OLED Pixel Circuit Stabilizes Current Against Transistor Threshold Variations
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Solution Overview
Problem
Organic light emitting display devices face challenges in achieving uniform luminance across pixels due to variations in threshold voltage of driving transistors, leading to inconsistent light output despite the same gray scale signal, and existing solutions with multiple transistors complicate the pixel structure and increase malfunction probability.
Innovation Solution
A pixel structure is proposed with no more than three transistors connected between power supplies, along with multiple capacitors, where the current supplied to the organic light emitting diode is independent of the voltage threshold of any transistor, using a specific capacitor configuration to stabilize current flow and ensure uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional transistors are added to compensate for threshold voltage variation, then uniform luminance can be achieved, but device complexity and malfunction probability increase
Solution Approach 1:
The patent changes the electrical parameters of the pixel circuit by introducing a transfer transistor that moves charge from a source node to a sink node, thereby adjusting the voltage levels and current flow characteristics to compensate for threshold voltage variations without adding multiple transistors
Solution Approach 2:
The transfer transistor acts as an intermediary element that mediates between the data line and the driving transistor, enabling voltage transfer and current regulation to achieve uniform luminance while maintaining a simple pixel structure
2Manufacturing precision
If additional transistors are added to compensate for threshold voltage variation, then uniform luminance can be achieved, but reliability decreases
Solution Approach 1:
The patent changes the electrical parameters of the pixel circuit by introducing a transfer transistor that moves charge from a source node to a sink node, thereby adjusting the voltage levels and current flow characteristics to compensate for threshold voltage variations without adding multiple transistors
Solution Approach 2:
The patent extracts the compensation function from a complex multi-transistor structure and implements it using a single transfer transistor, thereby reducing the number of potential failure points while maintaining luminance uniformity
3Device complexity
If a simple pixel structure is used, then device complexity is reduced, but threshold voltage variation causes non-uniform luminance
Solution Approach 1:
The patent changes the electrical parameters of the pixel circuit by introducing a transfer transistor that moves charge from a source node to a sink node, thereby adjusting the voltage levels and current flow characteristics to compensate for threshold voltage variations without adding multiple transistors
Solution Approach 2:
The patent substitutes the need for complex mechanical/transistor-based compensation structures with an electrical parameter adjustment mechanism using a transfer transistor, achieving uniform luminance through voltage transfer rather than structural complexity
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 configuration allows for consistent and uniform image luminance across pixels, independent of transistor threshold voltage variations, simplifying the pixel structure and reducing malfunction probability while eliminating the need for complex transistor compensation.
Implementation Method 1
The organic light emitting device displays an image by using an organic light emitting diode that emits light by recombining holes with electrons
Data Source
AI summary
A pixel for an organic light emitting display is disclosed. The pixel is configured to provide a current to an organic light emitting diode which is substantially independent of a voltage threshold of the driving transistor of the circuit.