Display device

Abstract

A display device is provided. The display device may comprise: a display panel including a pixel array in which pixels having a plurality of inorganic light-emitting elements are arranged in a plurality of row lines, and sub-pixel circuits corresponding to the inorganic light-emitting elements of the pixel array; and a driving unit for driving the sub-pixel circuits. Each of the sub-pixel circuits can include: a pulse amplitude modulation (PAM) circuit which includes a driving transistor, and which drives the driving transistor so as to provide a driving current to a corresponding inorganic light-emitting element on the basis of an image data voltage; and a first transistor having a gate terminal connected to a gate terminal of the driving transistor and having a drain terminal connected to a source terminal of the driving transistor.

Description

Display device

[0001] The present disclosure relates to a display device, and more specifically, to a display device comprising a pixel array made of self-emissive elements.

[0002] In a display panel that drives inorganic light-emitting diodes (hereinafter, LED refers to inorganic light-emitting diodes) such as red LEDs (Light Emitting Diodes), green LEDs, and blue LEDs as subpixels, the gradation of the subpixels is expressed through a Pulse Amplitude Modulation (PAM) driving method. In this case, the gradation of the emitted light is changed according to the magnitude of the driving current. Meanwhile, heat is generated as the driving current flows through the subpixels. At this time, deviations occur in the characteristics of the inorganic light-emitting diodes (e.g., luminous efficiency, critical voltage for turning on) depending on the heat generated in the subpixels.

[0003] The information described above may be provided as related art for the purpose of aiding understanding of the present disclosure. No claim or determination is made as to whether any of the foregoing may be applied as prior art related to the present disclosure.

[0004] According to one embodiment of the present disclosure, a display device may include a pixel array in which pixels composed of a plurality of inorganic light-emitting elements are arranged in a plurality of row lines, a display panel including sub-pixel circuits corresponding to the inorganic light-emitting elements of the pixel array, and a driving unit for driving the sub-pixel circuits. Each of the sub-pixel circuits may include a driving transistor, a pulse amplitude modulation (PAM) circuit for driving the driving transistor to provide a driving current to a corresponding inorganic light-emitting element based on an image data voltage, and a first transistor having a gate terminal connected to the gate terminal of the driving transistor and a drain terminal connected to the source terminal of the driving transistor.

[0005] In relation to the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0006] FIG. 1 is a drawing for explaining the pixel structure of a display panel according to one embodiment of the present disclosure.

[0007] FIGS. 2a and 2b are conceptual diagrams illustrating a driving method of a display panel according to one embodiment.

[0008] FIG. 3 is a cross-sectional view of a display panel according to one embodiment.

[0009] FIG. 4 is a block diagram illustrating the configuration of a display device according to one embodiment.

[0010] FIG. 5 is a detailed block diagram of a display device according to one embodiment.

[0011] FIG. 6 is a schematic circuit diagram of a subpixel circuit according to one embodiment.

[0012] FIG. 7 is a diagram illustrating an example of current flowing through a display panel in a light-emitting section according to one embodiment.

[0013] FIG. 8 is a graph illustrating an example of a driving current and a current magnitude according to the magnitude of the image data voltage, according to one embodiment.

[0014] In describing the present disclosure, detailed descriptions of related prior art are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the present disclosure. Additionally, redundant descriptions of identical components are to be omitted whenever possible.

[0015] The suffix "bu" for components used in the following description is assigned or used interchangeably solely for the ease of drafting the specification, and does not inherently possess a distinct meaning or role.

[0016] The terms used in this disclosure are for describing embodiments and are not intended to limit or / or restrict this disclosure. Additionally, any singular expression for any component used in this disclosure includes a plural expression unless the context makes it evident otherwise.

[0017] In this disclosure, terms such as 'comprising' or 'having' are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0018] Expressions such as "first," "second," "first," or "second" used in this disclosure may modify various components regardless of order and / or importance, and are used only to distinguish one component from another and do not limit said components.

[0019] Meanwhile, in the present disclosure, when it is stated that a certain component (e.g., a first component) is "connected" to another component (e.g., a second component), it should be understood that the certain component (e.g., a first component) may be directly connected to the other component (e.g., a second component), or that the certain component (e.g., a first component) may be connected to the other component (e.g., a second component) through another component (e.g., a third component).

[0020] On the other hand, when it is stated that a certain component (e.g., a first component) is "directly connected" to another component (e.g., a second component), it may be understood that there is no other component (e.g., a third component) between said certain component (e.g., a first component) and said other component (e.g., a second component).

[0021] Unless otherwise defined, the terms used in the embodiments of the present disclosure may be interpreted in the sense commonly known to those skilled in the art.

[0022] Various embodiments of the present disclosure will be described in detail below with reference to the attached drawings.

[0023] FIG. 1 is a drawing for explaining the pixel structure of a display panel according to one embodiment of the present disclosure.

[0024] Referring to FIG. 1, the display panel (100) includes a plurality of pixels (10), i.e., a pixel array, that are disposed (or arranged) in a matrix form.

[0025] In the present disclosure, a pixel array may include a plurality of row lines or a plurality of column lines. Row lines or column lines may be referred to by various expressions representing the same or similar concepts. For example, row lines may be replaced with expressions such as horizontal lines, scan lines, or gate lines, and column lines may be replaced with expressions such as vertical lines or data lines, but are not limited to the examples described above.

[0026] Additionally, the terms row line, column line, horizontal line, and vertical line are used to refer to lines formed by pixels on a pixel array, and the terms scan line, gate line, and data line may be used to refer to actual wiring on a display panel (100) through which data or signals are transmitted.

[0027] According to one embodiment, each pixel (10) of a pixel array may include three types of subpixels, such as a red (R) subpixel (20-1), a green (G) subpixel (20-2), and a blue (B) subpixel (20-3). Each pixel (10) may include a plurality of inorganic light-emitting elements constituting the subpixels (20-1, 20-2, 20-3).

[0028] For example, each pixel (10) may include three types of inorganic light-emitting elements, such as an R inorganic light-emitting element constituting an R subpixel (20-1), a G inorganic light-emitting element constituting a G subpixel (20-2), and a B inorganic light-emitting element constituting a B subpixel (20-3).

[0029] For example, each pixel (10) may include three blue inorganic light-emitting elements. In this case, a color filter for implementing R, G, and B colors may be provided on each inorganic light-emitting element. At this time, the color filter may be a quantum dot (QD) color filter, but is not limited thereto.

[0030] Meanwhile, although not illustrated, a sub-pixel circuit for driving an inorganic light-emitting element may be provided in the display panel (100) for each inorganic light-emitting element. Each sub-pixel circuit may provide a driving current to a corresponding inorganic light-emitting element based on an image data voltage applied from the outside.

[0031] According to one embodiment, the image data voltage includes a constant current generator data voltage. Each subpixel circuit can express the gradation of the image by providing a driving current of a magnitude corresponding to the image data voltage to an inorganic light-emitting element.

[0032] According to one embodiment, subpixel circuits included in each row line of a display panel (100) can be driven in the order of “setting (or programming) an image data voltage” and “providing a driving current based on the set image data voltage”.

[0033] According to one embodiment, the subpixel circuits included in each row line of the display panel (100) can be driven sequentially in the order of the row lines.

[0034] For example, the image data voltage setting operation of subpixel circuits included in one row line (e.g., a first row line) and the image data voltage setting operation of subpixel circuits included in the next row line (e.g., a second row line) can be performed sequentially in the order of row lines. In addition, the driving current providing operation of subpixel circuits included in the one row line (e.g., a first row line) and the driving current providing operation of subpixel circuits included in the next row line (e.g., a second row line) can also be performed sequentially in the order of row lines.

[0035] Meanwhile, in FIG. 1, an example was given in which subpixels (20-1 to 20-3) are arranged in an L-shape with the left and right reversed within a single pixel area. However, the embodiment is not limited thereto, and the R, G, and B subpixels (20-1 to 20-3) may be arranged in a line within the pixel area, or may be arranged in various forms depending on the embodiment.

[0036] In addition, Figure 1 describes an example in which three types of subpixels constitute one pixel. However, depending on the embodiment, four types of subpixels such as R, G, B, and W (white) may constitute one pixel, and any number of other subpixels may constitute one pixel.

[0037] FIGS. 2a and 2b are conceptual diagrams illustrating a driving method of a display panel according to one embodiment.

[0038] FIG. 2a illustrates a method of driving a display panel during one video frame time. In FIG. 2a, the vertical axis represents the row line of the display panel (100), and the horizontal axis represents time. Additionally, the data setting section represents a driving section of the display panel (100) in which a video data voltage is set to the sub-pixel circuits included in each row line, and the light emission section represents a driving section of the display panel (100) in which the sub-pixel circuits included in each row line provide a driving current to an inorganic light-emitting element based on the video data voltage set in the data setting section. The inorganic light-emitting elements emit light according to the driving current within the light emission section.

[0039] Conventionally, the light emission phase proceeded in batches after the image data voltage was first set for the entire low line of the display panel. In this case, since the entire low line of the display panel emits light simultaneously during the light emission phase, a high peak current is required, which leads to a problem of increased peak power consumption required for the product. As peak power consumption increases, the capacity of the power supply unit, such as the SMPS (Switched Mode Power Supply) installed in the product, increases, which leads to increased costs and volume, resulting in design constraints.

[0040] Meanwhile, according to one embodiment, the data setting section and the light emission section (specifically, a plurality of light emission sections) of each row line may proceed sequentially in the order of row lines. Hereinafter, a driving method in which the data setting section and the light emission section proceed sequentially in the order of row lines, as shown in FIG. 2a or FIG. 2b, may be referred to as a "progressive driving method."

[0041] In the case of a progressive driving method, the number of low lines emitting light simultaneously is reduced compared to conventional technology, so the required peak current is lowered, and accordingly, peak power consumption can be reduced.

[0042] FIG. 2b is a drawing for explaining a progressive driving method of a display panel (100) according to one embodiment.

[0043] FIG. 2b conceptually illustrates the driving method of a display panel (100) for three consecutive video frames. In FIG. 2b, the vertical axis may represent the row line of the display panel (100), and the horizontal axis may represent time.

[0044] Referring to FIG. 2b, an example is given in which a display panel (100) is composed of 312 row lines and four light-emitting sections (22-1 to 22-4) proceed based on the image data voltage set in the data setting section (21). However, it goes without saying that the number of row lines or the number of light-emitting sections are not limited to this.

[0045] Referring to FIG. 2b, for one video frame, one data setting section (21) and a plurality of light emission sections (22-1 to 22-4) may proceed for each row line.

[0046] According to one embodiment, during the data setting interval (21), an image data voltage for the corresponding image frame may be set in the subpixel circuits included in the row line. Additionally, in each light emission interval (22-1 to 22-4), a driving current may be provided to the corresponding inorganic light-emitting element based on the image data voltage set during the data setting interval (21).

[0047] According to one embodiment, the driving unit can apply a control signal (hereinafter referred to as a scan signal) for setting an image data voltage to the subpixel circuits of each row line during a data setting interval (21).

[0048] According to one embodiment, the driving unit may apply a control signal (hereinafter referred to as an emission signal) for controlling a driving current providing operation to the subpixel circuits of each row line during each light-emitting section (22-1 to 22-4).

[0049] Referring to FIG. 2b, it can be seen that the data setting section (21) and each light-emitting section (22-1 to 22-4) proceed sequentially in the order of the low lines for the entire low line of the display panel (100). The driving unit can apply a scan signal to the sub-pixel circuits in the order of the low lines from the first low line to the last low line of the display panel (100). Additionally, the driving unit can apply an emission signal to the sub-pixel circuits in the order of the low lines from the first low line to the last low line of the display panel (100).

[0050] Meanwhile, according to one embodiment, as shown in FIG. 2b, the first light-emitting section (22-1) of each row line is temporally continuous with the data setting section (21), and each of the plurality of light-emitting sections (22-1 to 22-4) may have a preset time interval.

[0051] At this time, the number of light-emitting sections proceeding in each row line for one video frame and the preset time interval between the light-emitting sections may be set based on the size of the display panel (100) and / or the shutter speed of the camera, etc. However, it is not limited thereto.

[0052] Generally, since the shutter speed of a camera is several times faster than the time of one video frame, if the display panel (100) is driven so that one light-emitting section proceeds in the order of low lines from the first low line to the last low line during the time of one video frame, the image displayed on the display panel (100) captured by the camera may be distorted.

[0053] Accordingly, according to one embodiment, a display panel (100) is driven so that a plurality of light-emitting sections proceed at preset time intervals during one video frame time, and by setting the preset time intervals based on the speed of the camera, the image displayed on the display panel (100) captured by the camera is not distorted even if the display panel (100) is captured at any moment.

[0054] FIG. 3 is a cross-sectional view of a display panel according to one embodiment. In FIG. 3, for convenience of explanation, only one pixel included in the display panel (100) is shown.

[0055] According to FIG. 3, the display panel (100) may include a glass substrate (80), a TFT layer (70), and inorganic light-emitting elements R, G, B (120-1, 120-2, 120-3). In this case, the aforementioned subpixel circuit may be implemented as a Thin Film Transistor (TFT) and included in the TFT layer (70) on the glass substrate (80).

[0056] According to one embodiment, each of the inorganic light-emitting elements R, G, and B (120-1, 120-2, 120-3) can be mounted on a TFT layer (70) so as to be electrically connected to a corresponding subpixel circuit to form the aforementioned subpixel.

[0057] According to one embodiment, a subpixel circuit (110) for providing a driving current to an inorganic light-emitting element (120-1, 120-2, 120-3) exists in the TFT layer (70) for each inorganic light-emitting element (120-1, 120-2, 120-3), and each inorganic light-emitting element (120-1, 120-2, 120-3) can be mounted or disposed on the TFT layer (70) so as to be electrically connected to a corresponding subpixel circuit.

[0058] Meanwhile, FIG. 3 illustrates an example in which the inorganic light-emitting elements R, G, B (120-1, 120-2, 120-3) are flip-chip type micro LEDs. However, this is not limited thereto, and depending on the embodiment, the inorganic light-emitting elements R, G, B (120-1, 120-2, 120-3) may be lateral type or vertical type micro LEDs.

[0059] According to one embodiment, at least some of the various components described above that may be included in the driving unit (500) are disposed on the rear surface of the glass substrate (80) and may be connected to sub-pixel circuits (110) formed on the TFT layer (70) through connecting wires.

[0060] According to one embodiment, at least some of the various components that may be included in the driving unit (500) may be formed on a TFT layer together with subpixel circuits and connected to the subpixel circuits.

[0061] According to one embodiment, the TFT layer (70) has a remaining area in addition to the area occupied by one pixel (10) (in this area, subpixel circuits (110) corresponding to each of the R, G, and B subpixels included in the pixel (10) exist), and some of the various components described above may be formed in such remaining areas.

[0062] According to one embodiment, a gate driver may be implemented in the remaining area of ​​the TFT layer (70). Thus, a structure in which a gate driver is formed inside the TFT layer (70) may be called a GIP (Gate In Panel) structure, but the name is not limited thereto.

[0063] In the above, the case where the substrate on which the TFT layer (70) is formed is a glass substrate (80) was given as an example, but the embodiment is not limited thereto. For instance, the TFT layer (70) may be formed on a synthetic resin substrate. In this case, the subpixel circuits (100) of the TFT layer (70) and the driving unit (500) may be connected through a hole penetrating the synthetic resin substrate.

[0064] Meanwhile, an example in which a sub-pixel circuit (110) is implemented on a TFT layer (70) has been described. However, the embodiment is not limited thereto. That is, according to another embodiment of the present disclosure, when implementing the sub-pixel circuit (110), it is possible to implement a pixel circuit chip in the form of a micro-IC in sub-pixel units or pixel units without using the TFT layer (70) and mount it on a substrate. At this time, the location where the sub-pixel circuit chip is mounted may be, for example, around a corresponding inorganic light-emitting element (120), but is not limited thereto.

[0065] Additionally, although an example has been given in which a gate driver is formed within the TFT layer (70), the embodiment is not limited thereto. That is, according to another embodiment of the present disclosure, the gate driver may be implemented as a gate driver chip in the form of a micro IC and mounted on the TFT layer (70).

[0066] In addition, in the various embodiments of the present disclosure described above, the TFT constituting the TFT layer (or TFT panel) is not limited to a specific structure or type; that is, the TFT cited in the various examples of the present disclosure can be implemented as an LTPS (Low Temperature Poly Silicon) TFT, an oxide TFT, a silicon (poly silicon or a-silicon) TFT, an organic TFT, a graphene TFT, etc., and can also be applied by manufacturing only a P-type (or N-type) MOSFET in a Si wafer CMOS process.

[0067] FIG. 4 is a block diagram illustrating the configuration of a display device according to one embodiment. According to FIG. 4, the display device (1000) includes a display panel (100) and a driving unit (500).

[0068] According to one embodiment, the driving unit (500) can drive the display panel (100). Specifically, the driving unit (500) can drive the display panel (100) by providing various control signals, data signals, driving voltages, etc. to the display panel (100).

[0069] According to one embodiment, the display panel (100) can be driven in a row line order. To this end, the driving unit (500) may include a gate driver for driving pixels on a pixel array in row line units. The gate driver can drive pixels in row line units by providing a scan signal and an emission signal for each row line. At this time, the gate driver providing the scan signal can be referred to as a scan driver, and the gate driver providing the emission signal can be referred to as an emission driver.

[0070] According to one embodiment, the driving unit (500) may include a power IC (or a driving voltage providing circuit) for providing various DC voltages (e.g., driving voltage, ground voltage (GND), etc.) or image data voltages, etc., to each subpixel circuit included in the display panel (100).

[0071] According to one embodiment, at least some of the various components described above that may be included in the driving unit (500) are placed on a PCB (Printed Circuit Board) separate from the display panel (100) and may be connected to sub-pixel circuits formed on the TFT layer of the display panel (100) through FOG (Film On Glass) wiring.

[0072] According to one embodiment, at least some of the various components described above may be arranged on a film in the form of a Chip On Film (COF) and connected to sub-pixel circuits formed on a TFT layer of a display panel (100) through Film On Glass (FOG) wiring.

[0073] According to one embodiment, at least some of the various components described above may be disposed on the back surface (the side opposite to the side where the TFT layer is formed with respect to the glass substrate) of the display panel (100) in the form of a Chip On Glass (COG), and may be connected to sub-pixel circuits formed on the TFT layer of the display panel (100) through connecting wires.

[0074] According to one embodiment, at least some of the various components described above may be formed on a TFT layer together with subpixel circuits formed on a TFT layer within a display panel (100) and connected to the subpixel circuits.

[0075] According to one embodiment, the driving unit (500) can drive the display panel (100) in a progressive driving manner. To this end, the driving unit (500) can set an image data voltage in the order of low lines to the sub-pixel circuits of the display panel (100) during a data setting period, and drive the sub-pixel circuits so that the pixels of the pixel array emit light in the order of low lines based on the set image data voltage during a light emission period.

[0076] According to one embodiment, the display panel (100) includes a pixel array as described above in FIG. 1 and can display an image corresponding to an applied image data voltage.

[0077] According to one embodiment, each subpixel circuit included in the display panel (100) can provide a driving current, with its magnitude and driving time (or pulse width) controlled based on the image data voltage, to a corresponding inorganic light-emitting element.

[0078] According to one embodiment, inorganic light-emitting elements constituting a pixel array emit light according to a driving current provided from a corresponding sub-pixel circuit, and accordingly, an image can be displayed on a display panel (100).

[0079] FIG. 5 is a detailed block diagram of a display device according to one embodiment. In describing FIG. 5, details that overlap with the foregoing will be omitted.

[0080] According to one embodiment, the display device (1000) may include at least one display module. For example, the display device (1000) may include a plurality of display modules and a TCON (not shown). The display modules may be assembled or arranged in a matrix form to form a modular display panel. According to one embodiment, it is obvious that a display device of any different size or different resolution can be implemented by combining a plurality of display modules. Meanwhile, the configuration and driving method of the display device (1000) may be as described above through FIGS. 1 to 8.

[0081] Referring to FIG. 5, the display device (1000) includes a display panel (100) comprising a subpixel circuit (110) and an inorganic light-emitting element (120), and a driving unit (500).

[0082] According to one embodiment, the display panel (100) may have a structure in which a subpixel circuit (110) is formed on a glass substrate as described above and an inorganic light-emitting element (120) is mounted on the subpixel circuit (110), but is not limited thereto. Meanwhile, for convenience of explanation, only one subpixel-related configuration included in the display panel (100) is shown in FIG. 5, but it is known that a subpixel circuit (110) and an inorganic light-emitting element (120) are provided for each subpixel.

[0083] According to one embodiment, an inorganic light-emitting element (120) is mounted on a subpixel circuit (110) so as to be electrically connected to the subpixel circuit (110), and can emit light based on a driving current provided from the subpixel circuit (110).

[0084] According to one embodiment, the inorganic light-emitting element (120) constitutes a subpixel of the display panel (100), and there may be multiple types depending on the color of the light emitted. For example, the inorganic light-emitting element (120) may be one of a red (R) inorganic light-emitting element that emits red light, a green (G) inorganic light-emitting element that emits green light, or a blue (B) inorganic light-emitting element that emits blue light.

[0085] The type of subpixel described above can be determined according to the type of inorganic light-emitting element (120). That is, an R inorganic light-emitting element can form an R subpixel (20-1), a G inorganic light-emitting element can form a G subpixel (20-2), and a B inorganic light-emitting element can form a B subpixel (20-3).

[0086] Here, the inorganic light-emitting element (120) may refer to a light-emitting element made using an inorganic material, which is different from an OLED (Organic Light Emitting Diode) made using an organic material. In particular, according to one embodiment, the inorganic light-emitting element (120) may be a micro light-emitting diode (micro LED or μLED) having a size of 100 micrometers (μm) or less.

[0087] A display panel in which each subpixel is implemented as a micro LED can be referred to as a micro LED display panel. A micro LED display panel is a type of flat panel that may be composed of multiple inorganic light-emitting diodes (inorganic LEDs), each measuring 100 micrometers or less. Micro LED display panels can provide better contrast, response time, and energy efficiency compared to liquid crystal display (LCD) panels that require a backlight. Meanwhile, while both organic light-emitting diodes (OLEDs) and micro LEDs are energy-efficient, micro LEDs can provide better performance than OLEDs in terms of brightness, luminous efficiency, and lifespan.

[0088] According to one embodiment, the inorganic light-emitting element (120) can express different brightness grayscale values ​​depending on the magnitude of the driving current provided from the subpixel circuit (110). For example, the inorganic light-emitting element (120) can express brighter grayscale values ​​as the magnitude of the driving current increases.

[0089] According to one embodiment, the subpixel circuit (110) can provide a driving current to an inorganic light-emitting element (120). Specifically, the subpixel circuit (110) can provide a driving current with controlled size and driving time to the inorganic light-emitting element (120) based on an image data voltage applied from the driving unit (500), a driving voltage (e.g., driving voltage, ground voltage), various control signals (e.g., scan signal, emission signal, test signal), various input signals (e.g., sweep signal, reference voltage), etc.

[0090] In particular, the subpixel circuit (110) can drive the inorganic light-emitting element (120) using Pulse Amplitude Modulation (PAM).

[0091] According to one embodiment, the subpixel circuit (110) may include a PAM circuit (111) and a first transistor (112). The subpixel circuit (110) may use the PAM circuit (111) to provide a constant current of a magnitude based on the image data voltage to an inorganic light-emitting element (120). Here, the constant current provided to the inorganic light-emitting element (120) becomes a driving current.

[0092] According to one embodiment, the PAM circuit (111) can provide a driving current (or constant current) to the inorganic light-emitting element (120) based on an image data voltage applied from the driving unit (500). Specifically, the PAM circuit (111) can apply a driving voltage to the inorganic light-emitting element (120) through a driving transistor. Accordingly, a driving current can flow to the inorganic light-emitting element (120).

[0093] According to one embodiment, the magnitude of the driving current can be determined based on the magnitude of the image data voltage applied to the PAM circuit (111). That is, the PAM circuit (111) has the capability to PAM drive the inorganic light-emitting element (120). PAM driving may refer to a driving method that expresses the gradation of an image based on the amplitude of the current applied to the inorganic light-emitting element (120).

[0094] In the light-emitting section, the PAM circuit (111) can apply a driving voltage to the inorganic light-emitting element (120) through the driving transistor. Accordingly, a driving current can flow through the inorganic light-emitting element (120).

[0095] Meanwhile, there may be a deviation among the threshold voltages (Vth) of the driving transistors included in the subpixel circuits of the display panel (100). Theoretically, the threshold voltages (Vth) of the driving transistors should be the same, but in reality, deviations may occur due to various factors such as process variation or changes over time, and since such deviations cause a degradation of image quality, they need to be compensated for.

[0096] Specifically, if the threshold voltage of the driving transistor is not compensated, even if the same image data voltage is applied to the PAM circuit (111) of each subpixel, a driving current of a different magnitude is provided to the inorganic light-emitting element (120) by the deviation of the threshold voltage, and this appears as stains in the image.

[0097] In order to compensate for the threshold voltage difference between driving transistors, according to one embodiment, the PAM circuit (111) can apply a voltage that is the sum of the image data voltage and the threshold voltage of the driving transistor to the gate terminal of the driving transistor when an image data voltage is applied during a data setting interval.

[0098] Subsequently, during the light emission period, the PAM circuit (111) can provide a driving current to the inorganic light-emitting element (120) with a magnitude based on (|Vgs|-|Vth|)^2, which is the square of the voltage obtained by subtracting the threshold voltage of the driving transistor from the voltage between the gate terminal and the source terminal of the driving transistor.

[0099] At this time, since the voltage (VCCG+Vth) which is the sum of the image data voltage (e.g., VCCG) and the threshold voltage of the driving transistor (e.g., Vth) is applied to the gate terminal of the driving transistor during the data setting interval, it can be seen that the threshold voltage of the driving transistor is eliminated by subtracting the threshold voltage of the driving transistor from the voltage between the gate terminal and the source terminal of the driving transistor.

[0100] More specifically, since the driving transistor is a PMOS TFT, = . In this case, since Vsg = Vs - (VCCG + Vth), Vsg + Vth = Vs - (VCCG + Vth) + Vth, it can be seen that the Vth term is eliminated.

[0101] Accordingly, the magnitude of the driving current provided by the PAM circuit (111) is independent of the threshold voltage of the driving transistor, and thus the threshold voltage difference between the driving transistors can be compensated. According to one embodiment, the PAM circuit (111) can be configured to compensate for the threshold voltage difference between the driving transistors as described above.

[0102] According to one embodiment, the gate terminal of the first transistor (112) may be connected to the gate terminal of the driving transistor, and the drain terminal may be connected to the source terminal of the driving transistor. According to one embodiment, the first transistor (112) may be a transistor of a different type from the driving transistor. For example, if the driving transistor is a P-type LTPS (low-temperature polycrystalline silicon), the first transistor (112) may include an N-type oxide TFT (thin film transistor). However, it is not limited thereto, and the first transistor may include a P-type or N-type TFT of a different type from the driving transistor.

[0103] According to one embodiment, heat may be generated in the first transistor (112) as current flows through the first transistor (112). For example, the first transistor (112) may be configured such that the amount of heat generated in the first transistor (112) is large when a large current flows through the first transistor (112) compared to when a relatively small current flows through the first transistor (112).

[0104] According to one embodiment, the display device (1000) can be applied as a single unit to a wearable device, a portable device, a handheld device, and various electronic products or automotive products that require a display.

[0105] In addition, according to another embodiment of the present disclosure, a plurality of display devices can be combined or assembled to form a single display panel. Thus, a single display panel formed by combining a plurality of display devices may be referred to as a "modular display panel." However, the name is not limited thereto. In this case, each display device (1000) becomes a component constituting the modular display panel. The modular display panel can be applied to small display products such as monitors and TVs, or large display products such as digital signage and electronic displays.

[0106] FIG. 6 is a schematic circuit diagram of a subpixel circuit according to one embodiment.

[0107] Referring to FIG. 6, the subpixel circuit (110) may include a PAM circuit (111), a first transistor (112), a second transistor (114), a third transistor (115), a driving transistor (113), and an inorganic light-emitting element (120).

[0108] According to one embodiment, the driving unit (500) can apply an image data voltage, a driving voltage (e.g., driving voltage, GND), and various control signals (e.g., emission signals) to the subpixel circuit (110). Based on the image data voltage, driving voltage, and various control signals applied from the driving unit (500), the subpixel circuit (110) can provide a driving current to the inorganic light-emitting element (120).

[0109] In the present disclosure, an emission signal may be applied to a subpixel circuit (110) to turn on the second transistor (114) and the third transistor (115) during the light-emitting period. The emission signal may be applied to the gate terminals of the second transistor (114) and the third transistor (115).

[0110] According to one embodiment, an emission signal may be applied separately from a gate driver for each row line to drive pixels on a pixel array in a row line unit. During the frame period of an image, the emission signal for the light emission operation may be applied multiple times for each row line.

[0111] In the present disclosure, the driving voltage may refer to a voltage applied to an inorganic light-emitting element (120) during a light-emitting period. Specifically, during a light-emitting period, the PAM circuit (111) may apply a driving voltage to the inorganic light-emitting element (120) through a driving transistor (113). Accordingly, a driving current may flow through the inorganic light-emitting element (120). According to one embodiment, the driving unit (500) may express a gradation by adjusting the magnitude of the driving current flowing through the inorganic light-emitting element (120).

[0112] In the present disclosure, the image data voltage may refer to a voltage applied to a PAM circuit (111) to control the magnitude of the driving current flowing through an inorganic light-emitting element (120). Since the method of controlling the driving current based on the image data voltage has been described above, redundant content is omitted.

[0113] According to one embodiment, the driving unit (500) can apply an image data voltage corresponding to the grayscale value of the image to the PAM circuit (111), thereby allowing a voltage (hereinafter referred to as the first voltage) to be applied to the gate terminal (e.g., node a) of the driving transistor (113).

[0114] According to one embodiment, the first voltage may be determined based on the image data voltage. For example, the first voltage may include a voltage obtained by adding the image data voltage and the threshold voltage of the driving transistor. However, according to an embodiment, if the threshold voltage of the driving transistor is not compensated, the first voltage may include the image data voltage.

[0115] According to one embodiment, the size of the image data voltage may be determined according to the grayscale expressed in the inorganic light-emitting element (120). For example, the size of the image data voltage corresponding to a high grayscale may be relatively smaller than the size of the image data voltage corresponding to a low grayscale. According to one embodiment, when an image data voltage of a size corresponding to a high grayscale is applied to the PAM circuit (111), the first voltage may be relatively smaller than the first voltage when an image data voltage of a size corresponding to a low grayscale is applied to the PAM circuit (111).

[0116] According to one embodiment, the driving transistor (113) can be turned on when the voltage at the gate terminal is lower than the voltage corresponding to the sum of the voltage at the source terminal and the threshold voltage. According to one embodiment, the magnitude of the driving current flowing through the inorganic light-emitting element (120) can be determined based on the magnitude of the first voltage applied to the gate terminal of the driving transistor (113).

[0117] For example, the magnitude of the driving current flowing through the inorganic light-emitting element (120) may be inversely proportional to the magnitude of the first voltage. For example, when the magnitude of the first voltage is small, a large current may flow through the inorganic light-emitting element (120) compared to the driving current flowing when the magnitude of the first voltage is relatively large.

[0118] The gradation of the image can be expressed based on the magnitude of the driving current flowing through the inorganic light-emitting element (120).

[0119] According to one embodiment, the first transistor (112) can be driven based on an image data voltage applied from the driving unit (500). For example, the driving unit (500) can apply an image data voltage to the PAM circuit (111) so that a first voltage is applied to the gate terminal of the first transistor (112). Since the method for determining the first voltage has been described above, redundant details are omitted.

[0120] According to one embodiment, the magnitude of the current flowing through the first transistor (112) can be determined based on the magnitude of the first voltage applied to the gate terminal of the first transistor (112). For example, the magnitude of the current flowing through the first transistor (112) may be proportional to the magnitude of the first voltage. For example, when the magnitude of the first voltage is large, the first transistor (112) may be driven at a high current, and when the magnitude of the first voltage is small, the first transistor (112) may be driven at a low current. Hereinafter, "driving the transistor" may mean that current flows through the transistor.

[0121] However, it is not limited to this, and the first transistor (112) may be configured to have a current of a magnitude inversely proportional to the magnitude of the driving current flowing through the driving transistor (113). For example, if the magnitude of the current flowing through the driving transistor (113) is proportional to the magnitude of the first voltage, the first transistor (112) may be configured to have a current of a magnitude inversely proportional to the magnitude of the first voltage.

[0122] FIG. 7 is a diagram illustrating an example of current flowing through a display panel in a light-emitting section according to one embodiment.

[0123] Referring to FIG. 7, according to one embodiment, a driving current (①) flows through the driving transistor (113) during the light-emitting section, and a current (②) can flow through the first transistor (112).

[0124] Meanwhile, while a driving current (①) flows through the inorganic light-emitting element (120), a heat generation phenomenon may occur due to the driving current. A heat generation phenomenon may refer to a phenomenon in which some of the power is converted into heat when current flows through the element, causing the temperature of the element to rise. The magnitude of the heat generated in the inorganic light-emitting element (120) may be proportional to the magnitude of the driving current (①). That is, when the inorganic light-emitting element (120) is driven at a high level, the magnitude of the heat generated may be greater than the magnitude of the heat generated when it is driven at a low level. Therefore, the magnitude of the heat generated in the inorganic light-emitting element (120) may differ depending on the driving method (e.g., high level driving, low level driving).

[0125] The characteristics of the inorganic light-emitting element (120) may vary depending on the temperature. The characteristics of the element may include, for example, a luminous efficiency or a threshold voltage for turning on the inorganic light-emitting element (120). Accordingly, depending on the temperature of each of the plurality of display panels (100) included in the display device, differences may occur in the characteristics of the corresponding plurality of inorganic light-emitting elements (120).

[0126] Meanwhile, a plurality of inorganic light-emitting elements (120) included in the display device (1000) may operate based on different driving methods depending on the gradation of the image expressed in each element. In this case, the magnitude of heat generated in each of the plurality of inorganic light-emitting elements (120) may differ. In this case, the plurality of inorganic light-emitting elements (120) may be driven at different temperatures. When driven at different temperatures, differences in the characteristics of the inorganic light-emitting elements (120) may occur, and the gradation of the image may not be expressed evenly.

[0127] Accordingly, the subpixel circuit (110) of the present disclosure can equalize the temperature of a plurality of inorganic light-emitting elements (120) through the heat generated by the driving current (①) as well as the heat generated in the first transistor (112) based on the current (②).

[0128] According to one embodiment, the magnitudes of the driving current (①) and the current (②) can be determined based on the image data voltage. For example, the PAM circuit (111) can apply a first voltage to the gate terminals of the driving transistor (113) and the first transistor (112). The first voltage may be a voltage based on the image data voltage.

[0129] For example, the PAM circuit (111) can provide a driving current (①) to an inorganic light-emitting element (120) based on a first voltage applied to the gate terminal of the driving transistor (113) while a driving voltage (VDD) is applied to the source terminal of the driving transistor (113).

[0130] For example, the PAM circuit (111) can cause current (②) to flow through the first transistor based on the first voltage applied to the gate terminal of the first transistor (112) while the driving voltage (VDD) is applied to the drain terminal of the first transistor (112).

[0131] For example, if the image data voltage corresponds to high brightness, the first transistor (112) can be driven at a low current, and the inorganic light-emitting element (120) can be driven at a high current. For example, if the image data voltage corresponds to low brightness, the first transistor can be driven at a high current, and the inorganic light-emitting element (120) can be driven at a low current. The fact that the image data voltage corresponds to high brightness may mean that the magnitude of the image data voltage is relatively small compared to the image data voltage corresponding to low brightness. The magnitudes of the driving current (①) and current (②) according to the magnitude of the image data voltage are explained in detail in FIG. 8.

[0132] FIG. 8 is a graph illustrating an example of a driving current and a current magnitude according to the magnitude of the image data voltage, according to one embodiment.

[0133] In FIG. 8, the vertical axis of the graph represents the amount of current, and the horizontal axis represents the magnitude of the image data voltage. According to one embodiment, the amount of current flowing through the first transistor (112) may be proportional to the magnitude of the image data voltage. Referring to the graph in FIG. 8, it can be seen that the amount of current flowing through the first transistor (112) increases as the magnitude of the image data voltage increases.

[0134] According to one embodiment, the amount of current flowing through the driving transistor (113) may be inversely proportional to the magnitude of the image data voltage. Referring to the graph in FIG. 8, it can be seen that the amount of current flowing through the driving transistor (113) decreases as the magnitude of the image data voltage increases.

[0135] For example, as the magnitude of the image data voltage corresponds to a higher grayscale, the magnitude of the current flowing through the first transistor (112) may decrease, while the magnitude of the current flowing through the driving transistor (113) may increase. In this case, the magnitude of the heat generated in the inorganic light-emitting element (120) may increase, while the magnitude of the heat generated in the first transistor (112) may decrease.

[0136] Meanwhile, as the magnitude of the image data voltage corresponds to a lower grayscale, the magnitude of the current flowing through the first transistor (112) increases, while the magnitude of the current flowing through the driving transistor (113) may decrease. In this case, the magnitude of heat generated in the inorganic light-emitting element (120) decreases, while the magnitude of heat generated in the first transistor (112) may increase.

[0137] That is, the magnitude of heat generated in the first transistor (112) and the inorganic light-emitting element (120) can be kept constant regardless of the gradation. Therefore, the variation in the characteristics of the multiple inorganic light-emitting elements (120) according to temperature can be minimized.

[0138] According to one embodiment, the gate length and / or channel width of the first transistor (112) may be determined based on the amount of heat generated by the inorganic light-emitting element (120). For example, let us assume a case where the driving current is 0.01 mA and the amount of heat generated by the inorganic light-emitting element (120) is 10 mW. In this case, the gate length and / or channel width of the first transistor (1120) may be determined such that when the same amount of current (0.01 mA) flows through the first transistor (1120), the same amount of heat (10 mW) is generated. For example, if the gate length of the first transistor (112) is reduced or the channel width is increased, the amount of heat generated according to the current may increase.

[0139] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs.

[0140] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure pertains.

[0141] According to one embodiment of the present disclosure, a display device may be provided.

[0142] For example, the display device may include a pixel array in which pixels composed of a plurality of inorganic light-emitting elements are arranged in a plurality of row lines, a display panel including sub-pixel circuits corresponding to the inorganic light-emitting elements of the pixel array, and a driving unit for driving the sub-pixel circuits.

[0143] For example, each of the above subpixel circuits may include a driving transistor, a pulse amplitude modulation (PAM) circuit for driving the driving transistor to provide a driving current to a corresponding inorganic light-emitting element based on an image data voltage, and a first transistor having a gate terminal connected to the gate terminal of the driving transistor and a drain terminal connected to the source terminal of the driving transistor.

[0144] For example, the PAM circuit can provide the driving current to the corresponding inorganic light-emitting element based on a first voltage applied to the gate terminal of the driving transistor while a driving voltage (VDD) is applied to the source terminal of the driving transistor.

[0145] For example, the PAM circuit can allow current to flow through the first transistor based on a first voltage applied to the gate terminal of the first transistor while a driving voltage is applied to the drain terminal of the first transistor.

[0146] For example, the first voltage may be a voltage based on the image data voltage.

[0147] For example, if the image data voltage corresponds to high brightness, the first transistor can be driven at a low current.

[0148] For example, if the image data voltage corresponds to low brightness, the first transistor can be driven with a high current.

[0149] For example, each of the above subpixel circuits may include a second transistor, the source terminal of which is connected to the driving voltage, and the drain terminal of which is connected to the source terminal of the driving transistor and the drain terminal of the first transistor.

[0150] For example, each of the above subpixel circuits may further include a third transistor, the source terminal of which is connected to the drain terminal of the driving transistor and the drain terminal of which is connected to the corresponding inorganic light-emitting element.

[0151] For example, each of the second transistor and the third transistor can be turned on based on an emission signal applied to the gate terminal during the light-emitting period.

[0152] For example, the driving unit provides a gate signal to the subpixel circuits in a row line order to drive the subpixel circuits in a row line order, and the gate signal may include a scan signal for applying an image data voltage to the subpixel circuits, and an emission signal for causing inorganic light-emitting elements of the pixel array to emit light based on the applied image data voltage.

[0153] For example, the subpixel circuits are driven in the order of a data setting interval and a plurality of light emission intervals for each row line for one image frame, and the driving unit can provide the scan signal to the subpixel circuits of the corresponding row line during the data setting interval of each row line and apply the emission signal to the subpixel circuits of the corresponding row line during each of the plurality of light emission intervals of each row line.

[0154] For example, the first light-emitting section among the plurality of light-emitting sections is temporally continuous with the data setting section, and each of the plurality of light-emitting sections may have a preset time interval.

[0155] For example, the PAM circuit applies the first voltage to the gate terminal of the driving transistor in each of the plurality of light-emitting sections to provide the driving current to the corresponding inorganic light-emitting element, and the first voltage may be a voltage based on the image data voltage.

[0156] For example, the driving transistor may include a P-type LTPS (low-temperature polycrystalline silicon), and the first transistor may include an N-type oxide TFT (thin film transistor).

[0157] Although various embodiments have been described above, each embodiment is not necessarily implemented individually, and may be combined with at least one other embodiment, either wholly or partially, to be implemented together in a single product.

[0158] The above description is merely an illustrative explanation of the technical concept of the present disclosure, and a person skilled in the art to which the present disclosure belongs may make various modifications and variations within the scope of the essential characteristics of the present disclosure. For example, although the above description describes a case where the subpixel circuit is implemented with PMOS TFTs, a person skilled in the art may make variations such as implementing the subpixel circuit with NMOS TFTs or CMOS TFTs.

[0159] Furthermore, the embodiments according to the present disclosure are intended to illustrate, not limit, the technical concept of the present disclosure, and the scope of the technical concept of the present disclosure is not limited by such embodiments. Accordingly, the scope of protection of the present disclosure should be interpreted by the claims below, and all technical concepts within an equivalent scope should be interpreted as being included within the scope of rights of the present disclosure.

Claims

1. In a display device, A display panel comprising a pixel array in which pixels composed of a plurality of inorganic light-emitting elements are arranged in a plurality of row lines, and sub-pixel circuits corresponding to the inorganic light-emitting elements of the pixel array; and A driving unit for driving the above subpixel circuits; including Each of the above subpixel circuits is, Driving transistor; A pulse amplitude modulation (PAM) circuit for driving the above-mentioned driving transistor to provide a driving current to a corresponding inorganic light-emitting element based on image data voltage; and A display device comprising: a first transistor, the gate terminal of which is connected to the gate terminal of the driving transistor and the drain terminal of which is connected to the source terminal of the driving transistor.

2. In Paragraph 1, The above PAM circuit is, While a driving voltage (VDD) is applied to the source terminal of the driving transistor, the driving current is provided to the corresponding inorganic light-emitting element based on a first voltage applied to the gate terminal of the driving transistor, and While a driving voltage is applied to the drain terminal of the first transistor, current flows through the first transistor based on a first voltage applied to the gate terminal of the first transistor, and A display device in which the first voltage is a voltage based on the image data voltage.

3. In Paragraph 2, When the above image data voltage corresponds to high brightness, the first transistor is driven at a low current, and A display device in which, when the above image data voltage corresponds to low brightness, the first transistor is driven with a high current.

4. In Paragraph 2, Each of the above subpixel circuits is, A second transistor having a source terminal connected to the driving voltage and a drain terminal connected to the source terminal of the driving transistor and the drain terminal of the first transistor; A third transistor further comprising a source terminal connected to the drain terminal of the driving transistor and a drain terminal connected to the corresponding inorganic light-emitting element; A display device in which each of the second transistor and the third transistor is turned on based on an emission signal applied to the gate terminal during a light-emitting period.

5. In Paragraph 4, The above driving unit is, Gate signals are provided to the above subpixel circuits in a row line order to drive the above subpixel circuits in a row line order, and The above gate signal is, A display device comprising a scan signal for applying an image data voltage to the subpixel circuits, and an emission signal for causing inorganic light-emitting elements of the pixel array to emit light based on the applied image data voltage.

6. In Paragraph 5, The above subpixel circuits are driven for one image frame in the order of a data setting section and a plurality of light emission sections for each row line, and The above driving unit is, A display device that provides the scan signal to the subpixel circuits of the corresponding row line during the data setting interval of each row line, and applies the emission signal to the subpixel circuits of the corresponding row line during each of the plurality of light-emitting intervals of each row line.

7. In Paragraph 6, The first light-emitting section among the plurality of light-emitting sections is temporally continuous with the data setting section, and Each of the above plurality of light-emitting sections has a preset time interval, a display device.

8. In Paragraph 6, The above PAM circuit is, In order to provide the driving current to the corresponding inorganic light-emitting element, the first voltage is applied to the gate terminal of the driving transistor in each of the plurality of light-emitting sections, and A display device in which the first voltage is a voltage based on the image data voltage.

9. In Paragraph 1, The above driving transistor includes P-type LTPS (low-temperature polycrystalline silicon), and A display device in which the first transistor comprises an N-type oxide TFT (thin film transistor).

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