OLED Driving Transistor Threshold Voltage Noise Offset
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Solution Overview
Problem
Existing organic light emitting displays face challenges in accurately extracting threshold voltage information from driving transistors due to noise currents, such as leakage and coupling noise, which affect the stability and accuracy of compensation for variations in threshold voltage.
Innovation Solution
A compensation unit is introduced, comprising sensing units that offset noise currents from multiple data lines, using capacitors, a reference voltage generation unit, and a comparison unit to extract precise threshold voltage information by comparing voltage values across capacitors, allowing for stable compensation of the driving transistor's threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If noise currents from data lines are directly measured during threshold voltage extraction, then the extraction process is simple, but the measurement precision deteriorates due to leakage and coupling noise affecting the accuracy
Solution Approach 1:
The patent introduces a sensing unit as an intermediary component between the data lines and the measurement system. This sensing unit includes capacitors that couple to multiple data lines and a comparison unit that processes the signals, thereby mediating the measurement process to eliminate noise currents while extracting accurate threshold voltage information from the driving transistor
Solution Approach 2:
The patent extracts and separates the noise currents from the measurement process by using the sensing unit to identify and exclude leakage and coupling noise components. The comparison unit then processes only the valid signal components, effectively taking out the harmful noise elements from the measurement pathway to achieve precise threshold voltage extraction
2Productivity
If threshold voltage compensation is performed without noise offset, then the process speed is fast, but the reliability deteriorates due to unstable compensation caused by noise currents
Solution Approach 1:
The patent performs preliminary noise offsetting action before the actual threshold voltage extraction. The sensing unit first captures and processes noise currents from multiple data lines, and the comparison unit preliminarily compensates for these noise effects, thereby preparing a clean measurement baseline that ensures reliable threshold voltage compensation without requiring repeated measurements
3Measurement precision
If multiple data lines are monitored simultaneously for noise offset, then the measurement precision improves, but the device complexity increases due to additional sensing components
Solution Approach 1:
The sensing unit is designed with multi-functionality to monitor and process signals from multiple data lines simultaneously using a unified structure. The capacitors and comparison unit serve multiple purposes: coupling to different data lines, filtering noise, and performing comparative analysis, thereby achieving comprehensive noise offset accuracy without proportionally increasing device complexity
Data Source
AI summary
An organic light emitting display includes a plurality of pixels and a compensation unit. Each of the pixels includes a driving transistor to control an amount of current supplied to a corresponding organic light emitting diode. The compensation unit is coupled to the pixels by data lines and includes at least one sensing unit. The sensing unit extracts threshold voltage information from the pixels corresponding to respective driving transistors. The sensing unit receives noise currents from a plurality of data lines, offset the noise currents, and extracts the threshold voltage information after offset of the noise currents.