LED Lamp Conductive Screen Diverts Leakage Current
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Solution Overview
Problem
Tubular LED lamps driven by high frequency fluorescent ballasts experience leakage current issues, leading to unwanted light output when dimmed to the lowest brightness setting, due to charge injection and parasitic capacitance causing glow even when the lamp is intended to be off.
Innovation Solution
An electrically conductive screen is connected to a node of the LED arrangement, such as the internal ground, creating a low impedance path for leakage currents to bypass the LED string, preventing glow by acting as a floating current sink, which can be an existing heatsink or a dedicated component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LED lamp is driven by high frequency ballast, then compatibility with existing fluorescent ballasts is achieved, but leakage current causes unwanted glow during deepest dimming
Solution Approach 1:
A resistive element (220 ohms, 2 Watts) is introduced as an intermediary component connected in parallel with the LED string. This resistor provides an alternative path for the leakage current generated by the high frequency ballast, preventing the current from flowing through the LED string and causing unwanted glow during deepest dimming while maintaining ballast compatibility
Solution Approach 2:
The harmful leakage current that causes glow during deepest dimming is converted into a beneficial effect by using it to flow through the parallel resistor instead of the LED string. The resistor dissipates this leakage current as heat, transforming the harmful glow-inducing current into a harmless thermal dissipation path
2Object-generated harmful factors
If a parallel resistive element is added to prevent glow, then leakage current is diverted, but device complexity increases
Solution Approach 1:
The parallel resistive element serves multiple functions simultaneously: it provides a leakage current path during deepest dimming to prevent LED glow, and it maintains proper operating current during normal brightness levels. This multi-functionality allows a single component to address the glow issue without requiring additional complex circuitry
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 solution effectively prevents glow during the deepest dimming setting by diverting leakage currents away from the LED string, ensuring the lamp remains off when intended, and can be implemented with minimal additional components, enhancing safety by avoiding user contact with the screen.
Implementation Method 1
an electrically conductive screen, wherein there is an electrical connection between a node of the LED arrangement and the screen for preventing glow of the LED arrangement when the tubular LED lamp is in an off state
Data Source
AI summary
A tubular LED lamp designed for connection to a high frequency ballast. An electrically conductive screen is provided with an electrical connection between an internal node, such as an internal LED ground, and the screen. This provides a low impedance path5 for leakage currents which bypasses the LED string and thus prevents glow.