Active Panel Conditioning for AMOLED Hysteresis Artifacts
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Solution Overview
Problem
LED displays, such as AMOLED and μLED, suffer from visual artifacts like image retention and ghost images due to hysteresis in driver TFTs, which cause previous images to persist on the screen after they have been turned off.
Innovation Solution
Active panel conditioning is applied to the display when it is off, using a common mode waveform or fixed bias voltage to accelerate the settling of hysteresis in driver TFTs, thereby reducing the time images remain visible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If driver TFTs are used to regulate voltage and current in LED displays, then the display can be controlled and operated, but hysteresis in the driver TFTs causes visual artifacts such as image retention and ghost images to appear
Solution Approach 1:
The patent applies preliminary action by implementing a conditioning phase before normal display operation. During this conditioning phase, a conditioning voltage is applied to the driver TFTs to reset their hysteresis state and eliminate residual charges. This preliminary reset action prevents visual artifacts from appearing in the subsequent display operation, thereby maintaining both ease of operation and eliminating harmful visual artifacts.
2Use of energy by moving object
If the display is left off to save power, then energy consumption is reduced, but previous images remain visible on the display due to hysteresis settling time
Solution Approach 1:
The patent applies periodic action by implementing a conditioning voltage applied at regular intervals or at specific moments (such as when the display transitions from off to on, or at predetermined time intervals). This periodic conditioning resets the hysteresis state of the driver TFTs without requiring continuous power application, thereby reducing overall power consumption while minimizing image retention time when the display is off.
3Object-generated harmful factors
If a conditioning voltage is applied to accelerate hysteresis settling, then visual artifacts are reduced, but additional power is consumed during the conditioning process
Solution Approach 1:
The conditioning voltage is applied in advance during a dedicated conditioning phase before normal display operation begins. This preliminary action eliminates visual artifacts proactively, so that no additional power is needed during normal operation to correct artifacts. The energy cost is confined to a brief conditioning period rather than continuous consumption.
Solution Approach 2:
The conditioning voltage is applied periodically or at specific transition moments rather than continuously. This periodic application accelerates hysteresis settling at critical moments when visual artifacts are most likely to occur, while minimizing the total time and energy spent in the high-power conditioning state. The display operates normally between conditioning cycles without additional power consumption for artifact reduction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces or eliminates visual artifacts by quickly removing previous image content from the display, improving the overall clarity and usability of LED displays.
Implementation Method 1
One cause of this particular type of visual artifact may be hysteresis of driver TFTs of the display (e.g., a lag between a present input and a past input affecting the operation of the driver TFTs, thereby allowing current to pass to an LED to cause light emissions therefrom)
Data Source
AI summary
An electronic device comprises a controller. The controller is configured to provide a first signal to a display of the electronic device to turn off the display. The controller is also configured to provide a second signal to the display to alter a gate source voltage of a drive transistor coupled to a light emitting diode (LED) of a pixel of the display while the display is turned off.