MOSFET Pixel Circuit with Body Electrode for Threshold Compensation
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Solution Overview
Problem
High-resolution display devices, such as head-mounted displays for virtual and augmented reality, require pixels that can efficiently manage high-resolution panels, but existing pixel designs struggle with threshold voltage compensation, leading to inconsistencies in driving current and luminance control.
Innovation Solution
The proposed pixel design incorporates a metal-oxide-semiconductor field-effect transistor (MOSFET) with a body electrode, along with multiple transistors and capacitors, to manage voltage levels and data signals effectively, ensuring reliable threshold voltage compensation and stable current supply to the light emitting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel designs are used in high-resolution displays, then device complexity is reduced, but threshold voltage compensation becomes unreliable leading to current inconsistencies
Solution Approach 1:
The pixel circuit is segmented into multiple specialized transistors: a first transistor for threshold voltage compensation, a second transistor for current mirroring, and a third transistor for driving the light emitting element. This segmentation allows each transistor to perform a specific function reliably, resolving the threshold voltage compensation issue while managing complexity through functional specialization.
Solution Approach 2:
A fourth transistor is introduced as an intermediary element between the data line and the light emitting element. This intermediary transistor enables precise control of the driving current by mediating the signal transmission, thereby improving threshold voltage compensation reliability without directly increasing the complexity of core components.
2Reliability
If more transistors and capacitors are added for voltage management, then current consistency improves, but pixel area increases
Solution Approach 1:
Different regions of the pixel circuit are assigned specific functions with localized optimization. The first transistor region handles threshold voltage compensation, the second transistor region handles current mirroring, and the third transistor region handles driving. This local quality approach ensures current consistency in each functional region while minimizing overall pixel area through efficient spatial arrangement.
Solution Approach 2:
The pixel circuit layout transitions from a planar two-dimensional arrangement to a three-dimensional stacked configuration, where transistors and capacitors are arranged in multiple layers vertically. This dimensional change allows more components to be integrated within the same pixel area, improving current consistency without significantly increasing the pixel footprint.
3Measurement precision
If multiple capacitors are used for voltage storage, then luminance control precision improves, but manufacturing complexity increases
Solution Approach 1:
The first capacitor serves multiple functions: it stores the threshold voltage during the compensation phase and maintains the voltage level during the emission phase. This multi-functionality improves luminance control precision without requiring additional dedicated capacitors, thereby simplifying the manufacturing process compared to designs with separate capacitors for each function.
Solution Approach 2:
The first capacitor is merged with the first transistor to form an integrated compensation unit, where the capacitor is positioned directly adjacent to and electrically connected with the transistor. This merging reduces the number of discrete components and interconnections, improving luminance control precision while easing manufacturing by reducing assembly steps.
4Reliability
If a body electrode is added to the MOSFET, then threshold voltage compensation reliability improves, but device complexity increases
Solution Approach 1:
The body electrode of the MOSFET is connected to the source electrode, enabling the transistor to self-regulate its threshold voltage through the body effect. This self-service mechanism improves threshold voltage compensation reliability without requiring external control circuits or additional components, thereby avoiding increases in overall device complexity.
Solution Approach 2:
The body electrode connection changes the electrical parameters of the MOSFET by introducing body effect control. By adjusting the potential difference between the body electrode and source electrode, the threshold voltage of the transistor can be dynamically adjusted to compensate for process variations, improving reliability while maintaining a simple transistor structure.
Data Source
AI summary
A pixel may include: a first transistor including a second electrode, a first electrode electrically connected to a first power line, and a gate electrode connected to a first node; a second transistor including a second electrode, a first electrode electrically connected to a data line, and a gate electrode electrically connected to a first scan line; a third transistor connected between the first node and the data line, and including a gate electrode electrically connected to a second scan line; a first capacitor including a first electrode connected to the second electrode of the second transistor, and a second electrode connected to the first node; a second capacitor connected between the first power line and the first node; and a light emitting element between a second power line and the first transistor, and including a second electrode electrically connected to the second power line.