Data Driver Sensing Transistor Mobility in OLED Panels
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in precisely sensing and compensating for characteristic deviations in driving transistors, particularly mobility, due to variations in driving time, leading to brightness deviations and reduced image quality.
Innovation Solution
The implementation of a data driver and organic light emitting display panel design that allows for simultaneous output of sensing data voltages to multiple data lines, using a sensing line to measure transistor characteristics within a short sensing time at a low voltage without increasing transistor size, while achieving high resolution and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensing time is extended to improve measurement precision of driving transistor characteristics, then measurement precision is improved, but productivity deteriorates due to increased sensing time
Solution Approach 1:
The patent applies preliminary action by performing mobility sensing during the blanking period before the next frame is displayed. The sensing operation is prepared and executed in advance using the available time window, allowing precise measurement without extending the active display time. This enables the sensing to be completed before the frame deadline, maintaining both precision and productivity.
Solution Approach 2:
The patent implements periodic action by conducting mobility sensing at regular intervals during the blanking period of each frame. The sensing operation is periodically repeated using the available time windows between frames, allowing continuous monitoring of transistor characteristics without disrupting the normal display refresh cycle. This periodic approach ensures measurement precision while maintaining overall system productivity.
2Measurement precision
If voltage is increased to improve current capability for sensing, then measurement precision is improved, but object-generated harmful factors worsen due to increased stress on the driving transistor
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the sensing voltage based on the measured current level. When the driving transistor exhibits insufficient current capability, the sensing voltage is automatically increased to ensure adequate signal levels for precise measurement. Conversely, when current capability is sufficient, the voltage is reduced to minimize stress on the transistor. This adaptive voltage adjustment resolves the contradiction between measurement precision and transistor stress.
3Productivity
If transistor size is increased to improve current capability, then productivity is improved through better sensing capability, but area of stationary object worsens due to larger transistor footprint
Solution Approach 1:
The patent applies parameter changes by adjusting the sensing voltage to compensate for small transistor size. Instead of increasing transistor area to improve current capability, the system dynamically modifies the sensing voltage parameter to ensure sufficient current flow for accurate measurement. This allows small transistors to maintain adequate sensing capability through voltage adjustment, resolving the contradiction between sensing capability and transistor area.
4Productivity
If sensing is performed on all data lines simultaneously to improve productivity, then productivity is improved, but device complexity worsens due to increased circuit requirements
Solution Approach 1:
The patent applies merging by combining multiple sensing operations into a single integrated circuit block. The mobility sensing circuit is designed to handle multiple data lines through shared components and multiplexed operation, allowing simultaneous or sequential sensing across all data lines without requiring separate dedicated circuits for each line. This integration improves productivity while controlling device complexity through component sharing.
Data Source
AI summary
The present exemplary embodiments relate to measurement of a characteristic of a driving transistor and sensing driving therefor. Provided are a data driver, an organic light emitting display panel, an organic light emitting display device, and a driving method thereof which are capable of measuring characteristics of a driving transistor even at a data voltage which is not so high within a short sensing time by simultaneously sensing the characteristics of the driving transistors for two or more sub pixels, among a plurality of sub pixels commonly connected to the sensing lines, while measuring characteristics (for example, a threshold voltage or a mobility) of the driving transistor.