Abstract:
A display having voltage-driven organic light-emitting pixel circuits. Each pixel circuit includes an organic light-emitting diode, a data writing circuit, a capacitor, three transistors, and a switch. The pixel circuit can compensate the threshold voltage variations of low temperature poly silicon thin film transistors. This increases the stability of the voltage-driven organic light-emitting pixel circuits, improves the uniformity of the luminance of the display, and provides a larger aperture ratio for the pixels.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Taiwan application serial no. 94141669, filed Nov. 28, 2005, the contents of which are incorporated by reference. 
     BACKGROUND 
     The present invention generally relates to an organic light-emitting diode display panel, and more particularly, to an organic light-emitting diode display panel that compensates for variations in threshold voltages. 
     At present, small, thin, short, and light-weighted electronic products are popular and easily accepted by consumers. Also, because of the advantages of being light, thin and easy to place and carry in comparison with the traditional cathode ray tube (CRT) displays, flat panel displays have become widely used nowadays and have a bright prospect. 
     Please refer to  FIG. 1 , which illustrates a conventional voltage-driven organic light-emitting pixel  100 , the voltage-driven organic light-emitting diode pixel  100  includes transistors m 1 , m 2 , m 4 , m 5 , m 6 , and a capacitor Cst having terminals C and D. In addition, a sustaining voltage line Sus_N−3 is electrically coupled to the transistor m 5 , a scan line Scan_N−3 is electrically coupled to gates of the transistors m 2 , m 4 , m 5 , and m 6 , and a data line Data_N−3 is electrically coupled to the transistor m 6 . The signal carried on the scan line Scan_N−3 can determine whether to establish a connection between the terminal C and the sustaining voltage line Sus_N−3 or between the terminal C and the data line Data_N−3. A terminal of the transistor m 1  is electrically coupled to a first predetermined voltage VDD. Furthermore, a terminal of the transistor m 4  is electrically coupled to a terminal of an organic light-emitting diode  110 , and another terminal of the organic light-emitting diode  110  is electrically coupled to a second predetermined voltage VSS. The above-mentioned circuitry structure can compensate for variations in the threshold voltages (Vth) of the driving transistors of the voltage-driven organic light-emitting pixels. To realize such a compensation function, a prerequisite is that the circuit has to ensure that a voltage of the capacitor terminal D is pulled down to a voltage less than VDD−Vth before data is written; otherwise the compensation function of the pixel circuit may fail. However, this circuitry structure does not provide such an assurance action; the pixel circuit therefore has a low stability, and this may lead to luminance non-uniformity (so-called “Mura”) of the display panel due to failure of the compensation function. 
       FIG. 2  illustrates a timing diagram of signals of the pixel circuit of  FIG. 1 . Referring to  FIGS. 1 and 2 , the data line Data_N−3 carries a data signal voltage Vdata 0  of a data signal Data 0 . The scan line Scan_N−3 carries a scan voltage signal VScan_N, and the sustaining voltage line Sus_N−3 carries a sustaining voltage Vsus. At image  0 , the scan voltage signal VScan_N is at “LOW” logic level, the data signal voltage Vdata 0  of the data signal Data 0  on the data line Data_N−3 is written into the terminal C and the voltage of the terminal D is pulled up to VDD−Vth. Then, when the scan voltage signal VScan_N is at “HIGH” logic level, the voltage of the terminal C is pulled up by a voltage difference of (Vsus−Vdata 0 ). At this time, the voltage of the terminal D is pulled up to VDD−Vth+(Vsus−Vdata 0 ) due to the voltage stabilization effect of the capacitor Cst. Thereafter, the operation at image  1  is similar to the operation at image  0 , but it can be seen from  FIG. 2 , before the data signal Data l is written into the terminal C, the situation of Vd&gt;VDD−Vth is still not improved. As a result, the panel formed by the voltage-driven organic light-emitting diode pixels is not able to compensate the threshold voltage (Vth) variation of the driving transistors of the voltage-driven organic light-emitting diode pixels. 
     In another aspect, current flat panel displays are becoming higher in resolution. The traditional pixels may not be suitable for use in active organic light-emitting diode display panels with high resolution. This is because the pixels include too many transistors, causing the aperture ratio to be too low. 
     SUMMARY 
     The present invention is directed to a voltage-driven organic light-emitting diode pixel which can ensure that a voltage of a capacitor terminal is lower than a predetermined voltage before each time the data is written, thereby ensuring that the threshold voltage variation of driving transistors of the pixels of a display panel can be compensated, thus avoiding luminance non-uniformity of the pixels on the display panel. 
     The present invention is also directed to an organic light-emitting diode display panel that includes the above-mentioned voltage-driven organic light-emitting diode pixels, allowing the pixels to have relatively larger aperture ratios, thus increasing pixel luminance and reducing cost. 
     The present invention is further directed to an organic light-emitting diode display panel that can improve the luminance non-uniformity of an image due to a drop in supply voltage (IR drop) of the display panel. 
     The voltage-driven organic light-emitting diode pixel of the present invention includes an organic light-emitting diode, a data writing circuit, a capacitor, a first transistor, a second transistor, a third transistor and a first switch. The organic light-emitting diode has a first terminal and a second terminal. The data writing circuit is electrically coupled to a data line, a sustaining voltage line and a first scan line. The data writing circuit determines whether to establish an electrical connection between an output terminal thereof and the data line or between the output terminal thereof and the sustaining voltage line according to a first scan signal carried on the first scan line. The capacitor has a first terminal and a second terminal. The first terminal of the capacitor is electrically coupled to the output terminal of the data writing circuit. 
     In addition, the first transistor has first and second signal terminals and a control terminal. The first signal terminal of the first transistor is electrically coupled to a first predetermined voltage, the second signal terminal of the first transistor is electrically coupled to the first terminal, and the control terminal of the first transistor is electrically coupled to the second terminal of the capacitor. The second transistor has first and second signal terminals and a control terminal. The first signal terminal of the second transistor is electrically coupled to the control terminal of the first transistor, the second signal terminal of the second transistor is electrically coupled to the first terminal, and the control terminal of the second transistor is configured to receive the first scan signal. The third transistor has first and second signal terminals and a control terminal. The first signal terminal and the control terminal of the third transistor are both electrically coupled to a second scan line, and the second signal terminal of the third transistor is electrically coupled to the first signal terminal of the second transistor. The first switch has a switch terminal electrically coupled to the second terminal, and another switch terminal electrically coupled to a second predetermined voltage. The first switch is configured to turn on or turn off according to the first scan signal. The first, second and third transistors are of a same conductive type, and scan sequence of the second scan line is arranged before that of the first scan line. 
     According to one embodiment of the present invention, the data writing circuit includes a second switch and a third switch. The second switch is electrically coupled between the sustaining voltage line and the output terminal of the data writing circuit, and is configured to turn on or turn off according to the first scan signal. The third switch is electrically coupled between the data line and the output terminal of the data writing circuit, and is configured to turn on or turn off according to the first scan signal, wherein turn-on time durations of the second and third switches do not overlap. 
     According to one embodiment of the present invention, the first switch of the voltage-driven organic light-emitting diode pixel includes a fourth transistor having first and second signal terminals and a control terminal. The first signal terminal of the fourth transistor is electrically coupled to the second terminal node, the control terminal of the fourth transistor is configured to receive the first scan signal, and the second signal terminal of the fourth transistor is electrically coupled to the second predetermined voltage. The second switch includes a fifth transistor having first and second signal terminals and a control terminal. The first signal terminal of the fifth transistor is electrically coupled to the sustaining voltage line, the control terminal of the fifth transistor is configured to receive the first scan signal, and the second signal terminal of the fifth transistor is electrically coupled to the output terminal of the data writing circuit. The third switch includes a sixth transistor having first and second signal terminals and a control terminal. The first signal terminal of the sixth transistor is electrically coupled to the data line, the second signal terminal of the sixth transistor is electrically coupled to the output terminal of the data writing circuit; and the control terminal of the sixth transistor is configured to receive the first scan signal. The sixth transistor and the first transistor are of a same conductive type, and the conductive types of the fourth and fifth transistors are different from that of the first transistor. 
     According to one embodiment of the present invention, the data writing circuit includes a second switch and a third switch. The second switch is electrically coupled between the sustaining voltage line and the output terminal of the data writing circuit, and is configured to receive an inverting signal having a phase opposite to the first scan signal to determine turn-on or turn-off thereof. The third switch is electrically coupled between the data line and the output terminal of the data writing circuit, and is configured to turn on or turn off according to the first scan signal, wherein turn-on time durations of the second and third switches do not overlap. Specifically, the first switch includes a fourth transistor, and the fourth transistor has first and second signal terminals and a control terminal. The first signal terminal of the fourth transistor is electrically coupled to the second terminal node, the control terminal of the fourth transistor is configured to receive the inverting signal, and the second signal terminal of the fourth transistor is electrically coupled to the second predetermined voltage. The second switch includes a fifth transistor having first and second signal terminals and a control terminal. The first signal terminal of the fifth transistor is electrically coupled to the sustaining voltage line, the control terminal of the fifth transistor is configured to receive the inverting signal, and the second signal terminal of the fifth transistor is electrically coupled to the output terminal of the data writing circuit. The third switch includes a sixth transistor having first and second signal terminals and a control terminal. The first signal terminal of the sixth transistor is electrically coupled to the data line, the second signal terminal of the sixth transistor is electrically coupled to the output terminal of the data writing circuit; and the control terminal of the sixth transistor is configured to receive the first scan signal. 
     The organic light-emitting diode display panel of the present invention uses multiple scan lines to control turn-on or turn-off of multiple organic light-emitting diode pixels, wherein the multiple organic light-emitting diode pixels can be implemented with the above-mentioned organic light-emitting diode pixel. When the organic light-emitting diode display panel determines, according to the first scan signal, whether to establish electrical connection between the output terminal and the organic light-emitting diode pixels in the data line or in the sustaining voltage line, at least two of the organic light-emitting diode pixels have their second terminals electrically coupled to the first terminal of the first switch. Therefore, the first switch can be arranged outside the pixel, thus increasing the aperture ratio of the pixel and reducing manufacturing cost of the active organic light-emitting diode display panel. 
     These together with other objects of the invention, along with the various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the invention. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a circuit diagram of a conventional voltage-driven organic light-emitting diode pixel. 
         FIG. 2  illustrates a timing diagram of the signals of the pixel of  FIG. 1 . 
         FIG. 3A  illustrates a circuit block diagram of a voltage-driven organic light-emitting diode pixel in accordance with an embodiment of the present invention. 
         FIG. 3B  illustrates a circuit diagram of a voltage-driven organic light-emitting diode pixel in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates a timing diagram of the signals of the pixel of  FIG. 3B . 
         FIG. 5  illustrates a circuit diagram of another voltage-driven organic light-emitting diode pixel in accordance with  FIG. 3B . 
         FIG. 6  illustrates a circuit diagram of a further voltage-driven organic light-emitting diode pixel in accordance with  FIG. 3B . 
         FIG. 7  illustrates a part of the circuit diagram of an organic light-emitting diode display panel formed by the voltage-driven organic light-emitting diode pixels of  FIG. 6 . 
         FIG. 8  illustrates a part of the circuit diagram of another organic light-emitting diode display panel in accordance with the circuit diagram of the organic light-emitting diode display panel of  FIG. 7 . 
         FIG. 9  illustrates a part of the circuit diagram of an organic light-emitting diode display panel formed by the voltage-driven organic light-emitting diode pixels of  FIG. 5 . 
         FIG. 10  illustrates a part of the circuit diagram of an organic light-emitting diode display panel formed by the voltage-driven organic light-emitting diode pixels of  FIG. 3B . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 3A , this figure illustrates a circuit block diagram of a voltage-driven organic light-emitting diode pixel  300  (referred to as “OLED pixel” hereinafter) in accordance with an embodiment of the present invention. In this embodiment, the OLED pixel  300  includes an organic light-emitting diode  310  (referred to as “OLED” hereinafter), a data writing circuit  320 , a capacitor  330 , transistors M 1 , M 2 , M 3 , and a switch  370 . 
     The OLED  310  has a first terminal  310   a  and a second terminal  310   b , and the data writing circuit  320  is electrically coupled to a data line Data_N, a sustaining voltage line Sus_N, and a scan line Scan_N. The data writing circuit  320  determines whether to establish an electrical connection between an output terminal of the data writing circuit  320  and the data line Data_N or between the output terminal of the data writing circuit  320  and the sustaining voltage line Sus_N according to a scan voltage signal VScan_N carried on the scan line Scan_N. In addition, the capacitor  330  has a terminal A and a terminal B, and the terminal A is electrically coupled to the output terminal of the data writing circuit  320 . 
       FIG. 3B  illustrates a circuit diagram of the voltage-driven OLED pixel in accordance with an embodiment of the present invention. Referring to  FIGS. 3A and 3B , in  FIG. 3A , the transistor M 1  has a first signal terminal electrically coupled to a first predetermined voltage VDD, a second signal terminal electrically coupled to the first terminal  310   a , and a control terminal electrically coupled to the terminal B of the capacitor  330 . The transistor M 2  has a first signal terminal electrically coupled to the control terminal of the transistor M 1 , a second signal terminal electrically coupled to the first terminal  310   a , and a control terminal configured to receive the scan voltage signal VScan_N. The transistor M 3  has a first signal terminal and a control terminal both electrically coupled to a scan line Scan_N−1, and a second signal terminal electrically coupled to the first signal terminal of the transistor M 2 . The switch  370  has one terminal electrically coupled to the second terminal  310   b , and another terminal electrically coupled to a second predetermined voltage VSS. Turn-on or turn-off of the switch  370  is determined according to the scan voltage signal VScan_N. In this embodiment, the transistors M 1 , M 2 , and M 3  are all P-type thin film transistors, and scanning sequence of the scan line Scan_N−1 is arranged before that of the scan line Scan_N. 
     In  FIG. 3B , the data writing circuit  320  includes a switch  322  and a switch  323 . The switch  322  is electrically coupled between the sustaining voltage line Sus_N and the output terminal of the data writing circuit  320 , and is configured to turn on or turn off according to the scan voltage signal VScan_N. The switch  323  is electrically coupled between the data line Data_N and the output terminal of the data writing circuit  320 , and is configured to turn on or turn off according to the scan voltage signal VScan_N. Turn-on time durations of the switch  322  and switch  323  do not overlap. 
     In this embodiment, the switch  370  of the voltage-driven OLED pixel includes a transistor M 4 . The transistor M 4  has a first signal terminal electrically coupled to the second terminal  310   b , a control terminal configured to receive the scan voltage signal VScan_N, and a second signal terminal electrically coupled to the second predetermined voltage VSS. The switch  322  includes a transistor M 5 . The transistor M 5  has a first signal terminal electrically coupled to the sustaining voltage line Sus_N, a control terminal configured to receive the scan voltage signal VScan_N, and a second signal terminal electrically coupled to the output terminal of the data writing circuit  320 . The switch  323  includes a transistor M 6 . The transistor M 6  includes a first signal terminal electrically coupled to the data line Data_N, a second signal terminal electrically coupled to the output terminal of the data writing circuit  320 , and a control terminal configured to receive the scan voltage signal VScan_N. The transistors M 6  and M 1  are both P-type thin film transistors and the transistors M 4  and M 5  are both N-type thin film transistors. 
       FIG. 4  illustrates a timing diagram of the signals of  FIG. 3B . Referring to  FIG. 3B  and  FIG. 4 , at image  0 , before writing data, that is, when the scan voltage signal VScan_N is at “HIGH” logic level and the scan voltage signal VScan_N−1 is at “LOW” logic level, the transistor M 3  is turned on, the transistor M 1  is turned on, the transistor M 5  is turned on, and the transistor M 6  is turned off. As a result, the voltage of the terminal A is equal to the sustaining voltage Vsus carried on the sustaining voltage line Sus_N. In addition, the voltage of the terminal B is equal to the “LOW” logic level of the scan voltage signal VScan_N−1 plus a threshold voltage Vth of the transistor M 3 , that is, VScan_N−1+Vth. Therefore, it can ensure that the voltage of the terminal B is below VDD−Vth. When the data are written, that is, when the scan voltage signal VScan_N is at “LOW” logic level and the scan voltage signal VScan_N−1 is at “HIGH” logic level, the transistor M 3  is turned off, the transistor M 1  is turned on, the transistor M 5  is turned off, and the transistor M 6  is turned on. As a result, the voltage of the terminal A is equal to the data signal voltage Vdata 0  of the data signal Data 0  at this time, and the voltage of the terminal B is pulled up to VDD−Vth. Thereafter, when the scan voltage signal VScan_N and the scan voltage signal VScan_N−1 are both at “HIGH” logic level, the transistor M 3  is turned off, the transistor M 1  is turned on, the transistor M 5  is turned on, and the transistor M 6  is turned off. As a result, the voltage of the terminal A is equal to the sustaining voltage Vsus, which means that the voltage of the terminal A is increased by Vsus−Vdata 0 . Therefore, the voltage of the terminal B becomes VDD−Vth+(Vsus−Vdata 0 ) due to a voltage stabilizing function of the capacitor  330 , causing the OLED  310  to emit light, wherein the amount of the current Id that flows through the OLED  310  can be described as follows: 
                     I   d     =       1   2     ⁢       β   ⁡     (       V   gs     -     V   th       )       2                   =       1   2     ⁢       β   ⁡     [       V   DD     -     (       V   DD     -     V   th     +     V   sus     -     V     data   ⁢           ⁢   0         )     -     V   th       ]       2                   =       1   2     ⁢       β   ⁡     (       V     data   ⁢           ⁢   0       -     V   sus       )       2                   
wherein Vgs represents a voltage difference between gate and source of the transistor M 1 , and β is a transconductance parameter used to calculate the current Id flowing through the OLED  310 . It can be known from the equation (1), the amount of the current Id flowing through the OLED  310  depends on the data signal voltage Vdata 0  and the sustaining voltage Vsus, but there are no current paths for the data signal voltage Vdata 0  and the sustaining voltage Vsus, the problem of IR drop can thus be avoided.
 
     Afterwards, at image  1 , operations of the terminal A and the terminal B are similar to the situation at image  0 . It can be known from the above description, the voltage-driven OLED pixel  300  of the present invention can ensure that the voltage of the terminal B is lower than VDD−Vth before each time the data is written, so that when each time the data is written, the voltage of the terminal B can be pulled up to VDD−Vth. Therefore, the pixel circuitry structure of the present invention can compensate for the threshold voltage variations of the driving transistors of the voltage-driven OLED pixels  300  of a display panel that is formed by the OLED pixels  300 . 
       FIG. 5  illustrates another embodiment of the voltage-driven OLED pixel  500  in accordance with  FIG. 3B . Referring to  FIG. 5 , the voltage-driven OLED pixel  500  includes transistors M 1 ˜M 6 , an OLED  310 , and a capacitor  330  having terminals A, B. In addition, the transistor M 1  is electrically coupled to a first predetermined voltage VDD, and the transistor M 4  is electrically coupled to a second predetermined voltage VSS. A scan line Scan_N is electrically coupled to control terminals of the transistors M 2 , M 4 , M 5  and M 6 . A scan voltage signal carried on the scan line Scan_N. determines whether or not to establish an electrical connection between the terminal A and a sustaining voltage line Sus_N or between the terminal A and a data line Data_N. A scan line Scan_N−1 is electrically coupled to a control terminal and a first signal terminal of the transistor M 3 . 
     In this embodiment, the transistors M 1 , M 2 , M 3  and M 6  are all P-type thin film transistors; the transistors M 4  and M 5  are both N-type thin film transistors, and the scan sequence of the scan line Scan_N−1 is arranged immediately before that of the scan line Scan_N. 
     The voltage-driven OLED pixel  500  described above can also compensate for the threshold voltage variations of the driving transistors of the voltage-driven OLED pixels that form the display panel. In addition, in this embodiment, the transistor M 4  and the second predetermined voltage VSS can be arranged outside the voltage-driven OLED pixel  500  in order to increase the aperture ratio of the voltage-driven OLED pixel  500 . 
       FIG. 6  illustrates a further embodiment of the voltage-driven OLED pixel  600  in accordance with  FIG. 3B . Referring to  FIG. 3B  and  FIG. 6 , the transistors M 1 ˜M 6  of  FIG. 3B  are substituted with p-type transistors M 1 , M 2 , M 3 , M 6 , M 7 , M 8 , respectively. This substitution can improve process yield and circuit stability, and reduce manufacturing cost. Further, the voltage-driven OLED pixel  600  includes an OLED  610 , a data writing circuit  620 , a capacitor  330 , the transistors M 1 , M 2 , M 3  and a switch  670 , wherein the OLED  610  has a first terminal  610   a  and a second terminal  610   b . The data writing circuit  620  is electrically coupled to a data line Data_N, a sustaining voltage line Sus_N and a scan line Scan_N, and the data writing circuit  620  determines whether to establish an electrical connection between an output terminal of the data writing circuit  620  and the data line Data_N or between the output terminal and the sustaining voltage line Sus_N according to a scan voltage signal VScan_N carried on the scan line Scan_N. The capacitor  330  includes terminals A and B, and the terminal A is electrically coupled to the output terminal of the data writing circuit  620 . 
     In  FIG. 6 , the transistor M 1  has a first signal terminal electrically coupled to a first predetermined voltage VDD, a second signal terminal electrically coupled to the first terminal  610   a , and a control terminal electrically coupled to the terminal B of the capacitor  330 . The transistor M 2  has a first signal terminal electrically coupled to the control terminal of the transistor M 1 , a second signal terminal electrically coupled to the first terminal  610   a , and a control terminal configured to receive the scan voltage signal VScan_N. The transistor M 3  has a first signal terminal and a control terminal both electrically coupled to a scan line Scan_N−1, and a second signal terminal electrically coupled to the first signal terminal of the transistor M 2 . The switch  670  has one terminal electrically coupled to the second terminal  610   b , and another terminal electrically coupled to a second predetermined voltage VSS. Turn-on or turn-off of the switch  670  is determined according to the scan voltage signal VScan_N. Scan sequence of the scan line Scan_N−1 is arranged immediately before that of the scan line Scan_N. 
     In  FIG. 6 , the data writing circuit  620  includes a switch  622  and a switch  623 . The switch  622  is electrically coupled between the sustaining voltage line Sus_N and the output terminal of the data writing circuit  620 , and is configured to turn on or turn off according to the scan voltage signal VScan_N. The switch  623  is electrically coupled between the data line Data_N and the output terminal of the data writing circuit  620 , and is configured turn on or turn off according to the scan voltage signal VScan_N. Turn-on time durations of the switch  622  and switch  623  do not overlap. 
     In addition, in order to make operation and voltage of the transistors M 7  and M 8  of the voltage-driven OLED pixel  600  of  FIG. 6  the same as those of the transistors M 4  and M 5  of the voltage-driven OLED pixel  300  of  FIG. 3B , the voltage-driven OLED pixel  600  further includes an inverting scan line  Scan_N  for the scan line Scan_N. The inverting scan line  Scan_N  is electrically coupled to control terminals of the transistors M 7  and M 8  to drive the transistors M 7  and M 8 . 
     In this embodiment, the switch  670  of the voltage-driven OLED pixel includes the transistor M 7 . The transistor M 7  has a first signal terminal electrically coupled to the second terminal  610   b , a control terminal electrically coupled to the inverting scan line  Scan_N , and a second signal terminal electrically coupled to the second predetermined voltage VSS. The switch  622  includes the transistor M 8 . The transistor M 8  has a first signal terminal electrically coupled to the sustaining voltage line Sus_N, a control terminal electrically coupled to the inverting scan line  Scan_N , and a second signal terminal electrically coupled to the output terminal of the data writing circuit  620 . The switch  623  includes the transistor M 6 . The transistor M 6  includes a first signal terminal electrically coupled to the data line Data_N, a second signal terminal electrically coupled to the output terminal of the data writing circuit  620 , and a control terminal configured to receive the scan voltage signal VScan_N. The transistors M 6 , M 7 , M 8  are all P-type thin film transistors. 
       FIG. 7  illustrates a part of the circuit diagram of an organic light-emitting diode display panel  700  (referred to as “OLED panel”) formed by the voltage-driven OLED pixels of  FIG. 6 . Referring to  FIG. 7 , transistors M 1 , M 2 , M 3 , M 6 , M 8 , the first predetermined voltage VDD, and electrical connections and signals of other components of each of the voltage-driven OLED pixels  710 - 790  of the OLED panel  700  are all similar to those of the voltage-driven OLED pixel  600  of  FIG. 6 . In addition, the transistors M 71 -M 73  can be arranged outside the voltage-driven OLED pixels  710 - 790 , wherein the voltage-driven OLED pixels  710 ,  720 ,  730  of the OLED panel  700  share the transistor M 71 , the voltage-driven OLED pixels  740 ,  750 ,  760  share the transistor M 72 , the voltage-driven OLED pixels  770 ,  780 ,  790  share the transistor M 73 , and the sustaining voltage Vsus is shared by the voltage-driven OLED pixels  710 - 790 . Further, the second predetermined voltage VSS can be electrically coupled to the second signal terminals of the transistors M 71 , M 72 , and M 73  and arranged outside the voltage-driven OLED pixels  710 - 790 . All of these arrangements can increase the aperture ratio of the voltage-driven OLED pixels  710 ˜ 790  of the OLED panel  700 . 
     In addition, the OLED panel  700  employs multiple scan lines Scan_N, Scan_N+1, Scan_N+2 to control turn-on and turn-off states of, for example, the transistors of the voltage-driven OLED pixels  710 - 790 , wherein the sustaining voltage Vsus can also be shared by the OLED pixels  710 - 790 . Also, inverters Inv 1 , Inv 2  and Inv 3  are configured to invert respective signals of the scan line Scan_N, Scan_N+1, Scan_N+2, wherein the inverter Inv 1  is configured to invert the signal of the scan line Scan_N and input it into the voltage-driven OLED pixels  710 ,  720 ,  730 , the inverter Inv 2  is configured to invert the signal of the scan line Scan_N+1 and input it into the voltage-driven OLED pixels  740 ,  750 ,  760 , and the inverter Inv 3  is configured to invert the signal of the scan line Scan_N+2 and input it into the voltage-driven OLED pixels  770 ,  780 ,  790 . In addition, the signals of the scan line Scan_N−1 and the scan line Scan_N are inputted into the voltage-driven OLED pixels  710 ,  720 ,  730 , the signals of the scan line Scan_N and the scan line Scan_N+1 are inputted into the voltage-driven OLED pixels  740 ,  750 ,  760 , and the signals of the scan line Scan_N+1 and the scan line Scan_N+2 are inputted into the voltage-driven OLED pixels  770 ,  780 ,  790 . Besides, the data line Data_N supplies data to the voltage-driven OLED pixels  710 ,  740 ,  770  on the same column, the data line Data_N+1 supplies data to the voltage-driven OLED pixels  720 ,  750 ,  780  on the same column, and the data line Data_N+2 supplies data to the voltage-driven OLED pixels  730 ,  760 ,  790  on the same column. 
       FIG. 8  illustrates a part of the circuit diagram of another OLED panel  800  in accordance with the circuit diagram of the OLED panel of  FIG. 7 . Referring to  FIG. 8 , transistors M 1 , M 2 , M 3 , M 6 , M 8 , the first predetermined voltage VDD, and electrical connections and signals of other components of each of the OLED pixels  810 - 890  of the OLED panel  800  are all similar to those of the voltage-driven OLED pixel  600  of  FIG. 6 . In addition, the transistors M 71 -M 73  can be arranged outside the voltage-driven OLED pixels  810 ˜ 890 , wherein the voltage-driven OLED pixels  810 ,  820 ,  830  of the OLED panel  800  share the transistor M 71 , the voltage-driven OLED pixels  840 ,  850 ,  860  share the transistor M 72 , the voltage-driven OLED pixels  870 ,  880 ,  890  share the transistor M 73 , and the sustaining voltage Vsus is shared by the voltage-driven OLED pixels  810 - 890 . Besides, the second predetermined voltage VSS can be electrically coupled to the second signal terminals of the transistors M 71 -M 73  and arranged outside the voltage-driven OLED pixels  810 - 890 . All of these arrangements can increase the aperture ratio of the voltage-driven OLED pixels  810 - 890  of the OLED panel  800 . 
     In addition, the OLED panel  800  employs multiple scan lines Scan_N, Scan_N+1, Scan_N+2 to control turn-on and turn-off states of, for example, the transistors of the voltage-driven OLED pixels  810 - 890 , wherein the sustaining voltage Vsus can also be commonly used by the OLED pixels  810 - 890 . Also, inverters Inv 1 , Inv 2  and Inv 3  are configured to respectively invert signals of the scan line Scan_N, Scan_N+1, Scan_N+2, wherein the inverter Inv 1  is configured to invert the signal of the scan line Scan_N and input it into the voltage-driven OLED pixels  810 ,  820 ,  830 , the inverter Inv 2  is configured to invert the signal of the scan line Scan_N+1 and input it into the voltage-driven OLED pixels  840 ,  850 ,  860 , and the inverter Inv 3  is configured to invert the signal of the scan line Scan_N+2 and input it into the voltage-driven OLED pixels  870 ,  880 ,  890 . In addition, the signals of the scan line Scan_N−1 and scan line Scan_N are inputted into the voltage-driven OLED pixels  810 ,  820 ,  830 , the signals of the scan line Scan_N and scan line Scan_N+1 are inputted into the voltage-driven OLED pixels  840 ,  850 ,  860 , and the signals of the scan line Scan_N+1 and scan line Scan_N+2 are inputted into the voltage-driven OLED pixels  870 ,  880 ,  890 . Besides, the data line Data_N supplies data to the voltage-driven OLED pixels  810 ,  840 ,  870  on the same column, the data line Data_N+1 supplies data to the voltage-driven OLED pixels  820 ,  850 ,  880  on the same column, and the data line Data_N+2 supplies data to the voltage-driven OLED pixels  830 ,  860 ,  890  on the same column. 
     Further, the OLED panel  800  includes insulating layers ILC 1 , ILC 2  and ILR 1 -ILR 4  to isolate cathodes of the voltage-driven OLED pixels, thereby preventing the cathodes of the voltage-driven OLED pixels (for example, the voltage-driven OLED pixels  810 - 830 ) on each scan line from electrically connecting directly with the cathodes of the voltage-driven OLED pixels on other scan lines to avoid short circuit between the cathodes of the voltage-driven OLED pixels on different scan lines. 
       FIG. 9  illustrates a part of the circuit diagram of an OLED panel formed by the OLED pixels of  FIG. 5 . Referring to  FIG. 9 , in the OLED panel  900 , transistors M 1 , M 2 , M 3 , M 6 , M 8 , the first predetermined voltage VDD, and electrical connections and signals of other components of each of the OLED pixels  910 - 990  are all similar to those of the voltage-driven OLED pixel  500  of  FIG. 5 . In addition, transistors M 41 ˜M 43  can be arranged outside the voltage-driven OLED pixels  910 - 990 , wherein the transistor M 41  is shared by the voltage-driven OLED pixels  910 ,  920 ,  930  of the OLED panel  800 , the transistor M 42  is shared by the voltage-driven OLED pixels  940 ,  950 ,  960 , the transistor M 43  is shared by the voltage-driven OLED pixels  970 ,  980 ,  990 , and the sustaining voltage Vsus is shared by the voltage-driven OLED pixels  910 - 990 . In addition, the second predetermined voltage VSS can be electrically coupled to second signal terminals of the transistors M 41 -M 43  and arranged outside the voltage-driven OLED pixels  910 - 990 . All of these arrangements can increase the aperture ratio of the voltage-driven OLED pixels  910 - 990  of the OLED panel  900 . 
     In addition, the OLED panel  900  employs multiple scan lines Scan_N, Scan_N+1, Scan_N+2 to control turn-on and turn-off states of, for example, the transistors of the voltage-driven OLED pixels  910 ˜ 990 . In addition, the signals of the scan line Scan_N−1 and the scan line Scan_N are inputted into the voltage-driven OLED pixels  910 ,  920 ,  930 , the signals of the scan line Scan_N and the scan line Scan_N+1 are inputted into the voltage-driven OLED pixels  940 ,  950 ,  960 , and the signals of the scan line Scan_N+1 and the scan line Scan_N+2 are inputted into the voltage-driven OLED pixels  970 ,  980 ,  990 . Besides, the data line Data_N supplies data to the voltage-driven OLED pixels  910 ,  940 ,  970  on a same column, the data line Data_N+1 supplies data to the voltage-driven OLED pixels  920 ,  950 ,  980  on a same column, and the data line Data_N+2 supplies data to the voltage-driven OLED pixels  930 ,  960 ,  990  on a same column. 
       FIG. 10  illustrates a part of the circuit diagram of an OLED panel  1000  formed by the voltage-driven OLED pixels of  FIG. 3B . Referring to  FIG. 10 , in the OLED panel  1000  of this embodiment, transistors M 1 -M 6 , the first predetermined voltage VDD, the second predetermined voltage VSS, and electrical connections and signals of other components of each of the OLED pixels  1010 - 1090  are all similar to those of the voltage-driven OLED pixel  300  of  FIG. 3B . In addition, the sustaining voltage Vsus can also be shared by the OLED pixels  1010 - 1090 . This can increase the aperture rate of the voltage-driven OLED pixels  1010 - 1090  of the OLED panel  1000 . 
     In addition, the OLED panel  1000  employs multiple scan lines Scan_N, Scan_N+1, Scan_N+2 to control turn-on and turn-off states of, for example, the transistors of the voltage-driven OLED pixels  1010 - 1090 . In addition, the signals of the scan line Scan_N−1 and the scan line Scan_N are inputted into the voltage-driven OLED pixels  1010 ,  1020 ,  1030 , the signals of the scan line Scan_N and the scan line Scan_N+1 are inputted into the voltage-driven OLED pixels  1040 ,  1050 ,  1060 , and the signals of the scan line Scan_N+1 and the scan line Scan_N+2 are inputted into the voltage-driven OLED pixels  1070 ,  1080 ,  1090 . Besides, the data line Data_N supplies data to the voltage-driven OLED pixels  1010 ,  1040 ,  1070  on a same column, the data line Data_N+1 supplies data to the voltage-driven OLED pixels  1020 ,  1050 ,  1080  on a same column, and the data line Data_N+2 supplies data to the voltage-driven OLED pixels  1030 ,  1060 ,  1090  on the same column. 
     In summary, because the voltage-driven OLED pixels of the present invention can ensure that the voltage of the terminal B in  FIGS. 3B ,  5  and  6  is in a level below VDD−Vth before each time the data is written, and part of the components can be arranged outside the OLED pixels and shared by multiple OLED pixels of the OLED panel, the variations of the threshold voltage Vth of the driving transistors of the OLED panel can be compensated, thus avoiding luminance non-uniformity of the pixels on the OLED panel. Also because of this, the voltage-driven OLED pixel can have a relatively larger aperture ratio, thus increasing pixel luminance and reducing cost. Moreover, the present invention can also avoid luminance non-uniformity of the image due to the IR drop of the OLED panel. 
     Although the preferred embodiments of the invention have been described above, it will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.