Detection Circuit for AMOLED Brightness Uniformity
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Solution Overview
Problem
Active matrix organic light-emitting diode (AMOLED) displays face non-uniformity in brightness due to variations in threshold voltage of drive transistors and working voltage of OLED devices, leading to mura phenomena and artifacts, which existing compensation methods struggle to address effectively without accurate detection of these voltages.
Innovation Solution
A detection circuit comprising a switching unit, reset unit, and comparison unit that detects representative threshold voltages and working voltages of drive transistors and light-emitting elements, enabling external compensation to improve display uniformity and effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTPS TFT or Oxide TFT is used to construct pixel circuit, then mobility and stability are improved, but non-uniformity in electrical parameters (threshold voltage, mobility) occurs due to crystallization process limitations
Solution Approach 1:
The patent implements a feedback mechanism by detecting the threshold voltage of drive transistors and working voltage of OLED devices, then using this detected information to compensate for brightness non-uniformity. The detection circuit measures actual electrical parameters and feeds this information back to adjust compensation values, thereby resolving the non-uniformity issue caused by crystallization process variations.
Solution Approach 2:
The patent introduces an intermediary detection circuit and compensation mechanism between the transistor manufacturing process and the final display output. This intermediary system detects threshold voltage variations and working voltage differences, then applies compensation to eliminate their harmful effects on display uniformity, without changing the transistor manufacturing process itself.
2Ease of manufacture
If OLED devices are evaporated, then film thickness non-uniformity occurs, causing electrical performance non-uniformity and working voltage differences
Solution Approach 1:
The patent detects working voltage differences caused by film thickness non-uniformity using the detection circuit, then uses this feedback information to compensate for brightness variations. By measuring actual working voltages and applying compensation based on detected values, the system resolves the non-uniformity issue without requiring perfect evaporation control.
Solution Approach 2:
The patent replaces mechanical/process control approaches (trying to achieve perfect uniformity during evaporation) with an electrical compensation approach. Instead of attempting to mechanically control film thickness uniformity during evaporation, the system uses electrical detection and compensation to achieve uniform display output despite physical non-uniformities.
3Manufacturing precision
If threshold voltage and working voltage are compensated, then display brightness uniformity is improved, but accurate detection of these voltages is required first
Solution Approach 1:
The patent implements a self-service approach where the detection circuit uses existing pixel circuit components and signals to detect threshold voltage and working voltage without requiring external complex measurement equipment. The system leverages its own internal resources (pixel circuits, data lines, power lines) to perform self-diagnosis and self-compensation, reducing overall system complexity.
Solution Approach 2:
The patent designs the detection circuit with multi-functionality, using the same circuit structure and components for both detecting threshold voltage of transistors and working voltage of OLED devices. This universal approach allows a single detection system to handle multiple measurement tasks, reducing device complexity compared to having separate dedicated circuits for each measurement.
4Ease of operation
If storage capacitor is connected between gate of drive TFT and OLED anode, then data voltage transmission is enabled, but voltage differences in OLED anodes cause different gate-source voltages and drive currents
Solution Approach 1:
The patent detects voltage differences in OLED anodes and the resulting gate-source voltage variations using the detection circuit, then applies compensation based on this feedback information. By measuring actual voltages and adjusting compensation values, the system resolves the non-uniformity in drive currents caused by anode voltage differences while maintaining the simple storage capacitor connection.
Data Source
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AI summary
The disclosure provides a detection circuit, a detection method and a drive system. The detection circuit comprises a switching unit, a reset unit and a comparison unit. The switching unit is used for switching the operations of the reset unit and the comparison unit. The reset unit is used for resetting the acquisition unit before the acquisition unit begins acquisition. The comparison unit is used for comparing a signal acquired by the acquisition unit with a standard signal to obtain a characterization quantity of the to-be-detected voltage. The detection circuit can detect a representative quantity of a threshold voltage of a drive transistor or a working voltage of a light emitting element in a pixel circuit, and thereby can detect non-uniformity of display brightness of pixels inside an active matrix organic electroluminescence display device. In turn, an external compensation circuit is enabled to well compensate the display brightness of pixels according to the detection result, such that the uniformity of display and hence the display effect of the active matrix organic electroluminescence display device is improved.