Color-Specific Pixel Sensing Circuit for Threshold Voltage Drift
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Solution Overview
Problem
Existing display devices face challenges in accurately sensing the electrical characteristics of pixels due to variations caused by process variation and aging, which affect the threshold voltage of driving transistors and light-emitting elements.
Innovation Solution
The display device incorporates a sensing unit with a sensing capacitor and initialization switches connected to sub-sensing lines, applying different initialization voltages to sub-pixels emitting different colors, and using selection switches to generate sensing data based on driving currents during blank intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single initialization voltage is applied to all sub-pixels, then the device complexity is reduced, but the measurement precision of electrical characteristics deteriorates due to inability to compensate for color-specific variations
Solution Approach 1:
The sensing unit is segmented into multiple independent initialization switches (first initialization switch, second initialization switch, third initialization switch) corresponding to different color sub-pixels (red, green, blue). Each switch can be independently controlled to apply initialization voltage only to its corresponding color group, enabling color-specific sensing while maintaining a modular and manageable structure.
Solution Approach 2:
Different initialization voltages are applied locally to different color sub-pixels based on their specific electrical characteristics. The first initialization voltage is applied to red sub-pixels, the second to green sub-pixels, and the third to blue sub-pixels, allowing each color group to be optimized for its unique threshold voltage variations without affecting other colors.
2Measurement precision
If multiple initialization voltages are applied to different color sub-pixels, then the measurement precision of electrical characteristics is improved, but the device complexity increases due to additional initialization switches and sensing lines
Solution Approach 1:
The sensing unit is designed to serve multiple functions: it can sense electrical characteristics of different color sub-pixels, compensate for threshold voltage variations, and operate during blank intervals without affecting normal display operation. The same sensing unit structure handles all color groups through multiplexed initialization switches and sensing lines, reducing overall system complexity despite the multi-voltage capability.
Solution Approach 2:
Initialization voltages are applied in advance during the blank interval before the actual sensing operation. This preliminary action prepares the sub-pixels by establishing known initial conditions (zero voltage across the sensing capacitor) before measurement begins, ensuring accurate sensing of electrical characteristics without interference from previous frame operations.
3Productivity
If sensing operation is performed during active interval, then the productivity is improved, but the reliability of sensing data deteriorates due to ongoing light emission and current flow
Solution Approach 1:
The sensing operation is performed periodically during the blank interval between frames, not continuously during the active display interval. This periodic sensing allows the display to complete its normal light emission function first, then perform accurate electrical characteristic measurement during the naturally occurring blank period, ensuring both display productivity and sensing reliability.
Solution Approach 2:
The sensing operation is skipped during the active display interval when light emission and current flow interfere with measurement accuracy. Instead, the sensing is rushed through during the blank interval when the display is naturally inactive, avoiding interference from ongoing light emission and establishing stable electrical conditions for accurate measurement.
Data Source
AI summary
A display device includes a display panel including blocks, each including sub-pixels, and a sensing unit connected to a first block among the blocks via a sensing line and including a sensing capacitor. The sensing line includes a first sub-sensing line connected to sub-pixels which emit light in a first color among sub-pixels included in the first block and a second sub-sensing line connected to sub-pixels which emit light in a second color among the sub-pixels included in the first block. The sensing unit includes a first initialization switch connected between a first initialization voltage node, to which a first initialization voltage is applied, and the first sub-sensing line and a second initialization switch connected between a second initialization voltage node, to which a second initialization voltage is applied, and the second sub-sensing line, and the first initialization voltage and the second initialization voltage may be different from each other.