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40V-30A Adjustable Switching Power Supply


A DC-to-DC converter is one of the most commonly used circuit topologies in electronics, especially in power supply applications. There are three main types of DC-to-DC converters (non-isolated): Buck, Boost, and Buck-Boost. Sometimes a buck converter is also called a step-down converter and a boost converter is also called a step-up converter. A buck converter reduces/steps down the input voltage while increasing the output current.
In this article/video, I introduced an adjustable buck converter circuit that can deliver up to 30A and handle up to 40V at the input. The output voltage is adjustable from 3V to 37.5V. Several PCB design rules were followed to enhance output stabilization and current handling, also to reduce the radiated emission, and noise figure.
To design the schematic and PCB, I used Altium Designer 22 and the electronic search engine (octopart) to easily and quickly collect information about the necessary components. To get high-quality fabricated boards, I sent the Gerber files to PCBWay and finally tested the current handling, output stability, and noise figure using the Siglent SDL1020X-E DC load, Siglent SDM3045X multimeter, and Siglent SDS2102X Plus oscilloscope. Just build one and have fun!

Impressive how low the ripple is at that current. Congratulations for a good design.

I myself would be interested in creating a smaller buck converter design (lower current, smaller PCB). I might take a look at your design. I'm not experienced with switching power supplies, but you have to start somewhere.

Did you do any EMI measurements?

The cheap SMPS that you can buy online are famously noisy. One such SMPS was analyzed and improved by Elvee on the diyaudio forum (linking it here, because I thought the methods whereby he reduced EMI might be interesting):

I happen to have that same SMPS and did the same mods. I'm thinking some of the methods might work on a buck converter as well, e.g. grounding ferrite cores, grounding the heat sink, adding a ferrite bead on the output diode leg. But this is for sure things that would have to measured case by case.

(To ground the transformer ferrite core, I scratched a small area on one side, glued a small wire to the side of the transformer with super glue and applied conductive paint on the scratched up area to make a connection with the bare wire in the same spot. This made a reliable connection that shows as a stable resistance reading when measured also elsewhere on the ferrite core).

Thank you.
I don't have a spectrum analyzer, so no EMI measurement, however, I expect to be okay, although you always have to put switching supplies inside a metal enclosure.


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