Digital LED driver technology eliminates harmful flicker
March 22, 2012 // Christoph Hammerschmidt
With LEDs gaining traction in replacing incandescent bulbs, a downside of LED-based concepts is gaining visibility as well: There are concerns that the flicker associated with LED lamps might cause health problems - even epileptic seizures can be triggered by this phenomenon.
IEEE experiments suggest. US-based LED driver company iWatt claims that its technology avoids these problems. Two factors cause LED lamps to flicker. One is the mains grid frequency that can introduce low frequency flicker to the LEDs which, in contrast to incandescent bulbs, do switch on and off at the rhythm of the grid frequency - much in contrast to conventional incandescent bulbs which are simply to inert to react on the grid frequency. The other factor that transforms LED lamps into nervously flickering lights are dimmers - available dimming circuits frequently are optimized for incandescent bulbs; they cannot cope with quickly reacting light sources such as LED lamps. Both factors added can cause significant flicker - and while it is a known fact that many LED lamps perform poorly when used with an electronic dimmer. However, this flicker is not just annoying but it can cause health problems.
Experiments of the Institute of Electrical and Electronic Engineers (IEEE) have demonstrated that the flicker in a commercially available LED lamp can into a frequency range that is known to cause photosensitive epileptic seizure, explains Scott Brown, Vice President of Marketing for iWatt, Inc, a privately held company producing driver ICs for LED lamps.
The reason for the poor performance of LEDs under dimming conditions is that LED lighting and LED dimming is not a simple linear problem - some lamps exhibit visible flicker at low dimmer settings or do not work with the dimmer at all.
Brown claims that iWatt has created a technology that eliminates flicker in LED lighting. The company has developed a two-stage driver topology with patented digital control technology which eliminates flicker under all operating conditions, Brown promises. The algorithm implemented in iWatt's digital LED drivers maps the operating characteristics of dimmers and digitally filters the LED drive current, effectively eliminating voltage spikes that otherwise would cause flicker. The company has characterized a representative sample of dimmers available and implemented its algorithm accordingly, resulting in smooth dimming and ensuring the elimination of low frequency flicker. "Health concerns have to be taken seriously", Scott said. "But our LED driver technology provides a cost-effective solution to safely eliminate this problem".
For more information, visit www.iwatt.comAll news
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Internet of Things (IoT) manufacturer Ciseco has launched the Raspberry Pi ‘Wireless Inventors Kit’ (RasWIK), featuring 88 pieces to provide everything a Pi owner needs to follow a series of step-by-step projects or to create their own wireless devices, without the need for configuration or even writing code.
RasWIK has been designed to be highly accessible, demystifying the dark art of wireless and enabling anyone with basic computing skills to begin building wireless devices with a Raspberry Pi. You can create anything from a simple traffic light, to a battery monitor, or even a temperature gauge that sends data to the Xively IoT cloud so billions can access the data.This month, Ciseco is giving away twelve Raspberry Pi Wireless Inventors kits, worth £49.99 each for EETimes Europe's readers to win.
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In our previous reader offer, Farsens was giving away five kits for EEtimes Europe readers to evaluate its FenixVortex, Kineo and X1 wireless, battery free sensor tags.
Lucky winners include Mr A. Neil from the UK, Mr. E. Delvaux from Belgium, Mr Lengal from the Czech Republic, Mr H. Bijlsma from the Netherlands, and Mr G. Pfaff from Germany. All should be receiving their packages soon. Lets wish them some interesting findings with their projects.
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