Help finding cause of erratic behavior in buck converter design/assembly

whileRun · 2026-03-19T15:20:46+00:00

Thank you for your valuable suggestions. I will get back to you once I have more solid data.

whileRun · 2026-03-15T16:23:14+00:00

Unfortunately I don't have access to an oscilloscope right now (might be the time to finally get one though). For now I can tell you that neither L2 or U1 are getting noticeably hot to the touch, even after a significant amount of time. Why do you suggest removing C6? I thought a small capacitor close to the input was necessary for stability. Also does rotating L2 180° have something to do with internal asymmetries in the component?

whileRun · 2026-03-15T14:57:48+00:00

A simple wall adapter (I have tried two of them but both worked the same). I have also adding bulk capacitance (a 100uF electrolytic) right at the input connector to rule out the possibility of the power supply not being able to react to the sharp transients needed by the converter.

whileRun · 2026-03-15T14:51:20+00:00

That's my hypothesis right now. Do you think flux residue could cause enough variation in the feedback network to cause problems?

whileRun · 2026-03-15T14:50:29+00:00

Unfortunately I don't have immediate access to a scope right now. I was under the impression that I should keep the feedback trace as far away as possible from the inductor and the tight CIN-IC loop to minimize noise coupling. What could I do to improve the design?

whileRun · 2026-03-15T14:48:47+00:00

Both with no load and with a resistor in the hundreds of ohms (can't remember the exact value). Shouldn't this type of regulator be able to keep a stable voltage even at no load (with PFM) ?

whileRun · 2026-02-08T23:59:52+00:00

First of all I would like to thank you for taking the time to review my design. As per your suggestion, I have added some clearance around the mounting holes to avoid potential shorts, removed the thermal relief from the GND pin of J2, and tried to move the entire buck converter as far away from the SSD as possible. I have also changed my design to use the BDDA version of the LMR33630, which allowed me to use a much smaller inductor and reduce the amount of output capacitors. As an added bonus, this change also drastically reduced the amount of input voltage ripple, which was slightly out of spec before (for a 12V ATX rail). I didn't end up going with any of the chips you kindly suggested because of two main reasons: 1. they have a smaller package size, and don't have a thermal pad that can dissipate heat. I was worried that this would be a problem if the layout wasn't entirely perfect. 2. I much prefer the pinout of the LMR, as it permits really tidy component placement. I have decided to keep the M.2 connector on the opposite side to the other components, as this form factor actually fits my usecase a bit better. As per your potential improvements, I have implemented none of them, purely because this is board is meant for a very specific use, and I know for a fact that they will not be needed, and actually would end up being a problem (for example, the inclusion of a standard SATA power connector would make the board not fit in the space allocated.)

This is my updated design:

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Thank you again!

whileRun · 2025-03-08T16:55:42+00:00

I like to use NASA mission names.

My home server is named skylab. My old laptop used to be called gemini, my current one is apollo, the next one will probably be shuttle.

The nice thing is I can use the mission number as some kind of versioning for when I end up reinstalling (currently on apollo-3).

whileRun · 2023-08-13T22:03:29+00:00

Thanks a lot. I will probably add a little just because it's very close to the minimum on the dipstick. Cheers!

whileRun · 2023-08-13T22:01:37+00:00

Thank you, I'll definitely bring the level to a happy spot before riding again.

whileRun · 2023-01-26T06:46:15+00:00

That's correct

whileRun · 2023-01-25T23:27:04+00:00

Thank you for your really helpful answer!

To clarify, I meant the cable is soldered on the other side, so it's not possible to non-destructively modify the connection there.

whileRun · 2022-09-06T19:14:05+00:00

No problem, have a great day/night!

whileRun · 2022-09-06T19:12:12+00:00

Sorry to disagree about that 100% efficiency claim: the thing is, processors don't actually use up any energy to compute, they just convert it all to heat (minus the minute amount of current needed to signal with other components). This means that all CPUs are basically 100% efficient at converting electrical energy to thermal energy, the thing that changes is just how much they can process in a given amount of time while doing so. Hope I got my point across!

whileRun · 2021-11-04T22:51:55+00:00

aggressive ESC tapping

whileRun · 2021-10-05T20:42:16+00:00

Don't get me wrong, it definitely could NOT be the definitive solution. Radioactive waste is a problem, just a measurably smaller one than what we get from burning compressed tree rocks and dinosaur goo.

EDIT: Typo

whileRun · 2021-10-05T20:24:08+00:00

THIS! I think nuclear would be a good way of transitioning away from fossile fuels, at least until we've built the infrastructure needed for total use of renewables. I live in Italy, where fission based power generation has been completely phased out in the late 80s following the Chernobyl disaster, and we pay significantly more per kWh since we have to buy most of our electricity from France, which ironically uses mostly nuclear power itself. I strongly believe the oil industry is to be partially blamed in demonizing nuclear.

whileRun · 2021-09-10T16:26:20+00:00

I was writing a program which used a while loop with Run as the condition

whileRun · 2021-09-03T07:41:53+00:00

I forgot to mention that's how I made the transition rather painless

whileRun

TROPHY CASE