Semiconductor Driving Method for Transistor Variation Compensation
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Solution Overview
Problem
Organic EL displays face issues with uneven image quality due to variations in transistor mobility and threshold voltage, leading to insufficient compensation periods and increased complexity in signal driving methods, which affect power consumption and manufacturing costs.
Innovation Solution
A driving method that includes specific periods for holding and discharging voltages in a capacitor connected to a transistor, allowing for compensation of transistor variations without distorting image signals, enabling both line and dot sequential driving and integrating pixel and driver circuits on the same substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If variation in mobility of transistor is compensated while an image signal is input to a pixel, then the compensation period increases, but the period for inputting image signal to other pixels and other processes is shortened
Solution Approach 1:
The gate selection period is divided into multiple distinct time periods: a first period for threshold voltage compensation, a second period for mobility compensation, and a third period for image signal input. This segmentation allows each compensation process to be performed with adequate time without encroaching on the image signal input period, thereby resolving the contradiction between sufficient compensation duration and overall processing speed.
2Productivity
If the number of pixels and frame frequencies increase, or screen size increases, then the gate selection period per pixel becomes shorter, but sufficient compensation and image signal input cannot be performed
Solution Approach 1:
The patent implements a periodic multi-stage compensation scheme where threshold voltage compensation and mobility compensation are performed in alternating or sequential periods within each gate selection cycle. This periodic action allows the system to maintain high pixel counts and frame frequencies while ensuring that each compensation process receives dedicated time slots, preventing the gate selection period from becoming excessively short.
3Measurement precision
If variation in mobility is compensated while an image signal is input, then compensation is affected by distortion of the waveform of the image signal, but accurate compensation becomes impossible
Solution Approach 1:
The patent performs mobility compensation in a second period that occurs before the image signal is fully input in the third period. By conducting the compensation measurement and adjustment before the image signal waveform is applied, the system avoids the distorting influence of the image signal on the compensation process, thereby achieving accurate compensation without requiring complex distortion control mechanisms.
4Reliability
If variation in mobility is compensated while an image signal is input to a pixel, then dot sequential driving cannot be performed, but driving flexibility is reduced
Solution Approach 1:
The patent implements a dynamic driving scheme where the timing and sequencing of compensation periods can be flexibly adjusted based on the selected driving mode. For dot sequential driving, the compensation periods are synchronized with the pixel-by-pixel addressing sequence, while for line sequential driving, compensation is performed across entire rows. This dynamic adaptation maintains effective compensation across different driving methods without sacrificing versatility.
Data Source
AI summary
A driving method of a semiconductor device for compensating variation in threshold voltage and mobility of a transistor is provided. A driving method of a semiconductor device including a transistor and a capacitor electrically connected to a gate of the transistor includes a first period where voltage corresponding to threshold voltage of the transistor is held in the capacitor, a second period where a total voltage of video signal voltage and threshold voltage is held in the capacitor holding the threshold voltage, and a third period where charge held in the capacitor in accordance with the total voltage of the video signal voltage and the threshold voltage in the second period is discharged through the transistor.