Semiconductor Pixel Circuit for Threshold Voltage Variation Correction
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Solution Overview
Problem
Current semiconductor devices face issues with variations in threshold voltage and mobility of transistors, leading to display unevenness and reduced image quality, particularly in current-driving-type light-emitting elements like OLEDs, where correcting these variations is challenging.
Innovation Solution
A semiconductor device configuration that includes a transistor with specific wiring connections to control current flow, utilizing switches and capacitors to correct variations in threshold voltage and mobility, thereby reducing adverse effects on display elements and achieving high-quality image display with a minimal number of transistors and wirings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional transistor configurations are used in current-driving-type light-emitting elements, then the device structure is simple, but variations in threshold voltage and mobility cause display unevenness and reduced image quality
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a switching circuit with multiple switches for precise current control, a storage capacitor for voltage holding, and a compensation circuit for threshold voltage correction. This segmentation allows each component to address specific issues independently, achieving display uniformity without requiring complete circuit redesign.
Solution Approach 2:
The compensation circuit performs preliminary correction of threshold voltage variations before the main current driving operation. By pre-compensating for transistor parameter variations through dedicated compensation transistors and capacitors, the system ensures accurate current control throughout the display operation, preventing display unevenness before it occurs.
2Manufacturing precision
If the number of transistors and wirings is increased to correct transistor variations, then display quality improves, but the device becomes more complex and larger
Solution Approach 1:
Multiple switches in the switching circuit serve dual functions: they control the main current flow to the light-emitting element and simultaneously enable compensation operations for threshold voltage correction. This multi-functionality allows the circuit to achieve high image quality without requiring separate dedicated compensation circuits, thereby limiting the increase in component count.
Solution Approach 2:
The compensation circuit is merged with the main switching circuit by sharing common nodes, power supply lines, and control signals. The compensation transistors are integrated into the existing pixel structure, and their control is coordinated with the main switching operations. This merging reduces the overall component count while maintaining the ability to correct transistor variations for high image quality.
Data Source
AI summary
To reduce adverse effect of variations in threshold voltage. A semiconductor device includes a transistor including a gate connected to one electrode of a capacitor and one terminal of a SW1, a source and a drain one of which is connected to one terminal of a SW2 and one terminal of a SW3 and the other of which is connected to the other terminal of the SW1 and one terminal of a SW4; a first wiring electrically connected to the other terminal of the SW2; a second wiring electrically connected to the other terminal of the SW4; a load including electrodes one of which is connected to one electrode of the capacitor and the other terminal of the SW3; and a third wiring connected to the other electrode of the load.