate electrode of the transistor M1 is initialized. Since the emission control signal of the off level is applied to the emission control line Ei, the transistors M5 and M6 are in the off state, and unnecessary emission of the first organic light emitting diode OLED1 caused by the process of applying the third initialization voltage VINT3 is prevented.

[0086] At time t2 , since the transistor M4 is turned off due to the application of the scan signal of the off level (high level) to the scan line S(i−1) of the previous stage, the supply of the third initialization voltage VINT3 is stopped.

[0087] At time t3, the data voltage DATAij of the pixel row of the current stage is applied, and the scan signal of the on level is applied to the scan line Si of the current stage. Therefore, the transistors M2, M1, and M3 are turned on, so that the data line Dj and the gate electrode of the transistor M1 are electrically coupled to each other. Therefore, the data voltage DATAij is applied to the other electrode of the storage capacitor Cst1, and the storage capacitor Cst1 accumulates a large amount of charge corresponding to the difference between the second power voltage ELVDD and the data voltage DATAij.

[0088] At this time, since the transistor M7 is in the on state, the first initialization voltage VINT1 is applied to the anode of the first organic light emitting diode OLED1, and the first organic light emitting diode OLED1 is pre-charged with a large amount of charge corresponding to the difference between the first initialization voltage VINT1 and the first power voltage ELVSS. In this embodiment, Figure 3 The case is a case where the target maximum brightness L_tar is equal to the reference maximum brightness L_ref and the first offset value OFFSET1 is 0. Therefore, since the first power voltage ELVSS is substantially equal to the first initialization voltage VINT1, there is no voltage difference between both ends of the first organic light emitting diode OLED1, and the amount of charge precharged in the first organic light emitting diode OLED1 becomes 0.

[0089] At time t4 , since the scan signal of the off level is applied to the scan line Si of the current stage, accumulation of charges in the storage capacitor Cst1 ends, the accumulated charges are held, and initialization of the first organic light emitting diode OLED1 ends.

[0090] At time t5, since an emission control signal of an on level is applied to the emission control line Ei, transistors M5 and M6 are turned on, and the amount of driving current flowing through transistor M1 is controlled according to the amount of charge accumulated in the storage capacitor Cst1, so that the driving current flows through the first organic light emitting diode OLED1. The driving current is charged into the capacitor Co1 of the first organic light emitting diode OLED1, and the fully charged first organic light emitting diode OLED1 emits light until an emission control signal of an off level is applied to the emission control line Ei.

[0091] The reference maximum brightness L_ref may be defined as the brightness when sufficient driving current flows to the extent that any color dragging phenomenon is not observed. The reference maximum brightness L_ref may be set individually for each product. Figure 3 In the embodiment of the present invention, even when the amount of charges pre-charged in the first organic light emitting diode OLED1 is 0, the color dragging phenomenon is not observed.

[0092] Figure 4 is a graph illustrating a first initialization voltage when a target maximum brightness is greater than a reference maximum brightness in the first embodiment.

[0093] exist Figure 4 In the driving method of the first pixel PXij, Figure 3 There is no difference in the driving method, and therefore, repeated description will be omitted.

[0094] The first lookup table LUT1 includes a first maximum brightness group exceeding a reference maximum brightness L_ref among the plurality of maximum brightnesses, and a first offset value OFFSET1 corresponding to the first maximum brightness group is less than 0. Figure 4 The case is a case where the target maximum brightness L_tar corresponds to any one of the first maximum brightness group, that is, a case where the target maximum brightness L_tar is greater than the reference maximum brightness L_ref.

[0095] Therefore, in Figure 4 In the case of , the first initialization voltage VINT1 is lower than the first power voltage ELVSS.

[0096] Figure 4 The case where the display device is set to emit light with high brightness. At this time, the amount of driving current supplied to the first organic light emitting diode OLED1 is greater than Figure 3 The amount of driving current in the case of , and therefore the color dragging phenomenon is not observed. Figure 4 In the case of , a reverse voltage is applied to the first organic light emitting diode OLED1 to be initialized, so that degradation of the first organic light emitting diode OLED1 can be delayed.

[0097] Figure 5 is a graph illustrating a first initialization voltage when a target maximum brightness is less than a reference maximum brightness in the first embodiment.

[0098] exist Figure 5 In the driving method of the first pixel PXij, Figure 3 There is no difference in the driving method, and therefore, repeated description will be omitted.

[0099] The first lookup table LUT1 includes a second maximum brightness group smaller than the reference maximum brightness L_ref among the plurality of maximum brightnesses, and a first offset value OFFSET1 corresponding to the second maximum brightness group is greater than 0. Figure 5 The case is a case where the target maximum brightness L_tar corresponds to any one of the second maximum brightness group, that is, a case where the target maximum brightness L_tar is smaller than the reference maximum brightness L_ref.

[0100] Therefore, in Figure 5 In the case of , the first initialization voltage VINT1 is greater than the first power voltage ELVSS.

[0101] Figure 5 The case where the display device is set to emit light with low brightness. At this time, the amount of driving current supplied to the first organic light emitting diode OLED1 is less than Figure 3 Therefore, since the capacitor Co1 is slowly charged, a color dragging phenomenon may be observed.

[0102] Therefore, in Figure 5 In this case, the capacitor Co1 is precharged according to the first offset value OFFSET1 greater than 0 during the period from t3 to t4. Therefore, although a relatively small amount of charge is supplied to the first organic light emitting diode OLED1 by the driving current at time t5, the capacitor Co1 is fully charged at the target time and the first organic light emitting diode OLED1 starts to emit light. Therefore, the color drag phenomenon is prevented.

[0103] Figure 6 is a diagram illustrating an example of a first initialization voltage, a first power voltage, and a second power voltage according to a target maximum brightness.

[0104] Reference Figure 6 Table 1 shows an example of the first offset value OFFSET1, the first power voltage ELVSS, and the second power voltage ELVDD according to the target maximum brightness L_tar. In Table 1, the unit of brightness is nit, and the unit of voltage is volt (V).

[0105] exist Figure 6 In the example, the first offset value OFFSET1 of the target maximum brightness L_tar is compared with the reference value OFFSET1. Figures 3 to 5 The description corresponds to the first offset value OFFSET1, and therefore, repeated description will be omitted.

[0106] According to some example embodiments of the present invention, the first power voltage ELVSS may be approximately inversely proportional to the size of the target maximum brightness L_tar. At this time, regardless of the target maximum brightness L_tar, the second power voltage ELVDD may have a fixed value. Figure 6 In the embodiment, the second power voltage ELVDD is, for example, 4.6V.

[0107] More specifically, the first power voltage ELVSS has a specific voltage value when the target maximum brightness L_tar corresponds to the reference maximum brightness L_ref. In addition, the first power voltage ELVSS may have a voltage value lower than the specific voltage value when the target maximum brightness L_tar corresponds to the first maximum brightness group (i.e., under high brightness conditions). In addition, the first power voltage ELVSS may have a voltage value equal to or higher than the specific voltage value when the target maximum brightness L_tar corresponds to the second maximum brightness group (i.e., under low brightness conditions). Figure 6 , the reference maximum brightness L_ref is, for example, 100 nit, and the specific voltage value of the first power voltage ELVSS is, for example, -2.6V.

[0108] According to some example embodiments of the present invention, under high brightness conditions, the potential difference Vd2 (see Figure 4 ) increases, so that the amount of driving current can be sufficiently guaranteed. Under low brightness conditions, the potential difference Vd3 (see Figure 5 ) is reduced, so that the power consumption can be reduced. At this time, the potential difference Vd1 between the second power voltage ELVDD and the first power voltage ELVSS (see Figure 3 ) becomes a reference when the target maximum brightness L_tar is the reference maximum brightness L_ref.

[0109] In addition, as described above, the second power voltage ELVDD may have a fixed value regardless of the target maximum brightness L_tar. However, in another embodiment, the second power voltage ELVDD and the first power voltage ELVSS may be changed so that the difference between the second power voltage ELVDD and the first power voltage ELVSS is maintained, as shown in FIG. Figure 6 shown.

[0110] Figure 7 are diagrams illustrating display devices according to some example embodiments of the present invention.

[0111] Reference Figure 7, a display device according to some example embodiments of the present invention includes a processor 9, a driver IC 10, a scan driver 20, an emission control driver 30, a pixel unit 40', and a DC-DC converter 50. The driver IC 10 may include a timing controller 11', an initialization voltage generator 12', and a data driver 13.

[0112] exist Figure 7 In the embodiment, the timing controller 11' and the initialization voltage generator 12' are connected to Figure 1 The timing controller 11 and the initialization voltage generator 12 in the embodiment are different. Figure 7 The other components in the embodiment shown are Figure 1 Other components in the illustrated embodiment are substantially the same, and therefore, repeated descriptions will be omitted.

[0113] The pixel unit 40 ′ includes a second pixel including a second organic light emitting diode having an organic material having a band gap different from the band gap of the organic material of the first organic light emitting diode OLED1 .

[0114] The timing controller 11' further includes a second lookup table LUT2 in which a plurality of second initialization voltage values ​​corresponding to a plurality of maximum luminances are recorded. The timing controller 11' determines the value of the second initialization voltage based on the received information about the target maximum luminance L_tar and the second lookup table LUT2.

[0115] As described above, the plurality of first initialization voltage values ​​are obtained by adding the first offset value OFFSET1 to the value of the first power voltage ELVSS. In this embodiment, the plurality of second initialization voltage values ​​are obtained by adding the second offset value to the value of the first power voltage ELVSS. At this time, except at the reference maximum brightness L_ref, the first offset value OFFSET1 and the second offset value may be different from each other. This will be referred to later. Figures 12 to 14 Describe in detail.

[0116] The initialization voltage generator 12 ′ further generates a second initialization voltage to be supplied to the anode of the second organic light emitting diode.

[0117] Figure 8 is a diagram illustrating embodiments of a pixel unit according to some example embodiments of the present invention.

[0118] Reference Figure 8 , a portion of the pixel unit 40' is enlarged and illustrated. The pixel unit 40' includes a first pixel PXij and a second pixel PXi(j+1). Figure 8, the first pixel PXij designates pixel B, and the second pixel PXi(j+1) designates pixel C. However, the second pixel PXi(j+1) may designate pixel A.

[0119] The first organic light emitting diode OLED1 of pixel B may include an organic material having a relatively high emission efficiency (i.e., exhibiting high brightness emission compared to energy consumption). The second organic light emitting diode OLED2 of pixel A or C may include an organic material having a relatively low emission efficiency (i.e., exhibiting low brightness emission compared to energy consumption). The organic light emitting diodes of pixel A and pixel C include organic materials having different band gaps from each other. However, pixel B is the object to be compared in this article, and therefore, for convenience, the difference between the organic light emitting diode of pixel A and the organic light emitting diode of pixel C is ignored.

[0120] Therefore, the first organic light emitting diode OLED1 may have a light emitting surface having an area smaller than that of the second organic light emitting diode OLED2. Figure 8 A case in which pixel B has an area smaller than that of pixel A or pixel C is illustrated.

[0121] Green organic light-emitting diodes typically have the highest emission brightness compared to their energy consumption. Therefore, the first organic light-emitting diode OLED1 can be a green organic light-emitting diode. In this case, the second organic light-emitting diode OLED2 can be a red or blue organic light-emitting diode. That is, pixel B can be a green pixel, pixel A can be a red pixel, and pixel C can be a blue pixel. Alternatively, pixel B can be a green pixel, pixel A can be a blue pixel, and pixel C can be a red pixel.

[0122] However, the embodiments of the present disclosure are not limited thereto, and new organic materials with high emission efficiency may be developed. In this case, the first organic light emitting diode OLED1 may be, for example, a blue organic light emitting diode. In this case, the second organic light emitting diode may be a green or red organic light emitting diode.

[0123] Similarly, the first organic light emitting diode OLED1 may be, for example, a red organic light emitting diode, and the second organic light emitting diode OLED2 may be a green or blue organic light emitting diode.

[0124] However, the first organic light emitting diode OLED1 is not necessarily determined based on the light emitting efficiency. Figure 8 , the sum of the number of pixels A and the number of pixels C is substantially equal to the number of pixels B. Therefore, if the emission efficiencies of the organic materials are similar to each other, as shown in FIG. Figure 8 The area of ​​the light emitting surface shown can be determined to control the emission area of ​​each color.

[0125] Figure 8 The structure of the pixel unit 40 ′ shown may be referred to as a P structure (pentile structure).

[0126] Figure 9 is a diagram illustrating another example of a pixel unit according to some example embodiments of the present invention.

[0127] Figure 9 The pixel unit 40" and Figure 8 The pixel units 40' are identical in terms of the electrical coupling relationship and configuration of the pixels, and therefore, repeated descriptions will be omitted.

[0128] and Figure 8 The pixel unit 40' is different. Figure 9 In the pixel unit 40 ″, the light emitting surface of each pixel may be provided in a diamond shape or a rhombus shape. Figure 9 The structure of the pixel unit 40" may be referred to as a diamond P structure.

[0129] Figure 10 is a diagram illustrating a color dragging phenomenon that occurs when an embodiment of the present disclosure is not applied.

[0130] Reference Figure 10 , which illustrates the difference in emission time between pixel A, pixel B, and pixel C when the embodiments of the present disclosure are not applied.

[0131] For example, to express gray, the lights emitted from the organic light emitting diodes of pixel A, pixel B, and pixel C will be combined when the brightness of each of the lights reaches a certain level.

[0132] However, in Figure 8 and Figure 9 In the structures of the pixel units 40' and 40", the capacitance of the first organic light emitting diode OLED1 of the pixel B per unit area can be large, and the amount of driving current flowing through the first organic light emitting diode OLED1 of the pixel B can be small. Therefore, Figure 10 As shown, the emission time of pixel B may be later than the emission time of pixels A and C.

[0133] For this reason, only pixels A and C can emit light during the initial period. If pixel A is a red pixel and pixel C is a blue pixel, the color observed by the user may be purple. Therefore, when the user scrolls the gray screen, the user may experience a color drag phenomenon where purple is first observed.

[0134] Figure 11 is a diagram illustrating a first pixel and a second pixel according to some example embodiments of the present invention.

[0135] Reference Figure 11 , the first pixel PXij includes a plurality of transistors M1 , M2 , M3 , M4 , M5 , M6 and M7 , a storage capacitor Cst1 and a first organic light emitting diode OLED1 . Figure 11 The first pixel PXij is Figure 2 The first pixels PXij are the same, and therefore, repeated descriptions will be omitted.

[0136] The second pixel PXi(j+1) includes a plurality of transistors M1′, M2′, M3′, M4′, M5′, M6′, and M7′, a storage capacitor Cst1′, and a second organic light emitting diode OLED2. In the second pixel PXi(j+1), overlapping descriptions of components corresponding to those of the first pixel PXij will be omitted.

[0137] The second pixel PXi(j+1) is different from the first pixel PXij in that one electrode of the transistor M2 ′ is coupled to the data line D(j+1) and a second initialization voltage VINT2 is applied to the other electrode of the transistor M7 ′.

[0138] As described above, since the first organic light emitting diode OLED1 of the first pixel PXij has higher emission efficiency than the second organic light emitting diode OLED2 , a relatively small amount of driving current flows compared to the second pixel PXi(j+1).

[0139] Therefore, under low brightness conditions where a very small amount of driving current flows, the time required to charge the capacitance Co1 of the first organic light emitting diode OLED1 is later than the time required to charge the capacitance Co2 of the second organic light emitting diode OLED2, and thus, as shown in FIG. Figure 10 Color dragging as shown may occur.

[0140] Will be in Figures 12 to 14 A driving method for preventing the color dragging phenomenon is described in .

[0141] Figure 12 is a graph illustrating a first initialization voltage and a second initialization voltage when a target maximum brightness is equal to a reference maximum brightness.

[0142] exist Figure 12 In the example, the driving method of the first pixel PXij and the second pixel PXi(j+1) is the same as that of Figure 3 The driving method is substantially the same, and therefore, repeated description will be omitted.

[0143] In the reference maximum brightness L_ref, the first and second offset values ​​OFFSET1 and OFFSET2 may be 0. That is, when the target maximum brightness L_tar is equal to the reference maximum brightness L_ref, the first and second initialization voltages VINT1 and VINT2 and the first power voltage ELVSS may be substantially equal to each other.

[0144] At this time, in the period from t3 to t4, the potential difference between both ends of each of the first and second organic light emitting diodes OLED1 and OLED2 is 0 V, and thus the amount of charge precharged in each of the first and second organic light emitting diodes OLED1 and OLED2 becomes 0.

[0145] As described above, the reference maximum luminance L_ref may be defined as the luminance when sufficient drive current flows to the extent that any color dragging phenomenon is not observed. Figure 12 In the embodiment of the present invention, even when the amount of charges pre-charged in the first organic light emitting diode OLED1 and the second organic light emitting diode OLED2 is 0, the color drag phenomenon is not observed.

[0146] The first power voltage ELVSS may have a specific voltage value when the target maximum brightness L_tar corresponds to the reference maximum brightness L_ref. In addition, the second power voltage ELVDD may have a fixed value regardless of the target maximum brightness L_tar. At this time, the potential difference Vd4 between the second power voltage ELVDD and the first power voltage ELVSS becomes a value which will be described later. Figure 13 and Figure 14 's reference.

[0147] Figure 13 is a graph illustrating a first initialization voltage and a second initialization voltage when a target maximum brightness is greater than a reference maximum brightness in the second embodiment.

[0148] As described above, the first lookup table LUT1 includes a first maximum brightness group exceeding the reference maximum brightness L_ref among the plurality of maximum brightnesses, and the first offset value OFFSET1 corresponding to the first maximum brightness group is less than 0. Figure 13 The case is a case where the target maximum brightness L_tar corresponds to any one of the first maximum brightness group, that is, a case where the target maximum brightness L_tar is greater than the reference maximum brightness L_ref.

[0149] In this embodiment, the second lookup table LUT2 includes a second offset value OFFSET2 corresponding to the first maximum brightness group. The second offset value OFFSET2 corresponding to the first maximum brightness group is smaller than the corresponding first offset value OFFSET1.

[0150] Therefore, in Figure 13 In the case of , the first initialization voltage VINT1 is lower than the first power voltage ELVSS, and the second initialization voltage VINT2 is lower than the first initialization voltage VINT1 and the first power voltage ELVSS.

[0151] Figure 13 The case where the display device is set to emit light with high brightness. At this time, the amount of driving current supplied to the first organic light emitting diode OLED1 and the second organic light emitting diode OLED2 is greater than Figure 12 The amount of driving current in the case of , and therefore the color dragging phenomenon is not observed. Figure 13 In the case of , a reverse voltage is applied to the first and second organic light emitting diodes OLED1 and OLED2 to be initialized, so that degradation of the first and second organic light emitting diodes OLED1 and OLED2 may be delayed.

[0152] In addition, the first initialization voltage VINT1 is set to be greater than the second initialization voltage VINT2, so that the capacitor Co1 of the first organic light emitting diode OLED1 can be pre-charged with a voltage higher than the voltage of the capacitor Co2 of the second organic light emitting diode OLED2. Therefore, at time t5, the emission start time of the first organic light emitting diode OLED1 can be further ahead than the emission start time of the second organic light emitting diode OLED2. Therefore, referring to Figure 10 , the interval between the emission start time of pixels A and C and the emission start time of pixel B can be reduced.

[0153] The first power voltage ELVSS may have a voltage value lower than a specific voltage value when the target maximum brightness L_tar corresponds to the first maximum brightness group. That is, the potential difference Vd5 may be greater than Figure 12 Vd4, and thus the driving current necessary for high-brightness driving can be ensured.

[0154] Figure 14 is a graph illustrating a first initialization voltage and a second initialization voltage when a target maximum brightness is less than a reference maximum brightness in the second embodiment.

[0155] As described above, the first lookup table LUT1 includes a second maximum brightness group smaller than the reference maximum brightness L_ref among the plurality of maximum brightnesses, and the first offset value OFFSET1 corresponding to the second maximum brightness group is greater than 0. Figure 14 The case is a case where the target maximum brightness L_tar corresponds to any one of the second maximum brightness group, that is, a case where the target maximum brightness L_tar is smaller than the reference maximum brightness L_ref.

[0156] In this embodiment, the second lookup table LUT2 includes a second offset value OFFSET2 corresponding to the second maximum brightness group. The second offset value OFFSET2 corresponding to the second maximum brightness group is smaller than the corresponding first offset value OFFSET1.

[0157] Therefore, in Figure 14 In the case of , the first initialization voltage VINT1 is greater than the first power voltage ELVSS, and the second initialization voltage VINT2 is less than the first initialization voltage VINT1. In addition, the second initialization voltage VINT2 may be greater than the first power voltage ELVSS.

[0158] Figure 14 The case where the display device is set to emit light with low brightness. At this time, the amount of driving current supplied to the first organic light emitting diode OLED1 is less than Figure 12 Therefore, since the capacitor Co1 is slowly charged, the color dragging phenomenon can be observed.

[0159] Therefore, in Figure 14 In this case, the capacitor Co1 is precharged according to the first offset value OFFSET1 greater than 0 during the period from t3 to t4. Therefore, although a relatively small amount of charge is supplied to the first organic light emitting diode OLED1 by the driving current at time t5, the capacitor Co1 is fully charged at the target time, and the first organic light emitting diode OLED1 begins to emit light. Therefore, the color drag phenomenon is prevented.

[0160] In addition, the first initialization voltage VINT1 is set to be greater than the second initialization voltage VINT2, so that the capacitor Co1 of the first organic light emitting diode OLED1 can be pre-charged with a voltage higher than the voltage of the capacitor Co2 of the second organic light emitting diode OLED2. Therefore, at time t5, the emission start time of the first organic light emitting diode OLED1 can be further ahead than the emission start time of the second organic light emitting diode OLED2. Figure 10 , the interval between the emission start time of pixels A and C and the emission start time of pixel B can be reduced.

[0161] The first power voltage ELVSS may have a voltage value equal to or higher than a specific voltage value when the target maximum brightness L_tar corresponds to the second maximum brightness group. That is, the potential difference Vd6 is equal to or less than Figure 12 Vd4, which makes it possible to promote reduction in power consumption.

[0162] The first lookup table LUT1 and the second lookup table LUT2 may be configured using a storage device (eg, a memory).

[0163] According to some example embodiments of the present disclosure, in a display device and a driving method thereof, an initialization voltage is controlled according to a brightness condition, so that a color dragging phenomenon can be eliminated or alleviated.

[0164] The electronic or electrical devices and / or any other related devices or components according to the embodiments of the present invention described herein can be implemented using any suitable hardware, firmware (e.g., application specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, the various components of these devices can be formed on a single integrated circuit (IC) chip or on separate IC chips. In addition, the various components of these devices can be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on a substrate. In addition, the various components of these devices can be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in a memory, which can be implemented in the computing device using a standard memory device (e.g., random access memory (RAM)). The computer program instructions can also be stored in other non-transitory computer-readable media (e.g., CD-ROMs, flash drives, etc.). In addition, those skilled in the art will recognize that without departing from the spirit and scope of the exemplary embodiments of the present invention, the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed across one or more other computing devices.

[0165] Aspects of certain example embodiments have been disclosed herein, and although specific terms are employed, they are used and interpreted in a general and descriptive sense only and not for purposes of limitation. In some cases, as will be apparent to those skilled in the art upon filing this application, features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless expressly stated otherwise. Therefore, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as set forth in the appended claims and their equivalents.

Claims

1. A display device, comprising: a processor configured to determine a first offset value and a second offset value; an initialization voltage generator configured to generate a first initialization voltage and a second initialization voltage; as well as A pixel unit, the pixel unit comprising: a first pixel including a first electrode initialization transistor and a first light emitting diode for emitting light having a first color, the first light emitting diode including a first electrode and a second electrode; and a second pixel including a second electrode initialization transistor and a second light emitting diode for emitting light having a second color different from the first color, the second light emitting diode including a third electrode and a fourth electrode, The second electrode of the first light emitting diode and the fourth electrode of the second light emitting diode are used to receive a first power voltage. wherein the first electrode is configured to receive the first initialization voltage through the first electrode initialization transistor, the first initialization voltage having a value obtained by adding the first offset value to a value of the first power voltage; and The third electrode of the second light-emitting diode is used to receive the second initialization voltage through the second electrode initialization transistor, and the second initialization voltage has a value obtained by adding the second offset value to the value of the first power voltage, and the second offset value is different from the first offset value.

2. The display device according to claim 1, in, An area of ​​a light emitting surface of the first light emitting diode is smaller than an area of ​​a light emitting surface of the second light emitting diode.

3. The display device according to claim 1, further comprising: A timing controller includes a first lookup table in which a plurality of first initialization voltage values ​​are stored, the timing controller being configured to determine the value of the first initialization voltage based on received information about the first lookup table.

4. The display device according to claim 3, wherein The plurality of first initialization voltage values ​​are obtained by adding a plurality of first offset values ​​to the value of the first power voltage.

5. The display device according to claim 4, wherein The plurality of first offset values ​​are greater than or equal to zero. The display device according to claim 4 , wherein: The plurality of first offset values ​​are less than zero.

7. The display device according to claim 3, wherein The timing controller further includes a second lookup table in which a plurality of second initialization voltage values ​​are recorded, and the timing controller is configured to determine the value of the second initialization voltage based on received information about the second lookup table.

8. The display device according to claim 7, wherein The plurality of second initialization voltage values ​​are obtained by adding a plurality of second offset values ​​to the value of the first power voltage.

9. The display device according to claim 8, wherein The plurality of second offset values ​​are greater than or equal to zero.

10. The display device according to claim 8, wherein The plurality of second offset values ​​are less than zero.

11. The display device according to claim 8, in, The plurality of second offset values ​​are smaller than the first offset value.

12. The display device according to claim 3, wherein The received information is manually set when a user manipulates the display device, or automatically set using an algorithm linked to a sensor.

13. The display device according to claim 1, in, A second power voltage to be supplied to the first electrode of the first light emitting diode and the third electrode of the second light emitting diode has a fixed value.

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