Organic light-emitting diode display and operating methods for it

Abstract

Organic light-emitting diode (OLED) displays include: a display field (110, 210) that has subpixels; a deterioration detection unit (120, 223) configured to detect a deterioration state of the display field (110, 210); a power supply (130, 221) configured to provide a voltage to drive the subpixels; and a time control controller (140, 222) configured to receive a detection result from the degradation detection unit (130, 221) and to control a high voltage supplied to the subpixels by the power supply, to be continuously varied based on the detection result, wherein the timing controller (140, 222) is configured to continuously vary a lower limit of the high voltage, where the high voltage is varied between a saturation range of the drive transistors of the subpixels of the display field (110, 210) and the lower limit.

Description

[0001] This application claims priority over Korean patent application No. 10-2017-0123374, which was filed on September 25, 2017. BACKGROUND OF THE INVENTION Area of ​​the invention

[0002] The present invention relates to an organic light-emitting diode (OLED) display and an operating method therefor, and in particular to an OLED display and an operating method therefor in which a high voltage applied to subpixels is continuously varied according to the deterioration state of the display field. Discussion of the state of the art

[0003] With the development of information technology, the market for display devices, which serve as a connection medium between users and information, is expanding. Accordingly, organic light-emitting diode (OLED) displays are being used increasingly.

[0004] The OLED display comprises a display array with multiple subpixels, a driver that outputs control signals to operate the display array, and a power supply to generate current for the display array and the driver. The driver includes a line driver that supplies a sampling signal (or gate signal) to the display array and a data driver that supplies a data signal to the display array.

[0005] The OLED display can display an image in such a way that, when control signals, such as a scanning signal and a data signal, are supplied to the subpixels of the display field, selected subpixels emit light.

[0006] The OLED display is used in various applications, such as televisions, navigation systems, video game consoles, personal computers (PCs), wearable devices (watches, glasses, etc.) and mobile phones (smartphones).

[0007] Fig. Figure 1 is a circuit diagram of a subpixel of a conventional OLED display, and Fig. Figure 2 is a current / voltage curve of a drive transistor according to an operating method of the conventional OLED display.

[0008] As in Fig. As shown in Figure 1, the conventional OLED display has a gate line GL1 and a data line DL1 that intersect to define a subpixel area. A switching transistor SW, a driver transistor DTFT, a storage capacitor Cst, and a light-emitting diode OLED are formed within this subpixel area. A high-voltage EVDD is connected to the drain electrode of the driver transistor DTFT, a low-voltage EVSS is connected to the cathode of the LED, and a data voltage V DATA is connected to the data line DL1. The DTFT driver transistor is synchronized with the data voltage V. DATAThe LED is switched on and controls a current flowing in the light-emitting diode (LED) to display an image. The LED emits light due to a high-voltage current from the EVDD, which is transmitted through the DTFT driver transistor. Specific connections between the components are shown in the figure and are not described again here.

[0009] As in the Fig. 1 and Fig. As shown in Figure 2, in a conventional OLED display, the subpixels operate according to a DTFT driver transistor that is driven in a saturation region. Accordingly, the conventional OLED display uses a high-voltage EVDD to drive the DTFT in this saturation region, resulting in unnecessary power consumption.

[0010] To solve this problem, a different OLED display was proposed. Fig. Figure 3 is a graph that represents an operating procedure of another conventional OLED display, and Fig. Figure 4 is a current / voltage curve of a drive transistor according to the operating procedure.

[0011] As shown, a high voltage is switched depending on a criterion (e.g., an average image signal level (APL)) while it is being varied. That is, normal operation (1) and linear operation (2) are performed alternately. Normal operation (1), in which the high voltage is fixed so that the drive transistor operates in the saturation region, requires high power consumption. On the other hand, linear operation can reduce power consumption by varying the high voltage to achieve a data voltage V. data to increase, rather than decrease the high voltage.

[0012] As described above, an OLED display operating in normal mode (1) requires high power consumption due to its use of a high voltage. In linear mode (2), which increases the data voltage to drive the driver transistor, a data voltage that gradually increases from the initial state is used due to degradation of the driver transistor and the display array. Because of the characteristics of linear operation using a high data voltage, the available margin for data voltage increase is insufficient to compensate for degradation, thus reducing the lifetime of the OLED display. In other words, since a voltage is used in response to OLED display degradation, the available voltage margin is inadequate.

[0013] Therefore, a method is needed to increase the lifespan of the OLED display while reducing its energy consumption. US 2017 / 0 193 900 A1, KR 10 2015 0 035 073 A and US 2013 / 0 162 622 A1 each concern further examples of conventional OLED displays. BRIEF SUMMARY OF THE INVENTION

[0014] One object of the present invention is to provide an OLED display and an operating method for it in order to control a display field taking into account both the energy consumption and the lifetime of the display field.

[0015] Another object of the present invention is to provide an OLED display and an operating method for it in order to reduce energy consumption by continuously varying an optimal high voltage for driving a display field.

[0016] Another object of the present invention is to provide an OLED display and an operating method for it in order to increase the lifetime of the OLED display by continuously varying an optimal high voltage for driving a display field.

[0017] The problems are solved by the features of the independent claims. Features of the preferred embodiments are set out in the dependent claims. According to one aspect, an organic light-emitting diode (OLED) display comprises: a display field having subpixels; a degradation detection unit for detecting a degradation state of the display field; a power supply that provides a voltage for driving the subpixels; and a timing controller for receiving a detection result from the degradation detection unit and for controlling a high voltage supplied to the subpixels by the power supply to be continuously varied based on the detection result.

[0018] In the OLED display according to one embodiment, the timing controller continuously varies a lower limit of variable values ​​of a high voltage.

[0019] In the OLED display according to one embodiment, the timing controller can continuously vary the lower limit of the variable high voltage values ​​based on a deterioration measurement of a subpixel that is experiencing the most severe deterioration.

[0020] In the OLED display according to one embodiment, the timing controller can gradually increase the lower limit of the variable high voltage values.

[0021] In one embodiment of the OLED display, the high voltage is varied between a saturation range of the drive transistors of the subpixels of the display field and the lower limit. The high voltage can be varied below a specific ratio or to a specific value relative to a previous value.

[0022] In the OLED display according to one embodiment, the deterioration detection unit can detect the deterioration state with reference to at least one of deterioration factors, including a threshold voltage variation of the drive transistors of the subpixels of the display field, a drive time accumulation value, an average image signal level (APL), and color information input data.

[0023] One operating method of an OLED display according to another aspect includes, among other things: detecting a deterioration state of a display field that has subpixels of the OLED display; and continuously varying a high voltage supplied to the subpixels by a power supply based on a deterioration detection result in order to drive the subpixel drive transistors.

[0024] The operating method of an OLED display according to preferred embodiments of the present invention can include a high voltage that is varied between a gradually increasing lower limit of variable high voltage values ​​and a saturation range of the drive transistors of subpixels of a display field, based on a degradation measurement of a subpixel that is experiencing the most severe degradation, in order to drive the drive transistors of the subpixels of the display field. The method can further include calculating lower limits of variable high voltage values ​​for driving the drive transistors of the subpixels of the display field based on a degradation measurement of a subpixel that is experiencing the most severe degradation. The method can further include continuously calculating a new high voltage within a range of the lower limit of the variable high voltage values.The method can further include calculating a data voltage adapted to the new high voltage and supplying the data voltage to the subpixels of the display field to drive the driver transistors. Driving the driver transistors can involve providing a high voltage that varies between a gradually increasing lower limit of the variable high voltage values ​​and a saturation region of the driver transistors.

[0025] The OLED display and the operating method therefor according to the present invention can have the following advantages.

[0026] Firstly, it is possible to reduce energy consumption by controlling the display field taking into account both energy consumption and the lifespan of the display field.

[0027] Secondly, it is possible to increase the lifespan of the display field by controlling the display field taking into account both energy consumption and the lifespan of the display field. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a circuit diagram of a subpixel of a conventional OLED display. Fig. Figure 2 shows a current / voltage curve of a drive transistor according to an operating procedure of the conventional OLED display. Fig. Figure 3 is a graph showing an operating procedure of another conventional OLED display. Fig. Figure 4 shows a current / voltage curve of a drive transistor in the other conventional OLED display. Fig. Figure 5 is a block diagram representing a schematic configuration of an OLED display according to an embodiment of the present invention. Fig. Figure 6 is a block diagram representing a schematic configuration of an OLED display according to another embodiment of the present invention. Fig. Figure 7 is a graph showing a deterioration trend of an OLED element. The Fig. 8A and Fig. Figure 8B are graphs showing average image levels (APL) before and after the degradation of a display field. Fig. Figure 9 is a graph showing a variation of a high voltage applied to drive transistors of the display field of the OLED display according to the present invention. Fig. Figure 10 is a graph showing a variation of a lower limit of variable values ​​of high voltage in accordance with a deterioration factor. Fig. Figure 11 is a graph showing the proportion of linear operation in relation to the total control time according to a deterioration factor. Fig. Figure 12 is a flowchart that represents a process of an operating procedure of the OLED display according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] Specific structural and functional descriptions relating to embodiments of the present invention, disclosed below, serve the purpose of explaining the embodiments of the present invention, and the present invention can be implemented in various forms and is not limited to the embodiments described below.

[0029] The present invention can be modified in various ways and implemented in many alternative forms. While the embodiments are suitable for various modifications and alternative forms, specific embodiments are accordingly shown by way of example in the drawings and are described in detail herein. However, it should be understood that the intention is not to limit the embodiments to the specific disclosed forms, but rather that, on the contrary, the embodiments are intended to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the disclosure.

[0030] Although terms such as "first" and "second" may be used to describe different elements, the elements should not be limited by these terms. These terms merely serve to distinguish identical or similar elements from one another. For example, a first element may be called a second element, and similarly, the second element may be referred to as the first element, without altering the scope of the present invention.

[0031] When an element is "coupled" or "connected" to another element, it should be understood that a third element may exist between the two elements, even though the element may be directly coupled or connected to the other element. When an element is "directly coupled" or "directly connected" to another element, it should be understood that no element exists between the two elements. Other representations describing relationships between elements, such as "between," "directly between," or "adjacent to" and "directly adjacent," should be understood in the same way.

[0032] The terms used in this description serve the purpose of describing specific embodiments and are not intended to limit the present invention. It is intended that the singular forms also include the plural forms, unless the context clearly indicates otherwise. Furthermore, it is understood that the expressions "include" or "have" when used in this description specify the presence of the indicated features, regions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0033] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meanings as they are normally understood by people skilled in the art in the field to which exemplary embodiments relate. It is further understood that terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant prior art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0034] If a particular embodiment can be realized in another way, a function or operation specified in a particular block can be executed in a different order than indicated in a flowchart. For example, two consecutive blocks can be executed simultaneously or in reverse order, depending on the function or operation in question.

[0035] Embodiments of the present invention are described below with reference to the accompanying drawings.

[0036] Depending on the direction of light emission, OLED displays can be implemented as an upward-emitting ("top-emission") type, a downward-emitting ("bottom-emission") type, or as a dual-emission type.

[0037] OLED displays can be implemented in an inverted staggered structure featuring an etched back-channel (BCE) structure or an etch stopper (ES), a staggered structure, or a coplanar structure, depending on a transistor channel structure.

[0038] OLED displays can be realized based on oxide, low-temperature polysilicon (LTPS), amorphous silicon (a-Si) or polysilicon (p-Si), depending on the semiconductor material of a transistor.

[0039] OLED displays can be configured for use in televisions, navigation systems, video game consoles, personal computers (PCs), wearable devices (watches, glasses, etc.), mobile phones (smartphones), and the like.

[0040] Fig. Figure 5 is a block diagram illustrating a schematic configuration of an OLED display 100 according to an embodiment of the present invention. The OLED display comprises a display field 110 with subpixels, a deterioration detection unit 120 for detecting a deterioration state of the display field 110, a power supply 130 that provides a voltage for driving the subpixels, and a timing controller 140 that receives a detection result from the deterioration detection unit and controls a high voltage supplied to the subpixels by the power supply to be continuously varied based on the detection result, and supplies this voltage to the subpixels. The timing controller 140 may include a memory (not shown) that stores information for driving the OLED display 100 and compensation data for compensation (including deterioration compensation).

[0041] The deterioration detection unit 120 detects the degree of deterioration of the display field 110 using various types of information to determine its deterioration state. A deterioration factor used by the deterioration detection unit 120 to determine the degree of deterioration of the display field 110 may include one or more of the threshold voltage variations of the drive transistors of the subpixels of the display field 110, a drive time accumulation value, an average image signal level (APL), and color information input data.

[0042] Fig. Figure 6 is a block diagram representing a schematic configuration of an OLED display 200 according to another embodiment of the present invention. In contrast to the one in Fig. In the embodiment shown in Figure 5, the OLED display 200 has a configuration in which a display field 210 and an assembly 220 are separated from each other by a predetermined distance. Here, a power supply 221, a timing controller 222, and a deterioration detection unit 223 are included in the assembly 220. The timing controller 222 can have a memory (not shown) that stores information for driving the OLED display 200 and compensation data for deterioration compensation.

[0043] Fig. Figure 7 is a graph showing the degradation trend of an OLED element. The graph illustrates the degradation trend of an OLED contained within subpixels of the display field. The graph shows that the variation before / after degradation is the anode voltage of the OLED, i.e., the voltage at the source node of the driver transistor (see, for example, Figure 7). Fig. 1), according to an increase in the current Ioled of the OLED.

[0044] The Fig. 8A and Fig. Figure 8B shows graphs displaying mean image signal levels (APL) before and after the display field degradation. The APL represents an average of the ratios of the luminance of the current frame of an image to the maximum luminances of the respective frames, and is closer to 100% for a brighter image and closer to 0% for a darker image. The APL can be calculated for a single image or for multiple images. That is, the APL can be calculated per frame or per frame block consisting of multiple frames. The APL can be calculated to reflect image properties of an input frame. For example, the APL can be calculated to correlate with the number of red, green, and blue pixels emitting light to represent an image contained within an input frame.Furthermore, the APL can be calculated by assigning a predefined weight to the number of red, green, and blue pixels that emit light.

[0045] The peak luminance of an image decreases as the APL increases and increases as the APL decreases. However, in conventional OLED displays, a drive voltage is applied to the OLEDs via a drive voltage line (for example, the voltage of the source node of the DTFT driver transistor). Fig. 1) is supplied, is set to a DC voltage level, and thus unnecessary energy consumption occurs for an image with low peak luminance.

[0046] The proportion of linear operation is high compared to normal operation in the initial state, as shown in Fig. Figure 8A shows that the proportion of linear operation gradually decreases in a deteriorated state, as shown in Figure 8A. Fig. 8B is shown. This means that the APL gradually increases as the deterioration progresses.

[0047] Fig. Figure 9 is a graph showing the change in a high voltage applied to the drive transistors of the display field of the OLED display according to the present invention. The timing controller continuously varies a lower limit of variable high voltage values. Here, the timing controller continuously varies the lower limit of variable high voltage values ​​based on a degradation measurement of a subpixel that is experiencing the most severe degradation. The timing controller gradually increases the lower limit of variable high voltage values. Here, the high voltage varies between a saturation range of the drive transistors of the subpixels of the display field and the lower limit.

[0048] Fig. Figure 10 is a graph showing the variation of the lower bound of variable high-voltage values ​​in accordance with a deterioration factor. As shown, the lower bound of the variable high-voltage values ​​gradually increases in accordance with the progression of the deterioration factor. However, the lower bound can be controlled to decrease in accordance with the progression of the deterioration factor if necessary.

[0049] Fig. Figure 11 is a graph showing the proportion of linear operation relative to the total control time according to a deterioration factor. The proportion of linear operation relative to the total control time gradually decreases in accordance with the progression of the deterioration factor. However, the proportion of linear operation relative to the total control time can be controlled so that it increases, if necessary, in accordance with the progression of the deterioration factor.

[0050] Fig.Figure 12 is a flowchart illustrating a process of an operating procedure for the OLED display according to the present invention. A deterioration state of the display field is detected by the deterioration detection unit. The deterioration state is detected according to various deterioration factors. A position with the largest delta value Ä, measured per data driver channel, and a degree of deterioration are transmitted to an analog-to-digital converter (ADC) of a data driver and to the memory of the timing controller. The delta value Ä can include a threshold voltage of the drive transistors of the subpixels, an accumulation value of image data, a drive time, and the like (S1201).

[0051] Lower limits of variable values ​​of a high voltage EVDD are calculated based on a measurement of a subpixel that suffers the most severe degradation (S1202).

[0052] New high voltages EVDD are continuously calculated within the range of the lower limits of the variable values ​​of the high voltage EVDD. Here, the high voltage is varied below a specific ratio or a specific value relative to a previous value (S1203).

[0053] A data voltage Vdata, adapted to a new high voltage EVDD, is calculated and supplied to the subpixels to drive the subpixel drive transistors (S1204).

[0054] As described above, the OLED displays according to the present invention gradually increase the lower limits of the variable high voltage values ​​in accordance with the passage of time or an increase in the degree of deterioration. Here, the high voltage is varied between the saturation range of the drive transistors of the subpixels of the display field and a lower limit of the variable high voltage values. Accordingly, the energy consumption of the OLED displays according to the present invention can be reduced, and their lifespan can be increased.

[0055] Although preferred embodiments of the present invention have been described above, the person skilled in the art will recognize that various modifications and variations can be made to the present invention without departing from the spirit or scope of the present invention as disclosed in the attached claims.

Claims

[1] Organic light-emitting diode (OLED) displays include: a display field (110, 210) that has subpixels; a deterioration detection unit (120, 223) configured to detect a deterioration state of the display field (110, 210); a power supply (130, 221) configured to provide a voltage to drive the subpixels; and a time control controller (140, 222) configured to receive a detection result from the degradation detection unit (130, 221) and to control a high voltage supplied to the subpixels by the power supply, to be continuously varied based on the detection result, wherein the timing controller (140, 222) is configured to continuously vary a lower limit of the high voltage, where the high voltage is varied between a saturation range of the drive transistors of the subpixels of the display field (110, 210) and the lower limit. [2] OLED display according to claim 1, wherein the timing controller (140, 222) is configured to continuously vary the lower limit of the high voltage based on a deterioration measurement of a subpixel that is experiencing the most severe deterioration. [3] OLED display according to claim 1 or 2, wherein the timing controller (140, 222) is configured to gradually increase the lower limit of the high voltage. [4] OLED display according to claim 1, wherein the high voltage is varied to below a certain ratio or a certain value with respect to a previous value. [5] OLED display according to one of the preceding claims, wherein the deterioration detection unit (120, 223) is configured to detect the deterioration state with reference to at least one of the deterioration factors, including a threshold voltage variation of the drive transistors of the subpixels of the display field (110, 210), a drive time accumulation value, an average image signal level (APL) and color information input data. [6] Operating method of an organic light-emitting diode (OLED) display, the method comprising: Detecting a deterioration state of a display field (110, 210) that has subpixels of the OLED display; Controlling a high voltage applied to the subpixels to drive them, continuously varying them based on the acquisition result; and Continuous variation of a lower limit of the high voltage, wherein the driving of the subpixels includes providing a high voltage that varies between a gradually increasing lower limit of the high voltage and a saturation region of the driving transistors of the subpixels. [7] Operating method according to claim 6, wherein the control further comprises: Calculating lower limits of the high voltage for driving the drive transistors of the subpixels of the display field based on a deterioration measurement of a subpixel that suffers the most severe deterioration; Continuous calculation of a new high voltage within a range of the lower limits of the high voltage; Calculating a data voltage adapted to the new high voltage; and Supplying the data voltage to the subpixels of the display field to control the drive transistors.

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