JP2007165161A - Led illumination device, led backlight device, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lessen reduction in brightness caused by an open failure of an LED or the like by lighting other LEDs except faulty LEDs by being equipped with a means to bypass current in parallel with the LEDs connected in series. <P>SOLUTION: The LED illumination device is provided with LED units formed by connecting a plurality of LEDs (D1 to D6) in series. These LED units are provided with Zener diodes (ZD1 to ZD6) for bypassing the current when one or more LEDs go in failure, and connect the Zener diodes (ZD1 to ZD6) in parallel for respective LEDs (D1 to D6). For example, when the forward direction voltage of the LEDs (D1 to D6) is made to be 1.2 V, and the reverse direction voltage of the Zener diodes (ZD1 to ZD6) is made to be 1.5 V, for example, if a D3 goes in failure, a terminal voltage of a ZD3 connected in parallel with the D3 becomes to have a constant voltage of 1.5 V, and similar voltages are applied to the other LEDs (D1, D2, and D4 to D6) except the D3 to become emittable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an LED illumination device, an LED backlight device, and an image display device. More specifically, the LED illumination device uses an LED (light emitting diode) as an element for illuminating a light modulation element such as a liquid crystal panel, and the LED illumination. The present invention relates to an LED backlight device using the device and an image display device that displays an image using the LED backlight device.

  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 R (red), G (green), and B (blue) LEDs are arranged. There is a configuration in which three colors of light are mixed to form white light. Here, for white LEDs, a method of obtaining white by combining RGB phosphors with a short wavelength LED chip, a method of obtaining white by combining yellow phosphors with a blue LED chip, or LED chips of three colors of RGB For example, a method of obtaining white as mixed light, a method of obtaining white as mixed light of two-color LED chips which are complementary colors, and the like can be employed.

  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 for lighting, and that the life of the fluorescent tube is shortened if lighting and extinguishing of the fluorescent tube are repeated in a complicated manner. . In addition, since the fluorescent tube is usually formed of a glass material, there is a problem that the degree of freedom of 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, a 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.

  LED backlights include, for example, a light guide plate type (edge light 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. In addition, optical sheets such as a diffusion plate and a prism sheet are appropriately disposed between the light guide plate and the liquid crystal panel in order to give the illumination light with light distribution characteristics and luminance dispersion characteristics.

  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 also 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 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, while the light utilization efficiency of a direct type LED backlight is as high as about 75%, for example. Become.

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, it can be said that a direct type LED backlight having a high light utilization efficiency is basically advantageous.

  The LED backlight is not limited to the edge light type and the direct type, and a configuration in which LEDs connected in series are connected in parallel is adopted. In such a form, the device has been devised such that the luminance of each LED series unit formed by connecting LEDs in series is made constant and the luminance is kept uniform.

  12 and 13 are schematic views showing a circuit configuration of a conventional direct type LED backlight device. The LED backlight device 100 illustrated in FIG. 12 includes LED series units 101 a to 101 d in which a plurality of LEDs (here, three LEDs) are connected in series and connected to a power source 103 in parallel. And the power supply control part 102a-102d which adds a constant current to each LED series unit 101a-101d is connected in series, respectively, and the electric current value for every unit is made constant.

  In addition, the LED backlight device 110 illustrated in FIG. 13 includes LED series units 111 a to 111 d in which a plurality of LEDs (here, three LEDs) are connected in series and connected in parallel to the power supply 113. And the electric current value is simply made constant by connecting resistance Ra-Rd to each LED series unit 111a-111d in series, respectively.

  However, in a system in which a plurality of LEDs are connected in series with a liquid crystal display using an LED backlight and one of the plurality of LEDs is damaged and becomes electrically open, the LEDs are connected in series. There was a problem that all the plurality of LEDs would be extinguished.

Regarding a conventional LED connection method, for example, Patent Document 1 describes a technique for absorbing a difference in Vf by connecting a resistor in series with an LED. Patent Document 2 describes a technique for reducing the influence of a decrease in luminance at the time of an open failure by arranging a Zener diode in an LED connected on a matrix.
JP 2004-90858 A JP 2004-356000 A

  However, the invention described in Patent Document 1 applies an LED to a stop lamp, and since a resistor is connected in series with the LED, the voltage drop caused by the resistor is integrated in proportion to the number of resistors. Thus, the voltage difference between the power supply side terminal and the GND terminal becomes large. When such a connection method is used for a backlight of a display device, there is a problem that a luminance change due to a voltage difference between terminals increases, and in particular, a luminance change increases as the number of LEDs increases.

  In the invention described in Patent Document 2, a plurality of LEDs are connected in a matrix, and Zener diodes are connected in parallel to LED groups connected in parallel to each column of the LED drive circuit block. Nothing is described about LEDs connected in series.

  The present invention has been made in view of the circumstances as described above, and by providing means for bypassing current in parallel to LEDs connected in series, other LEDs other than the failed LED are turned on. Provided are an LED illumination device that reduces a decrease in luminance due to an open failure of the LED, an LED backlight device using the LED illumination device, and an image display device that displays an image using the LED backlight device ,With the goal.

  In order to solve the above-mentioned problem, a first technical means of the present invention is an LED lighting device including an LED unit formed by connecting a plurality of LEDs in series, wherein one or more LEDs fail in the LED unit. In this case, a bypass means for bypassing the current is provided, and the bypass means is connected in parallel for each LED.

  A second technical means is an LED lighting device comprising an LED unit formed by connecting a plurality of LEDs in series, wherein the LED unit bypasses current when one or more LEDs fail. The bypass means is connected in parallel for each block composed of a plurality of LEDs.

  A third technical means is characterized in that, in the first or second technical means, the bypass means causes a current to flow when a voltage higher than a voltage for causing the LED to emit light is applied.

  According to a fourth technical means, in any one of the first to third technical means, the LED unit has the plurality of LEDs arranged in a staggered manner.

  According to a fifth technical means, in any one of the first to fourth technical means, the bypass means is constituted by a Zener diode.

  A sixth technical means is any one of the first to fourth technical means, wherein the bypass means is formed of a diode.

  A seventh technical means is any one of the first to fourth technical means, characterized in that the bypass means comprises a transistor circuit.

  The eighth technical means is any one of the first to fourth technical means, wherein the bypass means is composed of another LED.

  A ninth technical means is the eighth technical means, wherein the LED unit is composed of a plurality of LED blocks formed by connecting two LEDs in series and two in parallel. .

  A tenth technical means is the eighth technical means, wherein the LED unit is composed of a plurality of LED blocks formed by connecting two LEDs in parallel.

  An eleventh technical means is any one of the first to eighth technical means, wherein the LED unit comprises the LED and the bypass means as one component. .

  A twelfth technical means is an LED lighting device comprising an LED unit formed by connecting a plurality of LEDs in series, wherein the LED unit bypasses current when one or more LEDs fail. And a voltage detection means for detecting the voltage of the bypass means, wherein the bypass means and the voltage detection means are connected in parallel for each LED.

  A thirteenth technical means is the twelfth technical means characterized in that the plurality of voltage detecting means are connected to each other via a current backflow prevention circuit and grounded via the voltage detecting circuit. is there.

  A fourteenth technical means is the method according to the thirteenth technical means, wherein the current backflow prevention circuit is a diode.

  According to a fifteenth technical means, in the thirteenth or fourteenth technical means, the voltage detection circuit comprises a voltage detection resistor and a voltage measuring device.

  The sixteenth technical means is any one of the twelfth to fifteenth technical means, wherein the bypass means comprises a Zener diode and a diode.

  A seventeenth technical means includes the LED lighting device according to any one of the first to sixteenth technical means, and an LED backlight device that illuminates an object to be illuminated from the back surface with light emitted from the LED lighting device. It is what.

  The eighteenth technical means is characterized by an image display device comprising the LED backlight device according to the seventeenth technical means and a liquid crystal panel illuminated by the LED backlight device.

  According to the present invention, in an LED lighting device using an LED as a light source, it is possible to light other LEDs other than the failed LED by providing means for bypassing the current in parallel with the LEDs connected in series. Therefore, it is possible to reduce a decrease in luminance due to an open failure of the LED.

  The LED lighting device of the present invention includes a bypass unit for bypassing a current when one or more LEDs fail in an LED unit formed by connecting a plurality of LEDs in series. This bypass means, for example, arranges a Zener diode in parallel with one LED, arranges a Zener diode in parallel with a block composed of a plurality of LEDs, and arranges a plurality of LEDs in parallel with one or more LEDs. It is realized by a circuit configuration such as arranging a diode or a transistor circuit, or arranging another LED in parallel with one or more LEDs, thereby lighting other LEDs other than the failed LED, The main purpose is to reduce the influence of a decrease in luminance at the time of LED open failure.

  FIG. 1 is a diagram for explaining a configuration example of a direct type LED backlight device to which an LED lighting device according to the present invention is applied, FIG. 1 (A) is a sectional view, and FIG. 1 (B) is a plan view. is there. In the figure, 10 is an LED illumination device (hereinafter referred to as an LED backlight device), 11 is an LED, 12 is a diffuser plate, 13 is another optical sheet, 14 is a reflector, 15 is a housing of the LED backlight device, 16 Is a liquid crystal panel.

  In the example shown in FIG. 1, the reflector 14 is disposed on the bottom surface side of the housing 15 of the LED backlight device 10, and the plurality of LEDs 11 are disposed on the top surface side thereof. The LED unit composed of the plurality of LEDs 11 is provided with bypass means for bypassing current with respect to the LEDs connected in series in the event of an open failure of the LEDs. In this bypass means, for example, as shown in each embodiment of FIGS. 3 to 10 to be described later, a Zener diode is arranged in parallel to one LED, and a Zener diode is arranged in parallel to a plurality of LEDs. This is realized by a circuit configuration in which a plurality of diodes or transistor circuits are arranged in parallel with one or more LEDs, or another LED is arranged in parallel with one or more LEDs.

  The reflecting plate 14 may be formed with a through hole and the individual LEDs 11 are 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.

  Further, the LED backlight device 10 according to the present invention may be an illumination method using white LEDs as the LEDs 11, or may be an illumination method in which three RGB LEDs are arranged. The LED to be used is not limited.

  Light emitted from the plurality of LEDs 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.

  2 is a block diagram showing a circuit configuration example of the LED backlight device 10 shown in FIG. 1, in which 11a to 11n are LED units formed by connecting a plurality of LEDs 11 in series, 20 is a power circuit, and 21a. 21n represents a current control unit. The power supply circuit 20 supplies power to the current control units 21a to 21n, and the current control units 21a to 21n add constant currents to the LED units 11a to 11n, respectively. In addition, each electric circuit component (not shown) such as an LED lighting circuit for controlling lighting of the plurality of LEDs 11 and a dimming control unit is usually arranged collectively on the back surface of the LED backlight device 10, and the details thereof are particularly detailed. The positional relationship is not limited.

  Each of the LED units 11a to 11n includes a bypass unit that bypasses a current when the LED 11 connected in series is in the event of an open failure of one or more LEDs. This bypass means is configured by connecting a zener diode, a diode, a transistor circuit, or another LED in parallel to one or more LEDs 11. Hereinafter, a connection configuration example of the LED and the bypass unit in the LED unit will be described with reference to FIGS. 3 to 10.

  FIG. 3 is a diagram schematically showing an LED connection configuration example in the LED unit of the LED backlight device 10 according to the embodiment of the present invention, in which D1 to D6 are LEDs, and ZD1 to ZD6 are Zener diodes. Show. FIG. 3A shows a current flow in a normal state, and FIG. 3B shows a current flow when an open failure occurs. In addition, the arrow in a figure shows the direction of an electric current and LED (D3) to which "x" mark was given shows a failed LED.

  In this embodiment, for each LED (D1 to D6), one Zener diode (ZD1 to ZD6) is provided with a reverse polarity, and when an individual LED has an open failure, the Zener diode is bypassed. ing. For example, when the forward voltage of the LEDs (D1 to D6) is 1.2 V and the reverse voltage of the Zener diodes (ZD1 to ZD6) is 1.5 V, as shown in FIG. If D6) does not cause an open failure, the terminal voltage of the LEDs (D1 to D6) is 1.2 V, and therefore each Zener diode (ZD1 to ZD6) connected in parallel to each LED (D1 to D6). There is no current flowing through.

  Here, as shown in FIG. 3B, when at least one of the LEDs (D1 to D6) (D3 in this example) has an open failure, a Zener diode (ZD3) connected in parallel to the LED (D3) ) Terminal voltage becomes a constant voltage of 1.5V, and other LEDs than the LED (D3) are applied with substantially the same voltage as normal, and can emit light. Therefore, when an LED has an open failure, only the failed LED is turned off and other LEDs can be turned on, so that it is possible to reduce the influence of lowering the brightness of the entire backlight.

  FIG. 4 is a diagram schematically showing an example of an LED connection configuration in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D11 to D13, D21 to D23 are LEDs, ZD1, ZD2 represents a Zener diode. FIG. 4A shows the current flow in a normal state, and FIG. 4B shows the current flow when an open failure occurs. The arrow in the figure indicates the direction of current, the LED (D13) to which the “x” mark is given indicates a failed LED, and the LEDs (D11, D12) connected in series to the LED (D13) are also turned off. .

  In this embodiment, one Zener diode (ZD1, ZD2) is applied with reverse polarity for each block composed of a plurality of LEDs (D11 to D13, D21 to D23), and an individual LED (for example, D13) has an open failure. In some cases, a zener diode is bypassed. Therefore, the LEDs (D11, D12) connected in series to the failed LED (D13) are extinguished, but current flows through the Zener diode (ZD1) and is bypassed, so that current flows through the LEDs (D21 to D23). Can be lit.

  As shown in FIG. 3 described above, when a Zener diode is connected to each LED, the number of parts is greatly increased, resulting in a high cost. Therefore, in this embodiment, by arranging one Zener diode for several LEDs (three in this example), it is possible to prevent an increase in the number of components while preventing the LEDs connected in series from being completely turned off. it can.

  FIG. 5 is a diagram schematically showing an example of an LED connection configuration in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D11 to D13, D21 to D23 are LEDs, ZD1, ZD2 represents a Zener diode. FIG. 5A shows a current flow in a normal state, and FIG. 5B shows a current flow when an open failure occurs. The arrow in the figure indicates the direction of current, the LED (D13) to which the “x” mark is given indicates a failed LED, and the LEDs (D11, D12) connected in series to the LED (D13) are also turned off. .

  In the present embodiment, as in FIG. 4 described above, one Zener diode (ZD1, ZD2) is provided with a reverse polarity for each of the plurality of LEDs (D11 to D13, D21 to D23), and individual LEDs (for example, D13) are provided. ) Is configured to be bypassed by a Zener diode when an open failure occurs. Therefore, the LEDs (D11, D12) connected in series to the failed LED (D13) are extinguished, but current flows through the Zener diode (ZD1) and is bypassed, so that current flows through the LEDs (D21 to D23). Can be lit.

  Furthermore, in this embodiment, the arrangement of the LEDs (D11 to D13, D21 to D23) is devised so that the influence of the unlit LEDs is not concentrated on one place, and the LEDs are arranged in a staggered manner. For this reason, even if the LEDs (D11 to D13) are turned off, the LEDs (D21 to D23) arranged in a staggered manner are turned on, and dark portions of the liquid crystal panel do not occur in stripes, resulting in uneven brightness. It can be less noticeable.

  In addition, in order to acquire an effect as mentioned above, it is clear that arrangement | positioning of each LED (and Zener diode) which comprises an LED unit is not limited to the example of FIG. Wiring routing is slightly complicated, but the LED and Zener diode may be wired in a zigzag pattern with two or more column widths. An LED unit may be configured by connecting LEDs and Zener diodes arranged in the unit at random in series and parallel.

  FIG. 6 is a diagram schematically showing an LED connection configuration example in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D1 to D6 are LEDs, d11 to d12, d21 to d22, d31 to d32, d41 to d42, d51 to d52, d61 to d62 denote diodes. FIG. 6A shows the current flow in a normal state, and FIG. 6B shows the current flow when an open failure occurs. In addition, the arrow in a figure shows the direction of an electric current and LED (D3) to which "x" mark was given shows a failed LED.

  In the present embodiment, one or more diodes are connected in parallel and used instead of a Zener diode for at least one LED. A general diode is less expensive than a Zener diode, and a Zener diode can be substituted by connecting a plurality of diodes in series.

  For example, assuming that the forward voltage of each LED (D1 to D6) is 1.2V, two diodes having forward voltage of 0.7V are connected in series (d11 to d12, d21 to d22, d31 to d32, d41 to d42, d51). ˜d52, d61 to d62) can be connected to the terminals of the respective LEDs (D1 to D6) to obtain the same effect as the configuration illustrated in FIG. 3 described above.

  Further, by generating the LED element and the diode as the same component in advance, the effects of the present invention can be obtained without increasing the number of components and the component arrangement area.

  FIG. 7 is a diagram schematically showing an example of an LED connection configuration in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D1 is an LED, T1 is a transistor, and R1 and R2 are Indicates resistance. In FIG. 7, only one block constituting the LED unit is shown.

  In the configuration of this embodiment, instead of the two diodes shown in FIG. 6, a transistor T1 and resistors R1 and R2 are connected in parallel to the LED (D1). For example, if the resistors R1: R2 are in a 1: 2 relationship and the Vbe voltage of the transistor T1 is 0.6V, the terminal voltage is 1.8V when the LED (D1) has an open failure. Thereby, the effect similar to the structure illustrated in above-mentioned FIG. 3, FIG. 6 can be acquired.

  FIG. 8 is a diagram schematically showing an example of an LED connection configuration in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D11 to D14, D21 to D24, D31 to D34, D41 to D44 denote LEDs. In addition, the arrow in a figure shows the direction of an electric current and LED (D21) to which "x" mark was given shows a failed LED.

  In the configuration of this embodiment, four LEDs (for example, D21 to D24) are one block, and two LEDs are connected in series and in two rows in parallel. For example, when the LED (D21) has an open failure, the LED (D22) connected in series does not flow current and goes off, but the LED (D23, D24) has twice as much current as normal. It will be lit and the same brightness as normal is maintained. Also, for example, when the LED (D21) is short-circuited, the LED (D23, D24) does not flow and the light is extinguished, but the series-connected LED (D22) has twice as much current as normal. The brightness is reduced to half that of the normal state.

  FIG. 9 is a diagram schematically showing an example of an LED connection configuration in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D11 to D14, D21 to D24, D31 to D34, D41 to D44 denote LEDs. In addition, the arrow in a figure shows the direction of an electric current and LED (D21) to which "x" mark was given shows a failed LED.

  In the configuration of this embodiment, four LEDs (for example, D21 to D24) are one block, and two LEDs are connected in parallel. For example, when the LED (D21) has an open failure, the LED (D22, D24) is turned on because a current flows, and the LED (D23) is turned on with a current twice as large as normal, The same brightness as normal is maintained. Further, for example, when the LED (D21) is short-circuited, the LED (D23) is turned off without current flowing, but the LED (D22, D24) is turned on because current flows, so that the normal time Is maintained.

  FIG. 10 is a diagram schematically showing an LED connection configuration example in an LED unit of an LED backlight device 10 according to another embodiment of the present invention, in which D1 to D3 are LEDs, and ZD1 to ZD3 are Zener diodes. , D11 to d12, d21 to d22, d31 to d32 are diodes, R1 is a voltage detection resistor, and V is a voltage measuring instrument. FIG. 10A shows a current flow in a normal state, and FIG. 10B shows a current flow when an open failure occurs. In addition, the arrow in a figure shows the direction of an electric current and LED (D2) to which "x" mark was given shows a failed LED.

  In each of the embodiments shown in FIGS. 3 to 5 described above, when a current is bypassed by a Zener diode when an open failure occurs in at least one LED, an almost same value continues to flow as the current value. The light device 10 cannot detect an open failure of the LED. Therefore, in this embodiment, a circuit for detecting an open failure of an individual LED is added.

  Specifically, each LED (D1 to D3) is connected to a voltage detection resistor R1 (hereinafter simply referred to as R1) via diodes (d12, d22, d32). The resistance value of the resistor R1 is set to a value that is sufficiently smaller than the current flowing through the LEDs (D1 to D3) so as not to affect the driving of the LEDs (D1 to D3). In addition, diodes (d11, d21, d31), which are current backflow prevention circuits that prevent backflow of current from the LEDs (D1 to D3), are arranged in each connection. An open failure of the LED is detected by looking at the voltage of the resistor R1. The resistor R1 and the voltage measuring device V constitute the voltage detection circuit of the present invention.

Hereinafter, an operation example of the open failure detection method in the present embodiment will be described.
In FIG. 10, normally, when there is no open failure of the LED, all current flows through the LED (D1 to D3) side and does not flow through the Zener diode (ZD1 to ZD3) side. Accordingly, since no current flows to the resistor R1, the voltage of the resistor R1 becomes 0V.

  Next, when one LED (D2 in this case) has an open failure, a current flows through the Zener diode (ZD2) corresponding to the LED (D2) having the open failure, and the current flows to the resistor R1 through the diode (d22). Even current flows. The voltage applied to the resistor R1 is substantially equal to the cathode voltage of the LED (D2) that has failed open. Therefore, the open failure of the LED (D2) can be detected by monitoring the voltage of the resistor R1.

  As described above, since the voltage applied to the resistor R1 is the cathode voltage value of the LED (D2) having an open failure, the LED (D2) having an open failure can be identified from the value. Therefore, by storing the voltage value in a non-volatile memory or the like and referring to the value at the time of repair, it is possible to identify the LED that has failed open without turning on the LED again, and increase the working efficiency when replacing the LED. be able to.

  Although the direct type LED backlight device has been described above as an example, the LED lighting device according to the present invention can also be applied to an edge light type LED backlight device. This edge light type LED backlight device is not shown, but the LED illumination device as described above and the light emitted from the LED illumination device are incident from the end face, and the illuminated object is illuminated from behind by the emitted light. A light guide plate. Further, in the edge light type, the arrangement of LEDs is only one or a few as compared with the direct type, and an LED illumination device having an LED substrate on which LEDs of such an arrangement are mounted may be provided.

  FIG. 11 is a block diagram showing a configuration example of a liquid crystal television set configured as an image display device of the present invention, in which 30 is a liquid crystal television set. In this example, it is assumed that the LED backlight device as described above 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 35 selects a channel from the television broadcast signal received by the antenna 34. The video input terminal 36 inputs a video signal from an AV device built in or externally connected to the liquid crystal television device 30. The switching unit 37 switches and outputs the television broadcast signal selected by the tuner 35 and the video signal input via the video input terminal 36.

  The video signal output from the switching unit 37 is processed by the video processing unit 40 and output to the LCD control unit 41. The video processing unit 40 performs video signal generation processing, various image quality adjustment processing, and the like from the input video signal. The video processing unit 40 performs YC separation processing of composite signals, 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 41 generates gradation data and a signal line control signal to be output to the source driver of the liquid crystal panel 16 in accordance with the RGB image display signal output from the video processing unit 40, and also outputs a scanning line control signal to the gate driver. And the image display control in the liquid crystal panel 16 is performed. The LCD control unit 41 generates a backlight control signal to be output to the light source driving unit 42 and performs light emission driving control of the LED backlight 43.

  Based on the backlight control signal obtained from the LCD control unit 41, the light source driving unit 42 sends a control signal to the control circuit such as the microcomputer described above. The control circuit drives the LED backlight 43 to cause the LED of the LED backlight 43 to emit light.

  Here, as the dimming control means of the LED, a voltage (current) dimming method, a duty dimming method in which brightness is time-division, or the like can be applied. In general, the latter duty dimming method is preferably used in order to cope with a high-speed response suitable for moving image display. When this duty dimming method is applied, a dimming pulse (PWM signal) for driving the LED is generated, and the pulse width is varied so that the duty ratio is in accordance with the PWM ratio setting data. Can be dimmed. Further, when the voltage (current) dimming method is applied, the input voltage or input current from the power supply circuit is changed by a DC-DC converter or the like based on the output voltage control signal, and the drive voltage (current) is increased. The light can be dimmed by directly changing the LED current.

  In the liquid crystal television device 30, the audio signal output from the switching unit 37 is processed by the audio processing unit 38 and output from the speaker 39. Further, the remote control light receiving unit 31 receives a remote control operation signal by infrared rays transmitted from the remote control device 50 and sends it to the control unit 32. The control unit 32 detects and analyzes the remote control operation signal received by the remote control light receiving unit 31, and performs these operations on the tuner 35, the switching unit 37, the video processing unit 40, the LCD control unit 41, the audio processing unit 38, and the like. A control signal to be controlled is output. The control unit 32 uses programs and data stored in the memory 33. In addition, operation input by the user to the liquid crystal television device 30 can be executed using not only the remote control device 50 but also operation keys and switches provided in the main body operation unit of the liquid crystal television device 30.

  The image display device according to the present invention is not limited to the above-described liquid crystal television device, and various images having a configuration in which a display panel such as a liquid crystal panel is illuminated from the back to generate a display image. It can be applied to a display device.

  As described above, according to the present invention, in the LED lighting device using LEDs as light sources, by providing means for bypassing the current in parallel with the LEDs connected in series, other LEDs other than the failed LED are provided. Since the LED can be turned on, a decrease in luminance due to an open failure of the LED can be reduced.

It is a figure for demonstrating the structural example of the direct type | mold LED backlight apparatus to which the LED lighting apparatus which concerns on this invention is applied. It is a block diagram which shows the circuit structural example of the LED backlight apparatus shown in FIG. It is the figure which showed typically the example of LED connection structure in the LED unit of the LED backlight apparatus which concerns on one Embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is the figure which showed typically the LED connection structural example in the LED unit of the LED backlight apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structural example of the liquid crystal television apparatus comprised as an image display apparatus of this invention. It is the schematic which shows the circuit structure of the conventional direct type | mold LED backlight apparatus. It is the schematic which shows the circuit structure of the conventional direct type | mold LED backlight apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... LED illumination apparatus (LED backlight apparatus), 11 ... LED, 11a-11n ... LED unit, 12 ... Diffusing plate, 13 ... Optical sheet, 14 ... Reflecting plate, 15 ... Housing | casing, 16 ... Liquid crystal panel, 20 ... Power supply circuit, 21a to 21n ... Current control unit, 30 ... Liquid crystal television device, 31 ... Remote control light receiving unit, 32 ... Control unit, 33 ... Memory, 34 ... Antenna, 35 ... Tuner, 36 ... Video input terminal, 37 ... Switching unit, 38 ... audio processing unit, 39 ... speaker, 40 ... video processing unit, 41 ... LCD control unit, 42 ... light source driving unit, 43 ... LED backlight, 50 ... remote control device.

Claims (18)

  In an LED lighting device including an LED unit formed by connecting a plurality of LEDs in series, the LED unit includes a bypass unit for bypassing current when one or more LEDs fail, and the LED unit An LED lighting device, wherein bypass means are connected in parallel.   In the LED lighting device including an LED unit formed by connecting a plurality of LEDs in series, the LED unit includes a bypass unit for bypassing a current when one or more LEDs fail, An LED lighting device, wherein the bypass means is connected in parallel for each block.   3. The LED lighting device according to claim 1, wherein a current flows when a voltage higher than a voltage for causing the LED to emit light is applied to the bypass unit.   4. The LED illumination device according to claim 1, wherein the LED unit has the plurality of LEDs arranged in a staggered manner. 5.   5. The LED lighting device according to claim 1, wherein the bypass unit is configured by a Zener diode. 6.   5. The LED illumination device according to claim 1, wherein the bypass unit is configured by a diode. 6.   5. The LED lighting device according to claim 1, wherein the bypass unit is configured by a transistor circuit. 6.   5. The LED lighting device according to claim 1, wherein the bypass unit is composed of another LED. 6.   9. The LED lighting device according to claim 8, wherein the LED unit includes a plurality of LED blocks formed by connecting two LEDs in series and two in parallel.   9. The LED illumination device according to claim 8, wherein the LED unit includes a plurality of LED blocks formed by connecting two LEDs in parallel.   9. The LED lighting device according to claim 1, wherein the LED unit includes the LED and the bypass unit as one component. 10.   In an LED lighting device including an LED unit formed by connecting a plurality of LEDs in series, the LED unit includes bypass means for bypassing current when one or more LEDs fail, and voltage of the bypass means The LED illumination device is characterized in that the bypass means and the voltage detection means are connected in parallel for each LED.   13. The LED lighting device according to claim 12, wherein the plurality of voltage detection means are connected to each other via a current backflow prevention circuit and grounded via the voltage detection circuit.   The LED lighting device according to claim 13, wherein the current backflow prevention circuit is a diode.   15. The LED lighting device according to claim 13 or 14, wherein the voltage detection circuit includes a voltage detection resistor and a voltage measuring device.   16. The LED lighting device according to claim 12, wherein the bypass means includes a Zener diode and a diode.   An LED backlight device comprising the LED illumination device according to any one of claims 1 to 16, wherein the object to be illuminated is illuminated from the back by light emitted from the LED illumination device.   An image display device comprising the LED backlight device according to claim 17 and a liquid crystal panel illuminated by the LED backlight device.

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