KR20090010748A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

A liquid crystal display device and a driving method thereof are provided to prevent the lowering of a contrast ratio by generating a reference gradation voltage through a thermistor. In a liquid crystal panel(100), a pixel cell(110) is formed in a region defined by a plurality of data lines and gate lines. A power generator generates the driving power for the gradation voltage varied according to an ambient temperature of the liquid crystal panel. A reference gradation voltage generator generates a compensation power corresponding to the variation of the driving power for the gradation voltage and a plurality of reference gradation voltage with different level by voltage-distributing the driving power for the gradation voltage and the compensation power. A gradation voltage generator generates the plurality of gradation voltages with different levels corresponding to a total of gradation of the data signal by subdividing the reference gradation voltage. A data driver converts the data signal inputted by using the plurality of gradation voltages into an analog image signal and supplies the analog image signal to the data line. A gate driver successively operates the gate lines.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY DEVICE AND DRIVING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display and a driving method thereof capable of preventing a charging failure of a pixel cell generated in a low temperature environment.

In general, the liquid crystal display device displays an image by adjusting the light transmittance of the liquid crystal using an electric field. To this end, a liquid crystal display device drives a liquid crystal panel comprising a liquid crystal panel formed between two glass substrates and a pixel cell arranged in a matrix and switch elements for switching signals supplied to the pixel cells. And a back light unit for irradiating light to the liquid crystal panel.

Each pixel cell of the liquid crystal panel charges an image signal supplied through a switch element, drives a liquid crystal to correspond to the charged image signal, and adjusts the light transmittance of the liquid crystal to display an image corresponding to the image signal.

In general, a liquid crystal display device exhibits image quality characteristics different from room temperature in high and low temperature environments due to temperature characteristics of liquid crystal materials. This is because the liquid crystal material has a change in transmittance due to a change in viscosity due to a change in temperature.

1 is a waveform diagram comparing and comparing voltages charged in pixel cells in a room temperature and a low temperature environment.

As shown in FIG. 1, the image signal Vdata supplied to the pixel cells in the room temperature and low temperature environments respectively supplies the same positive / negative image signal Vdata based on the common voltage Vcom. In the environment, the positive / negative image signal Vdata supplied to the pixel cell is normally charged (Vp1; see dotted line), but in the low-temperature environment, the positive / negative image signal Vdata supplied to the pixel cell is sufficiently charged ( Vp2; see solid line).

As a result, when the liquid crystal panel of the normal white driving method is used in a low temperature environment, there is a problem that the contrast ratio is lowered due to the increase in the black brightness and the decrease in the white brightness.

Furthermore, as the charging time of each pixel cell decreases with increasing size and resolution, in recent years, sufficient charging is not performed in a low temperature environment, resulting in an increase in black brightness and a decrease in contrast ratio due to a decrease in white brightness. There is this.

In order to solve the above problems, the present invention is to provide a liquid crystal display device and a driving method thereof to prevent the charging failure of the pixel cells generated in a low temperature environment.

According to an aspect of the present invention, a liquid crystal panel includes: a liquid crystal panel in which pixel cells are formed in respective regions defined by a plurality of data lines and gate lines; A power generation unit configured to generate driving power for a gray voltage that varies according to an ambient temperature of the liquid crystal panel; A reference gradation voltage generator for generating a plurality of reference gradation voltages having different levels by generating a compensation power corresponding to the variance of the gradation voltage driving power and by voltage-distributing the gradation voltage driving power and the compensation power. ; A gradation voltage generation unit for generating a plurality of gradation voltages having different levels corresponding to the total gradations of data signals by subdividing the reference gradation voltages; A data driver converting the data signal input using the plurality of gray voltages into an analog image signal and supplying the data signal to the data line; And a gate driver for sequentially driving the gate lines.

The power generation unit includes different driving voltages for driving the liquid crystal panel, and includes a driving power generation unit for gray voltages for generating the driving power for the gray voltages; The gray scale voltage driving power generation unit may include: a switching module configured to generate the gray scale voltage driving power by varying a switching time of the switching element according to a feedback signal; First and second voltage divider resistors configured to divide the driving power for the gray voltage to generate the feedback signal; And a thermistor connected in parallel to the first resistor and varying the feedback signal such that the driving power for the gray voltage is varied according to the ambient temperature of the liquid crystal panel.

The reference gray voltage generator may include a voltage compensator configured to generate the compensation power corresponding to a change amount of the driving power for the gray voltage; And a divided resistor string for generating the plurality of reference gray voltages using a plurality of resistors connected in series between the gray scale voltage driving power supply and the compensation power supply.

A driving method of a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel in which pixel cells are formed in each region defined by a plurality of data lines and gate lines. The driving power for the gray voltage is varied according to the ambient temperature of the power supply, and the compensation power corresponding to the variation of the driving voltage for the gray voltage is generated. Generating a plurality of reference gray voltages having a level; Dividing the reference gray voltage to generate a plurality of gray voltages having different levels corresponding to the total number of grays of the data signal; A third step of driving the gate line; And converting the data signal input by using the plurality of gray voltages into an analog image signal, and supplying the converted image signal to the data line to be synchronized with driving of the gate line. It features.

The first step may include varying a switching time of the switching element according to a feedback signal to generate the driving power for the gray voltage; Generating the feedback signal by voltage-distributing the driving power for the gray voltage to first and second resistors; Varying the feedback signal using a thermistor connected in parallel to the first resistor such that the driving power for the gray voltage is varied according to an ambient temperature of the liquid crystal panel; Generating the compensation power corresponding to the change amount of the driving power for the gray voltage; And generating the plurality of reference gray voltages by voltage-dividing the driving power for the gray voltage and the compensation power.

The generating of the compensation power may include generating a distribution voltage by voltage-dividing the driving power for the gray voltage with first and second compensation resistors; And generating the compensation power supply by compensating a difference voltage between the reference voltage and the division voltage to a preset set voltage.

According to an exemplary embodiment of the present invention, a liquid crystal display and a driving method thereof use a reference gray voltage using a compensation power compensated by a compensation voltage of a gray voltage driving power and a gray voltage driving power compensated according to an ambient temperature of a liquid crystal panel using a thermistor. By preventing the charging failure of the pixel cell generated in a low temperature environment can be prevented to reduce the contrast ratio (Contrast Ratio).

In addition, when the liquid crystal panel of the normal white driving method is used in a low temperature environment, the contrast ratio may be prevented from being lowered by preventing black brightness and white brightness from being lowered.

Furthermore, even if the liquid crystal panel having the horizontally striped pixel structure is used in a low temperature environment, it is possible to prevent the charging failure of the pixel cells, thereby preventing the lowering of the contrast ratio.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

2 is a schematic view of a liquid crystal display according to a first embodiment of the present invention.

Referring to FIG. 2, the liquid crystal display according to the exemplary embodiment of the present invention is formed for each region defined by the plurality of data lines DL and the gate lines GL, and three colors are repeatedly generated in the direction of the data line. A liquid crystal panel 100 having a plurality of pixel cells 110 arranged in the direction of the gate line, and a thermistor 328 for detecting a temperature change of the surrounding environment of the liquid crystal panel 100; The gate driver 120 is formed in the liquid crystal panel 100 so as to be connected to each gate line of the liquid crystal panel 100, and drives the gate line GL, and is mounted on the liquid crystal panel 100 so as to be connected to the thermistor 328. The plurality of reference gray voltages are corrected according to the detected detection signal, the image signals generated by the plurality of corrected reference gray voltages are supplied to each data line DL, and the drive for controlling the gate driver 120 is performed. Accumulation Is configured, including 130, a flexible printed to connect the liquid crystal panel is attached to the 100 driving integrated circuits for driving an external system 130 (not shown) St. circuit 200.

The liquid crystal panel 100 includes a lower substrate 102 and an upper substrate 104 bonded together to face each other, a spacer (not shown) for maintaining a constant cell gap between the two substrates 102 and 104, and a spacer. It is configured to include a liquid crystal layer (not shown) formed in the liquid crystal space provided.

The lower substrate 102 includes a display area corresponding to the upper substrate 104 and a non-display area excluding the display area.

In the display area of the lower substrate 102, a plurality of data lines DL1 to DLm formed in parallel in a first direction (vertical direction) to have a predetermined gap, and a second direction crossing the first direction to have a constant gap. The pixel cells 110 formed for each of the regions defined by the plurality of gate lines GL1 to GLn and the plurality of data lines DL1 to DLm and the gate lines GL1 to GLn formed in parallel to each other (horizontal direction). Is formed. In this case, the data lines DL1 to DLm to which the image signal is supplied have a smaller number than the gate lines GL to which the gate-on voltage is supplied.

Each of the pixel cells 110 includes a thin film transistor 112 connected to the gate lines GL1 to GLn and the data lines DL1 to DLm, and a pixel electrode 114 connected to the thin film transistor 112. .

The thin film transistor 112 includes a gate electrode connected to the gate lines GL1 to GLn, a source electrode connected to the data lines DL1 to DLm, and a drain electrode connected to the pixel electrode 114. Accordingly, each of the thin film transistors 112 is switched according to the gate-on voltage supplied to the gate line GL to supply the image signals supplied from the data lines DL1 to DLm to the pixel electrodes 114.

The length of the short side parallel to the data lines DL1 to DLm is formed to be shorter than the long side parallel to the gate lines GL1 to GLn. Accordingly, the pixel electrode 114 has a horizontal stripe shape.

In the non-display area of the lower substrate 102, a gate driver 120 connected to each of the plurality of gate lines GL1 to GLn is formed, and a driving integrated circuit 130 is mounted.

The upper substrate 104 includes a color filter, a common electrode, a light shielding layer, and the like. The common electrode may be formed on the lower substrate 102 according to the liquid crystal formed in the liquid crystal layer.

In the color filter, a red (R) color filter, a green (G) color filter, and a blue (B) color filter are repeatedly formed in the directions of the data lines DL1 to DLm, and along the directions of the gate lines GL1 to GLn. It is formed in the same color.

The common electrode may be formed on the entire surface of the upper substrate 104 to face the pixel electrode 114 or form a line in order to form a vertical electric field in the liquid crystal layer according to the input common voltage. The common electrode may be formed on the lower substrate 102 to be parallel to the pixel electrode 114 to form a horizontal electric field in the liquid crystal layer.

The light blocking layer is formed on the upper substrate 104 so as to overlap the remaining region except the opening region overlapping the pixel electrode 114.

The pixel cells of red (R), green (G), and blue (B) on which the red (R) color filter, the green (G) color filter, and the blue (B) color filter are formed, respectively, display one color image. Constitute a unit pixel.

The flexible printed circuit 200 is attached to a pad portion provided in the non-display area of the lower substrate 102. The flexible printed circuit 200 transmits the source data signal Data and the synchronization signals DE, DCLK, Hsync, and Vsync supplied from the driving system to the driving integrated circuit 130.

The thermistor 328 is disposed in the flexible printed circuit 200 to supply a resistance value corresponding to the ambient temperature of the liquid crystal panel 110 to the driving integrated circuit 130. Here, the thermistor 328 may be formed or installed on the lower substrate 102 or the upper substrate 104 of the liquid crystal panel 110. In this case, the thermistor 328 is not affected by the heat generation of the driving integrated circuit 130. It is preferable to be formed or installed to be as close to the driving integrated circuit 130 as possible so as not to be affected by the line resistance.

The driving integrated circuit 130 is mounted on an integrated circuit mounting unit formed in the non-display area of the lower substrate 102 to have a plurality of input / output pads. Accordingly, each input / output bump provided in the driving integrated circuit 130 is mounted to be electrically connected to each input / output pad of the integrated circuit mounting unit.

The driving integrated circuit 130 may select one frame corresponding to one period of the vertical synchronization signal Vsync using at least one of the synchronization signals DE, DCLK, Hsync, and Vsync supplied from the flexible printed circuit 200. A gate driving signal and a data control signal for driving by dividing into first to third subframes are generated.

In addition, the driving integrated circuit 130 aligns the source data signal Data with the red data R, the green data G, and the blue data B corresponding to each of the first to third subframes. The data R, G, and B are converted into an image signal as an analog signal and supplied to each data line DL. At this time, the driving integrated circuit 130 corrects the plurality of reference gray voltages according to the detection signal from the thermistor 328 and generates an image signal using the corrected plurality of reference gray voltages.

3 is a block diagram illustrating a driving integrated circuit according to an exemplary embodiment of the present invention.

Referring to FIG. 3 and FIG. 2, the driving integrated circuit 130 according to an embodiment of the present invention may include a signal relay 310, a first power generator 320, a clock generator 322, and a second power generator. The unit 326, the signal controller 330, the control signal generator 340, the booster circuit 350, the reference gray voltage generator 355, the gray voltage generator 360, the common voltage generator 370, and the like. It is configured to include a data driver 380.

The signal relay 310 relays the source data signal Data and the synchronization signals DE, DCLK, Hsync, and Vsync supplied from the flexible printed circuit 200 to the signal controller 330.

The clock generator 322 generates a clock for driving the first and second power generators 320 and 326.

The first power generator 320 uses the input power Vin supplied from the flexible printed circuit 200 to generate a first power, that is, a first and second reference according to a clock supplied from the clock generator 322. Generate voltages VSP and VSN. In this case, passive elements such as the resistor 210, the capacitor 220, and the inductor 230 mounted on the flexible printed circuit 200 are connected to the first power generator 320 through the power signal line 321a. The first power supplies VSP and VSN are used for biasing or setting an optional function of the driving integrated circuit 130.

The second power generator 326 uses the liquid crystal panel according to the clock supplied from the clock generator 322 using the first and second reference voltages VSP and VSN generated by the first power generator 320. Second power source required for driving 100, that is, driving for the first and second driving voltages VDD and VSS, the integrated circuit driving voltage Vcc, the gate-on voltage Von, the gate-off voltage Voff, and the gradation voltage. Generate a power source AVDD. In this case, passive elements such as the resistor 210, the capacitor 220, and the inductor 230 mounted on the flexible printed circuit 200 are connected to the second power generator 326 through the power signal line 321b. It is used to bias the second power source (VDD, VSS, Vcc, Von, Voff, AVDD) or to set an optional function of the driving integrated circuit 130.

Meanwhile, the second power generator 326 includes the gray voltage driving power generator 400 shown in FIG. 4 to generate the gray voltage driving power AVDD for generating the reference gray voltage. .

The gray voltage driving power generation unit 400 may include a switching module 402 for generating a gray voltage driving power AVDD using a first reference voltage VSP and a feedback signal, and a switching module 402. Diode D for rectifying the driving voltage AVDD supplied to the first node n1 by the inductor L and outputting it to the output terminal Vout, and driving for the gray voltage output to the output terminal Vout. The first and second resistors R1 and R2 for dividing the power supply AVDD and feeding it back to the switching module 402, the thermistor 328 connected in parallel with the first resistor R1, and the output terminal Vout. And a capacitor C for smoothing the driving voltage AVDD for the gray level voltage to be output. Here, the inductor (L), diode (D), the first and second resistors (R1, R2), capacitor (C), as shown in Figure 2, on the flexible printed circuit 200 329).

The switching module 402 is driven by the first reference voltage VSP supplied to the input terminal IN. The switching module 402 pulse-width modulates an internally generated pulse signal according to the feedback voltage to the switch terminal SW and the ground GND. By controlling a current flowing through the inductor L by switching a switch (not shown) connected between the plurality of transistors, the driving power source AVDD having a voltage level higher than the input voltage VSP is supplied to the first node n1. Be sure to At this time, the inductor L is connected between the input terminal IN and the switch terminal SW.

In detail, the switching module 402 varies the duty ratio of the pulse width modulated signal according to the difference between the set reference voltage and the feedback voltage input to the feedback terminal F / B, thereby changing the switching time of the switch. The level of the voltage supplied to (n1) is varied. At this time, the level Vn1 of the voltage supplied to the first node n1 is inversely proportional to the duty ratio Duty of the pulse width signal, as shown in Equation 1 below.

Vn1 = Vin / (1-Duty)

The diode D rectifies the driving power source AVDD for the gray voltage and supplies it to the output terminal Vout.

Each of the first and second resistors R1 and R2 divides the driving voltage AVDD for the gray voltage output to the output terminal Vout to generate a feedback voltage. To this end, the first resistor R1 is connected to the output terminal Vout and the feedback terminal F / B of the switching module 402, and the second resistor R2 is connected to the feedback terminal F of the switching module 402. / B) and ground (GND).

The thermistor 328 is connected in parallel with the first resistor R1 to provide a resistance value Rtm corresponding to the temperature change of the surrounding environment of the liquid crystal panel 100 to change the feedback voltage according to the temperature change, thereby driving the gray voltage. The power source AVDD is made variable. For example, as shown in FIG. 5, the resistance value Rtm of the thermistor 328 according to the temperature may increase as the ambient temperature decreases and decrease as the ambient temperature increases.

The capacitor C is smoothed by the diode D and smoothes the gray voltage driving power source AVDD outputted to the output terminal Vout.

As described above, the gray voltage driving power generation unit 400 varies the gray voltage driving power AVDD according to the resistance value Rtm of the thermistor 328 corresponding to the temperature change. Done.

AVDD = k + k × (R1 + Rtm) / R2

In Equation 2, k denotes a reference voltage used inside the switching module.

That is, when the ambient temperature of the liquid crystal panel 100 decreases, the resistance value Rtm of the thermistor 328 increases, so that the voltage level of the gradation voltage driving power source AVDD corresponds to the resistance value Rtm of the thermistor 328. Rise as much as possible. On the other hand, when the ambient temperature of the liquid crystal panel 100 rises, the resistance value Rtm of the thermistor 328 decreases, so that the voltage level of the driving voltage AVDD for the gradation voltage is the resistance value Rtm of the thermistor 328. Is lowered to correspond to.

In FIG. 3, the signal controller 330 controls the driving of the signal relay 310 and controls an internal circuit block of the driving integrated circuit 130. In addition, the signal controller 330 aligns the source data signal Data supplied from the signal relay 310 to be suitable for driving the liquid crystal panel 100, and arranges the aligned data R, G, and B for each sub. The data driver 380 is rearranged to correspond to the frame and supplied to the data driver 380.

In detail, the signal controller 330 aligns the source data signal Data supplied from the signal relay 310 to match the resolution of the liquid crystal panel 100.

The signal controller 330 rearranges the red, green, and blue data R, G, and B of the aligned source data signal Data in units of one horizontal section so as to correspond to each of the first to third subframes. Supply to the drive unit 380. That is, the signal controller 330 rearranges the red data R of the source data signal Data to the first subframe data and rearranges the green data G of the source data signal Data to the second subframe data. The blue data B of the source data signal Data is rearranged to the third subframe data.

In addition, the signal controller 330 transmits the synchronization signals DE, DCLK, Hsync, and Vsync supplied from the signal relay 310 to the control signal generator 340.

The control signal generator 340 uses at least one of the data enable DE, the dot clock DCLK, the vertical sync signal Vsync, and the horizontal sync signal Hsync transmitted from the signal controller 330. According to the frame, a data control signal DCS and a gate driving signal GDS for supplying an image signal to each pixel cell 110 are generated. Here, the data control signal DCS includes a data start signal DST, a data shift clock DSC, a data output signal DOE, and a data polarity signal DSP. The gate driving signal GDS includes the gate start signal RVst and the first to i th clock signals RCLK1 to RCLKi.

The booster circuit 350 may include the gate start signal RVst supplied from the control signal generator 340 using the gate-on voltage Von and the gate-off voltage Voff supplied from the second power generator 326. The voltage levels of the i clock signals RCLK1 to RCLKi are boosted. Here, the gate on voltage Von is a voltage for turning on the thin film transistor 112 of each pixel cell 110, and the gate off voltage Voff is a voltage for turning off the thin film transistor 112. . The booster circuit 350 may include a gate start signal Vst and i clock signals CLK1 to CLKi boosted through the gate driving signal transmission line 140 formed in the non-display area of the lower substrate 102. Supply to 120.

The common voltage generator 370 is biased by a passive element of the flexible printed circuit 200 and uses the first and second driving voltages VDD and VSS supplied through the power line 321c to form a liquid crystal panel ( A common voltage Vcom to be supplied to the common electrode of 100 is generated. In this case, the common voltage Vcom may have a constant voltage level or may be inverted to a high or low state according to the data polarity signal DPS.

The reference gray voltage generator 355 divides the gray voltage driving power AVDD supplied from the gray voltage driving power generator 400 of the second power generator 326 to have different voltage levels. Positive reference gray voltages V_PG0 to V_PGj and j negative reference gray voltages V_NG0 to V_NGj.

To this end, the reference gray voltage generator 355 may include a voltage compensator 357 for generating a compensation power supply Vc in which the voltage variation of the gray voltage driving power AVDD is compensated. And a divided resistance train 359 connected in series between the first and second power supplies.

The voltage compensator 357 includes the first and second compensation resistors Rc1 and Rc2 connected in series between the grayscale voltage driving power source AVDD and the ground power source, and the first and second compensation resistors Rc1 and Rc2. The operational amplifier OP is configured to generate a compensation power supply Vc by compensating the difference voltage between the voltage distribution and the reference voltage Vref by the voltage distribution to a preset set voltage.

The first and second compensation resistors Rc1 and Rc2 divide the voltage of the gray voltage driving power source AVDD to generate a divided voltage.

The inverting terminal (-) of the operational amplifier OP is supplied with a divider voltage from the voltage divider node between the first and second compensation resistors Rc1 and Rc2, and the reference voltage Vref is supplied to the non-inverting terminal (+). . The operational amplifier OP supplies the divided resistor train 359 with a compensation power supply Vc in which the voltage difference between the reference voltage Vref and the divided voltage is compensated.

When there is no change in the distribution voltage, the voltage compensator 357 supplies a predetermined set voltage to the divided resistor string 359. On the other hand, the voltage compensator 357 divides the compensating power supply Vc by compensating the voltage difference between the reference voltage Vref and the divided voltage to the set voltage when a voltage change of the gray scale voltage driving power source AVDD is detected. Supply to column 359. For example, assuming that the gray scale voltage driving power source AVDD is set to 10V and the set voltage is set to 3V, the resistance value Rtm of the thermistor 328 becomes larger as the ambient temperature decreases, and the ambient temperature increases. It is assumed that it is getting smaller. First, when the ambient temperature of the liquid crystal panel 100 is at room temperature, since there is no change in the resistance value Rtm of the thermistor 328, the level of the gradation voltage driving power source AVDD and the setting voltage is also unchanged. On the other hand, when the ambient temperature of the liquid crystal panel 100 is at a low temperature, the resistance value Rtm of the thermistor 328 increases, so that the driving power source AVDD for the gradation voltage depends on the resistance value Rtm of the thermistor 328. The voltage level of the voltage rises (e.g., 10V to 12V), and the compensation power supply (Vc) drops as much as the voltage rise of the driving power source (AVDD) for the gradation voltage at the level of the set voltage (e.g., from 3V to 1V). )do.

The divided resistor row 359 includes k divided resistors R0 to Rk having different resistance values connected in series between the grayscale voltage driving power source AVDD and the compensation power source Vc. At this time, the driving voltage AVDD for the gray voltage is supplied to the first voltage divider R0 of the voltage divider resistor 359, and the compensation power Vc is supplied to the kth voltage divider Rk.

At each voltage divider node between k voltage divider resistors R0 to Rk, different voltage levels are applied between the driving power source AVDD and the compensation power source Vc for the gradation voltage according to the resistance value of each of the voltage divider resistors R0 to Rk. J positive reference gradation voltages V_PG0 to V_PGj and j negative reference gradation voltages V_NG0 to V_NGj are output.

The gray voltage generator 360 subdivides the j positive gray voltages and the j negative gray voltages having different voltage levels supplied from the reference gray voltage generator 355 to the data driver 380. . Here, when the source data signal Data is N bits, the gray voltage generator 360 generates 2 ^N positive (+) gray voltages and a negative (−) gray voltage.

The data driver 380 includes a shift register 381, a latch 383, a digital-analog converter 385, a buffer 387, and a selector 389.

The shift register 381 sequentially shifts the data start signal DST according to the data shift clock DSC supplied from the control signal generator 340 to generate the shift signal SS. In this case, the shift register 381 may be a bidirectional shift register driven in both directions according to the direction signal supplied from the signal controller 330.

The latch unit 383 sequentially latches subframe data R, G, and B for one horizontal line supplied from the signal controller 330 according to the shift signal SS supplied from the shift register 381. The latch unit 383 supplies the sub-frame data Rdata for one horizontal line latched in accordance with the data output signal DOE supplied from the control signal generator 340 to the digital-analog converter 385. do.

The digital-analog converter 385 is latched data Rdata supplied from the latch unit 383 by using the j positive gray voltages and the j negative gray voltages supplied from the gray voltage generator 360. Is converted into positive and negative image signals PVS and NVS which are analog signals. At this time, the digital-analog converter 385 selects one gray voltage corresponding to the gray value of the latched data Rdata among the j positive gray voltages as the positive image signal PVS, and at the same time, Among the negative gray voltages, one gray voltage corresponding to the gray value of the latched data Rdata is selected as the negative image signal NVS.

The buffer unit 387 uses the first and second driving voltages Vdd and Vss supplied from the first power generator 320 to the passive element of the flexible printed circuit 200 to form a positive and negative image. Each of the signals PVS and NVS is buffered. At this time, the buffer unit 387 amplifies and outputs each of the positive and negative image signals PVS and NVS in consideration of the load on the data line DL.

The selector 389 selects the positive or negative image signals PVS and NVS supplied from the buffer unit 387 according to the data polarity signal DPS supplied from the control signal generator 340, thereby selecting data lines. It supplies to (DL1-DLm). At this time, the polarity of the image signal output from the selector 389 is inverted in units of subframes and frames in accordance with the data polarity signal DPS.

In FIG. 2, the gate driver 120 is formed in the non-display area of the lower substrate 102 to be connected to each of the plurality of gate lines GL together with the process of forming the thin film transistor 112. The gate driver 120 generates gate-on voltages according to the boosted gate driving signals Vst and CLK1 to CLKi supplied from the driving integrated circuit 130 to sequentially drive the gate lines GL. In this case, the boosted gate driving signals Vst and CLK1 to CLKi are supplied to the gate driver 120 through the plurality of gate driving signal transmission lines 140 formed in the non-display area of the lower substrate 102.

As described above, the liquid crystal display according to the first exemplary embodiment of the present invention uses the thermistor 328 to compensate for the gray voltage driving power source AVDD and the gray voltage driving power source. By generating the reference gray voltage using the compensation power Vc compensated by the compensation voltage of the AVDD, the charging failure of the pixel cells generated in the low temperature environment may be prevented, thereby reducing the contrast ratio.

7 is a waveform diagram illustrating a comparison of voltages charged in pixel cells in a room temperature and a low temperature environment in a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 7, each of the grayscale voltage driving power source AVDD and the compensation power source Vc is compensated according to the resistance value Rtm of the thermistor 328 according to the low temperature environment, thereby supplying the positive cells to the pixel cells in the low temperature environment. It can be seen that the polarity / negative polarity image signal Vdata is normally charged (Vp1; see solid line) in the same manner as the charge in the room temperature environment (Vp2; see dotted line).

Specifically, in a case where a liquid crystal panel of a normal white driving method is used in a low temperature environment, the positive black gray level in the low temperature environment is normal (room temperature environment) by compensation of the driving voltage AVDD for the gray voltage. Since it is implemented by the positive black gray voltage MV_PG0 compensated higher than the positive black gray voltage V_PG0, the black black gray voltage is implemented in the same manner as the positive black gray in a room temperature environment. Similarly, since the negative black gradation in the low temperature environment is implemented by the negative black gradation voltage MV_NG0 which is compensated lower than the normal (room temperature environment) negative black gradation voltage V_NG0 by the compensation power supply Vc. Implemented in the same manner as the negative black gradation in the room temperature environment.

As a result, the first embodiment of the present invention can prevent the increase in the black luminance and the decrease in the white luminance even when the liquid crystal panel of the normally white driving method is used in a low temperature environment, thereby preventing the contrast ratio from being lowered.

In addition, in the first exemplary embodiment of the present invention, since the liquid crystal panel 100 has a horizontal stripe-like pixel structure, the horizontal resolution corresponding to the direction of the gate line GL is reduced to 1/3, whereas the vertical resolution is 3 It is doubled. However, the first embodiment of the present invention can provide the above-described effects even when the liquid crystal panel 100 having the horizontally striped pixel structure is used in a low temperature environment.

8 is a diagram schematically illustrating a liquid crystal display according to a second exemplary embodiment of the present invention.

Referring to FIG. 8, the liquid crystal display according to the second exemplary embodiment of the present invention may include a liquid crystal panel 510; A timing controller 530; The gate driver 540; A reference gray voltage generator 545; A data driver 550; A power generator 520; And thermistor 328.

The liquid crystal panel 510 includes a plurality of pixel cells 512 formed for each region defined by n gate lines GL1 to GLn and m data lines DL1 to DLm.

As illustrated in FIG. 9, red (R), green (G), and blue (B) are repeatedly arranged along the direction of the gate line GL, and as illustrated in FIG. Are arranged in the same color along the direction of. In this case, each pixel cell 512 has a pixel structure in the form of a vertical stripe parallel to the direction of the data line DL. The pixel cells 512 of red (R), green (G), and blue (B) adjacent in the direction of the gate line GL constitute a unit pixel for displaying one color image.

Each pixel cell 512 includes a thin film transistor T connected to a data line DL and a gate line GL; And the pixel P connected to the thin film transistor T. As shown in FIG. The thin film transistor T is turned on according to the gate-on voltage supplied from the gate line GL to supply the image signal supplied from the data line DL to the pixel P. The pixel P is composed of a pixel electrode connected to the common electrode and the thin film transistor TFT with the liquid crystal interposed therebetween, so that the pixel P may be equivalently represented as a liquid crystal capacitor. In addition, each pixel cell 512 includes a storage capacitor (not shown) for maintaining the image signal charged in the liquid crystal capacitor until the next image signal is charged.

The timing controller 530 aligns the source data signal Data supplied from the outside to match the pixel structure and resolution of the liquid crystal panel 100, and supplies the aligned data signal to the data driver 550. In addition, the timing controller 530 generates a data control signal DCS for controlling the driving timing of the data driver 550 and generates a gate driving signal GDS for controlling the driving timing of the gate driver 540. Create

The gate driver 540 sequentially drives the gate lines GL1 to GLn by generating a gate-on voltage according to the gate driving signal GDS from the timing controller 530. Here, the gate driver 120 may be formed on the substrate of the liquid crystal panel 510 at the same time as the manufacturing process of the thin film transistor and may be connected to the gate lines GL1 to GLn.

The thermistor 328 is disposed adjacent to the liquid crystal panel 510 to provide the power generator 520 with a resistance value Rtm corresponding to the ambient temperature of the liquid crystal panel 510. Here, the thermistor 328 may be formed or installed in the liquid crystal panel 510 to provide the power generation unit 520 with a resistance value Rtm corresponding to the ambient temperature of the liquid crystal panel 510. In this case, the substrate It is preferable to be formed or installed as close as possible to the power generation unit 520 so as not to be affected by the line resistance of the.

The power generator 520 uses the input power Vin to receive the first and second driving voltages VDD and VSS, the integrated circuit driving voltage Vcc, and the gate-on voltage required for driving the liquid crystal panel 510. (Von), gate-off voltage (Voff); The common voltage Vcom and the driving power source AVDD for the gray voltage are generated.

In particular, the power generator 520 generates a gray voltage driving power AVDD for generating a reference gray voltage according to the resistance value Rtm of the thermistor 328. To this end, since the power generation unit 520 includes the gray scale voltage driving power generation unit 400 described with reference to FIG. 4, the description thereof will be replaced with the above description.

Since the reference gray voltage generator 545 includes the voltage compensator 357 and the divided resistor string 359 as described with reference to FIG. 6, a description thereof will be replaced with the above description.

The data driver 550 converts the data signals R, G, and B supplied from the timing controller 530 into image signals, which are analog signals, in accordance with the data control signal DCS supplied from the timing controller 530. Image signals for one horizontal line are supplied to the data lines DL1 to DLm every one horizontal period in which the gate-on voltages are supplied to the fields GL1 to GLn. In this case, the data driver 550 inverts the polarity of the image signal supplied to the data lines DL1 to DLm in response to the data polarity signal. The data driver 550 may be mounted on a substrate of the liquid crystal panel 510 and connected to the data lines DL1 to DLm.

As described above, the liquid crystal display according to the second exemplary embodiment of the present invention provides the same effect as the first exemplary embodiment of the present invention even when the liquid crystal panel 510 has an ultra high resolution or a medical ultra high resolution of 1920 × 1080 or more. can do.

Meanwhile, in the liquid crystal display according to the second exemplary embodiment of the present invention, each of the pixel cells 512 is red (R) and green (G) in the direction of the data line DL, as shown in FIG. 10. ) And blue (B) may be repeatedly arranged and the same color along the direction of the gate line (GL). In this case, each pixel cell 512 has a pixel structure in the form of a horizontal stripe parallel to the direction of the gate line GL. The pixel cells 512 of red (R), green (G), and blue (B) adjacent in the direction of the data line DL constitute a unit pixel for displaying one color image.

In the second exemplary embodiment of the present invention, since the liquid crystal panel 510 has a horizontal stripe-like pixel structure, the horizontal resolution corresponding to the direction of the gate line GL is reduced to 1/3, whereas the vertical resolution is vertical. Is tripled. However, the second embodiment of the present invention can provide the above-described effects even when the liquid crystal panel 510 having the horizontal stripe-shaped pixel structure is used in a low temperature environment.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and 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.

1 is a waveform diagram comparing and comparing voltages charged in pixel cells in a room temperature and a low temperature environment;

2 is a schematic view of a liquid crystal display according to a first embodiment of the present invention;

3 is a block diagram illustrating the driving integrated circuit illustrated in FIG. 2;

4 is a circuit diagram illustrating a driving power generator for a gradation power source according to an exemplary embodiment of the present invention;

FIG. 5 is a graph showing resistance characteristics according to temperature of the thermistor shown in FIG. 4;

6 is a circuit diagram illustrating a reference gray voltage generator according to an embodiment of the present invention;

7 is a waveform diagram illustrating a comparison of voltages charged in pixel cells in a room temperature and a low temperature environment in a liquid crystal display according to an exemplary embodiment of the present invention;

8 is a schematic view of a liquid crystal display according to a second embodiment of the present invention;

9 is a diagram illustrating a pixel circuit according to a first embodiment of the liquid crystal panel illustrated in FIG. 8; And

FIG. 10 is a diagram illustrating a pixel circuit according to the second exemplary embodiment of the liquid crystal panel illustrated in FIG. 8.

Claims (11)

A liquid crystal panel in which pixel cells are formed in respective regions defined by a plurality of data lines and gate lines; A power generation unit configured to generate driving power for a gray voltage that varies according to an ambient temperature of the liquid crystal panel; A reference gradation voltage generator for generating a plurality of reference gradation voltages having different levels by generating a compensation power corresponding to the variance of the gradation voltage driving power and by voltage-distributing the gradation voltage driving power and the compensation power. ; A gradation voltage generation unit for generating a plurality of gradation voltages having different levels corresponding to the total gradations of data signals by subdividing the reference gradation voltages; A data driver converting the data signal input using the plurality of gray voltages into an analog image signal and supplying the data signal to the data line; And And a gate driver for sequentially driving the gate lines. The method of claim 1, The power generation unit includes different driving voltages for driving the liquid crystal panel, and includes a driving power generation unit for gray voltages for generating the driving power for the gray voltages; The driving power generator for the gray voltage; A switching module configured to generate a driving power for the gray voltage by varying a switching time of a switching device according to a feedback signal; First and second voltage divider resistors configured to divide the driving power for the gray voltage to generate the feedback signal; And And a thermistor connected in parallel to the first resistor and varying the feedback signal such that the driving power for the gray voltage is varied according to the ambient temperature of the liquid crystal panel. The method of claim 2, The reference gray voltage generator; A voltage compensator for generating the compensation power corresponding to the change amount of the driving power for the gray voltage; And And a divided resistor string for generating the plurality of reference gray scale voltages by using a plurality of resistors connected in series between the gray scale voltage driving power supply and the compensation power supply. The method of claim 3, wherein The voltage compensator, First and second compensation resistors configured to divide the driving power for the gray voltage to generate a divided voltage; And And an operational amplifier configured to generate the compensation power supply by compensating the difference voltage between the reference voltage and the divided voltage to a preset set voltage. The method of claim 1, The pixel cells may be arranged in the same color along the direction of the data line, while red (R), green (G), and blue (B) are repeatedly arranged along the direction of the gate line. And red (R), green (G), and blue (B) are repeatedly arranged in the same color along the direction of the gate line. The method of claim 1, The power generator; The reference gray voltage generator; The gray voltage generator; And the data driver comprises one integrated circuit. The method of claim 6, The integrated circuit, A signal controller to align the data signal to be suitable for driving the liquid crystal panel and to supply the data signal to the data driver; A control signal generator configured to generate a gate driving signal for controlling the gate driver and to generate a data control signal for controlling the data driver; A boost circuit for boosting the gate driving signal and outputting the boosted voltage; And And a common voltage generator supplying a common voltage to the liquid crystal panel. The method of claim 1, And a timing controller for aligning the data signal to be suitable for driving the liquid crystal panel, supplying the data signal to the data driver, and generating a gate driving signal for controlling the gate driver and a data control signal for controlling the data driver. Liquid crystal display, characterized in that. A driving method of a liquid crystal display device comprising a liquid crystal panel in which pixel cells are formed for each region defined by a plurality of data lines and gate lines, Generates a driving voltage for the gray voltage variable according to the ambient temperature of the liquid crystal panel, generates a compensation power corresponding to the variation of the driving voltage for the gray voltage, and divides the driving voltage and the compensation power for the gray voltage. Generating a plurality of reference gray voltages having different levels; Dividing the reference gray voltage to generate a plurality of gray voltages having different levels corresponding to the total number of grays of the data signal; A third step of driving the gate line; And And converting the data signal input by using the plurality of gray voltages into an analog image signal, and supplying the converted image signal to the data line to be synchronized with driving of the gate line. A method of driving a liquid crystal display device. The method of claim 9, The first step is; Generating a driving power for the gray voltage by varying a switching time of a switching device according to a feedback signal; Generating the feedback signal by voltage-distributing the driving power for the gray voltage to first and second resistors; Varying the feedback signal using a thermistor connected in parallel to the first resistor such that the driving power for the gray voltage is varied according to an ambient temperature of the liquid crystal panel; Generating the compensation power corresponding to the change amount of the driving power for the gray voltage; And And dividing the driving power for the gray voltage and the compensation power to generate the plurality of reference gray voltages. The method of claim 10, Generating the compensation power source; Generating a distribution voltage by voltage-dividing the driving power for the gray voltage with first and second compensation resistors; And And generating the compensation power supply by compensating a difference voltage between a reference voltage and the distribution voltage to a preset set voltage.

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