Automatic DCDC-converter efficiency tester project

[mattselectronics]

Hi,

I created this automatic DCDC-converter efficiency tester project.
https://youtu.be/ZX7pkNB275M

If you are interested in the modules, I tested so far, you can find the test reports here:
https://www.matts-electronics.com/dcdc-converters/

What do you think of it?
What could be improved?

[fki82]

Thank you for the Dataseets!
They are very useful!

[sleemanj]

Nice, I keep meaning to make something similar to do the same job, except I have this stupid idea to also try and make a mini stepper motor connect to the typical trimmer potentiometer(s) in order to also automatically step through output voltages.

I would make a couple suggestions, you should log the temperature of the board, and the ambient, you could simply do this using a couple of NTC bead thermistors, I have either used kapton or superglue to attach thermistors to what looks like it would be the hottest point (usually on the switching IC).   I often find that thermal capacity is the limiting factor long before advertised current capacity is reached.  You do need to allow the temperature to stabilise at each change though often these converters can do a minute or two at some current before starting to suffer thermally.

The temperature rise can then be plotted against output current this can give you a quick visual to "safe operating area" in terms of thermal capacity.  A single plot of temperature against power-loss (in W - Out W) can also be helpful to get a quick idea if somebody is going to use an in/out voltage combination you didn't test (ie they can say "well, assuming a worst case typical efficiency the loss will be x Watts so temperature rise would be about x degrees").

[mattselectronics]

Most of the potis on the cheap converters are pretty horrible. Maybe replacing it with a digital Potentiometer would be easier.

Yes, thermals are a big and complicated matter with such converters.
I didn't take that into account, because it is very complicated to test properly and takes forever, because I would have to wait until the temperature equalized on every step.

Also the mounting affects thermals a lot.
In a closed case it is going to be worse than out in the open.
Thermally connecting the PCB to some kind of heatsink will improve it a lot.
Even the orientation of the module would make a difference because of thermal convection.
If active airflow is added, everything is different again....

Most of the PCBs don't seem to be designed for optimal thermal performance anyway. Some even don't have thermal vias....

[capt bullshot]

Sorry for this shameless self-advert, but I couldn't resist:
Some time ago, I've made a proof of concept to measure DC/DC converter effiency using a modern Lab Power supply as the only instrument:
http://wunderkis.de/E36312A/index.html

Anyway, your approach is a pretty valid approach, I often thought about creating something similar, but I'm too lazy, so my approach didn't get over the "proof of concept" stage.

[mattselectronics]

Cool idea!
how did you measure the current?
Or did you calculate it using the resistor value?

[capt bullshot]

Or did you calculate it using the resistor value?

The current is calculated as the difference from the current through the resistor (this is supposed to be constant) and the Lab PS output current (the larger the Lab PS output current, the lower the real DUT output current is).