Display Pixel Circuit With Sub-Compensation for Low Grayscale Blotches
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Solution Overview
Problem
Hybrid oxide polysilicon pixels experience issues with current suppression during low grayscale image display, leading to blotches in displayed images due to voltage changes at the control electrode of the driving transistor.
Innovation Solution
The display panel incorporates a pixel circuit with a driving transistor, a switching transistor, a compensation transistor, a first capacitor, a second capacitor, and a sub-compensation transistor, along with additional transistors and signal lines to control and compensate the voltage at the control electrode, preventing blotches in low grayscale images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used, then the device structure is simple, but blotches appear in low grayscale images due to insufficient current suppression
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a driving transistor for current control, a compensation transistor for voltage compensation, a switching transistor for signal routing, and multiple capacitors (first capacitor for data signal storage, second capacitor for compensation voltage storage) for charge storage. This segmentation allows each component to perform its specific function optimally, resolving the blotche issue while maintaining manageable complexity
Solution Approach 2:
The compensation transistor acts as an intermediary between the output electrode and control electrode of the driving transistor, transferring compensation voltage to correct voltage drops. The first and second capacitors serve as intermediaries for storing and transferring electrical charges. These intermediary elements enable precise control of the driving transistor without requiring complete redesign of the entire pixel circuit
2Reliability
If the voltage at the control electrode is not compensated, then the circuit operation is simple, but current suppression is insufficient during low grayscale display
Solution Approach 1:
The compensation transistor is activated during the programming period before the emission period to pre-compensate the control electrode voltage. The first capacitor stores the data signal voltage and the second capacitor stores the compensation voltage in advance. This preliminary action ensures that when the pixel emits light, the driving transistor already has the correct compensated voltage for proper current suppression
Solution Approach 2:
The compensation transistor creates a feedback mechanism where the voltage at the output electrode is fed back to the control electrode through the compensation transistor. This feedback loop continuously adjusts the control electrode voltage to compensate for voltage drops caused by leakage currents or other factors, ensuring stable current suppression throughout the display operation
Data Source
AI summary
A display panel includes a pixel including a pixel circuit and a light-emitting diode, a data line providing a data signal to the pixel, a gate line providing a gate signal to the pixel, and a power line providing a power signal to the pixel. The pixel circuit includes a driving transistor, a switching transistor, a compensation transistor, and a sub-compensation transistor. The sub-compensation transistor is connected between the power line and a second capacitor or connected between the second capacitor and the driving transistor.