Pixel Circuit Time-Sharing Voltage Inputs for High PPI Displays
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Solution Overview
Problem
High PPI display panels face challenges in reducing the complexity of pixel circuit wiring due to the large number of electronic elements, making it difficult to achieve high pixel density and uniform display quality, especially in VR and AR applications.
Innovation Solution
A pixel circuit design that includes a light-emitting element, four transistors, and a capacitor element, where the transistors are configured to time-share data and power supply voltages, detect and compensate threshold voltage deviations, and provide driving currents, reducing the number of electronic elements and simplifying circuit wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of electronic elements in pixel circuits is increased to improve display quality and functionality, then the reliability and compensation capability are improved, but the device complexity and wiring complexity increase
Solution Approach 1:
The patent merges the data voltage input and power supply voltage input into a single shared electrode of the first transistor. This allows the pixel circuit to time-share between receiving data voltage and power supply voltage through the same physical connection, thereby reducing the number of separate wiring lines while maintaining full functionality. The single electrode serves dual purposes: receiving data during programming phase and receiving power supply voltage during display phase
Solution Approach 2:
The first transistor's single electrode is designed to perform multiple functions: it serves as both the data voltage input terminal and the power supply voltage input terminal at different time periods. This multi-functional design eliminates the need for separate dedicated electrodes for each voltage source, thereby simplifying the circuit structure and reducing wiring complexity while maintaining reliability
2Measurement precision
If the number of sub-pixels per inch (PPI) is increased to improve display precision and quality, then the display precision is improved, but the area available for wiring is reduced
Solution Approach 1:
By merging the data and power supply voltage inputs into a single shared electrode connection, the patent significantly reduces the amount of wiring required per pixel circuit. This consolidation frees up valuable area within each pixel, allowing for higher PPI arrangements where more sub-pixels can be packed into the same display area without proportionally increasing wiring complexity
Solution Approach 2:
The patent extracts and eliminates redundant wiring elements by recognizing that separate dedicated electrodes for data and power supply are unnecessary. By removing the extra electrode and its associated wiring, the design reduces the area consumed by circuit elements, thereby enabling higher pixel density arrangements
3Device complexity
If the number of transistors and capacitor elements is reduced to simplify circuit wiring, then the device complexity is reduced, but the capability for threshold voltage compensation and stable light emission may be affected
Solution Approach 1:
The patent incorporates a dedicated compensation transistor (second transistor) that is specifically designed to detect and compensate for threshold voltage variations in the first transistor. This preliminary compensation action ensures that any drift or variation in the driving transistor's characteristics is corrected before it affects display quality, thereby maintaining reliability even with a reduced overall element count
Solution Approach 2:
The compensation transistor acts as an intermediary element that mediates between the variable characteristics of the driving transistor and the required stable output. By introducing this intermediate compensation mechanism, the circuit can tolerate fewer total elements while maintaining performance through active correction of threshold voltage variations
4Reliability
If complex pixel circuits are disposed in high PPI display panels, then the display quality can be maintained, but the ease of manufacture is reduced due to fabrication constraints
Solution Approach 1:
The patent merges multiple voltage inputs into a single electrode connection, which dramatically simplifies the fabrication process. Fewer distinct electrical connections mean fewer photolithography steps, fewer metal layer routing requirements, and reduced alignment tolerances during manufacturing. This makes the circuit much more compatible with standard high-volume fabrication processes used in display manufacturing
Solution Approach 2:
The patent changes the operational parameters of the first transistor to enable time-sharing between data and power supply voltage inputs. By utilizing the transistor's ability to operate in different states (receiving different voltages at different times), the design achieves functional equivalence to a more complex circuit while using fewer physical elements, thereby easing manufacturing constraints
Data Source
AI summary
A pixel circuit and driving method thereof, and a display device are provided. The pixel circuit comprises a light-emitting element, a first, second, third, and fourth transistors, and a capacitor element. The first transistor is configured to time-sharingly receive a data voltage and a power supply voltage under control of a first voltage signal. The second transistor is configured to detect and compensate a threshold voltage deviation of the first transistor under control of a first scanning signal. The third transistor is configured to provide a driving current generated by the first transistor to the light-emitting element under control of a light-emitting signal. The fourth transistor is configured to transmit a reset signal to an anode of the light-emitting element under control of a second scanning signal. The capacitor element is configured to store the data voltage transmitted to the first transistor. The light-emitting element is configured to emit light.