KR20110068321A - Display device, backlight unit and backlight unit control method - Google Patents

Abstract

According to the present invention, when the backlight unit receives a plurality of light source units and a plurality of image signals, and controls the plurality of light source units in a local control mode using values of the plurality of image signals, the local control mode may be abnormally performed. If so, the light source control device for terminating the local control mode. For this reason, the operation state of the local control mode of the backlight unit is monitored. If a malfunction occurs, the local control mode is canceled, thereby reducing the image quality reduction.

Description

DISPLAY DEVICE, BACKLIGHT UNIT AND MEHTOD FOR CONTROLLONG THE SAME}

The present invention relates to a display device, a backlight unit, and a backlight unit control method.

Display devices used in monitors and TVs of computers include light emitting diodes (LEDs), electroluminescence (EL), vacuum fluorescent displays (VFDs), and electroluminescent devices (fields). emission display (FED), plasma display panel (PDP), and the like, a liquid crystal display (LCD) that does not emit light by itself and requires a light source.

Therefore, a light source for a display device that requires a light source, that is, a backlight device, is a light source such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL), or a plurality of fluorescent lamps (LEDs) or light emitting diodes (LEDs). light emitting diode).

In the case of using a fluorescent lamp, the power consumption is large and the device characteristics of the liquid crystal display are deteriorated due to heat generation. In addition, since fluorescent lamps are generally rod-shaped, they are susceptible to shock and have a high risk of breakage. The temperature of the lamps is not constant according to the positions of the lamps, and thus the brightness of the lamps varies from position to position, thereby degrading the image quality of the display device.

On the other hand, since the light emitting diode is a semiconductor device, it has a long life, a fast lighting speed, and low power consumption. In addition, it is strong in impact and advantageous in miniaturization and thinning.

Therefore, a light emitting diode is used as a light source of a backlight device not only for a small display device such as a mobile phone but also for a medium-large display device such as a monitor or a television.

The problem to be solved by the present invention is to prevent the deterioration of the image quality of the display device.

According to an aspect of the present invention, a backlight unit is provided with a plurality of light source units and a plurality of image signals, and controls the plurality of light source units in a local control mode using values of the plurality of image signals. And a light source control device for canceling the local control mode when the local control mode is abnormally performed.

The light source control apparatus determines a local control determination position of a light source unit for local control among the plurality of light source units by using the value of the image signal, and outputs a plurality of control signals to the plurality of light source units to drive the plurality of light source units. It is preferable to determine the local control execution position of the light source unit to which the local control is currently performed by using the method, and to cancel the local control mode when the local control determination position and the local control execution position are different from each other.

When the local control determination position and the local control execution position are different from each other, the light source control device increases the number of error occurrences by "1", and maintains the local control mode when the number of error occurrences is less than the set number of times. When the number of error occurrences is equal to or greater than the set number of times, the local control mode may be canceled.

The backlight unit may further include a warning unit configured to operate according to a control signal output from the light source control device to externally indicate a termination state of the local control mode.

Each of the plurality of light source units may include at least one light emitting diode.

According to another aspect of the present invention, a display device receives a plurality of pixels arranged in a matrix form, a plurality of light source units supplying light to the pixels, and a plurality of image signals, and use values of the plurality of image signals. And controlling the plurality of light sources in the local control mode, the light source control device releasing the local control mode when the local control mode is abnormally performed.

The light source control apparatus determines a local control determination position which is a position of a light source unit for local control among the plurality of light source units by using the value of the image signal, and outputs to the plurality of light source units to drive the plurality of light source units. It is preferable to determine a local control execution position, which is a position of a light source unit to which local control is currently performed, by using a control signal, and cancel the local control mode when the local control determination position and the local control execution position are different from each other.

The plurality of pixels may be divided into a plurality of pixel blocks, and the plurality of light source units may be positioned to correspond to the plurality of pixel blocks.

The light source control apparatus determines whether a local control pixel block exists by using the video signal of the pixel corresponding to each pixel block unit, and when the local control pixel block exists, the local calculated among a plurality of light source units. Determine a local control light source unit corresponding to the control pixel block, determine a local control determination position using a light source control unit for locally controlling an operation of the local control light source unit, and a position with respect to the local control light source unit, A local control execution position where local control is currently being performed is determined using a plurality of control signals, and when the local control determination position and the local control execution position are different from each other, a control signal for canceling the local control mode is outputted to the light source. Local dimming drive control output to the controller Number, and the light source control unit to include may terminate the local control mode in response to a control signal from the local dimming driving control.

The local dimming driving control unit may output the control signal for canceling the local control mode to the light source control unit when the local control determination position and the local control execution position differ by more than a set number of times.

The display device may further include a warning unit configured to operate according to a control signal output from the local dimming driving controller to externally indicate a termination state of the local control mode.

According to another aspect of the present invention, a method of controlling a backlight unit may include determining a first position of a local control light source unit using location information of a local control light source unit determined based on a plurality of image signals, and driving the plurality of light source units. Determining a second position of the light source unit to which the control signal for the current local control is applied, using the plurality of control signals output for the purpose; comparing the first position with the second position, and the first position and If the second positions are different from each other, outputting a control signal for canceling the local control mode to the light source controller.

The outputting of the control signal may include calculating a current error occurrence number by increasing the value of the error occurrence count by “1” when the first position and the second position are different from each other. And comparing the control signal for canceling the local control mode to the light source controller when the current error occurrence number is equal to or greater than the set value, and the current error occurrence number is less than the set value. If so, the method may include maintaining the local control mode.

According to this feature, the operation state of the local control mode of the backlight unit is monitored. If a malfunction occurs, the local control mode is canceled, thereby reducing the image quality reduction.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Hereinafter, a liquid crystal display and a light source driving device, which are examples of a display device according to an exemplary embodiment, will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display according to an exemplary embodiment of the present invention. 3 is a detailed circuit diagram of a backlight unit according to an exemplary embodiment of the present invention. 4A and 4B are diagrams illustrating an example of an operation state of a local control pixel block and a local control light source unit corresponding thereto when the light source device according to an exemplary embodiment of the present invention is an edge type and a direct type.

As shown in FIG. 1, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a gray voltage generator. 800, the backlight unit 900, and the signal controller 600.

The liquid crystal panel assembly 300 may include a plurality of signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels PX connected to the plurality of signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. Include. On the other hand, in the structure shown in FIG. 2, the liquid crystal panel assembly 300 includes lower and upper panels 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

The signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a plurality of data lines for transmitting a data signal ( D ₁ -D _m ). The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

As shown in Fig. 2, each pixel PX, for example, the i-th (i = 1, 2, ..., n) gate line G _i and the j-th (j = 1, 2, ... m) The pixel PX connected to the data line D _j includes a switching element Q connected to the signal lines G _{i and} D _j , a liquid crystal capacitor Clc, and a storage capacitor connected thereto. (Cst). Holding capacitor Cst can be omitted as needed.

The switching element Q is a three-terminal element of a thin film transistor or the like provided in the lower panel 100, the control terminal of which is connected to the gate line G _i , and the input terminal of which is connected to the data line D _j . The output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst.

The liquid crystal capacitor Clc has two terminals, the pixel electrode 191 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 191 and 270 is a dielectric material. Function as. The pixel electrode 191 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives the common voltage Vcom. Unlike in FIG. 3, the common electrode 270 may be provided in the lower panel 100. In this case, at least one of the two electrodes 191 and 270 may be formed in a linear or bar shape.

The storage capacitor Cst, which serves as an auxiliary part of the liquid crystal capacitor Clc, is formed by overlapping a separate signal line (not shown) and the pixel electrode 191 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage Vcom is applied to the separate signal line. However, the storage capacitor Cst may be formed such that the pixel electrode 191 overlaps the front gate line directly above the insulator.

On the other hand, in order to implement color display, each pixel PX uniquely displays one of the primary colors (spatial division) or each pixel PX alternately displays the primary colors over time (time division). The desired color is recognized by the spatial and temporal sum of these primary colors. Examples of basic colors include red, green, and blue. FIG. 2 illustrates that each pixel PX includes a color filter 230 representing one of the primary colors in an area of the upper panel 200 corresponding to the pixel electrode 191 as an example of spatial division. Unlike in FIG. 2, the color filter 230 may be disposed above or below the pixel electrode 191 of the lower panel 100.

At least one polarizer (not shown) for polarizing light is attached to the liquid crystal panel assembly 300.

Referring back to FIG. 1, the gray voltage generator 800 generates two sets of gray voltages related to the transmittance of the pixel PX. One of the two sets has a positive value for the common voltage Vcom and the other set has a negative value. The number of gray voltages included in the set of gray voltages generated by the gray voltage generator 800 may be the same as the number of grays that the liquid crystal display can display.

The data driver 500 is connected to the data lines (D ₁ -D _m) of the liquid crystal panel assembly 300, select a gray voltage from the gray voltage generator 800 and the data lines do this as a data voltage (D ₁ -D _m ).

A gate driver 400, a gate line (G ₁ -G _n) and is connected to the gate turn-on voltage (Von), and a gate signal consisting of a combination of a gate-off voltage (Voff), a gate line (G ₁ of the liquid crystal panel assembly 300 -G _n ).

The signal controller 600 controls operations of the gate driver 400, the data driver 500, and the backlight unit 900.

As illustrated in FIG. 3, the backlight unit 900 may include a light source device 970 mounted at a lower portion or an edge of the liquid crystal panel assembly 300, a power supply unit 910 for supplying power to the light source device 970, A light source control device 920 connected to the light source device 970 and a warning unit 940 connected to the light source control device 920 are provided.

In an alternative embodiment, the backlight unit 900 further includes a plurality of optical instruments, such as an optical sheet, positioned between the liquid crystal panel assembly 300 and the light source device 970 and processing light from the light source device 970. can do.

As shown in FIG. 3, the light source device 970 includes a plurality of switching means connected to a plurality of light source units 971-97r (r = 2, 4, 5, ...) and a plurality of light source units 971-97r, respectively. SW1-SWr and a plurality of switching means SW1-SWr and a plurality of resistors R1-Rr connected between ground.

Each light source unit 971-97r includes a plurality of light sources (LEDs) including light emitting diodes (LEDs), and each light source unit 971-97r includes a series of light emitting diodes in which a plurality of light emitting diodes are connected in series. Form.

The plurality of light emitting diode rows 971-97r are white light emitting diode rows, but red, green, and blue light emitting diode rows may be alternately mounted. In this case, the number of green light emitting diodes may be greater than the number of red or blue light emitting diodes, for example, about twice as many, and the number of green light emitting diode rows may be twice as many as other light emitting diode rows, May vary as needed. In addition, in FIG. 3, each light source unit 971-97r includes five light emitting diodes (LEDs), but the present invention is not limited thereto. Can vary.

In alternative embodiments, each light source 971-97r may have at least one fluorescent lamp, such as CCFL or EEFL.

The light source device 970 of the backlight unit 900 is divided into two types according to the position of the light source units 971-97r mounted on the liquid crystal panel assembly 300.

That is, the light source device 970 includes an edge type light source device in which a plurality of light source portions 971-97r are installed at an edge of the liquid crystal panel assembly 300, and a plurality of light source portions below the liquid crystal panel assembly 300. 971-97r) are divided into direct type light source devices.

When the light source device 970 is an edge type, the light output from the light source parts 971-97r is moved to the center of the liquid crystal panel assembly 300 by a light guide plate (not shown) disposed under the liquid crystal panel assembly 300. In the case of the direct type, light is evenly distributed on the entire surface of the liquid crystal panel assembly 300 by the diffusion plate (not shown).

The plurality of switching elements SW1-SWr are formed of a transistor or the like, the control terminal of which is connected to the light source control device 920, the input terminal of which is connected to the light source units 971-97r, and the output terminal of the resistor ( R1-Rr).

The power supply unit 910 may include a rectifier and a DC-DC converter.

The light source controller 920 includes a light source controller 921 and a local dimming driving controller 922 connected to the light source controller 921.

The light source controller 921 is connected to the control terminals of the plurality of switching elements SW1-SWr to control the lighting operation of each light source unit 97-97r.

The local dimming driving controller 922 detects whether the local control operation is normally performed when the light source device 970 is controlled in the local control mode, and when the local control operation is abnormally performed, the local dimming driving control unit 922 Terminate.

In the present embodiment, the light source control unit 921 and the local dimming driving control unit 922 are located in the light source control unit 920, but, alternatively, the local dimming driving control unit 922 is located in the light source control unit 921 or the light source is located. The controller 921 and the local dimming driving controller 922 may be mounted as separate components.

The warning unit 940 operates according to a signal from the local dimming driving control unit 922. Warning unit 940 is composed of a warning light (alarm).

Each of the driving devices 400, 500, 800, and 600 may be integrated in the liquid crystal panel assembly 300 together with the signal lines G ₁ -G _n , D ₁ -D _m , and the switching element Q. Alternatively, these driving devices 400, 500, 800, 600 may be mounted directly on the liquid crystal panel assembly 300 in the form of at least one integrated circuit chip, or a flexible printed circuit film (not shown). It may be mounted on the liquid crystal panel assembly 300 in the form of a tape carrier package (TCP), or may be mounted on a separate printed circuit board (not shown). In addition, the driving devices 400, 500, 800, and 600 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside the single chip.

Next, the operation of the liquid crystal display will be described in detail.

The signal controller 600 receives input image signals R, G, and B and an input control signal for controlling the display thereof from an external graphic controller (not shown). The input image signals R, G, and B contain luminance information of each pixel PX, and the luminance is a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 ( = 2 ⁶ ) There are grays. Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 600 properly processes the input image signals R, G, and B based on the input image signals R, G, and B and the input control signal according to operating conditions of the liquid crystal panel assembly 300, thereby outputting the output image. After generating the signal DAT, generating the gate control signal CONT1, the data control signal CONT2, the backlight control signal CONT3, and the like, the gate control signal CONT1 is sent to the gate driver 400, and the data control is performed. The signal CONT2 and the processed image signal DAT are sent to the data driver 500, and the backlight control signal CONT3 is sent to the backlight unit 900.

The gate control signal CONT1 includes at least one clock signal for controlling the output period of the scan start signal STV indicating the start of scanning and the gate-on voltage Von. The gate control signal CONT1 may also further include an output enable signal OE that defines the duration of the gate-on voltage Von.

The data control signal CONT2 is a bundle, for example, the horizontal synchronization start signal STH indicating the start of transmission of the output image signal DAT for one row of pixels PX and the data to the liquid crystal panel assembly 300. A load signal LOAD and a data clock signal HCLK for applying a data voltage to the lines D ₁ -D _m are included.

The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the data voltage relative to the common voltage Vcom (hereinafter referred to as "data voltage polarity" by reducing "voltage polarity of the data voltage relative to the common voltage"). (RVS) may be further included.

The backlight control signal CONT3 is a light source control signal such as a brightness control signal (eg, a dimming signal) that controls the blinking of the light source device 970 based on the vertical synchronization signal Vsync, or the like, and the power supply unit 910. It includes a plurality of control signals, such as a signal for controlling the initial operation of. In this case, the brightness control signal is a pulse width modulation signal, but is not limited thereto.

Unlike the present embodiment, the backlight control signal CONT3 may be generated by a separate control device.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 receives a digital output image signal DAT for a group of pixels PX, and each digital output image signal DAT. By converting the digital output image signal DAT into an analog data voltage by selecting a gray scale voltage corresponding thereto, the digital output image signal DAT is applied to the corresponding data lines D ₁ -D _m . At this time, the signal controller 600 sequentially outputs the digital output image signal DAT corresponding to each of the group of pixels PX to the data driver 500 in synchronization with the data clock signal HCLK.

The gate driver 400 applies the gate-on voltage Von to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n . Turn on the switching element (Q) connected to. Then, the data voltage applied to the data lines D ₁ -D _m is applied to the pixel PX through the turned-on switching element Q.

The difference between the data voltage applied to the pixel PX and the common voltage Vcom is shown as the charging voltage of the liquid crystal capacitor Clc, that is, the pixel voltage. The liquid crystal molecules vary in arrangement depending on the magnitude of the pixel voltage.

The power supply unit 910 converts an AC voltage from the outside into a DC voltage, and then converts the converted DC voltage into a DC voltage having a desired size and supplies it to the light source device 970 as a driving voltage. In this case, the magnitude of the converted DC voltage may be adjusted according to the backlight control signal CONT3.

The voltage from the power supply unit 910 is applied to the light source device 970 and is controlled by the control signal of the light source controller 921 based on the light source control signal according to the backlight control signal CONT3. The operation state is controlled to cause the flashing operation of the light source parts 971-97r.

That is, the light source controller 921 of the light source controller 920 uses the brightness control signal contained in the input image signals R, G, and B and the light source control signal CONT3 applied from the signal controller 600. Determine whether the device 970 is controlled according to the global control mode or the local control mode.

The global control mode drives the light source units 971-97r with a control signal having a duty ratio determined according to the brightness control signal applied from the signal controller 600, and controls all the light source units 971-97r. The duty ratio of the signal is constant. Therefore, the brightness of the light source parts 971-97r is the same in principle.

On the other hand, in the local control mode, the light source units 971-97r corresponding to at least one pixel block (hereinafter, referred to as a "local control pixel block") of the plurality of pixel blocks already determined according to the image signals R, G, and B. (Hereinafter, referred to as "local control light source unit") and the remaining light source units 971-97r (hereinafter referred to as "dimming light source unit") control the driving state differently from each other.

For example, the duty ratio of the control signal applied to the switching elements SW1-SWr connected to the local control light source units 971-97r is applied to the switching elements SW1-SWr connected to the dimming light source units 971-97r. Control greater than the duty ratio of the control signal. For this reason, the brightness of the local control light source unit 971-97r which is operated by the control signal of the duty ratio larger than the duty ratio for the dimming light source units 971-97r, that is, is controlled by the dimming light source unit 971-97r. Brighter than 97r).

For such local control, the light source controller 921 reads the input image signals R, G, and B and analyzes the value of the image signal in units of pixel blocks having a predetermined size. Determine if it exists. For example, the light source controller 921 compares an average value of input image signals R, G, and B with a predetermined setting value for a plurality of pixels corresponding to each pixel block, and has a lower average value than the predetermined value. When the block exists, the light source controller 921 controls the operation of the light source device 970 according to the local control mode, and when there is no pixel block having an average value lower than the set value, the light source controller 921 controls the global control. The operation of the light source device 970 is controlled according to the mode.

At this time, the plurality of pixel blocks are determined based on the installation positions of the light source portions 971-97r. For example, when the light source device 970 is a direct type, at least one light source unit 971-97r may be positioned to correspond to the lower portion of each pixel block, and when the light source device 970 is an edge type, a row of each pixel block. The plurality of light source parts 971-97r may be positioned at the most edge of the liquid crystal panel assembly 300 corresponding to the position in the overheat direction.

In this embodiment, the pixel block having an average value larger than the set value is determined as the pixel block for local control, but is not limited thereto.

In the present embodiment, among the plurality of light source units 971-97r, the local control light source units 971-97r corresponding to the local control pixel blocks determined for local control are already determined in a memory such as a look-up table or the like. have.

Therefore, when the position of the pixel block for local control is determined, the light source controller 921 determines the position of the light source units 971-97r corresponding to the position of the pixel block for local control by using the information stored in the memory.

 Further, the duty ratio of the control signal for the local control light source units 971-97r is determined according to the average value of the local control pixel block corresponding to the local control light source units 971-97r, and for the dimming light source units 971-97r. The duty ratio of the control signal has a fixed value.

In this embodiment, the duty ratio of the control signal for the dimming light source portions 971-97 has a value between about 10% and 20%, but is not limited thereto.

4A and 4B show examples of operating states of the local control pixel block and the local control light source units 971-97r corresponding to each other in the local control mode. 4A is an example when the light source device 970 is an edge type, and FIG. 4B is an example when the light source device 970 is a direct type.

As shown in FIGS. 4A and 4B, the liquid crystal panel assembly 300 is divided into a total of 16 pixel blocks, and among the 16 pixel blocks, the number of local control pixel blocks DB is one, and the liquid crystal panel assembly ( A total of 16 light source units 971-986 are disposed at the edge and the bottom of the 300, respectively.

In addition, when locally controlling the operation of the light source unit 973, 980, 985 and 976 of FIG. 4B: 977 of FIG. 4B to correspond to the local control pixel block DM, the local corresponding to the local control pixel block DM may be used. The duty ratio of the control signal for the control light source unit (973, 980, 985 and 976 of FIG. 4A: 977 of FIG. 4B) is about 50%, while the duty ratio of the control signal applied to the dimming light source unit is about 10%. Therefore, it can be seen that the brightness of the pixel block DM to which local control is performed is much higher than the brightness of the remaining pixel blocks.

In the case of FIG. 4A, the duty ratios of the control signals for the plurality of light source units 973, 980, 985, and 976 positioned in the row and column directions corresponding to the local control pixel block DM are all the same. However, alternatively, in an alternative embodiment, the plurality of light source units according to the distance between the local control pixel block DM and the plurality of light source units 973, 980, 985 and 976 for damaging the local control pixel block DM are provided. The duty ratios of the control signals for the light source portions 973, 980, 985, and 976 may be different from each other or partly different. For example, the duty ratio of the corresponding control signal increases as the light source units 973, 980, 985, and 976 located closer to the local control pixel block DM, and conversely, located farther from the local control pixel block DM. The duty ratio of the control signal may decrease as the light source units 973, 980, 985, and 976.

In an alternative embodiment, the light source controller 921 may receive a current or voltage flowing through each resistor R1-Rr as a feedback signal, and control the operation of the light source supply unit 910 based on the received feedback signal. have. Therefore, the magnitude of the driving voltage applied to the light source device 970 is controlled according to the operating state of each light source unit 971-97r of the light source device 970, so that a current having a desired magnitude is constant in the light source unit 971-97r. Allow it to flow.

As described above, when the light source units 971-97r of the light source device 970 operate according to the control operation of the light source control unit 921, the light emitted from each light emitting diode (LED) passes through the liquid crystal layer 3. The polarization changes according to the arrangement. The change in polarization is represented by a change in the transmittance of light by a polarizer attached to the display panel assembly 300, whereby the pixel PX displays the luminance represented by the gray level of the image signal DAT.

This process is repeated in units of one horizontal period (also referred to as "1H" and equal to one period of the horizontal sync signal Hsync and the data enable signal DE), thereby all the gate lines G ₁ -G _n. In order to display the image of one frame by applying the gate-on voltage Von in order to apply the data voltage to all the pixels PX.

When one frame ends, the state of the inversion signal RVS applied to the data driver 500 is controlled so that the next frame starts and the polarity of the data voltage applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). In this case, the polarities of the data voltages flowing through one data line change according to the characteristics of the inversion signal RVS within one frame (eg, row inversion and point inversion), or polarities of data voltages applied to one pixel row are also different from each other. Can be different (eg invert columns, invert points).

When the light source device 970 is controlled in the local control mode by the light source control unit 921, the local dimming drive control unit 922 monitors the local control operation currently being performed and determines whether the local control operation is normally performed.

When the local control operation is abnormally performed, the local dimming driving control unit 922 releases the local control mode and controls the operation of the light source device 970 in the global control mode.

However, when the user selects a state in which the user does not use the local control mode through an externally mounted selection switch or the like, for example, the "local control mode off" state, the light source controller 921 controls a separate control for local control. The operation of the light source portions 971-97r of the light source device 970 is controlled in the global control mode without executing the operation.

Next, the operation of the local dimming driving controller 922 will be described in more detail with reference to FIG. 5.

5 is a flowchart illustrating operations of a local dimming driving controller according to an embodiment of the present invention.

First, when the operation is started (S10), the local dimming driving control unit 922 requests the light source control unit 921 for location information of the local control light source unit for local control, and is transmitted from the light source control unit 921 in response thereto. The location information of the local control light source unit (hereinafter referred to as "local control determination position") calculated based on the input image signals R, G, and B is determined by receiving the position information of the local control light source unit (S12).

Next, the local dimming drive control unit 922 reads the control signal output to the corresponding switching means SW1-SWr to drive the respective light source units 971-97r, and outputs the control signal to the respective switching means SW1-SWr. The duty ratio is determined (S14), whereby the position (hereinafter, referred to as "local control execution position") of the light source units 971-97r to which the control signal for the current local control is applied is determined (S16).

In the present embodiment, the duty ratio has a value already set for the control signal applied to the corresponding switching elements SW1-SWr for the dimming light source parts 271-27r. Accordingly, the local dimming drive control unit 922 determines the light source units 971-97r corresponding to the control signal whose duty ratio is greater than the set value as the local control light source unit for which local control is currently performed, and executes the local control. Determine by location.

Next, the local dimming drive control unit 922 determines whether the local control determination position and the local control execution position are the same (S18).

If the local control determination position and the local control execution position are the same as each other, the local dimming drive control unit 922 determines that the operation of the local control mode is normally performed, and falls to step S12 to continue operation of the local control mode. To monitor.

However, when the local control determination position and the local control execution position are different from each other, the local dimming drive control unit 922 is at the position of the light source units 971-97r currently being subjected to local control to be wrong, so that unwanted pixels are not the pixel blocks for local control. The brightness of the light source units 971-97r corresponding to the block, i.e., the dimming pixel block, is locally controlled to determine that the local control pixel block is brighter than the dimming pixel block.

Therefore, the local dimming driving control unit 922 increases the number of error occurrences by "1", and calculates the current number of errors occurring during local control (S20).

Then, the calculated number of errors is compared with the set number of times (S22).

Therefore, when the calculated number of errors is smaller than the set number of times, the local dimming drive control unit 922 determines that a malfunction occurs temporarily and proceeds to step S12 to monitor the operation of the local control mode.

However, when the calculated number of errors is smaller than the set number of times, the local dimming drive control unit 922 determines that the local control mode operation is abnormally performed.

Therefore, the local dimming driving controller 922 outputs a control signal for releasing the local control mode to the light source controller 921 (S24).

Accordingly, the light source controller 921 switches the operation mode of the light source device 970 to the global control mode regardless of the average image signal values of the plurality of pixel blocks, thereby turning on the light source units 971-97r of the light source device 970. Control the operation.

Then, the local dimming driving control unit 922 outputs a warning signal to the warning unit 940 (S26), and operates the warning unit 940 to indicate to the user that an error has occurred in the local control operation. Accordingly, the user may perform necessary actions such as a service request according to the operation state of the warning unit 940.

As such, when the light source device 970 is controlled in the local control mode, the operating state of the local control mode is monitored, and if the local control operation is abnormally terminated, the local control mode is terminated. Therefore, a malfunction caused by abnormally controlled brightness of the pixel block is prevented in the local control mode, thereby reducing the problem of deterioration of the image quality of the output image.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

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

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a detailed circuit diagram of a backlight unit according to an exemplary embodiment of the present invention.

4A illustrates an example of an operation state of a local control pixel block and a local control light source unit corresponding thereto when the light source device is an edge type according to an exemplary embodiment of the present disclosure.

4B is a diagram illustrating an example of an operation state of a local control pixel block and a local control light source unit corresponding thereto when the light source device is a direct type according to an exemplary embodiment of the present invention.

5 is a flowchart illustrating operations of a local dimming driving controller according to an embodiment of the present invention.

* Brief description of the main parts of the drawing *

3: liquid crystal layer 100, 200: display part

230: color filter 270: common electrode

300: liquid crystal panel assembly 400: gate driver

500: data driver 600: signal controller

800: gray voltage generator 900: backlight unit

910: power supply unit 920: light source control device

921: light source controller 922: local dimming driving controller

940: warning section 971-97r: light source section

SW1-SWr: switching means R1-Rr: resistance

Claims (13)

A plurality of light sources, and When a plurality of video signals are received and the plurality of light source units are controlled in a local control mode using values of the plurality of video signals, when the local control mode is abnormally performed, the light source control to cancel the local control mode. Device A backlight unit comprising a. In claim 1, The light source control apparatus determines a local control determination position of a light source unit for local control among the plurality of light source units by using the value of the image signal, and outputs a plurality of control signals to the plurality of light source units to drive the plurality of light source units. And a local control execution position of a light source unit to which local control is currently performed, and cancels the local control mode when the local control determination position and the local control execution position are different from each other. 3. The method of claim 2, When the local control determination position and the local control execution position are different from each other, the light source control device increases the number of error occurrences by "1", and maintains the local control mode when the number of error occurrences is less than the set number of times. And canceling a local control mode when the number of error occurrences is equal to or greater than a set number of times. The method according to any one of claims 1 to 3, And a warning unit configured to operate according to a control signal output from the light source control device to externally indicate a termination state of the local control mode. The method according to any one of claims 1 to 3, Each of the plurality of light source units includes at least one light emitting diode. A plurality of pixels arranged in a matrix form, A plurality of light source units supplying light to the pixels, and When a plurality of video signals are applied and the plurality of light source units are controlled in a local control mode using values of the plurality of video signals, when the local control mode is abnormally performed, the light source control to release the local control mode. Device Display device comprising a. In claim 6, The light source control apparatus determines a local control determination position which is a position of a light source unit for local control among the plurality of light source units by using the value of the image signal, and outputs to the plurality of light source units to drive the plurality of light source units. And a local control execution position that is a position of a light source unit to which current local control is currently performed using a control signal, and cancels the local control mode when the local control determination position and the local control execution position are different from each other. 8. The method of claim 7, The plurality of pixels are divided into a plurality of pixel blocks, and the plurality of light source units are positioned to correspond to the plurality of pixel blocks. In claim 8, The light source control device, It is determined whether a local control pixel block exists by using the video signal of the pixel corresponding to each pixel block unit, and when the local control pixel block exists, it corresponds to the local control pixel block calculated from a plurality of light source units. A light source controller for determining a local control light source unit and locally controlling an operation of the local control light source unit; and A local control determination position is determined using a position with respect to the local control light source unit, a local control execution position at which local control is currently being performed is determined using a plurality of control signals for the plurality of light source units, and the local control determination position and the Local dimming drive control unit outputting a control signal for canceling the local control mode to the light source control unit when the local control execution positions are different from each other. Including, The light source controller cancels the local control mode according to a control signal from the local dimming driving controller.  Display device. The method of claim 9, And the local dimming driving control unit outputs the control signal for canceling the local control mode to the light source control unit when the local control determination position and the local control execution position differ by more than a set number of times. The method of claim 9, And a warning unit configured to operate according to a control signal output from the local dimming driving controller to externally indicate a termination state of the local control mode. Determining a first position of the local control light source unit by using the position information of the local control light source unit determined based on the plurality of video signals; Determining a second position of a light source unit to which a control signal for current local control is applied using a plurality of control signals output to drive the plurality of light source units, Comparing the first location with the second location, and Outputting a control signal for canceling a local control mode to a light source controller when the first position and the second position are different from each other; Containing How to control the backlight module unit. The method of claim 12, The control signal output step, If the first position and the second position are different from each other, increasing the value of the error occurrence count by “1” to calculate a current error occurrence count; Comparing the current error occurrence number with a set value, and The control signal for canceling the local control mode is output to the light source controller when the current error occurrence number is equal to or greater than the set value, and the local control mode is output when the current error occurrence number is less than the set value. Steps to maintain Backlight unit control method comprising a.

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