My first buck converter

[cavac]

I just finished designing and building my first buck converter.

The main design goal was reliability under harsh conditions, since it's used to power outdoor barebones Arduino projects from a solar power installation. The problem with staddard Arduinos isn't only the power usage, but (in my case) the rather crappy on board voltage regulators. I always need an external regulator anyway (battery voltage can go as high as 15V), and in most cases i need a second regulator to provide a decent amount of stable 3.3V. So i decided to do my own.

It's not the most efficient design (around 75-77%) and it uses a lot of power without any load connected (around 12 milliamps). The components will never see more than a few percent of their design load, all pins&pads have a fairly good spacing and with a bit of conformal coating this should (in theory) last a decade or more.

I have yet to fully qualify the design. Testing under various load conditions and checking the ripple current and such.

The design will later incorporated into my own "Radioduino", a barebones Arduino with nRF24 and RS485 on a single board.

The KiCAD files are Open Source as part of my "Garden Space Program".

https://cavac.at/public/mercurial/gardenspaceagency/file/tip/SystemControlBoards/powersupply

Sorry for the crappy photos, i had to use my phone (DSLR is currently lent out to a friend)

[cavac]

And the stats are in! To say i'm quite pleased is a gross understatement. This is my first ever buck converter, my first time using inductors and my first time using KiCAD.

Voltages are within 50-60mV of design for 0-200 milliamps current (my most common use case). Ripple is about 20mV at 100mA load. Ripple frequency is about 200-300kHz under my use case.

This is all similar or better to the cheap chinesy ready-to-use modules i used before. The output voltages are really spot on for what i need.

The module is a bit on the expensive side with about 16 Euros each. But the PCB (from Aisler) is super sturdy and it's dead easy to solder and test a complete module in under 5 minutes.

When i started this project, i thought it's a bit a waste of time and money, but unless i find some flaws down the line, this buck converter design will probably become my go-to standard for many future projects.

[Zero999]

Please post a PNG/PDF of the schematic here, as an attachment. Not everyone has KiCad installed.

[cavac]

Ooops, sorry.

Here's the schematic

[Dmeads]

Thats awesome!! Keep it up!

[temperance]

There is HF decoupling missing in your circuit. You will need some ceramic capacitors at the input and output. 100nF will do fine.

Also, the aluminium capacitors must be low ESR types.

[gnuarm]

Those European capacitors look a bit sketchy.  You might want to use reliable US made capacitors.

-|(-