Capacitive Coupling for Radio Interference Suppression in Class 2 Luminaires

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Solution Overview

Problem

Protection class 2 lamps face increased radio interference due to unconnected earth grounding, violating regulations and causing safety concerns, especially with electrically conductive mounting plates.

Innovation Solution

Incorporating a first capacitor to connect the mounting plate to a mains connection and a second capacitor to connect it to the ground, effectively damping oscillations caused by the inverter circuit, thus meeting radio interference suppression regulations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a protection class 2 luminaire uses control gear with an earth connection, then radio interference suppression is improved, but the luminaire structure becomes more complex and requires additional connections

Engineering Contradiction:

Improveradio interferenceVSAvoidluminaire structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The mounting plate serves as an intermediary element between the control gear and the capacitors. It provides a common connection point that allows the capacitors to couple the control gear's earth connection to both the phase conductor and neutral conductor, enabling radio interference suppression without requiring a separate protective conductor connection in protection class 2 luminaires

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mounting plate performs multiple functions: it mechanically supports the control gear, provides an electrical connection path for the capacitors, and serves as the reference potential for radio interference suppression. This multi-functionality eliminates the need for additional dedicated components for earth grounding

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Strength

If an electrically conductive mounting plate is used in protection class 2 luminaires, then mechanical stability and heat dissipation are improved, but radio interference increases

Engineering Contradiction:

Improvemechanical stabilityVSAvoidradio interference

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The capacitors act as intermediaries between the conductive mounting plate and the electrical conductors. They provide a coupled connection that allows the mounting plate to serve as an effective reference potential for radio interference suppression, while the oscillations from the inverter circuit are damped through the capacitive coupling to the phase and neutral conductors

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If protection class 2 luminaires are designed without earth connection, then safety for users is improved, but radio interference suppression capability deteriorates

Engineering Contradiction:

Improveuser safetyVSAvoidradio interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of connecting the earth terminal to a protective conductor as in protection class 1 devices, the invention inverts the approach by coupling the earth terminal to the phase and neutral conductors through capacitors. This creates an effective reference potential for radio interference suppression while maintaining the isolation characteristics required for protection class 2 safety

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the electrical connection parameters of the earth terminal from a direct conductive connection to a capacitive coupling. This parameter change allows the earth terminal to function effectively for radio interference suppression through the impedance characteristics of the capacitors, while maintaining the electrical isolation required for user safety in protection class 2 luminaires

Inventive Principle:

Principle #35Parameter changes

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 reduces radio interference to compliant levels, ensuring safety and regulatory compliance for protection class 2 lamps, and can be applied to other lighting types as well.

Implementation Method 1

a first capacitor (5) which couples the mounting plate (4) to one of the mains connections (L, N) and a second capacitor (6) which couples the mounting plate (4) to the ground connection

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP1799017B1Light for protection class 2

Publication Date: 2008.11.19 PATENT TREUHAND GESELLSCHAFT FUER ELECTRIC GLUEHLAMPEN M B H

AI summary

The fixture has an integrated electronic operating device (2) comprising two connections for supply voltage. An electrically conductive mounting plate and an earth connection are provided. A condenser (5) is coupled with the plate for connection with the supply voltage. Another condenser (6) is coupled with the plate for the earth connection, where values of the former and latter condensers are 2.2 and 1.5 nano Faradays.