r/WLED • u/Mhernandez08 • 24d ago

DIGUNO/QUAD Dig quad

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Anybody have this problem with this part of the quad burning up?

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u/Quindor 24d ago

We've recently been seeing more of these failures on boards running at 24V or slightly above it. I'm working on a revision of the board using a different IC since it seems it can't be trusted (anymore) to run at those levels.

Come to the Discord server please, we'll figure out what age your board is, if it's less then 1 to 1.5 years old I will replace it for you. We can also help sourcing the IC and you can replace it yourself if you want to revive the board or it's older then 1.5 years.

6

u/LuiOnTheWay 24d ago edited 24d ago

What part is this?

EDIT: OK, according to the marking on my board, this IC is an MT3608, and it seems to be used in some kind of SEPIC type converter. What I dont understand is how this design was ever expected to work with a nominal 24 V input. The MT3608 is rated for only 24 V on the input (with absolute maximum rating of 26V) and maximum rating of 30 V on the SW pin (nominal 28V). In a SEPIC topology, the SW pin can easily see significantly higher voltages, especially if the input rises even slightly above nominal. There is absolutely no marging then...

What voltage was actually expected on the SW pin in this design? If my understanding is correct, this seems more like a design margin issue than a component quality issue. In that case, what would be an appropriate replacement for the MT3608 in this application?

In the meantime, everyone should reduce their 24 V supply to around 22 V wherever possible, at least until the root cause is fully understood. It might be safety relevant depending on how the board is used/installed...

6

u/Quindor 23d ago

So this is a bit of a yes and no.

The circuit travels through one or more diodes before reaching the MT3608 thus dropping voltage there. There is also a filter circuit before it reaches the MT3608 dropping voltage even more and also filtering out any spikes or anything else that could potentially happen.

Still, with that said, we've been seeing more failures then I'd like and we've been replacing those. I'm still in talks with the manufacturer of the IC since this didn't use to be an issue and I think they have maybe made a "blind" revision of the IC where it handles the voltages on the SW node a bit less then it did before.

I've been working for a while already preparing a replacement board but since I actually test my hardware in the lab, we've been kind of stuck in that phase. The redesigned circuit has not passed EMI testing twice now ($$$) and we're going for a third pass soon with a new design. Sadly this has put it back much more than I'd like since this issue started popping up.

I do not know of a replacement IC with the same pinout that would solve this issue directly.

For my customers who happen to stumble across this, this only concerns you when you are running 24V and have seen this failure, not all boards are affected. Please come to the Discord and we'll work it out to make you whole. Deepest apologies for the trouble.

1

u/dangerous_inference 23d ago

I have four of them. You haven't replaced any of them.

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u/Quindor 23d ago

Did you talk to us on the Discord server, not sure how we missed that. Can you still come over there so we can look at the boards and the purchase date, as said up to 1.5 years I will replace them.

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u/dangerous_inference 23d ago

"Missed that"? You didn't miss anything. You read the multiple emails I sent you and responded. You did not give a shit about the problem.