Display Pixel Circuit Floating Node Self-Discharge Initialization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In organic EL display devices, the variation in transistor characteristics, such as threshold voltage, leads to display unevenness due to the need for a long initialization voltage writing time, which adversely affects subsequent video signal writing operations.
Innovation Solution
A display device configuration with a pixel array unit including a drive transistor, a sampling transistor, and a storage capacitor, where the gate and source nodes of the drive transistor are made floating after initializing the gate node, allowing for a self-discharge operation to generate a potential difference, enabling shorter initialization voltage writing times and consistent light emitting current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the initialization voltage is written for a long time to correct transistor characteristic variations, then the display uniformity is improved, but the video signal writing operation is adversely affected due to time consumption
Solution Approach 1:
The gate node is initialized to a reference voltage before the threshold correction operation begins. This preliminary initialization ensures that the transistor characteristics are corrected from a known state, enabling accurate correction while reducing the time needed for the correction process itself.
Solution Approach 2:
The correction operation is performed in a specific period when the pixel circuit is in a determined state (after initialization but before video signal writing). This periodic execution of correction at the right moment allows for effective correction without interfering with the video signal writing operation.
2Reliability
If the gate node is kept in a determined state during initialization, then the initialization voltage can be written reliably, but the self-discharge operation cannot generate the necessary potential difference for correction
Solution Approach 1:
The gate node transitions from a determined state (connected to reference voltage during initialization) to a floating state (disconnected during self-discharge). This dynamic state change allows the circuit to perform both reliable initialization and effective self-discharge correction operations at different times.
Solution Approach 2:
The gate node is initialized to a reference voltage beforehand to establish a known starting point. This cushioning initialization ensures that even when the node is later left floating for self-discharge, the correction process starts from a reliable state, maintaining both reliability and correction effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach shortens the initialization voltage writing time, ensures uniform image display by correcting transistor variations, and maintains high contrast by preventing unnecessary light emission during non-lighting periods, thus improving display uniformity and contrast.
Implementation Method 1
a pixel circuit having a storage capacitor to store the signal voltage
Data Source
AI summary
Provided is a display device including a pixel array unit that is made by arranging a drive transistor to drive a light emitting unit, a sampling transistor to sample a signal voltage, and a pixel circuit having a storage capacitor to store the signal voltage which is written by sampling with the sampling transistor, and a drive unit that makes a gate node and a source node of the drive transistor be in a floating state up to performing writing of the signal voltage with the sampling transistor, after writing an initialization voltage in the gate node when the source node of the drive transistor is in a non-floating state.