KR20120133814A - Apparatus and method for driving of light emitting diode array, and liquid crystal display device using the same - Google Patents

Abstract

PURPOSE: An apparatus and a method for driving a light emitting diode array, and a liquid crystal display device using the same are provided to delete an internal pressure compensation configured in a current sink shift and to prevent the damage of the current sink shift. CONSTITUTION: Switching units are connected between a light emitting diode string(812) and a ground power. The switching units switch the current value flowing through the light emitting diode string. An LED array driver(920) controls the switching unit. An off current is discharged if the off dimming control signal is received from the LED array driver. A power supply unit(910) apples an array driving voltage between the light emitting diode string and a power source. [Reference numerals] (910) Power supply unit; (921) Controller; (922) Reference voltage generating unit; (AA) Dimming control signal

Description

A light emitting diode array driving apparatus and method and a liquid crystal display using the same {APPARATUS AND METHOD FOR DRIVING OF LIGHT EMITTING DIODE ARRAY, AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode array driving apparatus, and more particularly, to an apparatus and method for driving a light emitting diode array used in a backlight unit of a liquid crystal display and a liquid crystal display using the same.

Flat panel displays are widely used in mobile devices that require miniaturization and low power, as well as large digital TVs that require weight and thickness reduction.

Among them, a liquid crystal display (LCD) is most widely used among flat panel displays due to its advantages of being applicable to small devices and large devices.

On the other hand, the liquid crystal display requires a light source called a backlight unit (BLU) on the back of the liquid crystal panel because the panel does not emit light by itself.

Cold Cathode Fluorescent Lamps (CCFLs) and External Electrode Fluorescent Lamps (EEFLs) are widely used as the light source of the backlight unit. Recently, the luminance is sufficiently high, the power consumption and the manufacturing cost are high. Low light emitting diodes (LEDs) have been developed to replace light sources as described above.

That is, a backlight unit using a light emitting diode (LED) does not need to use an expensive diffusion film or the like, and unlike an fluorescent lamp, an inverter is not required, which reduces manufacturing costs, is advantageous for large size, and also reduces thickness and weight. In addition, it is also widely used because it can reduce power consumption and environmental problems.

Meanwhile, in the backlight unit using the light emitting diodes, a plurality of light emitting diodes are configured in the form of a light emitting diode string, and the light emitting diode string is formed of a light emitting diode array in which a plurality of light emitting diode strings are collected.

1 is an exemplary view showing the configuration of a conventional LED array driving apparatus.

The conventional LED array driving apparatus includes a power supply unit 20 and an LED D-IC 10 as shown in FIG. 1. Here, the light emitting diode array 40 is formed by connecting a plurality of light emitting diode strings 30 in which the light emitting diodes are connected in series. In addition, one end of each LED string 30 is commonly connected to the output terminal of the power supply 20, and the other end is connected to the ground power source GND through the resistor Rs. That is, each of the plurality of light emitting diode strings 30 is electrically connected in parallel between the output terminal of the power supply unit 20 and the ground power source GND. In addition, each of the plurality of LED strings 30 includes a plurality of LEDs connected in series so as to emit light by a current flowing from the power supply 20 to the ground power source GND.

The power supply unit 20 generates an array driving voltage VLED for driving the LED array 40 under the control of the LED D-IC 10, and generates the generated array driving voltage VLED for each light emitting diode. A function of supplying the string 30 is performed.

The LED D-IC 10 controls the level of the array driving voltage VLED output from the power supply unit 20 (constant voltage driving method), or controls the current flowing through the light emitting diode string (constant current driving method) to emit light. The diode array 40 performs a function for driving stably.

On the other hand, in the above-described conventional light emitting diode array driving apparatus, the current sink stage of the LED D-IC is a breakdown voltage process corresponding to the voltage specification of the light emitting diode (LED Anode) of the light emitting diode array 40. Need condition.

For example, when the current flowing through the LED of the LED array is ideally '0', the array driving voltage VLED supplied from the power supply unit 20 to the LED array 40 is LED D. Since all are applied to the current sink stage of the IC 10, the LED D-IC 10 applied to the conventional LED array driving apparatus should be configured to satisfy the breakdown voltage condition as much as the array driving voltage VLED. Therefore, the conventional LED array driving apparatus uses a method of increasing the IC manufacturing process breakdown voltage of the LED D-IC current sink stage so that the LED D-IC 10 can satisfy the LED driving voltage VLED. have.

However, as described above, the method of raising the internal pressure of the manufacturing process of the LED D-IC may cause a problem of raising the unit cost of the LED D-IC 10.

Disclosure of Invention The present invention has been made in view of the above-described problem, and even though an off-dimming control signal for turning off a light emitting diode array is applied, a light emitting diode array driving apparatus and method for flowing a predetermined amount of off current to the light emitting diode array And it is a technical problem to provide a liquid crystal display device using the same.

A light emitting diode array driving apparatus according to the present invention for achieving the above technical problem is connected between each of the light emitting diode string constituting the light emitting diode array and a base power supply for switching a current value flowing through the light emitting diode string Switching unit; A light emitting diode array driver for controlling the switching unit so that a predetermined off current flows through the switching unit when an off-dimming control signal for turning off the light emitting diode string is received; And a power supply unit for applying an array driving voltage between each of the light emitting diode strings and the electromotive power source.

According to another aspect of the present invention, there is provided a light emitting diode array driving method comprising: applying an array driving voltage to a plurality of light emitting diode strings constituting a light emitting diode array; When an off-dimming control signal for turning off the light emitting diode string is received, a reference voltage for causing an off current to flow through the light emitting diode string while the light emitting diode string does not emit light is connected to the light emitting diode string. Applying to a switching unit connected between the base power sources; And when the on-dimming control signal for turning on the light emitting diode string is received, applying a steady voltage to the light emitting diode string to emit light.

A liquid crystal display using the light emitting diode array driving apparatus according to the present invention for achieving the above technical problem, the panel including a plurality of liquid crystal cells formed for each region defined by the intersection of a plurality of gate lines and a plurality of data lines. ; A panel driver for driving the data line and the gate line to display an image corresponding to input data from the outside on the panel; And a backlight unit for irradiating light to the panel, wherein the backlight unit includes the light emitting diode array driving device according to any one of claims 1 to 6.

According to the above solution, the present invention provides the following effects.

That is, according to the present invention, even when an off-dimming control signal for turning off the light emitting diode array is applied, a certain amount of off current flows to the light emitting diode array, so that all of the array driving voltages applied to the light emitting diode array are applied to the light emitting diode array. It provides an effect that can be prevented from being applied to the light emitting diode driver (LED D-IC) for controlling the turn off.

In addition, the present invention can reduce the process conditions of the current sink (Current Sink) stage of the LED driving unit (LED D-IC), and withstand voltage compensation circuit configured in the current sink stage of the LED D-IC (LED D-IC) In this case, the manufacturing cost of the liquid crystal display device can be reduced, and the damage of the current sink stage of the LED driving unit LED D-IC can be prevented.

1 is an exemplary view showing the configuration of a conventional LED array driving apparatus.
2 is a configuration diagram of a liquid crystal display device using a light emitting diode array driving apparatus according to the present invention.
Figure 3 is a configuration diagram of an embodiment of a light emitting diode array driving apparatus according to the present invention.
4 is an exemplary view showing a simulation result by the LED array driving apparatus according to the present invention.
5 is an exploded perspective view showing a liquid crystal display device using the light emitting diode array driving apparatus according to the present invention as a whole.

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

2 is a configuration diagram of a liquid crystal display device using a light emitting diode array driving apparatus according to the present invention.

As shown in FIG. 2, the liquid crystal display using the LED array driving apparatus according to the present invention includes a panel 102, a timing controller 108, a data driver 106, a gate driver 104, and a backlight unit 800. ) Is included. Here, the data driver 106 and the gate driver 104 are collectively referred to as a panel driver, and the backlight unit 800 includes a light emitting diode array 810 including a plurality of light emitting diode strings, and a light emitting diode for driving the light emitting diode array. An array drive device 900 is included.

First, the panel 102 is provided with liquid crystal molecules dropped between two glass substrates. In this panel, m × n liquid crystal cells Clc are arranged in a matrix by a cross structure of the data lines D1 to Dm and the gate lines G1 to Gn.

M data lines D1 to Dm, n gate lines G1 to Gn, TFTs, and pixel electrodes of the liquid crystal cell Clc connected to the TFT are formed on the lower glass substrate of the panel.

A black matrix, a color filter, and a common electrode are formed on the upper glass substrate of the panel. The common electrode is formed on the upper glass substrate in a vertical electric field driving method such as a TN (Twisted Nematic) mode and a VA (Vertical Alignment) mode, and a horizontal electric field such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) Is formed on the lower glass substrate together with the pixel electrode in the driving method. A polarizing plate having an optical axis orthogonal to each other is attached to the upper glass substrate and the lower glass substrate of the panel, and an alignment layer for setting the pretilt angle of the liquid crystal is formed on the inner surface in contact with the liquid crystal.

Next, the timing controller 108 receives timing signals such as vertical / horizontal synchronization signals (Vsync, Hsync), data enable, clock signal (CLK), and the like, and the data driver 106 and the gate driver 104. Control signals for controlling the operation timing of the < RTI ID = 0.0 > These control signals include a gate start pulse (GSP), a gate shift clock signal (GSC), a gate output enable signal (GOE), and a source start pulse (SSP). , A source sampling clock (SSC), a source output enable signal (SOE), a polarity control signal (POL), and the like. In addition, the timing controller rearranges the input digital video data RGB to the panel 102 and supplies the digital video data RGB to the data driver 106.

Next, the data driver 106 includes a plurality of gate drive ICs (not shown) including a shift register, first and second latches, a digital-to-analog converter, and an output buffer that are connected dependently between the input line and the data line. It consists of. The data driver latches the data RGB under the control of the timing controller 108 and converts the data into an analog positive / negative gamma compensation voltage to generate a positive / negative data voltage and convert the data voltage into the data lines. It supplies to (D1-Dm).

Next, the gate driver 104 includes a shift register and a level shifter for converting the output signal of the shift register into a swing width suitable for TFT driving of the liquid crystal cell, and an output buffer connected between the level shifter and the gate lines GL1 to GLn. Each of the plurality of gate drive integrated circuits includes a scan pulse having a pulse width of approximately one horizontal period and sequentially outputs to the gate lines.

Meanwhile, as described above, the data driver and the gate driver may be collectively referred to as a panel driver.

Lastly, since the panel does not emit light by itself, the backlight unit 800 is disposed at the rear of the panel and outputs light in the direction of the panel. The backlight unit 800 is directly aligned with the edge type according to the arrangement of the light sources. It can be classified as (Direct Type). Meanwhile, the present invention uses a light emitting diode as a light source, and the light source using the light emitting diode includes a light emitting diode array 810 in which a plurality of light emitting diode strings in which a plurality of light emitting diodes are arranged side by side are gathered. Can be. Therefore, hereinafter, a liquid crystal display device using a direct type backlight unit will be described as an example, but the present invention can also be applied to a liquid crystal display device using a photometric type backlight unit having at least two light emitting diode strings. In addition, hereinafter, the LED array refers to a light source.

The backlight unit 800 includes a light emitting diode array driving apparatus 900 for driving the light emitting diode array as described above. That is, the LED array driving apparatus 900 controls the level of the array driving voltage VLED output from the power supply unit (not shown), or controls the current flowing through the LED string (constant current driving method). In this case, the light emitting diode array 810 is stably driven. In particular, in the present invention, even when an off-dimming control signal for turning off at least one light emitting diode string is received, the light emitting diode array is connected to the light emitting diode array. By allowing a certain amount of off current to flow, all the array driving voltages applied to the LED array are prevented from being applied to the LED array driver (LED D-IC) that controls the turn-off of the LED array. .

That is, the LED array driving apparatus 900 according to the present invention is applied to a liquid crystal display device driven by a dimming control method, and is configured to turn off at least one LED string (here, the LED string). Off means that the LED string does not emit light) (hereinafter, the same), even if an off-dimming control signal is received, turning off the LED string so that no current flows to the LED string. In addition, a predetermined minute current such that the light emitting diode does not emit light flows through the light emitting diode string, so that a high voltage is applied to the light emitting diode controller (LED D-IC) included in the light emitting diode array driving apparatus 900. Is applied to damage the LED array driver. The functions to prevent.

Meanwhile, the power supply unit as described above included in the LED array driving apparatus 900 not only performs a function of supplying power required for the LED array 810, but also corresponds to other components as described above. It is also possible to supply the power required to drive the components.

3 is a configuration diagram of an LED array driving apparatus according to an embodiment of the present invention. 4 is an exemplary view showing a simulation result by the LED array driving apparatus according to the present invention.

According to the LED array driving apparatus 900 according to the present invention, in response to the backlight dimming control, when the off dimming control signal is transmitted so that the light emitting diode 811 does not emit light, the LED array 810 is transmitted. By allowing a predetermined minute current (hereinafter, simply referred to as an “off current”) that the light emitting diode of the light emitting diode array 810 does not emit light to flow to the light emitting diode array 810, the light emitting diode array and the base power supply All of the array driving voltages VLED of the power supply unit 910 applied between the GNDs are prevented from being applied to the LED array driving unit (LED D-IC) 920.

The light emitting diode array 810 includes a plurality of light emitting diode strings 812 connected in parallel as described above, and a plurality of light emitting diodes 811 are connected in series to each of the plurality of light emitting diode strings. It is. Here, the plurality of light emitting diodes may emit, for example, one of primary colors of red, green, and blue, a color expressed by combining three primary colors, or white light.

In addition, the dimming control signal refers to a signal generated by the backlight dimming control method for adjusting the brightness of the backlight unit according to the image.

That is, the image quality of the liquid crystal display device depends on the contrast characteristic, and since the method of controlling the data voltage applied to the liquid crystal layer of the panel to modulate the light transmittance of the liquid crystal layer has a limitation in improving the contrast characteristic, the contrast characteristic In order to improve this, a backlight dimming control method for adjusting the brightness of the backlight unit according to an image has been developed. Meanwhile, the backlight dimming control method includes a global dimming method of turning off the entire light emitting diode array 810 of the backlight unit to adjust the luminance of the entire display surface, and locally to adjust the luminance of the display surface. There is a local dimming method for turning off only a portion of the light emitting diode string 812 of the light emitting diode array, wherein the dimming control signal is a light emitting diode in a timing controller or a separate controller to execute the dimming control method as described above. Refers to a control signal transmitted to the array driver (LED D-IC) 920.

In detail, the LED array driving unit (LED D-IC) 920 emits light by turning on / off a current flowing through the LED array 810 according to a dimming control signal transmitted from a timing controller or a separate controller. The light emitting diodes of the diode array 810 may emit light or may not emit light. Hereinafter, preventing the light emitting diode from emitting light means to turn off the light emitting diode array or the light emitting diode string, and to cause the light emitting diode to emit light means to turn the light emitting diode array or the light emitting diode string on. For example, the dimming control signal for the former is called an off dimming control signal, and the dimming control signal for the latter is called an on dimming control signal.

As described above, the dimming control method includes a global dimming method and a local dimming method. Hereinafter, for convenience of description, only a specific light emitting diode string 812 of the LED array 810 emits light. The invention is described by way of example of a method of emitting or not emitting light. Thus, in the case of using the global dimming method, the present invention described below except that the LED array driver 920 simultaneously controls all the LED strings 812 of the LED array 810 according to the present invention. The invention can be applied as it is.

In order to achieve the above object, the LED array driving apparatus 900 according to the present invention is connected between each of the plurality of LED strings 812 and the detection resistor 940, as shown in FIG. A switching unit 930 having a gate or base terminal connected to the LED array driver 920 and an off dimming control signal for turning off at least one LED string are input to the switching unit. Applying a reference voltage capable of flowing off current) to the switching unit to apply the array driving voltage (VLED) between the light emitting diode array driver 920 and the light emitting diode array and the ground power supply (GND) for maintaining the switching unit on. It is configured to include a power supply 910 for.

First, the switching unit 930 is for flowing a current transmitted from the light emitting diode string to the ground power supply (GND). When the on-dimming control signal for turning on the light emitting diode string is applied, the switching unit 930 is provided from the light emitting diode array driving unit 920. A steady voltage is applied to allow a steady current to flow.

However, when the off-dimming control signal for turning off the light emitting diode string is applied, the switching unit 930 receives a reference voltage from the light emitting diode array driver 920 and performs a function of allowing a predetermined off current to flow.

Here, the normal current refers to a current flowing through the switching unit when the light emitting diode string is operated in an on state and emits light, and the off current refers to a light emitting diode in which the light emitting diode string is operated in an off state and does not emit light. The minimum current that can flow through the string.

That is, in general, when the light emitting diode string is turned off, current does not flow through the light emitting diode string, but in this case, all of the array driving voltages to be applied to the light emitting diode string are applied to the light emitting diode array driver 920 to emit light. The diode array driver may be damaged. Therefore, in order to solve this phenomenon, even if the LED string is turned off, a minimum current (off current) is allowed to flow through the LED string and the switching unit so that the LED string does not emit light. A portion of the array driving voltage VLED is applied to the light emitting diode string 812 to reduce the magnitude of the voltage applied to the LED array driving unit 920.

Meanwhile, in order to achieve the above object, the switching unit 930 applied to the present invention may be configured with various types of switches, and in particular, may be configured using a transistor as shown in FIG. 3.

That is, the transistor is turned on according to the magnitude of the voltage applied to the gate or the base so that a current flows between the source and the drain or the collector and the emitter. The transistor constituting the switching unit will be described below through the gate or the base. A normal voltage or a reference voltage is applied from the light emitting diode array driver 920 to perform a normal current or an off current.

On the other hand, the normal current and the off current may vary depending on the structure of the light emitting diode string and the number and characteristics of the light emitting diodes constituting the light emitting diode string. The off current refers to a current having an intensity of a current that can flow through the light emitting diode string in a state where the light emitting diode string does not emit light.

Next, the LED array driver 920 controls the amount of current flowing through the LED string in the normal state to which the ON dimming control signal is applied (constant current driving method), or controls the voltage applied to the LED string (constant voltage). Driving Method) A light emitting diode string is operated in a normal state to emit light, and may include a controller 921 and a reference voltage generator 922.

First, the method of driving the LED array driver 920 in the normal state to which the on-dimming control signal is applied will be described below.

That is, the light emitting diode array driver 920 may be driven by a constant current driving method or a constant voltage driving method to maintain a characteristic of the light emitting diode string by continuously flowing a steady current having a constant intensity through the light emitting diode string. The constant current driving method detects a current value flowing through the light emitting diode string and controls the normal current to flow through the constant current driving method. The constant voltage driving method detects a voltage value flowing through the light emitting diode string and through this, an array of a power supply unit. The driving voltage VLED is varied. The light emitting diode array driver 920 applied to the present invention may be configured in any of the above manners.

Meanwhile, the present invention includes a detection line 950 and a detection resistor 940 as shown in FIG. 3 to detect a current value or a voltage value flowing through the light emitting diode string as described above. That is, the LED array driver 920 is connected to the detection line 950 for detecting a current value or a voltage value. The detection line 950 may be connected to a node between the switching unit 930 and the detection resistor 940 and the light emitting diode array driving unit to apply a current or voltage flowing through the switching unit to the light emitting diode array driving unit.

Here, when the LED array driver (LED D-IC) 920 uses a constant current driving method, a separate constant current transistor, which is not shown in FIG. 3, may be provided in the LED array driver or may be connected in series with the switching unit. However, in the following, the present invention will be described as the transistors constituting the switching unit also perform the functions of the constant current transistor.

That is, when the LED array driving unit 920 is driven by the constant current driving method, the steady state current flows by applying a steady voltage to the switching unit in a normal state to which the on-dimming control signal is applied, while detecting through the detection line. When the current value is out of the range of the preset current value, a variable voltage may be applied to the switching unit so that the normal current flows through the switching unit.

Similarly, when the LED driving unit 920 is driven by the constant voltage driving method, the normal voltage is applied to the switching unit in the normal state where the on-dimming control signal is applied to allow the steady current to flow, and through the detection line. When the detected voltage value is out of the range of the preset voltage value, the power supply unit 910 may be controlled to change the array driving voltage VLED.

In the above description, after detecting the current value or the voltage value using the current or voltage applied through the detection line 950, the function of substantially controlling the switching unit 930 or the power supply unit 910 accordingly The controller 921 of the LED array driver 920 may perform the function, and the reference voltage generator 922 may perform a function of generating a normal voltage, a variable voltage, a reference voltage, and the like under the control of the controller.

That is, the controller 921 detects a current value or a voltage value, requests the reference voltage generator 922 to generate a necessary voltage, and performs a function of applying the requested voltage to the switching unit. As described above, when the off-dimming control signal is received from the timing controller or a separate controller, the reference voltage generator may be requested to generate a reference voltage, and then a function of applying the generated reference voltage to the switching unit may be performed.

Second, the method of driving the light emitting diode array driver 920 in the off state to which the off-dimming control signal is applied is as follows.

That is, the LED array driver 920 drives the reference voltage generator 922 when an off-dimming control signal is applied by the timing controller or a separate controller to turn off at least one LED string of the LED array. By generating a reference voltage, by applying the generated reference voltage to the switching unit 930, it is possible to perform a function to flow the off current through the switching unit.

Finally, the power supply unit 910 is for supplying the array driving voltage (VLED) to the light emitting diode array, in particular, in the constant voltage driving method, the array driving voltage (VLED) under the control of the light emitting diode array driving unit 920. The light emitting diode array 810 may be applied to the light emitting diode array 810.

On the other hand, in the light emitting diode array driving apparatus according to the present invention as described above, the simulation result of the V_collector voltage (LED D-IC breakdown voltage specification) of the transistor constituting the switching unit according to the light emitting diode current is shown in Figure 4,

That is, the section denoted by A in FIG. 4 is a section in which the light emitting diode string is turned on and a steady current flows through the light emitting diode string to emit light, and the array is formed on the light emitting diode string 812 by V = IR (I ≠ 0). As the driving voltage VLED is applied, it can be seen that the collector voltage V_collector of the transistor forming the switching unit is about 2V or less.

In addition, the section denoted by B in FIG. 4 is a section in which the light emitting diode string is turned off according to the off-dimming control signal so that off current flows to the light emitting diode string, but no light is emitted. Since the off current flows even when it is turned off, a certain voltage drop is applied to the light emitting diode string by V = IR (I ≠ 0). Thus, it can be seen that the collector voltage V_collector of the transistor is confirmed to be about 15V. have.

That is, in an ideal case not according to the present invention, when the light emitting diode string is turned off, the current flowing to the light emitting diode string becomes 0, and thus, the array driving voltage VLED supplied from the power supply unit 910 to the collector of the transistor 930. A voltage of about 53V is applied, but according to the present invention, a voltage of about 15V is applied to the collector of the transistor 930 due to the voltage drop in the light emitting diode string 812, whereby the light emitting diode It is not necessary to increase the breakdown voltage specification of the array driver (LED D-IC) 920.

FIG. 5 is an exploded perspective view of the entire liquid crystal display using the LED array driving apparatus according to the present invention.

That is, the liquid crystal display using the light emitting diode array driving apparatus according to the present invention, as shown in FIG. 5, includes a plurality of light emitting diode strings 812 on which a plurality of light emitting diodes 811 are arranged. A light source formed by the diode array 810, a cover bottom 870 on which the light source is mounted, a light guide plate 820 disposed at the top of the light source to change the light emitted from the light source into planar light, and the light guide plate The optical sheet unit 830 disposed on the upper side, and disposed on the upper surface of the optical sheet unit and formed of an upper substrate and a lower substrate to be assembled with a panel 102 for outputting an image and a cover bottom to mount the components therein. It may be configured to include a top cover (300) that is formed.

As described above, the top cover 300 is engaged with the cover bottom to perform a function of embedding the liquid crystal display panel and other components between the top cover and the cover bottom. Although not shown in the drawings, a support main may be further provided to align the edges of the optical sheet unit and the liquid crystal display panel, and in this case, the top cover and the cover bottom may support the support main. Can be assembled.

The panel 102 drives the liquid crystal injected between the upper plate and the lower plate by using a voltage applied to the lower plate, thereby outputting an image according to the amount of light transmitted from the light source, and may be configured in various forms.

Meanwhile, among the above components, the backlight unit 800 includes a light emitting diode array (light source) 810 composed of a plurality of light emitting diode strings 812 disposed on an inner surface of the cover bottom 870, and a light guide plate covering a light source. 820, an optical sheet unit 830 disposed on an upper surface of the light guide plate or disposed at a predetermined distance from the light guide plate, and the light emitting diode array driving apparatus 900 according to the present invention as described above.

As described above, the cover bottom 870 is fastened to the top cover in a state where the light source is mounted to perform the function of fixing the components.

The optical sheet unit 830 diffuses the light that has passed through the light guide plate or allows the light that has passed through the light guide plate to enter the liquid crystal display panel vertically. The optical sheet unit 830 may include a diffusion plate, a diffuser sheet, It may be variously formed, including a prism sheet.

In the plurality of light emitting diodes arranged in the light emitting diode array (light source) 810, a plurality of RGB LEDs emitting red (R), G (green), and B (blue) color light are arranged according to a predetermined rule. White light can be realized by color mixing.

Although not shown in the drawings, the LED array driving apparatus 900 as described above is connected to the LED array 810 and mounted on the cover bottom 870.

That is, according to the present invention, when an off-dimming control signal for any one of the light emitting diode strings 810 formed of the plurality of light emitting diode strings 812 is received, an off current flows to the light emitting diode string. As a result, all of the array driving voltages VLED to be applied to the LED string 812 are prevented from being applied to the LED array driver 920.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

800: backlight unit 810: light emitting diode array
811: light emitting diode 812: light emitting diode string
900: light emitting diode array driving device 910: power supply
920: LED array driver 921: controller
922: reference voltage generator 930: switching unit
940: detection resistance 950: detection line

Claims (11)

A plurality of switching units connected between each light emitting diode string constituting the light emitting diode array and a base power source to switch a current value flowing through the light emitting diode string;
A light emitting diode array driver for controlling the switching unit so that a predetermined off current flows through the switching unit when an off-dimming control signal for turning off the light emitting diode string is received; And
And a power supply unit for applying an array driving voltage between each of the LED strings and the electromotive power source. The method of claim 1,
The switching unit includes:
And a transistor formed such that the off current flows through the LED string by a gate or base voltage applied from the LED array driver. The method of claim 2,
A detection resistor connected between the switching unit and the base power source; And
A detection line connected to a node between the detection resistor and the switching unit and the light emitting diode array driving unit,
The LED array drive unit,
When an on-dimming control signal for turning on the light emitting diode string is received, a current value is detected through the detection line to control the switching unit according to the detected current value so that a predetermined normal current flows to the switching unit. A light emitting diode array driving device. The method of claim 3, wherein
The light emitting diode array control unit,
A reference voltage generator for generating a reference voltage for allowing the off current to flow through the switching unit or a voltage for allowing the steady current to flow; And
And a controller for driving the reference voltage generator to generate the reference voltage when the off-dimming control signal is received, and transmitting the generated reference voltage to the switching unit so that the off current flows to the switching unit. Diode array drive. The method of claim 1,
The light emitting diode drive control unit,
The switching unit controls the switching unit so that the predetermined off current flows only in the switching unit connected to the light emitting diode string requested by the off-dimming control signal among the switching units connected to the light emitting diode string. LED array drive device. The method of claim 2,
A detection resistor connected between the switching unit and the base power source; And
A detection line connected to a node between the detection resistor and the switching unit and the light emitting diode array driving unit,
The LED array drive unit,
When the on-dimming control signal for turning on the light emitting diode string is received, the power supply unit detects a voltage value through the detection line and applies a predetermined constant voltage to the light emitting diode strings according to the detected voltage value. Light emitting diode array driving apparatus, characterized in that for controlling. Applying an array driving voltage to the plurality of light emitting diode strings constituting the light emitting diode array;
When an off-dimming control signal for turning off the light emitting diode string is received, a reference voltage for causing an off current to flow through the light emitting diode string while the light emitting diode string does not emit light is connected to the light emitting diode string. Applying to a switching unit connected between the base power sources; And
And when the on-dimming control signal for turning on the light emitting diode string is received, applying a steady voltage to the switching unit to cause the light emitting diode string to emit light. The method of claim 7, wherein
Applying the reference voltage,
Receiving an off dimming control signal to turn off at least one of the light emitting diode strings;
Generating the reference voltage; And
Applying the reference voltage to a gate or a base of a transistor constituting a switching unit connected to a light emitting diode string corresponding to the off-dimming control signal to allow the off current to flow through the light emitting diode string and the transistor. LED array drive method comprising a. The method of claim 7, wherein
The step of applying the steady voltage,
Receiving an on dimming control signal to turn on at least one of the light emitting diode strings;
Applying the steady voltage to a gate or a base of a transistor constituting a switching unit connected to a light emitting diode string corresponding to the on dimming control signal;
Detecting a current value from a detection line connected to a node between the switching unit and a base power source; And
And applying a voltage for allowing the steady current to flow through the light emitting diode string and the switching unit when the current value is different from a preset current value. The method of claim 7, wherein
The step of applying the steady voltage,
Receiving an on dimming control signal to turn on at least one of the light emitting diode strings;
Applying the steady voltage to a gate or a base of a transistor constituting a switching unit connected to a light emitting diode string corresponding to the on dimming control signal;
Detecting a voltage value from a detection line connected to a node between the switching unit and a base power source;
And controlling the power supply unit to apply a predetermined voltage to the light emitting diode string when the voltage value is different from a predetermined voltage value. A panel including a plurality of liquid crystal cells formed for each region defined by the intersection of the plurality of gate lines and the plurality of data lines;
A panel driver for driving the data line and the gate line to display an image corresponding to input data from the outside on the panel; And
It includes a backlight unit for irradiating light to the panel,
The backlight unit includes a light emitting diode array driving device according to any one of claims 1 to 6. A liquid crystal display device using a light emitting diode array driving device.

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