MicroLED Display Pixel-Group Current Mirroring for Stable Grayscale
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Solution Overview
Problem
Micro LEDs in LEDOS technology face issues with grayscale fluctuations due to current variations, leading to voltage drops and inconsistencies in current supply to individual pixels.
Innovation Solution
A display device that groups pixels into arrays and uses sub-current sources to mirror a reference current, employing multiple current mirrors to ensure consistent current supply to light-emitting elements, minimizing errors and reducing the number of instances current is mirrored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If current is supplied to each individual pixel in LEDOS, then each pixel can be controlled independently, but current variations cause grayscale fluctuations and voltage drops
Solution Approach 1:
Multiple pixels are grouped into a pixel group that shares a common sub-current source. This merging approach reduces the number of current mirrors needed while maintaining independent control capability through the pixel circuit's switching elements. The common current supply path minimizes current variations and voltage drops compared to individual pixel supply.
Solution Approach 2:
The pixel array is divided into multiple pixel groups, each with its own sub-current source. This segmentation allows the system to balance between independent control (achieved through pixel-level switching) and current stability (achieved through group-level current supply). The segmentation reduces the overall number of current mirrors while maintaining grayscale consistency within each group.
2Reliability
If a sub-current source is provided for each pixel group, then current consistency is improved, but the number of current mirrors increases
Solution Approach 1:
Multiple pixels within a pixel group share a common sub-current source and current mirror circuitry. This merging reduces the total number of current mirrors needed compared to providing individual current sources for each pixel, while still maintaining current consistency across all pixels in the group through the shared current supply path.
3Measurement precision
If reference current is mirrored for each pixel, then current precision is maximized, but the number of current mirror instances increases significantly
Solution Approach 1:
The patent merges the current mirror function at the pixel group level rather than at the individual pixel level. Each pixel group shares a common sub-current source that mirrors the reference current once, and this mirrored current is then distributed to multiple pixels within the group. This approach significantly reduces the number of current mirror instances while maintaining sufficient current precision for grayscale control.
Solution Approach 2:
The current mirroring function is extracted from the individual pixel level and consolidated at the pixel group level. The sub-current source in each pixel group performs the current mirroring operation once for the entire group, rather than requiring separate current mirrors for each pixel. This extraction reduces device complexity while maintaining the essential precision needed for current control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures that the current supplied to each pixel group is substantially identical to the reference current, reducing errors and voltage drops, thereby maintaining consistent grayscale across the display.
Implementation Method 1
a first transistor connected to the reference current source and providing a first mirrored current that mirrors the reference current
Implementation Method 2
each of the n pixel circuits provides a second mirrored current that mirrors the first mirrored current
Data Source
AI summary
A display device is proposed. The display device may include a pixel array including n pixel groups, and a reference current source connected to the pixel array and providing a reference current. The display device may also include n sub-current sources and n pixel circuits included in each of the n pixel groups and connected to the reference current source. Each of the n sub-current sources may provide a first mirrored current that mirrors the reference current. Each of the n pixel circuits may provide a second mirrored current that mirrors the first mirrored current, and wherein n is a natural number.