Apparatus for generating gamma voltage and display device including the same

Abstract

One embodiment can offset the effects of an unstable pixel power supply voltage by generating or selectively using a gamma voltage according to a gamma reference voltage that is variable to the pixel power supply voltage.

Description

Technology Field

[0001] This embodiment relates to a technology for generating a gamma voltage for outputting image data in a display device. Background Technology

[0002] The display device may include a panel, a gate driver, a data driver, and a timing controller. The data driver receives image data from a data processing device and can convert the image data into an analog signal—e.g., a data voltage—and transmit it to the panel.

[0003] The data driver may include a digital-to-analog converter (DAC) that converts image data into an analog signal. The digital-to-analog converter may output one of a plurality of gamma voltages as an analog signal depending on the image data. The plurality of gamma voltages may each have different fixed magnitudes.

[0004] Meanwhile, multiple pixels included in the panel can receive power to drive them. However, resistance caused by the power supply wiring can drop the voltage supplied to the pixels. Each pixel may not receive uniform power, and consequently, it may not emit light at the desired brightness. Brightness variations may occur for each pixel.

[0005] Multiple gamma voltages with a fixed magnitude do not contribute to improving luminance deviations caused by wiring resistance. In situations where the power supplied to the pixel varies, if multiple gamma voltages or the gamma reference voltage used to generate them remain fixed to compensate for fluctuating power, the pixel is not driven by the target analog voltage and cannot emit light at the target luminance.

[0006] In addition, unstable power supply to pixels can exacerbate flicker, wave noise, and degradation in terms of image quality. Furthermore, frequent power fluctuations can increase power consumption.

[0007] In this regard, the present embodiment aims to provide a technique for generating a corrected gamma voltage to offset instability in the driving voltage of a pixel. The problem to be solved

[0008] Against this backdrop, one objective of the present embodiment is to provide a technology that selectively provides a gamma voltage of a fixed size or a variable gamma voltage (depending on the pixel power supply voltage) to a fixed size gamma voltage or pixel power supply voltage.

[0009] Another objective of the present embodiment is to provide a technology that receives a pixel power supply voltage, generates a gamma reference voltage dependent on the pixel power supply voltage, and generates a plurality of gamma voltages dependent on the pixel power supply voltage from the gamma reference voltage. means of solving the problem

[0010] To achieve the aforementioned objective, one embodiment provides a gamma voltage generating device for generating a gamma voltage of a grayscale value corresponding to image data for displaying image data, comprising: a first voltage generating unit for generating a first gamma reference voltage having a fixed size; a second voltage generating unit for generating a second gamma reference voltage that varies according to a pixel power supply voltage that supplies power to a pixel; a selection unit for selecting the first gamma reference voltage or the second gamma reference voltage; and a gamma voltage generating unit for generating the gamma voltage from the selected gamma reference voltage.

[0011] In the above device, the gamma voltage generating unit can generate the gamma voltage from a first gamma reference voltage comprising a plurality of gamma reference voltages having a fixed size.

[0012] In the above device, the gamma voltage generating unit receives a maximum voltage and a minimum voltage, generates the gamma voltage by distributing the voltage difference between the maximum voltage and the minimum voltage, and the first gamma reference voltage can be input to the gamma voltage generating unit as the maximum voltage and the minimum voltage.

[0013] In the above device, the gamma voltage generating unit can generate the gamma voltage from a second gamma reference voltage comprising a plurality of gamma reference voltages that vary according to the pixel power supply voltage.

[0014] In the above device, the gamma voltage generating unit receives a maximum voltage and a minimum voltage, generates the gamma voltage by distributing the voltage difference between the maximum voltage and the minimum voltage, and the second gamma reference voltage can be input to the gamma voltage generating unit as the maximum voltage and the minimum voltage.

[0015] Another embodiment provides a gamma voltage generating device for generating a gamma voltage of a grayscale value corresponding to image data for displaying image data, comprising: a voltage generating unit that generates a gamma reference voltage that varies according to a pixel power supply voltage that supplies power to a pixel; and a gamma voltage generating unit that generates the gamma voltage from the gamma reference voltage, wherein the voltage generating unit receives the pixel power supply voltage and generates a first gamma reference voltage and a second gamma reference voltage, and the gamma voltage generating unit receives the first gamma reference voltage as the highest voltage and receives the second gamma reference voltage as the lowest voltage, and generates the gamma voltage from the voltage difference between the first gamma reference voltage and the second gamma reference voltage.

[0016] In the above device, the voltage generation unit receives a reference voltage and can generate a first gamma reference voltage or a second gamma reference voltage by reflecting the pixel power supply voltage to the reference voltage.

[0017] In the above device, the voltage generation unit can generate the first gamma reference voltage from the sum of the one reference voltage and the pixel power supply voltage.

[0018] In the above device, the voltage generating unit includes a first gamma reference voltage circuit that generates the first gamma reference voltage, and the first gamma reference voltage circuit may include a first amplifier that receives the first reference voltage and the pixel power supply voltage through one input terminal.

[0019] In the above device, the voltage generation unit receives another reference voltage and can generate the second gamma reference voltage from the difference between the other reference voltage and the pixel power supply voltage.

[0020] In the above device, the voltage generating unit includes a second gamma reference voltage circuit that generates the second gamma reference voltage, and the second gamma reference voltage circuit may include a second amplifier that receives the other reference voltage through one input terminal and receives the pixel power supply voltage through another input terminal.

[0021] In the above device, the second gamma reference voltage circuit may include a differential amplifier.Another embodiment is a gamma voltage generating device for generating a gamma voltage (Vg1-Vgn) of a grayscale value corresponding to the image data for displaying image data, comprising: a first voltage generating unit (510) for generating a first gamma reference voltage (Vgref11, Vgref12) having a fixed magnitude regardless of a first pixel power voltage (ELVDD) among pixel power voltages that supply power to a pixel; a second voltage generating unit (520) for generating a second gamma reference voltage (Vgref21, Vgref22) that varies according to the first pixel power voltage (ELVDD); and a selection unit (530) for selecting either the first gamma reference voltage or the second gamma reference voltage, and outputting a top voltage (Vtop) and a bottom voltage (Vbot) for generating the gamma voltage (Vg1-Vgn) based on the selected gamma reference voltage. and includes a gamma voltage generation unit (540) that generates the gamma voltage (Vg1-Vgn) based on the uppermost voltage (Vtop) and the lowermost voltage (Vbot), and the second voltage generation unit (520) includes a first voltage correction unit (521) that receives a first reference voltage (Vref1) and generates a second-1 gamma reference voltage (Vgref21) among the second gamma reference voltages to be input as the uppermost voltage (Vtop) based on the first reference voltage (Vref1) and the first pixel power supply voltage (ELVDD), and a second voltage correction unit (522) that receives a second reference voltage (Vref2) and generates a second-2 gamma reference voltage (Vgref22) among the second gamma reference voltages to be input as the lowermost voltage (Vbot) based on the second reference voltage (Vref2) and the first pixel power supply voltage (ELVDD), and the first voltage correction unit (521) The second-1 gamma reference voltage (Vgref21) is independently generated, the second voltage correction unit (522) independently generates the second-2 gamma reference voltage (Vgref22), and the selection unit (530) can select either the first gamma reference voltage (Vgref11, Vgref12) and the second gamma reference voltage (Vgref21, Vgref2).At this time, the gamma voltage generation unit (540) can receive the top voltage (Vtop) and the bottom voltage (Vbot) from the selection unit (530), and generate the gamma voltage (Vg1-Vgn) by distributing the voltage difference between the top voltage (Vtop) and the bottom voltage (Vbot). Furthermore, the first voltage correction unit (521) can generate the second-1 gamma reference voltage (Vgref21) from the sum of the first reference voltage (Vref1) and the first pixel power supply voltage (ELVDD), and the second voltage correction unit (522) can generate the second-2 gamma reference voltage (Vgref22) from the difference between the second reference voltage (Vref2) and the first pixel power supply voltage (ELVDD). Additionally, the first voltage correction unit (521) can generate the first reference voltage (Vref1) and the first It may include a first amplifier that receives a pixel power supply voltage (ELVDD). The second voltage correction unit (522) may include a second amplifier that receives the second reference voltage (Vref2) through one input terminal and receives the first pixel power supply voltage (ELVDD) through another input terminal. Additionally, the second voltage correction unit (522) may include a differential amplifier. Effects of the invention

[0022] As explained above, according to the present embodiment, the gamma voltage is generated or selectively used according to a gamma reference voltage that is variable to the pixel power supply voltage, thereby offsetting the effect of the unstable pixel power supply voltage.

[0023] And according to the present embodiment, the effect of unstable pixel power supply voltage is offset, so the possibility of flicker, wave noise, and degradation is reduced and image quality can be improved. Brief explanation of the drawing

[0024] FIG. 1 is a configuration diagram of a display device according to one embodiment. FIG. 2 is a circuit diagram showing the structure of a pixel and signals input to and output to the pixel according to one embodiment. Figure 3 is a configuration diagram of the gamma voltage generator of the data driving device. Figure 4 is a circuit diagram of the gamma voltage generation section of the gamma voltage generation device. FIG. 5 is a configuration diagram of a gamma voltage generating device of a data driving device according to one embodiment. Specific details for implementing the invention

[0025] Hereinafter, some embodiments of the present invention will be described in detail with reference to the exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions could obscure the essence of the invention, such detailed description is omitted.

[0026] In addition, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the present invention. These terms are intended only to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms. Where it is stated that a component is "connected," "combined," or "connected" to another component, it should be understood that the component may be directly connected or connected to the other component, but that another component may also be "connected," "combined," or "connected" between each component.

[0027] FIG. 1 is a configuration diagram of a display device according to one embodiment.

[0028] Referring to FIG. 1, the display device (100) may include a panel (110), a data driving device (120), a gate driving device (130), and a data processing device (140), etc.

[0029] A plurality of data lines (DL) and a plurality of gate lines (GL) may be arranged on the panel (110), and a plurality of pixels (P) may be arranged. A pixel (P) may be composed of a plurality of sub-pixels. Here, the sub-pixels may be R (red), G (green), B (blue), W (white), etc. A single pixel (P) may be composed of RGB sub-pixels, RGBG sub-pixels, RGBW sub-pixels, etc. For convenience of explanation, in the following description, a single pixel (P) is composed of RGB sub-pixels, and various signals are applied to the pixel (P) without distinction of sub-pixels.

[0030] The data driving device (120), the gate driving device (130), and the data processing device (140) are devices that generate signals for displaying images on the panel (110).

[0031] The gate driving device (130) can supply a gate driving signal of a turn-on voltage or a turn-off voltage to the gate line (GL). When the gate driving signal of the turn-on voltage is supplied to the pixel (P), the pixel (P) is connected to the data line (DL). Then, when the gate driving signal of the turn-off voltage is supplied to the pixel (P), the connection between the pixel (P) and the data line (DL) is released. The gate driving device (130) may be referred to as a gate driver.

[0032] The data driving device (120) can supply a data voltage (Vdata) to a pixel (P) through a data line (DL). The data voltage (Vdata) supplied through the data line (DL) can be supplied to the pixel (P) according to a gate driving signal. The data driving device (120) may be referred to as a source driver.

[0033] The data driving device (120) can generate a plurality of gamma voltages and output a data voltage (Vdata) corresponding to image data (RGB) among the plurality of gamma voltages. The data driving device (120) may include a digital-to-analog converter and a buffer. The digital-to-analog converter can select one voltage among the plurality of gamma voltages in response to the image data (RGB) and output the selected voltage to a buffer. The buffer can amplify the selected voltage and apply the data voltage (Vdata) to a pixel (P) through a data line (DL).

[0034] The data driving device (120) may include at least one integrated circuit, which may be connected to a bonding pad of the panel (110) in a Tape Automated Bonding (TAB) type or Chip On Glass (COG) type, or may be formed directly on the panel (110), and, depending on the embodiment, may be formed by being integrated on the panel (110). Additionally, the data driving device (120) may be implemented in a Chip On Film (COF) type.

[0035] The data processing device (140) can supply control signals to the gate driving device (130) and the data driving device (120). For example, the data processing device (140) can transmit a gate control signal (GCS) to the gate driving device (130) to start scanning. Also, the data processing device (140) can output image data to the data driving device (120). Additionally, the data processing device (140) can transmit a data control signal (DCS) to control the data driving device (120) to supply a data voltage (Vdata) to each pixel (P). The data processing device (140) may be referred to as a timing controller.

[0036] The power management device (150) can supply power to the panel (110), the data driving device (120), the gate driving device (130), and the data processing device (140). The power management device (150) can generate and supply a voltage of the size required by each circuit, including a DC-DC converter.

[0037] In particular, the power management device (150) can drive the pixel (P) by supplying a pixel power voltage (ELVDD, ELVSS) to the pixel (P) of the panel (110). The pixel power voltage (ELVDD, ELVSS) may include a first pixel power voltage (ELVDD) and a second pixel power voltage (ELVSS) that is lower than the first.

[0038] The first pixel power supply voltage (ELVDD) can also be transmitted to the data driving device (120). The pixel power supply voltage (ELVDD, ELVSS) is supplied to the pixel (P) through the power line (PL), and as the distance between the power management device (150) and the pixel (P) increases, the wiring resistance of the power line (PL) may increase. An increase in wiring resistance may lower the pixel power supply voltage (ELVDD, ELVSS) applied to the pixel (P). The degree of voltage drop may increase as the distance between the power management device (150) and the pixel (P) increases. In particular, the first pixel power supply voltage (ELVDD) among the pixel power supply voltages (ELVDD, ELVSS) may be affected. Therefore, the data driving device (120) can receive the first pixel power supply voltage (ELVDD) from the pixel (P) terminal and generate a corrected gamma voltage to offset the voltage drop of the first pixel power supply voltage (ELVDD) caused by the wiring resistance.

[0039] FIG. 2 is a circuit diagram showing the structure of a pixel and signals input to and output to the pixel according to one embodiment.

[0040] Referring to FIG. 2, the pixel (P) may include an organic light-emitting diode (OLED), a driving transistor (DRT), a switching transistor (SWT), and a storage capacitor (Cstg), etc. When pixel power supply voltages (ELVDD, ELVSS) are applied to the pixel (P), the first pixel power supply voltage (ELVDD) may be applied in the direction of the anode electrode of the organic light-emitting diode, and the second pixel power supply voltage (ELVSS) may be applied in the direction of the cathode electrode of the organic light-emitting diode.

[0041] An organic light-emitting diode can be composed of an anode electrode, an organic layer, a cathode electrode, etc. Under the control of a driving transistor (DRT), the anode electrode is connected to the first pixel power supply voltage (ELVDD) and the cathode electrode is connected to the base voltage, i.e., the second pixel power supply voltage (ELVSS), thereby emitting light.

[0042] The driving transistor (DRT) can control the brightness of the organic light-emitting diode by controlling the driving current (Ioled) supplied to the organic light-emitting diode. Since the pixel power supply voltage (ELVDD, ELVSS) has a periodic wave with a constant pulse, the driving current (Ioled) can also have a periodic wave.

[0043] The first node (N1) of the driving transistor (DRT) can be electrically connected to the anode electrode of the organic light-emitting diode and may be a source node or a drain node. The second node (N2) of the driving transistor (DRT) can be electrically connected to the source node or a drain node of the switching transistor (SWT) and may be a gate node. The third node (N3) of the driving transistor (DRT) can be electrically connected to a power line (PL) that supplies the first pixel power supply voltage (ELVDD) and may be a drain node or a source node.

[0044] The switching transistor (SWT) is electrically connected between the data line (DL) and the second node (N2) of the driving transistor (DRT), and can be turned on by receiving a scan signal through the gate line (GL).

[0045] When this switching transistor (SWT) is turned on, the data voltage (Vdata) supplied from the data driving circuit (120) is transmitted to the second node (N2) of the driving transistor (DRT) through the data line (DL).

[0046] The storage capacitor (Cstg) can be electrically connected between the second node (N2) and the third node (N3) of the driving transistor (DRT).

[0047] The storage capacitor (Cstg) may be a parasitic capacitor existing between the second node (N2) and the third node (N3) of the driving transistor (DRT), or it may be an external capacitor intentionally designed outside the driving transistor (DRT).

[0048] FIG. 3 is a configuration diagram of a gamma voltage generator of a data driving device, and FIG. 4 is a circuit diagram of a gamma voltage generation unit of a gamma voltage generator.

[0049] Referring to FIG. 3, the gamma voltage generating device (1) may include a voltage generating unit (10) and a gamma voltage generating unit (20).

[0050] The voltage generation unit (10) can generate two or more gamma reference voltages, namely a top voltage (Vtop) and a bottom voltage (Vbot), to generate gamma voltages (Vg1~Vgn) and transmit them to the gamma voltage generation unit (20). Here, the top voltage (Vtop) may be larger than the bottom voltage (Vbot), and both the top voltage (Vtop) and the bottom voltage (Vbot) may have a fixed size.

[0051] The gamma voltage generation unit (20) can generate gamma voltages (Vg1~Vgn). The gamma voltage generation unit (20) receives a top voltage (Vtop) and a bottom voltage (Vbot), and can generate gamma voltages (Vg1~Vgn) by voltage distribution of the voltage difference between the top voltage (Vtop) and the bottom voltage (Vbot). The gamma voltage generation unit (20) includes a series of resistor arrays connected in series, and the series of resistor arrays can distribute a voltage corresponding to the difference between the top voltage (Vtop) and the bottom voltage (Vbot). The series of resistor arrays may be named a voltage divider. Multiple resistors constituting the series of resistor arrays form nodes at points where they are connected to each other, and each gamma voltage (Vg1~Vgn) can be formed at the node. Since a node is formed at every point where the multiple resistors are connected to each other, the gamma voltages (Vg1~Vgn) can include multiple voltages.

[0052] The data driving device can select one voltage among the gamma voltages (Vg1~Vgn) and amplify the selected voltage to output a data voltage.

[0053] Referring to FIG. 4, as an example, the gamma voltage generating unit (20) may have a circuit including a resistor string that generates 16 gamma voltages (Vg1 to Vg16).

[0054] The gamma voltage generating unit (20) may include a resistance string (21). The resistance string (21) may include a plurality of resistors connected in series. Additionally, the resistance string (21) may include a node formed by connecting the plurality of resistors between the highest voltage (Vtop) and the lowest voltage (Vbot). The node may include a point where the resistors are connected, the end of the resistor to which the highest voltage (Vtop) is applied, or the end of the resistor to which the lowest voltage (Vbot) is applied. In this drawing, the resistance value included in the gamma voltage generating unit (20) may be represented as R.

[0055] The resistance string (21) can form a node voltage at each node by distributing the voltage difference between the highest voltage (Vtop) and the lowest voltage (Vbot) into a plurality of resistors in series. The plurality of node voltages (V1~V16) generated at 16 nodes can be output as 16 gamma voltages (Vg1~Vg16).

[0056] FIG. 5 is a configuration diagram of a gamma voltage generating device of a data driving device according to one embodiment.

[0057] Referring to FIG. 5, a gamma voltage generating device (500) according to one embodiment may include a first voltage generating unit (510), a second voltage generating unit (520), a selection unit (530), and a gamma voltage generating unit (540).

[0058] The gamma voltage generating device (500) can generate a gamma voltage of a grayscale value corresponding to the image data in order to display the image data. The gamma voltage generating device (500) can generate gamma voltages (Vg1~Vgn) using a first gamma reference voltage (Vgref11, Vgref12) having a fixed size regardless of the pixel power supply voltage (ELVDD, ELVSS), or can generate gamma voltages (Vg1~Vgn) using a second gamma reference voltage (Vgref21, Vgref22) having a size linked to the pixel power supply voltage (ELVDD, ELVSS). That is, the gamma voltage generating device (500) can generate gamma voltages (Vg1~Vgn) by selectively using the first gamma reference voltage (Vgref11, Vgref12) or the second gamma reference voltage (Vgref21, Vgref22).

[0059] In this drawing, the gamma voltage generating device (500) is described as an example of generating a second gamma reference voltage (Vgref21, Vgref22) linked to the first pixel power voltage (ELVDD) among the pixel power voltages (ELVDD, ELVSS).

[0060] The first voltage generation unit (510) can generate a first gamma reference voltage (Vgref11, Vgref12) having a fixed voltage magnitude. The first gamma reference voltage (Vgref11, Vgref12) may include a first-1 gamma reference voltage (Vgref11) and a first-2 gamma reference voltage (Vgref12). When the selection unit (530) selects the first gamma reference voltage (Vgref11, Vgref12), the first-1 gamma reference voltage (Vgref11) may be input as the top voltage (Vtop) of the gamma voltage generation unit (540), and the first-2 gamma reference voltage (Vgref12) may be input as the bottom voltage (Vbot) of the gamma voltage generation unit (540).

[0061] The second voltage generation unit (520) can generate a second gamma reference voltage (Vgref21, Vgref22) having a different magnitude depending on the first pixel power supply voltage (ELVDD). The second gamma reference voltage (Vgref21, Vgref22) may include a second-1 gamma reference voltage (Vgref21) and a second-2 gamma reference voltage (Vgref22). When the selection unit (530) selects the second gamma reference voltage (Vgref21, Vgref22), the second-1 gamma reference voltage (Vgref21) may be input as the top voltage (Vtop) of the gamma voltage generation unit (540), and the second-2 gamma reference voltage (Vgref22) may be input as the bottom voltage (Vbot) of the gamma voltage generation unit (540).

[0062] In order to generate a second gamma reference voltage (Vgref21, Vgref22) that is dynamic (variable) according to the first pixel power supply voltage (ELVDD), the second voltage generation unit (520) can reflect the first pixel power supply voltage (ELVDD).

[0063] Specifically, the second voltage generation unit (520) receives the first reference voltage (Vref1) and the second reference voltage (Vref2), and can generate the second-1 gamma reference voltage (Vgref21) or the second-2 gamma reference voltage (Vgref22) by reflecting the first pixel power supply voltage (ELVDD) in the received reference voltages (Vref1, Vref2).

[0064] The second voltage generation unit (520) can generate a second-1 gamma reference voltage (Vgref21) by adding the first pixel power supply voltage (ELVDD) to the first reference voltage (Vref1). The second voltage generation unit (520) may include a first gamma reference voltage circuit for generating the second-1 gamma reference voltage (Vgref21). The first gamma reference voltage circuit may include an amplifier that receives the first reference voltage (Vref1) and the first pixel power supply voltage (ELVDD) through one input terminal.

[0065] Additionally, the second voltage generation unit (520) can generate a second-2 gamma reference voltage (Vgref22) by subtracting the second reference voltage (Vref2) from the first pixel power supply voltage (ELVDD). The second voltage generation unit (520) may include a second gamma reference voltage circuit for generating the second-2 gamma reference voltage (Vgref22). The second gamma reference voltage circuit may include an amplifier that receives the second reference voltage (Vref2) through one input terminal and receives the first pixel power supply voltage (ELVDD) through another input terminal. Here, the amplifier included in the second gamma reference voltage circuit may be a differential amplifier.

[0066] The second voltage generation unit (520) may include a first voltage correction unit (521) and a second voltage correction unit (522) that independently generate a second-1 gamma reference voltage (Vgref21) and a second-2 gamma reference voltage (Vgref22).

[0067] The first voltage correction unit (521) receives the first pixel power supply voltage (ELVDD) and can generate a second-1 gamma reference voltage (Vgref21) that varies according to the received pixel power supply voltage (ELVDD). Therefore, the first voltage correction unit (521) may be a first gamma reference voltage circuit. The first voltage correction unit (521) can generate a second-1 gamma reference voltage (Vgref21) that reflects the first pixel power supply voltage (ELVDD), and as the first pixel power supply voltage (ELVDD) becomes fluid due to the wiring resistance, the second-1 gamma reference voltage (Vgref21) may also become fluid. The second-1 gamma reference voltage (Vgref21) can be input as the top voltage (Vtop) of the gamma voltage generation unit (540).

[0068] The second voltage correction unit (522) receives the first pixel power supply voltage (ELVDD) and can generate a second-2 gamma reference voltage (Vgref22) that varies according to the received pixel power supply voltage (ELVDD). Therefore, the second voltage correction unit (522) may be a second gamma reference voltage circuit. The second voltage correction unit (522) can generate a second-2 gamma reference voltage (Vgref22) that reflects the first pixel power supply voltage (ELVDD), and as the first pixel power supply voltage (ELVDD) becomes variable due to the wiring resistance, the second-2 gamma reference voltage (Vgref22) may also become variable. The second-2 gamma reference voltage (Vgref22) can be input as the lowest voltage (Vbot) of the gamma voltage generation unit (540).

[0069] The selection unit (530) can select either the first gamma reference voltage (Vgref11, Vgref12) and the second gamma reference voltage (Vgref21, Vgref22). The selection unit (530) can transmit the selected gamma reference voltage to the gamma voltage generation unit (540) as the top voltage (Vtop) and the bottom voltage (Vbot).

[0070] The gamma voltage generation unit (540) receives the gamma reference voltage selected by the selection unit (530) as the top voltage (Vtop) and the bottom voltage (Vbot), and can generate multiple gamma voltages (Vg1~Vgn). The gamma voltage generation unit (540) can generate multiple voltages having different magnitudes by distributing the voltage difference of the selected gamma reference voltage.

[0071] For example, the gamma voltage generating unit (540) can generate multiple gamma voltages (Vg1~Vgn) by distributing the voltage difference between the first-1 gamma reference voltage (Vgref11) and the first-2 gamma reference voltage (Vgref12), or generate multiple gamma voltages (Vg1~Vgn) by distributing the voltage difference between the second-1 gamma reference voltage (Vgref21) and the second-2 gamma reference voltage (Vgref22).

[0072] According to an embodiment of the present invention, when the first pixel power supply voltage (ELVDD) changes dynamically, the second voltage generation unit (520) does not correct the gamma voltage by reflecting the deviation of the first pixel power supply voltage (ELVDD), but rather receives the first pixel power supply voltage (ELVDD) as is and generates a gamma reference voltage (Vgref21, Vgref22) that is immediately corrected according to the movement of the first pixel power supply voltage (ELVDD). Since the movement is reflected in real time, more accurate gamma reference voltage correction can be achieved.

[0073] In addition, the gamma voltage is generated or selectively used according to a variable gamma reference voltage in the pixel power supply voltage, thereby offsetting the effects of the unstable pixel power supply voltage.

[0074] In addition, the effects of unstable pixel power supply voltage are offset, reducing the possibility of flicker, wave noise, and degradation, and improving image quality.

Claims

Claim 1 A gamma voltage generating device for generating a gamma voltage of a grayscale value corresponding to the image data for displaying image data, comprising: a first voltage generating unit (510) for generating a first gamma reference voltage (Vgref11, Vgref12) having a fixed magnitude regardless of a first pixel power voltage (ELVDD) among pixel power voltages that supply power to a pixel; a second voltage generating unit (520) for generating a second gamma reference voltage (Vgref21, Vgref22) that varies according to the first pixel power voltage (ELVDD); and a selection unit (530) for selecting either the first gamma reference voltage or the second gamma reference voltage, and outputting a top voltage (Vtop) and a bottom voltage (Vbot) for generating the gamma voltage based on the selected gamma reference voltage. The apparatus includes a gamma voltage generation unit (540) that generates the gamma voltage (Vg1-Vgn) based on the uppermost voltage (Vtop) and the lowermost voltage (Vbot), and the second voltage generation unit (520) includes a first voltage correction unit (521) that receives a first reference voltage (Vref1) and generates a second-1 gamma reference voltage (Vgref21) among the second gamma reference voltages to be input as the uppermost voltage (Vtop) based on the first reference voltage (Vref1) and the first pixel power supply voltage (ELVDD), and a second voltage correction unit (522) that receives a second reference voltage (Vref2) and generates a second-2 gamma reference voltage (Vgref22) among the second gamma reference voltages to be input as the lowermost voltage (Vbot) based on the second reference voltage (Vref2) and the first pixel power supply voltage (ELVDD), and the first voltage correction unit (521) A gamma voltage generating device that independently generates a second-1 gamma reference voltage (Vgref21), the second voltage correction unit (522) independently generates the second-2 gamma reference voltage (Vgref22), and the selection unit (530) selects one of the first gamma reference voltage (Vgref11, Vgref12) and the second gamma reference voltage (Vgref21, Vgref22). Claim 2 In claim 1, the gamma voltage generating unit (540) receives the highest voltage (Vtop) and the lowest voltage (Vbot) from the selection unit (530), and generates the gamma voltage (Vg1-Vgn) by distributing the voltage difference between the highest voltage (Vtop) and the lowest voltage (Vbot). Claim 3 A gamma voltage generating device according to claim 1, wherein the first voltage correction unit (521) generates the second-1 gamma reference voltage (Vgref21) from the sum of the first reference voltage (Vref1) and the first pixel power supply voltage (ELVDD), and the second voltage correction unit (522) generates the second-2 gamma reference voltage (Vgref22) from the difference between the second reference voltage (Vref2) and the first pixel power supply voltage (ELVDD). Claim 4 In paragraph 3, the first voltage correction unit (521) is a gamma voltage generating device comprising a first amplifier that receives the first reference voltage (Vref1) and the first pixel power supply voltage (ELVDD) through one input terminal. Claim 5 In paragraph 4, the second voltage correction unit (522) is a gamma voltage generating device comprising a second amplifier that receives the second reference voltage (Vref2) through one input terminal and receives the first pixel power supply voltage (ELVDD) through another input terminal. Claim 6 In paragraph 5, the second voltage correction unit (522) is a gamma voltage generating device including a differential amplifier.

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