KR20040098729A - Method and Apparatus for Driving Liquid Crystal Display Device - Google Patents

Abstract

PURPOSE: A driving apparatus of an LCD(Liquid Crystal Display) and a driving method thereof are provided to supplying a light having an uniform brightness to an LC panel by altering a current supplied to a backlight according to a driving temperature and a driving time of the LCD. CONSTITUTION: A driving apparatus of an LCD comprises a backlight unit(72), an inverter(70) for supplying a driving current to the backlight unit, and a controller(74) for controlling the driving current. The backlight unit sets a standard current for brightness uniformity. In case of a current different from the standard current, the controller alters the supplied current into the driving current corresponding to the standard current. The driving current is applied to the back light unit through the inverter.

Description

Driving method and driving device of liquid crystal display device {Method and Apparatus for Driving Liquid Crystal Display Device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method and a driving device of a liquid crystal display device, and more particularly, to a driving method and a driving device of a liquid crystal display device capable of maintaining a uniform brightness.

A typical liquid crystal display device displays an image using light supplied from the outside. Accordingly, the conventional liquid crystal display device includes a liquid crystal display module for supplying light to the liquid crystal display device. The liquid crystal display module is divided into an edge type and a direct type according to the light supply method. In the edge type, a fluorescent lamp is installed outside the flat plate, and the light incident from the lamp is supplied to the entire liquid crystal panel by a transparent light guide plate. The direct type method is a method of directly dimming the front of the liquid crystal panel by arranging a plurality of light sources on the back of the liquid crystal panel, and has an advantage of having a higher luminance and a wider light emitting surface than the edge type method.

Referring to FIG. 1, a conventional edge type liquid crystal display module includes a support main 2, a backlight unit and a liquid crystal panel 10 stacked inside the support main 2, and a support main 2. A cover bottom 14 surrounding one side bottom and side of 2) and a case top 16 formed to surround the edge and the cover bottom 14 of the liquid crystal panel 10 are provided.

The support main 2 is a mold, and the side wall surface thereof is formed into a stepped stepped surface. The backlight unit is provided in the lowest inner layer of the support main 2, and the liquid crystal panel 10 is provided on the backlight unit.

The liquid crystal panel 10 includes a lower substrate 10b on which switch elements TFT are mounted, and an upper substrate 10a on which color filters are formed. Liquid crystal is injected between the lower substrate 10b and the upper substrate 10a. Polarizers 22 and 24 are disposed on the upper and lower sides of the liquid crystal panel 10. The lower polarizing plate 22 disposed below the liquid crystal panel 10 polarizes the light beam supplied from the backlight unit and supplies the polarized light beam to the liquid crystal panel 10. The upper polarizing plate 24 provided above the liquid crystal panel 10 polarizes the light beam supplied from the liquid crystal panel 10 and emits the light beam to the outside.

The cover bottom 14 is installed to surround one side bottom and side surfaces of the support main 2. The case top 16 is installed to surround the upper and side surfaces of the support main 2 to fix the support main 2 and the liquid crystal panel 10.

The backlight unit is attached to a lamp housing 18 equipped with a light source (or lamp) 20, a light guide plate 6 for converting light incident from the light source 20 into a surface light source, and a light guide plate 6. Reflecting the light emitted from the rear surface of the light guide plate 6 to the liquid crystal panel 10 by attaching the optical sheets 12 and the light guide plate 6 to increase the efficiency of light incident toward the liquid crystal panel 10. It has a reflecting plate 4 for.

The light source 20 supplies predetermined light toward the light guide plate 6 in response to a current supplied from an external power source. At this time, the light emitted from the light source 20 to the opposite side of the light guide plate 6 is reflected by the lamp housing 18 and is incident to the light guide plate 6.

The light guide plate 6 uniformly distributes the light incident from the light source 20 over its entire area. That is, the light guide plate 6 uniformly distributes the light incident from the light source 20 so that uniform light is incident on the liquid crystal panel 10.

The reflecting plate 4 reflects light incident to the lower side of the light guide plate. In other words, the reflecting plate 4 reflects the light incident from the light guide plate 6 so that the light incident to itself is supplied to the liquid crystal panel 10.

The optical sheets 12 include an upper / lower diffusion sheet and an upper / lower prism sheet. Such optical sheets 12 scatter light incident from the light guide plate so that the light is evenly distributed throughout the light guide plate surface. In addition, the optical sheets 12 refracting and condensing the scattered light to increase the surface brightness and diffuse the light to widen the viewing angle.

The conventional edge type liquid crystal display module supplies light corresponding to a current supplied from the outside to the liquid crystal panel 10 so that an image of a predetermined luminance is displayed on the liquid crystal panel 10.

2 is a view illustrating a conventional direct type liquid crystal display module.

Referring to FIG. 2, a conventional direct type liquid crystal display module includes a panel guide 36, a liquid crystal panel 50 stacked inside the panel guide 36, and a support side 48. A cover bottom 32 to be fastened, a backlight unit stacked in the cover bottom 32, and a case top 38 for fixing the liquid crystal panel 50 are provided.

The panel guide 36 is a mold, and the side wall surface thereof is formed into a stepped stepped surface. The liquid crystal panel 50 is mounted inside the panel guide 36.

The liquid crystal panel 50 includes a lower substrate 50a on which switch elements TFT are mounted, and an upper substrate 50b on which color filters are formed. Liquid crystal is injected between the lower substrate 50a and the upper substrate 50b. The switch elements display an image corresponding to the video signal by changing the refractive index of the liquid crystal in accordance with the video signal supplied from the outside.

The case top 38 is installed to surround the edge of the liquid crystal panel 50 and the panel guide 36 to fix the liquid crystal panel 50 and the panel guide 36.

The cover bottom 32 is installed to be fixed to the support side 48 by screws (not shown). The lamp holder 40 into which the lamp 42 is inserted is mounted on the cover bottom 32 as shown in FIG. 3. That is, a plurality of lamp holders 40 are mounted on the cover bottom 32 at regular intervals. In addition, a reflective sheet 44 is installed between the cover bottom 32 and the lamp holder 40.

The backlight unit includes a plurality of lamps 42 for generating light, a reflective sheet 44 positioned under the plurality of lamps 42, and a diffuser plate 46 positioned over the plurality of lamps 42. ) And optical sheets (not shown) overlying the diffuser plate 46.

Each of the plurality of lamps 42 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode installed at both ends of the glass tube. Such a plurality of lamps 42 are divided into groups of n (n is a positive integer) and inserted into the lamp holder 40.

The reflective sheet 44 reflects the light traveling from the lamp 42 toward the cover bottom 32 toward the diffuser plate 46 to improve the efficiency of the light generated by the lamp 42.

The diffusion plate 46 allows the light generated by the plurality of lamps 42 to propagate toward the liquid crystal panel 50 and diffuses the light to be incident at a wide range of angles. To this end, the diffusion plate 46 coats the light diffusion member on both sides of the film made of a transparent resin.

The optical sheets (not shown) narrow the viewing angle of the light emitted from the diffuser plate 46 to improve the front luminance of the liquid crystal display and reduce the power consumption.

In the conventional direct type liquid crystal display module, light corresponding to a current supplied from the outside is supplied to the liquid crystal panel 50 so that an image having a predetermined luminance is displayed on the liquid crystal panel 50.

In fact, the liquid crystal display device is provided with a direct type liquid crystal display module or an edge type liquid crystal display module, and displays an image having a predetermined luminance by using light supplied from the liquid crystal display module. However, since the lamps 20 and 42 used in the conventional liquid crystal display module have different initial luminance and saturated luminance, there is a problem in that the luminance of the liquid crystal display is uneven.

4 is a diagram illustrating luminance corresponding to a current supplied to a lamp. 4 shows the results of a direct-type liquid crystal display module, a 30 "panel and experiments at room temperature.

Referring to FIG. 4, the brightness of a conventional backlight unit (ie, a lamp) is changed in response to the flow of current and time supplied thereto.

When high current (approximately 7 mA or more in FIG. 4) is supplied to the backlight unit to obtain high luminance, the initial luminance is set high and the saturation luminance is set lower than the initial luminance. In other words, when a high current is supplied, the backlight unit supplies light of high luminance initially and supplies light of low luminance to the liquid crystal panel over time. In fact, when 11 mA of current is supplied to the backlight unit, the initial luminance is set to approximately 670 cd / m 2 and the saturated luminance is set to 437 cd / m 2.

In order to obtain low luminance, the initial luminance is set low and the saturated luminance is set higher than the initial luminance when a low current (a current less than about 7 mA in FIG. 4) is supplied to the backlight unit. In other words, when a low current is supplied, the backlight unit initially supplies light of low brightness and supplies light of high brightness to the liquid crystal panel over time. In fact, when 3 mA of current is supplied to the backlight unit, the initial luminance is set to approximately 32 cd / m 2 and the saturated luminance is set to 85 cd / m 2.

As such, the conventional backlight unit supplies light of different luminance to the liquid crystal panel over time even when the same current is supplied thereto. Therefore, in the conventional liquid crystal panel, an image of uniform luminance cannot be represented. In other words, when a high current is supplied to the backlight unit in order to represent an image of the same brightness in the liquid crystal panel, since the light supplied to the backlight unit is different with time, the luminance difference in the image displayed on the liquid crystal panel is different. Will be generated. On the other hand, the initial luminance and the saturated luminance characteristics of the backlight unit are set differently according to the inch, the elapse of time and the operating temperature of the liquid crystal panel.

Accordingly, it is an object of the present invention to provide a driving method and a driving device of a liquid crystal display device which can maintain the brightness uniformly.

1 is a view showing a conventional edge type liquid crystal display module.

2 is a view showing a conventional direct type liquid crystal display module.

3 is a diagram showing a conventional lamp arrangement of the direct type.

4 is a graph showing luminance generated from a backlight unit in response to an applied current and time;

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

6A and 6B illustrate a method of storing a lookup table.

7A and 7B are diagrams showing an applied current actually supplied corresponding to the current to be supplied.

<Description of Symbols for Main Parts of Drawings>

2: support main 4: reflector

6: LGP 10, 50, 60: liquid crystal panel

10a, 50b: Upper board 10b, 50a: Lower board

12: optical sheet 14,32: cover bottom

16,38 case top 18 lamp housing

20: light source 22,24: polarizing plate

36: panel guide 40: lamp holder

42: lamp 44: reflective sheet

46: diffuser plate 48: support side

62: data driver 64: gate driver

66: timing controller 68: power supply

70: inverter 72: backlight unit

74: tube current controller 76: controller

78: elapsed time check unit 80: temperature sensor

82: memory

In order to achieve the above object, the driving method of the liquid crystal display device of the present invention comprises the steps of setting a reference current having substantially similar initial luminance and saturation luminance in the backlight unit, and when the current other than the reference current is supplied to the backlight unit, And controlling the current supplied to the backlight unit so that light having a uniform brightness can be supplied to the liquid crystal panel.

When the first current higher than the reference current is to be supplied to the backlight unit, the current actually supplied to the backlight unit is set to be higher from the current lower than the first current to the first current.

The current actually supplied to the backlight unit is controlled so that light of luminance corresponding to the saturation luminance of the first current can be supplied from the backlight unit to the liquid crystal panel.

When the first current lower than the reference current is to be supplied to the backlight unit, the current actually supplied to the backlight unit is set to be lowered from the current higher than the first current to the first current.

The current actually supplied to the backlight unit is controlled so that light of luminance corresponding to the saturation luminance of the first current can be supplied from the backlight unit to the liquid crystal panel.

A method of driving a liquid crystal display device according to the present invention includes: a first step of checking a driving temperature of a liquid crystal display device; A second step of checking an elapsed time from a power input time of the liquid crystal display device; Checking a current to be supplied to the backlight unit; And a fourth step of determining an applied current to be actually supplied to the backlight unit in correspondence with the driving temperature, the elapsed time, and the current value to be supplied checked in the first and third steps.

In the fourth step, the applied current to be actually supplied is set such that light having a luminance corresponding to the saturation luminance of the current value to be supplied can be generated in the backlight unit.

The driving method of the liquid crystal display device of the present invention includes controlling the current value supplied to the backlight unit so that the initial luminance and the saturated luminance can be maintained uniformly.

The driving apparatus of the liquid crystal display device of the present invention includes a backlight unit, an inverter for supplying a driving current to the backlight unit, and a tube current controller for controlling the driving current to be supplied from the inverter to the backlight unit.

The tube current controller includes: an elapsed time controller for checking an elapsed time from a power input time of the liquid crystal display device; A temperature sensor for checking a driving temperature of the liquid crystal display device; A memory for storing an elapsed time, a temperature sensor, and an actual applied current to be actually supplied from the inverter to the backlight unit in correspondence with the current value to be supplied from the inverter to the backlight unit; And a controller for extracting from the memory an actual applied current to be actually supplied from the backlight unit by using the information supplied from the elapsed time controller, the temperature sensor, and the inverter.

In the memory, a real applied current to be actually supplied from the inverter to the backlight unit in correspondence with a predetermined temperature unit, a current unit, and an elapsed time is stored in a lookup table.

The actual applied current stored in the lookup table is set such that light of luminance corresponding to the saturation luminance of the current value to be supplied from the inverter to the backlight unit can be generated in the backlight unit.

The predetermined temperature unit is set between 1 ° C and 20 ° C.

The predetermined current unit is set between 0.1 mA and 5 mA.

The tube current controller controls the current actually supplied from the inverter to the backlight unit so that light corresponding to the saturation luminance of the current to be supplied from the inverter to the backlight unit can be generated in the backlight unit.

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

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 7B.

5 is a block diagram illustrating a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 5, a driving apparatus of a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel 60, a data driver 62 and a gate driver 64 for driving the liquid crystal panel 60, and data. A timing controller 66 for controlling the driver 62 and the gate driver 64, a backlight unit 72 for supplying light to the liquid crystal panel 60, and a driving current (drive power supply) to the backlight unit 72. ), A tube current controller 74 for controlling the drive current supplied from the inverter 70 to the backlight unit 72, and a power supply unit 68 for supplying drive power to the liquid crystal display device. ).

The liquid crystal panel 60 displays a predetermined image corresponding to the data signal supplied from the data driver. To this end, the liquid crystal panel 60 controls the light supplied from the backlight unit 72 using the liquid crystal injected between the two glass substrates.

The data driver 62 converts digital data supplied from the timing controller 66 into an analog data signal and supplies the digital data to the data line DL of the liquid crystal panel 60. Here, the data driver 62 is connected with a gamma supply unit (not shown) for supplying a plurality of voltage levels so that digital data can be converted into an analog data signal.

The gate driver 64 supplies a scan signal to the gate line GL when the data signal is supplied to the data line DL. Here, the gate driver 64 sequentially supplies scan signals to the gate lines GL so that each of the liquid crystal cells can be controlled. In the liquid crystal cells to which the scan signal and the data signal are supplied, predetermined light corresponding to the voltage difference is emitted to the scan signal and the data signal to the outside.

The timing controller 66 rearranges the digital data supplied from the outside to match the resolution of the liquid crystal panel 60 and supplies the digital data to the data driver 62. In addition, the timing controller 66 generates various control signals for controlling the data driver 62 and the gate driver 64, and supplies them to the data driver 62 and the gate driver 64.

The power supply unit 68 generates driving voltages (gate high voltage, gate low voltage, gamma reference voltage, common voltage, lamp driving voltage, and the like) necessary for the various driving units and the backlight unit 72 to generate the timing controller 66 and data. It supplies to the drive part 62, the gate drive part 64, the inverter 70, etc.

The inverter 70 receives the lamp driving voltage supplied from the power supply unit and converts the lamp driving voltage into a voltage for driving the backlight unit. That is, the inverter 70 supplies a predetermined voltage and current to the backlight unit 72 using the lamp driving voltage supplied from the power supply unit.

The backlight unit 72 supplies predetermined light to the liquid crystal panel 60 in response to a driving current (driving voltage) supplied from the inverter 70.

The tube current controller 74 controls the drive current (drive voltage) supplied from the inverter 70 to the backlight unit 72. The tube current controller 74 controls the inverter 70 so that a uniform current can be supplied from the backlight unit 72 to the liquid crystal panel 60 regardless of time and driving temperature.

To this end, the tube current controller 74 includes an elapsed time checking unit 78, a temperature sensor 80, a memory 82, and a controller 76. The temperature sensor 80 is installed at a position where the rear surface of the liquid crystal panel 60 or the driving temperature can be monitored to monitor the driving temperature of the liquid crystal display device. The driving temperature checked by the temperature sensor 80 is supplied to the controller 76.

The elapsed time checking unit 78 checks the elapsed time from the turn-on time of the liquid crystal display device to the present. In other words, the elapsed time checking unit 78 checks the elapsed time from the time when the power is input from the outside and supplies it to the control unit 76.

The memory 82 stores a plurality of look up tables (LUTs) corresponding to temperatures as shown in FIG. 6A. In other words, the memory 82 stores a plurality of lookup tables classified into predetermined temperature units (temperature units of 5 ° C. in FIG. 6A). Here, the temperature unit is set by the user in any one of 1 ℃ to 20 ℃ unit. Each lookup table classified into temperature units is subdivided into predetermined current units (1 mA current unit in FIG. 6B) as shown in FIG. 6B. Here, the current unit is set by the user in any one of 0.1 mA to 5 mA units.

Each of the lookup tables divided by the current unit corresponds to a current (current to be supplied to the original backlight unit 72) to be supplied as shown in FIGS. 7A and 7B so that light of uniform brightness can be supplied from the backlight unit 72. Information on the actual applied current (currently supplied to the backlight unit 72).

In detail, the operator first checks the initial luminance and the saturated luminance characteristics of the backlight unit while changing the inch, time, and operating temperature of the liquid crystal panel. At this time, a table as shown in FIG. 4 may be obtained corresponding to the temperature and the supplied current. Thereafter, the user may classify the temperature into predetermined temperature units (any one of 1 ° C. to 20 ° C., 5 ° C. in FIG. 6A), and may be supplied so that the same brightness may be supplied regardless of the current in each predetermined temperature unit. The look-up table obtained by subdividing the actual applied current in correspondence with the current is stored in the memory 82.

A value stored in the lookup table will be described in detail with reference to FIGS. 7A and 7B. As described in FIG. 4, which is the related art of the present application, the backlight unit 72 corresponding to the current is referred to based on a current approximately equal to the initial luminance and the saturated luminance (7 mA in FIG. 4). The characteristics are set oppositely (where the reference currents are set differently by the temperature and the inch of the panel, respectively).

In other words, when a current higher than the reference current is supplied to the backlight unit 72, light of high luminance is initially supplied, and light of low luminance is supplied to the liquid crystal panel over time. Therefore, when a current higher than the reference current is supplied, the value stored in the lookup table as shown in FIG. 7A is set to supply a high current from the low current. In other words, the luminance of the backlight unit 72 is set by setting the current actually applied lower than the current to be supplied so that the luminance initially supplied becomes approximately similar to the saturation luminance, and gradually increasing the current over time. On the other hand, when the backlight unit 72 reaches saturation luminance after a certain time, the current to be supplied and the actual applied current are set to be the same. In the present invention, the lookup table stored in the memory 82 may be expressed by a specific formula to calculate the actual applied current. Here, the specific formula calculates the actual applied current corresponding to the current to be stored and supplied to the controller 76 or the inverter 70.

On the other hand, when a current lower than the reference current is supplied to the backlight unit 72, light of low luminance is initially supplied, and light of high luminance is supplied to the liquid crystal panel over time. Therefore, when a current lower than the reference current is supplied, the value stored in the lookup table as shown in FIG. 7B is set to supply a low current from the high current. In other words, the luminance of the backlight unit 72 is set by setting the current actually applied higher than the current to be supplied so that the luminance initially supplied becomes approximately similar to the saturation luminance, and gradually lowering the current over time. Can be kept uniform. On the other hand, when the backlight unit 72 reaches saturation brightness after a certain time, the current to be supplied and the actual applied current are set equally.

7A and 7B illustrate that the actual applied current changes in 0.1 mA units for convenience of description. In practice, however, the actual applied current is determined experimentally in response to changes in inches, time, and operating temperature of the liquid crystal panel. In addition, although the elapsed time is shown in FIG. 7A and FIG. 7B as being changed in units of "1 minute", the unit of change in the actual elapsed time may be variously set by the operator.

When the operation of the tube current controller 74 of the present invention is described in detail, the controller 76 receives an elapsed time from a time point at which power is input to the liquid crystal display device from the elapsed time checking unit 78 to the present. The controller 76 receives a driving temperature at which the liquid crystal display device is driven from the temperature sensor 80. In addition, the controller 76 receives a current value to be supplied from the inverter 70 to the backlight unit 72.

The controller 76 receiving the driving temperature from the temperature sensor 80 selects a lookup table corresponding to the currently input temperature from the lookup table stored in the memory 82. Thereafter, the controller 76 selects one of the lookup tables that are divided according to the current value to be supplied. The controller 76 extracts the actual applied current value corresponding to the current elapsed time from the segmented lookup table. That is, the controller 76 extracts the actual applied current value corresponding to the temperature, the current value to be supplied and the elapsed time from the memory 82 and supplies it to the inverter 70. The inverter 70 supplies a current (or voltage) value corresponding to the actual applied current value input to the backlight unit 72. The backlight unit 72 supplies a predetermined light corresponding to the actual applied current supplied from the inverter 70 to the liquid crystal panel 60.

As described above, according to the driving method and driving apparatus of the liquid crystal display device according to the present invention, light of uniform brightness is emitted from the backlight unit by changing the current value supplied to the backlight unit in response to the driving temperature and the elapsed time of the liquid crystal display device. This liquid crystal panel can be supplied.

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

Claims (15)

Setting a reference current having substantially similar initial luminance and saturated luminance in the backlight unit, And controlling a current supplied to the backlight unit such that light having a uniform brightness is supplied from the backlight unit to the liquid crystal panel when a current other than the reference current is supplied to the backlight unit. Method of driving display device. The method of claim 1, When a first current higher than the reference current is to be supplied to the backlight unit, the current actually supplied to the backlight unit is set to be higher from the current lower than the first current to the first current. Driving method. The method of claim 2, And the current actually supplied to the backlight unit is controlled such that light having a luminance corresponding to the saturation luminance of the first current can be supplied from the backlight unit to the liquid crystal panel. The method of claim 1, When the first current lower than the reference current is to be supplied to the backlight unit, the current actually supplied to the backlight unit is set to be lowered from the current higher than the first current to the first current. Driving method. The method of claim 4, wherein And the current actually supplied to the backlight unit is controlled such that light having a luminance corresponding to the saturation luminance of the first current can be supplied from the backlight unit to the liquid crystal panel. A first step of checking a driving temperature of the liquid crystal display device; A second step of checking an elapsed time from a power input time of the liquid crystal display device; Checking a current to be supplied to the backlight unit; And a fourth step of determining an applied current to be actually supplied to the backlight unit in correspondence with the driving temperature, the elapsed time, and the current value to be supplied in the first and third steps. Driving method. The method of claim 6, And in the fourth step, the applied current to be actually supplied is set such that light having a luminance corresponding to the saturation luminance of the current value to be supplied can be generated in the backlight unit. And controlling a current value supplied to the backlight unit so that the initial luminance and the saturated luminance are uniformly maintained. Backlight unit, An inverter for supplying a driving current to the backlight unit; And a tube current controller for controlling the drive current to be supplied from the inverter to the backlight unit. The method of claim 9, The tube current controller An elapsed time controller for checking an elapsed time from a power input time of the liquid crystal display device; A temperature sensor for checking a driving temperature of the liquid crystal display; A memory in which an actual applied current to be actually supplied from the inverter to the backlight unit is stored corresponding to the elapsed time, the temperature sensor, and a current value to be supplied from the inverter to the backlight unit; And a control unit for extracting from the memory the actual applied current to be actually supplied from the backlight unit by using the information supplied from the elapsed time control unit, the temperature sensor, and the inverter. The method of claim 10, And a real applied current to be actually supplied from the inverter to the backlight unit in a look-up table corresponding to a predetermined temperature unit, a current unit, and the elapsed time. The method of claim 11, The actual applied current stored in the lookup table is set so that light of a luminance corresponding to a saturation luminance of a current value to be supplied from the inverter to the backlight unit can be generated in the backlight unit. Device. The method of claim 11, And the predetermined temperature unit is set between 1 ° C and 20 ° C. The method of claim 11, And the predetermined current unit is set between 0.1 mA and 5 mA. The method of claim 9, The tube current controller may control the current supplied from the inverter to the backlight unit so that light corresponding to the saturation luminance of the current to be supplied from the inverter to the backlight unit is generated in the backlight unit. Drive of the device.