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Flex PCB Prototypes & Small Series NEW ! Flexible PCBs: • Favourable pricing – thanks to PCB-POOL ® production • Online Calculation • Made in Germany Email: sales@pcb-pool.com www.pcb-pool.com 1681 High performance in very hot conditions - For maximum pin temperature up to +155°C - Suitable for applications according to IEC 60335-1 - Screw-on or snap-in mounting schurter.com/gst PCB-POOL® is a registered trademark of Beta LAYOUT GmbH Making streets safer from dusk ‘til dawn starts with circuit protection By Johnny Chang and Tim Patel All around the world, cities and towns are steadily replacing their old high-intensity discharge street lights with LED luminaires. In contrast with the yellowish light cast by high-pressure sodium lamps, LED street lights produce whiter, cooler light, which enhances drivers’ depth of field and peripheral vision, reducing the potential for collisions. However, installing these new fixtures requires a substantial initial investment; planners must be able to justify the expense by getting a payback on their investment within a reasonable period based on LEDs’ lower wattage demands, lower maintenance costs, and longer operating life. In the United States, the Department of Energy’s (DOE) Municipal Solid-State Street Lighting Consortium (MSSLC), the Clinton Climate Initiative (CCI)/C40, and the Federal Energy Management Program (FEMP) worked in partnership to develop the Street and Parking Facility Lighting Retrofit Financial Analysis Tool for the financial analysis of retrofitting street and parking facility lighting with more efficient alternatives. Approximately one-third of the savings attributable to switching to LED street lights are the result of the extended lifetimes these fixtures offer. Their potential for reducing maintenance costs is essential to ensuring their long-term cost-effectiveness. Protecting outdoor LED lighting from lightning-induced surges requires diverting high voltage/current transient interference away from sensitive electronics in the lighting fixture. Various surge protective devices (SPDs) are used in outdoor LED lighting to suppress surge energy and minimize surge impact. LED lighting equipment manufacturers rely on a variety of surge protective devices (SPDs), including carefully chosen fuses, metal oxide varistors (MOVs), and transient voltage suppression (TVS) diodes to meet important regulatory and safety standards related to overvoltage transients. Figure 1 illustrates the various elements typically incorporated into a street light surge protection circuit. Although some LED luminaires feature surge protection devices embedded in the power supply unit, circuit protection device manufacturers often recommend that the surge protection circuit be kept separate from the luminaire power supply; in this way, luminaire manufacturers can easily market the same luminaire anywhere by attaching different surge protection modules to meet differing surge level requirements, based in part on lightning strike frequency data. Because of their fast response times, high surge energy handling, compact size, and cost-effectiveness, MOVs are widely used in surge protection circuits. However, after MOVs absorb a certain number of surge strikes, they will start to degrade and Johnny Chang is a Product Manager for Littelfuse’s Electronic Business Unit - www.littelfuse.com - He can be reached at jchang@Littelfuse.com Tim Patel is Technical Marketing Manager for Littelfuse’s Electronics Business Unit. He can be reached at tpatel@littelfuse.com www.electronics-eetimes.com Electronic Engineering Times Europe November 2015 37


EETE NOV 2015
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