OLED Pixel Circuit Voltage Compensation for Afterimage Suppression
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Solution Overview
Problem
Current driving technologies for OLEDs face challenges in maintaining current stability due to device aging and threshold voltage shifts, leading to image quality degradation issues such as afterimages.
Innovation Solution
A pixel circuit with compensation sub-circuits that stabilize the operating voltage and current by generating compensation data signals based on node voltages, using transistors and capacitors to adjust the current applied to the OLEDs, thereby compensating for threshold voltage variations and aging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor is used to hold electric charge in a pixel circuit, then the pixel circuit can maintain image data, but the transistor exhibits threshold voltage shift and floating potential problems that deteriorate circuit reliability
Solution Approach 1:
The invention extracts the charge storage function from the transistor gate and relocates it to a dedicated storage node (first storage node and second storage node). This separation removes the transistor from the problematic charge-holding role, eliminating threshold voltage shift and floating potential issues while maintaining the ability to hold image data.
Solution Approach 2:
The invention introduces dual storage nodes as intermediary elements between the transistor and the light-receiving element. These storage nodes act as mediators that stabilize the circuit potential during switching operations and prevent direct coupling between the transistor gate and the charge storage function, thereby resolving stability issues.
2Ease of operation
If dual-gate transistors are used to improve switching characteristics, then switching performance is enhanced, but the device structure becomes more complex and manufacturing difficulty increases
Solution Approach 1:
The invention segments the charge storage function into two separate single-gate transistors (first and second transfer transistors) that operate independently through dual storage nodes. This segmentation avoids the complexity of dual-gate transistor structures while achieving similar switching performance through coordinated operation of multiple simpler components.
3Manufacturing precision
If conventional pixel circuits are used, then the display device can function, but image quality is poor due to threshold voltage shift and floating potential
Solution Approach 1:
The invention performs preliminary stabilization by using the dual storage nodes to pre-establish stable reference potentials before the transfer transistors switch. This preliminary action prevents threshold voltage shift and floating potential from degrading image quality, ensuring both high manufacturing precision and circuit reliability.
Data Source
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AI summary
Embodiments of the present disclosure provide a pixel circuit, including: a plurality of pixel units arranged in a matrix, wherein each pixel unit includes a light-emitting element and a pixel driving circuit for driving the light-emitting element to emit light, and the pixel driving circuit and the light-emitting element are electrically connected to a first node; a first compensation sub-circuit electrically connected to each pixel driving circuit in each of the pixel units, wherein the first compensation sub-circuit is configured to provide an initialization signal to the pixel driving circuit, and to obtain a voltage at the first node when the light-emitting element emits light via the pixel driving circuit, and to generate a compensation data signal based on the voltage at the first node; and a second compensation sub-circuit electrically connected to each pixel driving circuit in each of the pixel units and configured to keep the voltage at the first node within a set operating voltage range of the light-emitting element, wherein the pixel driving circuit is further configured to initialize the first node based on the initialization signal, and to use the compensation data signal to drive the light-emitting element to emit light.