DEVICES AND METHODS FOR REDUCING OR ELIMINATING MURA ARTIFACT ASSOCIATED WITH WHITE IMAGES

• US 20160071452A1
• Filed: 07/08/2015
• Published: 03/10/2016
• Est. Priority Date: 09/05/2014
• Status: Abandoned Application

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Nho, Hyunwoo, Bae, Hopil, Yao, Wei H.
• Application Number:
  US14/794,344
• Publication Number:
  US 20160071452A1
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3674 Details of drivers for scan electrodes

Abstract

Devices and methods for reducing or eliminating image artifacts are provided. By way of example, a method of preventing an occurrence of an image artifact on a display panel may include generating a first gate signal to be supplied to a first gate of a first transistor, generating a second gate signal to be supplied to a second gate of a second transistor, and adjusting a falling edge rate of the first gate signal or a rising edge rate of the second gate signal to reduce a voltage drop associated with row pixels of the display panel. Adjusting the falling edge rate of the first gate signal or the rising edge rate of the second gate signal include decreasing the falling edge rate of the first gate signal or the rising edge rate of the second gate signal during a period of time in which the first gate signal falls.

Claims

1. A method, comprising:

generating a first gate signal to be supplied to a first gate of a first transistor;

generating a second gate signal to be supplied to a second gate of a second transistor; and

adjusting a falling edge rate of the first gate signal to reduce a voltage drop associated with pixels of a display panel, wherein adjusting the falling edge rate of the first gate signal comprises decreasing the falling edge rate of the first gate signal during a period of time in which the first gate signal falls and the second gate signal rises to prevent an occurrence of an image artifact on the display panel.

2. The method of claim 1, wherein generating the first gate signal to be supplied to the first gate of the first transistor comprises generating a positive polarity gate signal.

3. The method of claim 1, wherein generating the second gate signal to be supplied to the second gate of the second transistor comprises generating a negative polarity gate signal.

4. The method of claim 1, wherein decreasing the falling edge rate of the first gate signal comprises introducing a delay on the falling edge of the first gate signal.

5. The method of claim 4, wherein introducing the delay comprises introducing a delay of less than or equal to approximately 10 microseconds (μ

s).

6. The method of claim 4, wherein introducing the delay comprises introducing a delay of less than or equal to approximately 5 microseconds (μ

s).

7. The method of claim 4, wherein introducing the delay comprises introducing a delay of less than or equal to approximately 1 microsecond (μ

s).

8. The method of claim 1, comprising adjusting a rising edge rate of the second gate signal to reduce the voltage drop associated with the pixels of the display panel.

9. The method of claim 1, comprising supplying the adjusted first gate signal to the first gate of the first transistor and supplying the second gate signal to the second gate of the second transistor.

10. A method, comprising:

generating a first gate signal to be supplied to a first gate of a first transistor;

generating a second gate signal to be supplied to a second gate of a second transistor; and

adjusting a rising edge rate of the second gate signal to reduce a voltage drop associated with pixels of a display panel, wherein adjusting the rising edge rate of the second gate signal comprises decreasing the rising edge rate of the second gate signal during a period of time in which the first gate signal falls and the second gate signal rises to prevent an occurrence of an image artifact on the display panel.

11. The method of claim 10, wherein generating the first gate signal to be supplied to the first gate of the first transistor comprises generating a positive polarity gate signal.

12. The method of claim 10, wherein generating the second gate signal to be supplied to the second gate of the second transistor comprises generating a negative polarity gate signal.

13. The method of claim 10, wherein decreasing the rising edge rate of the second gate signal comprises controlling the second gate signal to rise from a predetermined negative voltage value to an intermediate voltage value for a period time before rising to a predetermined positive voltage value.

14. The method of claim 13, wherein controlling the second gate signal to rise to the intermediate voltage value comprises controlling the second gate signal to rise to a positive voltage value less than the predetermined positive voltage value.

15. The method of claim 10, comprising adjusting a falling edge rate of the first gate signal to reduce the voltage drop associated with the pixels of the display panel.

16. The method of claim 10, comprising supplying the adjusted second gate signal to the second gate of the second transistor and supplying the first gate signal to the first gate of the first transistor.

17. An electronic device, comprising:

gate line driving circuitry, comprising;

a first transistor configured to receive a first signal, wherein the first transistor is configured to activate during a positive cycle of the first signal, and wherein the first transistor is configured to cause the gate line driving circuitry to generate a first gate signal;

a second transistor coupled in series to the first transistor and configured to receive the first signal, wherein the second transistor is configured to activate during a negative cycle of the first signal, and wherein the second transistor is configured to cause the gate line driving circuitry to generate a second gate signal; and

a first diode coupled to the first transistor and a second diode coupled to the second transistor, wherein the first diode and the second diode are configured to provide a current discharge path to control a rate at which the first gate signal falls or the second gate signal rises.

18. The electronic device of claim 17, wherein the first diode and the second diode are configured to control the rate at which the first gate signal falls or the second gate signal rises during a period of time in which the first gate signal falls and the second gate signal rises concurrently.

19. The electronic device of claim 17, wherein first transistor comprises an n-channel metal oxide semiconductor (NMOS) transistor and the second transistor comprises a p-channel metal oxide semiconductor (PMOS) transistor.

20. The electronic device of claim 17, wherein the first diode and the second diode each comprises an electrostatic discharge (ESD) diode.

21. The electronic device of claim 17, wherein the first diode and the second diode are configured to provide the current discharge path during a period in which the second gate signal transitions from a predetermined negative voltage value to an intermediate voltage value, and to not provide the current discharge path during a period in which the second gate signal transitions from the intermediate voltage value to a predetermined positive voltage value.

22. An electronic display, comprising:

a pixel, including;

a pixel electrode;

a first thin-film transistor (TFT) having a first source coupled to a data line and a first gate coupled to a first gate line;

a second TFT having a second source coupled to a first drain of the first TFT, a second gate coupled to a second gate line, and a second drain coupled to the pixel electrode, wherein the first TFT and the second TFT are configured to pass image data to the pixel electrode; and

gate driver circuitry configured to supply a first gate signal to the first gate line and a second gate signal to the second gate line, wherein the gate driver circuitry is configured to modulate the second gate signal between a voltage substantially equal to and a voltage less than that of the first gate signal.

23. The electronic display of claim 22, wherein the gate driver circuitry is configured to modulate the second gate signal between the voltage substantially equal to and the voltage less than that of the first gate signal during a rise period of the first gate signal.

24. The electronic display of claim 22, wherein the gate driver circuitry is configured to modulate the second gate signal to reduce a possible voltage coupling between the first gate line and the second gate line.

25. The electronic display of claim 22, wherein the gate driver circuitry is configured to modulate the second gate signal during a display scan period.

26. The electronic display of claim 22, wherein the gate driver circuitry is configured not to modulate the second gate signal during a touch scan period.

27. A display panel, comprising:

a pixel array comprising a plurality of pixels; and

a gate driver configured to;

provide a first set of activation signals to a first set of the plurality of pixels;

provide a second set of activation signals to a second set of the plurality of pixels; and

adjust a falling edge rate of the first set of activation signals or a rising edge rate of the second set of activation signals to reduce a voltage drop associated with row common voltage electrodes (VCOMs) of the display panel, wherein adjusting the falling edge rate of the first set of activation signals or the rising edge rate of the second set of activation signals comprises delaying the falling edge rate of the first set of activation signals or the rising edge rate of the second set of activation signals during a period of time in which the first set of activation signals falls and the second set of activation signals rises.

28. The display panel of claim 27, wherein the gate driver is configured to delay the falling edge rate of the first set of activation signals or the rising edge rate of the second set of activation signals by approximately 10 microseconds (μ

s), approximately 5 μ

s, or approximately 1 μ

s.

29. The display panel of claim 27, wherein the gate driver is configured to delay the rising edge rate of the second set of activation signals by causing the second set of activation signals to increase from a negative voltage rail to an intermediate voltage for a period time before increasing to a positive voltage rail.

30. The display panel of claim 27, wherein the gate driver is configured to delay the falling edge rate of the first set of activation signals by causing the first set of activation signals to decrease from a positive voltage rail to an intermediate voltage for a period time before decreasing to a negative voltage rail.