Scan Pulse Timing for Variable-Refresh Display Luminance
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Solution Overview
Problem
Existing display devices with variable refresh rate modes experience significant luminance deviations and flicker issues due to changes in driving frequency, particularly when transitioning between high and low frequencies, which degrade image quality.
Innovation Solution
Implementing a display device with a scan driver that provides first and second scan signals, including active and dummy pulses with varying intervals, and a controller that generates corresponding scan control signals to manage these pulses, ensuring consistent luminance by adjusting the time lengths of active and blank periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the driving frequency of the display panel is increased to improve image quality during moving image display, then image quality is improved, but power consumption increases
Solution Approach 1:
The patent implements variable refresh rate mode where the driving frequency of the display panel is dynamically adjusted based on the type of content being displayed. For moving images, higher refresh rates are used to improve image quality, while lower refresh rates are used for still images to reduce power consumption. This dynamic adaptation resolves the contradiction by allowing the system to optimize between image quality and power consumption based on actual usage conditions.
2Use of energy by moving object
If the driving frequency is changed to reduce power consumption, then power consumption is reduced, but luminance deviation and flicker occur degrading image quality
Solution Approach 1:
The patent introduces dummy pulses in the vertical blank period before the actual image display begins. These dummy pulses are generated in advance to pre-charge or pre-discharge the pixel capacitances, ensuring that the pixels are in a stable state before the actual image data is displayed. This preliminary action compensates for the luminance deviations that would otherwise occur when switching between different driving frequencies, maintaining consistent luminance while still enabling power savings through variable refresh rate mode.
3Illumination intensity
If dummy pulses are added in the vertical blank period to maintain luminance consistency, then luminance deviation is reduced, but the complexity of the scan control signal increases
Solution Approach 1:
The patent applies dummy pulses only during the vertical blank period, not during the entire scan cycle. The dummy pulses are strategically placed in the time interval between the active period and the next active period, specifically in the vertical blank period when no image data is being transmitted. This localized application of dummy pulses maintains luminance consistency without significantly increasing the overall complexity of the scan control signal, as the dummy pulses are confined to a specific temporal segment rather than affecting the entire scanning process.
Data Source
AI summary
A display device includes: a display panel including a pixel; a scan driver configured to provide a first scan signal and a second scan signal to the pixel; and a controller configured to provide a first scan control signal for generating the first scan signal and a second scan control signal for generating the second scan signal to the scan driver, wherein the second scan signal includes an active pulse in an active period having a constant time length and at least one dummy pulse in a vertical blank period having a variable time length, and wherein an interval between the active pulse and a first dummy pulse of the second scan signal is different from an interval between the first dummy pulse and a second dummy pulse of the second scan signal.