Column Controller LED Display Coupling Reduction
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Solution Overview
Problem
LED display walls face a coupling effect where LEDs within an array are coupled brighter or darker based on the output values of nearby LEDs, leading to distorted images and performance issues in small-pitch indoor applications.
Innovation Solution
The implementation of a column controller that uses one-shot functions and gamma correction to control voltages across LEDs, minimizing parasitic capacitance and tail charges by pre-charging, illuminating, and de-illuminating LEDs in a controlled manner to reduce coupling effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LEDs are driven with standard waveforms without pre-charging and de-illuminating, then the circuit complexity is reduced, but coupling effects cause distorted images and poor display quality
Solution Approach 1:
The patent applies preliminary action by implementing pre-charging waveforms before the main illumination period and de-illuminating waveforms after the main period. This preliminary preparation charges or discharges parasitic capacitances in advance, preventing coupling effects during the critical illumination phase and ensuring accurate brightness control without requiring complex real-time adjustments.
Solution Approach 2:
The patent uses periodic action through the structured sequence of waveforms: pre-charging phase, main illumination phase, and de-illuminating phase. This periodic structure systematically manages the charge and discharge of parasitic capacitances at different time intervals, effectively isolating coupling effects between adjacent LEDs while maintaining simple circuit architecture.
2Reliability
If parasitic capacitance and tail charges are not minimized through controlled voltage application, then the control circuit is simpler, but coupling effects cause ghosting and color shifting
Solution Approach 1:
The patent applies preliminary action by implementing pre-charging waveforms before the main illumination period and de-illuminating waveforms after the main period. This preliminary preparation charges or discharges parasitic capacitances in advance, preventing coupling effects during the critical illumination phase and ensuring accurate brightness control without requiring complex real-time adjustments.
Solution Approach 2:
The patent changes the temporal parameters of voltage application by introducing distinct time intervals for pre-charging, main illumination, and de-illuminating phases. This parameter modification allows systematic control of parasitic capacitance charge and discharge, minimizing coupling effects while maintaining relatively simple control circuitry.
3Manufacturing precision
If standard LED driving methods are used without one-shot functions, then the implementation is simpler, but coupling effects cause distorted images in small-pitch displays
Solution Approach 1:
The patent applies preliminary action by implementing pre-charging waveforms before the main illumination period and de-illuminating waveforms after the main period. This preliminary preparation charges or discharges parasitic capacitances in advance, preventing coupling effects during the critical illumination phase and ensuring accurate brightness control without requiring complex real-time adjustments.
Solution Approach 2:
The patent implements feedback through the structured waveform sequence that anticipates and compensates for parasitic capacitance effects. The pre-charging and de-illuminating phases provide implicit feedback control by preparing the circuit state in advance, ensuring that coupling effects are minimized without requiring complex real-time measurement and adjustment mechanisms.
Data Source
AI summary
Methods and apparatus to reduce a coupling effect in a light emitting diode (LED) display are disclosed. An example LED display includes an array of LEDs, and a line controller to select a line of LEDs of the array of LEDs for illumination. The example LED display wall includes a column controller to control illumination of at least two of the LEDs of the line of LEDs. The column controller is to cause, when the first brightness value is less than a threshold, a first LED to be illuminated during a first time period and a second LED to be illuminated during a second time period. The second period is distinct from the first time period. The first LED is a different color than the second LED.