LED light manufacturers are often claiming 50,000 hours or more for lighting lifetime. Unfortunately many times those lifetime expectations are not met. Usually the makers of those high those lifetime promises forget to include the lifetime and reliability of all components, and the real-world thermal conditions the LEDs are subjected too.
Just a few years ago, LEDs operated at such low power that they didn’t need any special cooling. But as LEDs have grown brighter and more powerful, thermal management has rapidly becoming a necessity. Designers need to understand that accurate thermal modeling as well as component selection will ensure their lighting designs meet their reliability and lifetime numbers.
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Tomi Engdahl says:
Lifetime of An LED
http://www.eeweb.com/company-blog/fairchild_semiconductor/lifetime-of-an-led/
Researching the different LED vendors and their datasheets, the common theme is proper heat sink and thermal management of silicon junction temperature extends the lifetime of the LEDs. Look for lifetime versus junction temperature graphs in LED vendor datasheets that accounts for lumens depreciation.
For example, L70 notation means that light output is 30 percent less than initial output. It is the percentage decrease that a “typical” eye starts to detect a decrease in light output.
Thermal management of LEDs is half the effort to ensure the advertised lifetime. The LED power supply or driver design is the other factor for lifetime. When the LED does not work, the end user does not care if it is caused by LED’s lumens depreciation or the LED power supply that failed.
Because LEDs are non-linear (varying forward voltage versus forward current) devices, a constant current LED driver or power supply is required.
Tomi Engdahl says:
LED lamps promises a lot, such as a long service life and large savings in electricity bills. Finnish manufacturer ledivaloputkien Valtavalo by cheap supermarket lamps is not wise to rely on.
- Consumer-oriented cheap LED lamps are often certainly not fulfill the promised lifespan. This is due to the fact that they use poor quality parts poorly assembled, says Valtavalo Markku Laatikainen.
The market is pushed all the time ledikomponentteja still at a lower price. A large part of these come from Asian, especially Chinese factories. – The range of prices in the world leditarjonnassa is in a word, huge. At the same intended use of the cheapest and most expensive component of the price difference between vo be many times higher.
- Typically, the electronics saves often these components, which shortens the life of the product significantly. In fact, ledikomponentit sustainable today often at least for long enough, but enimäkseen driving current is transformed into heat, the mechanical design and the power supply electrolytic capacitors determine the actual service life of LED lamps, Laatikainen image.
Source: http://www.etn.fi/index.php?option=com_content&view=article&id=2322:valtavalo-halpa-ledilamppu-ei-kesta&catid=13&Itemid=101
Tomi Engdahl says:
Jättitutkimus: joka toinen ledilamppu loistaa yli 10 000 tuntia
https://etn.fi/index.php?option=com_content&view=article&id=11207&via=n&datum=2020-09-28_15:38:00&mottagare=31202
Ledilampuille luvataan 15 tai 30 tuhannen tunnin käyttöikää, mutta täyttävätkö ne lupaukset? Ruotsin energiaviranomaisen laajassa testissä kävi ilmi, että puolet testatuista lampuista paloi 10 000 tuntia.
Energimyndighetenillä on oma testauslaboratorio, jossa ledilamppuja on testattu. Testatut lamput ostettiin jo vuonna 2014 eri EU-maista. Niistä mitattiin valovoimaa ja kykyä säilyttää ilmoitettu värilämpötila.
Testissä kriteeriksi määritettiin 70 prosenttia alkuperäisestä valovoimasta. Kun lampun kirkkaus alitti tämän lukeman, se katsotaan ”palaneeksi”.
Silfveniuksen mukaan laadukas ledivalo säilyttää valovoimansa ja värilämpötilansa. – Vuoden 2014 jälkeen markkinoille on tullut aljon uusia lamppuja. Ne ovat elektroniikaltaan parempia ja edullisempia, hän kertoo.
Syyskuussa 2021 ledilamppujen suunnitteluvaatimukset tiukkenevat. Niiden energiatehokkuutta mitataan uudella tavalla ja kriteerit läpäisseille myönnetään uusi energiamerkki.
Uudessa testissä lamput kytketään päälle kahdeksi tunniksi ja en jälkeen niiden annetaan jäähtyä puolen tunnin ajan ennen uudelleenkytkemistä. Testin tekeminen vie viisi kuukautta aikaa eli lamput palavat 3600 tuntia. Valmistajan lampuista vain yksi kymmenestä saa testin aikana pettää.
Tomi Engdahl says:
Testing solid-state lighting reliability
https://www.edn.com/testing-solid-state-lighting-reliability/
The U.S. Department of Energy (DOE) has recently released test results and conclusions from its ongoing reliability testing conducted on solid-state lighting (SSL) drivers, LED packages, and OLEDs.
SSL drivers
SSL drivers have long been considered the “weakest link” in a lighting system. In response to this, DOE initiated a long-term LED driver assessment in 2017 that included evaluation of both single- and multi-channel LED drivers
he test results indicated that degradation (vs. complete failure) of the capacitors and inductors in the electromagnetic interference (EMI) filter in stage 1 of the driver circuitry can lead to further failures throughout the driver as a whole. Components in the stage 1 circuitry are exposed to higher voltage levels, making them more susceptible to aging. Further, degradation of stage 2 components appears to lead to observable changes in light flicker.
LED packages
Luminous flux maintenance and chromaticity shift are the two most important parameters in assessing long-term LED package performance. The standards that govern the methodology for projecting these parameters are published by the Illuminating Engineering Society (IES). IES LM-80-15, IES Approved Method: Measuring Luminous Flux and Color Maintenance of LED Packages, Arrays and Modules, first published in 2008, provides the methodology for setup and data collection of luminous flux and chromaticity data. IES TM-21-19, Technical Memorandum: Projecting Long-Term Lumen, Photon, and Radiant Flux Maintenance of LED Light Sources, first published in 2011, provides a mathematical method for extrapolation of collected data to arrive at a luminous flux maintenance projection. The methodologies specified in these standards have been used in the DOE evaluation program since its inception in 2012.LED packages
Luminous flux maintenance and chromaticity shift are the two most important parameters in assessing long-term LED package performance. The standards that govern the methodology for projecting these parameters are published by the Illuminating Engineering Society (IES). IES LM-80-15, IES Approved Method: Measuring Luminous Flux and Color Maintenance of LED Packages, Arrays and Modules, first published in 2008, provides the methodology for setup and data collection of luminous flux and chromaticity data. IES TM-21-19, Technical Memorandum: Projecting Long-Term Lumen, Photon, and Radiant Flux Maintenance of LED Light Sources, first published in 2011, provides a mathematical method for extrapolation of collected data to arrive at a luminous flux maintenance projection. The methodologies specified in these standards have been used in the DOE evaluation program since its inception in 2012.
LED package data collected from 2012 to 2015 indicated that both ceramic and chip-on-board (COB) packages provided the best luminous flux maintenance, and that polymer packages performed worse, on average.
Results thus far have demonstrated a significant improvement in OLED panel luminous flux maintenance. Long-term performance of warm-white OLED panels is typically lower than higher-color-temperature panels and also typically decreases as operating temperature increases. In addition, the chromaticity maintenance of OLED products appears to have improved over the past five years, with warm-white panels exhibiting better chromaticity maintenance than neutral-white.
Tomi Engdahl says:
What’s the #storage life of idled #LED light bulbs? #LivingAnalog #capacitors
What’s the storage life of idled LED light bulbs?
https://www.edn.com/whats-the-storage-life-of-idled-led-light-bulbs/?utm_content=buffer0d5a1&utm_medium=social&utm_source=edn_facebook&utm_campaign=buffer
Previously, we discussed for how long a time an electrolytic capacitor can safely be left idled. Hold that thought.
The bulb held an impressive set of electronic goodies. Aside from 32 LEDs on that circular disk, there was a circuit board that turned out to be a constant-current switch-mode driver.
The first thing I learned was that these things should be e-cycled when they go bad, even though our local e-cycling service does not include these items. The second thing I learned was that there was/is an aluminum electrolytic capacitor in there. That led (no pun intended) to a new realization.
However, the storage life of an idled LED light bulb such as the one I took apart will be constrained by the storage life of that aluminum electrolytic capacitor. These things can’t just be put on a shelf somewhere and then forgotten about for years and years the way a conventional incandescent light bulb can be safely put away.
If my collection of reserve light bulbs included any LED light bulbs like the one I just dissected, there could be a substantial risk of trouble from electrolytic capacitor degradation. My advice would be to put any new LED light bulbs into service fairly soon after purchase. I would even advocate that LED light bulbs should only be sold with a “use by” date on their packaging.
As to why my particular device went dark, I never did figure that out. Nothing appeared to be burned or charred. Unfortunately, the circuitry itself was only partly discoverable because the PWM chip bore no markings.