Patent Publication Number: US-7911217-B2

Title: Liquid crystal display, connector and method of testing the liquid crystal display

Description:
This application claims priority to Korean Patent Application No. 10-2006-0133053, filed on Dec. 22, 2006, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display (“LCD”), a connector for testing the liquid crystal display and a method of testing the liquid crystal display. More specifically, the present invention relates to a liquid crystal display, a connector for testing the liquid crystal display and a method of testing the liquid crystal display which do not require a separate apparatus for conducting a high voltage stress test of the liquid crystal display. 
     2. Description of the Related Art 
     LCDs include a first display panel including pixel electrodes, a second display panel including a common electrode, a liquid crystal layer having dielectric anisotropy interposed between the first display panel and the second display panel, a gate driver which drives a plurality of gate lines, a data driver which outputs data signals, and a driver which generates and outputs a reference grayscale voltage and a gate turn-on/off voltage. 
     After LCDs are manufactured they are tested using a separate testing apparatus to detect defective LCDs. A high voltage stress (“HVS”) test is a method for testing the operation of an LCD in which a higher than rated voltage is applied to the LCD. For an HVS test, a separate HVS testing apparatus for providing a high voltage is used, and LCDs are electrically connected to the HVS testing apparatus in order to perform the test. 
     According to a conventional HVS testing technique, a separate HVS testing apparatus for providing a high voltage is required, thereby increasing manufacturing costs of LCDs, and requiring a complicated testing procedure after an LCD is manufactured. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a liquid crystal display capable of self-generating a high voltage for a high voltage stress (“HVS”) test. 
     The present invention also provides a connector for testing a liquid crystal display capable of self-generating a high voltage for a HVS test. 
     The present invention also provides a method of testing a liquid crystal display capable of self-generating a high voltage for a HVS test. 
     These and other aspects, features, and advantages of the present invention will be described in or be apparent from the following description of exemplary embodiments thereof. 
     According to an exemplary embodiment of the present invention, a liquid crystal display includes an internal connector including an input pin which receives a power supply voltage from an outside source, a no-connect (“NC”) pin and a ground pin. The liquid crystal display further includes a power supply unit connected to the NC pin and to the ground pin. The power supply unit receives the power supply voltage and outputs a gate-on voltage and a gate-off voltage whose levels are adjusted according to whether there is an electrical connection or disconnection between the NC pin and the ground pin. The liquid crystal display further includes a gate driving unit which receives the gate-on voltage and the gate-off voltage and outputs a gate signal, and a liquid crystal panel receiving the gate signal and comprising a plurality of pixels displaying images in response to the gate signal. 
     The gate-on voltage rises and the gate-off voltage falls when the NC pin is electrically connected to the ground pin. 
     The liquid crystal display is tested when the NC pin is electrically connected to the ground pin. 
     The liquid crystal display operates normally when the NC pin is electrically disconnected from the ground pin, and the gate-on voltage is lower and the gate-off voltage is higher compared to when the NC pin is electrically connected to the ground pin. 
     The power supply unit includes a boosting portion which boosts a first input voltage and outputs a driving voltage and a pulse signal whose voltage levels vary according to a feedback voltage, a feedback voltage generating portion which divides the driving voltage to generate the feedback voltage, a gate-on voltage generating portion which outputs the gate-on voltage by shifting the driving voltage by the voltage level of the pulse signal and a gate-off voltage generating portion which outputs the gate-off voltage by shifting a second input voltage by the voltage level of the pulse signal. 
     The NC pin is electrically connected to the ground pin, the feedback voltage falls, the gate-on voltage rises, and the gate-off voltage falls. 
     The feedback voltage generating portion includes a first resistor connected between a first terminal which supplies the driving voltage and a second terminal which supplies the feedback voltage and a second resistor connected between the second terminal which supplies the feedback voltage and a third terminal which is connected to a ground voltage. 
     The liquid crystal display further includes a connecting member which electrically connects the NC pin and the ground pin when the liquid crystal display is tested. 
     According to another exemplary embodiment of the present invention, a connector for testing a liquid crystal display includes a transmitting unit which receives a power supply voltage, a ground voltage, and a testing image signal from an outside source and transmits the received power supply voltage, the ground voltage, and the testing image signal to the liquid crystal display, and a connecting unit which electrically connects an NC pin and a ground pin in an internal connector of the liquid crystal display which receives the power supply voltage, the ground voltage, and the testing image signal. 
     The transmitting unit includes input terminals which receive the power supply voltage, the ground voltage and the testing image signal, and output terminals which output the received power supply voltage, the ground voltage and the testing image signal. The connecting unit includes a first connecting terminal connected to the NC pin and a second connecting terminal connected to the ground pin, and the first connecting terminal is electrically connected to the second connecting terminal. 
     When the liquid crystal display is tested, the connector is connected to the internal connector of the liquid crystal display and transmits the power supply voltage, the ground voltage and the testing image signal to the liquid crystal display. 
     According to yet another exemplary embodiment of the present invention, a method of testing a liquid crystal display includes providing a liquid crystal display to be tested. 
     The liquid crystal display includes an internal connector having an input pin receiving a power supply voltage from an external source, an NC pin and a ground pin. The liquid crystal display further includes a power supply unit connected to the NC pin and the ground pin, and the power supply unit receives the power supply voltage and outputs a gate-on voltage and a gate-off voltage whose levels are adjusted according to whether there is an electrical connection or disconnection between the NC pin and the ground pin. The NC pin is electrically connected to the ground pin. 
     The gate-on voltage rises and the gate-off voltage falls when the NC pin is electrically connected to the ground pin. 
     The electrical connecting of the NC pin and the ground pin includes connecting a connector to the internal connector. The connector includes a transmitting unit which receives a power supply voltage, a ground voltage, and a testing image signal from an outside source and transmits the received power supply voltage, the ground voltage and the testing image signal to the liquid crystal display. The connector further includes a connecting unit which electrically connects an NC pin and a ground pin in an internal connector of the liquid crystal display which receives the power supply voltage, the ground voltage and the testing image signal. 
     The power supply unit includes a boosting portion boosting a first input voltage and outputting a driving voltage and a pulse signal whose voltage levels vary according to a feedback voltage, a feedback voltage generating portion dividing the driving voltage and generating the feedback voltage, a gate-on voltage generating portion outputting the gate-on voltage by shifting the driving voltage by the voltage level of the pulse signal and a gate-off voltage generating portion outputting the gate-off voltage by shifting a second input voltage by the voltage level of the pulse signal. The electrical connecting of the NC pin and the ground pin includes causing the feedback voltage to fall. 
     The feedback voltage generating portion includes a first resistor connected between a first terminal supplying the driving voltage and a second terminal supplying the feedback voltage and a second resistor connected between the second terminal supplying the feedback voltage and a third terminal which is connected to a ground voltage. The electrical connecting of the NC pin and the ground pin includes causing an equivalent resistance between the feedback voltage and the ground voltage to fall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the present invention will become more apparent by describing in further detail exemplary embodiments thereof with reference to the attached drawings, in which: 
         FIG. 1  is a block diagram of a liquid crystal display (“LCD”) according to an exemplary embodiment of the present invention; 
         FIG. 2  is an equivalent circuit diagram of one pixel of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention; 
         FIG. 3  is a plan view of a connector of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention; 
         FIG. 4  is a graph which illustrates levels of voltages supplied from a power supply unit of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention; 
         FIG. 5  is a block diagram of a power supply unit of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention; 
         FIG. 6  is a schematic circuit view of a boosting portion and a feedback voltage generating portion of the power supply unit of  FIG. 5  according to an exemplary embodiment of the present invention; 
         FIG. 7  is a block diagram of a pulse width modulation signal generator of the boosting portion of the power supply unit of  FIG. 6  according to an exemplary embodiment of the present invention; 
         FIG. 8  is a schematic circuit view of a gate-on voltage generating portion and a gate-off voltage generating portion of the power supply unit of  FIG. 5  according to an exemplary embodiment of the present invention; and 
         FIG. 9  is a block diagram of a connector for testing an LCD according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including,” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components and/or groups thereof. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top” may be used herein to describe one element&#39;s relationship to other elements as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on the “upper” side of the other elements. The exemplary term “lower” can, therefore, encompass both an orientation of “lower” and “upper,” depending upon the particular orientation of the figure. Similarly, if the device in one of the figures were turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning which is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Exemplary embodiments of the present invention are described herein with reference to cross section illustrations which are schematic illustrations of idealized embodiments of the present invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes which result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles which are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present invention. 
     A liquid crystal display (“LCD”) according to an exemplary embodiment of the present invention and a method of testing the same will now be described more fully with reference to the accompanying drawings.  FIG. 1  is a block diagram of an LCD according to an exemplary embodiment of the present invention,  FIG. 2  is an equivalent circuit diagram of one pixel of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention,  FIG. 3  is a plan view of a connector of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention, and  FIG. 4  is a graph which illustrates levels of voltages supplied from a power supply unit of the LCD of  FIG. 1  according to an exemplary embodiment of the present invention. 
     For purposes of clarification herein, voltages supplied during a normal operation of the power supply unit of the LCD from voltages supplied during a test operation of the power supply unit of the LCD, the voltages supplied during the test operation are denoted in parentheses. For example, a normally-applied gate-off voltage designated Voff and a testing gate-off voltage TVoff will be denoted as Voff and Tvoff, respectively, herein. 
     Referring to  FIG. 1 , an LCD  10  according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly  300 , a gate driving unit  400 , a data driving unit  500 , a signal controlling unit  600 , a power supply unit  700 , a grayscale voltage generating unit  800  and an internal connector  750 . 
     The liquid crystal panel assembly  300  includes a plurality of display signal lines G 1 -G n  and D 1 -D m , and a plurality of pixels PX which are connected to the display signal lines G 1 -G n  and D 1 -D m  and arranged in a matrix form, as shown in  FIG. 1 . 
     The display signal lines include a plurality of gate lines G 1 -G n  which transmit a gate signal, and a plurality of data signals D 1 -D m  which transmit a data signal. The gate lines G 1 -G n  substantially extend in a transverse direction and are parallel to one another, while the data lines D 1 -D m  substantially extend in a longitudinal direction and are parallel to one another. 
     Referring to  FIG. 2 , each pixel PX of an LCD according to an exemplary embodiment of the present invention includes a first display panel  100 , a second display panel  200  and a liquid crystal layer  150  which is interposed between the first display panel  100  and the second display panel  200 . A color filter CF may be provided on an area of a common electrode CE of the second display panel  200  to face a pixel electrode PE of the first display panel  100 . The pixel PX, which is connected to a corresponding gate line and a corresponding data line, e.g., ith gate line Gi (i=1−n) and jth data line Dj (j=1−m), includes a first switching device Q 1 , and a liquid crystal capacitor C lc  and a storage capacitor C st  connected thereto. In alternative exemplary embodiments, the storage capacitor C st  may be eliminated. 
     Referring back to  FIG. 1 , the internal connector  750  is connected to an outside graphic controller (not shown) from which it receives a plurality of signals, and transmits the plurality of received signals to the LCD  10 . For example, the internal connector  750  receives red, green and blue image signals R, G and B, respectively, and input control signals which control display of the image signals R, G and B, and transmits the received image signals R, G and B to the signal controlling unit  600 . Examples of the input control signals include a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a main clock signal MCLK and a data enable signal DE, but are not limited thereto. Moreover, the internal connector  750  receives a power supply voltage Vdd from an outside source (not shown) and supplies the power supply voltage Vdd to the power supply unit  700 . The internal connector  750  includes input pins which receive and transmit the image signals R, G and B as described above, power supply voltage pin VDD which receives and transmits the power supply voltage Vdd and ground pin GND which receives a ground voltage Vg, and no-connect pin NC. 
     Referring to  FIG. 3 , the internal connector  750  may be a 30-pin connector standardized by, e.g., but is not limited thereto, the Panel Standardization Working Group (“PSWG”). In one exemplary embodiment of the present invention, a connector standardized by the PSWG includes first through third pins which receive the power supply voltages Vdd, fourth through sixth pins which are no-connect pins NC, seventh, fourteenth, seventeenth, and twenty-fourth pins which are ground pins GND which receive the ground voltage Vg and the remaining pins are pins which receive image signals and clock signals as indicated in  FIG. 3 . More specifically, with respect to “RXO” and “RXE” as shown in  FIG. 3 , “RX”, “O” and “E” are abbreviations for Receiver, Odd, and Even, respectively and the internal connector  750  includes RXO pins and RXE pins to transmit data in a dual transmission method to increase a bandwidth of the image and clock signals. For example, the image signals are input to RXO 0−, RXO 0+, RXO 1−, RXO 1+, RXO 2−, RXO 2+, RXO 3−, RXO 3+, RXE 0−, RXE 0+, RXE 1−, RXE 1+, RXE 2−, RXE 2+, RXE 3− and RXE 3+, and the clock signals are input to RXO C−, RXO C+, RXE C− and RXE C+. In an exemplary embodiment of the present invention, the no-connect pins NC, the ground pins GND and the power supply voltage pins VDD of the internal connector  750  are connected to the power supply unit  700  ( FIG. 1 ). 
     Referring again to  FIG. 1 , the gate driving unit  400  receives a gate control signal CONT 1  from the signal controlling unit  600  and applies gate signals to gate lines G 1 -G n . The gate signals include a gate-on voltage Von and a gate-off voltage Voff supplied from the power supply unit  700  during normal operation. During testing, the gate signals include a testing gate-on voltage TVon and a testing gate-off voltage TVoff. In an exemplary embodiment, the testing gate-on voltage TVon is higher than the gate-on voltage Von for normal operation, and the testing gate-off voltage TVoff is lower than the gate-off voltage Voff for normal operation. 
     The gate control signal CONT 1  is a signal for controlling the operation of the gate driving unit  400 , and may include a vertical starting signal (not shown) for initiating operation of the gate driving unit  400 , a gate clock signal for controlling the output time of the gate-on voltage Von and an output enable signal (not shown) for determining the pulse width of the gate-on voltage Von, for example, but is not limited thereto. 
     The grayscale voltage generating unit  800  divides a driving voltage AVDD supplied from the power supply unit  700  and supplies a plurality of grayscale voltages GV to the data driving unit  500  during normal operation, and divides a testing driving voltage TAVDD and supplies a plurality of testing grayscale voltages TGV to the data driving unit  500  during testing. 
     The data driving unit  500  receives a data control signal CONT 2  and a testing image signal TDAT, described in further detail later, from the signal controlling unit  600 . The data driving unit  500  operates in response to the data control signal CONT 2  to select image data voltages (not shown) corresponding to image signals (not shown) among the grayscale voltages GV or the testing grayscale voltages TGV received from the grayscale voltage generating unit  800 , and apply the selected image data voltages to the data lines D 1 -D m . Further, the data control signal CONT 2  is a signal for controlling the operation of the data driving unit  500  and may include a horizontal starting signal (not shown) for initiating the operation of the data driving unit  500  or an output control signal (not shown) for controlling the output of the data voltages, for example, but is not limited thereto. 
     In an exemplary embodiment of the present invention, the gate driving unit  400  and/or the data driving unit  500  may be directly mounted on the liquid crystal panel assembly  300  in the form of a plurality of driving integrated circuit (“IC”) chips. In alternative exemplary embodiments, the gate driving unit  400  or the data driving unit  500  may be mounted on a flexible printed circuit film (not shown) and made into a tape carrier package, and the tape carrier package may be attached to the liquid crystal panel assembly  300 , or the gate driving unit  400  or the data driving unit  500  may be integrated on the liquid crystal panel assembly  300 , together with the display signal lines G 1 -G n  and D 1 -D m  and switching devices Q 1  ( FIG. 2 ), for example, but are not limited thereto. 
     The signal controlling unit  600  receives the image signals R, G and B and the input control signals for controlling the display of the image signals R, G and B from the internal connector  750 , and generates and supplies the gate control signal CONT 1  and the data control signal CONT 2  to the gate driving unit  400  and the data driving unit  500 , respectively. 
     The power supply unit  700  receives the power supply voltage Vdd from the internal connector  750  and supplies voltages required to operate the LCD  10  such as the gate-on voltage Von, a gate-off voltage Voff and a common voltage Vcom, for example, but is not limited thereto. More specifically, referring to  FIGS. 3 and 4  together with  FIG. 1 , the power supply unit  700  supplies the driving voltage AVDD, the gate-on voltage Von, and the gate-off voltage Voff during normal operation. During testing, the power supply unit  700  supplies the testing driving voltage TAVDD and the testing gate-on voltage TVon, which are higher than the driving voltage AVDD and the gate-on voltage Von during normal operation, respectively, and the testing gate-off voltage TVoff which is lower than the gate-off voltage Voff for normal operation. During testing, the no-connect pin NC is electrically connected to the ground pin GND in the internal connector  750 . During normal operation, the no-connect pin NC is electrically disconnected from the ground pin GND in the internal connector  750 . For example, depending on whether there is an electrical connection or disconnection between the no-connect pin NC and the ground pin GND in the internal connector  750 , the power supply unit  700  supplies either the driving voltage AVDD, the gate-on voltage Von, and the gate-off voltage Voff, or the testing driving voltage TAVDD and the testing gate-on voltage TVon, which are higher than the driving voltage AVDD and the gate-on voltage Von, respectively, and the testing gate-off voltage TVoff, which is lower than the gate-off voltage Voff for normal operation. A more detailed description thereof will be described below. 
       FIG. 5  is a block diagram of the power supply unit  700  of  FIG. 1 ,  FIG. 6  is a schematic circuit view of a boosting portion and a feedback voltage generating portion of the power supply unit  700  of  FIG. 5  according to an exemplary embodiment of the present invention,  FIG. 7  is a block diagram of a pulse width modulation signal generator of  FIG. 6  according to an exemplary embodiment of the present invention, and  FIG. 8  is a schematic circuit view of a gate-on voltage generating portion and a gate-off voltage generating portion of the power supply unit of  FIG. 5  according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , the power supply unit  700  includes a boosting portion  720 , a gate-on voltage generating portion  730 , a gate-off voltage generating portion  740 , and a feedback voltage generating portion  710 . 
     The power supply voltage pin VDD of the internal connector  750  is connected to the boosting portion  720 , the no-connect pin NC is connected to the feedback voltage generating portion  710 , and the ground pin GND is connected to the gate-off voltage generating portion  740 . 
     The boosting portion  720  boosts the power supply voltage Vdd and outputs a driving voltage AVDD and a pulse signal PULSE whose voltage levels vary according to a feedback voltage FB. In an exemplary embodiment, when the feedback voltage FB falls, the driving voltage AVDD and the voltage of the pulse signal PULSE rise; conversely, when the feedback voltage FB rises, the driving voltage AVDD and the voltage of the pulse signal PULSE fall. Further, when the no-connect pin NC and the ground pin GND are electrically connected to each other in the internal connector  750 , the feedback voltage generating portion  710  reduces the feedback voltage FB. Put another way, when the no-connect pin NC is electrically connected to the ground pin GND, the feedback voltage generating portion  710  supplies a lower feedback voltage FB to the boosting portion  720 , compared with when the no-connect pin NC is electrically disconnected from the ground pin GND. In addition, the boosting portion  720  outputs a testing driving voltage TAVDD which is higher than the driving voltage AVDD for normal operation, and a pulse signal PULSE which is a higher voltage than the pulse signal PULSE for normal operation. The boosting portion  720  and the feedback voltage generating portion  710  will be described in further detail later with reference to  FIGS. 6 and 7 . 
     During normal operation, the gate-on voltage generating portion  730  outputs a gate-on voltage Von obtained by shifting the driving voltage AVDD ( FIG. 4 ) by a value approximately equal to the voltage of the pulse signal PULSE. During testing, e.g., when the no-connect pin NC is electrically connected to the ground pin GND, the gate-on voltage generating portion  730  outputs a testing gate-on voltage TVon. The gate-on voltage generating portion  730  will be described in further detail later with reference to  FIG. 8 . 
     During normal operation, the gate-off voltage generating portion  740  outputs a gate-off voltage Voff obtained by shifting a ground voltage by a value approximately equal to the voltage of the pulse signal PULSE ( FIG. 4 ). During testing, e.g., when the no-connect pin NC is electrically connected to the ground pin GND, the gate-off voltage generating portion  740  outputs a testing gate-off voltage TVoff. The gate-off voltage generating portion  740  will be described in further detail later with reference to  FIG. 8 . 
     The boosting portion  720  and the feedback voltage generating portion  710  will now be described in further detail with reference to  FIG. 6 . 
     Referring to  FIGS. 5 and 6 , with respect to the feedback voltage generating portion  710 , the feedback voltage generating portion  710  includes a first resistor R 1  and a second resistor R 2 , which are used for dividing the driving voltage AVDD, and an optional resistor R_OP. The first resistor R 1  is connected between the driving voltage AVDD and the feedback voltage FB, and the second resistor R 2  is connected between the feedback voltage FB and the ground voltage Vg. A terminal of the optional resistor R_OP is connected to the feedback voltage FB, and the other terminal is connected to the no-connect pin NC of the internal connector  750 . 
     When the no-connect pin NC is electrically disconnected from the ground pin GND, the optional resistor R_OP is floating, and the feedback voltage FB is set to a voltage level obtained by dividing the driving voltage AVDD by the first resistor R 1  and the second resistor R 2 . For example, when the no-connect pin NC are electrically disconnected from the ground pin GND, the boosting portion  720  outputs the driving voltage AVDD for normal operation. 
     During testing, the no-connect pin NC of the internal connector  750  is electrically connected to the ground pin GND of the internal connector  750  by a conductive connecting member CM. Therefore, the optional resistor R_OP is connected to the ground voltage. Since the optional resistor R_OP is connected in electrical parallel to the second resistor R 2 , the equivalent resistance between the feedback voltage FB and the ground voltage decreases, causing the feedback voltage FB to fall. When the feedback voltage FB falls, the boosting portion  720  outputs the testing driving voltage TAVDD, which is higher than the driving voltage AVDD for normal operation, and a pulse signal PULSE of a higher voltage than the pulse signal PULSE for normal operation. Therefore, the power supply unit  700  supplies the testing driving voltage TAVDD and the testing gate-on voltage TVon which are higher than the driving voltage AVDD and the gate-on voltage Von for normal operation, and the testing gate-off voltage TVoff which is lower than the gate-off voltage Voff for normal operation. In an exemplary embodiment, the no-connect pin NC and the ground pin GND are electrically connected through the conductive connecting member CM, which is a cable, for example, but is not limited thereto. 
     The boosting portion  720  may be a boost converter as illustrated in  FIG. 6  and include an inductor L which receives the power supply voltage Vdd from the internal connector  750 , a first diode D 1  including an anode connected to the inductor L and a cathode connected to the first resistor R 1 , a first capacitor C 1  connected between the first diode D 1  and the ground voltage, and a pulse width modulation (“PWM”) signal generator  725  connected to a gate terminal of a switching device Q 2 . In an exemplary embodiment, the boost converter shown in  FIG. 6  is an example of the boosting portion  720 , but alternative exemplary embodiments are not limited thereto. For example, the boosting portion  720  may be selected from other kinds of converters. Furthermore, in alternative exemplary embodiments, a lower voltage than the power supply voltage Vdd shown in  FIG. 6  may be applied to the boosting portion  720  through a voltage divider (not shown). 
     With respect to the operation of the boosting portion  720 , when a PWM signal PWM output from the PWM signal generator  725  is at a high level state, the switching device Q 2  is turned on, and thus, a current I L  flowing in the inductor L increases in proportion to the power supply voltage Vdd according to current/voltage characteristics of the inductor L. 
     When the PWM signal PWM is in a low level state, the switching device Q 2  is turned off. Thus, the current I L  flowing in the inductor L passes through the first diode D 1 , and a voltage is charged in the first capacitor C 1  according to the current/voltage characteristics of the first capacitor C 1 . As a result, the power supply voltage Vdd is boosted to a predetermined voltage, and the boosted voltage is output through the power supply unit  700 . Here, the duty ratio of the PWM signal PWM varies according to the feedback voltage FB, and the amount of the current I L  flowing in the inductor L varies according to the duty ratio of the PWM signal PWM. Accordingly, the driving voltage AVDD and the voltage of the pulse signal PULSE rise or fall. 
     When the no-connect pin NC is electrically connected to the ground pin GND, the boosting portion  720  outputs a pulse signal PULSE of a higher voltage than the pulse signal PULSE for normal operation, and the testing driving voltage TAVDD which is higher than the driving voltage AVDD for normal operation. 
     The operation of the PWM signal generator  725  outputting the PWM signal PWM having a different duty ratio according to the feedback voltage FB will now be described with reference to  FIGS. 6 and 7 . An oscillator  726  generates a reference clock signal RCLK which has a constant frequency. A comparator  727  compares the reference clock signal RCLK generated from the oscillator  726  and the feedback voltage FB. When the feedback voltage FB is higher than the voltage of the reference clock signal RCLK, the PMW signal generator  725  generates the PWM signal PWM of a high voltage. When the feedback voltage FB is lower than the voltage of the reference clock signal RCLK, the PMW signal generator  725  generates the PWM signal PWM of a low voltage. Since the frequency of the reference clock signal RCLK is constant, the duty ratio of the PWM signal PWM varies only according to the feedback voltage FB. The PWM signal generator  725  is not limited to the above-illustrated example, and may be a different circuit generating a PWM signal PWM having a different duty ratio according to the feedback voltage FB in an alternative exemplary embodiment. 
     The gate-on voltage generating portion  730  and the gate-off voltage generating portion  740  used as charge-pumping circuits will now be described with reference to  FIG. 8 . 
     Referring to  FIGS. 5 and 8 , the gate-on voltage generating portion  730  includes second and third diodes D 2  and D 3  and second and third capacitors C 2  and C 3 . The driving voltage AVDD for normal operation or the testing driving voltage TAVDD for testing is applied to an anode of the second diode D 2 , and a cathode of the second diode D 2  is connected to a first node N 1 . The second capacitor C 2  is connected between the first node N 1  and a second node N 2  which receives the pulse signal PULSE. An anode of the third diode D 3  is connected to the first node N 1 , and a cathode of the third diode D 3  outputs the gate-on voltage Von for normal operation or the testing gate-on voltage TVon for testing. The third capacitor C 3  is connected between the anode of the second diode D 2  and the cathode of the third diode D 3 . However, the gate-on voltage generating portion  730  is not limited to the exemplary embodiment described herein, and may include different combinations and/or numbers of diodes and/or capacitors. 
     With respect to the operation of the gate-on voltage generating portion  730 , when the pulse signal PULSE is applied to the second capacitor C 2 , the first node N 1  outputs a voltage which is higher than the driving voltage AVDD by an approximate value of the voltage of the pulse signal PULSE during normal operation, and a pulse of a voltage which is higher than the testing driving voltage TAVDD by an approximate value of the pulse signal PULSE during testing. The third diode D 3  and the third capacitor C 3  clamp the voltage at the first node N 1  to output the gate-on voltage Von or the testing gate-on voltage TVon. For example, the gate-on voltage Von for normal operation is a DC voltage shifted from the driving voltage AVDD by approximately the voltage of the pulse signal PULSE, and the testing gate-on voltage TVon is a DC voltage shifted from the testing driving voltage TAVDD by approximately the voltage of the pulse signal PULSE. 
     The gate-off voltage generating portion  740  includes fourth and fifth diodes D 4  and D 5  and fourth and fifth capacitors C 4  and C 5 . A cathode of the fourth diode D 4  is connected to the ground voltage, and an anode of the fourth diode D 4  is connected to a third node N 3 . The fourth capacitor C 4  is connected between the third node N 3  and the second node N 2  which receives the pulse signal PULSE. A cathode of the fifth diode D 5  is connected to the third node N 3 , and the fifth capacitor C 5  is connected between the cathode of the fourth diode D 4  and the anode of the fifth diode D 5 . The anode of the fifth diode D 5  outputs the gate-off voltage Voff or the testing gate-off voltage TVoff. The gate-off voltage generating portion  740  is not limited to the exemplary embodiment described herein, and may include different combinations and/or numbers of diodes and/or capacitors. 
     With respect to the operation of the gate-off voltage generating portion  740 , when the pulse signal PULSE is applied to the fourth capacitor C 4 , the third node N 3  outputs a voltage which is lower than the ground voltage and is obtained using the voltage of the pulse signal PULSE. Here, with respect to the voltage of the pulse signal PULSE, the voltage of the pulse signal PULSE when the no-connect pin NC is electrically connected to the ground pin GND is higher than that when the no-connect pin NC is electrically disconnected from the ground pin GND, as described above. The fifth diode D 5  and the fifth capacitor C 5  clamp the voltage at the third node N 3  to output the gate-off voltage Voff or the testing gate-off voltage TVoff. For example, the gate-off voltage Voff or the testing gate-off voltage TVoff is a DC voltage shifted from the ground voltage by approximately the voltage of the pulse signal PULSE. 
     In summary, when no-connect pin NC is electrically connected to the ground pin GND, the power supply unit  700  ( FIG. 1 ) supplies a testing driving voltage TAVdd, a testing gate-on voltage TVon, and a testing gate-off voltage TVoff. Therefore, since the power supply unit  700  itself generates the testing voltages described above, there is no need for a separate external HVS testing apparatus to test the LCD  10  according to exemplary embodiments of the present invention. 
     A connector for testing an LCD according to an exemplary embodiment of the present invention will be described in further detail hereinafter with reference to  FIG. 9 .  FIG. 9  is a block diagram of a connector for testing an LCD according to an exemplary embodiment of the present invention. For convenience of explanation, common components an LCD having the same functions as described above in reference to previous exemplary embodiments of the present invention are identified by the same reference numerals as in  FIG. 1 , and descriptions of these components will not be repeated. 
     Referring to  FIG. 9 , a connector includes an external signal supply unit  900  which supplies testing signals R, G, B, DE, Hsync, Vsync and MCLK; an LCD  10  to be tested; and a testing connector  760  transmitting the testing signals R, G, B, DE, Hsync, Vsync and MCLK received from the external signal supply unit  900  to an LCD  10 . 
     In order to test the LCD  10 , the testing connector  760  is connected to an internal connector  750  of the LCD  10  and to the external signal supply unit  900 . 
     The external signal supply unit  900  supplies testing image signals R, G, and B, control signals DE, Hsync, Vsync and MCLK., and a power supply voltage Vdd (not shown). In an exemplary embodiment, the testing image signals R, G and B may be patterned signals for testing a display quality of the LCD  10 . 
     The testing connector  760  includes input terminals  762 , output terminals  764  and a connecting portion  766 . The input terminals  762  receive the testing signals R, G, B, DE, Hsync, Vsync and MCLK from the external signal supply unit  900 , and output terminals  764  transmit the received signals to the LCD  10 . The connecting portion  766  includes a first connecting terminal P 1  connected to a no-connect pin NC of the internal connector  750  of the LCD  10  and a second connecting terminal P 2  connected to a ground pin GND. In  FIG. 9 , the first connecting terminal P 1  is shown as being electrically connected to the second connecting terminal P 2 . The testing connector  760  supplies the testing signals R, G, B, DE, Hsync, Vsync and MCLK to the internal connector  750  of the LCD  10 . In an exemplary embodiment, the testing connector  760  may receive the power supply voltage Vdd (not shown) and the ground voltage (not shown) from the external signal supply unit  900 , but is not limited thereto, and supply the received voltages to the internal connector  750 . 
     When the internal connector  750  is connected to the testing connector  760 , the no-connect pin NC is electrically connected to the ground pin GND. Thus, a power supply unit  700  generates a testing driving voltage TAVDD, a testing gate-on voltage TVon, and a testing gate-off voltage TVoff, as described in greater above. 
     A signal controlling unit  600  supplies a testing image signal TDAT to a data driving unit  500 , and the data driving unit  500  supplies an image data voltage corresponding to the testing image signal TDAT among the testing grayscale voltages TGV to a liquid crystal panel  300 . 
     In summary, in response to the operation of the testing connector  760 , the power supply unit  700  of the LCD  10  itself generates high voltages for testing, e.g., the testing driving voltage TAVDD, the testing gate-on voltage TVon, and the testing gate-off voltage TVoff. The LCD  10  is tested using the testing voltages TAVDD, TVon, and TVoff, and the testing image signals R, G and B supplied from the external signal supply unit  900  via the testing connector  760 . 
     Another exemplary embodiment of the present invention provides a method for HVS testing an LCD device. To perform the HVS test, an LCD includes an internal connector having an input pin receiving a power supply voltage from an outside source, a no-connect pin, and a ground pin, and a power supply unit connected to the NC pin and the ground pin. The power supply unit receives the power supply voltage and outputs a gate-on voltage and a gate-off voltage whose levels are adjusted according to whether there is an electrical connection or disconnection between the no-connect pin and the ground pin, e.g., to perform the HVS test, the no-connect pin is electrically connected to the ground pin. When the no-connect pin is electrically connected to the ground pin, the gate-on voltage rises to become a testing gate-on voltage and the gate-off voltage falls to become a testing gate-off voltage. The testing gate-on and the testing gate-off voltages are applied to the LCD to perform the HVS test. 
     As described above, an LCD, a connector for testing the LCD and a method of testing the LCD according to exemplary embodiments of the present invention provide several advantages. For example, the LCD can be self-tested for HVS without a separately-provided HVS test apparatus. Thus, an HVS testing procedure for LCDs is simplified. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various modifications and changes in form and details may be made therein without departing from the spirit and scope of the present invention. It is therefore understood that the above exemplary embodiments are considered in all respects as illustrative and not restrictive and are intended to cover various modifications and equivalent arrangements of the present invention as described in the following claims.