Dimmer Circuit Nonzero Threshold Zero Crossing Detection

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Solution Overview

Problem

Conventional dimmer circuits face issues with accurate zero crossing detection due to noise-induced false triggering, particularly in active light source loads like LEDs and CFLs, leading to unpredictable control and potential flickering.

Innovation Solution

The dimmer circuit employs a nonzero threshold voltage detection method to identify zero crossings, setting the trigger point above zero volts to avoid false triggering, and incorporates switch unlatch monitoring and fourth quadrant firing control schemes to optimize switch operation and reduce power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If zero crossing detection is performed by detecting voltage polarity change at zero volts, then the dimmer can be synchronized with input line voltage phases, but noise-induced false triggering occurs leading to unpredictable control and flickering

Engineering Contradiction:

Improvezero crossing detection accuracyVSAvoidcontrol stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the detection parameter from zero-volt threshold to a nonzero threshold voltage level. By detecting zero crossings at a voltage threshold above zero (e.g., 1-5 volts), the system avoids false triggering caused by noise near the zero-crossing point while maintaining accurate synchronization with the AC line voltage phases.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If conventional zero crossing detection is used, then the dimmer can control switch firing times, but power consumption increases due to false firings and continuous monitoring

Engineering Contradiction:

Improveswitch control capabilityVSAvoiddimmer power consumption

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent extracts and removes the problematic continuous monitoring and false firing components from the system. By using nonzero threshold detection, the system eliminates false firings that would otherwise require continuous correction and additional power consumption, thereby reducing overall power usage while maintaining switch control capability.

Inventive Principle:

Principle #2Taking out (Extraction)

3Adaptability or versatility

If zero crossing detection is implemented in active light source loads like LEDs and CFLs, then the dimmer can control these loads, but noise from these active loads causes false triggering and unpredictable behavior

Engineering Contradiction:

Improvecompatibility with active light sourcesVSAvoidnoise-induced false triggering

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a nonzero voltage threshold as an intermediary filtering mechanism between the noisy active light source loads and the zero crossing detection circuitry. This threshold acts as a mediator that blocks noise signals below the threshold level while allowing legitimate zero crossing events to pass through, thereby eliminating false triggering caused by active load noise.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9974152B2Power efficient line synchronized dimmer

Publication Date: 2018.05.15 LEVITON MFG CO INC

AI summary

There is set forth herein a dimmer circuit for controlling delivery of input line voltage to a load. The dimmer circuit can include a switch coupling an input line voltage terminal to a load terminal. The dimmer circuit can be operative to provide one or more switch firing control scheme for latching the switch.