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EETE NOV 2015

Harwin Gecko EETimes Europe Nov 15.qxd:Layout 1 Long live the LED driver High Reliability in a compact package By Tom Freeman Ensuring your LED driver lasts as long as your LEDs requires careful scrutiny NEW Horizontal Styles launching Nov 2015 Harwin’s Gecko range offers new horizontal additions affording increased design flexibility, with the same high performance. - Horizontal connector for mother-daughter board configurations - Horizontal Gecko allows reduced PCB stacking height when used with cable connectors - Pin spacing - 1.25mm - 2A per contact - Resists shock and vibration - Locking latch and PCB retention features For evaluation samples, CAD models and technical specifications go to: www.harwin.com/gecko of the data sheets. The key advantage of switching to LED lighting is reduced costs, delivered primarily through energy efficiency (cutting electricity bills) and longer lifetimes (reduced maintenance). Take-up is accelerating in civic, industrial and commercial applications, as prices are falling and return on investment times are shortened. Even the domestic market is being wooed by the promise of lower electricity bills and more attractive lighting options. Meanwhile, LED technology is constantly evolving to offer yet further improvements in efficiency, brightness and power consumption, thereby increasing its application and appeal. Running alongside this march of technology, LED drivers are obliged to keep up. And the importance of the LED driver is often under-estimated. The LED driver plays a crucial role, not only in operating LED fixtures, but also in controlling their performance. The benefits anticipated with LEDs can all but be negated with the incorrect choice of driver. Designers have to take into account factors including dimming level, output voltage, operating temperature and output loading. The design and operating environment of the luminaire and fixture can make a huge difference to whether or when the luminaire needs to run at full load, when dimming can be used to significantly reduce power consumption, and how these parameters impact efficiency. In addition to the technical complexities, designers clearly want to select a driver with a ‘lifetime’ and reliability specification that matches the LEDs. But here’s the rub: in the technical and promotional literature, ‘guaranteed’ driver lifetime is often misrepresented. The first, and most obvious point is whether the driver actually comes with a warranty or guarantee (other than the statutory rights laws in force in that country); some may quote an ‘expected lifetime’, but with no guarantee that it will work in that period. If a particular unit does come with a manufacturer’s warranty or guarantee, then it is worth checking whether there are any special conditions or generic rules that come into play. Often there is conflicting information between a product datasheet and a manufacturer’s website in this regard. At least one manufacturer claims a product guarantee of five years on the datasheet, but states on the website just 24 months from date of manufacture. Next, note whether ‘lifetime’ is stated in hours or years, or both. Check the detail to determine if a five-year expected lifetime figure covers 24/7 use, for example. One mainstream manufacturer, promotes a ‘full five year guarantee’, but in the small print, assumes a maximum 5000 hours operation per year and, for devices with relay contacts, a maximum of 20 switches per day. Similarly, another household name in the lighting market offers a five-year warranty on LED drivers, but under its ‘special conditions’, notes that the warranty period is based on a maximum of 4000h per year. In this case, for a 24/7 application such as a hotel lobby, the terms of the warranty will be exceeded in less than six months! Turning up the heat Luminaire designers will already be aware that the temperature at which the LED driver is running plays a key role in determining its lifetime. They will already be paying close attention to operating temperature in their specific application, and even the ambient temperature, particularly within the fixture itself. However, when it comes to matching requirements with the LED driver, it is not always easy to interpret the figures presented in the datasheets. The hottest point of an LED driver is the maximum case temperature, or Tc (max). Although this is, in theory, the maximum operating temperature for the driver, many manufacturers will specify that the expected lifetime of their devices refers to a lower Tom Freeman is Sales Executive and Franchise Manager at Solid State Supplies Ltd – www.sssltd.com www.electronics-eetimes.com Electronic Engineering Times Europe November 2015 35


EETE NOV 2015
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