KR102185676B1 - Apparatus for controlling dimming of backlight - Google Patents

Abstract

The present invention relates to an apparatus for controlling dimming of a backlight, including: a backlight in which a plurality of LEDs are connected to form a channel, and the channel is formed in multiple; a switching device for local dimming and connected, during local dimming control, to one end of each of the channels to apply an LED driving voltage to one end of each of the plurality of LEDs; a global dimming switching element, during global dimming control, connected to the other end of each of the plurality of channels for applying an LED driving voltage to one end of each of the plurality of LEDs; an IC chip for generating a PWM signal for applying a PWM signal to the other end of the plurality of LEDs through a PWM signal line for each channel connected to each of the plurality of channels; a grounding unit composed of a grounding switching element connected to a PWM signal line for applying a PWM signal to a plurality of LEDs through each of the plurality of channels during the global dimming control; a controller, during the local dimming control, to sequentially apply a switching signal to the switching element for local dimming to apply the LED driving voltage to each channel, and to turn off the local dimming switching device and turning on the grounding switching device during the global dimming control; and a global dimming controller, during the global dimming control, to turn on the global dimming switching element at the same time to apply an LED driving voltage to the plurality of LEDs connected to each of the plurality of channels, and turns off the global dimming switching element during the local dimming control.

Description

Backlight dimming control device {APPARATUS FOR CONTROLLING DIMMING OF BACKLIGHT}

The present invention relates to a backlight dimming control apparatus capable of handling global dimming as well as local dimming.

A liquid crystal display device has been widely used until recently as a flat panel display device. A liquid crystal display device is a non-luminescent display that cannot emit light by itself and needs a light source that supplies light from the outside. Such a device that supplies light from the rear of the liquid crystal display is called a backlight unit (BLU).

The liquid crystal display device displays an image by modulating light incident from a backlight unit by controlling an electric field applied to a liquid crystal layer. The image quality of a liquid crystal display device is largely influenced by a contrast ratio. However, there is a limit to improving the contrast ratio only by modulating the light transmittance of the liquid crystal layer by controlling the data voltage applied to the liquid crystal layer.

In order to improve the contrast ratio of a liquid crystal display device, a backlight dimming method for adjusting the brightness of a backlight unit according to an image has been proposed. The backlight dimming method includes a global dimming method that adjusts the luminance of the display surface as a whole, and a local dimming method that partially adjusts the luminance of the display surface. The global dimming method can improve a dynamic contrast ratio. The local dimming method can improve a static contrast ratio, which is difficult to improve by the global dimming method, by partially controlling the luminance of the display surface within one frame period.

In such a liquid crystal display device, a backlight unit is divided into a direct type type and a side type type of an edge type backlight unit according to an arrangement of a light source. In the edge type, a light source in the form of a bar is positioned on the side of the liquid crystal panel and irradiates light toward the liquid crystal panel through the light guide plate, whereas in the direct type, the liquid crystal panel is directly illuminated from a surface light source located under the liquid crystal panel.

Recently, in order to more vividly represent an image, the liquid crystal panel of the liquid crystal display device is divided into a plurality of areas, and the light source luminance value of the backlight unit can be adjusted for each divided area according to the gray level value of each divided area. . This backlight unit driving method is called local dimming. That is, the LEDs in the backlight unit area corresponding to the brightly displayed part on the screen may be partially turned on, and the LEDs corresponding to the remaining screen parts may be turned on with low luminance or completely turned off. According to the local dimming driving method, a brighter portion becomes brighter and a dark portion becomes darker, thereby realizing a more realistic image.

Meanwhile, in a liquid crystal display device using a backlight unit using a local dimming method, there is a case where it is necessary to convert from local dimming to global dimming. For example, in the driving frequency conversion section, the luminance of the backlight unit cannot be adjusted by the local dimming method, so the luminance of the backlight unit is adjusted by the global dimming method. At this time, there is a problem in that an inrush phenomenon occurs in which a current flowing through the backlight unit rapidly increases at the moment when the driving frequency conversion section starts, that is, the moment the dimming method is converted from the local dimming method to the global dimming method. In addition, when the driving frequency conversion period ends, that is, when the dimming method is changed from the global dimming method to the local dimming method, a backlight flashing phenomenon occurs in which the image displayed by the display panel is visually recognized.

Republic of Korea Patent Publication No. 10-2018-0062573 (published on June 11, 2018)

The present invention provides a backlight dimming control device capable of handling when global dimming is required in a backlight unit controlled by a local dimming method.

In addition, the present invention further adds a switching element, a controller, and a controller for global dimming separately from a controller and a switching element for local dimming, thereby preventing a backlight flashing phenomenon when converting from local dimming to global dimming. Provides a backlight dimming control device.

In order to solve the above-described problem to be solved, the backlight dimming control apparatus according to an embodiment of the present invention comprises a plurality of LEDs connected to form a channel, the plurality of channels is a backlight having a plurality of channels, and the plurality of channels when controlling local dimming. A switching element for local dimming that is connected to each end to apply an LED driving voltage to one end of each of the plurality of LEDs, and an LED at one end of each of the plurality of LEDs connected to the other end of each of the plurality of channels during global dimming control. An IC chip for generating a PWM signal for applying a PWM signal to the other ends of the plurality of LEDs through a switching element for global dimming that applies a driving voltage and a PWM signal line for each channel connected to each of the plurality of channels, and the global dimming A grounding unit consisting of a grounding switching element connected to a PWM signal line that applies a PWM signal to a plurality of LEDs through each of the plurality of channels during control, and a switching signal sequentially to the local dimming switching element during the local dimming control A controller that applies LED driving voltage to each channel by applying and turns on the LED driving voltage to each channel, turns off the local dimming switching element and turns on the ground switching element during the global dimming control, and the global dimming when the global dimming control It may include a global dimming controller that simultaneously turns on the switching element for applying an LED driving voltage to a plurality of LEDs connected to each of the plurality of channels, and turns off the global dimming switching element during the local dimming control.

According to an embodiment of the present invention, the backlight dimming control device may perform local dimming or global dimming by a timing controller of a liquid crystal display.

According to an embodiment of the present invention, the global dimming may be performed by the timing controller to control the brightness of the liquid crystal display device.

According to an embodiment of the present invention, the backlight may include a plurality of channels to which the plurality of LEDs are connected in parallel.

According to the above-described embodiments of the present invention, the present invention further adds a switching element, a controller, and a controller for global dimming separately from a controller and a switching element for local dimming, so that the backlight is converted from local dimming to global dimming. Flashing (Backlight Flashing) can be prevented.

1 is a schematic diagram of a liquid crystal display according to an exemplary embodiment of the present invention.
2 is a view showing a control device for controlling a backlight according to an embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms different from each other, and only these embodiments make the disclosure of the present invention complete, and common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have it, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and the present invention is not limited to the illustrated matters. The same reference numerals refer to the same components throughout the specification.

In addition, in describing the present invention, when it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

When'include','have','consists of' and the like mentioned in the present specification are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

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

In the case of a description of the positional relationship, for example, if the positional relationship of two parts is described as'upper','upper of','lower of','next to','right' Or, unless'direct' is used, one or more other parts may be located between the two parts.

In the case of a description of a temporal relationship, for example, when a temporal predecessor relationship is described as'after','following','after','before', etc.,'right' or'direct' It may also include cases that are not continuous unless this is used.

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

"X-axis direction", "Y-axis direction", and "Z-axis direction" should not be interpreted only as a geometrical relationship in which the relationship between each other is vertical, and is wider than within the range in which the configuration of the present invention can function functionally It can mean having directionality.

The term “at least one” is to be understood as including 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 2 among the first item, the second item, and the third item as well as each of the first item, the second item, or the third item. It may mean a combination of all items that can be presented from more than one.

Each of the features of the various embodiments of the present invention can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments can be implemented independently of each other or can be implemented together in a related relationship. May be.

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

1 is a diagram schematically illustrating a liquid crystal display device according to an exemplary embodiment of the present invention, and FIG. 2 is a view illustrating a control device for controlling a backlight according to an exemplary embodiment of the present invention.

The liquid crystal display device 100 according to the present invention is a timing for controlling the driving timing of the liquid crystal panel 110, the data driver 120, the gate driver 130, the data driver 120, and the gate driver 130, respectively. The control unit 140 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 areas SP defined by crossing a plurality of gate lines GL and a plurality of data lines DL, and a plurality of subpixel areas SP A thin film transistor T connected to the gate line GL and the data line DL, a storage capacitor Cst connected to the thin film transistor T, and a liquid crystal cell Clc are formed in the gate line GL and the data line DL.

Here, the plurality of sub-pixel regions SP may be, for example, red, green, and blue sub-pixel regions SP, and may be sequentially arranged in a horizontal direction (horizontal direction) or a vertical direction (vertical direction). have.

Further, in the liquid crystal panel 110, pixel regions including red, green, and blue subpixel regions SP may be arranged in a matrix shape of MxN (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, it is turned on and transmits data to the liquid crystal cell Clc through the data line DL. A signal is supplied, and when the gate low voltage VGL is supplied through the gate line GL, it is turned off.

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

In the liquid crystal cell Clc, a gradation is realized by adjusting the light transmittance by varying the arrangement state of the liquid crystals according to the data signal charged through the thin film transistor T.

In addition, the storage capacitor Cst serves to maintain 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) that supplies a data signal to the liquid crystal panel 110.

The data driver 120 is a driver such as a converted image signal (R/G/B) received from the timing controller 140, a source start pulse (SSP), a source shift clock (SSC), and a source output enable (SOE). 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 control unit 140 includes a plurality of video signals and vertical synchronization signals (Vsync), horizontal synchronization signals (Hsync), and data enable signals (DE) from a system such as a graphics card through a low voltage differential signal (LVDS) interface. ), etc., can be received.

In addition, the timing controller 140 generates a gate control signal GCS for controlling the gate driver 130 and a data control signal DCS for controlling the data driver 120 by using a plurality of control signals. I can.

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

At this time, the LVDS (Low Voltage Differential Signal) interface is an LVDS transmitter (not shown) that converts and transmits a plurality of video signals and control signals received from the system into LVDS signals, and an LVDS signal from the LVDS transmitter. It may include an LVDS receiver (not shown) that receives a plurality of converted N-bit video signals and a plurality of control signals.

Here, the LVDS transmitter may be built into the system, and the LVDS receiver may be built into the timing controller 140.

Meanwhile, the timing controller 140 may generate a backlight control signal BCS for controlling the backlight driver 150 or a local PWM dimming signal and a global 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 and analyzes the input image in units of blocks of images corresponding to the LED block size of the backlight unit, and the analysis result The local dimming value can be generated according to.

The gate driver 130 may be formed by a GIP (Gate In Panel) method, etc., and generates a gate signal using a plurality of gate control signals received from the timing controller 140, and converts the generated gate signal to a plurality of gates. It may be controlled to be supplied to the liquid crystal panel 110 through the wiring GL.

Although not shown, a gamma voltage generation circuit (not shown) and a power supply circuit (not shown) may be further included, and the gamma voltage generation circuit divides a high potential voltage and a low potential voltage to generate a plurality of gamma voltages, This can be supplied to the data driver 140.

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

The backlight driver 150 generates a driving voltage and a driving current and supplies it to the backlight 160, and 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 It may include.

Further, the backlight driver 150 generates a PWM signal having a duty ratio between 0-100% according to a plurality of local 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 variously change the delay times of the plurality of PWM signals for controlling the plurality of LED blocks according to the duty ratio of each PWM signal. To this end, the backlight driver 150 may include a controller 200 and an IC chip 210 for generating a PWM signal, as shown in FIG. 2.

The PWM signal generation IC chip 210 generates a PWM signal having a duty ratio between 0 and 100% using a plurality of PWM dimming signals, and determines the delay time of a plurality of PWM signals according to the duty ratio of each PWM signal. It can be changed in various ways.

In addition, the backlight driver 150 according to an embodiment of the present invention includes a global dimming controller 220 and a global dimming switching element 221/1, 221/2 in order to perform global dimming according to the control of the timing controller 140. , …, 221/n) and a plurality of grounding switching elements 230/1, 230/2, …, 230/n, etc. connected to each of the PWM signal lines may be provided.

The global dimming controller 220 operates in accordance with the control signal of the timing controller 140 to simultaneously turn on the global dimming switching elements 221/1, 221/2, ..., 221/n to increase the LED driving voltage (VLED). It can be applied to multiple LEDs 161 of each channel.

A plurality of grounding switching elements 230/1, 230/2, ..., 230/n of the grounding part 230 are turned on according to a switching signal generated from the controller 200 under the control of the timing controller 140 The PWM signal line of each channel can be grounded.

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

The backlight 160, as shown in FIG. A plurality of LEDs 161 may be bundled and configured as an LED block. For example, a plurality of LEDs 161 may be connected in parallel to form one channel, and a plurality of channels may be configured in a matrix form. Such an LED block may be driven for each channel by a 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 161 constituting the LED block, and the emission time of the plurality of LEDs 161 and the light emission time of the plurality of LEDs 161 according to the duty ratio of the PWM signal The amount of current flowing to the plurality of LEDs 161 can be adjusted. For example, the light emission time of the plurality of LEDs 161 driven by the PWM signal having a large duty ratio may be long, and the light emission time of the plurality of LEDs 161 driven by the PWM signal having a large duty ratio may be short.

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

As such a local PWM dimming signal is input from the timing controller 140, the backlight driver 150 controls the controller 200 and the PWM signal generator IC chip 210 as shown in FIG. 2 to the backlight 160 It is possible to perform local dimming by controlling a plurality of LEDs 161 constituting a. Specifically, the backlight driver 150 controls the controller 200 to sequentially generate a switching signal, and a plurality of local dimming switching elements 201/1, 201/2, ..., 201/n connected to the controller 200 ) Is sequentially turned on to supply voltage (VLED) to a plurality of LEDs 161 constituting the backlight 160, and has a duty ratio determined by a local PWM dimming signal through the IC chip 210 for a PWM signal generator. By applying a PWM signal to a plurality of LEDs 161, local dimming can be performed.

In the embodiment of the present invention, the switching elements 201/1, 201/2, …, 201/n for local dimming are inputted with a switching signal generated by the controller 200 as one end, and are turned on and applied according to the switching signal. It may be a PNP type transistor device capable of applying a voltage VLED to a plurality of LEDs 161 connected in parallel.

On the other hand, as the global PWM dimming signal is input from the timing controller 140, the backlight driver 150 is transferred to the local dimming switching elements 201/1, 201/2, ..., 201/n through the controller 200. In addition to turning off the applied switching signal, by simultaneously applying a switching signal to the global dimming switching elements 221/1, 221/2, ..., 221/n through the global dimming controller 220, the global dimming switching element ( 221/1, 221/2, …, 221/n) can be turned on. Accordingly, a voltage (VLED) applied through the global dimming switching elements 221/1, 221/2, ..., 221/n is applied to the plurality of LEDs 161 to operate the backlight 160. .

In addition, the backlight driver 150 applies a switching signal to the grounding switching elements 230/1, 230/2, ..., 230/n constituting the grounding part 230 to be turned on, so that the grounding switching element 230 /1, 230/2, …, 230/n) connected to the PWM signal line can be grounded.

Through this operation, the backlight driver 150 can simultaneously turn on all of the LEDs 161 constituting the backlight 160, thereby performing a global dimming operation.

The control process of the backlight 160 having the above-described configuration will be described below.

First, the timing controller 140 may generate a signal for local PWM dimming for local dimming and apply it to the IC chip 210 for generating a PWM signal.

Accordingly, the PWM signal generation IC chip 210 may generate a PWM signal having a predetermined duty based on the local PWM dimming signal and apply it to the other ends of the plurality of LEDs 161. In addition, as the switching signal generated by the controller 200 is sequentially applied to the plurality of local dimming switching elements 201/1, 201/2, ..., 201/n, the local dimming switching element 201/ 1, 201/2, ..., 201/n) are sequentially turned on so that the LED driving voltage VLED may be applied to one end of the plurality of LEDs 161.

Accordingly, the light emission time of the plurality of LEDs 161 and the amount of current flowing to the plurality of LEDs 161 are adjusted according to the duty ratio of the PWM signals applied to the plurality of LEDs 161 constituting the backlight 160. The brightness and light emission time for each of the plurality of LEDs 161 of 160) may be controlled.

In the embodiment of the present invention, a plurality of LEDs 161 are connected in parallel to the line to which the PWM signal is applied to receive the PWM signal to the other end, and one end of the switching elements for local dimming (201/1, 201/2, …, 201/n) through which the LED driving voltage (VLED) is applied to operate. In this case, the LED brightness and light emission time may be determined by the duty ratio of the PWM signal.

Meanwhile, the timing controller 140 includes a signal for turning off the local dimming switching elements 201/1, 201/2, …, 201/n connected to the controller 200 for global dimming and the global dimming controller 220 In addition to generating a control signal for operating, it is possible to generate a global PWM dimming signal and apply it to the PWM signal generation IC chip 210. Accordingly, the controller 200 turns off the local dimming switching elements 201/1, 201/2, ..., 201/n, and the global dimming controller 220 is turned on and connected to the global dimming controller 220. The LED driving voltage applied to the global dimming switching elements (221/1, 221/2, ..., 221/n) by turning on all the dimming switching elements (221/1, 221/2, ..., 221/n) VLED) can be applied to a plurality of LEDs (161).

On the other hand, the controller 200 generates a switching signal for turning on the ground switching elements 230/1, 230/2, ..., 230/n, and the ground switching elements 230/1, 230/2, ..., 230/n) connected to the PWM signal line can be grounded.

Accordingly, the PWM signal generation IC chip 210 may generate a PWM signal having a predetermined duty ratio based on the global PWM dimming signal and apply it to the other ends of the plurality of LEDs 161.

Accordingly, a plurality of LEDs 161 constituting the backlight 160 may simultaneously emit light according to the duty ratio of the PWM signal.

According to the embodiment of the present invention as described above, although it has been described as an example that the PWM signal generating IC chip 210 for generating the PWM signal is composed of one chip, it may be composed of two or more IC chips.

The foregoing description of the present application is for illustrative purposes only, and those of ordinary skill in the art to which the present application pertains will be able to understand that it is possible to easily transform it into other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present application. .

100: liquid crystal display device
110: liquid crystal panel
120: data driver
130: gate driver
140: timing control unit
150: backlight driver
160: backlight
200: controller
210: IC chip for PWM signal generation
220: global dimming controller
230: ground part

Claims (4)

In the backlight dimming control device,
A plurality of LEDs are connected to form a channel, and a backlight comprising a plurality of the channels,
A local dimming switching element connected to one end of each of the plurality of channels to apply an LED driving voltage to each end of the plurality of LEDs during local dimming control;
A global dimming switching element connected to the other end of each of the plurality of channels and applying an LED driving voltage to one end of each of the plurality of LEDs during global dimming control;
An IC chip for generating a PWM signal for applying a PWM signal to the other ends of the plurality of LEDs through a PWM signal line for each channel connected to each of the plurality of channels,
A grounding unit comprising a grounding switching element connected to a PWM signal line for applying a PWM signal to a plurality of LEDs through each of the plurality of channels during the global dimming control,
During the local dimming control, a switching signal is sequentially applied to the local dimming switching element to be turned on to apply an LED driving voltage to each channel, and the local dimming switching element is turned off during the global dimming control. A controller that turns on the switching element,
A global dimming controller for applying an LED driving voltage to a plurality of LEDs connected to each of the plurality of channels by simultaneously turning on the global dimming switching element during the global dimming control, and turning off the global dimming switching element during the local dimming control Including
Backlight dimming control device.
The method of claim 1,
The backlight dimming control device,
Local dimming or global dimming by the timing controller of the liquid crystal display
Backlight dimming control device.
The method of claim 2,
The global dimming,
Made by the timing control unit to control the brightness of the liquid crystal display device
Backlight dimming control device.
The method of claim 1,
The backlight,
Consisting of a plurality of channels in which the plurality of LEDs are connected in parallel
Backlight dimming control device.

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