EEVblog #222 - Lab Power Supply Design - Part 2

Part 2 of Dave's Open Hardware constant current linear regulated lab power supply design. An in-depth look at the LT3080 datasheet, the LM334 current source, and a few more circuit tweaks before it's ready to build in the next episode to see if it works!

[DocLow]

This series of videos has taught me more than many university classes.

[sujatnalokananta]

this is an advance tutorial for electronic engineer. the best electronic engineering tutorial I ever seen... increadible

[dedamarsovac]

I love it how the baby cries at 10:46
Really, the sound quality is so good that it made me think something is happening here in the middle of the night.

[EEVblog]

@TheMcMonster I don't know, maybe. There is a specific reason why I'm building this "simple" design, and you'll see why in the future (not the next video though). And AFAIK there aren't that many PSU circuits out there that show you how to control traditional voltage and current regs simply from a micro with PWM, hence this design.

[EEVblog]

@Kankki1 Good question, and one for the IC process engineers out there.

[GeorgeGraves]

I'm afraid of datasheeets. So I had to force myself to watch this. I'm really glad I did. Thanks for taking the time to walk us through the data sheet. I fell like I learned a lot just from that!

[mgeo]

I love the phrase "fairly jelly-bean low end precision opamp"...

[EEVblog]

@TheCrazyInventor Yep, there will eventually be a PCB for it.

[EEVblog]

@spelunkerd Yes, Part 3 will be testing the circuit on the breadboard to see how it performs. The real build will come later, I have an idea in mind, and will do another Part 4 when that is complete (that will take some time).

[hlab]

I think I'm gonna build one myself as I watch the next one. Thanks Dave.

[EEVblog]

@PetrFM The LM317 neg supply would actually make it more complicated. Not only the 7660, but the output divider will have a varying current based on output voltage, and that throws out your current sensing at low values. The LT3080 and LM334 is simpler IMO.

[MikePoirier]

I like it. I'm learning a lot.
It's fun and useful to take time to design.
More of these type of show, Dave!

[EEVblog]

@williefleete Sure, but likely not great at the low end on the diff amp due to the offset voltage. You could trim errors out though with pots, but that's rather medieval. I'll be using a slightly better TLC2272 in the build.

[EEVblog]

@compaq1275 No surprises, I'll build it as shown. Although the final built product (as opposed to breadboard) will likely use a current sense amp instead of the opamp based diff amp.

[spelunkerd]

As a relative beginner in this field, I've listed these two videos as favourites, for when I have more time to learn the details. What would be nice would be a practical view of the box and circuit board, so I can have some idea of what I need to put it all together. This is definitely one of those projects were effort in will reward the student later.

Thanks for going through this. Is there a part III?

[jacobcorr]

Poor Dave, trying to make videos and you can hear Sagan crying in the background!

[cpakditnon]

I havent learned so much neither at my university nor any other youtuve video, thank you so much for share your knowledge with all of us

[trentjackson]

EA did a lovely lab supply 0 to 40VDC at 3A back in the mid 90s. I built and sold several.

In more recent years I designed a supply ground up to be a bit more contemporary but using the same schema as the EA supply. The schema being the use of op amps and BJTs. The original design used needle movement meters. I used digital displays. 7 segment red LED to show voltage and a bargraph row of 10 LED to show current being drawn. The resolution of the LEDs was switchable from 10mA to 100mA. My design was good for 0 to 30VDC at 1A Dual rail tracking. I did the PCBs myself and did a low production run and flogged them off on eBay at 99-cent auctions. I lost a lot of money. It seems that Australian Made means very little these days. The money that I recieved was on par to a Chinese supply on the other side of the world. Disgusting. Australia is a first world country. Most people in Australia require at least fifty dollars or much more a day just to live comfortably. Middle-class adults would consume much much more than this. Minimum wage is close to twenty dollars a day now after tax. So that is 40Kpa.

[TheCrazyInventor]

Very good explanation. Nice job. I hope you'll do a video on designing a PC for the supply as well. I'd love to hear about the PCB design considerations.

[MatrixOfDynamism]

@EEVblog Once we have learnt simple stuff like linear circuit design (RLC), and stuff about transistors and other simle components and OpAmp configurations, how do we move onto being able to use such exotic ICs? ICs with datasheets that have so many words that look so unfamiliar? I really want to know that. There are soo many ICs how do we know which one is best. since our criteria only defines some of the things, and there can be soo many ICs that fit that criteria.