Variable-Refresh Display Timing for Flicker-Free Low-Frequency Driving
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Solution Overview
Problem
Display devices experience image quality deterioration such as distortion and flicker when driven at low frequencies due to voltage discharge, which occurs when there is little change in the input image, leading to issues during variable refresh rate modes.
Innovation Solution
The display device incorporates a counting circuit to measure the duration of the blanking period, a comparison circuit to assess if it meets threshold times for pixel sensing and driving preparation, and a delay decision circuit to adjust the blanking period duration accordingly, ensuring sufficient time for sensing and driving preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the pixels are driven at a low frequency to reduce power consumption, then power consumption is reduced, but image quality deteriorates due to voltage discharge causing distortion and flicker
Solution Approach 1:
The display device dynamically adjusts the blanking period duration based on the current frame rate. When operating at low refresh rates, the blanking period is extended to provide sufficient time for pixel sensing and driving preparation, preventing voltage discharge issues. This dynamic adaptation allows the system to maintain image quality across varying operating conditions while keeping power consumption low.
Solution Approach 2:
The extended blanking period provides advance preparation time for the next frame's pixel driving operations. By completing sensing and preparation activities during the blanking period before the active display period begins, the system ensures that pixels are ready for the next frame without requiring excessive current during the active period, thus maintaining image quality at low refresh rates.
2Reliability
If the blanking period duration is extended to ensure sufficient sensing and driving preparation time, then image quality is maintained, but the active display time is reduced
Solution Approach 1:
The system changes the blanking period parameter dynamically based on the operating refresh rate. At lower refresh rates where voltage discharge is more problematic, the blanking period is extended to ensure adequate sensing and preparation time. At higher refresh rates, the blanking period can be shortened, maximizing active display time. This parameter adaptation resolves the contradiction by optimizing the balance between preparation time and active display time for each operating condition.
3Use of energy by moving object
If the refresh rate is varied to optimize power consumption for different image types, then power efficiency is improved, but timing synchronization becomes more complex
Solution Approach 1:
The display device incorporates feedback mechanisms that monitor the current frame rate and automatically adjust the blanking period duration accordingly. The counting circuit tracks the timing of successive frames and provides feedback to the control logic, which then modifies the blanking period to maintain adequate sensing and preparation time. This closed-loop control simplifies the overall timing management by automatically adapting to variable refresh rates without requiring complex manual synchronization configurations.
Data Source
AI summary
A display device is disclosed that includes a display panel having pixels configured to display images during a first frame, a second frame, and a third frame, each of the first frame, the second frame, and the third frame including an active period and a blanking period; a counting circuit configured to count a duration of the blanking period of the first frame after the active period of the first frame; a comparison circuit configured to compare the counted duration of the blanking period of the first frame with a threshold time required for sensing at least one pixel or a threshold time required to prepare for driving the pixels during the second frame; and a delay decision circuit configured to determine whether to increase a duration of the blanking period of the first frame based on the comparison.