Relay Arc Suppression Circuit Using Back-EMF Switch

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Solution Overview

Problem

Existing power supply circuits face premature relay contact failure due to harmful arcing during both closing and opening, which is costly and complex to mitigate with prior solutions.

Innovation Solution

A circuit design that suppresses arcing during relay opening by using a switch connected in parallel to the relay contacts, which provides supplemental power based on back EMF energy generated after relay activation, allowing beneficial arcing during closing to clean contacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If prior art circuits attempt to eliminate all arcing across relay contacts, then relay contact life is extended, but device complexity and cost increase significantly

Engineering Contradiction:

Improverelay contact lifeVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention segments the arcing phenomenon into two distinct phases: closing arc (beneficial for contact cleaning) and opening arc (harmful to contact life). By applying different approaches to each phase through the parallel switch configuration, the circuit selectively suppresses only the harmful opening arc while preserving the beneficial closing arc, thereby extending relay life without requiring complex suppression mechanisms for both phases.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The parallel switch acts as an intermediary element that redirects the harmful opening arc current away from the relay contacts. When the relay opens, the switch provides an alternative current path that bypasses the contacts, effectively mediating the arc suppression function without requiring complex sensing or control circuitry.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If prior art circuits use solid state devices to sense and reduce power during arcing, then contact arcing is reduced, but implementation cost increases

Engineering Contradiction:

Improverelay contact lifeVSAvoidimplementation cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention employs a simple parallel switch configuration that can be implemented with basic, inexpensive components rather than expensive solid state sensing devices. The circuit uses readily available elements such as diodes, resistors, and transistors in a straightforward configuration, dramatically reducing implementation cost while maintaining effective arc suppression functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The circuit utilizes the relay's own back-EMF voltage to automatically trigger the parallel switch during opening arc conditions. This self-service mechanism eliminates the need for external sensing circuits or complex control logic, as the relay's inherent electrical characteristics drive the suppression action automatically.

Inventive Principle:

Principle #25Self-service

3Object-affected harmful factors

If all contact arcing is suppressed, then harmful arcing is reduced, but beneficial contact cleaning operation is eliminated

Engineering Contradiction:

Improveharmful arcingVSAvoidcontact cleanliness

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The circuit dynamically adapts its behavior based on the relay's operational state. During closing, the parallel switch remains inactive allowing the cleaning arc to occur. During opening, the back-EMF triggered switch activates to suppress the harmful arc. This dynamic response ensures optimal contact maintenance while minimizing damage.

Inventive Principle:

Principle #15Dynamics

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

Extends relay life and reduces costs by minimizing arcing during opening while allowing beneficial arcing during closing, improving the reliability and longevity of power supply circuits with minimal incremental complexity and cost.

Implementation Method 1

The relay coil is configured for closing the relay contacts in response to receiving relay activating energy and for generating back EMF energy following termination of the receiving of the relay activating energy

Methodology Applied

Scientific EffectBack EMF: Electromagnetic Induction

Data Source

PatentUS7385791B2Apparatus and method for relay contact arc suppression

Publication Date: 2008.06.10 WATLOW ELECTRIC MANUFACTURING CO

AI summary

An arc suppression circuit for a power switch or power supply with a relay having a coil and a set of contacts for providing a portion of an input power as load power to an output. The relay coil is configured for closing the relay contacts in response to receiving relay activating energy and for generating back EMF energy following termination of the receiving of the relay activating energy. A switch is connected in parallel to the relay contacts and is configured for providing a portion of the input power as supplemental load power to the output as a function of back EMF energy. Also, a method of suppressing damaging arcing across relay contacts in a power switch or power supply includes receiving back EMF energy generated by the relay coil following termination of the relay coil receiving activating energy and connecting supplemental load power to the output in parallel with the relay contacts in response to the receiving of the back EMF energy.