JP2007109691A - Led backlight device and image display device provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent conspicuousness of variation in luminance of a display screen of a liquid crystal panel to be illuminated with an LED backlight when a current value for driving LEDs varies. <P>SOLUTION: LEDs 11 arranged in matrix are formed by LED units connected in parallel while a plurality of LEDs are combined into one unit. Current control units 22 are each connected to each of the LED units, and supplies current to the LED unit to which itself is connected using power supplied from a power source circuit 21 to light each of the LEDs 11 on. The backlight device is configured so that an arrangement pattern of LEDs 11 of one unit to be connected in parallel to one of the current control units 22 has a Z-shape. With this configuration, if the current value of a plurality of arranged current control units varies or fluctuates, a change in light-emitting luminance corresponding to the current variation is generated not in linearity but in saw-tooth shape, and the variation in luminance on a screen can be made inconspicuous. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an LED backlight device and an image display device including the device, and more specifically, an LED backlight using an LED as an element for illuminating a light modulation element such as a liquid crystal panel, and the LED backlight. The present invention relates to an image display device that displays an image by using it.

  An LED backlight has attracted attention as a backlight for illuminating a light modulation element such as a liquid crystal panel from the back. The LED backlight has a configuration in which white LEDs are arranged to emit white illumination light, and LEDs of three colors of R (red), G (green), and B (blue) are arranged. There is a configuration in which light of three colors is mixed into white light. In addition, the white LED has a method of obtaining a white color by combining a phosphor with a short wavelength LED, a method of obtaining a white color by combining a phosphor with a blue LED, or a white color by combining a blue phosphor with a yellow phosphor. There are things to get.

Such a backlight using an LED has several characteristic advantages over a backlight using a fluorescent tube such as a conventional cold cathode tube (CCFL).
For example, a fluorescent tube that has been conventionally used as a backlight has a problem that a high voltage is required when it is turned on, and that the life of the fluorescent tube is shortened if the fluorescent tube is repeatedly turned on and off. In addition, since the fluorescent tube is usually formed of a glass material, there is a problem that the degree of freedom in shape is limited as a backlight light source.

In contrast, backlights using LEDs can be driven at a lower voltage than fluorescent tubes, and have superior performance such as low power consumption and long life.
In addition, the backlight using three-color LEDs is characterized in that white light is obtained from wavelengths close to the three primary colors of light, so that the degree of color freedom is increased compared to conventional cold cathode tubes. In particular, the color reproducibility can be greatly expanded so that the color reproducibility exceeding 100% compared to the NTSC standard can be realized and the white point (white color) can be freely adjusted. Become.

  As an LED backlight, for example, there is a light guide plate type in which a light guide plate is disposed on the back side of a liquid crystal panel and a plurality of LEDs are arranged in an array at the end of the light guide plate. In this case, the illumination light emitted from the LED array illuminates the liquid crystal panel via the light guide plate. Further, between the light guide plate and the liquid crystal panel, optical sheets such as a diffusion plate and a prism sheet are appropriately disposed in order to give the illumination light a light distribution characteristic and a luminance distribution characteristic.

  In contrast to the light guide plate system as described above, a direct type LED backlight in which LEDs are arranged directly under the back side of a liquid crystal panel is provided. Also in the direct type LED backlight, the optical sheets as described above are appropriately disposed between the LED and the liquid crystal panel.

The direct type LED backlight as described above has advantages such as higher light utilization efficiency and lighter weight than the light guide plate method. Regarding the light utilization efficiency, the light utilization efficiency of a light guide plate type LED backlight is about 50%, for example, whereas the light utilization efficiency of a direct type LED backlight is as high as about 75%. .
In general, a display device using a liquid crystal panel is required to have a high level of screen brightness. For example, in a liquid crystal television device, the luminance level of the screen is required to be at least 450 cd / m ^{2. In} order to satisfy such a requirement, a direct type LED backlight having a high light utilization efficiency is basically used. It can be said that it is advantageous.

Regarding the configuration of the LED backlight as described above, for example, Patent Document 1 discloses an efficient LED backlight device that suppresses voltage loss and current loss and has low power loss. Here, the LED drive means which has the timing control means which controls the switch means connected in parallel with each LED which comprises LED backlight, or the switch means connected in series with each LED is provided. By this LED driving means, the LED can be switched and blinked at a constant timing, thereby suppressing voltage loss and current loss due to the LED to a minimum.
JP 2002-37395 A

  FIG. 4 schematically shows a connection configuration example of the power supply circuit and the LED when the above-described direct type LED backlight is configured, in which 11 is the LED, 21 is the power supply circuit, and 22 is the current. It is a control unit. As shown in FIG. 4, in order to light the LEDs 11 constituting the backlight, a plurality of LEDs 11 are connected in parallel as a set of units, and a current control unit 22 applies a constant current to each unit. Connect. Each current control unit 22 is supplied with power from the power supply circuit 21.

  When a plurality of LEDs 11 are combined as described above and a constant current is supplied by each current control unit 22, due to variations in characteristics of the current control unit 22, for example, a specific current control unit If the current value supplied from the current control unit 22 fluctuates or the current values output from the plurality of current control units 22 differ from each other, the light emission of the set of LEDs 11 connected to the specific current control unit 22 The brightness will change.

  In this case, since the plurality of LEDs 11 arranged in a straight line are connected in parallel to the current control unit 22 as described above, for example, the output current value of one current control unit 22 is the other current control unit 22. When the current value is different from the current value, luminance unevenness occurs in a straight line. And on the display screen of the liquid crystal panel illuminated by the LED backlight, the luminance unevenness of the LED backlight is visually recognized, and the deterioration of the image quality becomes conspicuous. In particular, when uneven brightness occurs in a straight line, there is a problem that the unevenness is noticeable to human eyes.

  Although the above-mentioned Patent Document 1 discloses the idea of reducing power consumption by suppressing power loss due to the LED backlight, as described above, it copes with image quality degradation due to variations in current values for driving the LEDs to emit light. The idea for doing this is not disclosed.

  The present invention has been made in view of the above circumstances, and in an LED backlight device in which a plurality of LED units in which a plurality of LEDs are connected in parallel are arranged, power is supplied to each LED unit. An LED backlight that always enables high-quality screen display by making the brightness unevenness of the display screen of the liquid crystal panel illuminated by the LED backlight inconspicuous when the current value that drives the LED varies An object is to provide a light device and an image display device having the LED backlight device.

  In order to solve the above-mentioned problem, the first technical means is an LED backlight device in which an object to be illuminated is illuminated from the back by light emitted from the LED. The LED backlight device includes a plurality of LEDs arranged in parallel. An LED backlight unit having a plurality of LED units connected to the LED unit, and a current control unit that is provided for each LED unit and supplies a constant current to the LED unit. The LEDs are arranged such that a straight line connecting the constituent LEDs has at least a refracting portion.

  According to a second technical means, in the first technical means, the LED backlight unit includes LEDs arranged in a matrix in the vertical and horizontal directions, and at least LEDs adjacent in either the vertical and horizontal directions are arranged in parallel in one LED unit. It is characterized by not being connected.

  According to a third technical means, in the first technical means or the second technical means, the LED backlight unit includes a plurality of LEDs arranged in a matrix in the row direction and the column direction, and the LED unit is included in the LED unit. The arrangement of the plurality of LEDs in the row direction is configured to be arranged in a Z-shape while moving alternately in the column direction.

  A fourth technical means includes the LED backlight device according to any one of the first to third technical means and a liquid crystal panel illuminated by the LED backlight device, and the illumination light from the LED backlight is emitted from the liquid crystal panel. The image display is performed by modulation.

  According to the present invention, in an LED backlight device in which a plurality of LED units in which a plurality of LEDs are connected in parallel are arranged, the current value for driving the LEDs varies when power is supplied to each LED unit. In addition, by making the luminance unevenness of the display screen of the liquid crystal panel illuminated by the LED backlight inconspicuous, an LED backlight device that always enables high-quality screen display, and an image having the LED backlight device A display device can be provided.

  In particular, the LED backlight device of the present invention is arranged so that a straight line connecting LEDs connected in parallel has at least a refracted portion. For example, by configuring a so-called staggered wiring structure so that LEDs connected in parallel have a Z-shape, even when variations in the current value for driving the LEDs occur, uneven brightness occurs in a refracted shape. , Can be less noticeable to human eyes. As a result, the display screen of the liquid crystal panel illuminated by the LED backlight can maintain the image quality of the display image without conspicuous luminance unevenness even when the current value fluctuation of the current control unit of the LED backlight occurs. It becomes like this.

FIG. 1 is a diagram for explaining a configuration example of a direct type LED backlight, in which 10 is an LED backlight device, 11 is an LED, 12 is a diffusion plate, 13 is another optical sheet, and 14 is a reflection. A plate, 15 is a housing of the LED backlight device, and 16 is a liquid crystal panel.
In the example shown in FIG. 1, a reflector 14 is disposed on the bottom surface side of the casing 15 of the backlight unit, and a plurality of LEDs 11 are disposed in a matrix on the top surface side. The matrix LED 11 can be configured by arranging a plurality of units in which a plurality of LEDs 11 are arranged in an array on a substrate. Further, a through hole may be formed in the reflecting plate 14, and the individual LEDs 11 may be disposed in the through hole. Alternatively, a reflecting surface may be formed on the surface of the substrate on which the LEDs 11 are arranged by printing or the like, and the function of the reflecting plate 14 may be imparted to the LED substrate.

In the present invention, the configuration of these LEDs 11 is not limited at all, and it is sufficient that a plurality of LEDs 11 are provided on the back side of the liquid crystal panel 16. Further, the LED backlight device of the present embodiment may be an illumination method using white LEDs as described above, or may be an illumination method in which three colors of RGB LEDs are arranged, and is particularly used. The LED is not limited.
Various electric circuit parts (not shown) including an LED lighting circuit, a dimming control unit, an LED lighting circuit, and the like for controlling the lighting of the LEDs are arranged together on the back surface of the backlight unit. Is not limited.

The light emitted from the LED 11 is diffused by the diffusion plate 12 and further receives a predetermined action by another optical sheet 13 to illuminate the liquid crystal panel 16 from the back side. As the other optical sheets 13, for example, an optical sheet such as a prism sheet is appropriately used.
The liquid crystal panel 16 modulates the illumination light emitted from the LED 11 by controlling the orientation of the liquid crystal of each pixel according to the input video signal. As a result, an image corresponding to the image signal is displayed on the liquid crystal panel 16.

  In the present invention, the array of the plurality of LEDs 11 is not limited to the configuration in which the LEDs 11 are arranged in a matrix in the vertical and horizontal directions as described above. For example, the array pitch of the LEDs in the vertical and horizontal rows is alternately shifted. However, the arrangement form is not limited.

  FIG. 2 is a diagram for explaining a configuration example of a wiring pattern of the LED backlight device. In the LED backlight device of this example, a plurality of LEDs 11 are arranged in a matrix to form a light source unit. And LED11 arrange | positioned at matrix form is comprised by the unit (LED unit) which connected several LED11 as a set in parallel.

  Each LED unit is connected to a current control unit 22, and the power supplied from the power supply circuit 21 supplies current to the LED unit to which the LED unit is connected, thereby lighting each LED 11.

  In the LED backlight device of the embodiment shown in FIG. 2, the arrangement pattern of one unit of the LEDs 11 connected in parallel to one of the current control units 22 is configured to have a z-shaped Z shape. That is, the light source unit of the LED backlight is configured such that a plurality of LEDs 11 are arranged in a matrix in the row direction and the column direction, and the above LED unit has an array in the row direction of the plurality of LEDs 11 included in the LED unit. It is configured to be arranged in a Z shape while moving alternately in the column direction.

With such a configuration, when the current values of the plurality of current control units arranged vary or fluctuate, a change in light emission luminance corresponding to the current variation occurs in a sawtooth shape instead of a linear shape.
As described above, when LEDs connected in parallel are arranged on a straight line, when the light emission luminance of the LED changes due to variations in the current value, luminance unevenness occurs in a straight line. Will become noticeable.

  On the other hand, in the LED backlight of this embodiment, since the LEDs connected in parallel as described above have a zigzag Z-shape and are arranged in a staggered manner, variations in current values occurred. Even in this case, the luminance unevenness is generated in the Z-shape, and can be made inconspicuous by human eyes. Thereby, the display screen of the liquid crystal panel illuminated by the LED backlight can maintain the image quality of the display image without conspicuous luminance unevenness even if the current value fluctuation of the current control unit of the LED backlight occurs. become.

That is, in order to obtain the above effects, it is obvious that the LED wiring pattern in the LED backlight device is not limited to the example of FIG.
According to the present invention, when the LED 11 constituting the LED unit is connected in parallel, the LED backlight device is arranged such that a straight line connecting the LED 11 constituting the LED unit has at least a refracting portion. Configure. As a result, it is possible to prevent the LED 11 constituting the LED unit from being linear as much as possible and to make the luminance unevenness inconspicuous.

  Further, at this time, when a plurality of LEDs 11 are arranged in a matrix form in the vertical and horizontal directions as shown in FIG. 1, at least the LEDs 11 adjacent in either the vertical or horizontal direction are not connected in parallel in one LED unit. . When the LEDs 11 adjacent to each other in any one of the vertical and horizontal directions are connected in parallel in one LED unit, a linear array of the LEDs 11 is formed in that portion, and the luminance unevenness becomes conspicuous in that portion.

  At this time, it is preferable that the LEDs connected in parallel to one LED unit vary as widely as possible. By forming an LED unit using a wide range of LEDs 11 in this way, when the current value by the current control unit is different, the luminance unevenness on the screen can be made inconspicuous even when the current value fluctuates. Become.

  In addition, when forming wiring patterns connected in parallel using a wide range of LEDs as described above, if problems such as complicated manufacturing processes or reduced reliability occur due to wiring routing, etc. The wiring pattern is determined within the allowable range.

  FIG. 3 is a block diagram for explaining a configuration example of an image display device provided with the LED backlight device of the present invention, and shows an example of a liquid crystal television device configured as an image display device. In this example, it is assumed that the LED backlight device as described in the above embodiment is applied for illumination of a liquid crystal panel (LCD) included in the liquid crystal television device.

  In the liquid crystal television device 30, the tuner 32 selects a channel from the television broadcast signal received by the antenna 31. The video input terminal 33 inputs a video signal from an AV device that is built in or externally connected to the television apparatus 30. Then, the switching unit 34 switches and outputs the television broadcast signal selected by the tuner 32 and the video signal input via the video input terminal 33.

  The video signal output from the switching unit 34 is processed by the video processing unit 35 and output to the LCD control unit 36. The video processing unit 35 performs a video signal generation process and various image quality adjustment processes from the input video signal. The video processing unit 35 performs composite signal YC separation processing, RGB signal decoding processing for generating RGB signals from YC signals, AD conversion processing, color space conversion processing, IP conversion processing, scaling processing, FRC processing, color correction processing, synchronization Video signal processing such as detection processing, γ correction processing, and OSD display processing is appropriately executed.

  The LCD control unit 36 generates gradation data and a signal line control signal to be output to the source driver of the LCD 37 in accordance with the RGB image display signal output from the video processing unit 35, and also outputs the scanning line control signal to be output to the gate driver. Then, the image display control on the LCD 37 is performed. The LCD control unit 36 generates a backlight control signal to be output to the light source driving unit 38 and performs light emission driving control of the LED backlight 39.

  The light source drive unit 38 includes the current control unit 22, the abnormality detection unit 23a, and the control unit 25 shown in FIG. 2, and uses the power supplied from a power supply circuit to a liquid crystal television device (not shown) to The lighting drive control of the backlight 39 is executed.

In the television apparatus 30, the audio signal output from the switching unit 34 is processed by the audio processing unit 40 and output from the speaker 41 as audio.
The remote control light receiving unit 42 receives the infrared remote control operation signal transmitted from the remote control device 50 and sends it to the control unit 43. The control unit 43 detects and analyzes the remote control operation signal received by the remote control light receiving unit 42, and performs these operations on the tuner 32, the switching unit 34, the video processing unit 35, the LCD control unit 36, the audio processing unit 40, and the like. A control signal to be controlled is output. Here, programs and data stored in the memory 44 are used. Further, the operation input by the user to the liquid crystal television device can be executed not only by using the remote control device 50 but also by using operation keys and switches provided in the main body operation unit of the television device 30.

  The image display apparatus according to the present invention is not limited to the above-described liquid crystal television, and the present invention is applied to various image display apparatuses having a configuration in which a liquid crystal panel is illuminated from the back to generate a display image. Can be applied.

It is a figure for demonstrating the structural example of a direct type LED backlight. It is a figure for demonstrating the structural example of the power supply part of an LED backlight apparatus. It is a block diagram for demonstrating the structural example of the image display apparatus provided with the LED backlight of this invention. It is a figure for demonstrating the connection structural example of a power supply circuit and LED when comprising the conventional direct type | mold LED backlight.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... LED, 12 ... Diffusing plate, 13 ... Optical sheet, 14 ... Reflecting plate, 15 ... Housing | casing, 16 ... Liquid crystal panel, 21 ... Power supply circuit, 22 ... Current control part, 23a ... Abnormality detection part, 25 ... Control , 30 ... Television apparatus, 31 ... Antenna, 32 ... Tuner, 33 ... Video input terminal, 34 ... Switching unit, 35 ... Video processing unit, 36 ... LCD control unit, 37 ... LCD, 38 ... Light source drive unit, 39 DESCRIPTION OF SYMBOLS ... LED backlight, 40 ... Audio | voice processing part, 41 ... Speaker, 42 ... Remote control light-receiving part, 43 ... Control part, 44 ... Memory, 50 ... Remote control apparatus.

Claims (4)

An LED backlight device configured to illuminate an object to be illuminated from the back by light emitted from an LED. The LED backlight device includes an LED backlight having a plurality of LED units connected in parallel. A light unit and a current control unit that is provided for each LED unit and supplies a constant current to the LED unit;
The LED backlight device, wherein the LEDs are arranged so that a straight line connecting the LEDs constituting the LED units connected in parallel has at least a refracting portion.   2. The LED backlight device according to claim 1, wherein the LED backlight unit includes LEDs arranged in a matrix in the vertical and horizontal directions, and at least adjacent LEDs in either the vertical and horizontal directions are arranged in parallel in one LED unit. An LED backlight device that is not connected.   3. The LED backlight device according to claim 1, wherein the LED backlight unit includes a plurality of LEDs arranged in a matrix in a row direction and a column direction, and the LED unit is included in the LED unit. An LED backlight device comprising: a plurality of LEDs arranged in a Z shape while being alternately arranged in a column direction.   An LED backlight device according to any one of claims 1 to 3 and a liquid crystal panel illuminated by the LED backlight device, wherein the liquid crystal panel modulates illumination light from the LED backlight to generate an image. An image display device that performs display.

Images