JP2006318733A - Lighting device and display device using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device capable of carrying out an appropriate lighting volume control in accordance with its state of use, while restraining destruction or degradation of an LED, as well as a display device excellent in visibility and display quality. <P>SOLUTION: The lighting device is provided with a light source 1 for emitting light in accordance with drive current, a temperature detecting means 4 for detecting temperature of the light source 1, a drive current setting means IM for setting a drive current IL in accordance with temperature T of the light source, a second drive current setting means IR for setting a required drive current in accordance with signals from outside, and a control means 63 for deciding on the drive current IL of the light source 1 in accordance with the signals of the IM and IR. It is so structured to variably change an allowed current IM of the light source 1 so that the drive current IL of the light source 1 shall not exceed a permissible current in the light source temperature while the light source temperature T is monitored. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination device using a light emitting diode (LED [Light Emitting Diode]) or the like as a light source and a display device using the same, and more particularly to a technology related to an LED backlight system for a liquid crystal display.

  In recent years, LED lighting devices have been used as light sources for various applications because of advantages such as power saving, long life, low heat generation, space saving, and color reproducibility.

  As a technique related to LED light emission drive control, an LED illumination device that detects the junction temperature of an LED and controls the drive current has been disclosed and proposed (see, for example, Patent Document 1).

As another conventional technique related to the present invention, a laser diode driving circuit that monitors the ambient temperature and brightness, detects deterioration of the laser diode, and controls its light output and extinction ratio to be constant is disclosed and proposed. (For example, see Patent Document 2).
JP 2004-214519 A Japanese Patent Laid-Open No. 11-135871

  Certainly, as disclosed in Patent Document 1, if the drive current is controlled based on the junction temperature of the LED, the LED can be lit without causing destruction of the LED element.

  However, the above-described prior art is merely for controlling the LED drive current in order to initially set the junction temperature of the LED to the target upper limit temperature (a constant temperature close to the maximum temperature within the temperature range in which the LED does not break down). It is only the structure which performed it. In other words, as it can be seen from the absence of descriptions and suggestions regarding determining the drive current as needed with respect to the junction temperature, the period from the start of LED driving until the junction temperature reaches near the upper limit temperature. The drive current control was not particularly positive.

  Here, a correlation characteristic shown in FIG. 5 exists between the light source temperature (the junction temperature of the LED and its surrounding temperature) and the allowable forward current. That is, the allowable forward current of the LED decreases so as to conflict with the temperature increase.

  Therefore, in the above prior art, when setting the upper limit temperature of the LED and the drive current (authorization current) that actually flows at that temperature, the LED is allowed during the period until the light source temperature reaches the vicinity of the upper limit temperature. In order to prevent the forward current (allowable forward current) from falling below the authorized current, for example, as shown by (x) in FIG. (Allowable forward current at temperature Tx) and a use upper limit temperature as Ty as shown by (y) in FIG. 5 and Iy (allowable order at temperature Ty) as the drive current. (Direction current) was used.

  However, in the case where the former configuration is adopted, the period until the ambient temperature of the LED reaches the use upper limit temperature Tx can increase the light emission amount of the LED by flowing the maximum value Ix of the allowable forward current, but it is short. In this light emission driving, the light source temperature reaches the use upper limit temperature Tx, so that the drive current must be frequently limited thereafter, which is inconvenient.

  On the other hand, when the latter configuration is adopted, the period until the light source temperature reaches the use upper limit temperature Ty is long. Therefore, the drive current limit of the LED is hardly required, but the drive current is excessively reduced in the low temperature range. As a result, the amount of emitted light could not be earned, and the ability of the LED could not be fully exhibited.

  As described above, in the conventional technique, the operating temperature range or the drive current range of the LED is limited due to the decrease characteristic of the allowable forward current with respect to the increase of the light source temperature.

  In view of the above-described problems, the present invention provides an illumination device capable of appropriately controlling the amount of light emission according to the usage state while suppressing destruction and deterioration of an LED, and also provides visibility and display. An object is to provide a display device with excellent quality.

  In order to achieve the above object, an illumination device according to the present invention sets a light source that emits light according to a drive current, a temperature detection unit that detects the temperature of the light source, and a drive current corresponding to the temperature of the light source. The signals from the first drive current setting means, the second drive current setting means for setting the required drive current according to the signal from the outside, the first drive current setting means and the second drive current setting means And a control means for determining the drive current of the light source according to the second drive current setting means when the drive current by the second drive current setting means is lower than the drive current by the first drive current setting means. When the drive current by the second drive current setting means exceeds the drive current by the first drive current setting means, the drive current according to the first drive current setting means is supplied. The light source It has a configuration to flow. By adopting such a configuration, it is possible to perform appropriate light emission amount control according to the usage status while suppressing destruction and deterioration of the light emitting diode, and extending the light emission lifetime while increasing the light emission amount of the light emitting diode. Is possible.

  The first drive current setting means has storage means for storing an authorized current value smaller than an allowable current that the light source can flow at the temperature, and the authorized current is determined by the drive current of the light source. It is preferable that the matrix data is set stepwise so as not to exceed the allowable current. The storage means stores a plurality of the matrix data, and the control means preferably selectively reads any one of the plurality of matrix data. By adopting such a configuration, it is possible to easily determine the authorized current without requiring a complicated calculation.

  Further, it is preferable that cooling means for cooling the light source is further provided, and the control means controls the cooling capacity of the cooling means in accordance with a difference amount between the allowable current and the required drive current. With such a configuration, it is possible to actively increase the amount of drive current that can be passed through the light emitting diode, so that it is possible to respond more flexibly to requests from the host. In addition, if the configuration is such that the cooling capacity of the cooling means is appropriately variably controlled according to the usage situation, the power consumption is reduced and the fan when a fan is used as the cooling means, compared to a configuration that uniformly maintains the maximum cooling capacity. It is also possible to reduce noise.

  In the illumination device having any one of the above-described configurations, the light source may be a single light-emitting diode, and temperature detection means corresponding to the light-emitting diode may be provided, or the light source may be a plurality of light-emitting diodes. It is preferable to have a predetermined number of the temperature detecting means corresponding to the diodes. Moreover, it is good to further have a voltage setting part which can change the voltage applied to the said light source according to the control signal from the said control part. By adopting such a configuration, advantages such as power saving, long life, low heat generation, space saving, and color reproducibility of the lighting device can be obtained.

  A display device according to the present invention is a display device that includes a display panel that displays an image and an illumination device that illuminates the display panel, and the illumination device is any one of the embodiments. A structure including the lighting device described above is preferable. By adopting such a configuration, it is possible to provide a long-life display device with excellent visibility and display quality by controlling the amount of emitted light appropriately according to the usage status while suppressing the destruction and deterioration of the light-emitting diode. It becomes possible to do.

  As described above, according to the present invention, it is possible to provide an illuminating device capable of appropriately controlling the amount of light emission according to the use situation while suppressing the destruction and deterioration of light emitting elements such as LEDs, and A display device having excellent visibility and display quality can be provided.

  First, a first embodiment of a display device according to the present invention will be described in detail with reference to FIG. FIG. 1 is a block diagram showing a first embodiment of a display device according to the present invention. As shown in the figure, the display device of this embodiment includes a light emitting unit 1, a light guide 2, a liquid crystal display panel 3 (hereinafter referred to as an LCD [Liquid Crystal Display] panel 3), a temperature sensor 4, and a memory. This is a transmissive liquid crystal display including a unit 5, a light amount control unit 6, a current adjustment unit 7, and a voltage adjustment unit 8.

  The light emitting unit 1 includes an LEDL 1, and the illumination light generated by the light emitting unit 1 is used as a backlight that illuminates the LCD panel 3 through the light guide path 2. In this way, if the configuration uses an LED as a backlight, it is possible to obtain effects such as power saving, long life, low heat generation, space saving, and good color reproducibility compared to a configuration using a fluorescent tube or the like. Become.

  The LED L1 is a single LED element that is whitened using a phosphor or the like, or an LED that includes three LED elements having red, green, and blue emission colors as a group. By mixing the incident light, illumination light having a desired emission color (white in the present embodiment) is generated. If such a single white LED is used as a backlight, the color reproduction range of the LCD panel 3 can be expanded compared to a configuration using a fluorescent tube or the like.

  The light guide path 2 is a means for uniformly emitting the light emitted from the light emitting section 1 and guiding it to the entire LCD panel 3, and is composed of a reflection plate and a light guide plate (a transparent plate having a special process on the surface).

  The LCD panel 3 encloses the liquid crystal between two glass plates and applies a voltage to change the molecular direction of the liquid crystal, thereby increasing or decreasing the transmittance of the light irradiated from the light emitting unit 1 through the light guide path 2. This is a means for displaying an image. The drawing control of the LCD panel 3 is performed by an LCD controller (not shown).

  The temperature sensor 4 is a temperature detection unit that detects the junction temperature by measuring the forward voltage drop Vf of the LED L1 as the light source temperature T, or detects the ambient temperature using a thermistor or the like.

  The memory unit 5 is storage means for storing matrix data MX describing the correlation between the light source temperature T and the drive current (authorization current IM) that is actually passed through the LED L1 at that temperature, and includes ROM [Read Only Memory] and It has RAM [Random Access Memory]. The authorized current IM is upper limit value information for setting how much the drive current (forward current) may flow when the light source temperature T indicates a certain value. As shown in FIG. 2 (a), the authorization current IM is determined based on the correlation characteristics between the light source temperature T and the maximum forward current (allowable forward current) that can flow through the LED L1 at that temperature. Is set stepwise so as not to exceed its allowable forward current.

  More specifically, the maximum current value Ia is set in the memory unit 5 as the authorization current IM in the temperature range of T <Ta as the matrix data MX, for example, as shown in FIG. In the temperature range of Ta ≦ T <Tb, a smaller current value Ib is set, and thereafter the authorization current IM is gradually reduced from Ic to If as the temperature of the LED L1 rises. Specifically, information that the authorization current IM is zero in the temperature range of Tf ≦ T is stored in advance. Note that the matrix data MX shown in FIG. 2 is merely an example, and the number of divisions of the temperature range and the set value of the authorized current IM can be arbitrarily changed.

  The light amount control unit 6 includes an analog / digital conversion unit 61 (hereinafter referred to as ADC 61 [Analog / Digital Converter]), a matrix comparison unit 62, and a control signal generation unit 63 as signal processing means. It is a means for controlling the light emission amount by controlling the drive current value and the drive voltage value of the LEDL1 via the current adjustment unit 7 and the voltage adjustment unit 8. The light emission amount control operation by the light amount control unit 6 will be described in detail later together with the operation description of each of the signal processing units 61 to 63.

  The current adjustment unit 7 is a unit that adjusts the drive current of the LED L1 based on the current control signal Sic from the light amount control unit 6, and includes a constant current circuit or the like.

  The voltage adjustment unit 8 is a DC / DC converter that generates a drive voltage of the LED L1 from the DC power supply voltage, and based on the voltage control signal Svc from the light amount control unit 6, the drive voltage (and thus the drive current) of the LED L1. It is a means to adjust. As the means for generating the DC power supply voltage, an AC / DC converter that converts a commercial AC voltage into a DC voltage may be used, or a battery voltage such as a secondary battery is boosted using a charge pump circuit or the like. You may make it do. If the voltage supplied to the LED 1 is sufficiently high, the voltage adjustment unit 8 may be omitted.

  Subsequently, the light emission amount control operation by the light amount control unit 6 will be described in detail together with the operation description of each of the signal processing units 61 to 63 described above.

  The ADC 61 is means for converting an analog temperature signal from the temperature sensor 4 into a digital temperature signal (light source temperature T) and sending it to the matrix comparison unit 62. The ADC 61 is also means for converting an analog current reference signal corresponding to the drive current (actual drive current IL) that actually flows through the LED L1 into a digital current reference signal and sending it to the control signal generator 63.

  The matrix comparison unit 62 compares and refers to the digital temperature signal (the light source temperature T detected by the temperature sensor 4) input from the ADC 61 and the matrix data MX read from the memory unit 5, and allows the authorization current IM that can flow to the LED L1. And an approved current setting means for transmitting the result to the control signal generator 63.

  The control signal generation unit 63 includes an actual drive current IL input from the ADC 61, an authorization current IM input from the matrix comparison unit 62, and a light emission amount input from a host (not shown) (CPU [Central Processing Unit], etc.). Based on the control signal (required drive current IR), the smaller one of the authorized current IM and the required drive current IR is set as the drive current (target drive current) that actually flows, and the actual drive current IL of the LEDL1 is set as the target drive current. It is a light emission amount control means for generating a current control signal Sic and a voltage control signal Svc so as to match.

  More specifically, the control signal generator 63 first determines whether or not the requested drive current IR from the host exceeds the authorized current IM. Here, if the former is lower than the latter, the required drive current IR is approved as the target drive current, and the actual drive current IL of the LEDL1 is adjusted to the target drive current (required drive current IR). The current control signal Sic and the voltage control signal Svc are appropriately generated. On the other hand, when the former exceeds the latter, it is not necessary to set the required drive current IR as the target drive current. Therefore, after setting the authorized current IM as the target drive current, the actual drive current IL of the LEDL1 is The current control signal Sic and the voltage control signal Svc are appropriately generated so as to match the target drive current (authorization current IM).

  For example, when the light emission amount control signal is input from the host so that the forward current Ib flows to the LED L1 when the light source temperature T is in the temperature range of T <Ta, the control signal generation unit 63 determines the request. The drive current IR (forward current Ib) is determined not to exceed the current allowable current (forward current Ia), and the forward current Ib is approved as the target drive current. The current control signal Sic and the voltage control signal Svc are appropriately generated so as to match the forward current Ib. On the other hand, when the light source temperature T rises to a temperature range of Tb ≦ T <Tc with continuous driving of the LED L1, the control signal generator 63 no longer has the required drive current IR (forward current Ib) at the present time. The current is determined so as to exceed the allowable current (forward current Ic), the forward current Ic is set as the target drive current, and the actual drive current IL of the LEDL1 is adjusted to match the forward current Ic. The control signal Sic and the voltage control signal Svc are appropriately generated.

  As described above, the illumination device mounted on the display device of this embodiment and illuminating the LCD panel 3 from the back side monitors the light source temperature T unlike the conventional configuration in which the drive current is simply set in accordance with the use temperature. On the other hand, the required drive current IR and the variably controlled authorization current IM are appropriately selected and driven so that the drive current of the LEDL1 does not exceed the allowable forward current under the light source temperature. By adopting such a configuration, it is possible to appropriately control the amount of light emission according to the usage status while suppressing the destruction and deterioration of the LED L1, in other words, to allow the maximum drive current to flow under the usage conditions. Become. Therefore, if it is the illuminating device of this embodiment, it can extend the light emission lifetime, earning the light emission amount of LEDL1, and by using the said illuminating device as a backlight of LCD panel 3 by extension, visibility or It is possible to provide a long-life transmissive liquid crystal display excellent in display quality.

  Further, as described above, in the lighting device of the present embodiment, the related information stored in the memory unit 5 is the matrix data MX describing the correlation between the light source temperature T and the approved current IM, and the approval is made. The current IM is set stepwise so that the driving current of the LED L1 does not exceed its allowable forward current (see FIG. 2). As described above, by adopting a configuration in which the authorization current IM is variably controlled step by step using the matrix data MX, the authorization current IM can be easily determined without requiring a complicated calculation or the like.

  In FIG. 1, for convenience of explanation, the signal processing units 61 to 63 are depicted as individual circuit blocks. However, these are not necessarily configured by hardware, and similar signals are generated using software. You may make it implement | achieve a process. Further, the memory unit 5, the voltage adjustment unit 8, and the current adjustment unit 7 may be incorporated in the control signal generation unit 63.

  Next, a second embodiment of the display device according to the present invention will be described in detail with reference to FIG. FIG. 3 is a block diagram showing a second embodiment of the display device according to the present invention. As shown in the figure, the display device according to the present embodiment has substantially the same configuration as that of the first embodiment described above. Therefore, the same constituent elements as those in the first embodiment are denoted by the same reference numerals as those in FIG. 1, and the description thereof is omitted. Hereinafter, the characteristic portions of the present embodiment will be described with emphasis.

  The illumination device of the present embodiment includes a cooling fan 9 that cools the light emitting unit 1 as new components, and the control signal generation unit 63 includes the current control signal Sic and the voltage control signal Svc described above. In addition to the function of generating the cooling fan 9, a function of generating the cooling capacity control signal Scc of the cooling fan 9 is newly added. The memory unit 5 is built in the light quantity control unit 6, and matrix data is stored in the memory unit 5 before use.

  In the present embodiment, the LED array LL1 formed by connecting a plurality of LEDs in series is used as the light emitting unit 1 as a specific configuration in which the light emitting unit 1 generates a relatively large amount of heat and the necessity of the cooling fan 9 is high. Although the configuration used as an example is given as an example, a configuration using an LED similar to that of the first embodiment described above may be used.

  In the lighting device having the above-described configuration, the control signal generator 63 functions as the light emission amount control means described above, and controls the cooling capacity of the cooling fan 9 according to the difference between the authorized current IM and the required drive current IR. Functions as a cooling capacity control means.

  More specifically, referring to FIG. 2 and FIG. 3, for example, the light source temperature T is in the temperature range of Tb ≦ T <Tc, and only the forward current Ic is allowed to flow as the current approval current IM. Although the control signal generator 63 is instructed to flow the forward current Ib as the requested drive current IR from the host, the control signal generator 63 sets the forward current Ic as the target drive current as described above. Above, the current control signal Sic and the voltage control signal Svc are appropriately generated so as to match the actual drive current IL of the LED array LL1 with the forward current Ic, while the authorization current IM is increased by lowering the light source temperature T. The cooling capacity control signal Scc is appropriately generated so that the cooling capacity (fan rotation speed) of the cooling fan 9 is maximized.

  In other words, as a sequence when the required drive current IR is higher than the authorized current IM, the cooling of the light source temperature T is strengthened while the authorized current IM is supplied at that time, and the requested required drive current IR is reached. Until then, the actual drive current IL is gradually increased while increasing the authorized current IM.

  In addition, when the light source temperature T is in the temperature range of T <Ta, when the LED array LL1 is instructed to pass the forward current Ic, the control signal generator 63 outputs the required drive current IR (forward It is determined that the difference between the directional current Ic) and the current approval current IM (forward current Ia) is sufficiently large, and the cooling capacity control signal Scc is appropriately generated so as to lower the cooling capacity of the cooling fan 9. On the other hand, when the light source temperature T rises to a temperature range of Ta ≦ T <Tb as the LED array LL1 is continuously driven, the control signal generator 63 determines the required drive current IR (forward current Ic) and the current approval. It is determined that the difference from the current IM (forward current Ib) is not sufficient, and the cooling capacity control signal Scc is appropriately generated so as to increase the cooling capacity of the cooling fan 9.

  That is, even when the required drive current IR is lower than the authorized current IM, the control signal generator 63 monitors the difference amount between the authorized current IM and the requested drive current IR, and determines whether there is a margin for the difference. Thus, the cooling capacity of the cooling fan 9 is controlled to increase or decrease.

  In this way, by setting the cooling capacity of the cooling fan 9 to be controlled according to the difference between the authorization current IM and the required drive current IR, the amount of drive current that can be passed through the LED array LL1 is actively increased. Therefore, it is possible to take a more flexible response to the request from the host.

  In addition, as in this embodiment, if the cooling capacity of the cooling fan 9 is appropriately variably controlled according to usage conditions, power consumption and noise are reduced compared to a structure that uniformly maintains the maximum cooling capacity. Can be achieved.

  In the above embodiment, the configuration in which the light emitting unit 1 is air-cooled using the cooling fan 9 has been described as an example. However, the configuration of the present invention is not limited to this, and the configuration of the light emitting unit 1 is not limited thereto. A water cooling system may be adopted as the cooling means, and the circulating water amount of the circulation pump may be appropriately controlled.

  Next, a third embodiment of the display device according to the present invention will be described in detail with reference to FIG. FIG. 4 is a block diagram showing a third embodiment of the display device according to the present invention. As shown in the figure, the display device according to the present embodiment has substantially the same configuration as the first and second embodiments described above. Therefore, the same components as those in the first and second embodiments are denoted by the same reference numerals as those in FIGS. 1 and 3, and the description thereof is omitted. In the following, emphasis is placed on the characteristic portions of the present embodiment. Give an explanation.

  In the illuminating device of this embodiment, the LED row | line LL1-LLn of n row | line | column (n> = 2) formed by connecting several LED in series as the light emission part 1 is used. Here, each permissible forward current of the LED rows LL1 to LLn has different characteristics depending on the structure and type of the LED constituting the LED row LL1 to LLn.

  Therefore, a plurality of temperature sensors 4 are installed for each of the LED rows LL1 to LLn or at predetermined positions as the LEDs are arranged in parallel, and are configured to detect the light source temperatures T1 to Tn. However, when the temperature difference for each LED array is small, a single light source temperature T may be detected as in the above-described embodiment.

  Further, the memory unit 5 is configured to store a plurality of matrix data MX1 to MXn for each of the LED rows LL1 to LLn or for each detected light source temperature T1 to Tn with the parallelization of the LEDs. In the present embodiment, the configuration in which the same number of matrix data MX1 to MXn as the number of LED rows LL1 to LLn is provided as an example, but the number of both does not necessarily match. For example, if there are a total of (3 × m) LED rows as a result of providing m sets of R, G, and B color LED rows, assuming that the same color LED rows have the same characteristics, Three colors of matrix data are sufficient.

  Moreover, the light quantity control part 6 is set as the structure which has the selectors 64 and 65 newly with the parallelization of the said LED.

  The selector 64 is means for selecting any one (kth Tk) of analog temperature signals (light source temperatures T1 to Tn) input from the temperature sensor 4 and sending them to the ADC 61. The selector 65 is means for selecting any one of the analog current reference signals (actual drive currents IL1 to ILn for each of the LED strings LL1 to LLn) (kth ILk) and sending it to the ADC 61. .

  The ADC 61 is means for converting a signal from the temperature sensor 4 or an analog current reference signal input via the selector 64 or the selector 65 into a digital signal and sending it to the matrix comparison unit 62.

  The matrix comparison unit 62 compares and refers to the digital temperature signal Tk input from the ADC 61 and the matrix data MXk selectively read from the memory unit 5 to determine the authorized current IMk of the LED string LLk, and the result Is transmitted to the control signal generator 63.

  The control signal generator 63 is input from a digital current reference signal (actual drive current ILk) input from the ADC 61, an authorized current setting signal (authorized current IMk) input from the matrix comparator 62, and a host (not shown). Based on the light emission amount control signal (required drive current IRk), the smaller one of the authorization current IMk and the required drive current IRk is set as the target drive current, and the actual drive current ILk of the LED array LLk is matched with the target drive current Current control signal Sick is generated.

  In addition, the light emission control part 6 carries out the time division process of the said control sequentially for every LED row LL1-LLn individually or for every predetermined group.

  As described above, the memory unit 5 stores a plurality of matrix data MX1 to MXn as a data matrix (or data table), and the matrix comparison unit 62 stores any one of the plurality of matrix data MX1 to MXn. One is selectively transmitted. With such a configuration, it is possible to easily realize the drive current control for the LED rows LL1 to LLn having different characteristics.

  Further, if the configuration is such that the drive current control is sequentially executed in a time-division manner based on the signal from the temperature sensor 4 or the analog current reference signals of the LED strings LL1 to LLn using the selectors 64 and 65, the matrix comparison unit The drive current control can be realized without imposing an excessive burden on the control signal generator 62 and the control signal generator 63. However, the configuration of the present invention is not limited to this, and the selectors 64 and 65 may be omitted, and the drive current control of the LED rows LL1 to LLn may be input in parallel and AD conversion processing may be performed simultaneously.

  In the above embodiment, the case where the present invention is applied to a transmissive liquid crystal display device has been described as an example. However, the application target of the present invention is not limited to this, and other illumination devices are used. And can be widely applied to display devices.

  The configuration of the present invention can be variously modified within the scope of the present invention in addition to the above embodiment.

  For example, in the above-described embodiment, the light emitting means for generating white light by mixing red light, green light, and blue light has been described as an example. However, the application target of the present invention is not limited to this. Of course, the present invention can also be applied to a configuration using light emitting means for emitting desired colored light by mixing other colored light and light emitting means for emitting monochromatic light.

  Further, in the above embodiment, the description has been given by taking as an example the configuration in which the authorization current IM is variably controlled step by step using the matrix data MX, but the configuration of the present invention is not limited to this, A predetermined arithmetic expression expressing the correlation between the LED temperature and the allowable forward current may be used, and the authorization current IM may be continuously variably controlled according to the light source temperature T. With such a configuration, although the processing in the control signal control unit 63 increases, more accurate drive current control can be performed.

  The illumination device according to the present invention can be used, for example, as a backlight of a liquid crystal display, and as a display device including the same, a liquid crystal television receiver (particularly a large screen), a PDA, etc. [Personal Digital / Data Assistant] liquid crystal display or mobile phone liquid crystal display.

These are block diagrams which show 1st Embodiment of the display apparatus which concerns on this invention. These are the figures which show the correlation of the light source temperature T and the authorization electric current IM, and its matrix data MX. These are block diagrams which show 2nd Embodiment of the display apparatus which concerns on this invention. These are block diagrams which show 3rd Embodiment of the display apparatus which concerns on this invention. These are figures which show the correlation characteristic between light source temperature and an allowable forward current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emission part L1 Light emitting diode LL1-LLn Light emitting diode row 2 Light guide 3 Liquid crystal display panel (LCD panel)
4 Temperature Sensor 5 Memory Unit 6 Light Control Unit 61 Analog / Digital Converter (ADC)
62 Matrix Comparison Unit 63 Control Signal Generation Unit 64, 65 Selector 7 Current Adjustment Unit 8 Voltage Adjustment Unit 9 Cooling Fan IR Light Emission Control Signal (Required Drive Current)

Claims (8)

A light source that emits light in response to a drive current, a temperature detection unit that detects the temperature of the light source, a first drive current setting unit that sets a drive current corresponding to the temperature of the light source, and a signal from the outside A second drive current setting means for setting the required drive current; and a control means for determining the drive current of the light source in accordance with signals from the first drive current setting means and the second drive current setting means. ,
When the drive current set by the second drive current setting means is lower than the drive current set by the first drive current setting means, the drive current corresponding to the second drive current setting means is supplied to the light source and the second drive current is set. An illuminating device characterized in that when the driving current by the setting means exceeds the driving current by the first driving current setting means, a driving current according to the first driving current setting means is supplied to the light source.   The first drive current setting means has storage means for storing a value of an approved current smaller than an allowable current that the light source can flow at the temperature, and the approved current is determined by the drive current of the light source. The illumination device according to claim 1, wherein the matrix data is set in a stepwise manner so as not to exceed the current.   3. The storage unit stores a plurality of the matrix data, and the control unit selectively reads any one of the plurality of matrix data. The lighting device described in 1.   The cooling means for cooling the light source is further provided, and the control means controls the cooling capacity of the cooling means in accordance with a difference amount between the allowable current and the required drive current. The lighting device according to claim 3.   The lighting device according to any one of claims 1 to 4, wherein the light source is a single light emitting diode, and has temperature detection means corresponding to the light emitting diode.   5. The lighting device according to claim 1, wherein the light source includes a plurality of light emitting diodes, and has a predetermined number of the temperature detecting units corresponding to the plurality of light emitting diodes.   The illumination device according to claim 1, further comprising a voltage setting unit that can change a voltage applied to the light source in accordance with a control signal from the control unit. A display device comprising: a display panel that displays an image; and an illumination device that illuminates the display panel, wherein the illumination device according to any one of claims 1 to 7 is used as the illumination device. A display device comprising:

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