AC LED Driver Circuit Eliminates Triac Dimmer Flicker

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Solution Overview

Problem

AC direct LED lighting systems using triac dimmers often experience flicker phenomena due to differences in turn-on characteristics, leading to discomfort for users as the LEDs' lighting times deviate, causing a deviation in LED driving time.

Innovation Solution

A circuit and method that include a triac dimmer, a charger, a reference voltage generator, and a driving signal output unit to regulate the brightness and delay the LED module's lighting until a reference voltage is reached, ensuring uniform turn-off times and preventing flicker by synchronizing the LED driving signal with the triac dimmer's operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of stationary object

If a triac dimmer is used to control LED brightness in an AC direct lighting system, then the system becomes lighter and more compact, but the turn-on characteristic of the triac dimmer causes deviation in LED driving time and generates flicker phenomenon

Engineering Contradiction:

Improvesystem weightVSAvoidLED driving time consistency

Core Design Contradiction:

Weight of stationary objectVSReliability

Solution Approach 1:

The circuit charges a capacitor during the triac dimmer's turn-off period before the LED is supposed to turn on. This preliminary charging action ensures that the LED receives a consistent driving signal regardless of the triac dimmer's turn-on characteristic variations, thereby eliminating flicker while maintaining the AC direct driving benefits.

Inventive Principle:

Principle #10Preliminary action

2Speed

If the LED module is driven immediately by the rectified AC input voltage, then the lighting response is fast, but the turn-on time deviation of the dimmer causes flicker phenomenon

Engineering Contradiction:

Improvelighting response speedVSAvoidflicker phenomenon

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The circuit performs preliminary charging of a capacitor during the dimmer's turn-off period before activating the LED. This preliminary action delays the LED turn-on until the capacitor is sufficiently charged, synchronizing the LED driving time and eliminating flicker while maintaining fast response.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A capacitor is introduced as an intermediary energy storage element between the rectified AC voltage and the LED module. This intermediary component buffers the voltage and provides a consistent charging process that synchronizes LED activation, preventing flicker caused by direct connection to the dimmer-controlled AC voltage.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the LED module is driven immediately by the rectified AC input voltage, then the lighting response is fast, but the turn-on time deviation of the dimmer causes flicker phenomenon

Engineering Contradiction:

Improvelighting efficiencyVSAvoidflicker phenomenon

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

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

The solution effectively removes the deviation in LED driving time caused by the triac dimmer's turn-on characteristic, preventing the flicker phenomenon and maintaining a uniform light output.

Implementation Method 1

a charger configured to be charged during a turn-off period of the triac dimmer

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a reference voltage generator configured to generate a reference voltage based on a voltage charged in the charger during a first turn-off period of the triac dimmer and a voltage charged in the charger during a second turn-off period

Methodology Applied

Scientific EffectVoltage regulation:

Implementation Method 3

a driving signal output unit configured to output a driving signal of the LED module in response to a voltage charged in a third turn-off period of the triac dimmer reaching the generated reference voltage

Methodology Applied

Scientific EffectElectrical control of LED emission: Light Emitting Diode

Data Source

PatentUS9693406B2Circuit for driving AC direct lighting apparatus and method therefor

Publication Date: 2017.06.27 MAGNACHIP SEMICON LTD

AI summary

Disclosed is a circuit for driving an AC direct lighting apparatus, including a triac dimmer configured to control a brightness of an LED module, a charger configured to be charged during a turn-off period of the triac dimmer, a reference voltage generator configured to generate a reference voltage based on a voltage charged in the charger during a first turn-off period of the triac dimmer and a voltage charged in the charger during a second turn-off period, and a driving signal output unit configured to output a driving signal of the LED module in response to a voltage charged in a third turn-off period of the triac dimmer reaching the generated reference voltage. Accordingly, the driving circuit manages a driving time deviation of the LED module, removing a flicker phenomenon from the light produced by the module.