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Focus LED Design on Driver Topology, Circuit Protection
12/19/2012

An isolated single-stage flyback driver (top) and a non-isolated buck driver. (Source: ON Semiconductor)
An isolated single-stage flyback driver (top) and a non-isolated buck driver.
(Source: ON Semiconductor)

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tekochip
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The downside
tekochip   12/19/2012 1:48:00 PM
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The dowside of using a fuse in a consumer application like this is that the fuse will never be replaced.  Once the fuse opens the product will not be repaired by the consumer and the device will end up in the garbage.  Yes, the fuse is reliable and inexpensive, but it really provides no protection for the rest of the circuitry because the entire device will be disposed of when the fuse opens.

Cabe Atwell
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Re: The downside
Cabe Atwell   12/20/2012 1:28:09 AM
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Tekochip,

Great observation. Do you really think the end-user will toss the board? Isn't the fuse easy to replace after all?

C

tekochip
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Re: The downside
tekochip   12/20/2012 7:34:51 AM
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For the average consumuer; the bulb in your bedroom lamp burns out, you throw it away and buy a new one.

g-whiz
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Gold
Re: The downside
g-whiz   12/20/2012 10:40:23 AM
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@Cabe

Most likely, the "fuse" will be a tiny, surface mounted device the size of a Tic-Tac and buried inside a non accessable cavity. Even if you could mange to get to the fuse, the replacement is only available by the 1000 piece reel from a mainstream electronics distributor.

TJ McDermott
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Temperature
TJ McDermott   12/20/2012 12:23:05 AM
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I think the assemblies are also susceptable to temperature swings - The traffic signals in North Charlston SC are LEDs, and most them have signifcant failures.  In some cases, more than 60 percent of the LEDs in a single color have failed.  Either that, or North Charleston got incredibly ripped off by whomever sold them the LED signals.

g-whiz
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Re: Temperature
g-whiz   12/20/2012 10:46:17 AM
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@TJ McDermott 

I have also seen what you have observed. In my experience, it is the LED driver that fails and not LEDs themselves. We've still got a long way to go in driver design.

Cabe Atwell
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Blogger
Re: Temperature
Cabe Atwell   12/20/2012 3:04:15 PM
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Yes, the board may go out, but the LED, not so. In this circuit, it looks like the fuse is before the rectifier. I would assume it to be large enough to remove or change. Every company that would deal with such a device should have someone adept enough to at least open a box.

Don't count people out so quickly.

C

g-whiz
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Led Drivers suffer from bigger problems
g-whiz   12/20/2012 10:26:18 AM
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   While safety and circuit protection are two important aspects in the overall design, todays mainstream LED drivers suffer from (IMHO) two BIG problems - low efficiency and bad location. Most of the drivers I've seen have horrible power factors and efficiencies in the 70% range. How in the world can we be promoting LED technology with its huge efficiency gains and think a 30% loss in power conversion is acceptable.

   Furthermore, Why do we continually "shoehorn" this inefficient converter into a tiny little oven heated by the LEDs. All because we insist on making this "new" technology appear like a 100 year old A19 light bulb.

   We need to get the electronics package out and away from the LEDs. It can then be larger, cheaper, operate cooler so it will last longer, and perhaps employ user replaceable circuit protection devices.

 

William K.
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Platinum
Re: Led Drivers suffer from bigger problems
William K.   12/21/2012 3:04:03 PM
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Please don't incriminate me with that all-inclusive "WE". Marketing types decide what will be on the shelves and they never ever listen to what I say. 

Of course there is a valid reason for putting LED emitters and supplies in a bulb-looking package, which is that until very recently those bulbs were the only show in town, and the luminairs that used them were what there was. So there exists a massive installed base of edison based light sockets, and that is where a whole lot of the replacements must fit. While change delivering an improvement is good, not everybody is ready to scrap all their present lighting and replace every bit of it with new LED systems. So the present obstacle is the current installed infrastructure, and that will not go away rapidly, no matter what congres legislates.

While it is not reasonable to manfdate a lower price, it certainly should be possible to mandate a minimum lifetime, and simply not allow products of inadequate quality to be sold for any price. OF course, determining that a product has an adequate lifetime would be a bit of a challenge, no question about that. But assuring adequate product life is the best way to gain acceptance.

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