Optoelectronic Device Luminance Consistency via Threshold Voltage Compensation
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Solution Overview
Problem
The irregular threshold voltages of driving transistors in optoelectronic devices cause variations in luminance for the same gray scale voltages, affecting the performance of the devices.
Innovation Solution
The implementation of a correction transistor and a control circuit that adjust currents based on voltages stored in capacitors, allowing for precise control of gray scale voltages and luminance, while the driving transistor supplies current to the light-emitting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a driving transistor is used to control current to the OLED, then the device can display images with different luminance levels, but the irregular threshold voltage of the transistor causes luminance variation for the same gray scale voltage
Solution Approach 1:
The patent implements a feedback mechanism where the actual current flowing through the driving transistor is sensed and used to generate a compensation voltage. This compensation voltage is stored in a capacitor and applied to adjust the gate voltage of the driving transistor, thereby compensating for threshold voltage variations and achieving consistent luminance output.
Solution Approach 2:
The patent introduces a correction transistor as an intermediary element that mediates between the driving transistor and the gray scale voltage source. This correction transistor adjusts the voltage applied to the driving transistor's gate based on the sensed current, acting as a mediator to eliminate the harmful effect of threshold voltage irregularity.
2Illumination intensity
If a correction transistor is added to adjust for threshold voltage variations, then luminance consistency is improved, but the device complexity increases
Solution Approach 1:
The correction transistor is designed to perform multiple functions: it adjusts for threshold voltage variations, stores compensation voltage in a capacitor, and can be integrated with existing pixel circuit elements. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the correction transistor with existing pixel circuit elements such as the driving transistor and capacitor structures. By combining multiple functions into a single integrated circuit block, the overall device complexity is minimized while still achieving luminance consistency.
Data Source
AI summary
An optoelectronic device includes a driving transistor, a correction transistor, and a control circuit. The driving transistor adjusts a first current from a power supply based on a voltage stored in a first capacitor. The driving transistor supplies the adjusted first current to the light-emitting element. The correction transistor is electrically connected on a path of a second current flowing from the power supply to the first capacitor, and adjusts the second current based on a voltage stored in a second capacitor. The control circuit controls the second capacitor to store a gray scale voltage while the first current flows, and controls flow of the second current to update the voltage stored in the first capacitor while the first current is blocked.