Author Topic: Bad LED Drivers  (Read 5661 times)
flyoffacliff
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Bad LED Drivers « on: February 17, 2015, 03:30:52 PM » Author: flyoffacliff
I have been seeing a lot of LEDs going bad. They often start flickering rapidly and sporadically. I have a strip of 18 LEDs and 3 on the end started flickering, ruining the whole strip. Seems like it often happens in sets of 3. This strip had less than 3,000 hours of operation. They are supposed to dim slowly over 25,000+ hours. I have even seen it with streetlights around town. They disconnected them because they were distracting drivers more than helping.

What on earth is so hard about making quality LED drivers? There is no arc to strike, all they have to do is pass a steady current through the diodes.

Since these LED drivers are so unreliable, why don't the fixtures make them replacable? Are there any that are?

Also, what is the difference between a driver and a ballest? Besides LEDs using drivers, and florescent using ballests?

Thank you
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Re: Bad LED Drivers « Reply #1 on: February 17, 2015, 08:57:11 PM » Author: nicksfans
Many LED streetlights do have replaceable drivers. The terms "driver" and "ballast" pretty much mean the same thing; both regulate current to a light source. Nothing really wrong with calling it an "LED ballast" or "fluorescent driver" except that it breaks convention.
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flyoffacliff
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Re: Bad LED Drivers « Reply #2 on: February 17, 2015, 09:08:03 PM » Author: flyoffacliff
Many LED streetlights do have replaceable drivers. The terms "driver" and "ballast" pretty much mean the same thing; both regulate current to a light source. Nothing really wrong with calling it an "LED ballast" or "fluorescent driver" except that it breaks convention.

Thank you. Have you had flickering or reliability problems with the drivers?
What is so hard about making quality LED drivers? There is no arc to strike, all they have to do is pass a steady current through the diodes.
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Re: Bad LED Drivers « Reply #3 on: February 17, 2015, 09:14:43 PM » Author: nicksfans
I doubt it's hard to make a good LED driver, just more expensive than manufacturers would like right now. There's a lot of pressure for cheap LEDs and the manufacturers need to turn a profit. This isn't fact, just speculation on my part.

I've seen LEDs dimmed out, flashing, and whatnot out and about, but I've had good luck with them at home. Granted, I don't have too many, and the ones I do have, I haven't had long, but I'm not afraid to buy more. I definitely think they'll take over most lighting before too long.
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Re: Bad LED Drivers « Reply #4 on: February 17, 2015, 09:26:05 PM » Author: flyoffacliff
I doubt it's hard to make a good LED driver, just more expensive than manufacturers would like right now. There's a lot of pressure for cheap LEDs and the manufacturers need to turn a profit. This isn't fact, just speculation on my part.

I've seen LEDs dimmed out, flashing, and whatnot out and about, but I've had good luck with them at home. Granted, I don't have too many, and the ones I do have, I haven't had long, but I'm not afraid to buy more. I definitely think they'll take over most lighting before too long.

I agree some lamps are much better than others. I bought 5 LED Philips bi-pin lamps, 2 suddenly died suddenly within a few weeks, and 1 sometimes flickers. And the light I mentioned in the OP. All my other LEDs have been fine. I agree they are the future, but there is a lot of junk on the market now.
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Re: Bad LED Drivers « Reply #5 on: February 17, 2015, 09:59:55 PM » Author: nicksfans
When I was in Texas around New Year's, I saw a number of LED streetlights with some of the LEDs out and I even saw some LED parking lot lights at a car dealership flashing wildly. Haven't seen the same thing here in SC because we just started getting LED streetlights, but I have seen some LED landscape lights and LED fluorescent retrofit tubes that have failed. Lemme tell you, the LED retro tubes are pure, unadulterated crap.
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Re: Bad LED Drivers « Reply #6 on: February 17, 2015, 11:59:04 PM » Author: BlueHalide
The municipality here brought in some LED cobraheads to test that use a single 100w chip, these replaced 250w HPS cobraheads, the 20 or so fixtures lasted about 4 months. All seemed to suffer terrible rapid lumen depreciation and became dim to the point of being useless. The HPS cobraheads are back up and I couldnt be happier, you just cant beat magnetic HID in reliability
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Re: Bad LED Drivers « Reply #7 on: February 18, 2015, 01:19:40 AM » Author: Medved
Just 3 flickering out of large group does not sound like bad ballast, I would rather say one of the LED itself has an open circuit problem (usually bond wire welds on the die get loose, could be due to overheating; high temperature accelerates this type of defects).

The LED life is rather problematic: If you want to prevent the 100/120Hz flicker (many people here are so mad of... :-) ), you have touse an electrolytic capacitor. But once you use an electrolytic capacitor, you have a componentto fail very soon. The problem with higher power lighting is, you have to dissipate a lot of heat. For that you need either a lot of space and large heatsink outside of the fixture (does not look that appealing when OFF), forced air cooling (terrible lifetime of that fan - so practically not usable in general lighting) or operate at higher temperatures (compare to most of the older electronic).
So practically justthe latest approach is the only one usable at this time, but that impose problems the older long life electronic was never faced to: High temperature operation (actually the low operating temperature was assumed as a minimum must when a life longer than few 1000h was needed).
That means many components become not usable anymore, among them the electrolytic and many film capacitors, any package without either being very small or having strain relieve (so using a DFN or QFN for an IC package on a LED board just can not have different result than it had). But that is often very difficult to explain to many electronic design engineers (IC makers know that, but their customers just foolishly insist on such packages, so at the end the IC makers offer them), when they see such things in their smart phones...
And that means some features are just not possible, when you want reliable light (e.g. being flicker free; although electrolytic capacitor maker's marketing tries to tell otherwise, well just until ask for a 100khour life guarantee)
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marcopete87
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Re: Bad LED Drivers « Reply #8 on: February 18, 2015, 06:17:21 PM » Author: marcopete87
I have been seeing a lot of LEDs going bad. They often start flickering rapidly and sporadically. I have a strip of 18 LEDs and 3 on the end started flickering, ruining the whole strip. Seems like it often happens in sets of 3. This strip had less than 3,000 hours of operation. They are supposed to dim slowly over 25,000+ hours. I have even seen it with streetlights around town. They disconnected them because they were distracting drivers more than helping.

What on earth is so hard about making quality LED drivers? There is no arc to strike, all they have to do is pass a steady current through the diodes.

Since these LED drivers are so unreliable, why don't the fixtures make them replacable? Are there any that are?

Also, what is the difference between a driver and a ballest? Besides LEDs using drivers, and florescent using ballests?

Thank you

this strip is an 12v resistor included led strip, which every 3 leds there is an resistor, so your ballast is an common 12v power supply (constant voltage DC).
I think your problems are caused by bad quality leds and, as said Medved, thermal issues.
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Re: Bad LED Drivers « Reply #9 on: February 19, 2015, 12:49:59 AM » Author: tolivac
The LED drivers in the American Lighting LED yard lights installed at the tranmsitter site are replaceable along with the LED lamp panels.The LED drivers come in what looks like an "F" can flourescent ballast can.The primary voltage is 100V-277V.Since these have just been installed-running a month-so far so good.
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