Pixel Circuit Anode Initialization for Luminance Accuracy
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Solution Overview
Problem
The deterioration of light emitting elements in display devices due to voltage levels can lead to damage and compromised luminance accuracy.
Innovation Solution
A pixel circuit design that includes a first transistor to generate a driving current, a light emitting element with an anode connected to the second terminal of the first transistor, and additional transistors and capacitors to manage data voltage, ground voltage, and emission signals, preventing changes in the gate-source voltage of the first transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light emitting element is operated with high voltage to improve luminance output, then the brightness is improved, but the light emitting element deteriorates and may be damaged
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gate voltage of the first transistor based on the actual voltage level of the light emitting element's anode. When the anode voltage is high, the gate voltage is increased to compensate for the voltage drop across the light emitting element, thereby maintaining stable driving current. This prevents deterioration by avoiding excessive voltage stress on the light emitting element while maintaining adequate luminance output.
Solution Approach 2:
The patent implements feedback control by monitoring the voltage level of the light emitting element's anode and adjusting the transistor gate voltage accordingly. The second capacitor stores the actual anode voltage, and this stored voltage is fed back to control the first transistor's gate terminal. This feedback mechanism ensures that the driving current remains stable despite variations in light emitting element conditions, preventing both insufficient brightness and excessive voltage stress.
2Stability of the object's composition
If the gate voltage of the first transistor is increased to compensate for anode voltage drops, then the driving current stability is improved, but the gate-source voltage changes cause luminance accuracy deterioration
Solution Approach 1:
The patent introduces an intermediary mechanism using the second capacitor to store the actual anode voltage and use it as a reference for controlling the first transistor's gate terminal. Instead of directly adjusting gate voltage based on fixed assumptions, the system uses the actual measured anode voltage (stored in the second capacitor) as an intermediary reference. This allows the gate voltage to be adjusted to compensate for anode voltage drops while maintaining accurate control over the driving current, preventing both instability and luminance accuracy deterioration.
Data Source
AI summary
A pixel circuit connects one terminal of a second capacitor to a line of an anode initialization gate signal rather than an anode of a light emitting element such that a change of a gate-source voltage of a first transistor is prevented. The change of the gate-source voltage of the first transistor is prevented, and thus a change of a driving current generated by the first transistor is prevented. Therefore, any damage due to a deterioration of the light emitting element receiving the driving current is prevented, and a luminance accuracy of the light emitting element is preserved.