Zero-Cross Relay Timing to Reduce Contact Bounce and Arcing

Solution Overview

Problem

Existing load control devices, such as relay switches, face issues with shortened lifetimes due to arcs and sparks caused by improper timing of relay actuation, leading to bouncing that results in wasted energy and potential welding of relay contacts, and reactive corrections for opening relays can result in undesirable arcing.

Innovation Solution

A load control device with a controllably conductive device and a zero-cross detect circuit that generates signals for identifying rising and falling edge times, allowing for precise control of relay actuation times to minimize bouncing and arcing by adjusting the actuation time based on the average bounce duration and zero-crossing times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If relay actuation is controlled to close at zero-crossing, then arcing is reduced, but relay contact bouncing occurs causing energy waste and potential welding

Engineering Contradiction:

ImprovearcingVSAvoidenergy waste from bouncing

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The control circuit initiates relay actuation in advance of the zero-crossing moment, accounting for the relay's inherent response time and contact bounce duration. By calculating the required lead time based on measured bounce characteristics, the system ensures contacts are fully settled before current flow resumes, preventing energy waste from bouncing while maintaining zero-crossing closure benefits

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system measures the actual contact bounce duration through detection circuits that monitor contact state changes, then uses this feedback information to dynamically adjust the actuation timing. This closed-loop approach optimizes the lead time parameter, ensuring accurate synchronization between actuation command and actual contact closure at zero-crossing

Inventive Principle:

Principle #23Feedback

2Stability of the object's composition

If relay actuation delay is increased to account for contact bounce, then contact settling is improved, but relay lifetime is shortened due to arcs at closure

Engineering Contradiction:

Improvecontact settling stabilityVSAvoidrelay lifetime

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of stationary object

Solution Approach 1:

The control circuit initiates relay actuation in advance of the zero-crossing moment, accounting for the relay's inherent response time and contact bounce duration. By calculating the required lead time based on measured bounce characteristics, the system ensures contacts are fully settled before current flow resumes, preventing energy waste from bouncing while maintaining zero-crossing closure benefits

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system measures the actual contact bounce duration through detection circuits that monitor contact state changes, then uses this feedback information to dynamically adjust the actuation timing. This closed-loop approach optimizes the lead time parameter, ensuring accurate synchronization between actuation command and actual contact closure at zero-crossing

Inventive Principle:

Principle #23Feedback

3Loss of energy

If relay actuation timing is adjusted to minimize bouncing, then energy loss is reduced, but precise timing control complexity increases

Engineering Contradiction:

Improveenergy loss from bouncingVSAvoidtiming control complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The control circuit automatically measures the relay's own contact bounce characteristics during operation and uses this self-diagnosed information to optimize actuation timing. The system extracts bounce duration from monitored contact state changes and autonomously calculates the appropriate lead time, eliminating the need for external calibration or complex predetermined timing tables

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system measures the actual contact bounce duration through detection circuits that monitor contact state changes, then uses this feedback information to dynamically adjust the actuation timing. This closed-loop approach optimizes the lead time parameter, ensuring accurate synchronization between actuation command and actual contact closure at zero-crossing

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11935714B2Controlling a controllably conductive device based on zero-crossing detection

Publication Date: 2024.03.19 LUTRON TECHNOLOGY COMPANY LLC

AI summary

A load control device may control power delivered to an electrical load from an AC power source. The load control device may include a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load, a zero-cross detect circuit configured to generate a zero-cross signal representative of the zero-crossings of an AC voltage. The zero-cross signal may be characterized by pulses occurring in time with the zero-crossings of the AC voltage. The load control device may include a control circuit operatively coupled to the controllably conductive device and the zero cross detect circuit. The control circuit may be configured to identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal, and may control a conductive state of the controllably conductive device based on the rising-edge time and the falling-edge time of the pulse.