OLED Buffer Circuit Isolates Drive Voltage From Threshold Deviations
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Solution Overview
Problem
The existing organic electro-luminescence devices suffer from non-uniform picture quality due to luminance deviations caused by threshold voltage deviations and electron mobility non-uniformity in thin film transistors, leading to reduced gradation levels and degraded picture quality.
Innovation Solution
An organic electro-luminescence device with a buffer circuit that isolates the OLED drive voltage from the threshold voltage of the driving transistor, using a capacitor and switching elements to ensure the driving current is determined by the supply voltage and data voltage, independent of the threshold voltage, thereby maintaining uniformity and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If voltage addressing is used to drive the OLED, then the device can operate at low voltage with high response speed, but threshold voltage deviations and electron mobility non-uniformity cause luminance deviation and non-uniform picture quality
Solution Approach 1:
A buffer circuit is introduced as an intermediary component between the data line and the OLED. This buffer circuit includes a capacitor connected between the data line and the gate of the driving transistor, and a switching transistor that controls the charging of the capacitor. The buffer circuit mediates the voltage application to ensure that the OLED receives a stable driving voltage independent of threshold voltage variations in the driving transistor, thereby achieving uniform picture quality while maintaining fast response speed.
Solution Approach 2:
The invention changes the parameter control approach by using a capacitor to store and maintain the driving voltage. Instead of directly applying voltage from the data line to the OLED through the driving transistor, the system uses the capacitor to hold the voltage level, ensuring that the OLED receives a consistent voltage regardless of threshold voltage deviations. This parameter change strategy eliminates the impact of manufacturing non-uniformity on picture quality.
2Manufacturing precision
If threshold voltage deviation is compensated by adjusting data voltage, then picture quality uniformity can be improved, but the complexity of voltage control increases
Solution Approach 1:
The buffer circuit acts as an intermediary that automatically compensates for threshold voltage deviations without requiring complex external voltage adjustment. The capacitor in the buffer circuit stores the driving voltage and maintains it stable, while the switching transistor controls the charging process. This intermediary mechanism simplifies the overall voltage control system compared to direct adjustment methods.
Solution Approach 2:
The buffer circuit performs self-regulation to maintain stable driving voltage for the OLED. The capacitor automatically holds the voltage level, and the switching transistor controls the charging process based on the data voltage from the data line. This self-service mechanism eliminates the need for complex external control systems to compensate for threshold voltage deviations, thereby improving picture quality uniformity while keeping the control system simple.
3Measurement precision
If multi-step data voltage is applied to express gradation, then 8-bit gradation can be achieved, but threshold voltage deviation reduces the effective gradation levels
Solution Approach 1:
The buffer circuit with the capacitor serves as an intermediary that preserves the multi-step data voltage levels from the data line and delivers them stably to the OLED. The capacitor maintains each voltage level during the display period, ensuring that the OLED receives the precise multi-step voltage needed for 8-bit gradation. This intermediary mechanism prevents threshold voltage deviations from reducing the effective gradation levels, thereby maintaining high measurement precision.
Solution Approach 2:
The invention uses parameter changes by employing the capacitor to hold and stabilize the multi-step data voltage levels. Instead of directly applying the voltage through the driving transistor where threshold voltage deviations would affect the levels, the system uses the capacitor to maintain each voltage step. This parameter change strategy ensures that all 256 gradation levels are effectively delivered to the OLED, maintaining 8-bit precision despite manufacturing variations.
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 achieves uniform picture quality by eliminating the impact of threshold voltage deviations on the driving current, improving reliability and reducing power consumption, while maintaining high gradation levels and enhancing display performance.
Implementation Method 1
a capacitor connected to and between the first switching device and a gate terminal of the driving transistor
Implementation Method 2
The organic electro-luminescence device displays a predetermined image by exciting a phosphor material using carriers, such as electrons and holes
Data Source
AI summary
An organic electro-luminescence device according to an embodiment includes a light-emitting device in a pixel for emitting light; a data line for providing a data voltage; and a driving transistor connected to the light emitting device, wherein when the driving transistor is turned on to drive the light-emitting device, a driving voltage applied to the light emitting device reaches a value of a difference between a supply voltage and the data voltage.