Back-Gate Pixel Circuit for OLED Threshold Voltage Compensation
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Solution Overview
Problem
Existing display apparatuses using organic EL elements face challenges in achieving high display quality, high color reproducibility, and reduced power consumption due to variations in threshold voltage of driving transistors, which affect the current flowing through the organic EL elements.
Innovation Solution
A semiconductor device comprising first and second transistors, switches, capacitors, and a display element, where the transistors include a back gate and metal oxide in the semiconductor layer, and the capacitors are used to retain potential differences, enabling precise control of the current flowing through the display element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high voltage power source is added to drive organic EL elements, then the display quality and color reproducibility are improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent combines the high voltage generation function with the existing driving transistor by utilizing the back gate terminal. Instead of adding a separate power source circuit, the back gate is used to generate the necessary high voltage potential difference, thereby merging multiple functions into a single component and reducing overall device complexity while maintaining display quality
Solution Approach 2:
The back gate terminal, which is typically an auxiliary terminal in transistors, is repurposed to serve dual functions: maintaining transistor performance and generating high voltage for driving organic EL elements. This multi-functional usage eliminates the need for dedicated high voltage generation circuits, reducing device complexity while achieving improved display quality
2Manufacturing precision
If threshold voltage correction is implemented in each pixel, then display quality is improved, but the number of transistors and circuit complexity increase
Solution Approach 1:
The patent merges the threshold voltage correction function with the existing driving transistor structure by utilizing the back gate. Instead of adding separate correction circuits or additional transistors per pixel, the back gate is used to apply compensation voltages that correct threshold variations, thereby achieving improved display quality without increasing circuit complexity
Solution Approach 2:
The driving transistor uses its own back gate terminal to perform self-correction of threshold voltage variations. By applying compensation voltages through the back gate, the transistor autonomously adjusts its performance without requiring external correction circuits, reducing overall device complexity while maintaining high display quality
3Manufacturing precision
If more transistors are added per pixel for current control, then color reproducibility is improved, but the pixel area and device size increase
Solution Approach 1:
The patent combines multiple control functions (current control, threshold correction, high voltage generation) into a single driving transistor by utilizing the back gate terminal. This integration eliminates the need for additional transistors that would otherwise be required for these functions, thereby maintaining color reproducibility while reducing pixel area and device size
Data Source
AI summary
The invention of the application is the invention regarding a semiconductor device and a method for driving the semiconductor device. The semiconductor device includes first and second transistors, first to fifth switches, first to third capacitors, and a display element. The first transistor (M2) comprises a back gate, a gate of the first transistor is electrically connected to the first switch (M1), the second switch (M3) and the first capacitor (C1) are positioned between the gate of the first transistor and a source of the first transistor, the back gate of the first transistor is electrically connected to the third switch (M4), the second capacitor (C2) is positioned between the back gate of the first transistor and the source of the first transistor, the source of the first transistor is electrically connected to the fourth switch (M6) and a drain of the second transistor (M5), a gate of the second transistor is electrically connected to the fifth switch (M7), the third capacitor (C3) is positioned between the gate of the second transistor and a source of the second transistor, and the source of the second transistor is electrically connected to the display element (61).