The construction of a new building provides architects with an opportunity to embrace new technology to reduce the site’s lifetime carbon footprint. Solid-state lighting’s (SSL) high efficiency and longevity is making it the number one choice for lighting in environmentally-conscious projects.
Consumer electronics giant Apple, for example, has standardized on LED lighting for all facilities undergoing construction or major renovation. 1 However, fitting SSL to existing buildings brings several challenges. Conventional incandescent bulbs or fluorescent tubes run directly from the AC mains supply. In contrast, LEDs require a low-voltage, constant-current DC supply, so connecting SSL to legacy wiring demands the use of specialized power supplies known as LED drivers.
Theses LED drivers add expense, take up space, and generate heat. But, recently an alternative––which is particularly suited to modern office environments and which could significantly push down the cost of retrofitting SSL––has come to the fore: Power-over-Ethernet (PoE). PoE allows the wiring of a local area network (LAN) to carry both data and power to connected devices. This article explains the advantages of PoE-based LED lighting infrastructure over other wiring systems and describes how designers can implement PoE SSL solutions by taking advantage of the latest generation of wide-voltage input, constant-current LED drivers. Retrofitting LEDs A typical office environment is dominated by the steady cool-white glow of fluorescent lighting. While fluorescent tubes exhibit reasonable efficacy, averaging 60 to 100 lm/W, their electrical performance has been eclipsed by the latest generation of LED lights.
Even “mid-power” LEDs such as boast an efficacy of 122 lm/W (at 3 V and 150 mA). High-power devices (which are a little more expensive) such as can push out over 150 lm/W (at 2.95 V and 1.05 A). LEDs also boast longer lifetimes than fluorescent tubes. In normal use, an office manager might reasonably expect a fluorescent tube to last around 10,000 hours — LEDs routinely shine for five times as long; and fluorescent tubes do bring some environmental concerns due to the mercury used in the lights. The amount of mercury is small, but the health effects of this heavy metal are cumulative so careful disposal is required.
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No such toxic metal issue occurs with LEDs. It’s perhaps of little surprise then that companies such as Apple are keen to switch to SSL to illuminate their operations. Fluorescent tubes operate from an AC mains supply (some tubes can operate from a DC source, but this is unusual) at currents from 400 mA to 1.5 A. In contrast, LEDs operate from a constant-current, low-DC-voltage supply.
Operational characteristics vary from maker to maker, of course, but typically an LED demands a voltage between 2.8 to 3.5 V and a current between 150 mA and 2 A. The operational requirements for a popular high-brightness LED like for example, are a forward voltage of 2.8 V and a current of 700 mA to 1.5 A. LED drivers provide the solution. In addition to voltage regulation, can also interpret control signals to dim and change the color of the emitted light. The devices come in either constant voltage or constant current types. Constant-current drivers support both pulse width modulation (PWM) and constant-current reduction methods for adjusting the output current when dimming the LED. For example, has recently introduced the LED driver.
The product is a continuous-mode step-down (“buck”) voltage regulator, designed for driving single or multiple LEDs from a 7 to 36 V source. LED brightness control is achieved with PWM dimming from an analog or PWM input signal. Output current is up to 1.2 A.
Designers match the LED driver to the LEDs based on the application requirements, including factors such as the number of LEDs to be powered, the type of power supplied, and the functional characteristics of the LED. Some LED manufacturers offer “AC LEDs” which can screw straight into the socket vacated by a conventional bulb. The LEDs still have to be driven by a low-voltage DC source with the lighting manufacturer solving the problem by integrating a rectifier and LED driver into the light fixture with the downside of pushing up the unit’s price (See the TechZone article “ ”).
PoE offers a low-cost alternative to powering SSL from legacy wiring. Many offices already use PoE systems to network VoIP phones, wireless access points, modems and other building services such as security cameras and motion sensors, and it’s relatively simple and inexpensive to add LED lighting to such a network. A second major advantage is that the information-carrying capability of the Ethernet network endows SSL with a degree of intelligence, without the need to adopt the complex wireless technologies typically demanded by “smart” lighting. PoE first emerged as an answer to the problem of powering Voice over Internet Protocol (VoIP) phones.
In 2000, telecommunications equipment vendor Cisco introduced technology that allowed Ethernet cables to carry a 48 V DC supply to power VoIP phones. By June, 2003, the IEEE’s Ethernet subcommittee ratified the IEEE 802.3af PoE Standard. In 2009, a second standard, IEEE 802.3at, was ratified which defined a similar technology that could handle more power. IEEE 802.3af details a PoE technology designed to provide up to 15.4 W of DC power (minimum 44 V DC and 350 mA) to each device.
(Due to losses in the cable, only 12.95 W is guaranteed to be available at the equipment to be powered.) The technology uses a single, standard RJ45 connector and CAT 5 (or even CAT 3) cable, and can handle tens of watts (Figure 1). Figure 1: PoE uses a standard RJ45 connector and CAT 5 Cable. Power may be transmitted on the unused conductors of the Ethernet cable, since only two of the four pairs in CAT 5 cabling are required for the typical 10 to 100 Mbps Ethernet physical layers. Power also may be transmitted on the data conductors of the cable by applying a common-mode voltage to each pair — something which, because of Ethernet technology’s differential signaling, does not interfere with the cable’s data transmission.
IEEE 802.3af defines two types of PoE devices, Power Sourcing Equipment (PSE) and the Powered Device (PD). A PSE draws power from its own conventional power supply and then manages the power sent over the Ethernet cable network to the PD, which takes the power it needs via an RJ45 connector without needing a built-in power supply.
PoE is able to power PDs over typical Ethernet cable runs of up to tens of meters (Figure 2, based on the PoE controller. Also see the TechZone article “ ”). Figure 2: A PoE endpoint power-insertion implementation. (Courtesy of Maxim Integrated) PoE adds intelligence SSL is a key component of the “smart home” — a dwelling where networked services and appliances automate many routine tasks. By connecting lights to powerful computing devices such as proprietary controllers, smartphones, tablets, and PCs, SSL systems are, for example, “future proofed” and able to take advantage of the emerging capabilities of the Internet of Things (IoT). Connecting SSL to an existing PoE local area network (LAN) adds intelligence to the system without the added complexity and expense of a wireless connection.
In a PoE configuration, each SSL is effectively a standard RJ45 connector “plug-and-play” device with its own Internet Protocol (IP) address. That plug-and-play device could also incorporate sensors (for example to detect ambient-light levels and adjust the light’s output accordingly) and even additional capabilities such as acting as a wireless access point. The PoE connection enables each SSL to send real-time information about the local environment such that, for example, temperature and humidity could be more precisely adjusted (Figure 3). Figure 3: A PoE-connected LED light can incorporate sensors sending data back to a central controller. (Courtesy of Maxim) PoE-connected SSL also offers operational advantages over conventionally powered lighting, particularly in emergency situations. For example, in emergency situations the lights could illuminate safe routes out of a building or indicate hazardous areas by changing color.
Maxim Integrated has produced an application note 3 that describes the advantages of PoE-connected LEDs compared to legacy infrastructure-powered systems. PoE-compliant LED drivers From a lighting designer’s perspective, the key advantage of PoE-connected SSL is the reduction in complexity of the LED light’s power supply.
This makes the LED product easier to design, less expensive, and more compact while also easing thermal management challenges. LED lights connected to a PoE sockets act as PDs, drawing clean, regulated DC power from the network without requiring a primary power regulation stage to convert from AC to DC and step-down the mains voltage. However, PoE’s (nominally) 44 V DC supply is unsuitable to directly power the LEDs because of their requirement for a carefully controlled constant-current, constant-voltage source. There are many DC-to-DC LED drivers suitable for regulation of a PoE supply. Some manufacturers go so far as to state that their devices are “PoE-compliant” while others don’t mention compliancy even though their devices can safely be used in a PD. A “compliant” LED driver is essentially one which can accept an input voltage in the PoE operating range (nominally 44 V DC but typically across a range of 37-57 V).
However, there are some rules governing the compliancy of a PD as a complete unit. For example, in addition to standardizing existing practice for spare-pair and common-mode data-pair power transmission, the PoE standard provides for signaling between the PSE and PD. This signaling allows conforming devices to be detected by the PSE, avoiding damage to non-PoE devices attached to a network. To detect a PD, the PSE applies a DC voltage between 2.8 and 10 V across the conductor and determines if there is a PD connected by measuring the loop current.
The PD should present a resistive load between 19 and 27 kΩ with a parallel capacitor of 120 nF or less as a “signature.” is a suitable LED driver for PoE lighting. The device features a wide voltage-input range of 6.5 to 65 V (nicely accommodating PoE’s 37-57 V input range) and provides a constant output current of up to 1 A with ±3 percent accuracy. A dedicated PWM input enables pulsed LED dimming over a wide range of brightness levels. The 2 MHz switching encourages the use of smaller magnetic components. Efficiency is claimed to be around 95 percent when driving five LEDs in series from a 45 V input. An analog thermal-foldback feature reduces LED current when the temperature of the LED string exceeds a specified point. Figure 4 shows a typical application circuit for the MAX16832.
Figure 4: Application circuit for the Maxim MAX16832 LED driver. Although the company doesn’t promote its buck LED driver specifically for PoE applications, chip is a suitable basis for a PoE-compliant product’s power supply. The ILD6070 is designed for driving high-power LEDs in general lighting applications with average currents up to 0.7 A with ±3 percent accuracy over the input voltage range. The chip’s input range is 4.5 to 60 V and a multifunctional PWM input signal allows dimming of the LEDs with an analog DC voltage or an external PWM signal. An integrated over-temperature protection circuit reduces LED current once the adjustable junction temperature threshold of the IC is exceeded.
The company says the efficiency of the LED driver can reach 98 percent over a wide range. Similarly, (TI) supplies several wide-input buck LED drivers that are suitable for PoE-connected LED light applications. A good example is the, a constant-current device with an input voltage range of 4 to 65 V which is able to supply up to 1 A at ±3 percent accuracy. Efficiency is claimed to be up to 96 percent. The company’s proprietary Pulse-Level-Modulation (PLM) control method is said to ensure high-conversion efficiency and true average-current regulation. Plug-and-play LED lights For office facilities already equipped with PoE LANs, retrofitting SSL to the network offers an inexpensive way to enjoy the advantages of LED lighting.
Because the infrastructure is already in place considerable saving can be made on wiring and professional labor. Not only can the lights simply be plugged in to an RJ45 connector socket but also the information-carrying capability of the network adds intelligence without the added expense and complexity of wireless connectivity. For the designer of retrofit LED lights, offering a PoE version of their product is a promising route for increasing sales. Moreover, because the design doesn’t require the relatively inefficient rectification and initial voltage step-down stage, the power supply for the LED light can be made smaller, less complex, cheaper, and more efficient. Many silicon vendors offer a range of integrated buck DC-to-DC LED drivers with wide voltage-input ranges that are suitable for the power supplies of PoE-connected LED lights.
However, it is the designer’s responsibility to ensure that their product meets the IEEE802.3at or af standards before they can be sold as “PoE-complaint” products. For more information on the parts mentioned in this article, click on the links supplied to access product pages on the Digi-Key website. References:. “ Environmental Responsibility Report,” Apple, May 2015.
“ The Bright New Outlook For LEDs: New Drivers, New Possibilities,” Alec M. Makdessian, Director, Business Management, Maxim Integrated, 2015. “ PoE and LED Lighting: the Perfect Match,” Application note 6141, Maxim Integrated, 2014.
Disclaimer: The opinions, beliefs, and viewpoints expressed by the various authors and/or forum participants on this website do not necessarily reflect the opinions, beliefs, and viewpoints of Digi-Key Electronics or official policies of Digi-Key Electronics.
Similar words: (1.00) (1.00) (0.50) (0.50) (0.50) stA Spanning Tree Algorithm stB strobe stC Set Carry Flag stD I Sacrae Theologiae Doctor (doctor of sacred theology) noun doktor Svyashennogo Bogosloviya II Sexually Transmitted Disease noun zabolevanie, peredavaemoe polovym putem stD;.1. Set Direction Flag;.2. Standard stDA streetTalk Directory Assi stance Banyan stDAUX standard Auxillary stDERR standard Error stDIN standard Input stDIO.H standard Input/Output Header C stDMA Space-Time Division Multiple Access, mnozhestvennyi dostup s prostranstvenno-vremennym razdeleniem kanalov stDOUT standard Output stDPRN standard Printer stF structured File (file name extension) Lotus Agenda stI Set Interrupt Flag stN Supertwi st Nematic stOL port Short TakeOff and Landing airport noun aeroport dlya samoletov s ukorochennym probegom stOS store string stP Signal Transfer Point stP;.1. Shielded Twi sted Pair, ekranirovannaya vitaya para-;.2. Signal Transfer Point, punkt peredachi signala (v seti) stR;.1. Store Task Regi ster;.2. Synchronous Transmitter Receiver stRUDL structural Design Language (Programming Language) stScI Space Telescope Science In stitute stX 1 ( start of text) simvol 'nachalo teksta'.
Upravlyayushii simvol, ukazyvayushii na nachalo peredavayaemoi informacii v startstopnom rezhime. V kode ASCII predstavlen chislom 2 st-John's-wort noun bot. John's evil epilepsiya st. Street noun ulica st. Vitus's dance plyaska sv. Vitta (bolezn') sta station noun stanciya stabat Mater 1 Stabat Mater (srednevekovaya katolicheskaya horovaya kompoziciya) stafford(shire) noun Stafford(shir) staffs. Staffordshire noun Staffordshir (grafstvo v Anglii) stagirite 1 ist.
Stagirit, urozhenec Stagiry (v Drevnei Makedonii) 2 (the stagirite) Stagirit, Aristotel' stamp Act 1 am. Zakon o gerbovom sbore stanislas noun Stanislav stanislaus noun Stanislav stanley noun Stenli, Stanli stannaries 1 Olovyannye rudniki (olovodobyvayushii i olovoplavil'nyi raion v Kornuolle i Devonshire) star Chamber 1 ist. Zvezdnaya palata (vysshii korolevskii sud v Anglii, uprazdnennyi v 1641 g.) 2 tainyi, nepravednyi sud, sudilishe; zastenok star of Bethlehem 1 rel. Vifleemskaya zvezda 2 pticemlechnik zontichnyi (Ornithogalum ambellatum) stars and Bars 1 am. 'zvezdy i perekladiny', flag Konfederacii yuzhnyh shtatov stars and stripes 1 'zvezdy i polosy', gosuzharstvennyi flag SShA state Attorney 1 am. Prokuror shtata state Bank of Con struction 1 Vsesoyuznyi bank finansirovaniya kapital'nyh vlozhenii (Stroibank SSSR) state Bank of the USSR 1 Gosudarstvennyi bank SSSR (Gosbank SSSR) state Committee of the USSR Council of Mini sters for Labour and Wages 1 Gosudarstvennyi komitet SSSR po voprosam truda i zarabotnoi platy state Department 1 razg.
Gosudarstvennyi departament (ministerstvo inostrannyh del SShA) state of the state message 1 am. Ezhegodnyi doklad gubernatora shtata zakonodatel'nomu sobraniyu state of the Union message 1 am. Doklad prezidenta kongressu o polozhenii strany state of the World message 1 am. Doklad prezidenta kongressu o mezhdunarodnom polozhenii state's Attorney 1 am. Prokuror shtata state-house noun amer. Zdanie zakonodatel'nogo organa shtata statehouse 1 am.
Zdanie zakonodatel'nogo organa shtata 2 ist. Ratusha states General 1 ist. General'nye shtaty states' righter 1 am.
Storonnik ohrany i rasshireniya prav shtatov; protivnik vmeshatel'stva federal'nogo pravitel'stva v dela otdel'nyh shtatov states' rights 1 am. Prava otdel'nyh shtatov (ustanovlennye konstituciei SShA) stateside, stateside 1 am. Otnosyashiisya k SShA, amerikanskii Ex: stateside, stateside cu stom amerikanskii obychai Ex: transferred from Europe to stateside, stateside duty perevedennyi iz Evropy na sluzhbu v SShA 2 am. V SShA Ex: to go stateside, stateside vernut'sya na rodinu, domoi (ob amerikance) statesider, statesider 1 am.
Korennoi amerikanec; grazhdanin SShA stationery Office 1 gosudarstvennaya kancelyariya (v Velikobritanii; izdaet pravitel'stvennye dokumenty) stati stical department 1 Statisticheskoe upravlenie statute of We stmin ster 1 Vestminsterskii statut (1931 g.; akt parlamenta o pravovom polozhenii britanskih dominionov) steinberger 1 nem. Shteinberger (beloe vino) stella noun Stella sten gun 1 pulemet sistemy Stena sten, sten 1 pulemet sistemy Stena stentor 1 Stentor (gromoglasnyi glashatai v 'Iliade') 2 (obykn. S.) gromoglasnyi chelovek (ob oratore, d'yakone i t. P.) 3 (s.) zool. Infuzoriya-trubach ( stentor roeseli) stephana noun Stefaniya stephanie noun Stefaniya stephen noun Stiv(e)n- Stefan steve noun- dim. Of stephen Stiv stilton 1 stilton (sort zhirnogo syra; tzh. Stilton cheese) stirling(shire) noun Sterling(shir) stockholm noun g.
Stokgol'm stone Age 1 kamennyi vek stormont 1 ist. Stormont (avtonomnyi parlament Severnoi Irlandii; 1920-1972) storthing 1 storting (parlament Norvegii) str I strait noun proliv II street noun ulica straits Settlements 1 ist.
Britanskie vladeniya na p-ve Malakka strasbourg noun g. Strasburg strategic Air Command 1 strategicheskoe aviacionnoe komandovanie (VVS SShA; tzh. USAF strategic Air Command) stratford-on-Avon noun g. Stratford-on-Eivon, Stratford-na-Eivone street 1 am. Wall street Uoll-strit, n'yu-iorkskii denezhnyi rynok, amerikanskii finansovyi kapital, angl. Ulicy poblizosti ot zdaniya fondovoi birzhi, neoficial'naya birzha, vnebirzhevoi oborot strewth!
Vozglas udivleniya (avstr. Sleng) strine 1 razg. Avstraliiskii dialekt angliiskogo yazyka 2 razg. Avstraliiskii sturm und Drang 1 nem. 'Burya i natisk' (techenie v nemeckoi literature konca XVIII v.) sturmabteilung 1 nem. Otryad shturmovikov, otryad SA stygian 1 grech.
Stigiiskii, otnosyashiisya k reke Stiks 2 (tzh. Mrachnyi; adskii Ex: stygian gloom (darkness) adskii mrak 3 (tzh. Nerushimyi (o klyatve) styx 1 mif.
Stiks (reka) Id: to cross the styx umeret' st I state noun gosudarstvo II st - saint noun svyatoi III st - standard Time noun poyasnoe vremya stab 1 udar (nozhom, kinzhalom i t. P.) Ex: stab in the back udar v spinu; predatel'skii udar 2 kolotaya rana 3 vnezapnaya ostraya bol', ukol (tzh. Stab of pain) Ex: stab of lumbago pristup ishiasa 4 pristup, vnezapno nakativshee chuvstvo Ex: stab of anxiety vnezapnoe chuvstvo trevogi Ex: stab of joy (vnezapnyi) priliv radosti Ex: a stab of pity ran through her ee ohvatila volna sostradaniya 5 rezkii korotkii udar (bil'yard) 6 razg. Popytka Ex: to make a stab at conversation pytat'sya zavyazat' besedu 7 nanosit' udar (nozhom, kinzhalom) 8 vonzat' (nozh i t. P.); kolot' (shtykom) Ex: to stab a knife into smb.'
S heart vonzit' nozh komu-l. V serdce Ex: to stab in the back vsadit' nozh v spinu; nanesti predatel'skii udar; zloslovit' za spinoi u kogo-l. 9 ranit' (ostrym oruzhiem); zakolot' (tzh.
To stab to death) Ex: to stab oneself with a dagger zakolot'sya kinzhalom Ex: to stab at smb. Zamahnut'sya na kogo-l. P.; nanesti komu-l.
Kolotuyu ranu 10 tykat' Ex: he stabbed me in the che st with his finger on tknul menya pal'cem v grud' Ex: the speaker was stabbing the air in anger v gneve orator potryasal kulakom 11 razg. Nanosit' usherb, terzat' Ex: to stab at smb.' S reputation porochit' ch'yu-l. Reputaciyu 12 strelyat', kolot' (o bolevom oshushenii) 13 obbivat' stenu (pod shtukaturku) 14 poligr. Prokalyvat' otverstiya v koreshkovoi chasti bloka 15 (sokr. Ot e stablishment) razg. Shtat Ex: on (the) stab v shtate stab-awl 1 shilo stab-rag 1 voen.
Polkovoi portnoi stab-wound 1 kolotaya rana stabber 1 s-h. Shup, probnik (dlya vzyatiya prob zerna) stabbing 1 pronzitel'nyi, ostryi Ex: stabbing glare svet, rezhushii glaza; oslepitel'nyi svet Ex: stabbing pain rezkaya (ostraya, vnezapnaya) bol' stabile 1 isk. Abstraktnaya skul'ptura iz listovogo zheleza, provoloki i dereva 2 stabil'nyi, nepodvizhnyi 3 med. Ustoichivyi, nelabil'nyi 4 stoikii, ne podverzhennyi korrozii stability 1 ustoichivost', stabil'nost', prochnost' stability 1 ustoichivost', stabil'nost'; sostoyanie ravnovesiya Ex: dome stic stability vnutrennyaya ustoichivost' Ex: family stability postoyanstvo sostava sem'i (demografiya); prochnost' semeinyh otnoshenii Ex: to secure the stability of peace obespechit' prochnyi mir 2 postoyanstvo, nepokolebimost', tverdost' (haraktera, ubezhdenii, resheniya) Ex: man of stability nadezhnyi chelovek Ex: man of no stability chelovek, na kotorogo nel'zya polozhit'sya 3 teh. Prochnost', krepost'; zhestkost' 4 av. Ostoichivost', ustoichivost' stabilization 1 stabilizaciya, uprochenie (kursa) stabilization 1 stabilizaciya, uprochenie Ex: stabilization of currency stabilizaciya valyuty, ustanovlenie valyutnogo pariteta Ex: wage-and-price stabilization stabilizaciya cen i zarplaty 2 voen. Obrazovanie ustoichivoi linii fronta 3 voen.
Perehod k pozicionnoi voine stabilization fund 1 fond dlya stabilizacii valyuty stabilization of currency 1 stabilizaciya valyuty, ustanovlenie valyutnogo pariteta stabilization of exchange 1 stabilizaciya kursa valyuty stabilization of prices 1 stabilizaciya cen stabilizator = stabilizer stabilize 1 stabilizirovat', delat' ustoichivym stabilize 1 stabilizirovat', uprochit' Ex: to stabilize the dollar stabilizirovat' kurs dollara Ex: to stabilize the front voen. Stabilizirovat' polozhenie na fronte; pereiti k pozicionnoi voine 2 stabilizirovat'sya, uprochit'sya, priobresti ustoichivost' Ex: prices stabilized ceny stabilizirovalis' 3 av. Pridavat' ostoichivost' stabilized 1 stabilizirovannyi, ustoichivyi Ex: stabilized warfare pozicionnaya voina Ex: stabilized road dor.
Uluchshennaya doroga stabilized 1 stabil'nyi, ustoichivyi stabilizer 1 spec. Stabilizator 2 reakt. Stabiliziruyushii komponent (topliva) stable 1 konyushnya 2 hlev, stoilo, zakut Ex: stable fattening s-h. Stankovyi otkorm Ex: stable sy stem s-h. Stoilovoe soderzhanie (skota) Ex: stable climate s-h.
Mikroklimat zhivotnovodcheskogo pomesheniya 3 prenebr. Hlev (o zapushennom pomeshenii) 4 konyushnya, begovye loshadi, prinadlezhashie odnomu vladel'cu 5 manezh 6 vladel'cy konyushni; obsluzhivayushii personal konyushni 7 razg. Gruppa pod edinym nachalom; gruppa sportsmenov, rukovodimaya odnim menedzherom; hudozhniki, aktery, zavisyashie ot odnogo agenta i t.
8 prostorech. Orava, orda, vyvodok Ex: a comedian keeps a stable of gag writers pri komike vsegda sostoit orava sochinitelei repriz (ostrot) 9 organizaciya s filialami Ex: a stable of publication izdatel'stvo, vypuskayushee neskol'ko zhurnalov, gazet i t. Dezhurstvo po konyushne Id: to be out of the same stable prinadlezhat' k odnomu krugu (osob. Privilegirovannomu) Id: stable push sl.