Pixel Circuit Step-Down Sub-Circuit for OLED Contrast
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Solution Overview
Problem
Conventional pixel circuits for silicon-based Organic Light-Emitting Diode (OLED) micro display devices face challenges in achieving high contrast due to difficulties in reducing voltage across the light-emitting element in low-voltage Metal-Oxide-Semiconductor (MOS) manufacture processes.
Innovation Solution
A pixel circuit design incorporating a step-down sub-circuit, storage sub-circuit, and light-emission control sub-circuit to step down data voltage, charge or discharge control nodes, and manage power source voltage connections, enabling reduced voltage across the light-emitting element and improved contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional pixel circuit is used in low-voltage MOS manufacture process, then the manufacturing process is simple, but the voltage across the light-emitting element cannot be effectively reduced, resulting in low contrast
Solution Approach 1:
The pixel circuit is divided into multiple functional sub-circuits: a data write-in sub-circuit for writing data voltage, a step-down sub-circuit for reducing voltage, a storage sub-circuit for maintaining the stepped-down voltage, and a light-emission control sub-circuit for controlling the light-emitting element. This segmentation allows each sub-circuit to perform its specific function efficiently, enabling effective voltage reduction and high contrast while maintaining compatibility with low-voltage MOS manufacture processes.
2Illumination intensity
If the voltage across the light-emitting element is reduced to improve contrast, then contrast is enhanced, but the circuit complexity increases
Solution Approach 1:
Multiple sub-circuits are merged into a single integrated pixel circuit structure that shares common nodes and control signals. The data write-in node, control node, and light-emitting element are interconnected through the various sub-circuits, allowing them to work together as a unified system. This merging approach reduces overall complexity compared to implementing separate circuits for each function.
Solution Approach 2:
The pixel circuit is designed with multi-functional sub-circuits that can perform multiple operations. For example, the step-down sub-circuit not only reduces voltage but also works in conjunction with the storage sub-circuit to maintain the reduced voltage throughout the light-emitting stage. The light-emission control sub-circuit integrates both voltage control and light-emitting element activation functions. This multi-functionality reduces the need for additional dedicated circuits.
3Productivity
If high-frequency operation is implemented to improve productivity, then display refresh rate increases, but motion blur occurs
Solution Approach 1:
The storage sub-circuit is designed to hold the stepped-down voltage from the data write-in stage throughout the entire light-emitting stage. This preliminary storage of the control voltage ensures that the light-emitting element receives stable voltage control even during high-frequency refresh operations, preventing the voltage fluctuations that cause motion blur. The storage sub-circuit acts as a buffer that decouples the data writing process from the light emission process.
Data Source
AI summary
A pixel circuit includes a light-emitting element, a data write-in sub-circuit, a driving sub-circuit, a storage sub-circuit, a light-emission control sub-circuit, and a step-down sub-circuit. The step-down sub-circuit is configured to, at a charging compensation stage, step down a data voltage to acquire a first step-down voltage, and output the first step-down voltage via a control node. The storage sub-circuit is configured to, at the charging compensation stage, charge or discharge the control node to enable a potential at the control node to be the first step-down voltage, and at a light-emitting stage, maintain the potential at the control node as the first step-down voltage. The driving sub-circuit is configured to, at the light-emitting stage, enable a first end of the driving sub-circuit to be electrically connected to a first electrode of the light-emitting element under the control of the control node, to drive the light-emitting element to emit light.