CCFL Brightness Stabilization via Dual-End Current Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cold cathode fluorescent lamps (CCFLs) in flat panel displays face instability due to the thermometer effect and parasitic capacitance, leading to uneven brightness and reduced system efficiency, as the existing solutions fail to accurately detect current and provide stable input currents.
Innovation Solution
A method that involves a current comparison unit to receive and compare currents from both ends of the CCFL, selecting the lower current as a feedback signal to adjust the input current, thereby reducing parasitic capacitance-induced current leakage and stabilizing brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the CCFL is covered by a conductive layer to reduce electromagnetic interference, then electromagnetic interference is reduced, but parasitic capacitance increases causing current leakage
Solution Approach 1:
The patent implements a feedback mechanism where the power controller receives current feedback from the CCFL and adjusts the driving current accordingly. The feedback current is used to detect actual current consumption and compensate for losses due to parasitic capacitance, thereby maintaining stable brightness while accounting for the electromagnetic shielding structure's impact.
Solution Approach 2:
The patent introduces a power controller as an intermediary device between the power source and the CCFL. This controller measures the actual current through the CCFL using feedback signals and adjusts the driving current to compensate for parasitic capacitance effects, thereby mediating between the electromagnetic shielding requirement and current leakage problem.
2Stability of the object's composition
If floating the CCFL is done to improve the thermometer effect, then brightness uniformity improves, but brightness stability deteriorates due to stray capacitance variations
Solution Approach 1:
The power controller continuously monitors the actual current through the CCFL via feedback signals and dynamically adjusts the driving current to maintain consistent brightness. This feedback mechanism compensates for variations in stray capacitance that occur when the CCFL is floated to improve uniformity, thereby maintaining both uniformity and stability.
Solution Approach 2:
The patent employs dynamic current adjustment where the power controller modifies the driving current in real-time based on feedback signals. This dynamic control allows the system to adapt to changing conditions including stray capacitance variations, maintaining stable brightness while preserving the benefits of floating the CCFL for uniformity.
3Device complexity
If feedback from one end of the CCFL is used to control current, then current control is simplified, but measurement accuracy decreases due to current leakage at that end
Solution Approach 1:
The patent implements a feedback system where the current at one end of the CCFL is measured and used to control the power supply. The power controller uses this feedback signal to adjust the driving current, maintaining simple control architecture while compensating for measurement errors through active control rather than passive measurement accuracy.
Solution Approach 2:
The patent replaces the requirement for high-precision passive current measurement with an active feedback control system. Instead of relying on accurate direct measurement, the system uses feedback signals and electronic control to achieve accurate current regulation, substituting measurement precision requirements with control system functionality.
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
This approach enhances the stability and accuracy of CCFL brightness by dynamically selecting the lower current as feedback, mitigating the thermometer effect and reducing current leakage, resulting in improved efficiency and consistent illumination.
Implementation Method 1
a cold cathode fluorescent lamp (CCFL) transforms electricity into light
Implementation Method 2
between the CCFL and the system ground there is a significant parasitic capacitance. The capacitor 106 results in current leakage from the CCFL 104 to the system ground
Implementation Method 3
The EMF gradient in the CCFL 104 makes the CCFL 104 brighter in one end and darker in the other end, which is due to the thermometer effect shown in FIG. 2
Data Source
AI summary
A method for stabilizing brightness of a cold cathode fluorescent lamp includes receiving currents from two ends of the cold cathode fluorescent lamp and providing a current for the cold cathode fluorescent lamp according to a lower current of the currents received from the two ends of the cold cathode fluorescent lamp.