Systems and method for fast compensation programming of pixels in a display

• US 10,134,335 B2
• Filed: 10/12/2017
• Issued: 11/20/2018
• Est. Priority Date: 12/09/2008
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza, Azizi, Yaser, Ma, Maran Ran, Nathan, Arokia
• Primary Examiner(s): Tzeng, Fred
• Application Number:
  US15/730,920
• Publication Number:
  US 20180033368A1
• Time in Patent Office: 404 Days
• Field of Search: 345212
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]

Abstract

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.

Claims

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.