Abstract:
An apparatus is provided that includes circuitry (i.e. a central processing unit), a peripheral device (i.e. a liquid crystal display), and a thermal coupler. The peripheral device is substantially thermally insulated from the circuitry. The thermal coupler thermally couples the circuitry and the peripheral device. A method is also provided that includes a sensing step and a causing step. The sensing step includes sensing a temperature of a peripheral device (i.e. a liquid crystal display). The causing step includes causing power to be provided to the peripheral device according to the sensed temperature.

Description:
This application is related to U.S. patent application Ser. No. 09/972,876 filed Oct. 10, 2001 and U.S. patent application Ser. No. 10/194,068 filed Jul. 15, 2002. The entire disclosure of the prior applications are considered as being part of the disclosure of the accompanying application and is hereby incorporated by reference therein. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to liquid crystal display (LCD) devices. 
   2. Background of the Related Art 
   Liquid Crystal Displays (LCD) are devices for displaying video content. An example of one use of a LCD is a viewing screen of a video camera. LCDs are relatively light weight and therefore may be well suited for portable electronic devices (i.e. a video camera). Problems do exist in the implementation of LCDs. 
   Liquid Crystal Displays (LCD) do consume electric power during operation. Many portable electronic devices that do employ LCDs run on batteries. Batteries have a finite capacity to store power, which limits the length of time that some portable electronic devices can operate. There has been a long felt need to increase the length of time that a portable electronic device can operate from battery power. Accordingly, there has been a long felt need to minimize power consumption of a LCD, without degrading quality (i.e. the consistency of the brightness of the LCD) to increase the length of time that a portable electronic device can operate. 
   The brightness of a Liquid Crystal Display (LCD) is the amount of light output from the LCD. Changes in brightness are considered by many users of LCDs as an indication of a low quality product. Accordingly, there has been a long felt need for a LCD that has consistent brightness. 
   SUMMARY OF THE INVENTION 
   Objects of the present invention at least include overcoming the disadvantages of the related art. Embodiments of the present invention relate to an apparatus comprising circuitry (i.e. a central processing unit), a peripheral device (i.e. a liquid crystal display), and a thermal coupler. The peripheral device is substantially thermally insulated from the circuitry. The thermal coupler thermally couples the circuitry and the peripheral device. For example, in some embodiments, a liquid crystal display will operate more efficiently at higher temperatures. Further, circuitry often outputs heat during operation. Often, circuitry is physically separated from the LCD and the efficiency of the LCD does not benefit from the outputted heat, absent the thermal coupler. 
   Embodiments of the present invention relate to a method comprising a sensing step and a causing step. The sensing step includes sensing a temperature of a peripheral device (i.e. a liquid crystal display). The causing step includes causing power to be provided to the peripheral device according to the sensed temperature. For example, some embodiments stabilize the brightness of a Liquid Crystal Display (LCD) by controlling the power supplied to the LCD according to the sensed temperature. For instance, if the temperature of the LCD increases (which may cause the brightness of the LCD to increase), the amount of power to the LCD is decreased to maintain a consistent brightness. This process takes advantage of the relationship of brightness of a LCD to the power supplied to the LCD. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exemplary schematic view illustrating a configuration adapted to utilize heat internally generated from a system in a LCD device power control apparatus. 
       FIG. 2  is an exemplary block diagram illustrating a configuration of a LCD device power control apparatus which utilize heat internally generated from a system. 
       FIG. 3  is an exemplary flow chart illustrating a LCD device power control method. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Systems using LCDs as display devices may be equipped with a back light lamp and a front light lamp as light sources for accurately and clearly displaying information. For such a back light lamp (hereinafter, simply referred to as a “LCD lamp”), a cold cathode fluorescent lamp (CCFL) may be used. In order to drive this lamp, it may be necessary to supply an appropriate amount of power. For example, in portable systems equipped with a LCD smaller than 14.1 inches, it may be necessary to supply an AC voltage of 200 to 700 V (40 to 150 KHz), and a current of 0.5 to 7 mA for driving a LCD lamp. In order to supply a desired voltage and a desired current to the LCD lamp, an inverter may be used. A LCD lamp may be driven by a voltage and current supplied from the inverter. Brightness of a LCD lamp may be proportional to the magnitude of current flowing through the LCD lamp. 
   In some notebook computers, brightness of a LCD lamp may be adjustable by manipulating an input device (i.e. a keyboard). Information about variation in brightness inputted by an input device may be output to a microprocessor. Brightness variation information output to a microprocessor may be converted into digital brightness adjustment information. For example, digital brightness adjustment information may be a voltage level or a variable duty width of a PWM signal, required for the brightness adjustment of a LCD lamp. Brightness adjustment information may be applied to an inverter. In accordance with brightness adjustment information, an inverter may apply to a LCD lamp a voltage and current corresponding to applied brightness adjustment information to adjust brightness of a LCD lamp. 
   One important feature of some LCD lamps (i.e. a CCFL) is that brightness of a lamp may vary in accordance with temperature of the lamp. For example, a LCD lamp may exhibit an increase in brightness proportional to the lamp&#39;s temperature. Systems using LCDs may be configured to supply, to a LCD lamp, a voltage and current determined to meet the characteristics of the LCD lamp at room temperature (i.e. 25° C.). In these systems, the brightness of the LCD lamp is adjustable only according to a user&#39;s manual input. 
   Some devices include LCDs that are thermally insulated from system circuitry (i.e. a LCD is in a separate portion of the device than system circuitry). In these devices, the ambient temperature around a LCD lamp may be inaccurately determined as being a temperature proximate to the system circuitry. Accordingly, the present invention comprises embodiments that sense temperature of a LCD lamp at the LCD lamp. 
   An inverter may supply to a LCD lamp a voltage and current at levels in accordance with brightness adjustment information received from a microprocessor. In an exemplary system, voltage levels of 0 to 5 V may be used as brightness adjustment information for a LCD lamp. Brightness adjustment information corresponding to 0 V (1 mA) exhibits minimum brightness from a LCD. Brightness adjustment information corresponding to 5 V (6 mA) may correspond to a maximum brightness of a LCD. A plurality of levels may exist between a minimum brightness level and a maximum brightness level. A difference between adjacent levels may be in 0.5 V (0.5 mA) increments. 
   For example, a LCD lamp may have a lamp temperature characteristic exhibiting a temperature increase rate of 5 cd/m 2  per 1° C. while exhibiting a brightness of 150 cd/m 2  at an ambient temperature of 25° C. 5 V (6 mA) may be applied to a LCD lamp. For example, when the ambient temperature around a LCD lamp reaches 27° C., the brightness of the LCD lamp increases to 160 cd/m 2 . When the ambient temperature around the LCD lamp further increases to 28° C., the brightness of the LCD lamp may increase to 165 cd/m 2 . When ambient temperature around a LCD lamp reaches 29° C. brightness of the LCD lamp may increase to 170 cd/m 2 . In embodiments of the present invention, voltage and current applied to a LCD lamp are reduced by amounts corresponding to a brightness increment of a LCD lamp caused by increase in ambient temperature. Accordingly, reduction of consumption of power may be accomplished while maintaining brightness of a LCD lamp. 
     FIG. 1  is an exemplary schematic view illustrating a configuration adapted to utilize heat internally generated from a system. Fan  120  may be installed in heat-generating part  110  (i.e. a CPU) to discharge heat generated from heat-generating part  110 . Duct  130  may be arranged beneath cover  105 . Heat collecting part  140  may be formed around LCD lamp  150 . Duct  130  may have an inlet arranged near a discharge portion of fan  120 . Duct  130  may have an outlet connected to heat collecting part  140 . Fan  120  may be installed in a system to transfer heat generated from heat-generating part  110  to heat collecting part  140  connected to duct  130 . 
   Ambient temperature around LCD lamp  150 , which may be arranged inside heat collecting part  140 , may be increased by heat transferred to heat collecting part  140 . Increased ambient temperature around LCD lamp  150  may be sensed by a temperature sensor (not shown) arranged at a position proximate to heat collecting part  140 . The temperature sensor may apply a sensing signal indicative of a sensed ambient temperature to a microprocessor included in a system. 
   An additional fan may be provided in order to prevent heat from flowing in reverse into a system via duct  130 . An air discharge section may be provided at a portion of heat collecting part  140 , thereby discharging hot air primarily transferred to heat collecting part  140  outwardly from a system. 
     FIG. 2  is an exemplary block diagram illustrating a configuration of a LCD device power control apparatus according to embodiments of the present invention. A LCD device power control apparatus may include a temperature sensor  210 , a microprocessor  220 , a ROM table  230 , a keyboard controller  240 , and/or an inverter  250 . 
   In ROM table  230 , desired information (i.e. information about brightness of a LCD lamp associated with a plurality of brightness levels) may be stored as a table. In some embodiments, a plurality of tables, each corresponding to ROM table  230  may be stored in association with temperatures around LCD lamp  150 . 
   Temperature sensor  210  may detect ambient temperature around LCD lamp  150 . Temperature sensor  210  may send a detect signal indicative of a detected ambient temperature to microprocessor  220 . Microprocessor  220  may read out, from ROM table  230 , brightness information corresponding to a temperature detected by temperature sensor  210 . Microprocessor  220  may send read-out brightness information to keyboard controller  240 . Microprocessor  220  may receive, from keyboard controller  240 , a brightness select signal inputted from key input unit  100  in accordance with a selection by a user. In response to a brightness select signal, microprocessor  220  may read out, from ROM table  230 , brightness information corresponding to a brightness select signal and send read-out brightness information to keyboard controller  240 . Keyboard controller  240  may generate a voltage and/or current control signal in accordance with brightness information from microprocessor  220 . Keyboard controller  250  may send voltage and/or current control signals to inverter  250 . In response to a voltage and/or current control signal, inverter  250  may apply a corresponding voltage and/or current to LCD lamp  150 . 
   Temperature sensor  210  may measure ambient temperature around LCD lamp  150  in heat collecting part  140 . Ambient temperature around LCD lamp  150  (i.e. an internal temperature of heat collecting part  140 ) may be increased as hot air formed in a system is introduced into heat collecting part  140  in accordance with an operation of a fan. Microprocessor  220  may apply to keyboard controller  240  brightness information which may be determined in accordance with a temperature detected by temperature sensor  210 . 
   Microprocessor  220  may read out, from ROM table  230 , brightness information that may be capable of allowing LCD lamp  150  to maintain a consistent brightness, based on temperatures detected by temperature sensor  210 . Microprocessor  220  may output read-out brightness information to keyboard controller  240 . Accordingly, it may be possible to control LCD lamp  150  to maintain a constant brightness. Accordingly, a lamp can have a prescribed relationship of brightness to temperature. Further, a lamp can have a prescribed relationship with driving current or voltage to brightness. Such exemplary relationships can be described by a function or a model. An exemplary function or model may be determined empirically. 
   Table 1 illustrates a control operation according to embodiments of the present invention. 
   
     
       
             
             
           
             
             
             
             
           
         
             
                 
               TABLE 1 
             
           
           
             
                 
                 
             
             
                 
               Ambient Temperature 
             
           
        
         
             
               Brightness Level 
               25° C. 
               29° C. 
               35° C. 
             
             
                 
             
             
               Level No. 1 (0 V, 1 mV) 
                50 cd/m 2   
                70 cd/m 2   
               100 cd/m 2   
             
             
               . . .  
               . . .  
               . . .  
               . . .  
             
             
               Level No. 6 (2.5 V, 3.5 mV) 
               100 cd/m 2   
               120 cd/m 2   
               150 cd/m 2   
             
             
               . . .  
               . . .  
               . . .  
               . . .  
             
             
               Level No. 9 (4 V, 5 mV) 
               130 cd/m 2   
               150 cd/m 2   
               180 cd/m 2   
             
             
               Level No. 10 (4.5 V. 5.5 mV) 
               140 cd/m 2   
               160 cd/m 2   
               190 cd/m 2   
             
             
               Level No. 11 (5 V, 6 mV) 
               150 cd/m 2   
               170 cd/m 2   
               200 cd/m 2   
             
             
                 
             
           
        
       
     
   
   For example, when brightness of LCD lamp  150  is set to correspond to exemplary level No. 11 at an ambient temperature around LCD lamp  150  of 25° C., LCD lamp  150  exhibits a brightness of 150 cd/M 2 . When ambient temperature around LCD lamp  150  is 35° C., brightness of the LCD lamp  150  is 200 cd/M 2  unless the voltage (5 V) and/or current (6 mA) applied to LCD lamp  150  are appropriately varied. In other words, a system may exhibit a brightness unnecessarily increased by 50 cd/m 2 . However, in accordance with embodiments of the present invention, this problem can be avoided. For instance, when ambient temperature around LCD lamp  150  is increased to 35° C., this temperature increase is detected by temperature sensor  210 . Temperature sensor  210  may then apply a corresponding detect signal to microprocessor  220 . In response to a detect signal, microprocessor  220  may read out from a table associated with an ambient temperature of 35° C., brightness information corresponding to a reference brightness of 150 cd/m 2 . In other words, the brightness information of exemplary level No. 6 (corresponding to 2.5V and 3.5 mV) may be sent (as read-out brightness information) to keyboard controller  240 . In accordance with brightness information of level No. 6, keyboard controller  240  may control inverter  250  to apply a voltage of 2.5 V and a current of 3.5 mA to LCD lamp  150 . Accordingly, voltage and current applied to LCD lamp  150  may be reduced by 2.5 V and 2.5 mA. 
   It may be possible to reduce voltage and current applied to LCD lamp  150  while maintaining brightness of a LCD at the same level by passively or forcedly transferring heat to LCD lamp  150  by use of a thermal coupler (i.e. a fan, a duct, or a thermally conductive material). Accordingly, an increase in ambient temperature around LCD lamp  150  can increase efficiency of a LCD. Additionally, power consumption of a system can be reduced. 
     FIG. 3  is an exemplary flow chart illustrating embodiments associated with a LCD device power control method. Microprocessor  220  may be first initialized in order to normally process power to a LCD (Step  301 ). Microprocessor  220  may then read out, from ROM table  230 , brightness information corresponding to a predetermined ambient temperature (i.e. 25° C.) around LCD lamp 150. Microprocessor  220  may send read-out brightness information to keyboard controller  240 . For example, brightness information may be brightness information of exemplary level No. 11 in Table 1. In accordance with a control operation of keyboard controller  240  (based on the brightness information) inverter  250  may apply to LCD lamp  150  a voltage (i.e. 5 V) and a current (i.e. 6 mA) (Step  302 ). 
   Fan  120  may feed air, heated by heat generated from operation of a system, to heat collecting part  140  arranged around LCD lamp  150  via duct  130 . Accordingly, heat may be transferred to heat collecting part  140 . As a result, an area around LCD lamp  150  may be continuously heated by heat transferred to heat collecting part  140   
   Ambient temperature around LCD lamp  150  may then be detected by temperature sensor  210  which may apply a detect signal indicative of a detected temperature to microprocessor  220  (Step  303 ). Based on a detect signal, microprocessor  220  may determine if ambient temperature around LCD lamp  150  is more than 25° C. (Step  304 ). 
   If it is determined at Step  304  that ambient temperature around LCD lamp  150  is not more than 25° C., microprocessor  220  may determine if there is a brightness select signal inputted by a key input unit (Step  305 ). When it is determined at Step  305  that there is an input brightness select signal, brightness information corresponding to a brightness select signal may be set as a new reference LCD brightness information (Step  306 ). The procedure may then return to Step  302 . Accordingly, microprocessor  220  may read out, from ROM table  230 , brightness information associated with new reference LCD brightness information. Microprocessor  220  may then send read-out brightness information to keyboard controller  240 . In accordance with control operation of keyboard controller  240 , inverter  250  may apply, to the LCD lamp  150 , a voltage and/or current corresponding to newly-set brightness information. Subsequently, a procedure may proceed to Step  303  at which a detected signal indicative of ambient temperature around LCD lamp  150  may be applied to the microprocessor  220 . These steps may be repeatedly executed. 
   If it is determined at Step  305  that there is no input brightness select signal, microprocessor  220  may maintain control operation adapted to apply, to LCD lamp  150 , power corresponding to a detected temperature range of not more than 25° C. (i.e. a voltage of 5V and a current of 6 mA) in accordance with operation of inverter  250  (Step  307 ). Thereafter, the procedure may be returned to Step  303 , at which a detected signal indicative of ambient temperature around LCD lamp  150  is applied to microprocessor  220 . These steps may be repeatedly executed. When it is determined at Step  304  that ambient temperature around LCD lamp  150  is more than 25° C., microprocessor  220  may determine if ambient temperature around LCD lamp  150  is not more than 29° C. (Step  308 ). 
   If it is determined (at Step  308 ) that ambient temperature around LCD lamp  150  is not more than 29° C., microprocessor  220  may determine whether or not there is a brightness select signal input by a key input unit (Step  309 ). If it is determined at Step  309  that there is an input brightness select signal, brightness information corresponding to a brightness select signal is set as a new reference LCD brightness information (Step  306 ). The procedure may then return to Step  302 . Microprocessor  220  may read out, from the ROM table  230 , brightness information associated with new reference LCD brightness information. Microprocessor may send read-out brightness information to keyboard controller  240 . In accordance with a control operation of keyboard controller  240 , inverter  250  may apply to LCD lamp  150  a voltage and/or current corresponding to newly-set brightness information. Subsequently, the procedure may proceed to Step  303  at which a detected signal indicative of ambient temperature around LCD lamp  150  may be applied to microprocessor  220 . These steps may be repeatedly executed. 
   If it is determined at Step  309  that there is no input brightness select signal, microprocessor  220  may read out, from the ROM table  230 , brightness information corresponding to a detected temperature range of mote than 25° C., but not less than 29° C. Microprocessor  220  may send read-out brightness information to keyboard controller  240 . Under control of keyboard controller  240 , based on brightness information, inverter  250  may apply to LCD lamp  150  power corresponding to the brightness information (i.e. a voltage of 4V and a current of 5 mA) (Step  310 ). The procedure may then return to Step  303 , at which a detected signal indicative of ambient temperature around LCD lamp  150  is applied to microprocessor  220 . These steps may be repeatedly executed. 
   If it is determined at Step  308  that ambient temperature around LCD lamp  150  is more than 29° C., microprocessor  220  may determine if there is a brightness select signal input to key input unit (Step  311 ). When it is determined at Step  311  that there is an input brightness select signal, the procedure may returned to Step  306  at which brightness information corresponding to a brightness select signal is set as new reference LCD brightness information. The procedure may then return to Step  302 . Microprocessor  220  may then read out from ROM table  230  brightness information associated with new reference LCD brightness information. Microprocessor  220  may sends read-out brightness information to keyboard controller  240 . In accordance with a control operation of keyboard controller  240 , inverter  250  may apply to LCD lamp  150  a voltage and/or a current corresponding to newly-set brightness information. The procedure may proceed to Step  303 , at which a detected signal indicative of ambient temperature around LCD lamp  150  is applied to microprocessor  220 . These steps may be repeatedly executed. 
   If it is determined at Step  311  that there is no input brightness select signal, microprocessor  220  may read out from ROM table  230  brightness information corresponding to a detected temperature range of more than 29° C. Microprocessor  220  may then send read-out brightness information to keyboard controller  240 . Under control of keyboard controller  240 , based on brightness information, inverter  250  may apply to LCD lamp  150  power corresponding to the brightness information (i.e. a voltage of 2.5V and a current of 3.5 mA) (Step  312 ). The procedure may then return to Step  303  at which a detected signal indicative of ambient temperature around a LCD lamp  150  is applied to microprocessor  220 . These steps may be repeatedly executed. 
   In some embodiments illustrated in  FIG. 3 , ambient temperature around a LCD lamp is divided into three temperature ranges. For example, a first range of not more than 25° C., a second range of more than 25° C. and less than 29° C., and a third range of more than 29° C. in order to appropriately vary voltage and current which may be applied to a LCD lamp. However, it may be desirable that ambient temperature around a LCD lamp is divided into more temperature ranges for better resolution of brightness control. 
   As apparent from the above description, embodiments of the present invention provides an apparatus and method for controlling power of a LCD, which can reduce power consumed by the LCD while maintaining brightness of the LCD. Embodiments of the present invention provide an apparatus and method for controlling power of a LCD device, in which power to be applied to a LCD lamp is varied in accordance with ambient temperature of the LCD lamp, so that it is possible to reduce the power consumed by the LCD lamp while maintaining the brightness of the LCD lamp corresponding to a designed reference value. 
   Embodiments of the present invention provide a LCD device power control apparatus in which heat generated from heat-generating internal system elements is transferred around a LCD lamp via a duct to increase the ambient temperature around the LCD lamp, so that it is possible to reduce the power consumed by the LCD lamp while maintaining the brightness of the LCD lamp corresponding to a designed reference value. 
   Embodiments provide an apparatus for controlling power of a liquid crystal display (LCD) device comprising: a LCD lamp; temperature sensing means for sensing an ambient temperature around the LCD lamp; and control means for performing a control operation for varying a voltage and/or current, to be applied to the LCD lamp, in proportion to the ambient temperature sensed by the temperature sensing means. 
   Embodiments provides an apparatus for controlling power of a liquid crystal display (LCD) device comprising: an element generating heat in accordance with a system operation thereof; heat transfer means for transferring the heat generated from the heat-generating element to a region around a LCD lamp; and control means for performing a control operation for supplying, to the LCD lamp, a brightness adjustment voltage and/or current proportional to an ambient temperature around the LCD lamp increased in accordance with the transferred heat by an inverter. 
   Embodiments provide a method for controlling power of a liquid crystal display (LCD) device comprising: (a) supplying a voltage and/or current to a LCD lamp, based on a predetermined temperature, and receiving information about a temperature measured around the LCD lamp; (b) identifying, from a table, supply power information associated with the LCD lamp while corresponding to the received temperature information; and (c) varying the voltage and/or current, to be supplied to the LCD lamp at the step (a), based on the identified supply power information, and supplying the varied voltage and/or current to the LCD lamp. 
   Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.