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          提防LED十萬小時使用壽命之說- LED vs Cold Cathode
          作者:Dan Watt

          每次看到有關LED的報道,總會注明它有十萬小時的壽命,這意味你安裝它后便可安枕無憂地連續可使用超過11年了,這般通用的聲言就讓不少人習慣性地接受這是無可非議的事實。

          但事實并非如此… 一顆抗UV環氧樹脂5mm LED 二極管燈在全電流和高溫下工作,在一千小時內它的光輸出將會縮減一半... 在建筑照明的應用上,工程維護和能源成本為最關鍵的因素,因此使用冷陰極管仍是最理想的選擇。

          讓我們以典型的白色LED與直徑25mm暖白色冷極管在常規照明應用的情況下做個比較, 下圖即為我們展示實驗得出的二者的表現。

           

          Best Supply Ltd. HK

          LED標榜其專業燈光應用,但并不一定是所有燈光照明的最佳答案。當你分析LED的技術規格或說明書時,你會發現,沒有寫明的東西比寫明的東西更為重要,一定要好好考慮清楚!

          冷陰極管已是很成熟和被技術得到證實有很多優點的產品, 因此當我們把所有關鍵問題都整合在一起考慮,并需要在兩者間做個選擇的話,很明顯地,冷陰極管仍然能提供比LED更多的好處。

          注:本文借鑒 Dan Watt先生相關觀點和言論
          Dan Watts 是美國一名燈光技術顧問和電路設計工程師,擁有50多年電氣工程經驗。主要專注于燈光行業應用的電源設計,曾在著名的Micro Lamps公司(高級LED及燈光材料供應商)擔任3年技術總裁,常被受邀于全美各重大燈光會議上演講。

           

          LED vs. Cold Cathode -Beware of the 100,000 hour LED myth

          Every time you see anything regarding LEDs, it is always stated that they have a 100,000 hour life expectancy. This implies that you can just install them and forget about them for more than 11 years of continuous use. This claim is so common that most people have come to accept it as hard fact.
          The reality is quite different… A 5mm epoxy UV LED working at full current and an elevated tem-perature, may have its output decreased to 50% in less than 1,000 hours… In architectural lighting applications, where maintenance and energy costs are important, a superior choice is still Cold Cathode lamps.
          Let’s compare typical white LEDs with 25m diameter warm white Cold Cathode lamps for general illumination applications. The table below shows the typical performance ranges for both.

           

          LEDs are here to stay for specialty lighting applications, but are not necessarily the best answer to most lighting needs. When looking at a data sheet or specifications for LEDs, what is left out can be more important than what is put in. Do your homework carefully.
          Cold Cathode lamps are a mature, proven technology with many benefits. When all key issues are taken into account, it is clear that Cold Cathode lamps still have much to offer over LEDs.

          Source: Dan Watts
          Mr Watts is an independent technical consultant and circuit design engineer. He has over 50 years of electrical engineering experience. Much of his design work has focused on power supplies and ballast design for the lighting industry. He served as Director of Engineering for three years at Micro Lamps Inc., a supplier of premium LEDs and other light sources. He has presented numerous papers at na-tional lighting conferences.

           

          冷陰極管與LED用于燈槽的比較, 作者:Luc Steegmans

           

          LED在這幾年間被應用于很多領域和項目中,它無疑是槽型字、廣告牌、家具裝飾、自動售賣機以至扶手電梯裝飾等之最佳光源,但這些對光的強度和色彩渲染的要求都不大,然而這兩點卻為暗槽燈/天花照明(Cove Lighting) 所產生的氛圍環境的燈光效果之關鍵因素。

          暗槽燈的燈光應該是高亮光且介乎在色溫2400K 至 3000K之間。若使用冷陰極管,能產生甚至超過燈管本身長度的高亮光。由于光線均勻分布于燈管表面每處,將不會有任何黑點出現在燈光所照附近。所以如果使冷極管貼合天花的話,整個天花會被很均勻地照亮;如果想效果更佳,你可在暗槽內涂上金漆,這反射的燈光會使裝飾效果更金壁輝煌。

          然而,以LED本身的條件是很難應用于天花照明的;蛘邠Q句話來說,問題在于LED光源與天花之間的距離太近,而LED本身是點光源的緣故,它的光在不足夠的距離下很難平均分布于天花的表面。LED本身是帶方向性的細小點光源(即局部光源),有任何物體處于光源與墻壁之間,都會產生黑影投射到墻壁上。當然人們可以每米增加更多更密集的LED燈珠,但也是不能完全解決黑影的問題。從節能的角度來說,要達到同樣亮度的話,冷極管是比LED要更勝一籌。

          再者,色溫,尤其是在2400K至3000K之間的色溫,LED是很難達到的。人們應該要認識到的是,所謂的某一色溫是分列在色譜上某特定的范圍內的不同位置都能得出的數值,都可以被稱為同一色溫,但其實所謂的同一色溫不是一定給人同樣的感覺。

          最后關于保養維護方面,根據30年來的實踐經驗證明,作為天花暗槽燈照明光源的冷陰極管可以在極少的維護下維持使用很長時間,10年不間斷的工作運行也是很普通正常的。但LED的真實平均使用壽命,那就只有未來才能知道了。 雖然它被應用在裝飾照明方面才不過四年左右的時間但已出現很多顯著的失敗事故, 這大概是因為暗槽內的高溫對LED的穩定性造成影響。在不能降溫的情況下工作對LED來說是非常不利的,而冷陰極管就不會受高溫影響。

          如果暗槽天花照明是你房間的主要光源的話,就要注意燈光的充足亮度,合適的色溫以及最少的維護保養,在這種情況下,冷陰極管毫無疑問比LED更勝一籌。

          注:本文借鑒Luc Steegmans樂思迪文先生相關觀點和言論
          Luc Steegmans 是一位認證電力工程師,現任歐洲標識聯盟(ESF (www.eu-signs.org)的主席并曾擔任過該協會的技術委員會主席數年,也是其他不同協會的技術顧問;他是比利時Elbo Signs and Technology nv標識公司的總裁,與眾多國際標識公司合作,項目遍布全球75個國家。

           

           

          Cold cathode lighting vs led lighting with coves- by Luc Steegmans

          In recent years leds have been successfully used in many applications. It has been a suitable solution from channel letters, decorative lighting inside furniture, soft drink vending machines to escalators.
          These are typical applications where light intensity and color rendering seem less important. With cove lighting however these are the two key factors to create the right ambient atmosphere.

          Cove light should be intense, and the color should be between 2400°K to 3000°K.? With cold cathode lighting a very intense light can be generated, completely even over the length of the tube(s).? Because the light is evenly generated on every part of the tube surface there won’t be any dark spots on the nearby ceiling so if the tubes were well tailored the ceiling will be illuminated evenly. Light that is not directly projected on the ceiling will be reflected by the cove which gives another possibility to add some impression of gold light by painting the inside of the cove in gold.

          With the actual state of development of led it is difficult to have evenly illuminated coves, as these are usually shallow and near the ceiling, in other words there is not enough distance to spread the light from the bright light spots into an evenly illuminated surface.? The light from leds is by definition directional light, generated in a tiny point, and any object that will be in between the light source and the wall will result in a dark shadow on the wall or ceiling.? Of course one can increase the number of led modules per meter, but this will not completely remedy dark spots. Also, in terms of energy, for a similar light intensity from cove lighting cold cathode outperforms led.

          Color temperature, especially in the 2400°K to 3000°K range is very difficult to achieve with leds. One should realize that for a given color temperature there can be various spots in the color triangle that correspond with that figure but these do not necessarily create the same feeling. This is much more under control with cold cathode lighting.

          Lastly, in terms of maintenance, more than 30 years of experience have proven that cove lighting with cold cathode can last many years with minimal maintenance. 10 years of 24/7 operation is rather common. With led only the future will tell us what the real life expectancy is. Though in this kind of application led is only used since about four years we can only notice the failures.
          Probably much of this is due to the higher ambient temperature in the cove, as warm air raises. Lack of cooling is detrimental to leds but does not affect cold cathode lighting.

          If cove lighting is the main light source in a room then it is necessary to have enough light, with the right color temperature and with little maintenance. At this moment cold cathode lighting can deliver that, rather than led.

          Source: Luc Steegmans
          Luc Steegmans is President of the European Sign Federation (ESF, www.eu-signs.org)and has been Chairman of the Technical Committee of ESF for several years. He is a certified electric engineer and owner of a sign company in Belgium(www.elbosigns.com), cooperating with international sign companies in global rebrandings, covering more than 75 countries worldwide. He is technical consultant to various organizations.

          Cold Cathode Lighting
           

          冷陰極管光源與日光燈光源及LED光源優缺點對比

          一、經濟
          若把飛利浦燈管換成美國EGL冷陰極管則每平米節約電量49W(145W - 96W = 49W),若一個交通銀行的大型燈箱面積為400平米,可以節省電量19.6KW,即19.6度電。
          以燈箱每日6小時計算,每日可節省電量117.6度,每年節省電量42924度。全年節省電費42926元。
          LED產品雖然運行功率小,但由于其光衰快,單價比日光燈和冷陰極管高,在整個壽命使用周期內,要達到同樣光效,其投入的費用并不比冷陰極管低。以廣州知名shopping mall萬菱匯為例,原本建筑師的計劃是在塔樓使用36×3W的大功率LED洗墻燈照明,但通過燈光設計師及各方商議和測驗,最終采用了進口混色冷極管燈具。既有不遜于LED豐富的色彩變化,又有冷極管特有的5萬小時長壽性和不懼高空戶外惡劣氣候條件的耐候性,同時,還有相對大功率防水LED洗墻燈更經濟的造價(相比原計劃LED洗墻燈,節省費用上百萬)。

          RGB Cold Cathode - One Link Walk  Plaza Guangzhou

          二、使用壽命
          美國EGL冷陰極管的使用壽命平均可達30000小時,最高可達50000小時,在整個使用壽命周期內光衰小。日光燈最高只能達到 50000小時。
          LED光源在推出初期號稱使用壽命可達100000小時,但實際上隨著現在LED開始廣泛用于室外和室內的照明之后,尤其是大功率的LED燈具,其功率大、發熱高、工作時間長,壽命問題就十分突出。 過去認為LED壽命一定就是10萬小時的神話在現實面前無情地破滅了。很多LED廠家和供應商給客戶的承諾通常是1~3年內失效, 可以100%無條件更換。10萬小時在業內人士心里心照不宣:其實僅僅是一個行業為了推廣產品的廣告需要而已,不能太當真。

           
          LED dots problem

          三、效果
          冷陰極管色彩艷麗,超過20種顏色、7種白色、且亮度高,穿透力強。冷陰極管具有良好的連續性和柔韌性,可制作成超薄型,從而滿足多種需要,這些是日光燈管很難達到的。LED產品尤其是大功率高亮LED產品在使用初期效果尚可,但隨著使用增加,其光效迅速衰減,以美國科瑞(CREE)為例,其產品在1000小時內光衰都達到了3%-5%,在光效衰減后,LED產品的顏色就會大大暗淡,極大的影響美觀和亮化效果。
          在這里尤為值得一提的是燈箱和標識的光源選擇。使用LED發光體生產的燈箱或標識的體積可以很小,但是由于燈箱本身是相對比較密封的空間,LED在里面散熱很慢,在工作一段時間后,溫度會急劇升高,這對LED的散熱是一個致命的打擊。同時,在戶外的環境下,我們還要考慮到防水的問題,LED發光體碰到水就相對容易壞,壽命會減短很多,效果也大打折扣。另外LED產品與冷陰極管的價格相比較并不便宜,因為只有用比同樣數量的霓虹或者冷陰極管更多的LED匯聚在一起時,才可以達到霓虹或者冷陰極管的亮度。所以當你準備做一個燈箱和標識項目時,要考慮到使用LED產品的價錢其實是很高的。冷陰極管或者霓虹是比較明智的選擇。

          四、維修
          冷陰極管電極無需加熱,可頻繁開關,不易損壞,維修率低。日光燈管屬于傳統的熱啟動光源,隨著每次一開一關,對兩端的電極燈頭有沖擊損壞,所以使用壽命只有冷陰極管的十分之一。而LED的工作原理決定了散熱對其質量的制約。以現在LED業界的領導品牌,美國科瑞(CREE)的產品為例,假如其產品結溫為105度,亮度降至70%,其LED壽命就只有一萬多小時。所以在大功率照明或者亮化領域,冷陰極管在質量穩定性、維修方面仍有其不可替代的優越性。

          Florescent Lamp problem
           

          五、配電設備
          通過圖例對比可看出冷陰極管配電箱功率小,設備少,體積小,費用低。
          ---------------------------------------------------------------------------------------------------------------

          冷陰極管實用于室內外裝飾照明,輸出功率小、省電、經濟,能做到舒適、優雅, 光暗對比效果鮮明,更可配合 特定電腦控制系統做出數百種顏色變化。冷陰極管,管長可達3米,更有效提高了冷陰極管與冷陰極管之間的連續性, 減少了暗點,以達到高亮度和美觀的效果,其發光明亮、柔和、不刺眼,穿透力強且分布均勻,在霧天其光彩依舊清晰可見。
          電極保護套及高壓線采用全硅膠材料,其絕緣性極佳,安全可靠。

          ※ 冷極管最長壽命50000小時
          ※ 能產生一般燈具不能達到的照明效果
          ※ 可用于高難度的輪廓投光照明工程項目
          ※ 冷陰極管系統光輸最高達1500流明
          ※ 冷陰極管能根據工程需要制成不同的長度和一定的形狀
          ※ 冷陰極管是制造燈光效果的最佳燈具,沒有閃動高熱和輻射性等危害
          ※ 冷陰極管能美化夜景,達到流光溢彩的現代都市景觀
          ※ 利用控制調光器極容易配合建筑調節光暗
          ※ 具有極微的距離在照亮之間沒有影子
          ※ 冷陰極管發出的燈光穿透力強且分布均勻
          ※ 可做超。ㄗ钚】蛇_8cm)燈箱的內打燈
          ※ 通過適當的顏色配合和設計能形成無數種燈光的顏色

          * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
          以上文章由比誠廣告材料有限公司(Best Supply Ltd.)提供,www.omniswipe.com, tel:021-50596271比誠廣告為一進口歐美燈光材料之供應商,主銷產品包括:意大利SIET高壓變壓器、EGL冷陰極管、意大利TECNOLUX冷極管及電子轉換器、德國HANSEN LED及電子轉換器。

           
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