LED Panel Control Circuit Level Adjustment for Down-Ghost Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED panels suffer from the down-ghost phenomenon, where LEDs are inadvertently turned on due to residual voltage, causing unwanted light emission and image distortion.
Innovation Solution
A control circuit with a level adjustment circuit is introduced, which includes short-circuit switches or diodes coupled between the cathode of LEDs and scan lines to ensure the cathode voltage follows the anode voltage, preventing forward-bias and thus eliminating down-ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional LED panel scanning is used to display images, then the panel can show intended images through row-by-row scanning, but parasitic capacitors discharge to lower voltage levels causing LEDs to be wrongly turned on and generate down-ghost images
Solution Approach 1:
The patent applies preliminary anti-action by raising the cathode voltage to a higher level before the next scan cycle begins. This preemptive voltage adjustment prevents the forward-bias condition that would otherwise cause the LED to turn on incorrectly. The level adjustment circuit proactively counteracts the voltage drop caused by parasitic capacitor discharge, thereby eliminating the down-ghost phenomenon before it can occur.
Solution Approach 2:
The patent changes the voltage parameter of the cathode by introducing a level adjustment circuit that raises the cathode voltage to a higher level. This parameter change transforms the voltage relationship between anode and cathode, ensuring that even when parasitic capacitors discharge, the voltage difference remains insufficient to forward-bias the LED and cause unwanted light emission.
2Power
If the cathode voltage is allowed to drop to lower levels during scanning, then current can be supplied efficiently for light emission, but the voltage drop causes forward-bias between anode and cathode in non-emission periods
Solution Approach 1:
The patent segments the voltage control into two distinct phases: during emission periods, the cathode voltage is allowed to drop to enable efficient current supply and light emission; during non-emission periods, the cathode voltage is raised to a higher level to prevent unwanted LED activation. This temporal segmentation of voltage levels resolves the contradiction between power efficiency and activation control reliability.
Solution Approach 2:
The level adjustment circuit performs preliminary action by raising the cathode voltage before non-emission periods begin. This advance voltage adjustment ensures that when the scan line is conducted and couples the anode to high power supply voltage, the cathode is already at a sufficient voltage level to prevent forward-bias, thereby maintaining reliable LED activation control throughout the scanning process.
Data Source
AI summary
The invention discloses a control circuit for controlling a panel. The panel includes a plurality of light-emitting elements arranged as an array. Each row of light-emitting elements among the plurality of light-emitting elements are coupled to each other via one of a plurality of scan lines. The control circuit includes a current source, an emission switch, a plurality of scan switches and a level adjustment circuit. The current source is coupled to a column of light-emitting elements among the plurality of light-emitting elements. The emission switch is coupled to the current source and the column of light-emitting elements. Each of the plurality of scan switches is coupled to one of the column of light-emitting elements via one of the plurality of scan lines. The level adjustment circuit is coupled between the plurality of scan lines and the current source.