Display Pixel Circuit With Inverted Emission for Luminance Uniformity
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Solution Overview
Problem
Display devices, such as OLEDs, suffer from luminance non-uniformity due to threshold voltage variations in driving transistors, leading to increased power consumption and potential data voltage swing range increases due to kickback phenomena.
Innovation Solution
A pixel design incorporating an eighth transistor that uses an inverted emission signal to manage voltage changes, reducing power consumption by minimizing data voltage swing range through controlled kickback effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a pixel performs compensation operation to compensate for threshold voltage of driving transistor, then luminance uniformity is improved, but power consumption is increased and data voltage swing range is increased
Solution Approach 1:
The patent applies inversion by using an inverted emission signal (EM2) that is phase-opposite to the normal emission signal (EM1). This inverted signal is applied to the gate of the eighth transistor to generate a kickback voltage that counteracts the threshold voltage variation of the driving transistor, thereby compensating for luminance non-uniformity while reducing power consumption and data voltage swing range.
Solution Approach 2:
The eighth transistor serves as an intermediary element that mediates between the inverted emission signal and the data voltage at the first node. By introducing this intermediate transistor controlled by the inverted emission signal, the patent enables voltage compensation through kickback effect without directly modifying the data writing path, thus reducing power consumption while maintaining luminance uniformity.
2Manufacturing precision
If compensation operation is performed using additional signals, then threshold voltage compensation is improved, but kickback phenomenon occurs and data voltage changes undesirably
Solution Approach 1:
The patent converts the harmful kickback phenomenon into a beneficial compensation mechanism. By deliberately applying an inverted emission signal to the eighth transistor, the patent generates a controlled kickback voltage that compensates for threshold voltage variations. This transforms what is typically an unwanted effect into a useful compensation mechanism that improves manufacturing precision while maintaining data voltage stability.
Solution Approach 2:
The inverted emission signal is applied in advance during the emission period to preemptively counteract the threshold voltage variation before it affects the luminance output. This preliminary anti-action through kickback voltage generation prevents undesirable data voltage changes while ensuring accurate threshold voltage compensation.
3Illumination intensity
If data voltage swing range is increased to compensate for threshold voltage variation, then luminance uniformity is improved, but power consumption is increased
Solution Approach 1:
The patent changes the parameter of emission signal phase by using an inverted emission signal (EM2) that is 180 degrees out of phase with the normal emission signal (EM1). This parameter change enables the eighth transistor to generate a kickback voltage that compensates for threshold voltage variation, achieving luminance uniformity without increasing the data voltage swing range or power consumption.
Data Source
AI summary
A pixel includes a first transistor coupled to a first node, a second transistor receiving a writing signal, a third transistor receiving a compensation signal, a first terminal coupled to the third node, and a second terminal coupled to a fourth node, a fourth transistor receiving an initialization signal, a first terminal coupled to the fourth node, and a second terminal coupled to an initialization voltage line, a fifth transistor receiving a first emission signal, a first terminal coupled to the first power supply voltage line, and a second terminal coupled to the second node, a light emitting element coupled to the third node and a second power supply voltage line, and an eighth transistor receiving a second emission signal, a first terminal coupled to the first node, and a second terminal coupled to the fourth node.