Active Matrix Substrate Adjusting Pixel Electrode Voltage
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Solution Overview
Problem
Conventional organic EL display devices with compensation circuits suffer from long response times and stepwise response characteristics due to parasitic capacitance between the pixel electrode and the gate electrode of the drive transistor, leading to reduced display performance and the occurrence of 'caudate afterimage' in moving images.
Innovation Solution
An analog gradation-driving active matrix substrate is designed with an adjusting transistor to adjust the voltage of the pixel electrode, reducing parasitic capacitance by ensuring the voltage of the pixel electrode is closer to the gate voltage of the drive transistor, thereby preventing stepwise response characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compensation circuit is formed in each pixel to compensate for threshold voltage variations, then display uniformity is improved, but response time increases due to parasitic capacitance between pixel electrode and gate electrode
Solution Approach 1:
The patent applies equipotentiality by adjusting the pixel electrode voltage to match the gate electrode voltage potential, minimizing potential differences that cause parasitic capacitance effects. The adjusting transistor modulates the pixel electrode voltage to maintain it close to the gate voltage during different operating states, thereby reducing the voltage difference that generates parasitic capacitance and its associated time constants.
Solution Approach 2:
The patent changes the voltage parameter of the pixel electrode dynamically using an adjusting transistor. By modulating the pixel electrode voltage to track the gate voltage, the system alters the electrical parameters to minimize parasitic capacitance effects. This parameter adjustment reduces the effective capacitance time constant without requiring structural changes to the compensation circuit.
2Speed
If the pixel electrode voltage is adjusted to reduce parasitic capacitance, then response time is reduced, but circuit complexity increases due to additional adjusting transistor
Solution Approach 1:
The adjusting transistor is designed to serve multiple functions: it adjusts the pixel electrode voltage to reduce parasitic capacitance, works in conjunction with the compensation circuit for threshold voltage compensation, and operates during different timing phases (initialization, data input, light emission). This multi-functionality justifies the additional component by providing several benefits within a single element.
Solution Approach 2:
The adjusting transistor acts as an intermediary between the data signal line and the pixel electrode, mediating the voltage adjustment process. It controls the voltage applied to the pixel electrode based on the gate voltage level, serving as a buffer that reduces the direct impact of parasitic capacitance while maintaining the necessary voltage levels for display operation.
3Stability of the object's composition
If parasitic capacitance is reduced by adjusting voltage relationships, then stepwise response characteristics are eliminated, but manufacturing precision requirements increase
Solution Approach 1:
The system implements feedback by using the gate voltage as a reference to adjust the pixel electrode voltage. The adjusting transistor receives the data signal and modulates the pixel electrode voltage based on the gate voltage level, creating a feedback mechanism that automatically compensates for voltage differences. This feedback approach reduces the need for high manufacturing precision by self-correcting voltage variations.
Solution Approach 2:
The patent applies preliminary action by adjusting the pixel electrode voltage in advance during the initialization phase and data input phase before the light emission phase. The adjusting transistor pre-establishes the appropriate voltage relationship between pixel electrode and gate electrode, eliminating stepwise responses before they manifest during light emission, thereby reducing precision requirements during critical display operation.
Data Source
AI summary
The present invention provides an analog gradation-driving active matrix substrate suppressing reduction in the response time of the current-driven light-emitting element; a display device; and an organic EL display device. The active matrix substrate of the present invention is an analog gradation-driving active matrix substrate, comprising:pixels each including a current-driven light-emitting element and a drive transistor,the current-driven light-emitting element has a pixel electrode electrically coupled with the drive transistor,the drive transistor supplies a current to the current-driven light-emitting element through the pixel electrode,wherein an adjusting transistor for adjusting a voltage of the pixel electrode is electrically connected to a path for the electric current supplied from the drive transistor to the current-driven light-emitting element.