KR20210076618A - Display device and driving method the same - Google Patents

Abstract

The present invention relates to a display device and an operating method thereof. The display device includes: a liquid crystal display panel including a plurality of pixels; a data driving circuit applying a data voltage to each of the pixels; a gate driving circuit driving gate lines of the pixels; a timing controller controlling an operation timing of the driving circuits with a preset frame frequency in a normal driving mode, and controlling an operation timing of the driving circuits with a frame frequency lower than the frame frequency in the normal driving mode, in a low-speed driving mode; light sources generating light to be radiated to the liquid crystal display panel; and a light source control circuit gradually increasing the brightness of the light sources for a period of at least one frame in the low-speed driving mode. Therefore, the present invention is capable of compensating for the brightness of a backlight light source.

Description

Display device and its driving method

The present invention relates to a display device and a driving method thereof.

The low-speed driving technology, which is a technology for reducing power consumption in a display device, is a technology that changes the frame frequency according to the amount of data change. When low-speed driving technology is applied, in a moving picture with data change, the display device is driven normally and the screen of the display device is refreshed according to a preset frame frequency, and in a still image without data change, the display device is driven at a frame frequency slower than the normal driving frequency. refresh the screen.

When the frame frequency is reduced during low-speed driving, a data transition frequency for supplying a data voltage from the data driver is reduced, and thus power consumption may be reduced. On the other hand, as the frame frequency is decreased, the blank period between frames is increased to generate a leakage current, which reduces the transmittance of the panel, thereby lowering the luminance of the screen.

SUMMARY OF THE INVENTION An object of the present invention to solve the problems of the background art is to provide a display device and a driving method thereof, which can solve the problem that the luminance of a screen decreases due to a decrease in transmittance of a panel during low-speed driving.

As a means for solving the above problems, a display device according to an embodiment of the present invention includes: a liquid crystal display panel including a plurality of pixels; a data driving circuit for applying a data voltage to each of the pixels; a gate driving circuit for driving gate lines of the pixels; a timing controller for controlling the operation timing of the driving circuits at a preset frame frequency in the normal driving mode and controlling the operating timing of the driving circuits at a frame frequency lower than the frame frequency of the normal driving mode in the low speed driving mode; light sources for generating light to be irradiated to the liquid crystal display panel; and a light source control circuit for gradually increasing luminance of the light sources during at least one frame period in the low speed driving mode.

The light source control circuit may gradually increase luminance of the light sources in response to a decrease in luminance of an image displayed during the one frame period in the low speed driving mode.

The light source control circuit may increase the luminance of the light sources by 1/2 of the luminance decrease amount.

The light source control circuit may increase the luminance of the light sources in stages after a data voltage is applied to each of the pixels in the low-speed driving mode and before the next data voltage is applied.

The light source control circuit may increase the luminance of the light sources in stages according to the frame frequency of the normal driving mode.

The light source may include an LED, and the light source control circuit may gradually increase the amount of current input to the LED.

The light source control circuit may increase the amount of current in stages according to a frame period of the normal driving mode.

The light source control circuit may receive information on the input current from the system unit to control the luminance of the LED.

The light source control circuit may constantly maintain luminance of the light sources in a normal driving mode.

As a means of solving the above problems, the method of driving a display device according to an embodiment of the present invention includes a liquid crystal display panel including a plurality of pixels and light sources for generating light to be irradiated to the liquid crystal display panel. The method of claim 1 , further comprising: supplying a data voltage to the pixels at a frame frequency lower than a frame frequency of a normal driving mode in a low speed driving mode; and gradually increasing the luminance of the light sources during at least one frame period in the low-speed driving mode.

The step of gradually increasing the luminance of the light sources for at least one frame period in the low-speed driving mode may include reducing the luminance of the image displayed during one frame period of the low-speed driving mode to the frame frequency of the normal driving mode. Accordingly, the method may include increasing the luminance of the light sources in stages.

The step of gradually increasing the luminance of the light sources during at least one frame period in the low-speed driving mode may include increasing the luminance of the light sources by 1/2 of the luminance decrease amount.

The method may further include constantly maintaining the luminance of the light sources in the normal driving mode.

As a means for solving the above problems, a method of driving a display device according to another embodiment of the present invention includes: measuring a luminance change rate during one frame period of data input in a low speed driving mode; dividing the one frame period by frame frequency units of the high-speed driving mode and calculating average luminances in each division period; defining a highest average luminance among the average luminances as a reference luminance; calculating a luminance difference between the average luminance and the reference luminance in each of the divided sections; calculating a compensation current value input to a light source to compensate for the luminance difference in each of the divided sections; storing the compensation current value in each of the divided sections; and compensating for the current input to the light source by applying the compensation current value in the low speed driving mode.

In the display device and the driving method of the present invention, the luminance can be compensated by increasing the luminance of the backlight light source as much as the transmittance of the panel is reduced during low-speed driving.

In addition, the present invention maintains uniform luminance in the blank section and maintains uniform luminance in the blank section by measuring the luminance difference within one frame and adjusting the current of the light source to compensate for the reduced transmittance by checking the amount of transmittance reduction according to the measurement result. can be minimized.

1 is a schematic block diagram of a liquid crystal display according to an embodiment of the present invention.
2 is a view for explaining a driving mode of a liquid crystal display according to an embodiment of the present invention.
3 is a graph illustrating pixel charging characteristics of a liquid crystal display device.
4 is a control block diagram illustrating a backlight driving method according to an embodiment of the present invention.
5 is a data and LED current waveform diagram for explaining a backlight driving method according to an embodiment of the present invention.
6 is a flowchart of a backlight driving method according to an embodiment of the present invention.
7 and 8 are graphs of simulation results of a backlight driving method according to an embodiment of the present invention.

Advantages and features of the present specification and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present specification is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only these embodiments allow the disclosure of the present specification to be complete, and common knowledge in the technical field to which this specification belongs It is provided to fully inform those who have the scope of the invention, and the present specification is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present specification are illustrative and the present specification is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. When 'including', 'having', 'consisting of', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'next to', etc., 'right' Alternatively, one or more other parts may be positioned between the two parts unless 'directly' is used.

The first, second, etc. may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present specification.

Like reference numerals refer to substantially like elements throughout.

Hereinafter, embodiments of the present specification will be described in detail with reference to the accompanying drawings. In the following description, when it is determined that a detailed description of a known function or configuration related to the present specification may unnecessarily obscure the subject matter of the present specification, the detailed description thereof will be omitted.

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

Referring to FIG. 1 , a liquid crystal display according to an embodiment of the present invention includes a liquid crystal display panel 10 , a data driving circuit 12 for driving data lines DL of the liquid crystal display panel 10 , and a liquid crystal display. The gate driving circuit 13 for driving the gate lines GL of the panel 10, the data driving circuit 12 and the gate driving circuit according to the normal driving mode and low speed driving mode signals input from the system unit 14 The timing controller 11 for controlling the 13 , the backlight unit 16 including light sources irradiating light to the liquid crystal display panel 10 , and the light sources according to the current data CD input from the system unit 14 . and a light source control circuit 15 for supplying a driving current to the .

The liquid crystal display panel 10 includes two glass substrates and a liquid crystal layer formed therebetween. A plurality of data lines DL and a plurality of gate lines GL cross each other on the lower glass substrate of the liquid crystal display panel 10 . The liquid crystal cells Clc are arranged in a matrix form in the liquid crystal display panel 10 by the intersecting structure of the data lines DL and the gate lines GL. In addition, the TFT, the pixel electrode 1 of the liquid crystal cell Clc connected to the TFT, and the storage capacitor Cst are formed on the lower glass substrate of the liquid crystal display panel 10 .

A black matrix, a color filter, and a common electrode 2 are formed on the upper glass substrate of the liquid crystal display panel 10 . The common electrode 2 is formed on the upper glass substrate in a vertical electric field driving method such as TN (Twisted Nematic) mode and VA (Vertical Alignment) mode, such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode It is formed on the lower glass substrate together with the pixel electrode 1 in the horizontal electric field driving method. A polarizing plate is attached to each of the upper glass substrate and the lower glass substrate of the liquid crystal display panel 10 , and an alignment layer for setting a pretilt angle of the liquid crystal is formed on the inner surface in contact with the liquid crystal.

The timing controller 11 includes timing control signals DDC for controlling operation timings of the data driving circuit 12 and the gate driving circuit 13 according to the normal driving mode and low speed driving mode signals input from the system unit 14 . , GDC) occurs. The timing controller 11 outputs the RGB data and the data timing control signal DDC to the data driving circuit 12 and outputs the gate timing control signal GDC to the gate driving circuit 13 . The timing controller 11 controls the operation timing of the data driving circuit 12 and the gate driving circuit 13 at a preset frame frequency according to the normal driving mode signal input from the system unit 14, and Accordingly, the operation timings of the data driving circuit 12 and the gate driving circuit 13 are controlled at a frame frequency lower than the frame frequency of the normal driving mode. For example, in the normal driving mode, it may be controlled to operate at a frame frequency of 120 Hz, and in the low speed driving mode, it may be controlled to operate at a frame frequency of 12 Hz.

The data driving circuit 12 converts the digital video data RGB into positive/negative analog data voltages in response to the data timing control signal DDC input from the timing controller 11 , and then converts the data lines DL into positive/negative analog data voltages. supply to

The gate driving circuit 13 sequentially outputs scan pulses (or gate pulses) in response to the gate timing control signal GDC from the timing controller 11 and supplies them to the gate lines GL.

The backlight unit 16 emits light to the liquid crystal display panel 10 including a plurality of light sources. The backlight unit 16 may be implemented as either a direct type or an edge type. The direct backlight unit 16 has a structure in which a plurality of optical sheets and a diffusion plate are stacked under the liquid crystal display panel 10 , and a plurality of light sources are disposed under the diffusion plate. The edge type backlight unit 16 has a structure in which a plurality of optical sheets and a light guide plate are stacked under the liquid crystal display panel 10 , and a plurality of light sources are disposed on the side surface of the light guide plate. The light sources may be implemented as light emitting diodes (LEDs).

The light source control circuit 15 controls the driving current supplied to the LED of the backlight unit 16 . The light source control circuit 15 may supply or block a driving current to the LED to turn it on/off or control the amount of current supplied to the LED. The light source control circuit 15 may control the amount of current input to the LED according to current data (CD) input from the system unit 14 . When the amount of current input to the LED increases, the luminance of the LED may increase to increase the luminance of the backlight unit 16 . The light source control circuit 15 constantly supplies the LED current so that the luminance of the LED is kept constant in the normal driving mode. In the low speed driving mode, the amount of current in the LED is gradually increased so that the luminance of the LED is gradually increased.

The system unit 14 outputs a driving mode selection signal for selecting the normal driving mode and the low speed driving mode to the timing controller, and outputs the current data CD to the light source control circuit 15 . The system unit 14 may be implemented as an external host system or a system board provided inside the liquid crystal display.

The system unit 14 outputs a normal driving mode signal in the case of data having a change in input image data, for example, moving image data, and outputs a low speed driving mode signal in the case of still image data in which there is no change in the data. The driving mode selection signal output by the system unit 14 may include a frame rate sync signal for driving in a normal mode or a low speed mode.

The system unit 14 outputs current data CD respectively corresponding to the normal driving mode and the low speed driving mode to the light source control circuit 15 . In the normal driving mode, the system unit 14 outputs the current data CD so that the driving current supplied to the LED is kept constant. In the low-speed driving mode, the system unit 14 outputs the current data CD so that the driving current supplied to the LED gradually increases. Accordingly, in the low-speed driving mode, the luminance of the backlight unit 16 is increased.

2 is a view for explaining a driving mode of a liquid crystal display according to an embodiment of the present invention. Since the frame frequency during normal driving may be different depending on the liquid crystal display device, and low speed driving means that the frequency is relatively lower than that of normal driving, various frame frequencies may be applied. In the following description, the case of operating at a frame frequency of 120 Hz in the normal driving mode and operating at a frame frequency of 12 Hz in the low speed driving mode is exemplified, but the present invention is not limited thereto.

Referring to FIG. 2 , in the normal driving mode, image data for displaying a corresponding frame is input at every frame sync according to a frame frequency of 120 Hz.

In the low-speed driving mode, image data is input for each frame sync in accordance with 12 Hz, which is 1/10 the speed of the normal driving mode.

The image data input to the frame sync is maintained for one frame period, and the image data of the next frame is input in the next frame sync. In the case of the low-speed driving mode, since the frame sync period is 10 times longer than that in the normal driving mode, the blank period during which the TFT of the pixel is turned off after inputting the image data increases.

3 is a view for explaining the pixel charging characteristics of the liquid crystal display device.

Referring to FIG. 3 , in the pixel of the liquid crystal display device, the gate electrode of the TFT is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode of the TFT is the pixel of the liquid crystal cell Clc. It is connected to the electrode and one electrode of the storage capacitor Cs. The storage capacitor Cs charges the data voltage applied from the data line DL when the TFT is turned on to maintain a constant voltage of the liquid crystal cell Clc. When the scan pulse is applied to the gate line GL, the TFT is turned on to form a channel between the source electrode and the drain electrode to apply the voltage on the data line DL to the pixel electrode of the liquid crystal cell Clc. supply At this time, the arrangement of the liquid crystal molecules of the liquid crystal cell Clc is changed by the electric field between the pixel electrode and the common electrode to modulate the incident light.

When the gate high signal Vg is applied for one horizontal period (1H) to each gate line GL within one frame, the TFT is turned on and the data signal Vd is applied in synchronization therewith. At this time, the pixel voltage Vd charged to the actual pixel is gradually charged according to the RC delay of the data line. At the time of buffering, as the potential of the gate high signal Vg is transferred to the gate low signal, the TFT is turned off (Toff), and the turn-off period of the TFT is maintained until the next frame.

However, when the TFT is turned off after the pixel is fully charged (Vi), the voltage (Vlc(t)) charged to the pixel increases with time due to the leakage current ioff generated in the TFT and the leakage current of the capacitor (ileak). It gradually decreases as time elapses, and as the off time increases, the voltage drop amount Vdrop increases.

In the case of the low-speed driving mode driven at 12 Hz, a blank period during which the TFT of the pixel is turned off after inputting image data is greatly increased compared to the normal driving mode. Accordingly, when the charged voltage Vlc(t) decreases and the voltage Vlc(t) charged in the pixel decreases, the transmittance of the liquid crystal panel 10 decreases. Accordingly, when the luminance of the backlight unit 16 is kept constant, the luminance of the display device decreases due to a decrease in transmittance of the liquid crystal panel 10 .

Accordingly, in the present invention, the luminance of the backlight unit 16 is increased by increasing the driving current supplied to the LED of the backlight unit 16 as much as the transmittance is decreased in the low-speed driving mode, so that the luminance of the display device is maintained constant. .

4 and 5 are views for explaining a backlight driving method according to an embodiment of the present invention. FIG. 4 is a control block diagram for explaining a method for driving a display device according to an embodiment of the present invention, and FIG. 5 is 4 is a data output waveform and LED current waveform diagram of the display device.

Referring to FIG. 4 , the system unit 14 outputs a driving mode selection signal for selecting the normal driving mode and the low speed driving mode to the timing controller, and outputs the current data CD to the light source control circuit 15 .

The system unit 14 outputs a normal driving mode signal in the case of data having a change in image data, for example, moving image data, and outputs a low speed driving mode signal in the case of still image data in which there is no change in the data. The driving mode signal output by the system unit 14 may include a frame rate sync signal for driving in a normal mode or a low speed mode.

The system unit 14 outputs current data CD respectively corresponding to the normal driving mode and the low speed driving mode to the light source control circuit 15 . In the normal driving mode, the system unit 14 outputs the current data CD so that the driving current supplied to the LED is kept constant. In the low-speed driving mode, the system unit 14 outputs the current data CD so that the driving current supplied to the LED is gradually increased.

Here, the system unit 14 includes a memory unit 22 storing current data CD and a current data selection unit 20 selecting current data CD stored in the memory unit 22 .

The memory unit 22 may store current data supplied in the normal driving mode and current data supplied in the low speed driving mode. In the normal driving mode, current data CD supplying a constant current may be stored. In the low-speed driving mode, one frame period is divided into units of the frame frequency in the normal driving mode, and current data CD to be input in each division period may be stored.

The current data selection unit 20 searches for the current data CD corresponding to the current driving mode and outputs it to the light source control circuit 15 .

The timing controller 11 controls the data voltage to be supplied to the liquid crystal display panel 10 at a preset frame frequency according to the normal driving mode signal input from the system unit 14, and the normal driving mode according to the low speed driving mode signal. The data voltage is controlled to be supplied to the liquid crystal display panel 10 at a frame frequency lower than the frame frequency. Accordingly, as shown in FIG. 5 , in the normal driving mode, the data voltage is supplied at a frame frequency of 120 Hz, and in the low speed driving mode, the data voltage is supplied at a frame frequency of 12 Hz.

The light source control circuit 15 controls the amount of current input to the LED according to the current data CD input from the system unit 14 . 5, in the normal driving mode, the light source control circuit 15 constantly supplies the LED current so that the luminance of the LED is kept constant. In the low-speed driving mode, the light source control circuit 15 gradually increases the amount of current in the LED so that the luminance of the LED is gradually increased. Here, the light source control circuit 15 may increase the amount of LED current in stages according to the frame frequency in the normal driving mode. That is, in the case of low-speed driving at 12 Hz, the amount of LED current increases step by step with a frequency period of 120 Hz.

6 is a flowchart of a backlight driving method according to an embodiment of the present invention, illustrating a method of calculating current data CD for controlling an amount of LED current when driving at a low speed.

Referring to FIG. 6 , first, the luminance change rate is measured in the low-speed driving mode (S110). The luminance change rate measured here may mean a degree to which the luminance of data of a predetermined gray scale changes during one frame period.

One frame period in which the luminance change is measured is divided into frame frequency units of the high-speed driving mode (S112), and average luminances in each division are calculated (S112). When the normal driving mode is 120 Hz and the low speed driving mode is 12 Hz, the luminance change during the 12 Hz period may be measured, and the average luminance in each period may be calculated by dividing the luminance change into the 120 Hz period, ie, 10 sections.

The highest average luminance among the calculated average luminances is defined as the reference luminance (S116), and a luminance difference between the average luminance and the reference luminance is calculated in each division section (S118). The luminance is highest immediately after charging is completed, and as the blank period continues, the transmittance decreases due to the leakage current and the luminance gradually decreases. Accordingly, the luminance of the first section among the sections divided into 10 may be defined as the reference luminance, and the luminance difference gradually increases with respect to the remaining nine sections.

When the luminance difference in each division is calculated, a compensation current value input to the light source is calculated to compensate 1/2 of each luminance difference ( S120 ). Here, calculating to compensate for 1/2 of the luminance difference is only one of the embodiments, and may be variously set according to characteristics of the display device, frame frequency in normal/slow driving mode, and the like.

Thereafter, the compensation current value in each divided section is stored in the memory 22 of the system unit 14, and the current input to the light source is compensated by applying the compensation current value stored in the memory 22 in the low-speed driving mode ( S122).

As described above, the present invention can compensate for the decrease in luminance in the blank period by increasing the current supplied to the LED of the backlight unit 16 during the blank period of the low-speed driving mode.

7 and 8 are graphs of simulation results of a backlight driving method according to an embodiment of the present invention.

7 is a data input graph (Data), a transmittance graph for each pixel (transmittance 1st Line to Last Line), an LED luminance graph (LED luminance) and A luminance graph (LCM luminance) of the liquid crystal panel (LCM) is shown.

Referring to FIG. 7 , in the low-speed driving mode, image data is input at 12 Hz, which is 1/10 the speed of the normal driving mode. When the TFT is turned off after the image data (Data) is charged in the pixel, the voltage charged in each pixel line (1st Line to Last Line) gradually decreases due to leakage current, etc., and the longer the blank period, the longer the voltage decrease (Vdrop). ) is increased. When the charging voltage of the pixel is reduced, the transmittance of the liquid crystal LCM is also reduced.

Accordingly, the present invention compensates the LED current supplied to the LED so that the luminance of the LED increases as the blank period elapses.

Although the transmittance of the liquid crystal panel LCM is decreased, the luminance of the LED increases as the transmittance is decreased, so that the luminance of the liquid crystal panel LCM may be maintained constant even during the blank period.

8 is a graph simulating a luminance improvement rate as a result of supplying an LED compensation current in various ways when the gray of the data voltage is different as G63, G127, and G255.

Referring to FIG. 8 , the graph corresponding to the <reference condition> simulates flicker that occurs when displaying G63, G127, and G255 data when the backlight unit 16, that is, the LED current (BLU Current) is not compensated. It is one graph.

<First condition> is when 100% luminance is compensated by gradually increasing the luminance only in the blank period after charging is completed without compensating for the LED current (BLU Current) in the period in which the data voltage of G63 is charged. This is the result of simulating the luminance change of the panel. The flicker of G63 data in <standard condition> is Max. Compared to the measured value of -63dB, the flicker of the data of G63 in <1st condition> is Max. It is measured as -67dB, indicating that the improvement effect is insignificant.

<Second condition> is a result of simulating the change in luminance of the liquid crystal panel when 100% luminance is compensated for by gradually increasing the BLU Current of the LED in both the charging section and the blank section. The flicker of G63 data in <standard condition> is Max. Compared to the measured value of -63dB, the flicker of the G63 data under the <second condition> was Max. It is measured at -91dB, confirming that the improvement effect is high. However, the flicker of the data of G127 in <reference condition> is Max. Compared to the measured value of -74dB, the flicker of the data of G127 under the <second condition> was Max. It can be confirmed that it is rather deteriorated to -63dB.

<Third condition> is the result of simulating the luminance change of the liquid crystal panel when 50% luminance is compensated for by gradually increasing the BLU Current of the LED in both the charging section and the blank section. The flicker of G63 data in <standard condition> is Max. Compared to the measured value of -63dB, the flicker of the data of G63 under <3rd condition> was Max. -70dB has been improved, and the data flicker of G127 is Max. Max at -74dB. -75dB was maintained at almost the same level, and the data flicker of G255 was Max. Max at -94dB. -76dB was confirmed as a good level.

10: liquid crystal display panel 12: data driving circuit
13: gate driving circuit 14: system unit
15: light source control circuit 16: backlight unit
20: current data selection unit 22: memory

Claims (14)

a liquid crystal display panel including a plurality of pixels;
a data driving circuit for applying a data voltage to each of the pixels;
a gate driving circuit for driving gate lines of the pixels;
a timing controller for controlling the operation timing of the driving circuits at a preset frame frequency in the normal driving mode and controlling the operating timing of the driving circuits at a frame frequency lower than the frame frequency of the normal driving mode in the low speed driving mode;
light sources for generating light to be irradiated to the liquid crystal display panel; and
and a light source control circuit for gradually increasing luminance of the light sources during at least one frame period in the low-speed driving mode. According to claim 1,
The light source control circuit,
In the low-speed driving mode, the display device gradually increases the luminance of the light sources in response to the decrease in luminance of the image displayed during the one frame period. 3. The method of claim 2,
The light source control circuit,
The display device increases the luminance of the light sources by 1/2 of the luminance decrease amount. According to claim 1,
The light source control circuit,
In the low-speed driving mode, after a data voltage is applied to each of the pixels, the luminance of the light sources is gradually increased before a next data voltage is applied. 5. The method of claim 4,
The light source control circuit,
A display device for increasing the luminance of the light sources in stages according to the frame frequency of the normal driving mode. According to claim 1,
The light source includes an LED,
wherein the light source control circuit gradually increases the amount of current input to the LED. 7. The method of claim 6,
The light source control circuit,
A display device for increasing the amount of current in stages according to a frame period of the normal driving mode. 7. The method of claim 6,
The light source control circuit,
A display device that receives information on the input current from a system unit and controls the luminance of the LED. According to claim 1,
The light source control circuit,
A display device for constantly maintaining the luminance of the light sources in a normal driving mode. A method of driving a display device comprising a liquid crystal display panel including a plurality of pixels and light sources emitting light to be irradiated to the liquid crystal display panel, the method comprising:
supplying a data voltage to the pixels at a frame frequency lower than a frame frequency of the normal driving mode in the low speed driving mode; and
gradually increasing the luminance of the light sources during at least one frame period in the low-speed driving mode;
A method of driving a display device comprising a. 11. The method of claim 10,
The step of gradually increasing the luminance of the light sources for at least one frame period in the low-speed driving mode includes:
and increasing the luminance of the light sources in stages according to the frame frequency of the normal driving mode in response to a decrease in luminance of an image displayed during one frame period of the low speed driving mode. 12. The method of claim 11,
The step of gradually increasing the luminance of the light sources for at least one frame period in the low-speed driving mode includes:
and increasing the luminance of the light sources by 1/2 of the luminance decrease amount. 11. The method of claim 10,
and maintaining constant luminance of the light sources in the normal driving mode. 11. The method of claim 10,
measuring a luminance change rate during one frame period of input data in a low-speed driving mode;
dividing the one frame period by frame frequency units of the high-speed driving mode and calculating average luminances in each division period;
defining a highest average luminance among the average luminances as a reference luminance;
calculating a luminance difference between the average luminance and the reference luminance in each of the divided sections;
calculating a compensation current value input to a light source to compensate for the luminance difference in each of the divided sections;
and storing the compensation current value in each of the divided sections.

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