Patent Publication Number: US-2012044235-A1

Title: Active matrix organic light emitting diode display

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2010-0080518 filed on Aug. 10, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an active matrix organic light, emitting diode display and a driving method thereof, and more particularly, to an active matrix organic light emitting diode display capable of sensing deterioration during an emission period to more rapidly sense deterioration and thus rapidly compensate therefor. 
     2. Description of the Related Art 
     Generally, in order to manufacture a large-sized display panel using an organic light-emitting diode (OLED), prominent as a next generation display device, the organic light-emitting diode is configured to have an active matrix structure, known as an active matrix OLED (referred to as an AMOLED). 
     Since the AMOLED does not require an additional light source, it has improved performance in terms of brightness, thickness, definition, speed, power consumption, and the like, as compared to an LCD panel using a backlight unit (BLU) providing an additional light source. 
     However, the AMOLED has disadvantages in that uniformity between pixels and uniformity over time are very low, and a circuit for compensating for the uniformity is required. 
     As an AMOLED driving scheme, there are provided a current driving scheme and a voltage driving scheme. The voltage driving scheme has a disadvantage, in that an output changes due to the deterioration of the mobility or the threshold voltage of a transistor. 
     In order to solve the disadvantage due to the deterioration of the threshold voltage, a compensation circuit for compensating the deterioration thereof is required. In addition, the AMOLED voltage driving scheme additionally requires a period for sensing a degree of deterioration, thereby causing the time required to detect and compensate for deterioration to be extended. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides an active matrix organic light emitting diode display capable of sensing deterioration during an emission period to more rapidly sense deterioration and thus rapidly compensate therefor. 
     According to an aspect of the present invention, there is provided an active matrix organic light emitting diode display, including: a data driver converting previously-prepared correction data into an analog correction signal and generating a driving signal according to the analog correction signal; a selector selecting a charging path for programming, according to the driving signal in a preset programming period and selecting a deterioration detection path in a preset emission period; a pixel unit including an organic light-emitting diode connected between a power supply receiving power and a ground, charged with a value corresponding to the correction data according to the driving signal an the programming period, and allowing current to flow to the organic light-emitting diode accord in to the charged value in the emission period; and an analog-to-digital converter (ADC) detecting a deterioration voltage having deterioration information regarding the organic light-emitting diode of the pixel unit in the emission period. 
     The pixel unit may further include: first and second MOS transistors connected in series between the power supply receiving the power and the organic light-emitting diode; a third MOS transistor connected between a gate of the first MOS transistor and the selector; and a charging capacitor connected between the gate of the first MOS transistor and the power supply. 
     The pixel unit may be configured such that the first and third MOS transistors are turned on and the second MOS transistor is turned off in the programming period and the first and second MOS transistors are turned on and the third transistor is turned off in the emission period. 
     The pixel unit may be configured such that current flows from the power supply to the selector through the first and third MOS transistors according to the driving signal, to store the value corresponding to the correction data in the charging capacitor in the programming period, and the current flows from the power supply to the ground through the first and second MS transistors and the organic light-emitting diode, according to the value stored in the charging capacitor in the emission period. 
     The ADO may be configured to detect the deterioration voltage having the deterioration information regarding the organic light-emitting diode at a connection node between the first and second MOS transistors of the pixel unit in the emission period. 
     The active matrix organic light emitting diode display may further include: a compensator generating as deterioration compensation signal for compensating for deterioration using the digital deterioration voltage from the ADC; and a converter converting input data into the correction data in which deterioration is compensated for using the deterioration compensation signal to provide the correction data to the data driver. 
     The active matrix organic light emitting diode display may further include a panel load corresponding to a load of a panel and formed between the selector and the pixel unit. 
     According to another aspect of the present invention, there is provided an active matrix organic light emitting diode display, including: a data driver converting previously-prepared correction data into an analog correction signal and generating a driving signal according to the analog correction signal, a selector selecting a charging path for programming, according to the driving signal in a preset programming period and selecting a deterioration detection path in a preset emission period; a pixel unit including an organic light-emitting diode connected between a power supply receiving power and a ground, charged with a value corresponding to the correction data according to the driving signal in the programming period, and allowing current to flow to the organic light-emitting diode according to the charged value in the emission period; an analog-to-digital converter (ADC) detecting a deterioration voltage having deterioration information regarding the organic light-emitting diode of the pixel unit in the emission period; a compensator generating a deterioration compensation signal for compensating for deterioration using the digital deterioration voltage from the ADC; and a converter converting input data into the correction data in which deterioration is compensated for using the deterioration compensation signal to provide the correction data to the data driver. 
     The pixel unit may further include: first and second MOS transistors connected in series between the power supply receiving the power and the organic light-emitting diode; a third MOS transistor connected between a gate of the first MOS transistor and the selector; and a charging capacitor connected between the gate of the first MOS transistor and the power supply. 
     The pixel unit may be configured such that the first and third MOS transistors are turned on and the second MOS transistor is turned off in the programming period, and the first and second MOS transistors are turned on and the third transistor is turned off in the emission period. 
     The pixel unit may be configured such that current flows from the power supply to the selector through the first and third MOS transistors according to the driving signal, to store the value corresponding to the correction data in the charging capacitor in the programming period, and the current flows from the power supply to the ground through the first and second MOS transistors and the organic light-emitting diode, according to the value stored in the charging capacitor in the emission period. 
     The ADC may configured to detect the deterioration voltage having the deterioration information regarding the organic light-emitting diode at a connection node between the first and second MOS transistors of the pixel unit in the emission period. 
     The active matrix organic light emitting diode display may further include a panel load corresponding to a load of a panel and formed between the selector and the pixel unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention; 
         FIG. 2  is a flowchart showing an operation of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention; 
         FIG. 3  is a time chart of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention; 
         FIG. 4  is a diagram describing an operation during a programming period of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention; and 
         FIG. 5  is a diagram describing an operation during an emission period of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     The present invention should not be limited to the embodiments set forth herein and the embodiments may be used to assist in understanding the technical idea of the present invention. Like reference numerals designate like components having substantially the same constitution and function in the drawings of the present invention. 
       FIG. 1  is a block diagram of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention may include a data driver  120  converting previously prepared correction data into an analog correction signal Scor and generating a driving signal according to the analog correction signal Scor, and a selector  130  selecting a charging path for programming, according to the driving signal in a preset programming period (P 1 ) and selecting deterioration detection path in a preset emission period (P 2 ). 
     Herein, the selector  130  selects the charging path or the deterioration detection path according to a selection signal Ssel. For example, when the selection signal Ssel is high ( 1 ), the selector  130  may select the charging path, and when the selection signal Ssel is low ( 0 ), it may select the deterioration detection path. 
     In addition, the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention may include a pixel unit  150  having an organic light-emitting diode OLED connected between a power supply receiving power ELVDD and a ground, charged with a value corresponding to the correction data according to the driving signal in the programming period P 1 , and allowing current to flow to the organic light-emitting diode OLED according to the charged value in the emission, period P 2 . 
     The active matrix organic light emitting diode display according to an exemplary embodiment of the present invention may include an analog-to-digital converter (ADC)  160  detecting a deterioration voltage Vd having deterioration information regarding the organic light-emitting diode OLED of the pixel unit  150  in the emission period P 2 . 
     The pixel unit  150  further includes first and second MOS transistors PM 1  and PM 2  connected in series between the power supply receiving the power ELVDD and the organic light-emitting diode OLED, a third MOS transistor PM 3  connected between a gate of the first MOS transistor PM 1  and the selector  130 , and a charging capacitor Ccha connected between the gate of the first MOS transistor PM 1  and the power supply. 
     The pixel unit  150  may be configured such that the first and third MOS transistors PM 1  and PM 3  are tuned on and the second MOS transistor PM 2  is turned off in the programming period P 1 , and the first and second MOS transistors PM 1  and PM 2  are turned on and the third transistor PM 3  is turned off in the emission period P 2 . 
     In addition, the pixel unit  150  may be configured such that current flows from he power supply to the selector  130  through the first and third MOS transistors PM 1  and PM 3  according to the driving signal, to store the value corresponding to the correction data in the charging capacitor Ccha in the programming period P 1 . 
     Further, the pixel unit  150  may be configured such that the current flows from the power supply to the ground through the first and second MOS transistors PM 1  and PM 2  and the organic light-emitting diode OLED according to the value stored in the charging capacitor Ccha in the emission period P 2 . 
     The ADC  160  may be configured to detect the deterioration voltage Vd having the deterioration information regarding the organic light-emitting diode OLED at a connection node between the first and second MOS transistors PM 1  and PM 2  of the pixel unit  150  in the emission period P 2 . 
     in addition, the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention may further include a compensator  170  generating a deterioration compensation signal Scon for compensating for deterioration using the digital deterioration voltage VDd from the ADC  160 , and a converter  110  converting input data into correction data in which deterioration is compensated for using the deterioration compensation signal Scon to provide the correction data to the data driver  120 . 
     Further, the active organic light-emitting diode according to an exemplary embodiment of the present invention may further include a panel load  140  corresponding to a load of a panel and formed between the selector  130  and the pixel unit  150 . 
       FIG. 2  is a flowchart showing an operation of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. A programming period P 1  starts (S 100 ) the operation. The programming period P 1  ends and an emission period P 2  starts (S 200 ). Deterioration is sensed in the emission period (S 300 ) Further, deterioration is compensated for, based on the deterioration sensing in the emission period (P 2 ). 
       FIG. 3  is a time chart of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. In  FIG. 3 , P 1  indicates a programming period, P 2  indicates an emission period, Sscan indicates a gate signal applied to a gate of the third MOS transistor PM 3  of the pixel unit  150 , Sem indicates a gate signal applied to a gate of the second MOS transistor P 2  of the pixel unit  150 , and VDd indicates digital deterioration voltage outputted from the ADC  160 . 
       FIG. 4  is a diagram describing an operation during a programming period of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention, and  FIG. 5  is a diagram describing operation during an emission period of an active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. 
     In  FIG. 4 , PHi indicates a current path in the programming period P 1  in the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. In  FIG. 5 , PHdet indicates a deterioration detection path in the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention. 
     Hereinafter, the operations and effects of the present invention will be described with reference to the accompanying drawings. 
     The active matrix organic light emitting diode display according to an exemplary embodiment of the present invention will be described for each of preset programming period P 1  and emission period P 2  with reference to  FIGS. 1 to 5 . 
     First, operation during the programming period P 1  of the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention will be described. 
     Referring to  FIG. 1 , the data driver  120  according to an exemplary embodiment of the present invention starts an operation, corresponding to the programming period, to convert the pre-prepared correction data into the analog correction signal Scor and generate the driving signal according to the analog correction signal Scar (S 100 ), as shown in  FIG. 2 . 
     The selector  130  according to an exemplary embodiment of the present invention selects the charging path for programming, according to the driving signal in the preset programming period P 1 . 
     That is, the selector  130  selects the charging path according to the selection signal (Ssel). For example, when the selection signal Ssel is high ( 1 ), the selector  130  may select the charging path. 
     At this time, the pixel unit  150  may be charged with the value corresponding to the correction data according to the driving signal in the programming period P 1 . 
     That is, the pixel unit  150  turns on the first and third MOS transistors PM 1  and PM 3  and turns off the second MOS transistor PM 2  in the programming period P 1 . 
     Accordingly, since the current path is selected in the selector  130  according to an exemplary embodiment of the present invention, the pixel unit  150  may allow the current to flow from the power supply to the selector  130  through the first and third MOS transistors PM 1  and PM 3  according to the driving signal, to store the value corresponding to the correction data in the charging capacitor Ccha in the programming period P 1 , as shown in  FIG. 4 . 
     Then, as shown in  FIGS. 2 and 3 , the programming period P 1  of the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention ends and the emission period P 2  thereof starts. 
     Meanwhile, the converter  110  according to an exemplary embodiment of the present invention may convert the input data Din into the correction data in which deterioration is compensated for to provide the correction data to the data driver  120 . 
     Hereinafter, operation during the emission period P 2  of the active matrix organic light emitting diode display according to an exemplary embodiment of the present invention will he described. 
     Referring to  FIG. 1 , the selector  130  according to an exemplary embodiment of the present invention starts an operation, corresponding to the emission period P 2 , to select the deterioration detection path in the preset emission period P 2 . 
     That is, the selector  130  may select, the deterioration detection path according to the selection signal Ssel. For example, when the selection signal Ssel is low ( 0 ) the selector  130  may select the deterioration detection path. 
     In addition, the pixel unit  150  according to an exemplary embodiment of the present invention allows the current to flow to the organic light-emitting diode OLED according to the charged value in the emission period P 2 . 
     That is, the pixel unit  150  turns on the first and second MOS transistors PM 1 , and PM 2  and turns off the third MOS transistor PM 3  in the emission period P 2 . 
     Accordingly, the pixel unit  150  allows the current to flow from the power supply to the ground through the first and second MOS transistors PM 1  and PM 2  and the organic light-emitting diode OLED according to the value stored in the charging capacitor Ccha in the emission period P 2 . 
     At the same time, the ADC  160  according to an exemplary embodiment of the present invention may detect the deterioration voltage Vd having the deterioration information regarding the organic light-emitting diode OLED of the pixel unit  150  through the deterioration detection path, selected in the selector  120 , in the emission period P 2 . 
     That is, the ADC  160  may detect the deterioration voltage Vd having the deterioration information regarding the organic light-emitting diode OLED at the connection node between the first and second MOS transistors PM 1  and PM 2  of the pixel unit  150  in the emission period P 2 . 
     The compensator  170  according to an exemplary embodiment of the present invention may continuously generate the deterioration compensation signal Scon for compensating for deterioration using digital deterioration voltage VDd from the ADC  160  to provide the deterioration compensation signal to the converter  110 . 
     At this time, the converter  110  converts the input data Din into the correction data in which the deterioration is compensated for using the deterioration compensation signal Scon to provide the correction data to the data driver  120 . 
     Accordingly, as described above, the data driver  120  may convert the correction data into the analog correction signal Scor and generate the driving signal according to the analog correction signal Scor. 
     As set forth above, according to the exemplary embodiments of the present invention, deterioration due to aging, temperature, and a process may be compensated for without being influenced by the deterioration of the mobility, the threshold voltage, and the like, of a transistor, with respect to the output thereof. 
     In addition, the influence due to the deterioration of the mobility and the threshold voltage of the transistor, with respect to the current driving the OLED, may be removed using a compensation current driving scheme. Furthermore, the deterioration degree of the OLED is sensed in the emission period without separately requiring a period sensing the deterioration degree of the OLED, such that deterioration may be compensated for, while the screen is displayed. 
     As set forth above, according to the exemplary embodiments of the present invention, the sensing and compensation of deterioration are simultaneously performed in the emission period, such that deterioration may be more rapidly sensed and compensated for. 
     while the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.