Display Driving Circuit Threshold Voltage Cancelling for Uniform Luminance
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Solution Overview
Problem
Display apparatuses with current-driven light emitting portions face challenges in maintaining uniform luminance due to variations in threshold voltage correcting operations and signal electric potential writing processes, especially during short scanning periods, leading to deviations in electric potential and current flow across different lines, which affect the uniformity of the displayed image.
Innovation Solution
A method and apparatus where display devices are arranged in a two-dimensional matrix with a driving circuit that includes a driving transistor and a writing transistor, performing a threshold voltage cancelling process in units of display device rows by applying a reference voltage and driving voltage to change the electric potential of the source/drain regions, and sequentially writing video signals to maintain consistent electric potential changes across all rows, ensuring uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If threshold voltage correcting operation and signal electric potential writing operation are performed during one horizontal scanning period, then the luminance of the image is improved, but the scanning period becomes insufficient due to high definition requirements
Solution Approach 1:
The patent divides the display device rows into multiple groups and performs threshold voltage correcting operations for each group sequentially during different horizontal scanning periods. This segmentation allows the correcting operation to be distributed across multiple time slots, making it feasible to complete the correction within the available scanning period while maintaining high definition requirements.
2Manufacturing precision
If control signals are output sequentially to multiple scanning lines for signal electric potential writing, then the writing precision is improved, but the time required for the operation increases
Solution Approach 1:
The patent segments the signal electric potential writing operation by group, performing writing operations for multiple scanning lines within the same horizontal scanning period for each group. This approach maintains writing precision while reducing the total operation time by parallelizing operations within each group segment.
Solution Approach 2:
The patent employs periodic action by repeating the sequence of threshold voltage correction followed by signal electric potential writing for each group of scanning lines across multiple horizontal scanning periods. This periodic repetition ensures that each group receives adequate attention while maintaining overall timing efficiency.
3Productivity
If the period from the end of threshold voltage cancelling process to the start of writing process varies across display device rows, then the processing speed is improved, but the luminance uniformity deteriorates
Solution Approach 1:
The patent segments display device rows into multiple groups and processes each group with a consistent time interval from the end of threshold voltage cancelling to the start of writing process. This segmentation strategy ensures that while different groups may be processed at different times, each group within its processing cycle maintains uniform timing, thereby preserving luminance uniformity across all rows.
Data Source
AI summary
A method of driving a display apparatus formed by arranging display devices each having a driving circuit and a current-driven type light emitting portion, the method comprising the steps of: performing a threshold voltage cancelling process in units of a display device row in which a predetermined reference voltage is applied to a gate electrode of a driving transistor of Q×N display devices configuring groups of display device rows and a predetermined driving voltage is applied to one source/drain region of the Q×N display devices so as to change the electric potential of the other source/drain region toward an electric potential calculated by subtracting a threshold voltage of the driving transistor from the reference voltage during a period TQ; and sequentially performing a writing process, in which video signals are applied to the gate electrodes of the driving transistor of N display devices configuring the display device row, Q times.