KR20130016897A - Driving integrated circuit for backlight driver and liquid crystal display device including the same - Google Patents

Abstract

PURPOSE: A driving integrated circuit for a backlight driver and a liquid crystal display device including the same are provided to implement a scanning operation by receiving a plurality of PWM signals to drive a plurality of LED blocks according to a channel and giving different delay time according to the channel. CONSTITUTION: A PWM dimming signal is inputted through a plurality of PWM terminals(PWM1-PWM6). A PWM dimming signal is transmitted to a PWM control unit. The output of the PWM control unit controls each comparator. Drains of a plurality of transistors are connected to a plurality of LED blocks through a plurality of out terminals(LED1-LED6). Gates of the plurality of transistors are connected to output terminals of a plurality of comparators. Sources of the plurality of transistors are connected to the ends of a plurality of resistors(R1-R6). Each comparator compares a reference voltage with a sampling voltage in the end of the resistor. The plurality of transistors control currents flowing in the plurality of LED blocks according to an output voltage of the comparator.

Description

A driving integrated circuit for a backlight driver and a liquid crystal display including the same. {DRIVING INTEGRATED CIRCUIT FOR BACKLIGHT DRIVER AND LIQUID CRYSTAL DISPLAY DEVICE INCLUDING THE SAME}

The present invention relates to a driving integrated circuit for a backlight driver, and more particularly, to a driving integrated circuit for a backlight driver for driving a plurality of LEDs for each channel by receiving a plurality of PWM signals and a liquid crystal display including the same.

Recently, as the information society develops, the demand for the display field is increasing in various forms, and in response, various flat panel display devices, for example, liquid crystal, which have features such as thinning, light weight, and low power consumption Liquid crystal display devices, plasma display panel devices, electroluminescent display devices, and the like have been studied.

Among these, the liquid crystal display is one of the most widely used flat panel display devices, and includes two substrates on which pixel electrodes, a common electrode, and the like are formed, and a liquid crystal layer between the two substrates.

Such a liquid crystal display determines an orientation of liquid crystal molecules of a liquid crystal layer according to an electric field generated by a voltage applied to an electrode, and controls polarization of incident light to display an image.

In addition, the liquid crystal display device is advantageous for moving image display and replaces a conventional cathode ray tube due to a high contrast ratio, and not only a display device (laptop monitor, etc.) of a mobile terminal, but also a computer monitor, a television, etc. It is used in various ways.

The liquid crystal display device does not have its own light emitting element, so a separate light source must be provided. A backlight unit having a light source is disposed on the back of the liquid crystal display, and light is directed to the front of the liquid crystal panel through the backlight unit. As it is irradiated, an image of identifiable luminance may be realized.

Here, a cold cathode fluorescent lamp, an external electrode fluorescent lamp, a light emitting diode (LED), or the like is used as a light source of the backlight unit.

Among them, LEDs are particularly widely used as light sources for displays because of their small size, low power consumption, and high reliability. A description with reference to the drawings below.

1 is a diagram showing a driving integrated circuit of a conventional backlight driver, and FIG. 2 is a diagram referred to for explaining driving of a driving integrated circuit of a conventional backlight driver.

As shown in Fig. 1, the driving integrated circuit of the conventional backlight driver is composed of a plurality of terminals including one PWM terminal DIM and four OUT terminals OUT1, OUT2, OUT3, and OUT4.

Here, the PWM terminal DIM is a terminal for receiving a PWM dimming signal for adjusting the brightness of the backlight unit, and the PWM dimming signal is generally transmitted from a timing controller (not shown).

The first to fourth OUT terminals OUT1, OUT2, OUT3, and OUT4 are terminals connected to one ends of the first to fourth LED strings (not shown), respectively, and current flowing through the first to fourth LED strings. It is connected internally with a transistor to control it.

In this case, the first to fourth LED strings are connected in parallel, and each of the first to fourth LED strings may have a form in which a plurality of LEDs (Light Emitting Diodes) are connected in series.

Referring to the operation of the driving integrated circuit of the conventional backlight driver, as shown in FIG. 2, the PWM dimming signal input from the PWM terminal DIM is transferred to the logic unit Logic, The two switches can be turned on by the output.

Meanwhile, the drain of the transistor T is connected to the first to fourth LED strings through the respective OUT terminals OUT1, OUT2, OUT3, and OUT4, and the gate of the transistor T is connected to the output terminal of the comparator 52. .

The source of the transistor T is connected to the resistor R, and the other end of the resistor R is connected to the ground through the LEDGND terminal.

The comparator 52 compares the sampling voltage of one end of the resistor R according to the current of the first to fourth LED strings with the reference voltage Vref, and the transistors T are respectively set according to the output voltage of the comparator 52. Adjust the current flowing through each of the first to fourth LED strings

For example, when the current of the first to fourth LED strings is lower than the reference current, the voltage drop at the resistor R is small, and thus the sampling voltage at one end of the resistor R is lowered.

The comparator 52 compares the reference voltage Vref with the lowered sampling voltage of one end of the resistor R to control the transistor T so that a larger current flows, thereby increasing the current of the first to fourth LED strings. Can be.

On the other hand, when the current of the first to fourth LED string is higher than the reference current, the comparator 52 operates in the opposite direction to control the transistor T so that a smaller current flows, thereby the first to fourth LED string. Can reduce the current.

As a result, the comparator 52, the transistor T, and the resistor R may serve as a constant current source to allow a uniform current to flow through the first to fourth LED strings.

FIG. 3 is a diagram schematically showing a backlight of a conventional liquid crystal display, and FIG. 4 is a diagram showing a current flowing through each of the first to fourth LED strings of a conventional backlight, and FIG. It is a figure referred to for explaining the driving of the first to fourth LED strings.

As shown in FIG. 3, the backlight of the conventional liquid crystal display device includes first to fourth LED strings L1 to L4 in which a plurality of LEDs are connected in series, and the backlight driver drives each string. It consists of the first to fourth channels for.

Here, the first to fourth LED strings L1 to L4 may be disposed in parallel with the lower portion of the liquid crystal panel (not shown).

Since the driving integrated circuit of the conventional backlight driver drives the first to fourth LED strings L1 to L4 using one PWM signal, as shown in FIG. 4, the first to fourth LED strings L1. Through L4) are the same.

Accordingly, the first to fourth LED strings L1 to L4 are driven the same, and as shown in FIG. 5, the luminance of all screens of the liquid crystal display is equally implemented.

As such, the conventional backlight driver operates by using a single pulse width modulation (PWM) signal or controls only a single phase shift fixed at the time of design. Local Dimming was difficult to implement.

Therefore, since the duty ratio and delay time of the PWM for driving all the LED strings are the same, there is a problem that a motion blur phenomenon occurs.

In addition, since only global dimming to adjust the brightness of the full screen of the liquid crystal display device is possible regardless of the partial brightness of the image data, there is a problem in that contrast ratio is reduced and power consumption is increased. .

Meanwhile, in order to implement scanning operation and local dimming function, a backlight driver driving integrated circuit using multiple driving integrated circuits or a micro controller unit (MCU) IC and capable of I2C and SPI communication is required. did.

Therefore, there is a problem that the manufacturing cost increases due to the use of additional components.

The present invention has been made in view of the above-described problems, and a driving integrated circuit for driving a backlight driver for driving a plurality of LEDs received with a plurality of PWM signals through a plurality of PWM input terminals for each channel and a liquid crystal display including the same The purpose is to provide.

The driving integrated circuit of the backlight driver for achieving the above object comprises: first to Nth output terminals connected to one end of each of the first to Nth (N is an arbitrary natural number) light emitting diode blocks; First to Mth (M is any natural number) PWM terminal for receiving a plurality of pulse width modulation signal input, and using the plurality of pulse width modulation signal to the first to Nth LED block for each channel It is characterized by driving.

Here, the first to N-th comparator for outputting the output voltage by comparing the sampling voltage and the reference voltage; The apparatus may further include first to Nth switching elements controlled by the output voltages of the first to Nth comparators.

The gates of the first to Nth switching elements are connected to output terminals of the first to Nth comparators, respectively, and the drains of the first to Nth switching elements are connected to the first to Nth output terminals, respectively. The sources of the first to Nth switching elements may be connected to one ends of the first to Nth sampling resistors, respectively.

The sampling voltage may be a voltage generated at one end of the first to Nth sampling resistors by a current of each of the first to Nth LED blocks.

The other end of the first to Nth sampling resistors may be connected to ground through an LED ground terminal.

According to an aspect of the present invention, there is provided a liquid crystal display including: a backlight including first to Nth light emitting diode blocks (where N is an arbitrary natural number); And a backlight driver for driving the backlight, wherein the backlight driver includes first to Nth output terminals respectively connected to one end of the first to Nth LED blocks, and receives a plurality of pulse width modulated signals. The first to Mth (M is an arbitrary natural number) PWM terminals are configured, and the first to Nth LED blocks are driven for each channel using the plurality of pulse width modulation signals.

In this case, a scanning operation may be implemented by giving a delay time for each channel by the plurality of pulse width modulation signals.

In addition, a local dimming operation may be implemented by giving a different PWM duty ratio for each channel by the plurality of pulse width modulation signals.

The backlight driver may include: first to N th comparators configured to compare a sampling voltage and a reference voltage to output an output voltage; The apparatus may further include first to Nth switching elements controlled by the output voltages of the first to Nth comparators.

The gates of the first to Nth switching elements are connected to output terminals of the first to Nth comparators, respectively, and the drains of the first to Nth switching elements are connected to the first to Nth output terminals, respectively. Preferably, the sources of the first to Nth switching elements are connected to one ends of the first to Nth sampling resistors, respectively.

Here, the other end of the first to Nth sampling resistors may be connected to ground through an LED ground terminal.

The sampling voltage may be a voltage generated at one end of the first to Nth sampling resistors by a current of each of the first to Nth LED blocks.

As described above, the backlight driver integrated circuit may include a plurality of PWM terminals so as to correspond to the plurality of LED blocks, and may receive a plurality of PWM signals for driving the plurality of LED blocks per channel through each PWM terminal. .

As a result, scanning operation can be implemented by different delay time for each channel, and motion blur can be improved.

In addition, different PWM duty ratios are provided for each channel to implement a local dimming operation and to improve power consumption and contrast ratio.

Meanwhile, only one backlight driver integrated circuit can implement a scanning operation and a local dimming operation, thereby improving integration and reducing manufacturing costs.

1 is a diagram illustrating a driving integrated circuit of a conventional backlight driver.
2 is a view referred to for explaining the driving of the driving integrated circuit of the conventional backlight driver.
3 is a view schematically illustrating a backlight of a conventional liquid crystal display device.
4 is a diagram illustrating a current flowing through each of the first to fourth LED strings of the conventional backlight.
5 is a view referred to to explain driving of the first to fourth LED strings of the conventional backlight.
6 is a schematic view of a liquid crystal display according to an exemplary embodiment of the present invention.
7 is a diagram illustrating a driving integrated circuit of a backlight driver according to an exemplary embodiment of the present invention.
FIG. 8 is a diagram referred to for describing driving of a driving integrated circuit of a backlight driver according to an exemplary embodiment of the present invention.
9 is a diagram schematically illustrating a delay time of a PWM signal for driving a plurality of LED blocks according to an embodiment of the present invention.
FIG. 10 is a diagram referred to for describing a scanning operation of a backlight according to an exemplary embodiment of the present invention. FIG.
FIG. 11 is a diagram schematically illustrating a duty ratio of a PWM signal for driving a plurality of LED blocks according to an embodiment of the present invention.
12 is a diagram referred to describe a local dimming operation of a backlight according to an embodiment of the present invention.
13 and 14 are views referred to for explaining improvement of a motion blur phenomenon according to a scanning operation of a backlight.
15 and 16 are views referred to for explaining image quality improvement according to a local dimming operation of a backlight.

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

6 is a schematic view of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 6, the liquid crystal display device 100 according to the present invention includes a liquid crystal panel 110, a data driver 120, a gate driver 130, a data driver 120, and a gate driver 130, respectively. The timing controller 140 may control a driving timing of the backlight unit, and may include a backlight unit including the backlight 160 and the backlight driver 150.

The liquid crystal panel 110 may include a plurality of subpixel regions SP in which a plurality of gate lines GL and a plurality of data lines DL intersect each other, and include a plurality of subpixel regions SP. The thin film transistor T connected to the gate line GL and the data line DL, the storage capacitor Cst connected to the thin film transistor T, and the liquid crystal cell Clc are formed.

Here, the plurality of subpixel areas SP may be, for example, red, green, and blue subpixel areas SP, and may be sequentially disposed in the horizontal direction (horizontal direction) or the vertical direction (vertical direction). have.

In the liquid crystal panel 110, pixel regions including red, green, and blue pixel regions SP may be arranged in a matrix form of M ㅧ N (where M and N are arbitrary natural numbers).

When the thin film transistor T receives a gate signal, that is, a gate high voltage VGH, through the gate line GL, the thin film transistor T is turned on to transmit data to the liquid crystal cell Clc through the data line DL. When the signal is supplied and the gate low voltage VGL is supplied through the gate line GL, the signal is turned off.

The liquid crystal cell Clc is equivalently represented by a capacitor and includes a common electrode (not shown) facing the liquid crystal with a liquid crystal interposed therebetween and a pixel electrode (not shown) connected to the thin film transistor T.

The liquid crystal cell Clc realizes gradation by adjusting the light transmittance by changing the arrangement state of the liquid crystals according to the data signal charged through the thin film transistor T.

The storage capacitor Cst maintains the data signal charged in the liquid crystal cell Clc until the next frame.

The data driver 120 may include at least one driver IC (not shown) for supplying a data signal to the liquid crystal panel 110.

The data driver 120 includes a driver such as a converted image signal R / G / B, a source start pulse SSP, a source shift clock SSC, a source output enable SOE, etc. received from the timing controller 140. A data signal is generated using an IC control signal, and the generated data signal is supplied to the liquid crystal panel 110 through a plurality of data lines DL.

The timing controller 140 uses a low voltage differential signal (LVDS) interface to output a plurality of image signals, a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), and a data enable signal (DE) from a system such as a graphics card. A plurality of control signals such as) can be received.

The timing controller 140 may generate a gate control signal GCS for controlling the gate driver 130 and a data control signal DCS for controlling the data driver 120 using a plurality of control signals. Can be.

The gate control signal GCS may include a gate start pulse, a gate shift clock, a gate output enable signal, and the like, and a data control signal DCS. ) May include a source start pulse, a source shift clock, a source output enable, and the like.

In this case, a low voltage differential signal (LVDS) interface includes an LVDS transmitter (not shown) for converting a plurality of video signals and a plurality of control signals received from a system into LVDS signals, and a LVDS signal from the LVDS transmitter. It may include an LVDS receiver (not shown) receiving a plurality of converted N-bit image signal and a plurality of control signals.

Here, the LVDS transmitter may be embedded in the system, and the LVDS receiver may be embedded in the timing controller 140.

The timing controller 140 may generate a backlight control signal BCS for controlling the backlight driver 150 or a PWM dimming signal for controlling the brightness of the backlight 160.

For example, the timing controller 140 receives a global dimming value from a system such as a graphics card, analyzes the input image in units of blocks of an image corresponding to the LED block size of the backlight unit, and analyzes the input image. You can create local dimming values accordingly.

The gate driver 130 may be formed by a gate in panel (GIP) method, and generates a gate signal using a plurality of gate control signals received from the timing controller 140, and generates a plurality of gate signals. It may be controlled to supply the liquid crystal panel 110 through the wiring GL.

Although not shown, it may further include a gamma voltage generation circuit (not shown) and a power supply circuit (not shown). The gamma voltage generation circuit generates a plurality of gamma voltages by dividing a high potential voltage and a low potential voltage, This may be supplied to the data driver 140.

The power supply circuit may generate and supply a driving voltage for driving the components of the liquid crystal display device 100 using the power voltage received from the outside.

The backlight driver 150 generates a driving voltage and a driving current and supplies the driving voltage and the driving current to the backlight 160, and includes a driving integrated circuit that controls the driving voltage and the driving current according to the current flowing through each of the plurality of LED blocks of the backlight 160. can do.

In addition, the backlight driver 150 generates a PWM signal having a duty ratio of 0 to 100% according to the plurality of PWM dimming signals from the timing controller 140, and uses the generated PWM signal to generate an LED block (channel). Can be driven for each channel.

In addition, the backlight driver 150 may vary the delay time of the plurality of PWM signals for controlling the plurality of LED blocks according to the duty ratio of each PWM signal.

For example, the PWM controller (not shown) generates a PWM signal having a duty ratio of 0 to 100% using a plurality of PWM dimming signals, and delay time of the plurality of PWM signals according to the duty ratio of each PWM signal. Can be changed in various ways.

The backlight 160 serves to supply light to the liquid crystal panel 110. For example, the backlight 160 may be a direct type backlight provided under the liquid crystal panel 110 to supply light.

The backlight 160 may be configured as an LED block (not shown) in which a plurality of LEDs are bundled. For example, the backlight 160 may be configured as a plurality of LED strings (L1 to L4 of FIG. 3) in which a plurality of LEDs are connected in series. . Such an LED block may be driven for each channel by the PWM signal generated by the backlight driver 150.

Here, the PWM signal is a signal for adjusting the on / off time of the plurality of LEDs constituting the LED block, the emission time of the plurality of LEDs and the amount of current flowing to the plurality of LEDs according to the duty ratio of the PWM signal. This can be adjusted.

For example, the emission time of a plurality of LEDs driven by a PWM signal having a high duty ratio may be long, and the emission time of a plurality of LEDs driven by a PWM signal having a high duty ratio may be short.

The duty ratio of the PWM signal may be determined by the PWM dimming signal received from the timing controller 140.

The driving integrated circuit of the backlight driver will be described with reference to the drawings.

7 is a diagram illustrating a driving integrated circuit of a backlight driver according to an embodiment of the present invention, and FIG. 8 is a view referred to for explaining driving of the driving integrated circuit of a backlight driver according to an embodiment of the present invention. Although the number of PWM terminals is described as eight, for example, the present invention is not limited thereto and can be variously adjusted. The number of PWM terminals and OUT terminals may be different.

As shown in FIG. 7, the driving integrated circuit of the backlight driver is composed of a plurality of terminals including a plurality of PWM terminals PWM1 to PWM8 and a plurality of OUT terminals LED1 to LED8.

Here, the plurality of PWM terminals PWM1 to PWM8 are terminals for receiving a plurality of PWM dimming signals for adjusting the brightness of the backlight unit, and the plurality of PWM dimming signals are generally transmitted from the timing controller 140 (FIG. 6). I can receive it.

The plurality of OUT terminals LED1 to LED8 are terminals respectively connected to one ends of a plurality of LED blocks (not shown), and a plurality of transistors T1 to T6 are internally used to control current flowing through the plurality of LED blocks. ) Is associated with each.

Here, the plurality of LED blocks may be, for example, in the form of a plurality of LED strings (L1 to L4 of FIG. 3) in which a plurality of LEDs are connected in series.

Referring to the operation of the driving integrated circuit of the backlight driver, as shown in FIG. 8, the PWM dimming signal input through the plurality of PWM terminals PWM1 to PWM6 is transmitted to a PWM controller (not shown), and the PWM controller. The output (multiple PWM signals) of (not shown) can control each comparator.

Meanwhile, drains of the plurality of transistors T1 to T6 are connected to the plurality of LED blocks through the plurality of OUT terminals LED1 to LED6, and gates of the plurality of transistors T1 to T6 are connected to the plurality of comparators OP1 to OP6. Are respectively connected to the output terminal.

Each of the sources of the plurality of transistors T1 to T6 is connected to one end of the plurality of resistors R1 to R6, respectively, and the other end of the plurality of resistors R1 to R6 is connected to the ground through the LEDGND terminal.

Each comparator compares a sampling voltage and a reference voltage (Vref) of a plurality of resistors (R1 to R6) according to the current flowing in the plurality of LED blocks, and the plurality of transistors (T1 to T6) according to the output voltage of the comparator The current flowing in each LED block can be adjusted.

For example, when the current flowing in the plurality of LED blocks is lower than the reference current, the voltage drop at the first resistor R1 is reduced, thereby lowering the sampling voltage at one end of the first resistor R1.

The comparator compares the reference voltage Vref with the lowered sampling voltage of the resistor R to control the plurality of transistors T1 to T6 so that a larger current flows, thereby increasing the current flowing through the plurality of LED blocks. have.

On the other hand, when the current flowing in the plurality of LED blocks is higher than the reference current, the comparator operates in the opposite manner to control the plurality of transistors T1 to T6 so that a smaller current flows, thereby controlling the current flowing in the plurality of LED blocks. Can be reduced.

As a result, the plurality of comparators, the plurality of transistors T1 to T6, and the plurality of resistors R1 to R6 may serve as constant current sources that allow a uniform current to flow through the plurality of LED blocks.

FIG. 9 is a view schematically showing a delay time of a PWM signal for driving a plurality of LED blocks according to an embodiment of the present invention, and FIG. 10 is a reference for explaining a scanning operation of a backlight according to an embodiment of the present invention. It is a drawing.

As shown in FIG. 9, a plurality of PWM signals for driving a plurality of LED blocks (channels) for each channel may be input with different delay times DT1 to DT4, respectively.

That is, the plurality of PWM signals may be input after being sequentially delayed by the first delay time to the fourth delay time DT1 to DT4 based on the time point at which the vertical synchronization signal Vsync is applied.

As a result, the plurality of LED blocks (channels) of the backlight unit emit light while sequentially delaying the first to fourth delay times DT1 to DT4 for each channel, as shown in FIG. 10. The scanning operation may be implemented to drive the light emission time differently. Although not shown, the LED block may emit light at the same time.

FIG. 11 is a view schematically showing a duty ratio of a PWM signal for driving a plurality of LED blocks according to an embodiment of the present invention, and FIG. 12 is a diagram for describing a local dimming operation of a backlight according to an embodiment of the present invention. Reference is made to the drawing. Here, although four sections are shown as an example, the present invention is not limited thereto, and local dimming operations may be implemented by dividing the four sections into four or more sections.

As illustrated in FIG. 11, a PWM signal for driving a plurality of LED blocks for each channel may have first to fourth duty ratios DR1 to DR4.

In addition, the emission time of the LEDs of the plurality of LED blocks may be adjusted by the first to fourth duty ratios DR1 to DR4 of the PWM signal.

That is, the emission time of the plurality of LEDs may be adjusted according to the duty ratio of the PWM signal. For example, the first to fourth duty ratios DR1 to DR4 may be 40%, 99%, 50%, and 20%, respectively. As shown in FIG. 12, luminance may vary due to a difference in LED emission time for each LED block (channel).

In other words, since the LED emission time is shortened for each LED block (channel) in the order of 99%, 50%, 40%, and 20%, the luminance is lowered.

As a result, it is possible to implement a local dimming operation in which the luminance is changed for each LED block (channel).

13 and 14 are views for explaining the improvement of the motion blur phenomenon according to the scanning operation of the backlight, and FIGS. 15 and 16 are referred to for explaining the improvement of the image quality according to the local dimming operation of the backlight. Drawing.

Referring to FIGS. 13 and 14, it can be seen that the motion blur phenomenon is improved by implementing a scanning operation to change the light emission point for each LED block (channel).

15 and 16, a contrast ratio may be improved by dividing an input image into a dark section and a bright section to control each section to be driven by a PWM signal having a different duty ratio. .

In addition, power consumption can be improved by dividing the light emission time of a plurality of LEDs into a dark section and a bright section.

In other words, the contrast ratio and power consumption may be improved by dividing the input image into a dark section and a bright section to drive the brighter part brighter and the darker part darker.

The embodiments of the present invention as described above are merely illustrative, and those skilled in the art can make modifications without departing from the gist of the present invention. Accordingly, the protection scope of the present invention includes modifications of the present invention within the scope of the appended claims and equivalents thereof.

100: liquid crystal display 110: liquid crystal panel
120: Data driver 130: Gate driver
140: timing controller 150: backlight driver
160: backlight

Claims (12)

First to Nth output terminals connected to one end of each of the first to Nth light emitting diode blocks (where N is an arbitrary natural number);
A first through Mth (M is any natural number) PWM terminals for receiving a plurality of pulse width modulated signals,
And driving the first to Nth LED blocks for each channel by using the plurality of pulse width modulated signals.
The method of claim 1,
First to Nth comparators configured to compare the sampling voltage and the reference voltage to output an output voltage;
First to Nth switching elements controlled by output voltages of the first to Nth comparators
Drive integrated circuit for a backlight driver further comprises.
The method of claim 2,
Gates of the first to Nth switching elements are connected to output terminals of the first to Nth comparators, respectively.
The drains of the first to Nth switching elements are connected to the first to Nth output terminals, respectively.
And a source of the first to Nth switching elements is connected to one end of the first to Nth sampling resistors, respectively.
The method of claim 2,
The sampling voltage is,
And a voltage generated at one end of the first to Nth sampling resistors by a current of each of the first to Nth LED blocks.
The method of claim 3,
And the other end of the first to Nth sampling resistors is connected to ground through an LED ground terminal.
A backlight comprising first to Nth (N is any natural number) light emitting diode blocks;
A backlight driver for driving the backlight;
The backlight driver,
First to Nth output terminals connected to one end of each of the first to Nth LED blocks, and first to Mth PWM terminals (M are arbitrary natural numbers) for receiving a plurality of pulse width modulation signals. ,
And driving the first to Nth LED blocks for each channel by using the plurality of pulse width modulation signals.
The method according to claim 6,
By the plurality of pulse width modulated signals
And a delay time for each channel to implement a scanning operation.
The method according to claim 6,
By the plurality of pulse width modulated signals
And varying the PWM duty ratio for each channel to implement a local dimming operation.
The method according to claim 6,
The backlight driver,
First to Nth comparators configured to compare the sampling voltage and the reference voltage to output an output voltage;
First to Nth switching elements controlled by output voltages of the first to Nth comparators
Liquid crystal display device further comprising.
10. The method of claim 9,
Gates of the first to Nth switching elements are connected to output terminals of the first to Nth comparators, respectively.
The drains of the first to Nth switching elements are connected to the first to Nth output terminals, respectively.
The source of the first to Nth switching elements is connected to one end of the first to Nth sampling resistor, respectively.
The method of claim 10,
And the other end of the first to Nth sampling resistors is connected to the ground through an LED ground terminal.
10. The method of claim 9,
The sampling voltage is,
And a voltage generated at one end of the first to Nth sampling resistors by a current of each of the first to Nth LED blocks.

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