Abstract:
An active matrix organic light emitting diode (AMOLED) display device including a panel, a master source driver and at least one slave source driver is provided. The panel has a group of master column pixels and at least one group of slave column pixels. The master source driver receives a reference current and duplicates the reference current to output a master current for driving the group of master column pixels. The at least one slave source driver, coupled to the master source driver or a preceding slave source driver, duplicates the master current or a slave current outputted by the preceding slave source driver as a new slave current and outputs the new slave current for driving the at least one group of slave column pixels.

Description:
[0001]    This application claims the benefit of Taiwan application Ser. No. 95112733, filed Apr. 10, 2006, the subject matter of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates in general to an active matrix organic light emitting diode (AMOLED) display device, and more particularly to an AMOLED display device with uniformed current. 
         [0004]    2. Description of the Related Art 
         [0005]    It is essential for a current driven active light emitting diode that the source driver must be able to provide a stable current source. That is, the currents, corresponding to the same grey level value, provided by all the channels of the source drivers must be very close and the reverse in grey level value is not permitted between neighboring channels of the source drivers. When the same source driver is used, the above object can be achieved by the device matching or improving circuit configuration. However, when many source drivers are used to provide the current sources at the same time, device matching is not applicable among many source drivers. 
         [0006]    Referring to  FIG. 1 , a perspective of a conventional AMOLED display device is shown. In the AMOLED display device  10 , the panel  12  has many column pixels, and the source drivers  141 ˜ 14   n  respectively receive a reference current Iref to drive corresponding column pixels. Due to the manufacturing factors, the currents received by the source driver  141 ˜ 14   n  to drive the corresponding column pixels may deviate from the reference current Iref by ΔI 1 ˜ΔIn. For example, the current I 1  received by the source driver  141  to drive the corresponding column pixels should be Iref, but is now equal to I 1 =Iref+ΔI 1 . As the currents vary largely, the grey level values of neighboring source drivers may reverse. Consequently, despite the panel  12  has excellent pixel circuit compensation, the AMOLED display device  10  still may display an erroneous frame because the currents provided by the source driver  141 ˜ 14   n  are not uniformed. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention is directed to an active matrix organic light emitting diode (AMOLED) display device. According to the AMOLED display device of the invention, currents are connected in parallel such that the difference between the currents outputted by different source drivers is reduced, hence achieving uniformed currents. 
         [0008]    According to a first aspect of the present invention, an AMOLED display device including a panel, a master source driver and at least one slave source driver is provided. The panel has a group of master column pixels and at least one group of slave column pixels. The master source driver receives a reference current and duplicates the reference current to output a master current for driving the group of master column pixels. The at least one slave source driver, coupled to the master source driver or a preceding slave source driver, duplicates the master current or a slave current outputted by the preceding slave source driver to output a new slave current for driving the at least one group of slave column pixels. 
         [0009]    According to a second aspect of the present invention, an AMOLED display device including a panel, a master source driver and at least one slave source driver is provided. The panel has a group of master column pixels and at least one group of slave column pixels. The master source driver receives a reference current and duplicates the reference current as a master current and at least one slave current to output the master current for driving the group of master column pixels. The at least one slave source driver, coupled to the master source driver or a preceding slave source driver, receives one of the at least one slave current and outputs a new slave current for driving the second column pixels. 
         [0010]    According to a third aspect of the present invention, an AMOLED display device including a panel, a current source circuit and a plurality of source drivers is provided. The panel has many groups of column pixels. The current source circuit receives a reference current and duplicates the reference current to output a master current. Each source driver, coupled to current source circuit, duplicates the master current as a plurality of slave currents and outputs the slave currents for driving each group of column pixels. 
         [0011]    According to a fourth aspect of the present invention, an AMOLED display device including a panel, a master source driver and at least one slave source driver is provided. The panel having many groups of column pixels includes a group of master column pixels and at least one group of slave column pixels. The master source driver receives a reference current and duplicates the reference current to output a master current, and refers to both the master current and a first calibration current transmitted back by a neighboring slave source driver to output a master data current for driving the group of master column pixels. The master data current is an average current of the master current and first calibration current. Each slave source driver, coupled to the master source driver or a preceding slave source driver, duplicates the master current or a slave current outputted by the preceding slave source driver as a new slave current, and refers to both the new slave current and a second calibration current transmitted back by a subsequent slave source driver to output at least one slave data current for driving each group of slave column pixels. The at least one slave data current is an average current of the new slave current and the second calibration current transmitted back by the subsequent source driver. 
         [0012]    The invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  (PriorArt) is a perspective of a conventional AMOLED display device; 
           [0014]      FIG. 2  is a perspective of an AMOLED display device according to a first embodiment of the invention; 
           [0015]      FIG. 3  is a perspective of an AMOLED display device according to a second embodiment of the invention; 
           [0016]      FIG. 4  is a perspective of an AMOLED display device according to a third embodiment of the invention; and 
           [0017]      FIG. 5  is a perspective of an AMOLED display device according to a fourth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    According to the AMOLED display device of the invention, currents are connected in parallel such that the difference between the currents outputted by different source drivers is reduced, hence achieving uniformed currents. The invention is exemplified by an AMOLED display device having three source drivers, but is not limited thereto. The AMOLED display device having more source drivers is still within the scope of protection of the invention. 
         [0019]    Referring to  FIG. 2 , a perspective of an AMOLED display device according to a first embodiment of the invention is shown. As indicated in the diagram, in the AMOLED display device  20 , the panel  22  has a first group of column pixels, a second group of column pixels and a third group of column pixels driven by a master source driver  24 , a slave source driver  26  and a slave source driver  28  respectively. The master source driver  24  receives a reference current Iref and duplicates the reference current Iref to output a master current Im for driving the first group of column pixels. The slave source driver  26 , coupled to the master source driver  24 , duplicates the master current Im as a first slave current Is 1  and outputs the first slave current Is 1  for driving the second group of column pixels. The slave source driver  28 , coupled to slave source driver  26 , duplicates the first slave current Is 1  as a second slave current Is 2  and outputs the second slave current Is 2  for driving the third group of column pixels. 
         [0020]    All the currents in the AMOLED display device  20  are transmitted via a printed circuit board (not shown in the diagram) or a glass substrate (not shown in the diagram) inside the AMOLED display device  20 . 
         [0021]    Referring to  FIG. 3 , a perspective of an AMOLED display device according to a second embodiment of the invention is shown. As indicated in the diagram, in the AMOLED display device  30 , the panel  32  has a first group of column pixels, a second group of column pixels and a third group of column pixels driven by a master source driver  34 , a slave source driver  36  and a slave source driver  38  respectively. The master source driver  34  receives a reference current Iref and duplicates the reference current Iref as a master current Im, a first slave current Is 1  and a second slave current Is 2  and outputs the master current Im for driving the first group of column pixels. The slave source driver  36 , coupled to the master source driver  34 , receives and outputs the first slave current Is 1  for driving the second group of column pixels. The slave source driver  38 , coupled to the master source driver  34 , receives and outputs the second slave current Is 2  for driving the third group of column pixels. 
         [0022]    All the currents in the AMOLED display device  30  are transmitted via a printed circuit board (not shown in the diagram) or a glass substrate (not shown in the diagram) inside the AMOLED display device  30 . 
         [0023]    Referring to  FIG. 4 , a perspective of an AMOLED display device according to a third embodiment of the invention is shown. As indicated in the diagram, in the AMOLED display device  40 , the panel  42  has a first group of column pixels, a second group of column pixels and a third group of column pixels driven by a slave source driver  46 , a slave source driver  48  and a slave source driver  49  respectively. The current source circuit  44  of the AMOLED display device  40  receives a reference current Iref and duplicates the reference current Iref to output many identical master currents Im. The slave source driver  46 , coupled to the current source circuit  44 , duplicates a master current Im as a first slave current Is 1  and outputs the first slave current Is 1  for driving the first group of column pixels. The slave source driver  48  and the slave source driver  49 , both coupled to the current source circuit  44 , duplicate the other master currents Im as a second slave current Is 1  and a third slave current Is 2  and output the first slave current Is 1  and the third slave current Is 2  for driving the second group and the third group of column pixels. 
         [0024]    All the currents in the AMOLED display device  40  are transmitted via a printed circuit board (not shown in the diagram) or a glass substrate (not shown in the diagram) inside the AMOLED display device  40 . 
         [0025]    Unlike the conventional practice in which the source driver individually receives a reference current Iref hence resulting in deviation, the current outputted by each source driver of the AMOLED display device disclosed in the above embodiments of the invention refers to the same reference current Iref and duplicates many identical master currents Im. Consequently, the difference between currents is very small, and the uniformity in the currents of the overall AMOLED display device is improved. 
         [0026]    In order to further improve the uniformity in the currents of the overall AMOLED display device, a calibration mechanism can be introduced to the AMOLED display device. Referring to  FIG. 5 , a perspective of an AMOLED display device according to a fourth embodiment of the invention is shown. As indicated in the diagram, in the AMOLED display device  50 , the panel  52  has a first group of column pixels, a second group of column pixels and a third group of column pixels driven by a master source driver  54 , a slave source driver  56  and a slave source driver  58  respectively. 
         [0027]    The master source driver  54  receives a reference current Iref and duplicates the reference current Iref to output a master current Im, and receives a first calibration current Ic 1  transmitted back by the slave source driver  56  to output a master data current Idata 1  for driving the first group of column pixels. The master data current Idata 1  is an average current of the master current Im and the first calibration current Ic 1 . 
         [0028]    The slave source driver  56 , coupled to the master source driver  54 , duplicates the master current Im as a first slave current Is 1 , and receives a second calibration current Ic 2  transmitted back by the slave source driver  58  to output a first slave data current Idata 1  for driving the second group of column pixels. The first slave data current Idata 1  is an average current of of the first slave current Is 1  and the second calibration current Ic 2 . 
         [0029]    The slave source driver  58 , coupled to slave source driver  56 , duplicates the first slave current Is 1  and a second slave current Is 2  and transmits the second calibration current Ic 2  to the master source driver  54  according to the second slave current. The second slave current Is 2  is substantially equal to the second calibration current Ic 2 . The slave source driver  58  outputs a second slave data current Idata 2  for driving many third column pixels. The second slave data current Idat 2  is an average current of the second slave current Is 2  and the second calibration current Ic 2 . That is, the second slave data current Idata 2  is substantially equal to the second slave current Is 2 . 
         [0030]    All the currents in the AMOLED display device  50  are transmitted via a printed circuit board (not shown in the diagram) or a glass substrate (not shown in the diagram) inside the AMOLED display device  50 . As each source driver has a calibration current, the difference between the currents outputted by each source driver is further reduced, and the uniformity in the currents of the overall AMOLED display device is further improved. 
         [0031]    According to the conventional practice, the source driver individually receives a reference current Iref hence causing deviation. According to the AMOLED display device disclosed in the above embodiments of the invention, the currents are connected in parallel and the same reference current is used, such that the difference between the currents outputted different source drivers is reduced, and the uniformity in the currents of the overall AMOLED display device is achieved. 
         [0032]    While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.