Pixel circuit and display apparatus
A pixel circuit performs a threshold voltage correcting function. A sampling transistor becomes conductive in response to a control signal supplied from a scan line and samples a video signal supplied from a signal line to a pixel capacitor during a horizontal scanning period. The pixel capacitor applies an input voltage to a gate of a drive transistor in response to the sampled video signal. The drive transistor supplies an output current in accordance with the input voltage to a light-emitting device. A threshold voltage correcting period is provided to be part of the horizontal scanning period, to detect the threshold voltage of the drive transistor, and to write the threshold voltage in the pixel capacitor.
1. A display device comprising:
a plurality of scanning lines disposed in rows,
a plurality of signal lines disposed in columns, and
a plurality of pixels arranged at places where the scanning lines and the signal lines intersect; and
a control circuitry configured to drive the pixels through the scanning lines and the signal lines,
wherein each of the pixels arranged along an n-th row of the rows respectively includes:
a light emitting element
a capacitor;
a sampling transistor configured to supply a data signal from a corresponding one of the signal lines to the capacitor in response to a control signal supplied through a corresponding scanning line disposed in the n-th row;
a drive transistor configured to supply a drive current to the light emitting element according to a voltage stored in the capacitor; and
a switching transistor configured to connect the capacitor to a predetermined voltage line in response to a control signal supplied through a corresponding scanning line disposed in an (n-1)th row of the rows.
2. The display device according to claim 1 , wherein the sampling transistor is configured to turn on a plurality of times before the voltage stored in the capacitor becomes a threshold voltage that reflects a property of the drive transistor.
3. The display device according to claim 2 , wherein the drive transistor is configured to control a driving current from a power supply line to the light-emitting element depending on a potential held by the capacitor.
4. The display device according to claim 2 , wherein the switching transistor has a first terminal connected to the predetermined voltage line, and a second terminal connected to a first terminal of the capacitor.
5. The display device according to claim 2 , wherein a first pixel and a second pixel are connected to one of the signal lines,
wherein the control circuitry is configured to sequentially provide, through the signal line:
a predetermined signal in a first period;
a first video signal for the first pixel in a second period;
the predetermined signal in a third period; and
a second video signal for the second pixel in a fourth period,
wherein the control circuitry is configured to drive each of the first and second pixels so as to:
perform a correction operation such that the voltage stored in the capacitor reflects a property of the drive transistor; and
perform a sampling operation to sample a video signal,
wherein a period of the correction operation of the first and second pixels is divided into the first and the third periods.
6. The display device according to claim 5 , wherein the correction operation is performed during the first and third periods after the sampling transistor becomes conductive.
7. The display device according to claim 5 , wherein the correction operation is configured to detect the property of the drive transistor and to write the property in the capacitor in the first and third periods.
8. The display device according to claim 5 , wherein, during the second and fourth periods, the capacitor applies an input voltage to the drive transistor, the input voltage being a sum of a sampled video signal and the property of the drive transistor.