Display Pixel Circuit with N-Type Transistors for Leakage Control
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Solution Overview
Problem
Display apparatuses for virtual and augmented reality face challenges with high integration and reduced pixel circuit area due to narrow pitch, leading to restrictions on the number of transistors and signals, which affects performance and efficiency.
Innovation Solution
A pixel circuit design with a reduced number of transistors and capacitors, utilizing N-type and P-type transistors in specific configurations to manage power supply voltages and emission signals, enhancing integration and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of transistors and capacitors is reduced to achieve high integration and low area, then the pixel circuit area is reduced and integration is improved, but the leakage current increases and reliability deteriorates
Solution Approach 1:
The patent changes the type parameter of transistors from conventional P-type to N-type for specific positions in the pixel circuit. This parameter change exploits the fundamentally different electrical characteristics of N-type transistors, which have lower off-state leakage current, thereby reducing overall leakage current in the circuit while maintaining the reduced transistor count for high integration.
2Reliability
If N-type transistors are used to reduce leakage current, then reliability is improved, but the threshold voltage control becomes more difficult
Solution Approach 1:
The patent introduces a dedicated control transistor (first control transistor) that acts as an intermediary to manage the threshold voltage of N-type transistors. This control transistor regulates the gate voltage applied to N-type transistors, enabling precise threshold voltage control without directly modifying the N-type transistor structure, thus maintaining reliability while managing complexity.
3Area of stationary object
If the pitch is narrowed to achieve high integration, then the area is reduced, but the number of signals that can be applied to the pixel circuit is restricted
Solution Approach 1:
The patent designs the pixel circuit with multi-functional transistors that can handle multiple signals and operations. For example, the control transistors are designed to manage both data writing and emission control functions, reducing the total number of dedicated signal lines needed. This multi-functionality allows the circuit to maintain adaptability and versatility despite the narrowed pitch and reduced area.
Data Source
AI summary
A pixel circuit includes a light-emitting element, a first transistor which applies a first power supply voltage to a second node in response to a voltage of a first node, a second transistor which applies a voltage of the second node to the first node in response to a control signal, a third transistor which applies the voltage of the second node to the light-emitting element in response to the control signal and a first capacitor connected to the first node. The first power supply voltage has a first voltage level, a second voltage level lower than the first voltage level or a data voltage.