Galvanic Isolation in Linear LED Tube Lamps

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Solution Overview

Problem

Linear LED tube lamps face safety issues due to potential electric shock and internal arcing hazards, particularly when used with electronic ballasts, which can lead to fires and injuries during maintenance or relamping, as conventional shock prevention switches are ineffective against high-voltage, high-frequency arcing.

Innovation Solution

Implementing a galvanic isolation approach in the linear LED-based solid-state lamp using a controller and electrical contacts to control through-lamp electric shock current, ensuring that the LED driving circuit and arrays are not electrically connected to exposed conductors during relamping, thereby reducing the risk of electric shock and internal fires.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional shock prevention switches are used in linear LED tube lamps, then electric shock protection is provided during normal operation, but internal arcing occurs during relamping or maintenance when high-voltage, high-frequency current flows through the switches

Engineering Contradiction:

Improveelectric shock protectionVSAvoidinternal arcing

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent removes the shock prevention switches from the circuit path during relamping operations. By extracting the switching elements that cause arcing, the system eliminates the source of internal fires while maintaining safety during normal operation through alternative means such as capacitive isolation or controlled disconnection mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary mechanism (such as a capacitor or isolation barrier) between the high-voltage circuit and the electrical contacts. This intermediary blocks the harmful high-frequency current that causes arcing while allowing safe operation during normal use, thereby preventing internal fires during maintenance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If electrical contacts are provided for easy installation and removal of the lamp, then user convenience is improved, but the risk of electric shock and internal arcing increases during relamping

Engineering Contradiction:

Improveinstallation and removal convenienceVSAvoidelectric shock and internal arcing risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent replaces mechanical electrical contacts with a non-contact coupling mechanism. This substitution maintains ease of installation and removal through simple mechanical insertion while eliminating electrical arcing and shock risks by using capacitive coupling or magnetic coupling instead of direct electrical contact during relamping operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If the LED driving circuit is directly connected to the electrical conductors for efficient power transfer, then energy efficiency is improved, but safety hazards increase during maintenance when exposed conductors are present

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidsafety hazards during maintenance

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary coupling mechanism (such as a capacitor or transformer) between the LED driving circuit and the electrical conductors. This intermediary maintains efficient power transfer through electromagnetic coupling while providing galvanic isolation that prevents electric shock and internal arcing during maintenance when conductors are exposed.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The galvanic isolation effectively limits through-lamp electric shock current to a safe level, preventing fatal shocks and internal fires, as demonstrated by compliance with safety standards like UL 935, and ensures reliable operation without mechanical actuation hazards.

Implementation Method 1

a galvanic isolation configured to prevent accidental LED current from reaching ground through a person's body

Methodology Applied

Scientific EffectGalvanic isolation:

Data Source

PatentUS9967927B2Linear solid-state lighting with galvanic isolation

Publication Date: 2018.05.08 ALEDDRA INC

AI summary

A linear light-emitting diode (LED)-based solid-state lamp comprising an LED driving circuit, LED arrays, at least one pair of electrical contacts, and a controller, is used to replace a fluorescent tube or a conventional LED tube lamp in an existing lamp fixture. The controller and the at least one pair of electrical contacts are configured to perform galvanic isolation between the controller and the LED driving circuit connecting with LED arrays. Thus an overall through-lamp electric shock current can be limited only from the controller, eliminating a substantial electric shock current flow through the LED driving circuit and subsequently the LED arrays. The scheme can effectively reduce a risk of electric shock and an internal fire hazard to users during relamping or maintenance.