KR20200093940A - Display - Google Patents

Abstract

Embodiments of the present invention discloses a data driving circuit and a display device including the same. The display device according to one embodiment of the present invention includes: a pixel portion including pixels; and a data driving portion converting n-bit first image data into m-bit (a natural number of m> n) second image data and generating a data signal based on a gamma voltage corresponding to the second image data to output the first image data to the pixel, thereby simply adjusting brightness using the gamma voltage.

Description

Display device{Display}

The present embodiments relate to a data driving circuit and a display device including the same.

As the information society develops, the demand for a display device for displaying images is increasing, and a liquid crystal display device, a plasma display device, and an organic light emitting display device Various types of display devices, such as, are used. Recently, interest in a display device using a micro light emitting diode (μLED) (hereinafter referred to as a “micro display device”) is also increasing.

As excellent display device characteristics are required for VR (Virtual Reality), AR (Augmented Reality), and MR (Mixed Reality) technologies, the development of micro LED on Silicon or AMOLED on Silicon is increasing, especially pixel size for high resolution implementation. The demand for minimization is increasing.

Embodiments of the present invention simply provide a display device that can adjust the brightness using a gamma voltage.

A display device according to an exemplary embodiment of the present invention includes a pixel unit including a pixel; And converting n-bit first image data into m-bit (m>n natural number) second image data, generating a data signal based on a gamma voltage corresponding to the second image data, and outputting the data to the pixel. And a data driver. The data driver includes a relationship between first control data corresponding to characteristic data of the driving transistor of the pixel among 2 ⁿ gradation levels and second control data corresponding to characteristic data of the driving transistor among 2 ^m gradation levels. Based on the, the first image data is converted to the second image data.

The characteristic data of the driving transistor may include a voltage corresponding to a boundary point separating an operation region of the driving transistor.

The characteristic data of the driving transistor may include a threshold voltage of the driving transistor.

The data driver may adjust the gamma graph using the characteristic data of the driving transistor.

The first control data may vary according to the set brightness.

Embodiments of the present invention can provide a display device capable of simply adjusting brightness using a gamma voltage by adjusting a gamma graph using characteristic data of a driving transistor.

1 is a view schematically showing a manufacturing process of a display device according to an exemplary embodiment of the present invention.
2 is a view schematically showing a display device according to an exemplary embodiment of the present invention.
3 is an example of a pixel of the display device illustrated in FIG. 2.
4 is a diagram schematically showing a data driver according to an embodiment of the present invention.
5 is a view for explaining gamma voltage generation of a gamma voltage generation unit according to an embodiment of the present invention.
6 is a diagram illustrating bit conversion of input data using a lookup table according to an embodiment of the present invention.
7 to 9 are diagrams illustrating bit conversion of input data according to an embodiment of the present invention.

The present invention can be applied to various transformations and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description. Effects and features of the present invention and methods for achieving them will be clarified with reference to embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals when describing with reference to the drawings, and redundant description thereof will be omitted. .

In the following examples, terms such as first and second are not used in a limiting sense, but for the purpose of distinguishing one component from other components. In addition, in the following embodiments, the singular expression includes a plural expression unless the context clearly indicates otherwise.

In the following embodiments, when X and Y are connected, X and Y are electrically connected, X and Y are functionally connected, and X and Y are directly connected. Can. Here, X, Y may be an object (for example, a device, an element, a circuit, a wiring, an electrode, a terminal, a conductive film, a layer, etc.). Therefore, it is not limited to a predetermined connection relationship, for example, the connection relationship shown in the drawings or detailed description, and may include other than the connection relationship shown in the drawings or detailed description.

When X and Y are electrically connected, for example, an element (eg, switch, transistor, capacitive element, inductor, resistance element, diode, etc.) that enables electrical connection between X and Y, It may include a case where one or more are connected between X and Y.

When X and Y are functionally connected, a circuit that enables functional connection of X and Y, such as when the signal output from X is transmitted to Y (for example, a logic circuit (OR gate, inverter, etc.)) , Signal conversion circuit (AD conversion circuit, gamma correction circuit, etc.), potential level conversion circuit (level shifter circuit, etc.), current supply circuit, amplification circuit (circuit that can increase the signal amplitude or current amount, etc.), signal generation circuit, It may include a case where one or more memory circuits (such as a memory) are connected between X and Y.

In the following embodiments, “ON” used in connection with the device state refers to the activated state of the device, and “OFF” refers to the deactivated state of the device. “On” used in connection with a signal received by the device may refer to a signal that activates the device, and “off” may refer to a signal that deactivates the device. The device can be activated by a high voltage or a low voltage. For example, a P-type transistor is activated by a low voltage, and an N-type transistor is activated by a high voltage. Therefore, it should be understood that the "on" voltages for the P-type transistor and the N-type transistor are opposite (low to high) voltage levels.

In the examples below, terms such as include or have are meant to mean that features or components described in the specification exist, and do not preclude the possibility of adding one or more other features or components.

1 is a view schematically showing a manufacturing process of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the display device 30 according to an exemplary embodiment may include a light emitting element array 10 and a driving circuit board 20. The light emitting element array 10 may be coupled to the driving circuit board 20. The display device 30 may be a micro display device.

The light emitting device array 10 may include a plurality of light emitting devices. The light emitting device may be a light emitting diode (LED). The light emitting device may be a micro light emitting diode (LED). The light emitting device may be a light emitting diode (LED) having a size of micro to nano units. At least one light emitting device array 10 may be manufactured by growing a plurality of light emitting diodes on a semiconductor wafer SW. Therefore, the display device 30 can be manufactured by combining the light emitting element array 10 with the driving circuit board 20 without having to separately transfer the light emitting diodes to the driving circuit board 20.

The driving circuit board 20 may be a Si-CMOS substrate in which pixel circuits corresponding to each of the light emitting diodes on the light emitting element array 10 and independently controlling the light emitting diodes are arranged. The pixel circuit may include at least one transistor and at least one capacitor.

Micro light-emitting diodes require a high processing temperature of 1000°C or higher, and cannot be directly grown and patterned on the transistors of the driving circuit board 20. According to an exemplary embodiment of the present invention, a pixel circuit array on the light emitting element array 10 and the driving circuit board 20 is formed and then combined, so that the light emitting diode of the light emitting element array 10 and the pixel circuit of the driving circuit board 20 are formed. May be electrically connected to form a pixel PX. At this time, it is important to accurately arrange the pixel circuit array and the LED array.

2 is a view schematically showing a display device according to an exemplary embodiment of the present invention. Referring to FIG. 2, the display device 30 may include a pixel unit 110 and a driver 120.

The pixel unit 110 may display an image using m-bit digital image data capable of displaying 1 to 2 ^m gradation levels. The pixel unit 110 may be disposed in a display area displaying an image. The pixel unit 110 may include a plurality of pixels PX arranged in various patterns such as a predetermined pattern, for example, a matrix type or a zigzag type. The pixel PX emits one color, and for example, one of red, blue, green, and white colors. The pixel PX may emit colors other than red, blue, green, and white.

The pixel PX may include a light emitting device. The light emitting device may be a self light emitting device. For example, the light emitting device may be an inorganic light emitting diode (LED). The light emitting device may be a micro light emitting diode (LED). The light emitting device may emit a single peak wavelength or emit a plurality of peak wavelengths.

The pixel PX may further include a pixel circuit connected to the light emitting element. The pixel circuit may include at least one transistor and at least one capacitor. The transistor can be a CMOS transistor.

The pixel unit 110 may include scan lines SL1-SLi applying a scan signal to the pixels PX and data lines DL1-DLj applying a data signal to the pixels PX. The pixel unit 110 may further include light emission control lines that apply a light emission control signal to the pixels PX.

The scan lines SL1-SLi may be connected to the pixels PX arranged in the same row, and each of the day lines DL1-DLj may be connected to the pixels PX arranged in the same column. The emission control lines may be connected to the pixels PX arranged in the same row.

The driving unit 120 is provided in a non-display area around the pixel unit 110 to drive and control the pixel unit 110. The driving unit 120 may include a control unit 121, a scanning driving unit 122, a data driving unit 123, and a power supply unit 124.

Under the control of the control unit 121, the scan driver 122 sequentially applies a scan signal to the scan lines SL1-SLi, and the data driver 123 can apply a data signal to each pixel PX. . Under the control of the control unit 121, the scan driver 122 may sequentially apply the emission control signal to the emission control lines. The pixels PX emit light with a brightness corresponding to a voltage level or a current level of the data signal received through the data lines DL1-DLj in response to the scan signal received through the scan lines SL1-SLi.

The data driver 123 converts n-bit first image data to m-bit (m> n natural number) second image data, and generates a data signal based on a gamma voltage corresponding to the second image data to generate data. Among the lines DL1-DLj, the corresponding data line may be output. The data driver 123 includes first control data corresponding to characteristic data of the driving transistor of the pixel PX among 2 ⁿ gradation levels and second control data corresponding to characteristic data of the driving transistor among the 2 ^m gradation levels. Based on the relationship of, the first image data may be converted into the second image data.

The power supply unit 124 receives external power and/or internal power, converts it to various levels of voltage required for the operation of each component, and converts the corresponding voltage according to a power control signal input from the controller 121 (110).

The power supply unit 124 may generate a first power voltage VDD and apply it to the pixel unit 110. The power supply unit 124 may generate a driving voltage and apply it to the scan driving unit 122 and the data driving unit 123.

The control unit 121, the scan driving unit 122, the data driving unit 123, and the power supply unit 124 are each formed in the form of a separate integrated circuit chip or a single integrated circuit chip and directly on the substrate on which the pixel unit 110 is formed. It may be mounted, mounted on a flexible printed circuit film, attached to a substrate in the form of a tape carrier package (TCP), or directly formed on the substrate.

3 is an example of a pixel of the display device illustrated in FIG. 2.

The light emitting element array 10 includes a plurality of pixels PXs arranged in the pixel unit 110. Each pixel PX is a pixel circuit and a display element connected to the pixel circuit, and includes a light emitting diode EL. The pixel circuit may include a first transistor T1, a second transistor T2, and a capacitor C. Each pixel PX may emit light of, for example, red, green, blue, or white through the light emitting diode EL. The first transistor T1 and the second transistor T2 may be implemented as thin film transistors.

The second transistor T2 is a switching transistor, and is connected to the scan line SL and the data line DL, and controls the data voltage input from the data line DL according to the switching voltage input from the scan line SL. It can be delivered to one transistor (T1). The capacitor C is connected to the second transistor T2 and the driving voltage line supplying the first power voltage VDD, and the voltage received from the second transistor T2 and the first power voltage VDD supplied to the driving voltage line ) Can store the voltage corresponding to the difference.

The first transistor T1 is a driving transistor, and is connected to the driving voltage line and the capacitor C, and can control the driving current flowing through the light emitting diode EL from the driving voltage line in response to the voltage value stored in the capacitor C. . The light emitting diode EL may emit light having a predetermined luminance by a driving current. The counter electrode (eg, cathode) of the light emitting diode EL may be supplied with a second power voltage VSS.

3 illustrates that the pixel circuit includes two transistors and one capacitor, but the present invention is not limited thereto. The pixel circuit may further include a transistor that is turned on and off by a light emission control signal for light emission control. It goes without saying that the number of transistors and the number of capacitors can be variously changed according to the design of the pixel circuit. Also, FIG. 3 shows an example in which the pixel circuit is implemented as a P-type transistor, but the embodiment of the present invention is not limited thereto, and may be implemented as a pixel circuit in which an N-type transistor or a P-type and N-type transistor are mixed.

3 illustrates that the pixel circuit includes two transistors and one capacitor, but the present invention is not limited thereto. The pixel circuit may further include a transistor that is turned on and off by a light emission control signal for light emission control. It goes without saying that the number of transistors and the number of capacitors can be variously changed according to the design of the pixel circuit. Also, FIG. 3 shows an example in which the pixel circuit is implemented as a P-type transistor, but the embodiment of the present invention is not limited thereto, and may be implemented as a pixel circuit in which an N-type transistor or a P-type and N-type transistor are mixed.

4 is a diagram schematically showing a data driver according to an embodiment of the present invention. 5 is a view for explaining gamma voltage generation of a gamma voltage generation unit according to an embodiment of the present invention. 6 is a diagram illustrating bit conversion of input data using a lookup table according to an embodiment of the present invention. 7 to 9 are diagrams illustrating bit conversion of input data according to an embodiment of the present invention.

Referring to FIG. 4, the data driver 123 may include a gamma voltage generator 1231, a data converter 1233, a decoder 1235, and a buffer 1237.

The gamma voltage generation unit 1231 may generate and output gamma voltage to be applied to input data. The gamma voltage generation unit 1231 is a gamma voltage (V<0> to V<N-) based on a gamma graph defining a relationship between input data (gradation level) and output data (gamma voltage) as illustrated in FIG. 5. 1>). The gamma voltages V<0> and V<N-1> of the first grayscale G0 and the Nth grayscale G(N-1) (N=2 ^m ) may be set in advance. The gamma voltage generator 1231 may select and output a gamma voltage corresponding to m-bit input data based on the gamma graph. 5 is an example of a gamma graph with a gamma value of 1, where the x-axis represents a gradation level corresponding to 10-bit input data and the y-axis represents a gamma voltage.

The data conversion unit 1303 may perform extended conversion of bits of input data. For example, the data conversion unit 1303 may convert 8-bit input data I_DATA input from the control unit 121 into 10-bit input data I_DATA'.

The data converter 1233 may convert the 8-bit input data I_DATA into 10-bit input data I_DATA' by performing a bit conversion algorithm that defines a relationship between 8-bit data and 10-bit data.

The data conversion unit 1233 may include a lookup table 1234. The bit conversion algorithm may be performed based on data stored in the lookup table 1234. Referring to FIG. 6, 256 8-bit input data (I_DATA) are matched to one of 1024 10-bit data of the lookup table 1234 according to a bit conversion algorithm and converted into 256 10-bit input data (I_DATA'). Can.

In the bit conversion algorithm, 8-bit data and 10-bit data are matched by matching the first control data (GA, GB, GC, and FIG. 9) and the second control data (GA', GB', GC', and FIG. 9). The conversion relationship can be adjusted. The control data may include first control data (GA, GB, GC) and second control data (GA', GB', GC') corresponding to characteristic data of the driving transistor (T1 in FIG. 3). The characteristic data of the driving transistor may include a voltage corresponding to a boundary point dividing the operating regions of the driving transistor. The characteristic data of the driving transistor may include the threshold voltage of the driving transistor.

The first control data (GA, GB, GC) may be included in 2 ⁿ gradation levels, and the second control data (GA', GB', GC') may be included in 2 ^m gradation levels. For example, the first control data (GA, GB, GC) is an 8-bit gradation level, that is, three gradation levels of 2 ⁸ gradation levels, and the second control data (GA', GB', GC') is It may be a 10-bit gradation level, that is, 3 gradation levels out of 2 ¹⁰ gradation levels. The second control data (GA', GB', GC') are fixed values and can be set in advance. The first control data (GA, GB, GC) may be varied according to the brightness set in the display device.

7 is a view illustrating a reference point setting according to an embodiment of the present invention.

Referring to FIG. 7, three reference points A, B, and C may be determined from a voltage-current (V-I) characteristic curve of the driving transistor. The voltage-current (V-I) characteristic curve represents the relationship between the gate-source voltage (VGS) and the source-drain current (ID) of the driving transistor.

The operating region of the driving transistor includes a subthreshold exponential region, a quadratic region, and a linear region. Since each area is known, detailed description is omitted. The reference point (A) may be a boundary point between the subthreshold exponential region and the quadratic region. The reference point B may be a threshold point corresponding to the threshold voltage Vth. The reference point C may be a boundary point between the quadratic region and the linear region.

In the voltage-current (V-I) characteristic curve of the driving transistor, three reference voltages VA, VB, and VC corresponding to the three reference points A, B, and C may be set. The control point of the gamma graph for brightness adjustment is determined by the reference voltage (VA) corresponding to the reference point (A), the reference voltage (VB) corresponding to the reference point (B), and the reference voltage (VC) corresponding to the reference point (C). Can.

8 is a diagram illustrating a change of a control point according to brightness according to an embodiment of the present invention.

8, a gamma graph 81 with a gamma value of 2.2 at a basic brightness, a gamma graph 83 with a gamma value of 2.2 at the maximum brightness, and a gamma graph 85 with a gamma value of 2.2 at the minimum brightness are shown. A gamma graph with a gamma value of 2.2 for the brightness between the basic brightness and the maximum brightness may be located between the gamma graph 81 and the gamma graph 83. A gamma graph with a gamma value of 2.2 for the brightness between the basic brightness and the minimum brightness may be located between the gamma graph 81 and the gamma graph 85.

Input gradation levels (GA, GB, GC) from control points (A', B', C') on gamma graphs (81, 83, 85) corresponding to the three reference voltages (VA, VB, VC) set in FIG. This is determined, and it can be used as the first control data (GA, GB, GC).

Normally, when the brightness of the display device is adjusted, the gamma graph is adjusted to change the brightness. In the case of the conventional analog gamma circuit, in order to maintain the set gamma value under the adjusted brightness condition, a plurality of setting registers are required because the setting values of a plurality of taps (typically 10 to 13 taps) must be reassigned according to the changed brightness. According to an embodiment of the present invention, by adjusting the gamma graph with only three control points corresponding to three reference voltages (VA, VB, VC) which are characteristic data of the driving transistor, brightness can be adjusted while maintaining a gamma value set by a simple gamma circuit. .

The second control data (GA', GB', GC') may be set in advance corresponding to the three reference voltages (VA, VB, VC).

9 is a diagram illustrating an algorithm for converting 8-bit input data I_DATA into 10-bit input data I_DATA' according to an embodiment of the present invention.

Referring to FIG. 9, the data conversion unit 1233 includes first control data (GA, GB, GC) and second control data determined by a gamma graph having a gamma value of 2.2 corresponding to the adjusted brightness as illustrated in FIG. 8. (GA', GB', GC') can be matched. The data converter 1233 may match the gradation levels GD and G255 of the control point D'on the gamma graphs 81, 83, and 85 shown in FIG. 8 to the highest gradation level G1023 of 10 bits. .

The data converter 1233 defines a conversion relationship between 8-bit data and 10-bit data based on the matched three control data pairs (GA/GA', GB/GB', GC/GC'), and the corresponding bits By performing the conversion algorithm, 256 10-bit input data (I_DATA') matching 256 8-bit input data (I_DATA) may be selected.

Referring back to FIG. 4, the decoder 1235 may receive a gamma voltage corresponding to the 10-bit input data I_DATA' from the data converter 1233 from the gamma voltage generator 1231. The decoder 1235 may select one of the plurality of gamma voltages V<0> to V<N-1> corresponding to 10-bit input data I_DATA' and output the input voltage VIN. The decoder 1235 may be configured for each channel corresponding to each of the data lines DL1-DLj.

The buffer 1237 may generate a data signal DATA corresponding to the input voltage VIN and output it to the data lines DL1-DLj. The buffer 1237 may be configured for each channel corresponding to each of the data lines DL1-DLj. The buffer 1237 may output a data signal DATA as a corresponding data line among the plurality of data lines DL1-DLj.

According to an embodiment of the present invention, by determining the gamma voltage using a voltage that determines the operating region of the driving transistor, brightness can be easily adjusted while maintaining gamma characteristics, thereby reducing circuit complexity.

In the present specification, the present invention has been mainly described with limited embodiments, but various embodiments are possible within the scope of the present invention. Also, although not described, it will be said that equivalent means are also incorporated into the present invention. Therefore, the true protection scope of the present invention should be defined by the claims below.

Claims (5)

A pixel portion including a pixel; And
Data that converts n-bit first image data to m-bit (m> n natural number) second image data, generates a data signal based on a gamma voltage corresponding to the second image data, and outputs the data to the pixel Includes a driving unit;
The data driving unit,
Based on the relationship between the first control data corresponding to the characteristic data of the driving transistor of the pixel among 2 ⁿ gradation levels and the second control data corresponding to the characteristic data of the driving transistor among 2 ^m gradation levels, the A display device for converting first image data to the second image data. According to claim 1,
The characteristic data of the driving transistor includes a voltage corresponding to a boundary point separating an operating region of the driving transistor. According to claim 1,
The characteristic data of the driving transistor includes a threshold voltage of the driving transistor. According to claim 1, The data driving unit,
A display device for adjusting the gamma graph using the characteristic data of the driving transistor. According to claim 1,
The first control data is variable according to the set brightness, the display device.

Images