Pixel Driving Circuit Brightness Uniformity via Switch Timing
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Solution Overview
Problem
Pixel driving circuits in display devices face issues with non-uniform brightness due to metal residue, excessive etching, and current path characteristics, leading to higher manufacturing costs and substrate abnormalities during the production of light emitting elements like micro light emitting diodes.
Innovation Solution
The implementation of a display device with pixel driving circuits that include light emitting units, capacitors, and switches, where the second switch is turned on before the first switch, and the use of reference signals to stabilize voltage levels and adjust current flow independently of threshold voltage levels, reducing the impact of internal resistance and manufacturing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional pixel driving circuits are used with standard switch configurations, then the circuit structure is simple, but the brightness uniformity deteriorates due to threshold voltage variations and current path characteristics
Solution Approach 1:
The pixel driving circuit is divided into multiple switching stages (first switch, second switch, third switch) with distinct functions. The first switch controls data signal input, the second switch controls reference signal input, and the third switch controls light emitting signal. This segmentation allows independent optimization of each switching function to achieve uniform brightness while maintaining reasonable circuit complexity.
Solution Approach 2:
The second switch is configured to turn on before the first switch, allowing the reference signal to be written into the capacitor in advance. This preliminary action establishes a stable voltage baseline before the data signal is applied, compensating for threshold voltage variations and ensuring uniform brightness across pixels.
2Productivity
If manufacturing processes for light emitting elements are performed with conventional methods, then the production can be completed, but metal residue and excessive etching cause substrate abnormalities and higher costs
Solution Approach 1:
The circuit performs preliminary detection of switch functionality and capacitor integrity before the light emitting element is fully integrated and activated. By writing reference signals and data signals through the switching circuit and measuring the resulting current, defects are identified early in the manufacturing process, preventing waste of completed light emitting elements and reducing costly rework.
Solution Approach 2:
The pixel driving circuit uses its own switching elements and capacitors to perform self-diagnosis during manufacturing. The circuit writes test signals through its internal switches and measures the response current, enabling automated detection of manufacturing defects without requiring external testing equipment, thereby improving manufacturing efficiency and precision.
3Illumination intensity
If currents are allowed to flow through conventional switch paths, then the circuit operation is simple, but the currents are affected by switch and resistance characteristics causing non-uniform brightness
Solution Approach 1:
A capacitor is introduced as an intermediary element between the switching elements and the light emitting element. The capacitor stores the reference signal voltage and provides a stable voltage baseline that mediates the current flow, isolating the light emitting element from direct dependence on switch threshold voltages and resistance characteristics, thereby achieving uniform brightness while maintaining operational simplicity.
Solution Approach 2:
The circuit changes the operating parameters by using dual switching stages with different timing. The second switch operates at a different time (turning on before the first switch) and controls a different signal (reference signal versus data signal). This parameter change in switching sequence and signal type enables precise control of current flow to achieve uniform brightness.
Data Source
AI summary
A display device includes a light emitting unit, first and second capacitors, and first and second switches. The light emitting unit emits light according to a voltage level of a first node. A first terminal of the first capacitor is coupled to the first node, and a second terminal of the first capacitor is coupled to a second node. A first terminal of the second capacitor is coupled to the second node, and a second terminal of the first capacitor is coupled to the light emitting unit. A first terminal of the first switch is coupled to the first node, and a second terminal of the first switch is coupled to the light emitting unit. The second switch is configured to be turned on before the first switch is turned on, and a first terminal of the second switch is coupled to the first node.