Systems and method for fast compensation programming of pixels in a display
Circuits for programming a circuit with decreased programming time are provided. Such circuits include a storage device such as a capacitor for storing display information and for ensuring a driving device such as a driving transistor drives a light emitting device according to the display information. To increase programming time, the pixel circuits may be pre-charged or a biasing current may be applied to charge and/or discharge a data line and/or the driving device. Aspects of the present disclosure allow for the biasing current to drain partially through the storage device to allow the portion of the biasing current applied to the driving device to remain small while the data line discharges. Furthermore, the present disclosure provides display architectures and operation schemes for display arranged in segments each including a plurality of pixel circuits.
1. A pixel circuit for coupling to a data line, a supply line and a monitor line to a light emitting device comprising:
a storage element coupled to the data line for storing a programming signal during a programming phase;
a drive device for conveying a drive current from the supply line to the light emitting device according to the programming signal to emit light at a desired amount of luminance during an emission phase;
an access switch for selectively connecting the storage element to the data line during the programming phase, and disconnecting the storage element from the data line during the emission phase; and
a monitoring system comprising a switch connected to the monitoring line for applying a reference current to the drive device during a compensation phase, between the emission and programming phases, to develop a calibration factor for modifying the programming signal.
2. The pixel circuit according to claim 1 , wherein the programming signal comprises a programming voltage; and wherein the calibration factor comprises a gate-to-source voltage of the drive device.
3. The pixel circuit according to claim 1 , wherein the compensation phase comprises a pre-charging phase and an adjustment phase;
wherein, during the pre-charging phase, the monitoring system is capable of pre-charging a capacitance of the monitor line; and
wherein, during the adjustment phase, the monitoring system is capable of adjusting the voltage on the data line via the drive device.
4. The pixel circuit according to claim 3 , wherein the monitoring system is capable of setting a voltage on the monitor line to a constant value to pre-charge the capacitance in the monitor line.
5. The pixel circuit according to claim 3 , wherein the monitoring system is capable of applying a reference current to the monitor line to pre-charge the capacitance in the monitor line.
6. A pixel circuit for coupling to a data line, a supply line and a monitor line to a light emitting device comprising:
a storage element coupled to the data line for storing a programming signal during a programming phase;
a drive device for conveying a drive current from the supply line to the light emitting device according to the programming signal to emit light at a desired amount of luminance during an emission phase;
an access switch for selectively connecting the storage element to the data line during the programming phase, and for disconnecting the storage element from the data source during the emission phase; and
a monitoring system connected to the data line for applying a reference current to the drive device during a compensation phase, between the emission and programming phases, to develop a calibration factor for modifying the programming signal.
7. The pixel circuit according to claim 6 , further comprising an emission switch connected to the emission line for connecting the drive device to the light emitting device during the emission phase, and for disconnecting the drive device from the light emitting device during the programming phase.
8. The pixel circuit according to claim 6 , further comprising:
a programming capacitor connected between the data line and the drive device for applying the reference current to the drive device via the access switch; and
a selection transistor connected between the programming capacitor and the drive device to isolate the drive device from the data line during the emission phase.
9. The pixel circuit according to claim 8 , wherein the monitoring system is capable of setting a reference voltage on the data line, and decreasing the reference voltage to generate a ramp voltage.
10. The pixel circuit according to claim 8 , wherein the drive device comprises a transistor comprising a gate connected to the storage element, a first terminal connected to the supply line, and a second terminal connect to the light emitting device; and
wherein the access switch comprises first and second transistors providing increased resistance to leakage between the gate and the second terminal of the drive device.
11. The pixel circuit according to claim 8 , wherein the access switch comprises an access transistor; and
wherein the access transistor is connected between the programming capacitor and the selection transistor for reducing leakage currents through the drive device, and enabling the programming capacitor to discharge to a capacitance of the light emitting device.
12. A display system comprising:
a controller for receiving digital data indicative of information to be displayed and for generating data signals and addressing signals;
a data driver and a plurality of data lines for receiving and transmitting programming signals;
an address driver for receiving and transmitting addressing signals;
a voltage supply and a plurality of supply lines for providing a voltage source;
a plurality of pixel circuits arranged in rows and columns, each pixel circuit comprising:
a storage element coupled to one of the data lines for storing a programming signal during a programming phase;
a drive device for conveying a drive current from one of the supply lines to the light emitting device according to the programming signal to emit light at a desired amount of luminance during an emission phase;
an access switch connected to the address driver for receiving addressing signals for selectively connecting the storage element to the data line during the programming phase, and for disconnecting the storage element from the data source during the emission phase; and
a monitoring system for applying a reference current to the drive device during a compensation phase, between the emission and programming phases, to develop a calibration factor for modifying the programming signal.
13. The display system according to claim 12 , wherein the monitoring system comprises a switch connected to the monitoring line for applying the reference current to the drive device during a compensation phase.
14. The display system according to claim 12 , further comprising:
a programming capacitor connected between the data line and the drive device of a row or column of the plurality of pixel circuits for applying the reference current to the drive device of each of the pixel circuits via their respective access switches; and
a selection transistor connected between the programming capacitor and the drive device to isolate the drive device from the programming capacitor during the emission phase.
15. The display system according to claim 14 , wherein the monitoring system is capable of setting a reference voltage on the data line, and decreasing the reference voltage to generate a ramp voltage.
16. The display system according to claim 14 , wherein the access switch comprises an access transistor; and
wherein the access transistor is connected between the programming capacitor and the selection transistor for reducing leakage currents through the drive device, and enabling the storage capacitor to discharge to a capacitance of the light emitting device.
17. The display system according to claim 12 , wherein the programming signal comprises a programming voltage; and wherein the calibration factor comprises a gate-to-source voltage of the drive device.
18. The display according to claim 17 , wherein the monitoring system is capable of setting a voltage on the monitor line to a constant value to pre-charge the capacitance in the monitor line.
19. The display according to claim 17 , wherein the monitoring system is capable of applying a reference current to the monitor line to pre-charge the capacitance in the monitor line.
20. The display system according to claim 12 , wherein the monitoring system comprises a plurality of monitoring lines;
wherein the compensation phase comprises a pre-charging phase and an adjustment phase;
wherein, during the pre-charging phase, the monitoring system is capable of pre-charging a capacitance of the monitor line; and
wherein, during the adjustment phase, the monitoring system is capable of adjusting the voltage on the data line via the drive device.