DIY bench power supply with adjustable current limit 

Thanks :)

I have to agree with this man. I've learned so much more about SMPS technology and the behaviors of MOSFET circuitry through your videos. A classrooms curriculum would pale in comparison.

Dave from EEVblog has a great (5-part, I believe?) video about his battery-operated benchlab power supply. It provides enourmous amount of the knowledge of good quality. Now, Danyk shows his own take and I'm so happy to see his project in created his own style, which provides another portion of knowledge. Good job and thank you!

Fr tnx to Danky and all the others I found my passion. One more year at highschool and I'll go straight to collage for electrical engineering. I can't thank those guys enough for their wonderful explanations with schematics and measurements. ❤

@@marius9429 Good luck with your college in the future! :)

It's not easy to find something healthy these days...

@@DiodeGoneWild try to cut it with knife, then break it. But it is up to you, just wanted to warn you. :)

Ok, maybe a knife next time ;) or a hand saw, it doesn't produce such a fine dust. Or maybe sheet metal scissors.

Silica dust, not quite asbestos bad, but bad enough to avoid.

​@@DiodeGoneWild we don't want anything to happen to you , we need these videos to keep coming

It's also green because it's not built to end up in trash a year later ;)

Of course :) but I decided to use LM317 because it's ready made, simple and almost guaranteed to work well. In very small power supply, this makes sense. Bigger linear power supplies of course would use just a single power component, not two.

Or make positive side current sensor and make it pull the adj of 317 to -1.25.

One thing you get "for free" with most LM317s, is over-temperature protection. It's a nice "free" gift that would otherwise require designing and debugging some additional circuitry. Using an opamp will get you more precision on your output voltage, but using a 317 with overtemp protection will get you more safety overall. In a power supply, I'd rather go safer. (Most power supply rails are only supposed to be accurate to ~3% anyway.)

using them as switches, you run into trouble when they de-saturate.

@@liam3284 Yes, but if desaturation during switching happens, it's usually caused by a fault or by the gates getting too low voltage (usually caused by the whole circuit getting too low input voltage). If that happens, it means the rated "maximum power dissipation" of the transistors is often exceeded as well (and may lead to failure anyway). But, this fact that they may handle less if the voltage drop is large, can sometimes be of interest for a switching circuit as well. When for example evaluating the need for an "under voltage lockout". High power circuits pretty much always need it, since the power dissipation will easely reach destructive levels if the transistors go into linear mode. But if it's a low to medium power one, the transistors can sometimes be allowed to go into linear mode if the input voltage get too low - since the power dissipation will stay below damaging levels anyway. Which allow for a simpler circuit with less components. But it can be good to know some more margins may be needed, depending on how large voltage drop they may be subjected to during that condition.

You could do this with an potentiometer for the voltage where you have access to the shaft. Just 3d print an inner wheel, which has a thicker section that activates a micro switch, which switches to the higher voltage tap. This would not work for the current limiter dissipation

LMAO, I was about to give up trying to figure out wtf you were talking about. I promise you, no brown shirt sympathizer running this channel, just a coincidence.

Red color LED has a voltage drop of 1.8 (or ranges 1.7 to 2.2 ) volt

I think it mainly depends of output capacitor which slows down CC timing

There's always a high current pulse when you connect an LED to an already running bench power supply. The output capacitor discharges into the LED and also the current limit has a delay (the sensing circuitry, the power transistor...). The safe way is probably to connect the LED and then power the power supply, or to use some series resistor, despite the current is then limited by the psu.

Actually the safest way is to short out the output terminals, set the output current limit, connect the LED in parallel with the still shorted output terminals, then disconnect the short circuit.

LM317 datasheet shows couple ways of how to increase its current capability using an external transistor. At least some versions of the datasheet. But for more current, you might also have a double opamp and just one transistor, that both limits the current and regulates the voltage.

Very common trick, plenty of examples in linear regulator datasheets and around the web.

@@DiodeGoneWild thankyou sir for reply on my comment u made my day

Hell no, we've burnt all masks several months ago...