JP2013222515A - Led lighting device and display device - Google Patents

Abstract

When controlling the light emission luminance of an LED for each region composed of a plurality of LEDs, the load is distributed among a plurality of driver circuits that drive the LEDs, and the temperature of ICs and semiconductor elements included in the driver circuits is increased. Suppress.
An LED lighting device is mounted on a display device having a local dimming function that divides a backlight into a plurality of regions and controls light emission of the LEDs for each region in accordance with a video signal of the divided region. The LED lighting device includes a plurality of LED units 71 and 72 including a plurality of LED elements, and a plurality of driver circuits 62 and 63 that drive the LED units 71 and 72. The LED units 71 and 72 each display a display device. The adjacent LED elements in the LED unit corresponding to the predetermined area of the panel and corresponding to the predetermined area are connected to and driven by different driver circuits.
[Selection] Figure 3

Description

  The present invention relates to an LED lighting device and a display device, and more specifically, an LED lighting device for lighting an LED (Light Emitting Diode) used for a backlight light source of the display device and a display including the LED lighting device. Relates to the device.

  In recent years, liquid crystal display devices using LEDs (Light Emitting Diodes) as backlight light sources have been released by various manufacturers. This LED is a semiconductor element that emits light when a voltage is applied in the forward direction. When a positive voltage is applied to the anode and a negative voltage is applied to the cathode, a current flows at a voltage of several volts and emits light. When this LED is used as a backlight light source, there is an advantage that local dimming is possible. Local dimming is a technique in which the backlight is divided into a plurality of areas, and the light emission of the LEDs is controlled for each area in accordance with the video signal of each area. For example, it is possible to control such that a dark portion in the screen suppresses light emission of the LED, and a bright portion in the screen causes the LED to emit light strongly. Thereby, the power consumption of the backlight can be reduced and the contrast of the display screen can be improved.

  It is generally known that the above-mentioned LEDs are vulnerable to heat, and unless appropriate heat dissipation measures are taken, the light emission efficiency and the life may be reduced. For example, Patent Document 1 discloses a technique for improving heat dissipation efficiency by utilizing the fact that a drive voltage is reduced when lighting / extinguishing is controlled for each region (block) composed of a plurality of LEDs. ing. According to the technique described in Patent Document 1, the heat dissipation efficiency is improved by bringing the LED drive board into close contact with the chassis. In addition, in the LED driving unit for driving the LED, on / off switching is performed at high speed by a semiconductor element such as an FET (Field Effect Transistor). When the LED driving unit is overloaded, the LED driving unit is configured. There is a possibility that the semiconductor element to cause thermal destruction. For this reason, it is important to perform an appropriate thermal design for the semiconductor elements in the LED drive unit.

JP 2010-176968 A

  FIG. 5 is a diagram showing a configuration of a conventional LED lighting device. The LED lighting device is roughly divided into an LED driving unit 101 that drives an LED and an LED backlight 105 that includes a plurality of LEDs. The LED driving unit 101 includes a microcomputer 102, a first driver circuit 103, and a second driver circuit 104, and the LED backlight 105 includes a first LED unit 106 and a second LED unit 107. The first driver circuit 103 includes a first LED driver 103a that drives each LED of the first LED unit 106 of the LED backlight 105, and a first converter circuit 103b that includes a first switching power supply 103c. .

  Similarly, the second driver circuit 104 includes a second LED driver 104a that drives each LED of the second LED unit 107 of the LED backlight 105, and a second converter circuit 104b that includes a second switching power supply 104c. With. The first LED driver 103a and the second LED driver 104a are mounted as an IC (Integrated Circuit) chip, for example. The first switching power supply 103c and the second switching power supply 104c are mounted as semiconductor elements such as FETs, for example.

  FIG. 6 is a diagram for explaining a connection relationship between the LED backlight and the LED driving unit constituting the LED lighting device. In this example, the first LED unit 106 of the LED backlight 107 is arranged at the upper part of the screen of the display device, and the second LED unit 107 is arranged at the lower part of the screen of the display device. Each LED constituting the first LED unit 106 is connected to the first LED driver 103a, and each LED constituting the second LED unit 107 is connected to the second LED driver 104a.

  Here, as a method that further expands the above-mentioned local dimming, PWM (Pulse Width Modulation) control is performed so that the power does not exceed the specified value. When the lighting area is small, the power is supplied locally and the peak is reached. A technique for increasing luminance is known. By this method, it is possible to obtain a higher luminance than normal local dimming. However, for example, when a video signal as shown in FIG. 7 (the upper half is white and the lower half is black) is input, the first driver circuit 103 and the second driver circuit 104 shown in FIG. The load is concentrated only on the first driver circuit 103 that drives half of the LEDs. The concentration of the load may increase the temperature of the IC and the semiconductor element constituting the first driver circuit 103, which may cause a decrease in life, thermal destruction, and the like.

  On the other hand, the invention described in Patent Document 1 does not focus on suppressing the temperature rise of ICs and semiconductor elements constituting the driver circuit, and cannot solve such problems.

  The present invention has been made in view of the above circumstances, and when controlling the light emission luminance of each LED, the load is distributed among a plurality of driver circuits that drive the LEDs. An object of the present invention is to provide an LED lighting device capable of suppressing a temperature rise of an IC or a semiconductor element included in a driver circuit, and a display device including the LED lighting device.

  In order to solve the above problems, the first technical means of the present invention divides the backlight into a plurality of areas, and controls the light emission of the LED for each area according to the video signal of the divided area. An LED lighting device mounted on a display device including: a plurality of LED units including a plurality of LED elements; and a plurality of driver circuits for driving the LED units, each of the LED units being the display device. The adjacent LED elements in the LED unit corresponding to the predetermined area of the display panel and connected to the predetermined area are connected to and driven by different driver circuits.

  According to a second technical means, in the first technical means, the LED unit includes a plurality of LED lines in which a plurality of LED elements are arranged in a predetermined direction, and the plurality of LED lines have the predetermined direction. It is characterized by being arranged so as to be parallel to each other.

  According to a third technical means, in the second technical means, the plurality of LED lines are arranged in a matrix, and among the plurality of LED lines arranged in the matrix, there are LED lines in a staggered positional relationship. It is characterized by being driven by the same driver circuit.

  According to a fourth technical means, in any one of the first to third technical means, the driver circuit includes an LED driver configured as an IC chip and a switching power source configured as a semiconductor element. It is a feature.

  The fifth technical means is a display device equipped with the LED lighting device according to any one of the first to fourth technical means.

  According to the present invention, when controlling the light emission luminance of each LED region, the load can be distributed among a plurality of driver circuits that drive the LEDs. It is possible to prevent the load from being concentrated and to suppress the temperature rise of the IC and the semiconductor element included in the driver circuit.

It is a block diagram which shows the principal part structural example of the display apparatus provided with the LED lighting device by this invention. It is a figure explaining the setting method of the maximum light emission luminance of LED of LED backlight. It is a figure which shows the structural example of the LED lighting device by this invention. It is a figure for demonstrating an example of the connection relation of the LED backlight which comprises the LED lighting device by this invention, and an LED drive part. It is a figure which shows the structure of the conventional LED lighting device. It is a figure for demonstrating the connection relation of the LED backlight which comprises an LED lighting device, and an LED drive part. It is a figure which shows an example of an input video signal.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an LED lighting device of the present invention and a display device including the LED lighting device will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating an exemplary configuration of a main part of a display device including an LED lighting device according to the present invention. The display device 1 can be exemplified as a liquid crystal display device, for example, and includes an image processing unit 2, an area active control unit 3, a panel control unit 4, an LCD (Liquid Crystal Display) panel 5, an LED driving unit 6, and an LED. A backlight 7 is provided. The LED lighting device according to the present invention includes the LED driving unit 6 and the LED backlight 7.

  The image processing unit 2 receives a video / audio signal separated from a broadcast signal and a video / audio signal from an external device and performs video signal processing such as decoding the encoded video / audio signal. The image processing unit 2 appropriately executes, for example, IP conversion, noise reduction, scaling processing, γ adjustment, white balance adjustment, and the like on the input video signal.

  The area active control unit 3 divides the backlight into a plurality of areas, and executes a local dimming process for controlling the light emission of the LED for each area according to the video signal of the divided area. Specifically, the area active control unit 3 divides an image displayed by the video signal into predetermined regions according to the video signal input by the image processing unit 2, and sets the maximum gradation value of the video signal for each divided region. Extract.

  Then, the area active control unit 3 increases the light emission luminance of the LED backlight 7 in the region where the maximum gradation value is large, and decreases the light emission luminance of the LED in the region where the maximum gradation value is small. The emission luminance is controlled according to the extracted maximum gradation value.

  Note that here, the emission luminance of the LED is controlled using the maximum gradation value of each divided area, but the emission luminance of the LED is determined using other feature amounts such as the gradation average value of each divided area. It is good also as controlling.

  Further, the area active control unit 3 increases the brightness of the LED backlight 7 and improves the contrast while keeping the total value of the drive currents for turning on the LEDs of the LED backlight 7 below a predetermined allowable current value. Take control.

  Specifically, the area active control unit 3 calculates the lighting rate of the LED backlight 7 corresponding to each divided region based on the maximum gradation value of the video signal extracted for each divided region. The lighting rate is the ratio of the maximum gradation value of the video signal in each divided area to the gradation value that the video signal can take.

  For example, the gradation value that the video signal can take is 256 gradations, there are eight divided areas, and the maximum gradation value of the video signal in the eight divided areas is 64, 224, 160, 32, 128, 192, 192. , 96, the lighting rate of the LED backlight 7 corresponding to each divided area is 25.0%, 87.8%, 62.7%, 12.5%, 50.2%, 75.3, respectively. %, 75.3%, and 37.6%.

  Moreover, the area active control part 3 calculates an average lighting rate. In the example described above, the average lighting rate is 53.3%. Then, the area active control unit 3 sets the maximum light emission luminance of the LED of the LED backlight 7 using the average lighting rate.

  FIG. 2 is a diagram for explaining a method for setting the maximum light emission luminance of the LED of the LED backlight 7. The horizontal axis of FIG. 2 is the average lighting rate of the LED backlight 7. The average lighting rate is 0% when all the LEDs in each area of the LED backlight 7 corresponding to each divided area are turned off, and all the LEDs in each area of the LED backlight 7 corresponding to each divided area are turned on. Then, it becomes 100%. The vertical axis | shaft of FIG. 2 shows the maximum light emission luminance of LED of the LED backlight 7 in each average lighting rate.

  In the power limit control, it is assumed that the total value of the drive current for lighting each LED of the LED backlight 7 is constant. In the range where the average lighting rate is larger than P, the larger the average lighting rate, the smaller the current that can be supplied to one divided region, so the maximum light emission luminance becomes smaller.

  In a region where the average lighting rate is large, the image is felt dazzling, but this dazzling is suppressed by decreasing the maximum light emission luminance. Further, when the average lighting rate is near P, the maximum light emission luminance is the highest. When the maximum emission luminance is increased, the color reproducibility of a light source such as the sun or light is improved.

  In the range where the average lighting rate is smaller than P, it is possible to increase the maximum light emission luminance. However, since the image in this range is a dark image, reducing the maximum light emission luminance reduces the black expression. Realize, suppress black float, and maintain display quality.

  The area active control unit 3 determines the final luminance of each divided region using the relationship shown in FIG. 2, and outputs the determined luminance data to the LED driving unit 6. Specifically, the area active control unit 3 multiplies the luminance determined for each divided region according to the maximum gradation value by the local dimming process by the luminance increase rate, thereby obtaining the final luminance of each divided region. decide. Here, the luminance increase rate means a ratio a / b where the maximum emission luminance at a certain average lighting rate is a and the maximum emission luminance at 100% average lighting rate is b.

For example, assuming that the maximum light emission luminance is 800 cd / m ² when the average lighting rate is 64.0% and the maximum light emission luminance when the average lighting rate is 100% is 533 cd / m ² , the luminance increase rate a / b is 1.5.

  In this case, the area active control unit 3 determines the final luminance of each divided region by multiplying the luminance determined for each divided region according to the maximum gradation value by the local dimming process by 1.5. . It is assumed that the relationship between the maximum luminance and the average lighting rate shown in FIG. 2 is stored in advance in a storage unit (not shown) included in the display device 1.

  The area active control unit 3 outputs control data for controlling the LCD panel 5 to the panel control unit 4 for video display.

  In the above description, the luminance is controlled using the lighting rate of the LED backlight 7. However, the same control can be performed using the APL (Average Picture Level) of the video signal. . Since APL is an average value of the luminance of the entire video signal, the relationship between APL and the maximum luminance of the LED is considered to show the same tendency as that shown in FIG. That is, when the APL of the video signal is low, the lighting rate of the LED backlight 7 is low, and when the APL of the video signal is high, the lighting rate of the LED backlight 7 is high. Therefore, similar control can be performed even when the horizontal axis in FIG. 2 is APL.

  Here, when the above-described area active control is performed in the display device 1, for example, when a video signal as shown in FIG. 7 is input, the upper half LED unit among a plurality of driver circuits is driven. The load is concentrated only on one driver circuit. This concentration of loads may increase the temperature of ICs and semiconductor elements that constitute one driver circuit, possibly leading to a decrease in life and thermal destruction.

  The main object of the present invention is to distribute the load among a plurality of driver circuits that drive the LEDs when controlling the light emission luminance of the LEDs for each region composed of the plurality of LEDs, and to include ICs and semiconductors included in the driver circuits. It is to suppress the temperature rise of the element. As a configuration for this, the LED lighting device includes a plurality of LED units including a plurality of LED elements and a plurality of driver circuits for driving the LED units, each of the LED units being a predetermined unit of the LCD panel 5 of the display device 1. Adjacent LED elements in the LED unit arranged corresponding to the region and corresponding to the predetermined region are connected to and driven by different driver circuits. Hereinafter, a specific description will be given with reference to FIGS.

  FIG. 3 is a diagram showing a configuration example of the LED lighting device according to the present invention. The LED lighting device is roughly composed of an LED drive unit 6 that drives an LED and an LED backlight 7 that includes a plurality of LEDs. The LED drive unit 6 includes a microcomputer 61, a first driver circuit 62, and a second driver circuit 63, and the LED backlight 7 includes a first LED unit 71 and a second LED unit 72. The first driver circuit 62 includes a first LED driver 62a connected to the first LED unit 71 and the second LED unit 72, and a first converter circuit 62b including a first switching power supply 62c. .

  Similarly, the second driver circuit 63 includes a second LED driver 63a connected to the first LED unit 71 and the second LED unit 72, and a second converter circuit 63b including a second switching power supply 63c. With. The first LED driver 62a and the second LED driver 63a are mounted as an IC chip, for example. The first switching power supply 62c and the second switching power supply 63c are mounted as semiconductor elements such as FETs, for example.

  The first LED driver 62a receives a dimming control signal for controlling to a predetermined dimming duty ratio from the microcomputer 61. Then, the first LED driver 62a outputs a duty signal based on the dimming duty ratio to the first converter circuit 62b, and controls the operation / stop of the first switching power supply 62c to control the dimming duty ratio. A voltage V corresponding to is generated. For example, the first converter circuit 62b generates a voltage V for lighting the LED based on a reference voltage generated from a power supply voltage Vin such as a battery. The first converter circuit 62b is configured as a so-called step-up converter including the capacitor C, but may be any of a step-up type, a step-down type, and a step-up / step-down type. The basic configuration of the second driver circuit 63 is the same as that of the first driver circuit 62.

  In the example of FIG. 3, the first LED unit 71 is driven by the first driver circuit 62 and the second driver circuit 63, and similarly, the second LED unit 72 is driven by the first driver circuit 62 and the second driver circuit 62. It is driven by the driver circuit 63. That is, each of the LED units 71 and 72 is arranged corresponding to a predetermined area of the LCD panel 5 of the display device 1, and adjacent LED elements in the LED unit corresponding to the predetermined area are connected to different driver circuits. Driven.

  FIG. 4 is a diagram for explaining an example of a connection relationship between the LED backlight and the LED driving unit constituting the LED lighting device according to the present invention. In this example, the first LED unit 71 of the LED backlight 7 is arranged at the upper part of the screen of the display device 1, and the second LED unit 72 is arranged at the lower part of the screen of the display device 1. The first LED unit 71 includes a plurality of LED lines (1, 2, 3,...) Formed by arranging a plurality of LED elements in a predetermined direction, and the plurality of LED lines (1, 2, 3,...). ) Are arranged in a matrix so that the predetermined directions are parallel to each other. Adjacent LED lines are driven by different driver circuits. For example, in the adjacent LED lines 1 and 2, the LED line 1 is connected to the first LED driver 62a, and the LED line 2 is connected to the second LED driver 63a.

  Further, among the plurality of LED lines arranged in a matrix, LED lines having a zigzag positional relationship may be driven by the same driver circuit. In the example of FIG. 4, the LED lines 1, n + 2, 3 and the LED lines n + 1, 2, n + 3 are in a zigzag positional relationship, and the LED lines 1, n + 2, 3 are connected to the same first LED driver 62a. , LED lines n + 1, 2, n + 3 are connected to the same second LED driver 63a. That is, the LED lines 1, n + 2, 3 and the LED lines n + 1, 2, n + 3 are connected to different LED drivers.

  In addition, in the example of FIG. 4, although it has shown about the case where a some LED line is arrange | positioned in matrix form, it is not limited to this, For example, it is arranged so that a some LED line may be arranged in one direction. Also good.

  In the above configuration, for example, when a video signal as shown in FIG. 7 is input, the LED of the first LED unit 71 arranged at the upper part of the screen is driven. It is driven by one driver circuit 62 and second driver circuit 63. That is, since the load can be distributed among a plurality of driver circuits that drive the LEDs, the load is prevented from being concentrated on one driver circuit, and the temperature rise of the IC and semiconductor elements included in the driver circuit is suppressed. be able to.

  As described above, according to the present invention, when controlling the light emission of the LED for each region by the local dimming process, it is possible to prevent load concentration on one driver circuit regardless of what video signal is input. Therefore, the reliability of the apparatus can be improved with a simple and inexpensive configuration.

DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 2 ... Image processing part, 3 ... Area active control part, 4 ... Panel control part, 5 ... LCD panel, 6 ... LED drive part, 7 ... LED backlight, 61 ... Microcomputer, 62 ... 1st Driver circuit, 62a ... first LED driver, 62b ... first converter circuit, 62c ... first switching power supply, 63 ... second driver circuit, 63a ... second LED driver, 63b ... second converter circuit 63c, second switching power supply, 71, first LED unit, 72, second LED unit.

Claims (5)

An LED lighting device mounted on a display device having a local dimming function that divides a backlight into a plurality of regions and controls light emission of the LEDs for each region according to a video signal of the divided regions,
A plurality of LED units including a plurality of LED elements, and a plurality of driver circuits for driving the LED units;
Each of the LED units is disposed corresponding to a predetermined area of the display panel of the display device, and adjacent LED elements in the LED unit corresponding to the predetermined area are connected to and driven by different driver circuits. LED lighting device characterized by this.   The LED unit includes a plurality of LED lines in which a plurality of LED elements are arranged in a predetermined direction, and the plurality of LED lines are arranged so that the predetermined directions are parallel to each other. The LED lighting device according to claim 1.   The plurality of LED lines are arranged in a matrix, and among the plurality of LED lines arranged in the matrix, LED lines in a staggered relationship are driven by the same driver circuit. 2. The LED lighting device according to 2.   4. The LED lighting device according to claim 1, wherein the driver circuit includes an LED driver configured as an IC chip and a switching power source configured as a semiconductor element. 5.   The display apparatus carrying the LED lighting device of any one of Claims 1-4.

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