Display Panel Pixel Circuit Timing for Brightness-Uniformity Control
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Solution Overview
Problem
The threshold voltage shifting of drive transistors in pixel circuits due to internal characteristics changes over time, affecting display uniformity in display panels, especially at different brightness levels.
Innovation Solution
The display panel adjusts the duration of initialization and initialization writing phases differently in various brightness modes to balance the bias state of the drive transistor, thereby stabilizing the drive current and improving display uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive transistor operates continuously to provide drive current, then the display panel can maintain continuous display function, but threshold voltage shifting occurs due to internal characteristics changes, degrading display uniformity
Solution Approach 1:
The patent applies preliminary action by performing initialization before data writing in each frame. The initialization module resets the drive transistor threshold voltage to a reference value at the beginning of each frame, proactively preventing threshold voltage drift that would otherwise occur during continuous operation. This preliminary reset ensures display uniformity is maintained across all pixels before they begin their operational cycle.
Solution Approach 2:
The patent implements periodic action through frame-based initialization cycles. Since display panels operate continuously with refresh rates (e.g., 60Hz), the initialization module performs threshold voltage resetting at regular intervals corresponding to each frame period. This periodic initialization compensates for cumulative threshold voltage shifts that occur during continuous drive transistor operation, maintaining display uniformity over time.
2Reliability
If a fixed initialization duration is used across all brightness modes, then the circuit design is simplified, but display uniformity deteriorates at different brightness levels due to varying threshold voltage shifts
Solution Approach 1:
The patent applies dynamics by making the initialization duration adaptive rather than fixed. The initialization module adjusts the duration of the initialization phase based on the detected brightness mode. In high brightness modes where larger drive currents cause greater threshold voltage shifts, the initialization duration is extended. In low brightness modes, the initialization duration is shortened. This dynamic adjustment optimizes display uniformity across different operating conditions.
Solution Approach 2:
The patent implements parameter changes by varying the initialization time parameter according to brightness mode. The system detects the current brightness mode and changes the initialization duration parameter accordingly - using longer initialization periods for high brightness modes and shorter periods for low brightness modes. This parameter adaptation allows the system to compensate for brightness-dependent threshold voltage shifts without requiring completely different circuit architectures.
3Reliability
If the initialization phase duration is extended to compensate for threshold voltage shifts, then display uniformity is improved, but the frame time is consumed, reducing productivity
Solution Approach 1:
The patent resolves this contradiction through dynamic initialization duration adjustment. Rather than using a consistently long initialization phase that would consume excessive frame time, the system adapts the initialization duration to the actual needs of each brightness mode. High brightness modes receive longer initialization periods when threshold voltage shifts are most significant, while low brightness modes receive shorter periods when shifts are minimal. This dynamic approach maximizes display uniformity while minimizing unnecessary time consumption.
Solution Approach 2:
The patent changes the initialization time parameter based on brightness mode to balance uniformity and efficiency. By detecting the brightness mode and adjusting the initialization duration parameter accordingly, the system ensures sufficient initialization time is allocated only when needed (high brightness modes with larger threshold shifts), rather than wasting frame time on excessive initialization in low brightness modes where threshold voltage stability is less of an issue.
Data Source
AI summary
Provided are a display panel and a display device. The display panel includes a pixel circuit and a light-emitting element. In a data writing phase, a data writing module of the pixel circuit provides a data signal. In an initialization writing phase, an initialization module of the pixel circuit provides an initialization signal. In the same data writing frame, a time period between the start time of the initialization writing phase and the start time of the data writing phase is an initialization phase. The duration of the initialization phase in a first mode is different from the duration of the initialization phase in a second mode, and/or the duration of the initialization writing phase in a first mode is different from the duration of the initialization writing phase in a second mode.