JP4776463B2 - Surface light source device, illumination device, backlight device, and display device - Google Patents

Description

  The present invention relates to a surface light source device, and more particularly to a surface light source device such as a backlight for a flat display.

  In recent years, thin televisions and thin displays using liquid crystal panels have been actively developed. The liquid crystal is an element that plays a role of a shutter without emitting light by itself. Therefore, in a transmissive liquid crystal display, a surface light source device called a backlight plays a very important role, and the color gamut of the backlight determines the color gamut of the display. Many current liquid crystal displays use a cold cathode tube as a backlight. However, cold cathode tubes have the disadvantage that the color gamut is narrow and that they contain mercury.

  In order to overcome the above drawbacks, for example, Patent Document 1 discloses a surface light source device in which a large number of LEDs (Light Emitting Diodes) are arranged in a two-dimensional array.

  In addition, in order to reduce the number of LED drivers for driving LEDs in current and to make the current flowing through the LEDs uniform, a method of connecting a plurality of LEDs in series as shown in FIG. 9 is conventionally used.

FIG. 9 is a block diagram showing a configuration of a conventional surface light source device.
Referring to FIG. 9, this surface light source device has a configuration in which a large number of LEDs are arranged in a two-dimensional array using the above-described series connection method. This surface light source device includes a PWM signal generation circuit 100, LEDs 101A to 104A, LEDs 101B to 104B, LEDs 101C to 104C, LEDs 101D to 104D, and LED drivers (drive circuits) 105A to 105D.

  The LED driver 105A drives the LEDs 101A to 104A, the LED driver 105B drives the LEDs 101B to 104B, the LED driver 105C drives the LEDs 101C to 104C, and the LED driver 105D drives the LEDs 101D to 104D.

  Patent Document 2 discloses a surface light source device in which two light emitting elements that are not adjacent to each other are connected in series as a set, and each set is connected in parallel to a power source.

Further, in Patent Document 3, a plurality of light emitting elements are divided into a plurality of groups in which the light emitting elements are connected in series for each group, and a constant voltage is applied to each of the plurality of groups from a power source. A surface light source device is disclosed in which light emitting elements are opposed to a side end surface of a light guide plate and arranged along the side end surface.
JP 2005-115372 A JP 2000-89224 A Japanese Patent Laid-Open No. 2004-233809

  However, in the conventional surface light source device shown in FIG. 9, for example, when the LED 101A breaks, the supply current to the LEDs 102A to 104A driven by the LED driver 105A is cut off and the LEDs 102A to 104A are turned off. If it does so, the upper left area | region of the area | region enclosed with the dotted line of FIG. 9, ie, the area | region irradiated with light by LED101A-104A will become dark, and a defect will become very conspicuous.

  Also, in the surface light source devices described in Patent Documents 2 and 3, the portion where the optical element fails and is extinguished is still conspicuous, and the luminance cannot be restored to a state substantially equivalent to that before the failure.

Therefore, an object of the present invention is to provide a surface light source device , an illuminating device, a back light source , and the like that can restore the luminance to a state substantially equivalent to that before the light is turned off even if some of the light emitting elements are turned off for some reason. A light device and a display device are provided.

In order to solve the above problems, a surface light source device according to an aspect of the present invention includes a plurality of light emitting element sets each including a plurality of light emitting elements that are not electrically connected in series with each other, and each of the light emitting element sets for at least part of a region where each light emitting element is irradiated with light, the other light emitting elements are arranged in the area and weight of so that when exposed to light, each region in which a plurality of light-emitting elements set is irradiated with light is set the different, the plurality of light emitting elements of each set, the other set of corresponding light-emitting element and electrically connected in series, provided corresponding to the group of serially connected light emitting elements, the group of the corresponding light emitting element The plurality of drive circuits irradiate the failed light emitting element when a part of the light emitting element fails and the light quantity of the light emitting element connected in series with the failed light emitting element changes. Increase the brightness of light-emitting elements with overlapping regions That.
Preferably, the first light-emitting element group among the plurality of light-emitting element groups includes first and third light-emitting elements, and the second light-emitting element group among the plurality of light-emitting element groups includes the second and fourth light-emitting element groups. Including a light emitting element, the first light emitting element and the second light emitting element are electrically connected in series, the third light emitting element and the fourth light emitting element are electrically connected in series, and the first light emitting element and the first light emitting element The light-emitting element 3 irradiates light in substantially the same region, the second light-emitting element and the fourth light-emitting element irradiate light in substantially the same area, and the first light-emitting element and the third light-emitting element irradiate light. The region where the second light emitting element and the fourth light emitting element irradiate light are not all or part of the region where light is emitted, and the plurality of driving circuits include the first light emitting element and the second light emitting element. A first driving circuit for driving the second light emitting element, and a second driving circuit for driving the third light emitting element and the fourth light emitting element. And a dynamic circuit, the light-emitting element for emitting light to substantially the same area, Ru is set disposed.

  Preferably, each light emitting element that irradiates light to substantially the same region is sealed in the same package.

  Preferably, the surface light source device further controls light emitted from the first light-emitting element to the fourth light-emitting element so that the light from the first light-emitting element and the third light-emitting element is in substantially the same region. A region where light is emitted from the second light-emitting element and the fourth light-emitting element to substantially the same region, and the first light-emitting element and the third light-emitting element emit light; The element and the fourth light emitting element include a light distribution unit that does not match all or part of the region irradiated with light.

Preferably, the drive circuit includes a failure detection unit that detects a conduction failure of the light emitting element.
Preferably, the failure detection unit includes a conversion element that converts a current output from the light emitting element to the drive circuit into a voltage, compares the converted voltage with a predetermined voltage, and conducts when the converted voltage is higher. Judge as a failure.
Preferably, the drive circuit includes a failure detection unit that detects a disconnection failure of the light emitting element.
Preferably, the failure detection unit includes a conversion element that converts a current output from the light emitting element to the drive circuit into a voltage, compares the converted voltage with a predetermined voltage, and disconnects when the converted voltage is lower. Judge as a failure.
Preferably, the light emitting element is a light emitting diode.

  According to the present invention, even when some of the plurality of light emitting elements are turned off for some reason, the luminance can be recovered to a state substantially equivalent to that before the light is turned off.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a block diagram showing the configuration of the surface light source device according to the first embodiment of the present invention.

  Referring to FIG. 1, a surface light source device 201 includes a PWM signal generation circuit (drive control circuit) 100, LEDs (light emitting elements) 101A to 104A, LEDs 101B to 104B, LEDs 101C to 104C, and LEDs 101D to 104D. LED drivers (drive circuits) 105 </ b> A to 105 </ b> D and an LED mounting substrate 106 are provided.

  The LEDs 101A to 104A are electrically connected in series, the LEDs 101B to 104B are electrically connected in series, the LEDs 101C to 104C are electrically connected in series, and the LEDs 101D to 104D are electrically connected in series.

  LED 101A, LED 101B, LED 101C, and LED 101D are arranged close together, LED 102A, LED 102B, LED 102C, and LED 102D are arranged close together, and LED 103A, LED 103B, LED 103C, and LED 103D are arranged. The LED 104A, the LED 104B, the LED 104C, and the LED 104D are closely arranged and arranged in close proximity.

  The LED driver 105A drives the LEDs 101A to 104A, the LED driver 105B drives the LEDs 101B to 104B, the LED driver 105C drives the LEDs 101C to 104C, and the LED driver 105D drives the LEDs 101D to 104D.

  More specifically, the PWM signal generation circuit 100 generates a PWM (Pulse Width Modulation) signal having a duty ratio corresponding to the luminance for each LED driver, and outputs the generated signals to the LED drivers 105A to 105D. LED drivers 105 </ b> A to 105 </ b> D drive LEDs in accordance with the PWM signal received from PWM signal generation circuit 100. For example, the LED drivers 105A to 105D draw current from the fixed power source VLED and supply it to the LED when the PWM signal is at a high level.

FIG. 2 is a cross-sectional view of the surface light source device according to the first embodiment of the present invention.
Referring to FIG. 2, LED mounting substrate 106 mounts each LED and has a function as a reflector and a heat sink. In FIG. 2, for convenience of showing a cross section, LED 101A, LED 101B, LED 102A and LED 102B, and LED drivers 105A and 105B corresponding to these LEDs are shown.

  As indicated by the dotted arrows, the light emitted from each LED is applied to the optical sheet 301 including a prism sheet, a polarizing mirror sheet, a diffusion sheet, and the like located above the LED mounting substrate 106, and luminance unevenness and color Unevenness is reduced. And the light which passed the optical sheet 301 is irradiated to the liquid crystal panel 300 as backlight light. Here, since the LEDs 101A to 101D are arranged in close proximity to each other, the light emitted from the LEDs 101A to 101D is applied to substantially the same region in the optical sheet 301 as indicated by a dotted arrow. Further, since the LEDs 102A to 102C and 102D are arranged in close proximity to each other, the light emitted from the LEDs 102A to 102D is applied to substantially the same region in the optical sheet 301 as indicated by dotted arrows. Since the LEDs 101A to 101D, the LEDs 102A to 102D, the LEDs 103A to 103D, and the LEDs 104A to 104D are not closely arranged in close proximity, light is emitted to different areas in the optical sheet 301. In other words, the region where the LEDs 101A to 101D irradiate light, the region where the LEDs 102A to 102D irradiate light, the region where the LEDs 103A to 103D irradiate light, and the region where the LEDs 104A to 104D irradiate light are all or Some do not match.

  For example, when all of the LEDs 101A to 104A driven by the LED driver 105A are extinguished due to a disconnection failure of the LED 101A, the PWM signal generation circuit 100 sets the duty of the PWM signal output to the LED drivers 105B, 105C, and 105D. By changing the ratio, control is performed to increase the luminance of the LEDs 101B to 104B, 101C to 104C, and 101D to 104D.

  More specifically, the PWM control circuit 100 increases the duty ratio of the PWM signal output to the LED drivers 105B, 105C, and 105D when the LED 101A breaks, for example, the ratio of the period during which the PWM signal becomes high level in a predetermined period Raise. That is, it is assumed that the duty ratios of the PWM signals output to the LED drivers 105A, 105B, 105C, and 105D are all 25% before the LED 101A breaks down. When the LED 101A breaks down, the PWM control circuit 100 increases the duty ratio of the PWM signal output to the LED drivers 105A, 105B, 105C, and 105D to 33.3%, thereby compensating the luminance of the unlit LEDs 101A to 104A. To do. With such a configuration, the luminance of the backlight light that passes through the optical sheet 301 and is applied to the liquid crystal panel 300 can be recovered to a state substantially equivalent to that before the disconnection failure.

  Further, the PWM control circuit 100 is used when, for example, only the LED 101A is extinguished due to the conduction failure of the LED 101A, or when the LED 101A is in an abnormal lighting state such as a decrease in luminance due to deterioration over time. Fixes the duty ratio of the PWM signal output to the LED driver 105A to 0%, for example, the PWM signal at a low level. As a result, the LEDs 101A to 104A are intentionally turned off to create the same state as when the LED 101A breaks down. The PWM control circuit 100 increases the luminance of the LEDs 101B to 104B, 101C to 104C, and 101D to 104D by increasing the duty ratio of the PWM signal output to the LED drivers 105B, 105C, and 105D, as in the case of the disconnection failure. increase. With such a configuration, the luminance of the backlight light that passes through the optical sheet 301 and is applied to the liquid crystal panel 300 can be recovered to a state substantially equivalent to that before the disconnection failure.

  By the way, in the conventional surface light source device shown in FIG. 9 and the surface light source devices described in Patent Documents 1 to 3, the location where the optical element has failed and is extinguished is conspicuous, and the luminance is restored to a state substantially equivalent to that before the failure. There was a problem that it was not possible. However, in the surface light source device according to the first embodiment of the present invention, a plurality of LEDs that are not connected in series, for example, LEDs 101A to 101D, are closely arranged, and light emitted from the LEDs 101A to 101D. Is irradiated to substantially the same region in the optical sheet 301. Since a plurality of LEDs connected in series, for example, LEDs 101A to 104A, are not arranged close together, all or a part of the light irradiation region in the optical sheet 301 does not match. An LED drive circuit is provided for each of the plurality of LEDs connected in series. With such a configuration, for example, by turning off the LED connected in series to the LED having an abnormality as described above and increasing the luminance of the LED not connected in series to the LED having an abnormality, the luminance can be increased. It is possible to recover to a state substantially the same as before turning off.

  The surface light source device according to the first embodiment of the present invention is configured to include 16 LEDs as shown in FIG. 1, but the present invention is not limited to this. For example, as shown in FIG. 2, the surface light source device includes an LED (first light emitting element) 101A, an LED (second light emitting element) 102A, an LED (third light emitting element) 101B, and an LED (first light emitting element). 4 light-emitting elements) 102B, and only the LED driver (first driving circuit) 105A and the LED driver (second driving circuit) 105B can be used as LED drivers. Even with such a configuration, the object of the present invention can be achieved.

  The surface light source device according to the first embodiment of the present invention can be suitably used for a backlight device of a liquid crystal display and other illuminations.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Second Embodiment>
The present embodiment relates to a surface light source device in which LEDs are packaged with respect to the surface light source device according to the first embodiment. The contents other than those described below are the same as those of the surface light source device according to the first embodiment.

FIG. 3 is a diagram showing a configuration of a surface light source device according to the second embodiment of the present invention.
Referring to FIG. 3, the surface light source device 202 further includes LED packages 111 to 114 with respect to the surface light source device 201.

  Referring to FIG. 3, LEDs 101A, 101B, 101C and 101D are sealed in LED package 111, LEDs 102A, 102B, 102C and 102D are sealed in LED package 112, and LEDs 103A, 103B, 103C and 103D are LED packages. The LED 104A, 104B, 104C and 104D are sealed in the LED package 114.

  Here, "a plurality of LEDs are sealed in a package" means a state in which a plurality of LED chips are housed in a package having connection terminals and then sealed with a high refractive index resin. And a state in which a plurality of LED chips are mounted in proximity to the LED mounting substrate 106 and sealed with a high refractive index member such as a continuous lump of resin. .

  FIG. 4 is a cross-sectional view of a surface light source device according to a second embodiment of the present invention. In FIG. 4, for the convenience of showing a cross section, LED 101A, LED 101B, LED 102A and LED 102B, and LED drivers 105A and 105B corresponding to these LEDs are shown.

  With the configuration in which a plurality of LEDs are sealed in the same package, for example, the LEDs 101A and 101B can be arranged in close proximity to each other. With such a configuration, as indicated by the dotted arrows in FIG. 4, the area irradiated with the light from the LEDs 101 </ b> A and 101 </ b> B on the optical sheet 301 is further closer than the surface light source device according to the first embodiment. The brightness unevenness and color unevenness of the backlight of the surface light source device in a state where the brightness of the LED turned off due to a disconnection failure or the like is supplemented by another LED can be reduced.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Third Embodiment>
The present embodiment relates to a surface light source device in which the light collection method is changed with respect to the surface light source device according to the first embodiment. The contents other than those described below are the same as those of the surface light source device according to the first embodiment.

FIG. 5 is a cross-sectional view showing a configuration of a surface light source device according to the third embodiment of the present invention.
Referring to FIG. 5, the surface light source device 203 further includes optical elements (light distribution units) 501 </ b> A to 504 </ b> A, optical elements (light distribution units) 501 </ b> B to 504 </ b> B, and optical elements ( (Light distribution part) 501C-504C and optical element (light distribution part) 501D-504D are provided.

  In FIG. 5, for convenience of showing the cross section, LED 101A, LED 101B, LED 102A and LED 102B, optical element 501A, optical element 501B, optical element 502A and optical element 502B, and LED drivers 105A and 105B corresponding to these LEDs. Is shown.

  The LEDs 101A to 101D, LEDs 102A to 102D, LEDs 103A to 103D, and LEDs 104A to 104D are not collectively arranged in terms of mounting positions, but optical elements 501A to 501D, 502A to 502D, and 503A that control the light distribution characteristics of the LEDs. ˜503D and 504A to 504D are provided so as to be optically arranged together.

  The optical elements 501 </ b> A to 501 </ b> D are designed and adjusted so that the light emitted from the LEDs 101 </ b> A to 101 </ b> D is controlled and the light from the LEDs 101 </ b> A to 101 </ b> D is irradiated on substantially the same region in the optical sheet 301. Similarly, the optical elements 502A to 502D, 503A to 503D, and 504A to 504D control the light emitted from the LEDs 102A to 102D, the LEDs 103A to 103D, and the LEDs 104A to 104D, respectively, so that the LEDs 102A are arranged in substantially the same region in the optical sheet 301. -102D, LEDs 103A-103D and LEDs 104A-104D are designed and adjusted to be illuminated.

  The optical elements 501A to 501D, 502A to 502D, 503A to 503D, and 504A to 504D are irradiated with light from the LEDs 101A to 101D, the LEDs 102A to 102D, the LEDs 103A to 103D, and the LEDs 104A to 104D, respectively, in different regions of the optical sheet 301. Designed and tuned to. In other words, in other words, the region where the LEDs 101A to 101D irradiate light, the region where the LEDs 102A to 102D irradiate light, the region where the LEDs 103A to 103D irradiate light, and the region where the LEDs 104A to 104D irradiate light. , All or part does not match.

  Therefore, in the surface light source device according to the third embodiment of the present invention, as in the surface light source device according to the first embodiment of the present invention, some of the plurality of light emitting elements are turned off for some reason. However, it is possible to restore the luminance to a state substantially equivalent to that before the light is turned off.

  Note that the surface light source device may be configured to combine the adjustment of the irradiation area by the mounting position of each LED and the adjustment of the irradiation area by the optical element.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Fourth embodiment>
The present embodiment relates to a surface light source device including an LED driver having a failure detection function with respect to the surface light source device according to the first embodiment. The contents other than those described below are the same as those of the surface light source device according to the first embodiment.

FIG. 6 is a block diagram showing a configuration of a surface light source device according to the fourth embodiment of the present invention.
Referring to FIG. 6, the surface light source device 204 includes LED drivers 605 </ b> A to 605 </ b> D instead of the LED drivers 105 </ b> A to 105 </ b> D with respect to the surface light source device 201. Hereinafter, when the LED drivers 605A to 605D are collectively referred to, reference numeral 605 is used.

  The LED driver 605 detects whether or not the LED being driven has failed, and outputs a failure detection signal indicating whether or not the LED has failed to the PWM signal generation circuit 600.

  When the PWM signal generation circuit 600 recognizes that the LED has failed with reference to the failure detection signals from the LED drivers 605A to 605D, it responds to the failed LED regardless of the failure mode such as disconnection failure or conduction failure. Reduce the duty ratio of the PWM signal to the LED driver to 0%. Thereby, all the LEDs connected in series to the failed LED are turned off. Then, the PWM signal generation circuit 600 increases the duty ratio of the PWM signal to the LED driver corresponding to the LED that is not connected in series to the failed LED. Thereby, the brightness | luminance of LED which is not connected in series with the failed LED can be raised, and the brightness | luminance of backlight light can be recovered | restored to the state substantially equivalent to before failure.

  FIG. 7 is a block diagram of the LED driver 605 having a function of generating a failure detection signal.

  Referring to FIG. 7, LED driver 605 includes an FET (Field Effect Transistor) 700 and a failure detection unit 300. Fault detection unit 300 includes a resistance element 701, a voltage comparator 702, a voltage comparator 703, a logic OR circuit 704, a delay element 705, and a flip-flop 706. The G point, D point, and S point in FIG. 7 indicate the gate, drain, and source of the FET 700, respectively. I represents the current flowing through the LED.

  The FET 700 operates in a saturation region, that is, a region where the current Ids flowing from the D point to the S point is constant even when the voltage Vds between the D point and the S point changes, and operates as a simple constant current source. .

  The resistance element 701 has a predetermined resistance value of several ohms to several tens of ohms, and monitors a current value.

  The voltage comparator 702 compares the drain voltage of the FET 700 with a predetermined voltage value, and outputs a high level signal when it is equal to or higher than the predetermined voltage value, and outputs a low level signal when it is lower than the predetermined voltage value. To do.

  The voltage comparator 703 compares the source voltage of the FET 700, that is, the voltage at the connection point between the FET 700 and the resistance element 701, with a predetermined voltage value, and outputs a high level signal if the voltage is less than the predetermined voltage value. If it is, a low level signal is output.

  Logic OR circuit 704 outputs a logical sum of signals received from voltage comparators 702 and 703.

  The delay element 705 compares the gate voltage of the FET 700 with a predetermined voltage value, and outputs a low level signal when the voltage is lower than the predetermined voltage value, and outputs a high level signal when the voltage is equal to or higher than the predetermined voltage value. . The delay element 705 outputs a high-level or low-level signal indicating the comparison result after a predetermined time has elapsed since the gate voltage of the FET 700 was input.

  The flip-flop 706 holds and outputs the signal received from the logic OR circuit 704 at the rising or falling timing of the output signal of the delay element 705.

  FIGS. 8A and 8B are waveform diagrams illustrating the operation of the failure detection unit 300. FIG. In FIG. 8, the waveform indicated by “PWM” is a PWM signal output from the PWM signal generation circuit 600, the waveform indicated by “CLK” is the output signal of the delay element 705, and the waveform indicated by “VD” is the drain of the FET 700. The waveform indicated by “VS” is the source voltage of the FET 700, and the waveform indicated by “Y” is an output signal of the flip-flop 706, that is, a failure detection signal.

  With reference to FIG. 8A, when any one of the plurality of LEDs driven by the LED driver 605 is broken, the current I does not flow. In this case, even if the PWM signal becomes high level and the FET 700 is turned on, the source voltage of the FET 700 is substantially at the GND level.

  Then, the voltage comparator 703 outputs a high level signal because the source voltage of the FET 700 is less than the predetermined voltage B. The logic OR circuit 704 also outputs a high level signal.

  The delay element 705 changes the output signal from the low level to the high level after a lapse of a predetermined time after the PWM signal becomes the high level and becomes equal to or higher than the predetermined voltage A.

  The flip-flop 706 holds and outputs the high level output signal received from the logic OR circuit 704 at the rising timing of the output signal of the delay element 705. That is, flip-flop 706 outputs a high-level failure detection signal indicating that a failure has been detected.

  Referring to FIG. 8B, when any one of the plurality of LEDs driven by the LED driver 605 fails in conduction, a voltage drop due to the forward voltage of the plurality of LEDs connected in series is caused. The drain voltage of the FET 700 becomes larger than that during normal operation because it decreases by the amount of the LED that has failed in conduction.

  Then, the voltage comparator 702 outputs a high level signal because the drain voltage of the FET 700 is equal to or higher than the predetermined voltage A. The logic OR circuit 704 also outputs a high level signal.

  The delay element 705 changes the output signal from the low level to the high level after a lapse of a predetermined time after the PWM signal becomes the high level and becomes equal to or higher than the predetermined voltage A.

  The flip-flop 706 holds and outputs the high level output signal received from the logic OR circuit 704 at the rising timing of the output signal of the delay element 705. That is, flip-flop 706 outputs a high-level failure detection signal indicating that a failure has been detected.

  Therefore, the failure detection unit 300 can detect both the disconnection failure and the conduction failure of the LED.

  The failure detection unit 300 is not limited to the configuration shown in FIG. 7. For example, the failure detection unit 300 determines whether or not the drain voltage when the FET 700 is on is within a predetermined voltage range. The configuration may be such that the failure of the LED is determined.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows the structure of the surface light source device which concerns on the 1st Embodiment of this invention. It is sectional drawing of the surface light source device which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the surface light source device which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the surface light source device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the surface light source device which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the surface light source device which concerns on the 4th Embodiment of this invention. It is a block diagram of the LED driver 605 provided with the function which produces | generates a failure detection signal. (A) And (b) is a wave form diagram which shows operation | movement of the failure detection part 300. FIG. It is a block diagram which shows the structure of the conventional surface light source device.

Explanation of symbols

  100 PWM signal generation circuit (drive control circuit), 101A to 104A, 101B to 104B, 101C to 104C, 101D to 104D LED, 105A to 105D, 605A to 605D LED driver (drive circuit), 106 LED mounting board, 111 to 114 LED package, 201-204 surface light source device, 300 failure detection unit, 501A-504A, 501B-504B, 501C-504C, 501D-504D optical element (light distribution unit), 700 FET, 701 resistance element, 702-703 Voltage comparison , 704 logic OR circuit, 705 delay element, 706 flip-flop.

Claims (12)

A plurality of light emitting element sets each including a plurality of light emitting elements that are not electrically connected in series with each other,
For each of the light emitting device assembly, at least a part of the region each said light emitting element for emitting light is disposed in a region and overlap with so that the other of said light emitting element is irradiated with light,
The region where the plurality of light emitting element groups emit light is different for each group,
The plurality of light emitting elements of each set are electrically connected in series with corresponding light emitting elements of other sets,
A plurality of drive circuits provided corresponding to the groups of light emitting elements connected in series, and driving the corresponding groups of light emitting elements ;
The plurality of drive circuits include:
A surface light source device that increases the luminance of a light emitting element that overlaps with the failed light emitting element when the light emitting element of the failed light emitting element and the light emitting element connected in series with the failed light emitting element change. . Of the plurality of light emitting element sets, a first light emitting element set includes first and third light emitting elements,
Of the plurality of light emitting element sets, a second light emitting element set includes second and fourth light emitting elements,
The first light emitting element and the second light emitting element are electrically connected in series;
The third light emitting element and the fourth light emitting element are electrically connected in series;
The first light emitting element and the third light emitting element irradiate light in substantially the same region,
The second light emitting element and the fourth light emitting element irradiate light in substantially the same region,
The region where the first light-emitting element and the third light-emitting element irradiate light and the region where the second light-emitting element and the fourth light-emitting element irradiate light all or partly match. Without
The plurality of drive circuits include:
A first drive circuit for driving the first light emitting element and the second light emitting element;
A second drive circuit for driving the third light emitting element and the fourth light emitting element ,
Each light-emitting element for irradiating light to the substantially same area is set disposed, the surface light source device according to claim 1. Each light-emitting element for irradiating light to the substantially same area is sealed in the same package, a surface light source device according to claim 1 or claim 2. The surface light source device further includes:
The light emitted from the first light emitting element to the fourth light emitting element is controlled to irradiate light from the first light emitting element and the third light emitting element to substantially the same region, and A region in which light from two light emitting elements and the fourth light emitting element are irradiated in substantially the same region, and a region in which the first light emitting element and the third light emitting element emit light, and the second light emitting element The surface light source device according to claim 2 , further comprising a light distribution unit that does not match all or part of a region where the fourth light emitting element emits light. The surface light source device according to claim 1 , wherein the drive circuit includes a failure detection unit that detects a conduction failure of the light emitting element. The failure detection unit includes a conversion element that converts a current output from the light emitting element to the drive circuit into a voltage, compares the converted voltage with a predetermined voltage, and the converted voltage is higher The surface light source device according to claim 5 , wherein the surface light source device is determined to be a conduction failure. The surface light source device according to claim 1 , wherein the drive circuit includes a failure detection unit that detects a disconnection failure of the light emitting element. The failure detection unit includes a conversion element that converts a current output from the light emitting element to the drive circuit into a voltage, compares the converted voltage with a predetermined voltage, and the converted voltage is lower The surface light source device according to claim 7 , wherein the surface light source device is determined as a disconnection failure. The light emitting element is a light emitting diode, a surface light source device according to claims 1 to 8. The illuminating device provided with the surface light source device in any one of Claim 1 to 9 . The backlight apparatus provided with the surface light source device in any one of Claim 1 to 9 . A display device comprising the backlight device according to claim 11 .

Images