Pixel circuit and display device

Abstract

In at least one embodiment, an electrooptic element is connected between a first power supply wire and a second conducting terminal of a driving transistor. A first conducting terminal of the driving transistor is connected to a second power supply wire. The second conducting terminal of the driving transistor is connected through a first switching transistor to a control terminal of the driving transistor. A control terminal of the first switching transistor is connected to a control wire. The control terminal of the driving transistor is connected through a first capacitor to a node. The node is connected through a second switching transistor to a data line. A control terminal of the second switching transistor is connected to a scanning line. The node is connected through a second capacitor to a third power supply wire. The constitution realizes a pixel circuit that allows freely setting a period for compensation of the threshold voltage of a driving TFT and further reducing power consumption.

1 . A pixel circuit, disposed so as to correspond to each intersection between a scanning line and a data line, which includes a current-driven electrooptic element and to which a display signal corresponding to a driving current of the electrooptic element is written through the data line, the pixel circuit comprising:
 first and second power supply wires;   a third power supply wire for supplying a constant voltage;   a driving transistor for determining, in accordance with the display signal, a current that is passed through a first path connecting the first power supply wire with the second power supply wire;   first and second switching elements; and   first and second capacitors,   the driving transistor and the electrooptic element being connected in series on the first path, the first switching element being provided between gate and drain terminals of the driving transistor, the first capacitor and the second switching element being connected in series in this order between the gate terminal of the driving transistor and the data line, the gate terminal of the driving transistor being connected through the second capacitor to the third power supply wire,   a first end of the second capacitor being connected between the first capacitor and the second switching element and a second end of the second capacitor being connected to the third power supply wire or a first end of the second capacitor being connected between the gate terminal of the driving transistor and the first capacitor and a second end of the second capacitor being connected to the third power supply wire.   
   
   
       2 . The pixel circuit as set forth in  claim 1 , further comprising a third switching element connected between (i) the third power supply wire and (ii) a point between the first capacitor and the second switching element, wherein
 the first end of the second capacitor is connected between the first capacitor and the second switching element and the second end of the second capacitor is connected to the third power supply wire.   
   
   
       3 . The pixel circuit as set forth in  claim 1 , further comprising a third switching element connected between (i) the third power supply wire and (ii) a point between the first capacitor and the second switching element, wherein
 the first end of the second capacitor is connected between the gate terminal of the driving transistor and the first capacitor and the second end of the second capacitor is connected to the third power supply wire.   
   
   
       4 . The pixel circuit as set forth in  claim 1  wherein the third power supply wire is the first power supply wire. 
   
   
       5 . The pixel circuit as set forth in  claim 1  wherein a voltage applied to the electrooptic element is reverse-biased during a period in which a gate-source voltage of the driving transistor is set to a threshold voltage of the driving transistor. 
   
   
       6 . The pixel circuit as set forth in  claim 1  wherein a voltage applied to the electrooptic element is less than a light-emitting threshold voltage of the electrooptic element during a period in which a gate-source voltage of the driving transistor is set to a threshold voltage of the driving transistor. 
   
   
       7 . A pixel circuit, disposed so as to correspond to each intersection between a scanning line and a data line, which includes a current-driven electrooptic element, the pixel circuit comprising:
 first to third power supply wires;   a control wire;   a driving transistor;   first and second switching transistors; and   first and second capacitors,   the electrooptic element being connected between the first power supply wire and a second conducting terminal of the driving transistor, a first conducting terminal of the driving transistor being connected to the second power supply wire, the second conducting terminal of the driving transistor being connected through the first switching transistor to a control terminal of the driving transistor, a control terminal of the first switching transistor being connected to the control wire, the control terminal of the driving transistor being connected through the first capacitor to a node, the node being connected through the second switching transistor to the data line, a control terminal of the second switching transistor being connected to the scanning line, the node being connected through the second capacitor to the third power supply wire.   
   
   
       8 . The pixel circuit as set forth in  claim 5 , further comprising a third switching transistor, wherein:
 the node is connected through the third switching transistor to the third power supply wire; and   a control terminal of the third switching transistor is connected to the control wire.   
   
   
       9 . A pixel circuit, disposed so as to correspond to each intersection between a scanning line and a data line, which includes a current-driven electrooptic element, the pixel circuit comprising:
 first to third power supply wires;   a control wire;   a driving transistor;   first and second switching transistors; and   first and second capacitors,   the electrooptic element being connected between the first power supply wire and a second conducting terminal of the driving transistor, a first conducting terminal of the driving transistor being connected to the second power supply wire, the second conducting terminal of the driving transistor being connected through the first switching transistor to a control terminal of the driving transistor, a control terminal of the first switching transistor being connected to the control wire, the control terminal of the driving transistor being connected to a first node, the first node being connected through the first capacitor to a second node, the second node being connected through the second switching transistor to the data line, a control terminal of the second switching transistor being connected to the scanning line, the first node being connected through the second capacitor to the third power supply wire.   
   
   
       10 . The pixel circuit as set forth in  claim 9 , further comprising a third switching transistor, wherein
 the second node is connected through the third switching transistor to the third power supply wire; and   a control terminal of the third switching transistor is connected to the control wire.   
   
   
       11 . The pixel circuit as set forth in  claim 7  further comprising a period between a point of time where a current is passed through the driving transistor by the first and second capacitors' being charged from a source line in a state where the first switching transistor is ON and a point of time where a potential of the control terminal of the driving transistor is changed to take on a value at which the driving transistor is turned OFF. 
   
   
       12 . The pixel circuit as set forth in  claim 8  further comprising a period between a point of time where a current is passed through the driving transistor by the first and second capacitors' being charged from the third power supply wire in a state where the first switching transistor is ON and a point of time where a potential of the control terminal of the driving transistor is changed to take on a value at which the driving transistor is turned OFF. 
   
   
       13 . The pixel circuit as set forth in  claim 11  wherein during the period, a voltage applied to the electrooptic element takes on a value to be reverse-biased or a value less than a light-emitting threshold voltage. 
   
   
       14 . The pixel circuit as set forth in  claim 1  wherein the electrooptic element is an organic EL element. 
   
   
       15 . The pixel circuit as set forth in  claim 1  wherein at least the driving transistor is constituted by an insulated gate field effect transistor. 
   
   
       16 . The pixel circuit as set forth in  claim 1  wherein each of the driving transistor and the switching elements is constituted by a thin-film transistor. 
   
   
       17 . The pixel circuit as set forth in  claim 16 , wherein the thin-film transistor is made of amorphous silicon. 
   
   
       18 . The pixel circuit as set forth in  claim 1  wherein each of the switching elements is constituted by an n-channel transistor. 
   
   
       19 . A display device including a pixel circuit as set forth in  claim 1 , the display device comprising:
 a scanning signal output circuit; and   a display signal output circuit,   the pixel circuit being made writable by a scanning signal outputted from the scanning signal output circuit to the scanning line, a display signal corresponding to a driving current of the electrooptic element being written from the display signal output circuit through the data line to the pixel circuit thus made writable.   
   
   
       20 . The pixel circuit as set forth in  claim 9 , further comprising a period between a point of time where a current is passed through the driving transistor by the first and second capacitors' being charged from a source line in a state where the first switching transistor is ON and a point of time where a potential of the control terminal of the driving transistor is changed to take on a value at which the driving transistor is turned OFF. 
   
   
       21 . The pixel circuit as set forth in  claim 10 , further comprising a period between a point of time where a current is passed through the driving transistor by the first and second capacitors' being charged from the third power supply wire in a state where the first switching transistor is ON and a point of time where a potential of the control terminal of the driving transistor is changed to take on a value at which the driving transistor is turned OFF. 
   
   
       22 . The pixel circuit as set forth in  claim 12 , wherein during the period, a voltage applied to the electrooptic element takes on a value to be reverse-biased or a value less than a light-emitting threshold voltage. 
   
   
       23 . The pixel circuit as set forth in  claim 20 , wherein during the period, a voltage applied to the electrooptic element takes on a value to be reverse-biased or a value less than a light-emitting threshold voltage. 
   
   
       24 . The pixel circuit as set forth in  claim 21 , wherein during the period, a voltage applied to the electrooptic element takes on a value to be reverse-biased or a value less than a light-emitting threshold voltage. 
   
   
       25 . The pixel circuit as set forth in  claim 7 , wherein the electrooptic element is an organic EL element. 
   
   
       26 . The pixel circuit as set forth in  claim 9 , wherein the electrooptic element is an organic EL element. 
   
   
       27 . The pixel circuit as set forth in  claim 7 , wherein at least the driving transistor is constituted by an insulated gate field effect transistor. 
   
   
       28 . The pixel circuit as set forth in  claim 9 , wherein at least the driving transistor is constituted by an insulated gate field effect transistor. 
   
   
       29 . A display device including a pixel circuit as set forth in  claim 7 , the display device comprising:
 a scanning signal output circuit; and   a display signal output circuit,   the pixel circuit being made writable by a scanning signal outputted from the scanning signal output circuit to the scanning line, a display signal corresponding to a driving current of the electrooptic element being written from the display signal output circuit through the data line to the pixel circuit thus made writable.   
   
   
       30 . A display device including a pixel circuit as set forth in  claim 9 , the display device comprising:
 a scanning signal output circuit; and   a display signal output circuit,   the pixel circuit being made writable by a scanning signal outputted from the scanning signal output circuit to the scanning line, a display signal corresponding to a driving current of the electrooptic element being written from the display signal output circuit through the data line to the pixel circuit thus made writable.