KR20110033471A - Display device, apparatus for driving light source and method thereof - Google Patents

Abstract

PURPOSE: A display device, an apparatus for driving light source, and a method thereof are provided to reduce malfunctions due to open and short state of a light emitting diode by including a light source controller. CONSTITUTION: In a display device, an apparatus for driving light source, and a method thereof, a light source controller(930) decodes the operation state of the light source(S12). The light source controller determines whether one of the plural light sources is an abnormal state or not(S13). The light source controller outputs the abnormal operation signal to a determination unit(S14). The determination unit request the operation state signal of the light source from the light source controller(S15). The determination unit determines the kind of an abnormal state and a generation position(S18). The determination unit outputs abnormal information to the light source controller, which outputs a control signal.

Description

Display device, light source driving device and method thereof {DISPLAY DEVICE, APPARATUS FOR DRIVING LIGHT SOURCE AND METHOD THEREOF}

The present invention relates to a display device, a light source driving device and a method thereof.

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.

A general liquid crystal display device includes two display panels provided with a field generating electrode and a liquid crystal layer having dielectric anisotropy interposed therebetween. A voltage is applied to the field generating electrode to generate an electric field in the liquid crystal layer, and the voltage is changed to adjust the intensity of the electric field, thereby adjusting the transmittance of light passing through the liquid crystal layer to obtain a desired image.

In this case, the light may be a separate artificial light source or natural light.

A light source for a liquid crystal display, that is, a backlight unit, is a light source and includes a plurality of fluorescent lamps or light emitting diodes such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL). ).

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 typically 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.

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 unit not only for a small liquid crystal display such as a mobile phone but also for a medium and large liquid crystal display such as a monitor or a television.

The problem to be solved by the present invention is to reduce the occurrence of defects due to malfunction of the light source.

A light source driving apparatus according to an aspect of the present invention for achieving the above object is a driving device for driving a light source unit operated by a driving voltage, the light source operation corresponding to the operating state of the light source unit using the output voltage output from the light source unit And a light source control unit configured to output a state signal, and a light source control device to control an operation of the light source unit or to control the driving voltage when the light source unit is in an abnormal state by receiving the light source operating state signal.

The light source control device may include: a light source controller configured to detect an abnormal state of the plurality of light source units based on the light source operating state signal and output an abnormal operation signal; and when an abnormal operation signal is input from the light source controller, the light source operating state signal. And a light source state determination unit configured to determine the type and occurrence position of the abnormal state and to output abnormal state information corresponding to the type and occurrence position of the abnormal state to the light source control unit. Determines a kind of an abnormal state of the light source unit and a position of the light source unit in which the abnormal state occurs based on the abnormal state information, and determines an operation of the light source unit corresponding to the abnormal state occurrence position or a light source unit corresponding to the abnormal normal state occurrence position. Stop the drive voltage control based on can do.

The abnormal state is preferably one of an open state and a short state.

The light source driving apparatus according to the above feature may further include a feedback controller configured to control the driving voltage by sensing a voltage based on a current flowing through the plurality of light source units, wherein the light source controller is in an open state of the light source unit. In this case, the light source unit corresponding to the abnormal state occurrence position may be turned off, and when the abnormal state of the light source unit is a short circuit state, the voltage corresponding to the light source unit at the abnormal state occurrence position may be blocked from being applied to the feedback controller.

The light source driving apparatus according to the above feature may further include a switching unit having a plurality of switching means connected between the plurality of light source units and the ground, and a plurality of switches respectively connected between the plurality of light source units and the feedback. The light source control unit turns off the switching means corresponding to the abnormal state occurrence position among the plurality of switching means when the abnormal state of the light source unit is in an open state, and when the abnormal state of the light source unit is a short state, The electrical connection between the light source unit and the feedback control unit may be blocked by controlling a switch corresponding to the abnormal state occurrence position among switches.

The light source state detector may output the light source operating state signal using the output voltage and at least one reference voltage.

The at least one reference voltage includes a first reference voltage and a second reference voltage different from the first reference voltage, and the light source state detecting unit uses the plurality of output voltages and the first reference voltages. The open state of the light source may be sensed, and a short state of the light source units may be detected using the plurality of output voltages and the second reference voltage.

Preferably, the first reference voltage is smaller than the second reference voltage.

The light source state detector may include a plurality of first comparators comparing the plurality of output voltages and the first reference voltage and a plurality of second comparators comparing the plurality of output voltages and the second voltage.

The light source controller may include a memory unit that stores the light source operating state signal.

The light source unit preferably includes at least one light emitting diode.

According to another aspect of the present invention, there is provided a method of driving a light source control apparatus, which controls an abnormal state of the light source by using light source operating state signals corresponding to operating states of a plurality of light sources, and includes a light source control unit and a light source state determination unit. A method of driving an apparatus, the light source control unit comprising: reading the light source operating state signal, determining whether an abnormal state has occurred in at least one of the plurality of light sources based on the light source operating state signal, and the plurality of Outputting an abnormal operation signal to the light source state determination unit, when the abnormal state occurs in at least one of the light sources, wherein the light source state determination unit receives the light source operation state signal when the abnormal operation signal is received. Requesting a control unit from the light source control unit to the light source operating state; Determining a type and occurrence position of an abnormal state based on the light source operating state signal, and outputting abnormal occurrence information to the light source controller based on the type and occurrence position of the abnormal state when the signal is input; The light source control unit may further include determining a type and a location of the abnormal state and outputting a control signal based on the abnormal occurrence information.

The abnormal state is preferably one of an open state and a short state.

The control signal outputting step may include outputting a control signal for blocking feedback control based on the light source corresponding to the generation position when the type of the abnormal state is the open state, and the type of the abnormal state is the short circuit. In a state, it is preferable to include the step of outputting a control signal to turn off the light source corresponding to the generation position.

Comparing the elapsed time for the abnormal state of the determined type with a set time, outputting the abnormal occurrence information to the light source controller when the elapsed time exceeds the set time, and If the elapsed time does not exceed the set time, the method may further include terminating the operation.

The elapsed time may be determined based on the time of one frame.

According to still another aspect of the present invention, there is provided a method of operating a light source control apparatus, the method of operating a light source control apparatus that controls operations of a plurality of light sources, the method comprising: reading a plurality of light source operating state signals from an external source, Determining whether there is a light source that operates abnormally, using a light source that operates abnormally, outputting an abnormal operation signal to an external device, and when abnormal occurrence information is input from the external device, Determining a type and an occurrence position of an abnormal state based on the output; outputting a control signal for blocking feedback control based on the light source corresponding to the occurrence position when the type of the abnormal state is an open state; and the abnormal state When the kind of state is a short-circuit state, the phase corresponding to the occurrence position Outputting a control signal to turn off the light source.

According to yet another aspect of the present invention, there is provided a method of operating a light source control apparatus, including determining whether a set time has elapsed, reading the plurality of light source operating state signals when the set time has elapsed, and If not, the method may further include determining whether the set time has elapsed.

A method of operating a light source state determination device according to another aspect of the present invention is an operation method of a light source state determination device that determines an abnormal state of a plurality of light sources, and when an abnormal operation signal is input from an external device, the light source is operated by the external device. Requesting a status signal, receiving a light source operating state signal from the external device, reading the light source operating state signal, determining a kind and an occurrence position of an abnormal state, and a kind and generating position of the abnormal state Outputting the abnormal occurrence information based on the external device.

The abnormal state may be an open state or a short state of the light source.

According to still another aspect of the present invention, there is provided a display device including a plurality of pixels arranged in a matrix, a plurality of light source units each having at least one light source operating by a driving voltage, and supplying light to the pixels, A light source state detector for outputting a light source operating state signal corresponding to an operating state of the light source unit using a plurality of output voltages and at least one reference voltage output from the light source unit, and the plurality of light source units using the light source operating state signal And a light source control device that determines an abnormal state of the light source and controls an operation of the light source unit or controls the driving voltage according to the abnormal state.

The light source control device may include: a light source controller configured to detect an abnormal state of the plurality of light source units based on the light source operating state signal and output an abnormal operation signal; and when an abnormal operation signal is input from the light source controller, the light source operating state signal. A light source state determination unit configured to determine the type and occurrence position of the abnormal state and to output abnormal state information to the light source control unit, wherein the light source control unit opens an abnormal state of the light source unit based on the abnormal state information. The controller may determine whether the abnormal state occurs, and determine the position of the light source unit in which the abnormal state occurs, and control the operation of the light source unit corresponding to the abnormal state occurrence position or the driving voltage.

The display device according to the aspect may further include a feedback controller configured to control a driving voltage by sensing a voltage based on a current flowing through the plurality of light source units, wherein the light source controller is configured to be abnormal when the light source unit is in an open state. When the light source unit corresponding to the state occurrence position is turned off and the abnormal state of the light source unit is a short circuit state, it is preferable to block the voltage corresponding to the light source unit at the abnormal state occurrence position from being applied to the feedback control unit.

According to another aspect of the present invention, a backlight unit includes a light source unit having at least one light source operating by a driving voltage, and a light source operating state signal corresponding to an operating state of the light source unit by using an output voltage output from the light source unit. And a light source control device configured to control an operation of the light source unit or to control the driving voltage when the light source unit is in an open state or a short state by receiving an output light source state detection unit and the light source operating state signal.

The light source control device may include: a light source controller configured to detect an abnormal state of the plurality of light source units based on the light source operating state signal and output an abnormal operation signal; and when an abnormal operation signal is input from the light source controller, the light source operating state signal. A light source state determination unit which determines whether the abnormal state is the open state or the short state and a generation position, and outputs abnormal state information corresponding to the type and occurrence position of the determined abnormal state to the light source controller; The light source control unit determines the type of an abnormal state of the light source unit and the position of the light source unit in which the abnormal state occurs based on the abnormal state information. The driving voltage based on the corresponding light source portion It is preferable to stop the control and stop the operation of the light source unit corresponding to the abnormal state occurrence position when the kind of the abnormal state is a short circuit state.

According to this feature, malfunction or damage of the light source unit or the device located behind the light source unit is prevented due to the opening phenomenon or the short circuit phenomenon of the light emitting diode.

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 portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right on" 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.

A liquid crystal display device which is now an example of a display device according to an embodiment of the present invention. A light source driving device and a method thereof 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 embodiment of the present invention.

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 includes a plurality of signal lines G1 -Gn and D1 -Dm and a plurality of pixels PX connected to the plurality of signal lines G1 -Gn and D1 -Dm and arranged in a substantially matrix form. 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 G1 -Gn and D1 -Dm include a plurality of gate lines G1 -Gn for transmitting a gate signal (also called a "scan signal") and a plurality of data lines D1 -Dm for transmitting a data signal. do. The gate lines G1 -Gn extend substantially in the row direction and are substantially parallel to each other, and the data lines D1 -Dm 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. It functions as a sieve. 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 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 D1-Dm of the liquid crystal panel assembly 300 and selects a gray voltage from the gray voltage generator 800 and uses the data voltage D1 -Dm as the data voltage. To apply.

The gate driver 400 is connected to the gate lines G1 -Gn of the liquid crystal panel assembly 300 to receive a gate signal formed of a combination of the gate on voltage Von and the gate off voltage Voff. To apply.

As illustrated in FIG. 3, the backlight unit 900 may include a light source device 970 mounted under the liquid crystal panel assembly 300, a power supply unit 910 for supplying power to the light source device 970, and a light source device. The light source state detection unit 920 connected to the light source state detection unit 920, the light source control unit 930 connected to the light source state detection unit 970, the switching unit 940 connected to the light source device 970, and the switching unit 940 and a power source. And a feedback control unit 950 connected between the supply units 910.

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 illustrated in FIG. 3, the light source device 970 includes a plurality of light emitting diode rows 971 which are a plurality of light source units, a plurality of switching elements SW1-SW4 connected to a plurality of light emitting diode rows 971, and a plurality of light emitting units. A plurality of resistors R1-R4 connected between the switching elements SW1-SW4 and ground are included.

Each LED array 971 includes a plurality of light emitting diodes (LEDs) connected in a forward direction between the power supply unit 910 and each switching element (SW1-SW4).

The plurality of light emitting diode rows 961 may be white light emitting diode rows or alternately mounted red, green, and blue light emitting diode rows. 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 FIG. 3, the number of light emitting diode strings 9710 is four, but this is only one example, and may be added or subtracted as needed, and each light emitting diode string 971 also includes five light emitting diodes (LEDs). This is just an example, and the number of light emitting diodes (LEDs) constituting each of the light emitting diode rows 971 may also vary according to necessity.

Each switching element SW1-SW4 is a three-terminal element having a control terminal, an input terminal, and an output terminal. The control terminal is connected to a light source control device, and the input terminal is connected to each light source unit 971, and an output terminal. Is connected to each resistor (R1-R4).

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

The light source state detector 920 detects an operating state of the light source device 970 and outputs a light source operating state signal.

The light source controller 930 uses the light source operating state signal output from the light source state detector 920 when there is a light emitting diode string 971 that operates abnormally such as an open state or a short state. Operation of the switching unit 940 or the operation of the switching unit 940 is turned off or the feedback control operation based on the LED array 971 is blocked.

The switching unit 940 includes a plurality of switches SW5-SW8 having one input terminal, two output terminals, and a control terminal. Each switch SW5-SW8 has an input terminal connected to one of two output terminals according to the state of a signal applied to the control terminal. One of the output terminals of each switch SW5-SW8 is connected to the feedback control unit 950, but the other output terminal NC is not connected anywhere. This switch SW5-SW8 may be an electronic switch such as a relay.

The feedback controller 950 controls the operation of the power supply unit 910 by using a voltage proportional to a current flowing through the light emitting diode column 971 of the light source device 970.

The backlight unit 900 will be described in more detail later.

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

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 G1 -Gn, D1-Dm, 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 ) It has gray. 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 applied to the horizontal synchronization start signal STH indicating the start of transmission of the output image signal DAT for the group of pixels PX and the data lines D1 -Dm to the liquid crystal panel assembly 300. A load signal LOAD and a data clock signal HCLK to apply a data voltage are included. The data control signal CONT2 is also an inversion signal that inverts the voltage polarity of the data voltage with respect to the common voltage Vcom (hereinafter referred to as " polarity of the data voltage by reducing the voltage polarity of the data voltage with respect to the common voltage "). RVS) may be further included.

The backlight control signal CONT3 includes a plurality of control signals, such as a control signal for controlling the blinking of the light source device 970 and a control signal for controlling the initial operation of the power supply unit 910 based on the vertical synchronization signal Vsync. do.

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. The digital output image signal DAT is converted into an analog data voltage by selecting a gray scale voltage corresponding to and then applied to the data lines D1-Dm.

The gate driver 400 applies a gate-on voltage Von to the gate lines G1 -Gn according to the gate control signal CONT1 from the signal controller 600, and is connected to the gate lines G1 -Gn. Turn on (Q). Then, the data voltage applied to the data lines D1 -Dm is applied to the pixel PX through the switching element Q turned on.

The difference between the data voltage applied to the pixel PX and the common voltage V _com 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, it may be adjusted according to the backlight control signal CONT3 having the magnitude of the converted DC voltage.

The light source device 970 operates in response to the backlight control signal CONT3 and the voltage from the power supply unit 910, so that each LED string 971 blinks.

When the light emitting diode string 971 of the light source device 970 operates, the light source state detecting unit 920 compares the voltage output from each light emitting diode string 971 with a reference signal, and outputs a light source operating state signal to the light source control device 930. )

The light source control device 930 determines an abnormally operating light emitting diode string 971, such as a short circuit state or an open state, based on the light source operating state signal and applies it to the switching elements SW1-SW4 or the switching unit 940. By controlling the states of the control signals S1-S4 and C1-C4, the operation of the LED string 971 and the operation of the feedback control unit 950 which operate abnormally are controlled.

The operation of the light source state detector 920 and the light source control device 930 will be described in detail below.

According to the operation of the backlight unit 900, the light emitted from each light emitting diode (LED) passes through the liquid crystal layer 3 and its polarization changes according to the arrangement of the liquid crystal molecules. 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) to all the gate lines G1 -Gn. In response to the gate-on voltage Von, a data voltage is applied to all the pixels PX to display an image of one frame.

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 may be changed (eg, row inversion and point inversion), or polarities of data voltages applied to one pixel row may be different depending on the characteristics of the inversion signal RVS within one frame. (E.g. column inversion, point inversion).

Next, referring to FIG. 3, the light source state detecting unit 920 and the light source control device 930 according to an embodiment of the present invention will be described in detail.

The light source state detection unit 920 includes a plurality of light source state detection circuits 921 that receive the voltages Vout and the reference voltages Vref1 and Vref2 respectively output from the plurality of light emitting diode rows 971.

The number of these light source state detection circuits 921 is the same as the number of light emitting diode columns 971, but is not limited thereto. The plurality of light source state detection circuits 921 differ only in the connected light emitting diode rows 971, and both have the same structure and operation.

Each light source state detecting circuit 921 has a non-inverting terminal (+) connected to an input terminal of each switching element SW1-SW4, and a comparator OP1 having a first reference voltage Vref1 connected to an inverting terminal (−). And a comparator OP2 connected to an input terminal of each switching element SW1-SW4 to a non-inverting terminal + and a second reference voltage Vref2 to an inverting terminal −.

The first reference voltage Vref1 is a reference voltage for detecting an open state of each LED row 971.

The second reference voltage Vref2 is a reference voltage for detecting a short circuit state of each LED row 971 and has a value greater than the first reference voltage Vref1.

The light source control device 930 includes a light source controller 931 connected to the light source state detector 920 and a light source state determiner 932 connected to the light source controller 931.

The light source controller 931 includes a memory unit 9311 for storing a light source operating state signal output from the light source state detector 920.

 In the present embodiment, the memory unit 9311 may be static random access memory (SRAM), but is not limited thereto.

The structure of the power supply state sensing unit 920 and the light source control device 930 and the operation of the switching unit 940 and the light source device 970 according to the light source control device 930, as shown in FIG. This will be described with reference to.

4 is a flowchart illustrating operations of the light source controller and the light source state determination unit illustrated in FIG. 3.

When a driving voltage output from the power supply unit 910 is applied to the light source device 970, an initial lighting operation of each LED row 971 of the light source device 970 is performed.

In the initial operation, the light source control unit 931 maintains the state of the control signals S1-S4 applied to the switching elements SW1-SW4 to a high level "H" state, so that the initial state of the switching elements SW1-SW4 is maintained. Maintaining the turn-on state, the initial state of the switch (SW5-SW8) of the switching unit 940 controls the state of the control signal (C1-C4) so that the input terminal is connected to the output terminal connected to the feedback control unit 950.

When each light emitting diode string 971 operates, the output voltage of each light emitting diode string 971, which is the voltage Vout between each light emitting diode string 971 and the input terminal of each switching element SW1-SW4, is a light source state. The comparator OP1 and OP2 of the light source state detection circuit 921 of the detector 920 are applied to each of the input output voltages Vout and the respective reference voltages Vref1 and Vref1. Are compared and the comparison results are output to the light source control unit 931.

That is, when the state of the LED array 971 is a normal state, not a short state or an open state, the output voltage Vout is larger than the first reference voltage Vref1 and smaller than the second reference voltage Vref2. Have Therefore, the comparator OP1 outputs a signal in a high level (H) state, and the comparator OP2 outputs a signal in a low level (L) state.

However, when the state of the LED array 971 is open due to disconnection or the like, the voltage Vout output from the LED array 971 has a lower value than the first reference voltage Vref1. That is, when the state of the light emitting diode string 971 is in an open state, since no current flows through the light emitting diode string 971, the output voltage Vout is almost 0V. For this reason, the comparator OP1 outputs a signal in the low level L state, while the comparator OP2 outputs a signal in the low level L state in a normal state.

In addition, when the state of the light emitting diode string 971 is short-circuited due to a short circuit between the anode terminal and the cathode terminal of the light emitting diode LED, the output voltage Vout of the corresponding light emitting diode string 971 is the second reference voltage. It has a value greater than (Vref2). That is, when the state of the LED array 971 is a short-circuit state, the voltage consumed in the LED array 971 decreases, so that the output voltage Vout maintains a value greater than the output voltage in the normal state. For this reason, the comparator OP1 maintains the high level H state in the normal state, but the comparator OP2 outputs a signal in the high level H state.

As described above, when a signal having a corresponding level is output from the light source operating state detection circuit 971 according to the operating state of each light emitting diode string 971 and output to the light source control unit 931 as a light source operating state signal, the light source operating state signal. Is stored in the memory portion 9311.

For this reason, the light source control unit 931 determines whether there is a light emitting diode column 971 that maintains a short state or an open state by using the light source operation state signal stored in the memory unit 9311.

That is, as shown in Fig. 4, the light source control unit 931 reads the light source operating state signal stored in the memory unit 9311 at each set time (S11 and S12), so that there is a light emitting diode string 971 in an abnormal state. In this case, the set time may be determined based on the time of one frame using the vertical synchronization signal Vsync.

When it is determined that there is a light emitting diode string 971 operating in an abnormal state using the read light source operating state signal, the light source controller 931 outputs an abnormal operation signal to the light source state determination unit 932. (S14), the light source state determination unit 932 is operated.

When an abnormal operation signal is input from the light source controller 931, the light source state determination unit 932 requests a light source operation state signal from the light source controller 931 (S15).

For this reason, the light source controller 931 outputs the light source operation state signal stored in the memory unit 9311 to the light source state determination unit 932 (S16).

When the light source operating state signal is input from the light source control unit 931, the input light source operating state signal is read (S17) to determine whether the abnormal state is a short state or an open state and the position of the LED string 971 in which the abnormal state has occurred. It determines (S18).

When the determined abnormal state is the open state (S19), the light source state determination unit 932 compares the elapsed time of the open state with the set time to determine whether the set time has been exceeded (S20).

In this case, the elapsed time may be determined based on the number of frames (time) using the backlight control signal CONT3. Therefore, when it is determined that the open state is continuously made for the set number of frames, the light source state determination unit 932 finally determines the abnormal state of the light source device 970.

In an alternative example, the light source state determination unit 932 may finally determine an abnormal state of the light source device 970 using the number of occurrences of the open state instead of the set time. In this case, when the operation of the backlight unit 900 is determined to be in an open state for more than a set number of frames, the light source state determination unit 932 may finally determine an abnormal state of the light source device 970.

When the elapsed time of the open state does not exceed the set time, the light source state determination unit 932 determines that the voltage drop state occurs instantaneously during normal operation of the light source device 970. Therefore, the light source state determination unit 932 ends the abnormal state determination operation of the light source device 970 (S100).

However, when the elapsed time of the open state exceeds the set time, the light source state determination unit 932 finally determines that there is a light emitting diode string 971 that maintains the open state. It outputs to the control part 931 (S21).

The open occurrence information includes information indicating that an abnormal state is in an open state and location information of the LED array 971 in which the open state has occurred.

Accordingly, the light source control unit 931 is a control signal C1-C4 applied to the switch SW5-SW8 connected to the LED array 971 in which the open state is generated based on the open occurrence information from the light source state determination unit 932. ) Is changed from the initial state (S22), whereby the input terminal of the switch SW5-SW8 contacts the output terminal NC. Therefore, the electrical connection between the LED string 971 and the feedback controller 950 in which the open state occurs is cut off.

Since no signal is applied to the feedback control unit 950 through the switch SW5-SW8 connected to the light emitting diode string 971 in the open state, the feedback control unit 950 applies the light emitting diode string 971 in the open state to the feedback control. Without considering, only the signal (eg, voltage) applied through the normally operating light emitting diode column 971 is considered in the feedback control.

Accordingly, the feedback controller 950 receives only a voltage applied through only the light emitting diode string 971 using a voltage divider (not shown) or the like, and supplies the power supply 910 based on the lowest voltage. Since the output voltage of the power supply unit 910 is controlled by controlling the pulse width, etc. of the pulse width control signal applied to the pulse width control signal, a constant current can always flow through the LED array 971.

As described above, as the LED string 971 in the open state is excluded from the feedback control, the power supply unit 910 is controlled by the voltage output based on the LED string 971 in the open state. The output voltage of the supply unit is abnormally increased to prevent the problem that an overvoltage is applied to the light source device 970.

However, when the abnormal state determined in step S19 is not an open state during the operation of the light source state determination unit 932, the light source state determination unit 932 determines the abnormal state as a short circuit state (S23).

Then, similarly to step S20, in order to determine whether there is a temporary malfunction due to a momentary voltage increase or the like, the light source state determination unit 932 compares the elapsed time of the abnormal state with the set time to determine whether the set time has been exceeded. It is determined (S24). At this time, the elapsed time is set in the same manner as described above. Similarly to what has already been described, in an alternative example, the number of occurrences of a short condition may be used instead of the elapsed time.

If the elapsed time of the abnormal state does not exceed the set time, the light source state determination unit 932 determines that a malfunction occurred temporarily during the operation of the normal light source device 970 and ends the operation (S100).

However, when the elapsed time of the short-circuit state exceeds the set time, the light source state determination unit 932 determines that there is a light emitting diode string 971 that maintains the short-circuit state, and generates short-circuit generation information that is open occurrence information. Output to 931 (S25).

The short circuit occurrence information includes information indicating that the kind of abnormal state is a short circuit state and position information of the LED array 971 in which the short state occurs.

Therefore, the light source control unit 931 is a control signal S1-S4 applied to the switch SW1-SW4 connected to the LED array 971 in which the short circuit condition is generated based on the short circuit occurrence information from the light source state determination unit 932. Is changed to the low level L, and the switches SW1 to SW4 are turned off. As a result, since the LED string 971 having a short circuit is turned off, the component located at the rear end of the light source device 970 is prevented from malfunctioning or breaking due to heat generation due to the short circuit phenomenon.

In addition, since the light source state determination unit 932 operates only when the light source unit 971 is in an abnormal state, the operation speed of the light source control device 930 is improved and unnecessary power consumption of the light source control device 930 is reduced.

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 embodiment of the present invention.

4 is a flowchart illustrating operations of the light source controller and the light source state determination unit illustrated in FIG. 3.

* 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 state detection unit

930: light source control device 931: light source control unit

932: light source state determination unit 9311: memory unit

940: switching unit 950: feedback control unit

970: light source device OP1, OP2: comparator

SW1-SW4: switching means SW5-SW8: switch

Claims (25)

A driving device for driving a light source unit operated by a driving voltage, A light source state detector for outputting a light source operating state signal corresponding to an operating state of the light source unit by using the output voltage output from the light source unit, and A light source control device which receives the light source operation state signal and controls the operation of the light source unit or the driving voltage when the light source unit is in an abnormal state Light source driving device comprising a. In claim 1, The light source control device, A light source controller which detects an abnormal state of the plurality of light source units based on the light source operating state signal and outputs an abnormal operation signal; and When an abnormal operation signal is input from the light source controller, the type and occurrence position of the abnormal state are determined using the light source operation state signal, and the abnormal state information corresponding to the type and occurrence position of the determined abnormal state is obtained. Light source state determination unit output to the control unit Including, The light source control unit determines the type of an abnormal state of the light source unit and the position of the light source unit in which the abnormal state occurs based on the abnormal state information, so that the operation of the light source unit corresponding to the abnormal state occurrence position or the abnormal normal state occurrence position To stop the driving voltage control based on the light source unit corresponding to Light source driving device. 3. The method of claim 2, The abnormal state is one of an open state and a short state. 4. The method of claim 3, A feedback control unit for sensing the voltage based on the current flowing through the plurality of light source unit to control the driving voltage, The light source control unit turns off the light source unit corresponding to the abnormal state occurrence position when the abnormal state of the light source unit is open, and the voltage corresponding to the light source unit at the abnormal state occurrence position when the abnormal state of the light source unit is a short circuit state. Blocking this from being applied to the feedback controller Light source driving device. In claim 4, A plurality of switching means each connected between the plurality of light source units and ground; and A switching unit including a plurality of switches respectively connected between the plurality of light source units and the feedback; More, The light source control unit turns off the switching means corresponding to the abnormal state occurrence position among the plurality of switching means when the abnormal state of the light source unit is open, and the plurality of switches when the abnormal state of the light source unit is a short circuit state. Controlling the switch corresponding to the abnormal state occurrence position to block electrical connection between the light source unit and the feedback control unit. Light source driving device. The method according to any one of claims 3 to 5, And the light source state detection unit outputs the light source operating state signal using the output voltage and at least one reference voltage. In claim 6, The at least one reference voltage includes a first reference voltage and a second reference voltage different from the first reference voltage, The light source state detector detects an open state of the plurality of light source units using the plurality of output voltages and the first reference voltage, and short-circuits the plurality of light source units using the plurality of output voltages and the second reference voltage. To detect the condition Light source driving device. In claim 7, And the first reference voltage is smaller than the second reference voltage. In claim 7, The light source state detecting unit includes a plurality of first comparators for comparing the plurality of output voltages and the first reference voltage and a plurality of second comparators for comparing the plurality of output voltages and the second voltage. 3. The method of claim 2, The light source controller includes a memory unit for storing the light source operating state signal. In claim 1, The light source driving apparatus includes at least one light emitting diode. A driving method of a light source driving apparatus including a light source control unit and a light source state determination unit for controlling an abnormal state of the light source using a light source operating state signal corresponding to an operating state of a plurality of light sources. The light source control unit, Reading the light source operating state signal; Determining whether an abnormal state occurs in at least one of the plurality of light sources based on the light source operating state signal, and Outputting an abnormal operation signal to the light source state determination unit when an abnormal state occurs in at least one of the plurality of light sources; Including, The light source state determination unit, Requesting the light source operating state signal to the light source controller when the abnormal operation signal is received; When the light source operating state signal is input from the light source control unit, determining a type and an occurrence position of an abnormal state based on the light source operating state signal, and Outputting abnormal occurrence information to the light source controller based on the type of abnormal state and the occurrence position; Including, The light source controller may further include determining a type and a location of the abnormal state and outputting a control signal based on the abnormal occurrence information. A method of driving a light source driving device. The method of claim 12, And the abnormal state is one of an open state and a short state. The method of claim 13, The control signal output step, Outputting a control signal for blocking feedback control based on the light source corresponding to the generation position when the kind of the abnormal state is the open state, and Outputting a control signal to turn off the light source corresponding to the generation position when the kind of the abnormal state is the short circuit state; Method of driving a light source driving apparatus comprising a. The method of claim 12, The light source state determination unit, Comparing the elapsed time for the abnormal state of the determined kind with a set time; Outputting the abnormal occurrence information to the light source controller when the elapsed time exceeds a set time; and If the elapsed time does not exceed the set time, terminating the operation Driving method of a light source driving device further comprising. 16. The method of claim 15, And the elapsed time is determined based on the time of one frame. An operation method of a light source control device that controls the operation of a plurality of light sources, Reading a plurality of light source operating status signals from the outside, Determining whether there is a light source that operates abnormally using the light source operating state signal; Outputting an abnormal operation signal to an external device when there is a light source that operates abnormally; Determining an abnormal state type and a generation position based on the abnormal occurrence signal when abnormal occurrence information is input from the external device; Outputting a control signal for blocking feedback control based on the light source corresponding to the generation position when the kind of the abnormal state is an open state, and Outputting a control signal to turn off the light source corresponding to the generation position when the kind of the abnormal state is a short circuit state; Method of operating a light source control device comprising a. The method of claim 17, Determining whether the set time has elapsed, Reading the plurality of light source operating state signals when the set time elapses, and If the set time has not passed, determining whether the set time has elapsed Operation method of a light source control device further comprising. An operation method of a light source state determination device for determining an abnormal state of a plurality of light sources, Requesting a light source operation status signal to the external device when an abnormal operation signal is input from an external device, When the light source operating state signal is received from the external device, reading the light source operating state signal to determine a kind and an occurrence position of an abnormal state; and Outputting abnormal occurrence information to the external device based on the abnormal state type and occurrence position; Method of operating a light source state determination device comprising a. The method of claim 19, And the abnormal state is an open state or a short state of the light source. A plurality of pixels arranged in a matrix form, A plurality of light source units each having at least one light source operated by a driving voltage and supplying light to the pixel; A light source state detector for outputting a light source operating state signal corresponding to an operating state of the light source unit by using a plurality of output voltages and at least one reference voltage output from the plurality of light source units, and A light source control device which determines an abnormal state of the plurality of light source units by using the light source operating state signal and controls the operation of the light source unit or controls the driving voltage according to the abnormal state. Display device comprising a. The method of claim 21, The light source control device, A light source controller which detects an abnormal state of the plurality of light source units based on the light source operating state signal and outputs an abnormal operation signal; and When an abnormal operation signal is input from the light source controller, the light source state determination unit determines the type and occurrence position of the abnormal state by using the light source operating state signal and outputs abnormal state information to the light source controller. Including, The light source controller determines whether the abnormal state of the light source unit is an open state or a short state based on the abnormal state information, determines the position of the light source unit in which the abnormal state occurs, and determines the operation of the light source unit corresponding to the abnormal state occurrence position. To control the driving voltage Display device. The method of claim 22, A feedback control unit for sensing the voltage based on the current flowing through the plurality of light source unit to control the driving voltage, The light source control unit turns off the light source unit corresponding to the abnormal state occurrence position when the abnormal state of the light source unit is open, and the voltage corresponding to the light source unit at the abnormal state occurrence position when the abnormal state of the light source unit is a short circuit state. Blocking this from being applied to the feedback controller Display device. A light source unit having at least one light source each operated by a driving voltage, A light source state detector for outputting a light source operating state signal corresponding to an operating state of the light source unit by using the output voltage output from the light source unit, and A light source control device that controls the operation of the light source unit or the driving voltage when the light source unit is in an open state or a short state by receiving the light source operating state signal. A backlight unit comprising a. The method of claim 24, The light source control device, A light source controller which detects an abnormal state of the plurality of light source units based on the light source operating state signal and outputs an abnormal operation signal; and When an abnormal operation signal is input from the light source controller, the light source operation state signal is used to determine whether the abnormal state is the open state or the short circuit state and the occurrence position, and corresponds to the type and occurrence position of the determined abnormal state. A light source state determination unit outputting abnormal state information to the light source control unit Including, The light source controller determines the type of an abnormal state of the light source unit and the position of the light source unit in which the abnormal state occurs based on the abnormal state information, and corresponds to the abnormal normal state occurrence position when the kind of the abnormal state is in an open state. Stopping the driving voltage control based on the light source unit to stop the operation of the light source unit corresponding to the abnormal state occurrence position when the kind of the abnormal state is a short circuit state; Backlight unit.

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