Bypass Switching Transistor for OLED Leakage Current Suppression
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Solution Overview
Problem
In display devices using organic electroluminescence elements, leakage current between the source and drain of the driving transistor can occur when turned off, leading to decreased contrast during black gradation display.
Innovation Solution
A display device with a driving transistor, a switching unit, and a control unit that controls the conduction state to bypass the light emitting element, ensuring no current is supplied during non-light-emission periods, thereby maintaining high contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the driving transistor is turned off to stop current supply to the light emitting element, then black gradation display is achieved, but leakage current flows between source and drain causing decreased contrast
Solution Approach 1:
The pixel circuit is segmented into multiple functional blocks: driving transistor for current control, switching transistor for path selection, storage capacitor for voltage retention, and bypass path for leakage current diversion. This segmentation allows independent optimization of each function to achieve both black gradation and low leakage current.
Solution Approach 2:
A switching transistor is introduced as an intermediary component between the power supply and the light emitting element. This switching transistor acts as a mediator that can completely block the current path when turned off, preventing leakage current from reaching the light emitting element during black gradation display.
2Object-affected harmful factors
If a switching unit is added to bypass the light emitting element to prevent leakage current, then contrast is improved, but device complexity increases
Solution Approach 1:
The switching transistor serves multiple functions: it acts as a switch to block leakage current paths, controls the bypass path for charge redistribution, and works with the storage capacitor to maintain proper voltage levels. This multi-functionality reduces the need for additional dedicated components.
Solution Approach 2:
The bypass path is merged with the existing pixel circuit structure rather than being implemented as a separate parallel circuit. The switching transistor is integrated into the current supply path, and the storage capacitor is connected to existing nodes, combining leakage prevention functionality with the driving circuitry.
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
The solution effectively suppresses leakage current, maintaining high contrast during black gradation display, thereby enhancing the display's overall performance.
Implementation Method 1
the switching unit being configured to, by being brought in the conduction state, form a path that bypasses the light emitting element in a manner that the current is not supplied to the light emitting element
Data Source
AI summary
Provided is a display device including a driving transistor, a switching unit, and a control unit. The driving transistor includes a control terminal, a first terminal, and a second terminal, and controls supply of current to a light emitting element, which is connected to the first terminal and emits light in accordance with the current amount, in accordance with a signal voltage applied to the control terminal. The switching unit can switch a conduction and non-conduction state, and, by being brought in the conduction state, forms a path that bypasses the light emitting element so that the current is not supplied to the light emitting element. The control unit performs control so that the switching unit is brought in the non-conduction state after the signal voltage is written into the control terminal, and controls a potential of the control terminal in synchronization with the control of the switching unit.