LED Lighting Control Circuit for Triac Dimmer Flicker Reduction

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Solution Overview

Problem

LED lighting apparatuses using triac dimmers experience flicker due to low-angle rectified voltages and initial abnormal waveforms, which affect brightness control and stability.

Innovation Solution

A control circuit that includes a reference voltage supply unit, a flicker control unit, and switching circuits to regulate current paths for LED groups, comparing reference voltages to current sensing voltages and turning off paths during low-angle or abnormal waveform periods to prevent flicker.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a dimmer using triac is applied to control LED brightness, then brightness control function is achieved, but flicker occurs due to low-angle rectified voltage and initial abnormal waveforms

Engineering Contradiction:

Improvebrightness control functionVSAvoidflicker occurrence

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control circuit detects the initial abnormal waveform period of the rectified voltage at startup and skips LED driving during this period before normal operation begins. This preliminary detection and skipping action prevents flicker caused by abnormal initial waveforms while maintaining brightness control functionality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit continuously monitors the rectified voltage waveform and detects low-angle regions. When abnormal waveforms or low-angle regions are detected, the circuit adjusts or skips LED driving accordingly. This feedback mechanism eliminates flicker while preserving dimmer brightness control during normal operating conditions.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If triac characteristic differences are considered, then holding current varies causing flicker, but ignoring it leads to unstable operation

Engineering Contradiction:

Improvetriac characteristic adaptationVSAvoidoperation stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control circuit dynamically detects the actual waveform characteristics of the rectified voltage in real-time and adapts its driving strategy accordingly. Instead of using fixed holding current values, the circuit adjusts its operation based on detected waveform abnormalities, accommodating triac characteristic variations and preventing flicker while maintaining stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control circuit changes its operating parameters based on detected waveform conditions. When abnormal waveforms are detected, the circuit modifies its driving parameters or skips operation during problematic periods. This parameter adaptation allows the system to handle triac characteristic differences while maintaining stable operation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9572220B2LED lighting apparatus and control circuit thereof

Publication Date: 2017.02.14 SILICON WORKS CO LTD

AI summary

Disclosed are an LED lighting apparatus and a control circuit thereof which controls illumination of a lamp including LEDs using a dimmer. The LED lighting apparatus includes a flicker control unit which provides a control signal corresponding to a rectified voltage having a low angle corresponding to a preset low angle region and equal to or less than a preset level or detects an initial abnormal waveform diagram of the rectified voltage and provides a control signal corresponding to the abnormal waveform period, and controls a current path for light emission of the lamp.