Display device, electronic device, and method of driving display device
View Patent ↗A display device is provided having improved reliability compared with the related art. The display device includes, for each pixel: a photo-emission element and a first MOS transistor connected in series between a first power source line and a second power source line; a capacitor connected to be inserted between a gate and a source of the first MOS transistor; and a second MOS transistor connected to be inserted between a signal line to be applied with a image signal voltage and the gate of the first MOS transistor, the second MOS transistor being controlled by a scan signal to change between ON-state and OFF-state, wherein ON-period of the first transistor is established within a period in which the photo-emission element is maintained to an extinction state and the signal line is applied with a voltage having a fixed level independent from the image signal voltage.
1. A display device, comprising:
a signal line configured to supply a variable signal to pixels, the variable signal being dependent on a luminance level of an image signal,
at least one of the pixels including:
a capacitor;
a photo-emission element; and
a transistor including an input node and an output node, the input node being configured to receive the variable signal, and
said one of the pixels being configured to:
execute a reset operation to apply an offset voltage to the capacitor that resets a signal stored in the capacitor;
execute a signal write operation to write the variable signal in the capacitor;
execute a light emission operation by the photo-emission element, the light emission being dependent upon the variable signal;
execute a refresh operation that applies a fixed voltage independent of the variable signal to the input node while the transistor is in a conductive state and while a fixed non-emission voltage is applied to the photo-emission element, such that the photo-emission element does not emit light; and
stop conduction of the transistor at a conclusion of the refresh operation.
2. The display device according to claim 1 , wherein executing the refresh operation prevents a characteristic shift of the transistor when a period, in which a variable voltage is at a high level, is dominant within an operation time.
3. The display device according to claim 1 , wherein applying the fixed voltage at a level that is not greater than a lowest level of a variable voltage to reduce a characteristic shift of the transistor when the variable voltage is at a high level.
4. The display device according to claim 1 , wherein the display device corresponds to a white display when a variable voltage is at a high level.
5. The display device according to claim 1 , wherein the transistor is a sampling transistor configured to sample the variable signal to the capacitor.
6. The display device according to claim 1 , wherein the transistor is a MOS transistor.
7. The display device according to claim 1 , wherein the input node and the output node of the transistor respectively correspond to a source electrode and a drain electrode.
8. The display device according to claim 1 , wherein said at least one pixel is configured to execute the refresh operation before the reset operation.
9. The display device according to claim 1 , wherein said at least one pixel is configured to execute in order the reset operation, the signal write operation, and the light emission operation.
10. A method for driving a pixel circuit including a capacitor, a photo-emission element, and a transistor of a display device, the method comprising:
applying a fixed potential to an input node of the transistor while the transistor is in a conductive state;
setting the transistor in a non-conductive state;
providing an offset voltage to the capacitor;
writing a variable signal to the capacitor, the variable signal being dependent on an luminance level of an image signal; and
making the photo-emission element emit light, the light emission being dependent upon the variable signal.
11. The method according to claim 10 , further comprising:
applying the fixed potential to prevent a characteristic shift of the transistor when a period, in which a variable voltage is at a high level, is dominant within an operation time.
12. The method according to claim 10 , further comprising:
applying the fixed voltage at a level that is not greater than a lowest level of a variable voltage to reduce a characteristic shift of the transistor when the variable voltage is at a high level.
13. The method according to claim 10 , wherein the writing of the variable signal further comprise:
continuously applying a voltage corresponding to the variable signal to the input node of the transistor.
14. The method according to claim 10 , wherein the fixed potential is independent of the variable signal.
15. The method according to claim 10 , further comprising:
compensating a voltage stored in the capacitor to enhance an uniformity of a screen of a display device that includes the pixel circuit.
16. The method according to claim 10 , wherein the transistor is a MOS transistor.
17. A pixel circuit including a capacitor, a photo-emission element, and a transistor of a display device, configured to:
apply a fixed potential to an input node of the transistor while the transistor is in a conductive state;
set the transistor in a non-conductive state;
provide an offset voltage to the capacitor;
write a variable signal to the capacitor, the variable signal being dependent on an luminance level of an image signal; and
make the photo-emission element emit light, the light emission being dependent upon the variable signal.
18. The pixel circuit according to claim 17 , the pixel circuit being configured to:
applying the fixed potential to prevent a characteristic shift of the transistor when a period, in which a variable voltage is at a high level, is dominant within an operation time.
19. The pixel circuit according to claim 17 , the pixel circuit being configured to:
apply the fixed voltage at a level that is not greater than a lowest level of a variable voltage to reduce a characteristic shift of the transistor when the variable voltage is at a high level.