KR101232176B1 - Driving circuit for liquid crystal display device and method for driving the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device of a liquid crystal display device and a method of driving the same, which can improve the brightness and image quality of an image displayed on an RGBW display device while reducing power consumption. The liquid crystal panel includes a plurality of unit pixels. And a data converter converting and outputting four-color image data according to the gain value extracted using the gray level difference of each of the three-color image data, an inverter controller generating a dimming control signal according to the gain value, and the dimming. It characterized in that it comprises an inverter for driving a plurality of lamps in response to the control signal.

4-color image data, gain value, dimming value, duty ratio

Description

Driving device for liquid crystal display and driving method thereof {Driving circuit for liquid crystal display device and method for driving the same}

1 is a block diagram showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a data converter shown in FIG. 1. FIG.

3 is a block diagram showing a histogram generating unit shown in FIG.

4 is a configuration diagram illustrating an RGBW generation unit illustrated in FIG. 2.

5A and 5B are histograms illustrating a process of extracting gain values from the histogram extractor and the accumulator shown in FIG. 3;

6 is a graph showing a dimming value compared to a gain value according to an embodiment of the present invention.

7A to 7D are waveform diagrams illustrating lamp driving signals according to the gain and dimming values shown in FIG. 6.

8 is a graph showing a dimming value compared to a gain value according to another embodiment of the present invention.

9A to 9D are waveform diagrams illustrating lamp driving signals according to gain and dimming values shown in FIG. 8;

10 is a graph showing a dimming value compared to a gain value according to another embodiment of the present invention.

11A and 11B are waveform diagrams illustrating ramp driving signals according to gain and dimming values shown in FIG. 10.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a driving device and a driving method of the liquid crystal display device capable of reducing the power consumption while improving the brightness and image quality of a displayed image.

Recently, liquid crystal displays, field emission displays, plasma display panels, and light emitting displays are emerging as flat panel displays.

Among flat panel displays, a liquid crystal display includes a plurality of liquid crystal cells in a region defined by a plurality of data lines and a plurality of gate lines, and a thin film transistor (TFT), which is a switch element, is disposed in each liquid crystal cell. The formed TFT substrate and the color filter substrate on which the color filter is formed are maintained at regular intervals and include a liquid crystal layer formed therebetween.

The liquid crystal display obtains a desired image by forming an electric field in the liquid crystal layer according to the data signal and adjusting the transmittance of light passing through the liquid crystal layer. Such a liquid crystal display implements a color for one pixel by combining three color subpixels of red, green, and blue. However, in the general three-color liquid crystal display, since the color filter disposed in each of the red, green, and blue sub-pixels transmits only about one third of the applied light, the overall light efficiency decreases.

Accordingly, Korean Patent Publication No. 2002-13830 (Liquid Crystal Display Device) and 2004-83786 (Driver of Display Device and Its Method) as a method for improving luminance and light efficiency while maintaining color reproducibility of liquid crystal display device. In the driving method), an RGBW liquid crystal display including a white filter in addition to the red, green, and blue color filters has been proposed.

The RGBW liquid crystal display converts a three-color image signal into a four-color image signal to improve the luminance of the color image. In other words, the color gamut is extended by adding white to the color of the three colors of red, green, and blue.

However, since the sub pixel size of the RGBW liquid crystal display is about 0.75% smaller than the sub pixel size of the RGB liquid crystal display, there is a problem in that luminance is reduced when displaying pure colors.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and a driving device and a driving method thereof for improving the brightness and image quality of an image displayed in an RGBW type display device while reducing power consumption. The purpose is to provide.

The driving device of the liquid crystal display according to the embodiment of the present invention for achieving the above object is a liquid crystal panel including a plurality of unit pixels, and the gain value extracted using the gray level difference of each of the three-color image data. And a data converter converting and outputting four-color image data, an inverter controller generating a dimming control signal according to the gain value, and an inverter driving a plurality of lamps in response to the dimming control signal. .

In addition, the driving method of the liquid crystal display according to an embodiment of the present invention for achieving the above object is the step of extracting a gain value using the gray level difference of the three-color image data, the three colors by using the gain value Converting the image data into four-color image data, generating a dimming control signal according to the gain value, and driving a lamp according to the dimming control signal.

Hereinafter, a driving apparatus and a driving method thereof of a liquid crystal display according to an exemplary embodiment of the present invention having the above characteristics will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

The liquid crystal display shown in FIG. 1 includes a liquid crystal panel 2 including four pixel regions, a data driver 4 driving a plurality of data lines DL1 to DLm, and a plurality of gate lines GL1. To the gate driver 6 driving GLn, and the gain value k is extracted from the input three-color image data RGB, and the three-color image data RGB is extracted using the extracted gain value k. The data converter 10 converts and outputs the color image data RGBW, and supplies the four-color image data RGBW from the data converter 10 to the data driver 4 and supplies the data driver 4 with the data driver 4. A timing controller 8 that controls the gate driver 6 and an inverter controller 12 that controls the inverter 14 by varying a dimming value according to the gain value k from the data converter 10. ), The backlight unit 16 for irradiating light to the liquid crystal panel 2, and the sides from the inverter controller 12. In accordance with the dimming value generating a lamp driving signal (ALDS) to an inverter 14, which drives the backlight unit (16).

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel region defined by a plurality of gate lines GL1 to GLn and a plurality of data lines DL1 to DLm, and a liquid crystal connected to a TFT. Capacitor Clc is provided. The liquid crystal capacitor Clc is composed of a pixel electrode connected to a TFT and a common electrode facing each other with the pixel electrode and the liquid crystal interposed therebetween. The TFT supplies the data signals from the respective data lines DL1 to DLm to the pixel electrodes in response to the scan pulses from the respective gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the data signal supplied to the pixel electrode and the common voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of liquid crystal molecules according to the difference voltage. The storage capacitor Cst is connected to the liquid crystal capacitor Clc in parallel so that the voltage charged in the liquid crystal capacitor Clc is maintained until the next data signal is supplied. The storage capacitor Cst is formed by overlapping the pixel electrode with the previous gate line and the insulating layer interposed therebetween. In contrast, the storage capacitor Cst may be formed by overlapping the pixel electrode with the storage line and the insulating layer interposed therebetween.

Meanwhile, in the liquid crystal panel 2, red (R), green (G), blue (B), and white (W) pixels are repeatedly arranged in the row / column direction. A color filter corresponding to each color is disposed in each of the red (R), green (G), and blue (B) pixels, while a separate color filter is not disposed in the white (W) pixel. The red (R), green (G), blue (B), and white (W) pixels form a stripe structure with the same area ratio or different area ratio. Alternatively, the pixels may be arranged in the form of a 2 × 2 matrix.

The data driver 4 converts four-color digital image data Data into analog image data according to the data control signal DCS from the timing controller 8, and scan pulses are supplied to the gate lines GL1 to GLn. One horizontal line of analog image data is supplied to the data lines DL1 through DLm every horizontal period. That is, the data driver 4 selects a gamma voltage having a predetermined level according to the gray value of the analog image data and supplies the selected gamma voltage to the data lines DL1 to DLm.

The gate driver 6 sequentially generates scan pulses, for example, gate high pulses, and supplies them to the gate lines GL1 to GLn in response to the gate control signal GCS from the timing controller 8.

The timing controller 8 arranges the four-color image data RGBW from the data converter 10 so as to be suitable for driving the liquid crystal panel 2, and supplies the four-color image data RGBW to the data driver 4. In addition, the gate control signal GCS and the data control signal DCS are generated using the synchronization signals DCLK, DE, Hsync, and Vsync from the outside to control the data driver 4 and the gate driver 6. .

The data converter 10 may use the gray level difference of the three-color image data RGB supplied to each of the unit pixels consisting of sub-pixels of red (R), green (G), and blue (B) input from the outside. A histogram for each gradation difference is extracted. The three-color image data RGB is converted into four-color image data RGBW and supplied to the timing controller 8 according to the gain value k extracted from the histogram for each gray level difference, and the extracted gain value k ) Is supplied to the inverter control unit 12.

The inverter controller 12 generates a signal in which the dimming value is modulated according to the gain value k from the data converter 10, that is, the dimming control signal Dim. In detail, the inverter controller 12 includes at least one memory and generates a dimming value corresponding to the input gain value k, that is, a dimming control signal Dim. The modulated dimming control signal Dim is supplied to the inverter 14. The conversion relationship of the dimming control signal Dim according to the gain value k will be described in detail later with reference to the attached graph.

The inverter 14 generates a lamp driving signal ALDS to drive a plurality of lamps included in the backlight unit 16. In this case, the inverter 14 responds to the converted dimming control signal Dim from the inverter controller 12. To generate the lamp driving signal ALDS. The inverter 14 drives in a burst mode for varying the on / off time of the lamp according to the input dimming control signal Dim. In this case, the inverter 14 adjusts the brightness of the lamp by varying the on / off time of the lamp or varying the voltage level of the lamp driving signal ALDS.

Specifically, the inverter 14 includes a driving signal generator, a switching unit, and a transformer although not shown in the drawings.

The driving signal generator generates a duty ratio, that is, a high signal ratio in one period, in response to the dimming control signal Dim converted and supplied from the inverter controller 12 to supply a pulse width modulation signal. Create The pulse width modulated signal having a variable duty ratio is supplied to the switching unit. Here, the high section of the pulse width modulated signal is the driving time of the lamp, that is, the lamp ON time.

The switching unit is a structure in which a plurality of switching elements are connected in series or in parallel. Accordingly, an AC drive signal of which amplitude is modulated is generated in response to the pulse width modulation signal from the drive signal generator. That is, an AC drive signal whose amplitude is modulated to have an on / off time synchronized with a high and low period of a pulse width modulated signal input as a digital signal is generated.

The transformer is composed of first and second windings, and the like, and converts the AC drive signal from the switching unit into a high voltage lamp drive signal ALDS by the turns ratio of the first and second windings. That is, the lamp driving signal ALDS is generated and supplied to the backlight unit 16 by being amplified by a high voltage AC voltage so as to correspond to the on / off time and amplitude of the AC driving signal. Here, the lamp driving signal ALDS is supplied on a different frequency level depending on the frequency of driving the liquid crystal display and the number of lamps used. For example, when driving a liquid crystal display composed of eight lamp groups at 60 ms, one frame is 1/60 second (16.7 ms), so one cycle is 2.08 ms to drive eight lamp groups for one frame. It may be supplied with a pulse width according to the set frequency. In addition, the voltage level of the lamp driving signal ALDS may be set differently according to the size of the liquid crystal display and the number of lamps. However, in the case of a general large screen liquid crystal display, the voltage level may be set to have a high voltage level of 100V to 220V.

The backlight unit 16 includes a light source for generating light and an optical unit for diffusing and condensing incident light from the light source to improve light efficiency. The light source mainly uses cylindrical lamps such as Cold Cathode Fluorescent Lamp (CCFL) and External Electrode Fluorescent Lamp (EEFL). The lamp is driven by the high voltage AC voltage from the inverter 14, that is, the lamp drive signal ALDS, to generate light.

FIG. 2 is a diagram illustrating a data converter illustrated in FIG. 1.

As illustrated in FIG. 2, the data converter 10 includes a gray scale detector 110, a histogram generator 120, a gain value extractor 130, and an RGBW generator 140.

The gray scale detection unit 110 shown in FIG. 2 compares the three-color image data RGB from the outside to detect the maximum gray value MAX _RGB and the minimum gray value MIN _RGB of each pixel. In addition, the detected maximum gray value MAX _RGB and the minimum gray value MIN _{RGB are} supplied to the histogram generator 120, and the minimum gray value MIN _{RGB is} supplied to the RGBW generator 140.

FIG. 3 is a diagram illustrating a histogram generator shown in FIG. 2.

The histogram generator 120 illustrated in FIG. 3 includes a first subtractor 121, a histogram calculator 122, and a histogram accumulator 123.

The first subtracting unit 121 is a maximum tank unit pixels each supplied from the tone detecting unit 110 based value (MAX _RGB) minimum gray level value (MIN _RGB), the subtraction operation by the unit pixels by gray level difference (MAX -MIN _RGB in _RGB ) Here, the gray level difference (MAX _{RGB to} MIN _RGB ) for each unit pixel is an element that determines the saturation saturation of the pixel when the three-color image data _{RGB is} converted into the four-color image data RGBW.

The histogram calculator 122 calculates a histogram Hist_s for each gray level difference by counting the number of pixels for each gray level difference (MAX _{RGB to} MIN _RGB ) for each unit pixel supplied from the first subtractor 121.

The histogram accumulator 123 accumulates the histogram Hist_s for each gray level difference from the histogram calculator 122 for each gray level difference, and calculates a cumulative histogram Hist_c for each gray level difference, and calculates the accumulated histogram Hist_c for each gray level difference. It is supplied to the gain value extraction unit 130.

In FIG. 2, the gain value extractor 130 accumulates histograms for each gray level difference when the gray level difference setting value M input from the user is exceeded in the cumulative histogram Hist_c for each gray level supplied from the histogram accumulator 123. The gain value k is extracted according to Equation 1 below using the step N gray limit value N. The gain value extractor 130 supplies the extracted gain value k to the RGBW generator 140 and the inverter controller 12.

In Equation 1, MAX _gray represents a maximum gray value corresponding to the number of bits of the tricolor image data RGB, and becomes '255' when the tricolor image data RGB is 8 bits. In order to prevent the denominator from being zero in Equation 1, one gray scale is added to the gray scale loss limit value N.

The saturation saturation setting value M set by the user is a variable for setting the number of saturation allowable pixels of the pixels displayed on the liquid crystal panel 2. The saturation saturation setting value M may be set to '0', '3000', '6000', '10000', etc. according to the user's preference according to the resolution of the liquid crystal panel 2. The saturation saturation setting value M refers to the number of pixels which does not affect visual quality visually even when saturation occurs during generation of the four-color image data RGBW.

For example, the gain value extracting unit 130 has a saturation setting value M of '10000', and a cumulative value of the histogram Hist_s of each gray level in the cumulative histogram Hist_c for each gray level difference exceeds 10000. When the maximum and minimum gradation difference (MAX _RGB -MIN _RGB ) is' 135 ', set' 135 'to the gradation loss limit value (N), and add' 1 'to the gradation loss limit value (N) to' Divide 255 'and' 136 'to generate a gain value (k) with' 1.875 '.

As shown in FIG. 4, the RGBW generator 140 includes a second subtractor 242 and a multiplier 244.

The second subtractor 141 uses the three-color image data RGB supplied from the outside and the minimum gray value MIN _RGB supplied from the gray scale detector 110 as shown in Equation 2 below. To produce (Ra, Ga, Ba). That is, the second subtractor 141 subtracts the minimum gray value MIN _RGB from each of the three color image data RGB to generate the primary three-color data Ra, Ga, and Ba.

Ra = R-MIN _RGB

Ga = G-MIN _RGB

Ba = B-MIN _RGB

The multiplier 142 uses the first three-color image data Ra, Ga, Ba supplied from the second subtractor 141, and the gain value k supplied from the gain value extractor 130, as follows. According to Equation 3, image data RGBW of four colors is generated.

R = Ra × k

G = Ga × k

B = Ba × k

W = MIN _RGB × k

That is, the multiplier 142 multiplies the gain value k by each of the primary three-color data Ra, Ga, and Ba, and converts the three, i.e., red, green, and blue image converted data (R, G, B). ) The multiplier 142 multiplies the gain value k by the minimum gray value MIN _RGB to generate four colors, that is, white (W) image data (W). Then, the four-color image data RGBW is supplied to the timing controller 8.

On the other hand, the three-color conversion data (R, G, B) generated by the multiplier 142 is a gain value (generated in the cumulative histogram (Hist_c) for each gradation difference by the saturation saturation setting value M set by the user ( As it is amplified by k), the gray scale loss due to gain amplification is minimized by amplifying to be equal to or smaller than the maximum number of gray scales (255 in the case of 8 bits) corresponding to the number of bits of the input data RGB.

As described above, the process of converting the three-color data RGB into the four-color image data RGBW by the data converter 10 according to an exemplary embodiment of the present invention will be described in detail.

First, the data converter 10 detects a maximum gray value MAX _RGB and a minimum gray value MIN _{RGB of} three-color image data RGB corresponding to each unit pixel. Then, the maximum gray level value (MAX _RGB) and a minimum gray level value (MIN _RGB) of the gray-scale difference (MAX -MIN _{RGB RGB)} for use by the gray scale difference by gradation difference histogram by counting the number of pixel-specific, as shown in Figure 5a ( Hist_s)

Next, the histogram Hist_s for each gray level difference is accumulated for each gray level difference to obtain a cumulative histogram Hist_c for each gray level difference as illustrated in FIG. 5B. In addition, the gain value (k) according to Equation 1 is obtained using the cumulative histogram step N for each gray level difference when the cumulative histogram Hist_c for each gray level difference exceeds the gray level setting value M input from the user. Extract

Subsequently, the data converter 10 may convert the four-color image data RGBW according to Equations 2 and 3 using the extracted gain value k, the three-color image data RGB, and the minimum gray value MIN _RGB . Create

As described above, the driving apparatus and driving method of the liquid crystal display according to the embodiment of the present invention determine how much saturation for the pixels in the image by the saturation saturation setting value M set by the user. Because of this, the luminance of the liquid crystal panel 2 having the sub-pixels of RGBW can be kept bright while generating gradation saturation below a level that can be visually recognized by a person.

That is, even if gray scale saturation occurs in a small area of the image displayed on the liquid crystal panel 2, it is difficult to perceive visually. Therefore, setting a high gain value k even in consideration of some partial gray scale loss improves luminance and image quality. To be more advantageous. For example, when the saturation setting value M is set to 10000, 10000 pixels correspond to an area of 0.95% on the liquid crystal panel 2 having a resolution of 1366 × 768 and thus have no effect on visual quality degradation. .

On the other hand, when there are more than a certain number of pure colors of the four-color image data RGBW, the gain value k becomes close to one. That is, when all of the four-color image data RGBW are pure color data, the gain value k is 1 because N in Equation 1 is zero. In this case, the luminance in which the pure color of the four-color image data RGBW is displayed is lower than that in the pure color of the three-color image data RGB. This is because the pixel size of the RGBW display device is 0.75% of the pixel size of the RGB display device.

As described above, when there are more than a predetermined number of pure colors of the four-color image data RGBW, the lamp driving time of the backlight unit 16 is increased to prevent deterioration of the luminance of the pure colors. In addition, when the pure color of the four-color image data RGBW is less than a certain number, the lamp driving time may be reduced according to the increased brightness, thereby reducing power consumption.

To this end, as described above, the inverter controller 12 according to the embodiment of the present invention converts the dimming value, that is, the dimming control signal Dim, according to the gain value k from the data converter 10 to convert the inverter ( 14). The inverter 14 adjusts the brightness of the displayed image by generating the lamp driving signal ALDS by varying the on / off time and the driving voltage level of the lamp so as to correspond to the supplied dimming control signal Dim.

6 is a graph illustrating a dimming value versus a gain value according to an embodiment of the present invention.

As illustrated in FIG. 6, when the gain value k is set to have a range of 1 to 2, the dimming value may be set to 50% to 100%. In this case, since the pixel size of the RGBW liquid crystal display is 0.75% of the pixel size of the RGB liquid crystal display, the gain value k is set to have a dimming control signal of 100% when the gain value k is less than 1 to 1.3. And when the gain value k is 1.3 or more and 2 or less, it may be set in a specific form such as a straight line or a quadratic curve so as to have a dimming value of 99% to 50%. For example, if the gain value (k) is 2, the dimming value is 50%, if the gain value (k) is 1.6, the dimming value is 60%, and if the gain value (k) is 1.4, the dimming value is 85%. It may be set.

7A to 7D are waveform diagrams illustrating lamp driving signals converted according to the gain and dimming values shown in FIG. 6.

6A and 7A to 7D, FIG. 7A illustrates first and second generations in full-on time in response to a pulse width modulated signal having a duty ratio of 100% when the gain value k is less than 1.3. The lamp drive signal ALDS of the periods T1 and T2 is shown. The pulse width modulated signal may be generated at 3.3V in the high period and 0V in the low period.

The duty ratio represents a ratio in which the pulse width modulated signal generated by the drive signal generator of the inverter 14 has a high section in units of one cycle (T). Specifically, when the dimming control signal Dim supplied to the inverter 14 indicates 100% as a digital signal, the pulse width modulation signal of the inverter 14 is supplied only as a high signal. That is, when the digital dimming control signal Dim represents 100%, the duty ratio of the pulse width modulation signal is generated to have a full-on period of 100%. Accordingly, the ramp driving signal ALDS is generated to swing to the full-on period in response to the high period of the pulse width modulated signal having a duty ratio of 100%.

As shown in FIG. 7A, when the gain value k is less than 1 to 1.3, the inverter 14 drives the lamp at full on, thereby increasing the luminance of the displayed image. That is, when the ratio of the pure color is displayed high, the driving time of the lamp can be increased to 100% to increase the luminance of the pure color.

FIG. 7B illustrates a ramp driving signal ALDS in which an on / off period is changed according to a dimming value set to 50% when the gain value k is 2. FIG. Specifically, the inverter 14 generates a pulse width modulated signal having a duty ratio of 50% in response to a dimming value set from the inverter controller 12 according to the gain value k, that is, the dimming control signal Dim. The lamp driving signal ALDS has a 50% ON section and a 50% OFF section in each cycle unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 50%. Occurs.

As shown in FIG. 7B, when the dimming value is low, that is, when the ratio of the displayed pure color is minimized, since the displayed four-color image is in a state where the luminance is increased compared to the three-color image, the lamp driving time is reduced to 50%. Can save power.

In addition, FIG. 7C illustrates the ramp driving signal ALDS whose on / off cycle is varied according to the dimming control signal set to 85% when the gain value k is 1.4. In detail, the inverter 14 generates a pulse width modulated signal having a duty ratio of 70% in response to the dimming control signal Dim converted from the inverter controller 12 according to the gain value k. The lamp driving signal ALDS has 85% ON period and 15% OFF period in each period unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 85%. Occurs.

FIG. 7D illustrates the ramp driving signal ALDS whose on / off period is changed according to the dimming control signal set to 60% when the gain value k is 1.6. In detail, the inverter 14 generates a pulse width modulated signal having a duty ratio of 60% in response to the dimming control signal Dim converted from the inverter controller 12 according to the gain value k. The lamp driving signal ALDS has a 60% ON section and a 40% OFF section in each cycle unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 60%. Occurs.

As described above, the RGBW liquid crystal display according to the exemplary embodiment of the present invention adjusts the dimming value, that is, the brightness of the displayed image according to the gain value k extracted during the conversion of the four-color image data RGBW. 6 to 7D, the gain value k was set in the range of 1 to 2, and then the dimming value was varied according to the duty ratio of the pulse width modulated signal. Accordingly, when the pure color exists over a certain ratio, the brightness is increased by setting the dimming value high according to the size of the sub-pixel, and when the brightness of the image data converted into four colors is increased, the dimming value is set low to consume power. Can be reduced.

The dimming value according to the gain value k may be varied by adjusting the duty ratio of the pulse width modulation signal and the voltage level of the ramp driving signal ALDS. For example, if the voltage level of the lamp driving signal ALDS is generated to swing at a reference voltage level of 120V, the level may be generated to swing at a reference voltage level of 140V in another embodiment of the present invention. The voltage level of the ramp drive signal ALDS may be varied by supplying the voltage level of the pulse width modulation signal directly to the inverter 14 or by setting the voltage level of the ramp drive signal ALDS from the inverter 14 in advance. Can be. For example, when the ramp driving signal ALDS is amplified to a voltage level corresponding to the low and high voltage levels of the pulse width modulation signal by the number of windings of the first and second windings in the transformer of the inverter 14. The voltage level of the ramp driving signal ALDS may be varied by varying the voltage level of the pulse width modulation signal.

8 is a graph illustrating a dimming value versus a gain value according to another embodiment of the present invention.

As shown in FIG. 8, when the gain value k is set to have a range of 1 to 2, the dimming value may be set to 100 + α% to 50 + α%. Here, the variable of 50% to 100% is made by adjusting the duty ratio of the pulse width modulation signal in the inverter 14, the variable of α is made by adjusting the voltage level of the lamp driving signal (ALDS). At this time, since the pixel size of the RGBW display device is 0.75% of the pixel size of the RGB display device, the gain value k is set to have a dimming value of 100 + α% when the gain value k is less than 1 to 1.3. When the gain value k is 1.3 to 2 or less, the gain value k may be set in the form of a secondary curve to have a dimming value of 99 + α% to 50 + α%. For example, if the gain value (k) is 2, the dimming value is 50 + α%, if the gain value (k) is 1.6, the dimming value is 60 + α%, and the gain value (k) is 1.4, the dimming value May be set to 85 + α%. Meanwhile, the pulse width modulated signal may be generated as 6.3V in the high period and 0V in the low period.

9A to 9D are waveform diagrams illustrating lamp driving signals converted according to the gain and dimming values shown in FIG. 8.

Referring to FIGS. 8 and 9A to 9D, FIG. 9A illustrates a first generation generated in a full-on period in response to a pulse width modulated signal having a duty ratio of 100% when the gain value k is less than 1.3. And the lamp driving signal ALDS in the second periods T1 and T2.

The duty ratio represents a ratio in which the pulse width modulated signal generated by the drive signal generator of the inverter 14 has a ramp-on time having a high section in units of one period (T). Specifically, when the dimming control signal Dim supplied to the inverter 14 indicates 100% as a digital signal, the pulse width modulation signal of the inverter 14 is supplied only as a high signal of 6.3V. That is, when the digital dimming control signal Dim represents 100%, the duty ratio of the pulse width modulated signal is generated to have a full-on period of 100%. Accordingly, the ramp driving signal ALDS is generated to swing to the full-on period in response to the high period of the pulse width modulated signal having a duty ratio of 100%. At this time, since the high period of the pulse width modulation signal is applied at a voltage level of 6.3V, the voltage level of the lamp driving signal ALDS is generated to swing the reference voltage level of 140V in response to the pulse width modulation signal.

As shown in FIG. 9A, when the gain value k is less than 1 to 1.3, the inverter 14 drives the lamp at full ON while the reference voltage level of the lamp driving signal ALDS increases by 20V or more. The luminance of is further increased. That is, when the ratio of pure colors is displayed high, the luminance of displaying pure colors can be increased by increasing the voltage level of the lamp driving signal ALDS and its swing width while increasing the driving time of the lamp to 100%.

9B illustrates a ramp driving signal ALDS in which an on / off period is varied according to a dimming value set to 50% when the gain value k is 2. FIG. Specifically, the inverter 14 generates a pulse width modulated signal having a duty ratio of 50% in response to a dimming value set from the inverter controller 12 according to the gain value k, that is, the dimming control signal Dim. The lamp driving signal ALDS has a 50% ON section and a 50% OFF section in each cycle unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 50%. Occurs. At this time, the high section voltage level of the pulse width modulation signal is 6.3V, the low section voltage level is 0V. Accordingly, the voltage level of the ramp driving signal ALDS is generated to swing at the reference voltage level of 140V corresponding to the high period of the pulse width modulation signal.

As shown in FIG. 9B, when the dimming value is low, that is, when the ratio of the displayed pure color is minimized, since the displayed four-color image is in a state where the luminance is increased compared to the three-color image, the lamp driving time is reduced to 50%. Can save power.

In addition, when the gain value k is 1.4, FIG. 9C illustrates a ramp driving signal ALDS in which an on / off period is changed according to a dimming value set to 85%. Specifically, the inverter 14 generates a pulse width modulated signal having a duty ratio of 85% in response to the dimming control signal Dim converted from the inverter controller 12 according to the gain value k. The lamp driving signal ALDS has 85% ON period and 15% OFF period in each period unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 85%. Occurs. At this time, the high section voltage level of the pulse width modulation signal is 6.3V, the low section voltage level is 0V. Accordingly, the voltage level of the ramp drive signal ALDS is generated to swing the reference voltage level of 140V in response to the high section of the pulse width modulation signal.

9D illustrates the ramp driving signal ALDS whose on / off period is changed according to the dimming value set to 60% when the gain value k is 1.6. In detail, the inverter 14 generates a pulse width modulated signal having a duty ratio of 60% in response to the dimming control signal Dim converted from the inverter controller 12 according to the gain value k. The lamp driving signal ALDS has a 60% ON section and a 40% OFF section in each cycle unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 60%. Occurs. At this time, the high section voltage level of the pulse width modulation signal is 6.3V, the voltage level of the low section is 0V. Accordingly, the voltage level of the ramp driving signal ALDS is generated to swing the reference voltage level of 140V in response to the pulse width modulation signal.

As described above, the RGBW liquid crystal display according to another embodiment of the present invention further adjusts by applying a to the dimming control signal Dim according to the gain value k extracted during the conversion of the four-color image data RGBW. Specifically, as shown in FIGS. 8 to 9D, after setting the gain value k in the range of 1 to 2, the dimming value according to the duty ratio of the pulse width modulated signal and the ramp driving signal ALDS is set. The voltage was adjusted by adjusting the level. Accordingly, when the pure color exists over a certain ratio, the luminance of the pure color can be further improved by increasing the voltage level of the lamp driving signal ALDS together with the duty ratio of the pulse width modulation signal.

In the present invention, when the gain value k is less than 1.3, the driving ratio is 100%, the maximum value of the gain value k is set to 2, and the driving ratio is 50%. The setting range of the value k and the duty ratio may be changed. For example, the duty ratio may be set to 100 + α% to 25 + α%. In the embodiment of the present invention, 50 + α% is set to the lowest value based on the experimental value, and the lowest setting value of the duty ratio may be set to the lowest duty ratio within a range capable of classifying the image when driving the lamp. In addition, the setting range of the duty ratio may be changed according to the size, type, and driving method of the liquid crystal display.

For example, the gain value k extracted from the data converter 10 may be set to have a range of 1 to 4. That is, the gain value k extracted by Equation 1 may be extracted up to 4 according to the saturation saturation setting value M and the gradation loss limit value N of the data converter 10. Accordingly, the dimming control signal can be varied by setting the gain value k in the range of 1 to 4. FIG. In this case, the effect according to the dimming value can be further increased than when the gain value k is set in the range of 1-2.

10 is a graph illustrating a dimming value versus a gain value according to another embodiment of the present invention.

As illustrated in FIG. 10, when the gain value k is set to have a range of 1 to 4, the dimming value may be set to 100 + α% to 25 + α%. Here, the variable of 25% to 100% is made by adjusting the duty ratio of the pulse width modulated signal, and the variable of α is made by adjusting the voltage level of the lamp driving signal ALDS. At this time, since the pixel size of the RGBW display device is 0.75% of the pixel size of the RGB display device, the gain value k is set to have a dimming value of 100 + α% when the gain value k is less than 1 to 1.3. And when the gain value k is 1.3 or more and 4 or less, it may be set to a specific curve such as a linear or quadratic curve so as to have a dimming value of 99 + α% to 25 + α%. For example, when the gain value k is 4, the dimming value may be set to 25 + α%, and when the gain value k is less than 1.3, the dimming value may be set to 100 + α%.

FIG. 11A shows the lamp driving of the first and second periods T1 and T2 generated in full-on time in response to a pulse width modulated signal having a duty ratio of 100% when the gain value k is less than 1.3. Indicates signal ALDS.

The duty ratio represents a ratio in which the pulse width modulated signal has a high period, that is, a lamp on period, in one period (T). Specifically, when the dimming control signal Dim supplied to the inverter 14 represents 100% as a digital signal, the pulse width modulation signal of the inverter 14 is supplied only as a high signal of 6.3V. That is, when the dimming control signal Dim represents 100%, the duty ratio of the pulse width modulation signal is generated to have a full-on period of 100%. Accordingly, the ramp driving signal ALDS is generated to swing to the full-on period in response to the high period of the pulse width modulated signal having a duty ratio of 100%. At this time, since the high section of the pulse width modulation signal is applied at a voltage level of 6.3V, the voltage level of the lamp driving signal ALDS is generated to swing at a reference voltage level of 140V in response to the pulse width modulation signal.

As shown in FIG. 11A, when the gain value k is less than 1 to 1.3, the inverter 14 drives the lamp at full ON while the reference voltage level of the lamp driving signal ALDS increases by 20V or more. The luminance of is further increased. That is, when the ratio of pure colors is displayed high, the luminance of displaying pure colors can be increased by increasing the voltage level of the lamp driving signal ALDS and its swing width while increasing the driving time of the lamp to 100%.

11B illustrates a ramp driving signal ALDS in which an on / off period is changed according to a dimming control signal set to 25% when the gain value k is 4. FIG. Specifically, the inverter 14 generates a pulse width modulated signal having a duty ratio of 50% in response to the dimming control signal Dim set according to the gain value k from the inverter controller 12. The lamp driving signal ALDS has a 25% ON section and a 75% OFF section in each cycle unit T1, T2 ,, so as to correspond to a pulse width modulated signal having a duty ratio of 25%. Occurs. At this time, the high level voltage level of the pulse width modulation signal is 6.3V, the low level voltage level is 0V. Accordingly, the voltage level of the lamp driving signal ALDS is generated to swing the reference voltage level of 140V corresponding to the high period of the pulse width modulation signal.

As described above, the RGBW liquid crystal display according to another embodiment of the present invention adjusts the dimming control signal according to the gain value k extracted during the conversion of the four-color image data RGBW. Specifically, as shown in Figs. 10 to 11B, after setting the gain value k in the range of 1 to 4, the dimming value according to the duty ratio of the pulse width modulation signal and the ramp driving signal ALDS is set. The voltage was adjusted by adjusting the level. Accordingly, when the pure color exists over a certain ratio, the luminance of the pure color may be further increased by increasing the voltage level of the lamp driving signal ALDS together with the duty ratio of the pulse width modulation signal. Further, the duty ratio change width of the pulse width modulated signal can be further subdivided according to the gain value k range of 1.3 or more and 4 or less.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The driving apparatus and driving method thereof according to an exemplary embodiment of the present invention extract a gain value such that a gradation loss occurs below a saturation setting value set by a user. The dimming value of the backlight unit is adjusted using the extracted gain value. Accordingly, the present invention can prevent the lowering of the luminance compared to the pure color, minimize the gradation loss of the image data, and reduce the power consumption while improving the display quality.

Claims (16)

A liquid crystal panel including a plurality of unit pixels; A data converting unit converting the three-color image data into four-color image data according to the gain value extracted using the gray level difference of the three-color image data and outputting the four-color image data; An inverter controller configured to generate a dimming control signal according to the gain value; An inverter for driving a plurality of lamps in response to the dimming control signal, The inverter According to the dimming control signal to generate a pulse width modulated signal whose duty ratio is variable in the range of 100% to 25% and generates a drive signal of the lamp in accordance with the pulse width modulated signal to control the lamp driving time Drive of display device. The method of claim 1, The data conversion unit And generating the histogram according to the system of the three-color image data, and generating the gain value using the generated histogram and the saturation setting value set by the user. The method of claim 2, The inverter controller And a dimming control signal set to 100% when the gain value is less than 1.3. The method of claim 3, wherein The inverter controller And a dimming control signal having a range of 100% to 25% when the gain value is in a range of 1.3 or more and 4 or less. delete 5. The method of claim 4, The inverter And adjusting the amplitude of the pulse width modulated signal according to the dimming control signal. The method of claim 6, The inverter And adjusting the amplitude of the lamp driving signal in accordance with the pulse width modulation signal. The method of claim 2, The data converter, A gray scale detector for detecting a maximum and minimum gray scale value for each unit pixel of the three-color image data; A histogram generator for generating the histogram by using a gray level difference between the maximum and minimum gray values; A gain value extracting unit extracting the gain value using the histogram and the gray scale saturation setting value; And an RGBW generator configured to generate red, green, blue, and white converted data using the three-color image data, the minimum gray value, and the gain value. Extracting a gain value using the gradation difference of the three-color image data; Converting the three-color image data into four-color image data using the gain value; Generating a dimming control signal according to the gain value; Driving a lamp according to the dimming control signal, Driving the lamp Generating a pulse width modulated signal having a duty ratio varied in a range of 100% to 25% according to the dimming control signal; And generating a driving signal of the lamp according to the pulse width modulation signal to adjust a lamp driving time. The method of claim 9, Converting the three-color image data to four-color image data Generating a histogram according to the system of the three-color image data, And generating the gain value using the generated histogram and the saturation setting value set by the user. 11. The method of claim 10, Generating the dimming control signal And a dimming control signal set to 100% when the gain value is less than 1.3. The method of claim 11, Generating the dimming control signal And a dimming control signal having a range of 100% to 25% when the gain value is in a range of 1.3 or more and 4 or less. delete 13. The method of claim 12, Driving the lamp And adjusting the amplitude of the pulse width modulated signal according to the dimming control signal. 15. The method of claim 14, Driving the lamp And adjusting the amplitude of the lamp driving signal according to the pulse width modulation signal. 11. The method of claim 10, Converting the three-color image data into the four-color image data Detecting a maximum and minimum gray value of each unit pixel of the three-color image data; Generating the histogram using gray level differences between the maximum and minimum gray values; Extracting the gain value using the histogram and the saturation setting value; And generating red, green, blue, and white converted data using the three-color image data, the minimum gray value, and the gain value.

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