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Teardown: LED light shrinks size, cost with non-isolated driver

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Jack.L
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re: Teardown: LED light shrinks size, cost with non-isolated driver
Jack.L   3/4/2013 2:25:50 AM
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The two picture of an old design and a new design DO NOT represent generational changes, simply different design choices. I have a driver extracted from a LED lamp (non-isolated) that is 18-24 month old that is simpler in design than either of the examples shown. It is not the greatest design in terms of efficiency, but it works ..... other than the Rudycon ... yes Rudycon capacitor. It even passed UL, though I have a hard time believing it passed any conducted emissions tests.

Jack.L
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re: Teardown: LED light shrinks size, cost with non-isolated driver
Jack.L   3/4/2013 2:09:26 AM
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Keep in mind that radiated power is a function of the temperature of what is radiated. Heat sinks are relatively cool so they do not radiate much heat and much rely on convection (and some radiation). A bulb radiates most of its energy into the environment. To dleske below, actually we are up to 30-40% in some cases for modern LEDs in terms of percentage of power that is light, though high CRI, low color temp bulbs are generally lower today. As the LED efficiency goes up, power supply requirements go down linearly, but heat sink requirements drop quicker as less and less power is generated as heat.

Jack.L
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re: Teardown: LED light shrinks size, cost with non-isolated driver
Jack.L   3/4/2013 2:05:41 AM
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The LEDs are good for 50,000 hours or more. However, bulbs have force a smaller than ideal heat sink and limited ability to isolate the power supply from the heat sink. I don't think you mean plasma emitting diodes, but plasma light sources. They are still going strong somewhat, but there are few companies working on it. As LED costs come down and efficiencies go up, their market space keeps getting smaller.

Jack.L
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re: Teardown: LED light shrinks size, cost with non-isolated driver
Jack.L   3/4/2013 2:03:38 AM
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I have evaluated several LED bulbs and have found the temperature in the power supply to vary between about 65C and 90C across a range of designs in a typical installation environment. If you are using 2000 hour 85C caps then you are going to have issues in all of those bulbs depending on how tight the required tolerance is of the power supply. On the other hand, if you have 5000 hours 105C capacitors, most of the designs will see lifetimes that match the product claims.

l8mackey11
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re: Teardown: LED light shrinks size, cost with non-isolated driver
l8mackey11   3/1/2013 3:25:14 AM
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I thought one of the nice attributes of the LEDs was long life (like on the order of 50,000 hours) if the heat management is designed right? Anyone hear about the Plasma Emitting Diodes. Saw an article about them awhile back but not much since then.

Dave1010101
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re: Teardown: LED light shrinks size, cost with non-isolated driver
Dave1010101   3/1/2013 2:34:53 AM
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I think the caps will not be that hot but eliminating them--or making them smaller--is probably a design project somewhere. I know that there was much work done in multi-phase power converters to power very high current (but low voltage) with fast voltage adjustment. Perhaps more IC integration will simplify the overall architecture and make the system more reliable and easier to manufacture.

PCB_Tom
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re: Teardown: LED light shrinks size, cost with non-isolated driver
PCB_Tom   2/28/2013 9:41:05 PM
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Yep, those electrolytics will almost certainly be the weak link that fails in these.

Etmax
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re: Teardown: LED light shrinks size, cost with non-isolated driver
Etmax   2/27/2013 4:10:41 AM
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Interesting, 2 electrolytic capacitors. From memory the life span at 100degC is 2000 to 5000 hours for the good ones. I think this needs to be re-thought.

DrQuine
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re: Teardown: LED light shrinks size, cost with non-isolated driver
DrQuine   2/27/2013 3:11:26 AM
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This bulb having the same form factor as a traditional light bulb is a great benefit. I do hope that they prove as reliable as promised. While the LEDs may have a long life, most of the package is other components. I know that I've returned at least 10% of my 7 year guaranteed compact fluorescent lamps (CFLs) because of failures within 2 years. The CFLs also suffered from slow start-up (anything over "60 watt" replacement could take a minute or more to become bright despite their packaging claims to the contrary). Dimmers and remote controlled outlets, of course, were non-starters.

anne-francoise.pele
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re: Teardown: LED light shrinks size, cost with non-isolated driver
anne-francoise.pele   2/26/2013 2:39:45 PM
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FYI, this has been fixed... Thanks for your interest. Anne-Francoise Pelé

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