Pixel Circuit Voltage Compensation for High Refresh Rate Displays
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Solution Overview
Problem
High-frequency display products face insufficient driving voltage compensation due to compressed writing and compensation times, while large-sized display products experience significant voltage drops leading to insufficient driving voltage, both affecting the display effect.
Innovation Solution
A pixel circuit is designed with multiple sub-circuits, including a data writing sub-circuit, light-emitting control sub-circuits, a driving sub-circuit, storage sub-circuit, compensation sub-circuit, and initialization sub-circuits, which work together to manage and stabilize the driving voltage across the pixel circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the display frequency is increased for high-frequency display products, then the display refresh rate is improved, but the circuit screen writing and compensation time is compressed, resulting in insufficient driving voltage compensation
Solution Approach 1:
The pixel circuit performs compensation actions in advance during the compensation stage before the light-emitting stage. The compensation transistor transfers compensation voltage to the compensation capacitor during this preliminary phase, ensuring that voltage compensation is completed before the actual light emission, thus resolving the time conflict between high refresh rates and sufficient compensation duration
Solution Approach 2:
The pixel circuit operation is divided into distinct stages: compensation stage, light-emitting stage, and reset stage. By segmenting the operation timeline, the circuit can allocate specific time slots for compensation activities, ensuring adequate compensation time even at high display frequencies. The compensation transistor and compensation capacitor work during the compensation stage, separate from the light-emitting stage
2Area of stationary object
If the display size is increased for large-sized display products, then the display area is improved, but the driving current increases, causing serious voltage drops and insufficient driving voltage
Solution Approach 1:
The pixel circuit employs a feedback mechanism where the compensation transistor senses the voltage drop across the driving transistor and automatically compensates by transferring appropriate voltage to the compensation capacitor. This feedback loop ensures that the driving voltage is maintained at the correct level despite increased current demands from larger display sizes
Solution Approach 2:
The circuit changes the voltage parameter dynamically through the compensation process. The compensation transistor adjusts the compensation voltage based on the actual voltage drop conditions, modifying the electrical parameters in real-time to maintain stable driving voltage across the light-emitting element regardless of display size
3Stability of the object's composition
If the pixel circuit uses more sub-circuits for voltage management, then the driving voltage stability is improved, but the circuit complexity increases
Solution Approach 1:
The compensation transistor serves multiple functions: it acts as a switch for voltage transfer, a sensor for detecting voltage drops, and a regulator for maintaining driving voltage. The compensation capacitor also performs dual roles by storing compensation voltage and maintaining it during the light-emitting stage. This multi-functionality reduces the need for separate dedicated components for each function
Solution Approach 2:
The pixel circuit merges the compensation function with the existing driving transistor and light-emitting control structures. The compensation transistor is integrated into the same pixel circuit architecture, sharing common nodes and signal lines with other components. This merging approach achieves stable voltage management while minimizing the increase in overall circuit complexity
Data Source
AI summary
A pixel circuit includes: data writing sub-circuit coupled to data signal terminal, scanning signal terminal and fourth node; first light-emitting control sub-circuit coupled to first voltage terminal, first light-emitting control terminal and second node; driving sub-circuit coupled to first node, the second node and third node; storage sub-circuit coupled to the first node and the fourth node; compensation sub-circuit coupled to compensation signal terminal, the first node and the third node; second light-emitting control sub-circuit coupled to the third node, second light-emitting control terminal, and an electrode of light-emitting element; first initialization sub-circuit coupled to first reset signal terminal, first initialization signal terminal and the fourth node; second initialization sub-circuit coupled to second reset signal terminal, second initialization signal terminal and an electrode of the light-emitting element; third initialization sub-circuit coupled to third reset signal terminal, third initialization signal terminal and the third node.