Organic EL Display Pixel Circuit Threshold Voltage Correction
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Solution Overview
Problem
Active matrix flat panel light emitting display apparatuses using organic EL devices face challenges in maintaining uniform light emission luminance due to fluctuations in threshold voltage and mobility of drive transistors and organic EL devices, requiring complex correction operations that increase circuit complexity and component costs, and restrict wiring layout options.
Innovation Solution
The display apparatus incorporates a pixel array with scanning lines, signal lines, and bias lines, utilizing a sampling transistor, drive transistor, light emitting element, holding capacitance, and auxiliary capacitance to perform correction operations without complex potential operations on power supply and signal lines, simplifying the circuit configuration and reducing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction operations are executed in each pixel to control light emission luminance uniformity, then luminance uniformity is improved, but circuit configuration becomes complicated and component costs increase
Solution Approach 1:
The patent combines the threshold voltage correction operation and the video signal write operation into a single integrated process. By using the video signal line to supply both the correction voltage and the video signal, and by coordinating the timing of transistor switching, the patent eliminates the need for separate correction circuits and operations, thereby reducing circuit complexity while maintaining luminance uniformity
Solution Approach 2:
The video signal line is designed to serve multiple functions: it supplies the video signal for display and simultaneously supplies the correction voltage for threshold voltage compensation. This multi-functional use of existing signal lines avoids the need for additional dedicated correction lines, reducing circuit complexity while achieving luminance uniformity
2Manufacturing precision
If correction operations are executed in each pixel to control light emission luminance uniformity, then luminance uniformity is improved, but component costs increase
Solution Approach 1:
The patent merges the correction function into the existing pixel circuit components, particularly utilizing the holding capacitance and drive transistor that are already present for video signal storage and driving. This eliminates the need for additional correction-specific components, thereby reducing component costs while achieving luminance uniformity
3Reliability
If wiring resistances and wiring capacities are decreased to suppress potential waveform distortions, then potential stability is improved, but wiring layout is restricted
Solution Approach 1:
The patent performs threshold voltage correction before the video signal is written to the pixel. By pre-charging the holding capacitance with the correction voltage and coordinating the switching timing, the system compensates for potential waveform distortions before they affect the display, allowing standard wiring designs to be used without requiring reduced wiring resistances or capacities
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables correction operations for each pixel without complicating potential operations on power supply and signal lines, reducing circuit complexity and costs, while maintaining high-quality panel performance with lower power consumption and reduced manufacturing costs.
Implementation Method 1
The organic EL device is a device utilizing such a phenomenon that light is emitted when an organic thin film is applied with an electric field
Implementation Method 2
a correction operation for holding a voltage equivalent to a threshold voltage of the drive transistor in the holding capacitance
Data Source
AI summary
A drive section sequentially supplies respective scanning lines with a control signal and supplies respective signal lines with a video signal to carry out a correction operation for holding a voltage equivalent to a threshold voltage of a drive transistor in a holding capacitance, and subsequently performs a write operation for writing the video signal in the holding capacitance, and before the correction operation, the drive section switches potentials at the bias line and adds a coupling voltage to one current terminal of the drive transistor via an auxiliary capacitance to carry out a preparation operation for an initialization to set a potential difference between a control terminal and the one current terminal of the drive transistor larger than the threshold voltage.