KR100520826B1 - Apparatus of generating gamma voltage - Google Patents

Abstract

The present invention relates to a gamma voltage generator that can reduce manufacturing costs.

The gamma voltage generator includes a first gamma voltage generator configured to generate a first gamma voltage so that data supplied to red, green, and blue cells can be converted into an analog data signal having a first gray level; A second gamma voltage generating a second gamma voltage, a third gamma voltage, and a fourth gamma voltage having different voltage values so that data supplied to the red, green, and blue cells can be converted into an analog data signal having a second gray scale. It has a generation unit.

Description

Gamma Voltage Generator {APPARATUS OF GENERATING GAMMA VOLTAGE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for generating a gamma voltage for use in a display device, and more particularly, to a gamma voltage generator for reducing manufacturing costs.

Recently, various flat panel display devices that can reduce weight and volume, which are disadvantages of cathode ray tubes, have emerged. Such flat panel displays include a liquid crystal display, a field emission display, a plasma display panel, and an electro-luminescence (hereinafter, EL). And a display device.

Among them, an EL display device is a self-luminous element that emits a phosphor by recombination of electrons and holes, and is classified roughly into an inorganic EL using an inorganic compound and an organic EL using an organic compound as the phosphor. Such an EL display device has an advantage that the response speed is as fast as that of a cathode ray tube as compared to a passive light emitting device requiring a separate light source like a liquid crystal display device. In addition, EL displays have many advantages such as low voltage driving, self-luminous, thin film type, wide viewing angle, fast response speed, high contrast, and the like, and are expected to be the next generation display devices.

1 is a cross-sectional view showing a general organic EL structure for explaining the light emission principle of an EL display device. The organic EL includes an electron injection layer 4, an electron transport layer 6, a light emitting layer 8, a hole transport layer 10, and a hole injection layer 12 stacked between the cathode 2 and the anode 14.

When a voltage is applied between the anode 14, which is a transparent electrode, and the cathode 2, which is a metal electrode, electrons generated from the cathode 2 are directed toward the light emitting layer 8 through the electron injection layer 4 and the electron transport layer 6. Move. In addition, holes generated from the anode 14 move toward the light emitting layer 8 through the hole injection layer 12 and the hole transport layer 10. Accordingly, in the light emitting layer 8, light is generated by collision between electrons and holes supplied from the electron transport layer 6 and the hole transport layer 10 and recombination, and the light is externally transmitted through the anode 14 which is a transparent electrode. Is emitted so that the image is displayed. The luminescence brightness of such an EL organic element is not proportional to the voltage across the element but proportional to the supply current, so that the anode 14 is usually connected to a constant current source.

2 is a diagram showing a general EL display device.

The EL display device illustrated in FIG. 2 includes an EL display panel 20 including EL cells 28 arranged at each intersection of the scan electrode line SL and the data electrode line DL, and the scan electrode lines SL. The scan driver 22 for driving the?, The data driver 24 for driving the data electrode lines DL, and the gamma voltage generator 26 for supplying a plurality of gamma voltages to the data driver 24 It is provided.

Each of the EL cells 28 is selected when a scan pulse is applied to the scan electrode line SL, which is a cathode, to generate light corresponding to a pixel signal, that is, a current signal, supplied to the data electrode line DL, which is an anode. Each of the EL cells 28 is represented by a diode equivalently connected between the data electrode line DL and the scan electrode line SL. Each of the EL cells 28 is supplied with a negative scan pulse to the scan electrode line SL and emits light when a positive current is applied to the data electrode line DL and a forward voltage is applied thereto. In contrast, the reverse direction voltage is applied to the EL cells 28 included in the unselected scan lines so as not to emit light. In other words, the EL cells 28 that emit light are charged with forward charges, while the EL cells 28 that do not emit light are charged with reverse charges.

The scan driver 22 sequentially supplies the negative scan pulses to the plurality of scan electrode lines SL in line order.

The data driver 24 converts the digital data signal input from the outside into an analog data signal by using the gamma voltage from the gamma voltage generator 26. The data driver 24 supplies the analog data signal to the data lines DL every time a scan pulse is supplied.

In this manner, the conventional EL display device displays an image by supplying a current signal proportional to the input data to each of the EL cells 28 and causing the EL cells 28 to emit light. In addition, the EL cells 28 are R cells having a red (hereinafter referred to as R) phosphor, G cells having a green (hereinafter referred to as G) phosphor, and blue (hereinafter referred to as B) for color implementation. It consists of B cells which have a phosphor. In addition, three R, G, and B cells are combined to implement a color for one pixel. Here, each of the R, G, and B phosphors has different luminous efficiency. In other words, when the same level of data signal is supplied to the R, G, and B cells, the luminance levels of the R, G, and B cells are different. Accordingly, for the white balance of the R, G, and B cells, gamma voltages of the same luminance are set differently for each of the R, G, and B cells. Therefore, the gamma voltage generator 26 supplying gamma voltages to the data driver 24 generates gamma voltages for each of R, G, and B.

3 shows a detailed circuit configuration of the gamma voltage generator 26 shown in FIG.

Referring to FIG. 3, the conventional gamma voltage generator 26 includes an R gamma voltage generator 32, a G gamma voltage generator 34, and a B gamma voltage generator 36.

The R gamma voltage generator 32 includes three divided resistors r1_R, r2_R, and r3_R connected in series between the supply voltage source VDD and the ground voltage source GND. The three divided resistors r1_R, r2_R, and r3_R are used to generate a high gray scale R gamma voltage VL_R and a low gray scale R gamma voltage VH_R to express gray scales. At this time, the low grayscale R gamma voltage VH_R is generated by Equation 1 below, and the high grayscale R gamma voltage VL_R is generated by Equation 2 below.

The G gamma voltage generator 34 includes three divided resistors r1_G, r2_G, and r3_G connected in series between the supply voltage source VDD and the ground voltage source GND. The three divided resistors r1_G, r2_G, and r3_G are used to generate a gray level G gamma voltage (VH_G) and a low gray level G gamma voltage (VL_G). At this time, the low grayscale G gamma voltage VH_G is generated by Equation 3 below, and the high grayscale G gamma voltage VL_G is generated by Equation 4 below.

The B gamma voltage generator 36 includes three divided resistors r1_B, r2_B, and r3_B connected in series between the supply voltage source VDD and the ground voltage source GND. The three divided resistors r1_B, r2_B, and r3_B are used to generate a high gray level B gamma voltage VH_B and a low gray level B gamma voltage VL_B to express gray levels. At this time, the low gray level B gamma voltage VH_B is generated by Equation 5 below, and the high gray level B gamma voltage VL_B is generated by Equation 6 below.

The R, G, and B gamma voltage generators 32, 34, and 36 respectively generate high gray level gamma voltages VL_R, VL_G, and VL_B and low gray level gamma voltages between three resistors connected in series. VH_R, VH_G, VH_B) are generated, and the generated gamma voltages are supplied to the data driver 24. The data driver 24 generates an analog data signal using a gamma voltage corresponding to an input digital data signal among a plurality of gamma voltages, and supplies the generated analog data signal to the data line DL to be synchronized with a scan signal. The EL panel 20 causes a predetermined image to be displayed.

However, the gamma voltage generator 26 must generate a high gray scale R gamma voltage VL_R and a low gray scale R gamma voltage VH_R supplied to the R cell. In addition, the gamma voltage generator 26 should generate the high gray G gamma voltage VL_G and the low gray G gamma voltage VH_G supplied to the G cell. In addition, the gamma voltage generator 26 must generate the high gray level B gamma voltage VL_B and the low gray level B gamma voltage VH_B supplied to the B cell. That is, the high gray level gamma voltages VL_R, VL_G, and VL_B and the low gray level gamma voltages VH_R, VH_G, and VH_B supplied to each of the R, G, and B cells must be generated. To this end, the R, G, and B gamma voltage generators 32, 34, and 36 respectively generate high gray gamma voltages VL_R, VL_G, and VL_B and low gray gamma voltages VH_R between three resistors connected in series. , VH_G, VH_B), so all nine resistors must be considered. Accordingly, there is a problem in that the arrangement of parts is complicated and workability on the module is inferior. In addition, the number of parts occupied on the module has a problem that the manufacturing cost increases.

Accordingly, an object of the present invention is to provide a gamma voltage generating device that can improve workability and reduce manufacturing costs.

In order to achieve the above object, a gamma voltage generation device according to an embodiment of the present invention generates a first gamma voltage so that data supplied to red, green, and blue cells can be converted into an analog data signal having a first gray level. A gamma voltage generator; A second gamma voltage generating a second gamma voltage, a third gamma voltage, and a fourth gamma voltage having different voltage values so that data supplied to the red, green, and blue cells can be converted into an analog data signal having a second gray scale. It has a generation unit.

In the gamma voltage generator, a voltage value of the first gamma voltage is set higher than the second gamma voltage, the third gamma voltage, and the fourth gamma voltage.

In the gamma voltage generator, a second gamma voltage is used when any one of the red, green, and blue data is converted into an analog signal of the second gray level, and the voltage value is equal to the third gamma voltage and the fourth gamma voltage. The third gamma voltage is set equal or higher, and the third gamma voltage is used when any one of the red, green, and blue data except the data used when the second gamma voltage is converted is converted into an analog signal of the second gray level. The voltage value is set equal to or higher than the fourth gamma voltage.

In the gamma voltage generator, a second gamma voltage is used when data supplied to any one of the red cell, green cell, and blue cell is converted into an analog signal of the second gray level, and the third gamma voltage is used in the second gamma voltage. The fourth gamma voltage is used when the data supplied to any one of the red, green, and blue cells except for the cell to which the gamma voltage is supplied is converted into an analog signal of the second gray level. The second gamma voltage, the third gamma voltage, and the third gamma voltage are used when data supplied to any one of the red cells, the green cells, and the blue cells except for the cell to which the gamma voltage is supplied is converted into an analog signal of the second gray level. The voltage value of the gamma voltage is set so that the white balance is correct when the second gray scale is expressed.

In the gamma voltage generator, a first gamma voltage generator includes a first resistor connected to a supply voltage source, and a second gamma voltage generator is connected in series between the first resistor and a base voltage source to divide voltages from 2 to 5. And a fifth resistor.

In the gamma voltage generator, at least one of the first to fifth resistors may be a variable resistor.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG. 4.

4 is a diagram illustrating a gamma voltage generator according to an exemplary embodiment of the present invention.

Referring to FIG. 4, a gamma voltage generator 40 according to an embodiment of the present invention includes a first gamma voltage generator 42 for supplying the same gamma voltage to an R cell, a G cell, and a B cell; A second gamma voltage generator 44 is provided to supply different gamma voltages to the R cells, the G cells, and the B cells.

The first gamma voltage generator 42 generates a gamma voltage for expressing low gray. To this end, the first gamma voltage generator 42 includes a first resistor element R1 connected between the supply voltage source VDD and the second gamma voltage generator 44. In this case, the first resistor R1 may use a fixed resistor or a variable resistor. The first gamma voltage generator 42 supplies the gamma voltage VH_RGB having the same low gray level to the R cells, the G cells, and the B cells.

In detail, when a low gray scale, ie, black, is represented (a black color is represented by combining grays of R, G, and B cells), a gamma voltage having the same low gray scale for each of the R, G, and B cells is represented. Even when (VH_RGB) is supplied, the luminance difference does not occur significantly. Accordingly, the low gray level gamma voltage VH_RGB output from the common terminal n1 between the first resistor element R1 and the second gamma voltage generator 44 is equal to each of the R cells, the G cells, and the B cells. Supply a low gray scale. At this time, the low gray gamma voltage VH_RGB, which is equally supplied to each of the R cells, the G cells, and the B cells, is generated by the following equation (7).

The second gamma voltage generator 44 generates a gamma voltage for expressing high gray. To this end, the second gamma voltage generator 44 includes second to fifth resistor elements R2 to R5 connected in series between the first gamma voltage generator 42 and the ground voltage source GND. In this case, the second to fifth resistor elements R2 to R5 may use a fixed resistor or a variable resistor. By the second gamma voltage generator 42, the R gamma voltage VL_R of high gradation, the G gamma voltage VL_G of high gradation, and the high gradation of R, G, and B cells are different. B gamma voltages VL_B are supplied, respectively.

In detail, when expressing a high gradation, that is, white (white is expressed by combining the gradations of the R, G, and B cells), luminance corresponding to the luminous efficiency of each of the R, G, and B cells is achieved. Differences occur, so the high grayscale R gamma voltage (VL_R), the high grayscale G gamma voltage (VL_G), and the high grayscale B gamma voltage (VL_B) are supplied to each of the R, G, and B cells to achieve white balance. The ratio of must be different. Therefore, when expressing white, the resistance of each of the high gray R gamma voltage VL_R, the high gray G gamma voltage VL_G, and the high gray B gamma voltage VL_B should be considered. In this case, the resistor may be used including a fixed resistor or one or more variable resistors. In consideration of such a resistance, the high gradation R gamma voltage VL_R is output from the common terminal n2 of the second and third gamma resistance elements R2 and R3 and supplied to the data driver shown in FIG. 1. The high gray G gamma voltage VL_G is output from the common terminal n3 of the third and fourth gamma resistors R3 and R4 and supplied to the data driver shown in FIG. The high gray level B gamma voltage VL_B is output from the common terminal n4 of the fourth and fifth resistors R4 and R5 and supplied to the data driver shown in FIG. That is, a high gray scale R gamma voltage (VL_R), a high gray scale G gamma voltage (VL_G), and a high gray scale B gamma voltage (VL_B) are supplied to each of the R cells, the G cells, and the B cells. High gradations of the R cells, the G cells, and the B cells can be expressed. Here, a high gray scale R gamma voltage (VL_R), a high gray scale G gamma voltage (VL_G), and a high gray scale B gamma voltage (VL_B) each having a different voltage value in each of the R cells, the G cells, and the B cells are white balance. Is set to fit. At this time, a high gradation R gamma voltage (VL_R), a high gradation G gamma voltage (VL_G), and a high gradation B gamma voltage (VL_B) are supplied to each of the R cells, the G cells, and the B cells. As shown in Equation 8, the ratios of the R gray gamma voltage VL_R of the high gray level, the G gamma voltage VL_G of the high gray level, and the B gamma voltage VL_B of the high gray level are varied.

Here, the R gamma voltage VL_R of high gradation is set higher than the G gamma voltage VL_G of high gradation, and the G gamma voltage VL_G of high gradation is set higher than the B gamma voltage VL_B of high gradation.

Meanwhile, the high gamma voltage R gamma voltage (VL_R), the high gray G gamma voltage (VL_G) and the high gray B gamma voltage (VL_B) are different according to the characteristics of the organic light emitting materials of the R cells, the G cells, and the B cells. Can be set. In detail, in the second node n2 illustrated in FIG. 4, any one of a high gray R gamma voltage VL_R, a high gray G gamma voltage VL_G, and a high gray B gamma voltage VL_B Can be output. In the third node n3, the R gamma voltage VL_R of the high gray, the G gamma voltage VL_G of the high gray, and the B gamma voltage VL_B of the high gray are excluded except the gamma voltage output from the second node n2. ) May be output. In addition, at the fourth node n4, the R gamma voltage VL_R of high gradation, the G gamma voltage VL_G of high gradation, and the high gradation except for the gamma voltages output from the second and third nodes n2 and n3 are obtained. Any one of the B gamma voltages VL_B may be output. At this time, the gamma voltage ratio of Equation 8 should be changed according to each situation.

In the gamma voltage generator 40 according to the embodiment of the present invention, the low gray level gamma voltage VH_RGB supplied to each of the R cells, the G cells, and the B cells by the first gamma voltage generator 42 is equal to. Is generated. In addition, the second gamma voltage generation unit 44 generates a high gray level R gamma voltage VL_R, a high gray level G gamma voltage VL_G, and a high level having a different voltage value for each of the R cells, the G cells, and the B cells. Gray-level B gamma voltages VL_B are generated. The gamma voltages thus generated are supplied to the data driver shown in FIG. 1. The data driver generates an analog data signal using a gamma voltage corresponding to the input digital data signal among a plurality of gamma voltages, and supplies the generated analog data signal to the data line DL to be synchronized with the scan signal. The predetermined image is displayed.

Accordingly, the gamma voltage generator 40 according to the embodiment of the present invention can reduce the manufacturing cost because the resistance elements are reduced as compared to the conventional gamma voltage generator shown in FIG. Workability can be improved.

As described above, in the gamma voltage generating device according to the present invention, the gamma voltages supplied to the low gradation representation are all the same voltage as the red, green, and blue gamma voltages, and the gamma voltages supplied to the high gradation representation are red, green, and blue. By supplying different gamma voltages, the number of components is reduced, which not only simplifies the arrangement of components but also reduces manufacturing costs.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a cross-sectional view showing the structure of a conventional organic electro-luminescence device.

2 is a view showing a driving device of a conventional organic electroluminescent display panel.

FIG. 3 is a circuit diagram illustrating in detail a gamma voltage generation unit illustrated in FIG. 2.

4 is a circuit diagram illustrating a gamma voltage generator according to an exemplary embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

2: cathode 4: electron injection layer

6: electron transport layer 8: light emitting layer

10 hole transport layer 12 hole injection layer

14 anode 20 electro-luminescence panel

22: scan driver 24: data driver

26, 40: gamma voltage generator 28: EL cell

30: cell driver 42: first gamma voltage generator

44: second gamma voltage generator

Claims (6)

A first gamma voltage generator configured to generate a first gamma voltage so that data supplied to the red, green, and blue cells can be converted into an analog data signal having a first gray level; A second gamma generating a second gamma voltage, a third gamma voltage, and a fourth gamma voltage having different voltage values so that data supplied to the red, green, and blue cells can be converted into an analog data signal having a second gray scale. A gamma voltage generator comprising a voltage generator. The method of claim 1, And a voltage value of the first gamma voltage is set higher than the second gamma voltage, the third gamma voltage, and the fourth gamma voltage. The method of claim 2, The second gamma voltage is used when any one of the red, green, and blue data is converted into an analog signal of the second gray level, and the voltage value is set equal to or higher than the third gamma voltage and the fourth gamma voltage. The third gamma voltage is used when any one of the red, green, and blue data, except for the data used when the second gamma voltage is converted, is converted into an analog signal of the second gray level. A gamma voltage generator, characterized in that it is set equal to or higher than the fourth gamma voltage. The method of claim 1, The second gamma voltage is used when data supplied to any one of the red cell, green cell, and blue cell is converted into an analog signal of the second gray level, and the third gamma voltage is supplied with the second gamma voltage. When the data supplied to any one of the red cell, the green cell, and the blue cell except for the cell is converted into an analog signal of the second gray level, the fourth gamma voltage is supplied with the second and third gamma voltages. It is used when data supplied to any one of the red cell, the green cell, and the blue cell except the cell is converted into an analog signal of the second gray level, and the voltage of the second gamma voltage, the third gamma voltage, and the fourth gamma voltage. And a value is set such that white balance is correct when expressing the second gray scale. The method of claim 1, The first gamma voltage generator includes a first resistor connected to a supply voltage source, And the second gamma voltage generator comprises second to fifth resistors connected in series between the first resistor and the base voltage source to divide the voltage. The method of claim 5, At least one of the first to fifth resistors is a variable resistor.