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EMI Problems in TRIAC Dimmable LED Drivers

LED professional Review, Issue 35/2013

TRIAC dimming adds a dimension to Power Factor (PF) and Total Harmonic Distortion (THD) that is rarely defined by LED driver manufacturers. Bianca Aichinger, Product Marketing Manager at RECOM Lighting, examines the relationship between PF, THD and harmonics and explains why this relationship can change as soon as the LEDs are dimmed, thus causing increased EMI and undesirable visible effects such as LED flashing and flicker. The European standards for EMC and Harmonics are only specified for full load and in the non-dimmed condition. In practice, there are often dimmer/driver/LED load conditions which may meet the regulations when undimmed, but fail significantly if dimming is used.

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Keeping Thermal Runaway under Control

CIE Components in Electronics, Issue February 2012

An increasingly common method of increasing the light output from a high power LED cluster is to run parallel strings of LEDs from a single constant current source. But this Option is not without ist hazards. A typical high power 350mA white LED has a forward voltage (Vf) of about 3.3V, so if a cluster of ten LEDs were required in an application, connecting all the LEDs in series would require a driver capable of delivering at least 33V. If the supply voltage is 24VDC, then an expensive boost converter would be required with all the attendent EMC problems that can create.

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DC/DC Converters offer Flexibility when Designing LED Drivers

LED professional Review, Issue 29/2012

DC/DC converters are used in many of today’s applications and products. They also offer some advantages for developing LED drivers. Steve Roberts, Technical Director of the RECOM group explains these advantages and shows when a DC/DC converter is the first choice. For efficient and reliable LED lighting, the optimum matching of the driver to the LED must be taken into account besides a simple selection according to the required constant current. Until now it was common to always use an AC powered LED ballast, usually supplied as a kit with the purchase of the LEDs.

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