Patent Publication Number: US-2007097045-A1

Title: Display apparatus having LED backlight and brightness adjusting method for the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit under 35 U.S.C. §119(a) of a Korean Patent Application No. 2005-0102337, filed on Oct. 28, 2005, in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.  
     BACKGROUND OF INVENTION  
      1. Field of Invention  
      The present invention relates to a display apparatus and a brightness adjusting method. More particularly, the present invention relates to a display apparatus including a backlight comprising an LED and a brightness adjusting method allowing the backlight to have a uniform light output distribution with a predetermined reference value.  
      2. Description of the Related Art  
      Generally, a display apparatus such as an LCD apparatus requires a separate lighting means due to non-luminescence of an image forming unit such as an LCD panel. The lighting means is typically provided on a rear side of the LCD panel as a backlight. The backlight emits light toward the LCD panel and forms an image in a front screen of the LCD apparatus. Conventionally, an incandescent electric lamp and a fluorescent lamp, among others have been used as the lighting means. However, these lamps experience problems such as low energy efficiency and overheating, among others. Therefore, an LED (light emitting diode) array has recently been developed as the lighting means.  
       FIG. 1  is a circuit diagram schematically illustrating a configuration of a backlight  10  comprising an LED array. As shown in  FIG. 1 , a plurality of LEDs  11  are arrayed on a plane, and each LED  11  includes a current supplying part  12  respectively. Each current supplying part  12  receives a control signal from a controlling part (not shown) independently and drives the corresponding LED  11 . The LEDs  11  emit light to transmit an LCD panel (not shown) provided on the front thereof.  
      However, in the conventional display apparatus including the backlight  10  comprising the LED array, since the current supplying parts  12  are independently provided to drive the respective LEDs  11 , the light output distribution of the backlight  10  may not be uniform by means of the different attributes of the current supplying parts  12  and the LEDs  11 , though the same control signals are input to all the current supplying parts  12 .  
      Consequently, it is difficult for the display apparatus to accomplish uniform brightness across the entire display screen.  
      Accordingly, there is a need for an improved brightness adjusting method and a display apparatus comprising a backlight comprising an LED capable of accomplishing uniform brightness.  
     SUMMARY OF THE INVENTION  
      An aspect of exemplary embodiments of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of exemplary embodiments of the present invention is to provide a display apparatus including a backlight comprising an LED and a brightness adjusting method capable of accomplishing uniform brightness across the entire display screen.  
      Exemplary embodiments of the present invention can be achieved by providing a display apparatus comprising a backlight, a plurality of LEDs and a plurality of current supplying parts. A driving current is respectively supplied to the LEDs by the plurality of current supplying parts. A light sensor receives light generated from the LEDs and a controlling part controls the current supplying parts to selectively drive the LEDs, and adjusts the amount of the driving current of the current supplying parts to be supplied to the driven LED so that the intensity of light received by the light sensor corresponds to a predetermined reference value.  
      According to an aspect of an exemplary embodiment of the present invention, the display apparatus further comprises a plurality of light transmitting parts transmitting light generated from each LED to the light sensor, wherein the LEDs are controlled by the controlling part to respectively supply the light to the corresponding light transmitting part.  
      According to an aspect of an exemplary embodiment of the present invention, the controlling part selects one of the LEDs, and sets the intensity of the light generated from the selected LED as the reference value.  
      According to an aspect of an exemplary embodiment of the present invention, the display apparatus further comprises a storing part for storing information about the amount of the driving current of the current supplying parts to be supplied to each LED.  
      To achieve other aspects of an exemplary embodiment of the present invention, a display apparatus is provided. The display apparatus comprises a backlight, a plurality of LEDs and a plurality of current supplying parts respectively supply a driving current to the LEDs. A storing part stores information about the amount of the driving current to be supplied to the LED so that the intensity of light generated from the LEDs corresponds to a predetermined reference value and a controlling part controls the amount of the driving current of the current supplying parts based on the information stored in the storing part.  
      According to an aspect of an exemplary embodiment of the present invention, a brightness adjusting method for a display apparatus comprising a backlight with a plurality of LEDs is provided. A plurality of current supplying parts supply a driving current to the LEDs, respectively. A predetermined reference value is set for the intensity of light, light generated from the LEDs is received and selectively driven by controlling the current supplying parts, and the amount of the driving current of the current supplying parts is adjusted so that the intensity of the received light corresponds to the reference value.  
      According to another aspect of an exemplary embodiment of the present invention, the reference value setting stage comprises selecting one of the LEDs, and setting the intensity of light generated from the selected LED as the reference value.  
      According to an aspect of an exemplary embodiment of the present invention, the brightness adjusting method further comprises storing information about the amount of the driving current of the current supplying parts to be supplied to each LED.  
      According to an aspect of an exemplary embodiment of the present invention, a brightness performing method for a display apparatus comprising a backlight with a plurality of LEDs is provided. A plurality of current supplying parts supply a driving current to the LEDs, respectively. Information about the amount of the driving current to be supplied to each LED is provided so that the intensity of light generated from the LEDs corresponds to a predetermined reference value and the amount of the driving current of the current supplying parts is adjusted based on the provided information.  
      Other objects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other exemplary objects, features, and advantages of certain exemplary embodiments of the prevent invention will be apparent from the following description taken in conjunction with the accompany drawings, in which:  
       FIG. 1  is a circuit diagram of a backlight according to a conventional display apparatus;  
       FIG. 2  is a circuit diagram schematically illustrating a display apparatus according to an exemplary embodiment of the present invention;  
       FIG. 3  is a flowchart illustrating a brightness adjusting method for a display apparatus according to an exemplary embodiment of the present invention; and  
       FIG. 4  is a flowchart illustrating a method for accomplishing a uniform brightness distribution in a display apparatus according to an exemplary embodiment of the present invention. 
    
    
      Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.  
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
      As shown in  FIG. 2 , a backlight  110  includes LEDs  112  arranged in a 3 by 3 configuration on a plane. Alternatively, the backlight  110  may include LEDs  112  with other arrangements.  
      A display apparatus  100  may include the backlight  110 , a light leading tube  116 , a light sensor  117 , a controlling part  120 , and a storing part  130  provided to control the backlight  110 .  
      The backlight  110  includes the plurality of LEDs  112  arranged on a plane, and a plurality of current supplying parts  113  corresponding to the respective LEDs  112 .  
      The respective current supplying parts  113  are electrically connected with the controlling part  120 , receive a control signal from the controlling part  120 , and supply a driving current to the corresponding LED  112 . Therefore, the LED  112  emits light comprising an intensity proportional to the supplied driving current.  
      A substrate of the backlight  110  is provided with the plurality of light leading tubes  116  respectively receiving light from the LEDs  112 . Each light leading tube  116  transmits the received light to the light sensor  117  as a light transmitting part.  
      The light sensor  117  is preferably provided on the substrate of the backlight  110  and detects the light transmitted through each light leading tube  116 .  
      The controlling part  120  measures the intensity of the light detected by the light sensor  117 . The controlling part  120  may be provided on the substrate of the backlight  110 . Alternatively, the controlling part  120  may be provided in other positions.  
      The storing part  130  stores a reference value for light intensity demanded from the LEDs  112 . The reference value may have multiple values classified by output levels of the LEDs  112 .  
      The controlling part  120  compares the intensity of the light emitted from the LED  112  and detected by the light sensor  117  with the reference value stored in the storing part  130 , and generates a compensation signal according to the difference. The controlling part  120  then sends the compensation signal to the corresponding current supplying part  113  to be added to the control signal which has already been sent. Accordingly, the current supplying part  113  may receive the control signal added with the compensation signal, and supply an adjusted driving current to the corresponding LED  112 . Thus, the LED  112  generates light comprising an intensity adjusted to the reference value.  
      Then, the controlling part  120  stores information including the compensation signal in the storing part  130 . Here, the information including the compensation signal corresponds to information relating to the amount of the driving current which allows the LED  112  to generate light comprising an intensity corresponding to the reference value in a standpoint of the current supplying part  113 .  
      The above adjustment of the light of the LED  112  may be performed to all the LEDs  112  provided to the backlight  110 , and consequently, as illustrated in  FIG. 2 , compensation values di 11  to di 33  are respectively attached to signal currents i supplied to the current supplying parts  113 .  
      Here, the reference value for the intensity of light stored in the storing part  130  may be set to have a predetermined value in a manufacturing process, or by selection of a user or service personnel.  
      Alternatively, the reference value may be set to comprise a value corresponding to the intensity of the light generated from one of the plurality of LEDs  112 . For example, an LED 22  is driven, and then the intensity of light generated from the LED 22  is measured through the light sensor  117  and the controlling part  120  to be set as the reference value. Therefore, all the remaining LEDs  112 , except the LED 22 , are adjusted to have a light intensity corresponding to the LED 22 .  
      The controlling part  120  stores information about the amount of driving current to be supplied to the corresponding LED  112  from each current supplying part  113  in the storing part  130  so that each LED  112  may emit light comprising the light intensity corresponding to the reference value. Thus, the controlling part  120  controls each current supplying part  113  based on the information stored in the storing part  130 , and accordingly the backlight  110  may generate light comprising uniform brightness distribution.  
      Further, the controlling part  120  may add or subtract information about an operational environment of the display apparatus  100  to or from the control signal. The information about the operational environment may comprise temperature information affecting the light intensity of the LED  112  and an image information input to the display apparatus  100 . The temperature information may be obtained through a temperature sensor provided on the LED  112 . The temperature information and the image information may comprise a functional relation with the driving of the LED  112 .  
      The adjustment of light of the LED  112  may be performed in the manufacturing process of the display apparatus  100 . In the manufacturing process of the display apparatus  100 , data comprising information about the amount of driving current to be supplied to the current supplying part  113  for obtaining the uniform brightness distribution of the backlight  110  is stored to the storing part  130 . Also, the display apparatus  100  is manufactured without the light leading tube  116  and the light sensor  117 , and the controlling part  120  is manufactured without the function for adjusting the amount of driving current of the current supplying part  113 .  
      In the display apparatus  100 , to control each current supplying part  113 , the controlling part  120  sends the control signal optimally adjusted based on the data stored in the storing part  130  to each current supplying part  112 . Therefore, each current supplying part  113  may supply the adjusted driving current to the corresponding LED  112 . Consequently, each LED  112  may generate light comprising the uniform light intensity corresponding to the reference value.  
       FIG. 3  is a flowchart illustrating a brightness adjusting method for the display apparatus  100  in  FIG. 2 . Initially, a reference value for the intensity of light demanded from each LED  112  is set (S 110 ). The reference value may be set to have a predetermined selected value, or to have the value corresponding to the intensity of light generated from one LED  112  selected among the plurality of LEDs  112 .  
      The current supplying part  113  is driven for the LED  112  to generate light, and then the intensity of the light generated from the LED  112  is measured (S 120 ).  
      The measured light intensity and the reference value are compared to each other (S 130 ). If the measured intensity of the light and the reference value are not substantially the same, the adjusted control signal to compensate for the difference between the values is sent (S 131 ) to the LED to be measured and to measure light intensity. According to the comparison result, a control signal adjusted to compensate for the difference between the values is sent to the current supplying part  113  to drive again the LED  112  (S 140 ). After driving the LED  112 , the light intensity measured may be compared with the reference value again. If the light intensity and the reference value are different, the control signal adjusted to compensate for the difference between the values may be sent again to the current supplying part  113  to drive the LED  112 .  
      If the measured intensity of the light generated from the LED  112  driven by the adjusted control signal and the reference value are substantially the same, the data relating to the adjusted control signal (such as, the amount of adjusted driving current of the current supplying part  113 ) is stored (S 150 ).  
      A determination is then made as to whether other LEDs  112  to be measured exist (S 160 ). If other LEDs  112  to be measured exist, the above steps (S 120  to S 150 ) are repeated to the other LEDs  112 . If no further LEDs  112  to be measured exist, the brightness adjusting method is completed.  
       FIG. 4  is a flowchart illustrating a method for accomplishing a uniform brightness distribution for the display apparatus  100  by using the data relating to the control signal generated and stored according to the brightness adjusting method in  FIG. 3 . Initially, the information relating to the amount of the driving current with respect to each LED  112 , that is, the information about the adjusted control signal with respect to each current supplying part  113  is called (S 210 ). Here, the information is provided through the brightness adjusting method in  FIG. 3 . The information may be called from the storing part  130 .  
      Each current supplying part  113  and the corresponding LED  112  are driven based on the called information (S 220 ). Accordingly, all the LEDs  112  provided to the backlight  110  can generate light comprising the same light intensity, and thus, the backlight  110  can emit light comprising the uniform light distribution over the entire display screen.  
      The display apparatus and the brightness adjusting method, according to an exemplary embodiment of the present invention, allow all the LEDs provided to the backlight of the display apparatus to generate light comprising the same light intensity, and accordingly can accomplish the uniform brightness distribution over the entire display screen.  
      While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.