LED lamps are available in various shapes and constructions. Design is usually defined by the application of LED lamp. In this article construction of simple office luminary is examined and main emission sources determined.
Office LED lamp
Office LED lamp, close look
Office LED lamp without protective cover
LED arrays are mounted directly on LED lamp enclosure (without insulation), so enclosure acts as heat sink. All LED arrays are connected in series and connected to LED driver DC output. In front of LED driver there is EMI filter. This filter prototype was added by manufacturer afterwards they has bought coupe hundreds of “certified” LED drivers, assembled couple of LED lamps and sent to EMC laboratory, LVD laboratory and afterwards to certification. The only solution to get LED lamp certification was to add external EMI filter. Other solution was to donate all LED drivers for universities to educate new engineers, how not to design LED drivers.
Single LED lamp, without EMI filter, radiated emissions were high enough to damp all radio stations in 5m range. If such LED lams were installed in office, there could be high probability that some of office equipment were failing, due to electromagnetic interference. If such LED lamps were installed in hospital or other health care institutions, there could arise death threatening situations (depending on the EU country, it can lead up to long term prison sentence for LED lamp distributor). Another thread to manufacturer, who retails such un-compliant LED lamps, is market surveillance companies, who react on customer claims and verify market randomly taking out and testing samples.
LED lamp radiated emissions without EMI filter
LED lamp radiated emissions with manufacturer designed EMI filter
RF EMC DEVELOPMENT team was assigned to this case to optimize LED lamp EMI filter design, as manufacturers prototype design price was equivalent to LED driver price. The size of EMI filter was too big and radiated emissions was too close to limit line. RF EMC DEVELOPMENT had two solutions, integrate couple of passive components inside the LED driver or add extra filter at the AC input of LED driver. As LED lamp manufacturer, due to simplicity, chose to add external EMI filter. RF EMC DEVELOPMENT team developed filter prototype, consisting of few low-cost components, which decreased LED lamp total price and decreased radiated emissions.
Office LED lamp with RF EMC DEVELOPMENT optimized EMI filter prototype
LED lamp radiated emissions with RF EMC DEVELOPMENT designed EMI filter prototype
RF EMC DEVELOPMENT team recommends to make precompliance tests for LED lamps and LED lamp drivers before sending them to certification and accredited testing. It is a lot cheaper to make precompliance tests than make repeated accredited testing and certification.
RF EMC DEVELOPMENT offers EMC precompliance testing, accredited testing and development for LED drivers, LED lamps and other lighting equipment. We can provide evaluation of LED drivers quality, before they are installed in LED luminaries and give recomendations.
