KR20140086682A - Apparatus and method for driving of back light, display apparatus including the same - Google Patents

Abstract

A backlight driving apparatus according to the present invention which minimizes the color coordinate change of a backlight and improves light efficiency, comprises a backlight which includes light emitting diodes which are connected in series; a voltage supply unit which outputs a driving voltage generated according to the switching of a switching device; an amplitude control unit which controls the amplitude of the driving voltage outputted from the voltage supply unit and supplies the same to the backlight; and a backlight control unit which controls the voltage supply unit and the amplitude control unit to allow the backlight to operate with a DC driving mode or a pulse-width modulation driving mode based on a sensing current value corresponding to the driving voltage.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving apparatus, a driving method thereof, and a display apparatus using the same.

Back light is a light source that irradiates light to a display panel or a light guide plate for advertisement. In the past, cold cathode ray tube lamp (CCFL) was used as a light source. However, when a cold cathode ray tube lamp is used, , The response speed is about 15ms slow, and the color reproducibility is about 75% lower than that of NTSC. In addition, since a variety of problems occur, such as generating a predetermined white light, a light emitting diode (LED) device has become more popular as a light source in recent years.

The light emitting diode is eco-friendly as compared with the cold cathode tube lamp, has a response speed of several nanoseconds, is capable of high-speed response, is capable of impulse driving, and has a color reproducibility of 80% to 100% or more.

The light emitting diode may be driven by a direct current (DC) driving method or a pulse width modulation (PWM) method.

The direct current driving method is a method of varying the amplitude of the driving voltage supplied to the light emitting diode, and the pulse width modulation driving method is a method of varying the pulse width of the driving voltage having a fixed amplitude.

Meanwhile, the conventional backlight driving apparatus employs a pulse width modulation driving method which has an advantage that a light amount of a light emitting diode can be controlled rather than a direct current (DC) method, and the brightness of a backlight can be arbitrarily adjusted.

FIG. 1 is a graph showing changes in light efficiency according to currents in the direct current driving method and the pulse width modulation driving method, and FIG. 2 is a graph showing changes in the Y axis Cy in the color coordinates according to the currents in the direct current driving method and the pulse width modulation driving method. FIG.

1 and 2, when the light emitting diode is driven by the pulse width modulation driving method, the variation width of the Y axis Cy of the color coordinates of the light emitting diode according to the current flowing in the light emitting diode is small, (lm / W) is relatively low as compared with the direct current driving method.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a backlight driving apparatus and driving method capable of improving light efficiency while minimizing a change in color coordinates of a backlight, and a display device using the same.

Other features and advantages of the invention will be set forth in the description which follows, or may be obvious to those skilled in the art from the description and the claims.

According to an aspect of the present invention, there is provided a backlight driving apparatus including: a backlight including a plurality of light emitting diodes connected in series; A voltage supplier for outputting a driving voltage generated by switching of the switching device; An amplitude controller for adjusting the amplitude of the driving voltage output from the voltage supplier and supplying the adjusted amplitude to the backlight; And a backlight control unit for controlling the voltage supplying unit and the amplitude adjusting unit such that the backlight is driven by a DC driving method or a pulse width modulation driving method based on a sensing current value corresponding to the driving voltage. do.

Wherein the backlight control unit controls the voltage supply unit and the amplitude adjusting unit according to a backlight dimming signal so that the backlight is driven according to a direct current driving method when the sensed current value is equal to or greater than a set reference current value, And controls the voltage supply unit and the amplitude control unit according to the backlight dimming signal so that the backlight is driven according to the pulse width modulation driving scheme when the sensing current value is less than the set reference current value, And the width is adjusted.

According to an aspect of the present invention, there is provided a display device including: a display panel including a plurality of liquid crystal cells formed in regions defined by intersections of a plurality of gate lines and a plurality of data lines; A panel driver for analyzing input data from outside to generate a backlight dimming signal and displaying an image corresponding to the input data on the display panel; A backlight unit for emitting light to the display panel in accordance with driving of a backlight including a plurality of light emitting diodes connected in series; And the backlight driving device for driving the backlight.

According to an aspect of the present invention, there is provided a method of driving a backlight including a plurality of light emitting diodes connected in series, the method comprising: A) outputting a driving voltage in response to switching of a switching device; And (B) controlling the switching of the switching device and the amplitude of the driving voltage based on a sensing current value corresponding to the driving voltage to drive the backlight by a direct current driving method or a pulse width modulation driving method .

Wherein the step (B) controls the amplitude of the driving voltage according to the backlight dimming signal so that the backlight is driven according to the direct current driving method when the sensing current value is equal to or greater than the set reference current value, And adjusts the pulse width of the driving voltage according to the backlight dimming signal so that the backlight is driven according to the pulse width modulation driving scheme when the backlight is below the reference current value.

According to a preferred embodiment of the present invention, a backlight driving apparatus, a driving method, and a display apparatus using the same according to the present invention drive a backlight by a direct current driving method or a pulse width modulation driving method according to a magnitude of a current supplied to a backlight It is possible to improve the light efficiency while minimizing the color coordinate change of the backlight.

FIG. 1 is a diagram showing changes in light efficiency according to currents in a direct current driving method and a pulse width modulation driving method.
FIG. 2 is a diagram showing the Y axis (Cy) change of the color coordinate according to the currents of the direct current driving method and the pulse width modulation driving method.
3 is a view for explaining a backlight driving apparatus according to an embodiment of the present invention.
FIG. 4 is a waveform diagram showing the amplitude and pulse width variation of the driving voltage supplied to the backlight under the control of the backlight control unit shown in FIG. 3. FIG.
5 is a diagram for explaining a configuration of a backlight control unit according to an embodiment of the present invention.
6 is a flowchart illustrating a backlight driving method according to an embodiment of the present invention.
Fig. 7 is a diagram showing a change in light efficiency according to a current in the backlight driving device of the present invention. Fig.
FIG. 8 is a diagram showing a change in the Y axis (Cy) of the color coordinate according to the current in the backlight driving device of the present invention.

The meaning of the terms described herein should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

Hereinafter, preferred embodiments of a backlight driving apparatus and a display device including the same according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a view for explaining a backlight driving apparatus according to an embodiment of the present invention. FIG. 4 is a graph showing changes in amplitude and pulse width of a driving voltage supplied to the backlight according to the control of the backlight control unit shown in FIG. Fig.

3 and 4, the backlight driving apparatus 100 according to the embodiment of the present invention includes a voltage supply unit 120 for generating and outputting a driving voltage V _LED , or amplitude (AM _DC, AM of the driving voltage (V _LED) according to a control of the pulse width modulated backlight control unit 130, and a backlight control unit 130 for controlling the voltage supply 120 to be driven by a drive system _And an amplitude adjuster 140 for adjusting the _PWM .

The backlight 110 includes at least one light emitting diode LA having a plurality of light emitting diodes (LEDs) connected in series. The backlight 110 emits light having a predetermined luminance by emitting light from the LEDs due to the current flowing by the driving voltage V _LED from the voltage supply unit 120 to the image display panel, Or the light guide plate for advertisement.

The voltage supply unit 120 generates a driving voltage V _LED according to the switching control signal SCS of the backlight control unit 130 using the input voltage Vcc and supplies the driving voltage V _LED to the backlight 110. In one example, the voltage supply unit 120 includes an inductor L, a diode D, a capacitor C, and a switching element Psw. The voltage supply unit 120 having such a configuration outputs energy stored in the inductor L through the diode D in accordance with the switching of the switching element Psw and boosts the voltage through the capacitor C to generate the driving voltage V _LED . .

The inductor L is connected between the input voltage Vcc line and the first node N1 and stores a voltage corresponding to a change amount of the current by the input voltage Vcc.

The diode D is connected between the first node N1 and the output node No and rectifies and outputs a voltage supplied from the inductor L in accordance with switching of the switching element Psw. Here, the diode D is a reverse current prevention diode, and the voltage supplied from the inductor L is supplied to the output node N2.

The capacitor C charges the voltage supplied from the inductor L through the diode D according to switching of the switching element Psw or charges the charged voltage to the output node No with the driving voltage V _LED Output.

The switching element Psw is switched according to the switching control signal SCS supplied from the backlight control unit 130 so that the energy stored in the inductor L is charged in the capacitor C or the voltage charged in the capacitor C And is supplied to the backlight 110 as the driving voltage V _LED . At this time, the switching control signal SCS has a duty-on period and a duty-off period for turning on the switching element Psw, and the duty-on period is varied within a predetermined period Pulse width modulation signal.

The backlight control unit 130 is connected to the output node No of the voltage supply unit 120 and outputs a sensing current value Isensing corresponding to the driving voltage V _LED supplied from the voltage supply unit 120 to the backlight 110. [ And generates a switching element of the voltage supply unit 120 so that the backlight 110 is driven by a DC driving method or a pulse width modulation driving method based on the sensing current value Isensing and the set reference current value Iref Psw), and at the same time controls the amplitude adjusting unit 140. [0064] That is, when the sensing current value Isensing is equal to or greater than the reference current value Iref, the backlight controller 130 controls the switching element Psw of the voltage supplier 120 such that the backlight 110 is driven by the direct- The amplitude AM _DC of the driving voltage V _LED supplied to the backlight 110 is controlled by controlling the amplitude controller 140 according to the backlight dimming signal DIM supplied from the outside, . On the other hand, when the sensing current value Isensing is less than the reference current value Iref, the backlight control unit 130 controls the backlight 110 to be driven by the pulse width modulation driving method, The amplitude control unit 140 controls the amplitude of the driving voltage V _LED supplied to the backlight 110 to a predetermined reference amplitude AM _PWM .

The amplitude adjuster 140 adjusts the amplitude AM of the driving voltage V _LED supplied from the voltage supplier 120 according to the first or second amplitude setting signals ASS1 and ASS2 supplied from the backlight controller 130, _DC , and AM _PWM ).

More specifically, when the first amplitude setting signal ASS1 is supplied from the backlight control unit 130, the amplitude adjusting unit 140 adjusts the amplitude of the driving voltage V _LED according to the first amplitude setting signal ASS1 AM _DC ) to above the reference amplitude (AM _PWM ). On the other hand, when the second amplitude setting signal ASS2 is supplied from the backlight control unit 130, the amplitude of the driving voltage V _LED corresponding to the second amplitude setting signal ASS2 becomes the reference amplitude AM _PWM .

The amplitude adjuster 140 may include an operational amplifier 140a and a feedback voltage setting unit 140b.

The operational amplifier 140a includes a non-inverting terminal (+) to which the driving voltage V _LED is supplied from the voltage supply unit 120, an inverting terminal (-) to which the feedback voltage Vfb is supplied from the feedback voltage setting unit 140b, And an output terminal Vo connected to the back light 110. [ The operational amplifier 140a adjusts the voltage levels of the driving voltage V _LED , that is, the amplitudes AM _DC and AM _PWM based on the input driving voltage V _LED and the feedback voltage Vfb, .

The feedback voltage setting unit 140b adjusts the voltage level of the driving voltage V _LED fed back from the output terminal Vo of the operational amplifier 140a according to the first or second amplitude setting signals ASS1 and ASS2 And generates the feedback voltage Vfb and supplies the generated feedback voltage Vfb to the inverting terminal (-) of the operational amplifier 140a. For example, the feedback voltage setting unit 140b may include a plurality of parallel resistors (not shown) connected in parallel between the inverting terminal (-) of the operational amplifier 140a and the output terminal Vo, (Not shown) that selects either one of a plurality of parallel resistors according to the two amplitude setting signals ASS1 and ASS2 and generates a feedback voltage Vfb by adjusting a voltage level of a feedback driving voltage V _LED Lt; / RTI >

5 is a diagram for explaining a configuration of a backlight control unit according to an embodiment of the present invention.

3 to 5, a backlight control unit 130 according to an embodiment of the present invention includes a current sensing unit 131, a first comparison unit 133, a duty setting unit 135, an amplitude setting unit 137, and a switching control signal generator 139.

The current sensing unit 131 is connected to the output terminal Vo of the amplitude controller 140 and senses a current corresponding to the driving voltage V _LED supplied to the backlight 110, And supplies the value Isensing to the first comparator 133.

The first comparator 133 compares a sensing current value Isensing supplied from the current sensing unit 131 with a reference current value Iref to generate a comparison signal CS. That is, when the sensing current value Isensing is equal to or greater than the reference current value Iref, the first comparison unit 133 generates the first comparison signal CS1. When the sensing current value Isensing is greater than the reference current value Iref ), It generates the second comparison signal CS2.

The reference current value Iref is set to a minimum range in which a user or a person can recognize the light efficiency of the backlight 110 and the amount of change in the Y axis of the color coordinate system. The light efficiency of the backlight 110, Y axis change amount and the cognitive characteristics are measured and stored in the memory in advance.

Specifically, as shown in FIG. 1, the light emitting diode (LED) has a characteristic in which the Y-axis change amount of the light efficiency and the color coordinate decreases with an increase in the current value flowing therethrough. (Iref) is set. A method of setting the reference current value Iref will now be described.

First, after measuring the lower limit value (see "Cyl" in FIG. 8) of the Y axis variation amount of the color coordinate with respect to the maximum current value of the backlight 110 using the optical device, And the amount of change of the Y axis of the color coordinate according to the intensity of the electric current is measured and recorded. Next, the current value corresponding to the Y-axis change amount (see "Cyh" in Fig. 8) which is 0.008 or more from the lower limit value of the measured Y-axis change amount of the color coordinate is set as the reference current value Iref and is stored in the memory. Here, the reference current value Iref corresponds to the Y-axis change amount (see "Cyh " in Fig. 8) of 0.008 from the lower limit value of the Y-axis change amount of the color coordinate in consideration of the color coordinate recognition characteristic of the user or person sensitive to the color coordinate change amount As shown in FIG.

The duty setting unit 135 sets the duty ratio of the first or second duty setting voltage Vduty1 or Vduty2 based on the first comparison signal CS1 or the second comparison signal CS2 supplied from the first comparison unit 133, And supplies the generated first or second duty setting voltages Vduty1 and Vduty2 to the switching control signal generating unit 139. [

Specifically, when the first comparison signal CS1 is supplied from the first comparator 133, the duty setting unit 135 sets a first duty setting voltage (for example, Vduty1). On the other hand, when the second comparison signal CS2 is supplied from the first comparator 133, the duty setting unit 135 sets the duty ratio of the backlight 110 based on the backlight dimming signal DIM supplied from the outside, And a second duty setting voltage (Vduty2) for driving the first duty setting voltage (Vduty2) by a pulse width modulation driving method. Although the duty setting unit 135 generates the first and second duty setting voltages Vduty1 and Vuty2 for the convenience of explanation, the duty setting unit 135 substantially sets the duty ratio of the comparison signal CS1 , And CS2 and the backlight dimming signal DIM to generate one duty setting voltage whose voltage level is determined. For example, when the first comparison signal CS1 is supplied, the duty setting unit 135 sets the switching control signal SCS having the duty-on duration of 100% to be output from the switching control signal generating unit 139 And generates a duty setting voltage to be used. On the other hand, when the second comparison signal CS2 is supplied, the duty setting unit 135 outputs a switching control signal SCS having a duty-on duration of less than 100% corresponding to the backlight dimming signal DIM, And generates a duty setting voltage for outputting it from the control signal generating unit 139.

The amplitude setting unit 137 sets the amplitude of the driving voltage V _LED (s) supplied to the backlight 110 based on the first comparison signal CS1 or the second comparison signal CS2 supplied from the first comparison unit 133, (ASS1, ASS2) for controlling the amplitude controller 140 to generate the first or second amplitude setting signals ASS1, ASS2.

More specifically, when the first comparison signal CS1 is supplied from the first comparator 133, the amplitude setting unit 137 sets the amplitude of the driving voltage V _LED to the backlight dimming signal The amplitude control unit 140 generates a first amplitude setting signal ASS1 for adjusting the amplitude to the amplitude (AM _DC ) corresponding to the amplitude control signal DIM. On the other hand, when the second comparison signal CS2 is supplied from the first comparator 133, the amplitude setting unit 137 adjusts the amplitude of the driving voltage V _LED to a predetermined reference amplitude AM _PWM The second amplitude setting signal ASS2 for controlling the amplitude adjusting unit 140 is generated. Here, the reference amplitude (AM _PWM ) may be set equal to the minimum amplitude (AM _{DC - LOW} ) of the driving voltage (V _LED ) according to the direct current driving method.

The switching control signal generator 139 generates a switching control signal having a duty-on duration of 0% to 100% based on the first and second duty setting voltages Vduty1 and Vduty2 supplied from the duty setting unit 135, (SCS) to switch the switching element (Psw) of the voltage supply unit (120). To this end, the switching control signal generator 139 includes a triangle wave generator 139a and a second comparator 139b.

The triangle wave generator 139a generates a triangle wave CW having a constant frequency and supplies it to the second comparator 139b.

The second comparator 139b compares the duty-on and duty-off intervals according to the first and second duty setting voltages Vduty1 and Vduty2 supplied from the duty setting unit 135 based on the triangular wave CW, And supplies the control signal SCS to the switching unit Psw.

Specifically, when the first duty setting voltage Vduty1 is supplied, the second comparing unit 137b outputs a switching control signal SCS having a duty-on duration of 100% according to the first duty setting voltage Vduty1, And the switching element Psw of the voltage supply unit 120 is switched so that the driving voltage V _LED output from the voltage supply unit 120 becomes a direct current type. On the other hand, when the second duty setting voltage Vduty1 is supplied, the second comparing unit 137b outputs a switching control signal SCS having a duty-on duration of less than 100% according to the second duty setting voltage Vduty2, ) To switch the switching element Psw of the voltage supply unit 120 so that the driving voltage V _LED output from the voltage supply unit 120 becomes a pulse width modulation form.

6 is a flowchart illustrating a backlight driving method according to an embodiment of the present invention.

Referring to FIG. 6, a backlight driving method according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG.

First, a sensing current value Isensing is generated by sensing a current corresponding to a driving voltage V _LED supplied to the backlight 110 (S100).

Then, the sensing current value Isensing is compared with the set reference current value Iref (S110).

If the sensing current value Isensing is equal to or greater than the reference current value Iref ("Yes" in step S110), the amplitude of the driving voltage V _LED is controlled according to the backlight dimming signal supplied from the outside So that the backlight 100 is driven by the DC driving method (S120).

On the other hand, if it is determined in step S110 that the sensing current value Isensing is less than the reference current value Iref, the amplitude of the driving voltage V _LED is adjusted to the reference amplitude and at the same time, the driving voltage V _{And the} backlight 100 is driven by a pulse width modulation driving method (S130).

Subsequently, the above-described steps S100 to S130 are repeatedly performed to control the backlight 110 according to the magnitude (or intensity) of the sensing current value Isensing according to the driving voltage V _LED supplied to the backlight 110. [ Is driven by a direct current driving method or a pulse width modulation driving method.

FIG. 8 is a graph showing the change in the Y-axis (Cy) of the color coordinate according to the current in the backlight driving apparatus according to the present invention. FIG.

7 and 8, the backlight driving device and the driving method according to the present invention drive the backlight by the direct current driving method or the pulse width modulation driving method according to the magnitude of the current supplied to the backlight, The light efficiency (lm / W) is improved (hatched region in FIG. 7) in comparison with the pulse width modulation driving system and the difference (Cyh-Cyl) between the Y-axis vertical change amount Cyh and the lower limit change amount Cyl 0.005, and the amount of Y-axis change of the color coordinate is within a range not recognized by the user.

9 is a view for explaining a display device according to an embodiment of the present invention.

9, a display device according to an exemplary embodiment of the present invention includes a display panel 300, a panel driver 400, a backlight unit 500, and a backlight driver 600.

The display panel 300 includes a plurality of pixels P formed in regions defined by a plurality of gate lines GL and a plurality of data lines DL.

Each of the plurality of pixels P includes a thin film transistor (not shown) connected to the gate line GL and the data line DL, and a liquid crystal cell connected to the thin film transistor.

The display panel 300 displays an image by controlling the transmittance of light emitted from the backlight unit 500 by forming an electric field in the liquid crystal cell according to the data voltage supplied to each pixel P. [

The panel driving unit 400 includes a data driving circuit unit 410, a gate driving circuit unit 420, and a timing control unit 430.

The data driving circuit unit 410 latches the data signals R, G, and B input from the timing control unit 430 according to the data control signal DCS supplied from the timing controller 430, Converts the latched data signal to a positive / negative analog pixel voltage using a polarity gamma voltage, generates a pixel voltage having a polarity corresponding to the polarity control signal, and supplies the pixel voltage to the data lines DL.

The gate driving circuit 420 generates a gate signal according to a gate control signal GCS supplied from the timing controller 430 and sequentially supplies the gate signal to the gate lines GL. Here, the gate driving circuit part 420 may be formed on the substrate simultaneously with the formation of the thin film transistor.

The timing controller 430 arranges input data (RGB) input from the outside to be suitable for driving the display panel 300 and supplies the input data RGB to the data driving circuit unit 410.

The timing control unit 430 receives the data control signal DCS and the gate control signal DCS for controlling the operation timings of the data driving circuit unit 410 and the gate driving circuit unit 420 using the input timing synchronization signal TSS, (GCS). Here, the timing synchronization signal TSS is a vertical synchronization signal Vsync; A horizontal synchronizing signal Hsync; A data enable signal (Data Enable); And a dot clock (DCLK). The data control signal DCS includes a source start pulse (Source Start Pulse); A source sampling clock; Source Output Enable; And a polarity control signal POL. The gate control signal GCS includes a gate start pulse (Gate Start Pulse); A gate shift clock; And gate output enable (Gate Output Enable).

The timing controller 430 generates a backlight dimming signal DIM for controlling the brightness of the backlight unit 500 according to the brightness of the image of one frame and supplies the backlight dimming signal DIM to the backlight unit 500. Here, the timing controller 430 analyzes the input data (RGB) of one frame, calculates an average image level, and generates a backlight dimming signal (DIM) according to the calculated average image level. For example, when the image of one frame is determined as a relatively bright image according to the average image level, a backlight dimming signal DIM for reducing the brightness of the backlight unit 500 is generated, The backlight dimming signal DIM for increasing the brightness of the backlight unit 500 can be generated when the image of one frame is determined to be a relatively dark image.

The backlight unit 500 irradiates light to the display panel 300 using light emission of a plurality of light emitting diodes. The backlight unit 500 includes at least one light emitting diode array including a plurality of light emitting diodes (LEDs) connected in series. Here, the backlight unit 500 may be an edge-type backlight unit or a direct-type backlight unit.

The backlight driving unit 60 drives the backlight unit 500, that is, the light emitting diode array based on the backlight dimming signal DIM. And thus it is configured in the same manner as the backlight driving apparatus 100 according to the embodiment of the present invention, so that a duplicate description thereof will be omitted.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

110: backlight 120: voltage supply unit
130: back light control unit 131: current sensing unit
133: first comparison unit 135: duty setting unit
137: amplitude setting unit 139: switching control signal generating unit
140: amplitude adjuster 300: display panel
400: panel driver 410: data driver
420: Gate driving circuit part 430: Timing control part
500: backlight unit 600: backlight driving unit

Claims (10)

A backlight including a plurality of light emitting diodes connected in series;
A voltage supplier for outputting a driving voltage generated by switching of the switching device;
An amplitude controller for adjusting the amplitude of the driving voltage output from the voltage supplier and supplying the adjusted amplitude to the backlight; And
And a backlight control unit for controlling the voltage supplying unit and the amplitude adjusting unit such that the backlight is driven by a DC driving method or a pulse width modulation driving method based on a sensing current value corresponding to the driving voltage. Backlight driving device. The method according to claim 1,
The backlight control unit
Controlling the amplitude of the driving voltage by controlling the voltage supply unit and the amplitude adjusting unit according to a backlight dimming signal so that the backlight is driven according to a direct current driving method when the sensing current value is equal to or greater than a set reference current value,
And controlling the voltage supply unit and the amplitude control unit according to the backlight dimming signal so that the backlight is driven according to the pulse width modulation driving scheme when the sensing current value is less than the set reference current value, And the backlight driving device. 3. The method of claim 2,
Wherein the amplitude of the driving voltage according to the pulse width modulation driving method is equal to the minimum amplitude of the driving voltage according to the direct current driving method. 3. The method of claim 2,
Wherein the reference current value is set to a current value of 0.008 or more from the Y-axis lower limit change amount of the Y coordinate of the color coordinate according to the current of the backlight. 3. The method of claim 2,
A current sensing unit for generating a sensing current corresponding to the driving voltage;
A comparison unit for comparing the sensed current value with a set reference current value to generate a comparison signal;
A duty setting unit for generating a duty setting voltage corresponding to the backlight dimming signal based on the comparison signal;
An amplitude setting unit for generating an amplitude setting signal corresponding to the backlight dimming signal based on the comparison signal and supplying the amplitude setting signal to the amplitude adjusting unit; And
And a switching control signal generator for generating a switching control signal having a duty-on duration ranging from 0 to 100% according to the duty setting voltage to switch the switching device. A display panel including a plurality of liquid crystal cells formed in regions defined by intersections of a plurality of gate lines and a plurality of data lines;
A panel driver for analyzing input data from outside to generate a backlight dimming signal and displaying an image corresponding to the input data on the display panel;
A backlight unit for emitting light to the display panel in accordance with driving of a backlight including a plurality of light emitting diodes connected in series; And
The display device according to any one of claims 1 to 5, wherein the backlight is driven. A backlight driving method comprising a plurality of light emitting diodes connected in series,
A step (A) of outputting a driving voltage in accordance with switching of a switching element; And
(B) controlling the switching of the switching element and the amplitude of the driving voltage based on a sensing current value corresponding to the driving voltage to drive the backlight by a direct current driving method or a pulse width modulation driving method And a backlight driving method. 8. The method of claim 7,
The step (B)
And controlling the amplitude of the driving voltage according to a backlight dimming signal so that the backlight is driven according to a direct current driving method when the sensing current value is equal to or greater than a set reference current value,
Wherein the pulse width of the driving voltage is adjusted according to the backlight dimming signal so that the backlight is driven according to the pulse width modulation driving scheme when the sensing current value is less than the set reference current value. 9. The method of claim 8,
Wherein the amplitude of the driving voltage according to the pulse width modulation driving method is equal to the minimum amplitude of the driving voltage according to the direct current driving method. 10. The method of claim 9,
Wherein the reference current value is set to a current value of 0.008 or more from the Y-axis lower limit change amount of the Y coordinate of the color coordinate according to the current of the backlight.

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