Pixel Pulse Timing for Temperature-Stable Display Luminance
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Solution Overview
Problem
The luminance of displayed images in display devices, such as liquid crystal and organic light emitting displays, varies with changes in ambient temperature or a user's finger temperature due to the changing characteristics of the transistors within the pixels.
Innovation Solution
A pixel design that includes a light emitting element, an emission transistor, and an initialization transistor, with specific timing of emission and initialization signals to maintain targeted luminance despite temperature changes, using a first and second pulse sequence for emission signals and a third and fourth pulse sequence for initialization signals, adjusting the timing points and widths of these pulses to stabilize luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the transistor characteristics change due to temperature variations, then the luminance of displayed images varies, but maintaining stable luminance requires complex signal timing control
Solution Approach 1:
The initialization transistor applies an initialization voltage to the anode electrode before the emission transistor activates, preparing the pixel circuit in advance to compensate for temperature-induced variations. This preliminary action ensures that the pixel starts from a known state, reducing the impact of temperature changes on luminance stability.
Solution Approach 2:
The emission signal includes multiple pulses (first pulse, second pulse) with specific timing relationships, and the initialization signal includes multiple pulses (third pulse, fourth pulse) that are periodically applied to the pixel circuit. This periodic pulse sequence allows for repeated compensation cycles, maintaining stable luminance despite temperature fluctuations.
2Productivity
If the emission signal pulse width is reduced to increase refresh rate, then productivity improves, but the time interval for initialization may be insufficient
Solution Approach 1:
The timing of the third pulse (initialization signal) is dynamically adjusted based on the end time point of the first pulse (emission signal). When the end time point of the first pulse changes, the start time point of the third pulse changes accordingly, ensuring that the time interval between them is maintained. This dynamic timing adjustment allows for faster refresh rates while ensuring sufficient initialization time.
Solution Approach 2:
The patent adjusts the timing parameters of the emission and initialization signals, specifically the end time point of the first pulse and the start time point of the third pulse, to optimize the balance between refresh rate and initialization time. By changing these temporal parameters, the system achieves higher productivity without sacrificing the necessary initialization duration.
Data Source
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AI summary
A pixel includes a light emitting element emitting light based on a driving current, an emission transistor passing and blocking the driving current when receiving an emission signal of a turn-on and turn-off level, and an initialization transistor supplying and not supplying an initialization voltage to the light emitting element when receiving an initialization signal of a turn-on and a turn-off level. The emission signal sequentially includes first and second pulses of a turn-on level, and the initialization signal sequentially includes third and fourth pulses of a turn-on level. The third pulse is generated in a period between the first pulse and the second pulse, the fourth pulse is generated after the second pulse. When an end time point of the first pulse changes, a start time point of the third pulse changes.