Power Supply Scanner for OLED Drive Transistor Voltage Control
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Solution Overview
Problem
Active-matrix flat self-luminous displays using organic EL devices face challenges in uniformly controlling light-emission luminance due to variations in drive transistor threshold voltage and mobility, which require high capacitance capacitive elements that compromise insulation breakdown voltage, making it difficult to enhance capacitance without risking voltage breakdown.
Innovation Solution
A power supply scanner sequentially switches the potential of power feed lines between different higher potentials in a predetermined sequence, preventing excessive voltage between the source and drain of the drive transistor, allowing for a decrease in gate insulating film thickness and increasing the capacitance of holding capacitors while maintaining insulation breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the dielectric film is decreased to increase the capacitance of the capacitive element, then the capacitance is improved, but the insulation breakdown voltage between source and drain of the drive transistor deteriorates
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage correction before the main driving operation. The correction operation is executed in advance when the pixel is not being driven, allowing the capacitive element to be charged to the correct threshold voltage level before normal operation begins. This prevents voltage breakdown during correction operations while enabling adequate capacitance for stable driving.
Solution Approach 2:
The patent implements dynamics by making the drive transistor's source and drain potentials switchable between multiple levels (first higher potential, second higher potential, and lower potential) in a predetermined sequence. This dynamic voltage switching prevents excessive voltage differences that would cause breakdown, while allowing the system to operate with thinner dielectric films for higher capacitance.
2Manufacturing precision
If the supply voltage is switched between high level and low level to correct threshold voltage and mobility, then the correction operation is enabled, but the potential difference may surpass the insulation breakdown voltage
Solution Approach 1:
The patent performs threshold voltage correction in advance during a dedicated correction operation phase before the main image display begins. By completing the correction operation preliminarily when no image is being displayed, the system can apply necessary voltage corrections without creating excessive potential differences during active driving, thus avoiding insulation breakdown.
Solution Approach 2:
The patent dynamically switches the supply voltage between multiple levels (first higher potential, second higher potential, and lower potential) in a predetermined sequence during correction operations. This controlled dynamic switching enables threshold voltage and mobility correction while preventing the potential difference from exceeding the insulation breakdown voltage of the drive transistor.
3Stability of the object's composition
If the capacitance of the capacitive element is increased to stabilize correction operation, then the correction stability is improved, but the gate insulating film thickness must be decreased which reduces insulation breakdown voltage
Solution Approach 1:
The patent executes the correction operation in advance during a dedicated phase before normal driving begins. By completing threshold voltage and mobility correction preliminarily when the pixel is not being driven, the system can use capacitive elements with adequate capacitance for stable correction without requiring excessively thin gate insulating films that would compromise breakdown voltage during active operation.
Solution Approach 2:
The patent employs dynamic voltage switching between multiple levels to enable correction operations with sufficient capacitance while maintaining insulation breakdown voltage. The controlled switching sequence allows the capacitive element to store necessary correction charges without creating excessive voltage differences that would require thicker gate insulating films.
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 enables stable operation by preventing voltage breakdown and enhancing capacitance, leading to improved light-emission uniformity and display definition without compromising insulation breakdown voltage.
Implementation Method 1
The organic EL device employs a phenomenon that an organic thin film emits light in response to application of an electric field thereto.
Implementation Method 2
In order to stably carry out an operation of correcting the threshold voltage and mobility of the drive transistor, it is preferable for a capacitive element formed in each pixel to have a capacitance that is as high capacitance as possible.
Implementation Method 3
A power supply scanner sequentially switches the potential of power feed lines between different higher potentials in a predetermined sequence, preventing excessive voltage between the source and drain of the drive transistor.
Data Source
AI summary
A display includes: a pixel array section configured to include power feed lines, scan lines disposed along rows, signal lines disposed along columns, and pixels that are disposed at intersections of the scan lines and the signal lines and are arranged in a matrix, each of the pixels including a drive transistor and a light-emitting device, one of a pair of current terminals as source and drain of the drive transistor being connected to the power feed line, and a power supply scanner configured to sequentially switch potential of each power feed line between higher potential and lower potential, wherein the power supply scanner switches the higher potential applied to the power feed line between first higher potential and second higher potential at different levels in a predetermined sequence.