Want To Dim Your LEDs with a TRIAC Dimmer?

Focus:

Triacs provide a simple, low-cost solution for dimming incandescent lamps. But standard TRIAC dimmers cannot be used with LED lamps because LEDs have faster turn-on and turn-off times than incandesents. So using a TRIAC based dimmer with LEDs produces visible flicker. This article describes a dimming circuit based on National Semiconductor's LM3455 LED driver IC, which allows an LED lamp to be dimmed (without flickering) using a standard TRIAC dimmer. The IC translates the TRIAC dimmer trigger point into an average current that can be used to control and drive a string of LEDs. The article describes how the dimmer circuit works when driving a single string of LEDs and then describes how multiple LM3445 ICs can be used in a master/slave configuration for dimming multiple LED strings.

What you’ll learn:

• How to build a dimmer circuit for LED lamps that is controlled by a standard TRIAC dimmer
• How to dim one or more strings of LEDs using a standard TRIAC dimmer

Notes:

Article appears on pages 36-37 of March issue in article archive. You must register to access articles in this magazine's archive.

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Author & Publication:

Ernest Bron, Field Applications Engineer, National Semiconductor Europe, Bodo's Power Systems, Mar 01 2009

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