Pixel Scan Timing Control for Low-Flicker Variable-Refresh Displays
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Solution Overview
Problem
Existing display devices experience issues with power consumption and image quality, including noticeable image flicker and distortion due to driving current leakage and changes in frame frequency or frame response speed.
Innovation Solution
The display device incorporates a pixel structure with multiple transistors and capacitors, along with a scan driver and emission driver, to control the timing and voltage supply to sub-pixels, allowing for variable frame frequencies and reduced power consumption by optimizing the driving current and minimizing voltage differences between nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the driving frequency is lowered to reduce power consumption, then power consumption is reduced, but image quality deteriorates due to driving current leakage and flicker
Solution Approach 1:
The patent applies preliminary action by performing bias scanning before the main scanning period. Specifically, a bias scan signal is applied to the bias scan line before the data scan signal, allowing the pixel circuit to be pre-configured with appropriate bias currents. This preliminary biasing action ensures that when the main scanning occurs at lower frequencies, the driving current remains stable and prevents flicker, thus maintaining image quality while enabling reduced power consumption through lower driving frequency.
Solution Approach 2:
The patent implements feedback through the emission control signal that dynamically adjusts the emission current based on the scan signal timing. The emission control signal is generated in response to the scan signal and controls the emission current to match the driving frequency requirements. This feedback mechanism allows the system to automatically adjust current levels to maintain image quality across varying driving frequencies, resolving the contradiction between power consumption and image quality.
2Adaptability or versatility
If the frame frequency is changed to adapt to various conditions, then adaptability is improved, but image distortion and flicker increase due to voltage differences between nodes
Solution Approach 1:
The patent applies dynamics by making the scan signal generation adaptive to different frame frequencies. The scan driver generates scan signals based on the required frame frequency, allowing the system to dynamically adjust the timing and duration of scanning periods. This dynamic adjustment enables the display to operate at various frame frequencies (e.g., 60Hz, 120Hz) while maintaining image clarity by synchronizing the scanning process with the desired refresh rate, thus improving adaptability without compromising image quality.
Solution Approach 2:
The patent utilizes parameter changes by modifying the voltage levels and timing parameters of scan signals based on the emission control signal. When the emission control signal indicates a need for adjusted framing, the system changes the voltage parameters of the scan signals to compensate for potential voltage differences between nodes. This parameter adjustment ensures that the driving current remains stable across different frame frequencies, preventing image distortion and maintaining clarity while achieving frame frequency adaptability.
3Reliability
If multiple scan signals are supplied in non-emission periods, then driving current stability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the scan driver to perform multiple functions through a unified control mechanism. The scan driver generates different types of scan signals (bias scan signals and data scan signals) based on the emission control signal, allowing a single driver circuit to handle multiple scanning tasks. This multi-functional approach improves driving current stability by providing comprehensive biasing and data scanning while avoiding the need for separate dedicated circuits for each scanning function, thus managing device complexity effectively.
Data Source
AI summary
A display device includes a pixel including a light emitting element and a first transistor connected between a first node and a second node and generating a driving current. The pixel is connected to a first scan line, a second scan line, a third scan line, a fourth scan line, a fifth scan line, an emission control line, and a data line. The display device further includes an emission driver that supplies an emission control signal to the emission control line, a scan driver that supplies first to fifth scan signals respectively to the first to fifth scan lines in a period in which the emission control signal is supplied, and a data driver that supplies a data signal to the data line. The first scan signal controls a timing at which the second node and a first electrode of the light emitting element are connected to each other.