4T2C Pixel Circuit With Threshold Compensation for Narrow-Pitch Displays
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Solution Overview
Problem
Display devices, particularly those used in virtual reality or augmented reality, face challenges in achieving high integration and emission reliability due to the narrow pitch of pixel circuits, which restricts the number of transistors and signals.
Innovation Solution
A pixel circuit with a 4T2C structure, including a first transistor, second to fourth transistors, and two capacitors, where the threshold voltage of the driving transistor is compensated by a compensation transistor, improving emission reliability and integration by allowing simultaneous emission of pixel-rows without a dedicated emission signal driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the pitch of pixel circuit is narrowed to achieve high integration, then the area is reduced, but the number of transistors and signals is restricted
Solution Approach 1:
The patent merges the emission control function into the data writing process. The data signal simultaneously performs two functions: writing pixel data and controlling light emission timing. This eliminates the need for separate emission control transistors and signals, reducing the transistor count while maintaining full functionality.
Solution Approach 2:
The data signal is designed to serve multiple purposes: it writes pixel data to the holding capacitor and simultaneously acts as the emission control signal for the light emitting element. This multi-functional approach reduces the number of dedicated control signals and transistors needed in the pixel circuit.
2Area of stationary object
If the number of transistors is reduced for high integration, then the area is reduced, but the emission reliability may deteriorate
Solution Approach 1:
The emission control function is merged with the data writing operation. The data signal that writes pixel information also triggers light emission, eliminating the need for separate emission control transistors while maintaining reliable emission control through the dual-function data signal path.
3Reliability
If dedicated emission signal driver is added to improve emission reliability, then the reliability is improved, but the integration is reduced
Solution Approach 1:
The emission control function is merged with the data writing operation. The data signal that writes pixel information also triggers light emission, eliminating the need for separate emission control transistors while maintaining reliable emission control through the dual-function data signal path.
Solution Approach 2:
The data signal is designed to serve multiple purposes: it writes pixel data to the holding capacitor and simultaneously acts as the emission control signal for the light emitting element. This multi-functional approach reduces the number of dedicated control signals and transistors needed in the pixel circuit.
Data Source
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AI summary
A display device includes a display panel including pixel circuits and a display panel driver. The pixel circuit (PXA) includes a first transistor (T1A) including a control electrode connected to a first node (N1A), a first electrode receiving a first driving voltage (DV1) and as second electrode connected to a second node (N2A), a second transistor (T2A) applying a data voltage (VDATA) to a third node (N3A) in response to a write gate signal (GW[n]), a third transistor (T3A) connecting the first node and the second node in response to a compensation gate signal (GC), a first capacitor (C1A) and a light emitting element (EE) including a first electrode connected to the second node and a second electrode receiving a second driving voltage (DV2). The first driving voltage has a driving-high voltage or a driving-low voltage, and the second driving voltage has the driving-high voltage and the driving-low voltage. The compensation gate signal may be globally applied.