Multiplexed Column Drivers for Uniform Passive-Matrix Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Passive-matrix displays experience non-uniformity in light output due to variations in voltage and current between rows or columns controlled by different circuits, which are sensitive to spatial variations in semiconductor epitaxy, leading to visible defects.
Innovation Solution
A passive-matrix controller with a multiplexer that reroutes signals to column drivers, ensuring each column is driven at different times with the same signal, averaging out performance differences and reducing observable variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple column drivers are used to control different columns of light emitters, then the display can drive more columns simultaneously, but the spatial variation in semiconductor epitaxy causes variable circuit operation leading to non-uniform light output
Solution Approach 1:
The patent applies periodic action by sequentially activating different column drivers at different time intervals rather than simultaneously. Each column driver is activated in turn during different time periods, allowing the system to drive multiple columns while averaging out the spatial variations in semiconductor epitaxy. This temporal multiplexing converts a spatial uniformity problem into a time-sequential process, maintaining light output uniformity across all columns.
2Area of stationary object
If column drivers are placed closer together to reduce area, then the chip area decreases, but the variation between circuits increases due to local changes in epitaxy having a larger relative effect
Solution Approach 1:
By implementing periodic activation of column drivers, the patent allows closely-spaced drivers to operate at different times. This temporal separation averages out the local epitaxial variations that would otherwise cause significant circuit performance differences in closely-spaced drivers, thereby maintaining reliability while minimizing chip area.
Solution Approach 2:
The patent introduces dynamic operation by sequentially enabling different column drivers based on time-period signals. This dynamic multiplexing approach allows the system to adapt to spatial variations in the semiconductor substrate, ensuring consistent circuit operation across the chip area while maintaining compact dimensions.
3Manufacturing precision
If a single column driver is used for all columns to reduce circuit variation, then light output uniformity improves, but the device complexity increases due to sequential switching requirements
Solution Approach 1:
The patent segments the column driving function into multiple dedicated column drivers, each responsible for specific columns. By combining segmentation with periodic activation through a multiplexer, the system achieves light output uniformity through spatial distribution while using temporal multiplexing to manage the complexity of controlling multiple drivers.
Data Source
AI summary
A passive-matrix controller provides a control signal to each column of multiple columns of components, a driver for each column wire, and a multiplexer. Each column of components is connected to a column wire. The driver provides a drive signal in response to the control signal and the multiplexer comprises an output connected to each column wire and an input connected to each driver and connects the inputs to the outputs in response to a multiplex signal from the passive-matrix controller. The components can be inorganic micro-light-emitting diodes.