EEVblog

PART 1 is HERE: • EEVblog #221 - Lab Pow...
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.

[@MarkMcDaniel]

Seriously. Although, I start my first basic circuits / digital logic classes in two weeks.

[@prateekchowdhury3337]

True

[@omniyambot9876]

I usually see comments like this as bullshit. But I entirely agree with this one. Dave Jones is a fucking veteran. NOOOO way I'm close to this.

[@sujatnalokananta234]

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.

[@skynetcybernetics9058]

Lots of traps for young players

[@Rainbow__cookie]

From whiteboards to paper What's next he tap on a screen

[@m1geo]

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

[@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!

[@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!

[@hla27b]

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

[@nachiketathakur697]

did u do it?

[@EEVblog]

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

[@cpakditno4n95]

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

[@EdwinFairchild]

is there a part 3? I cant find it

[@jacobcorr337]

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

[@MarkMcDaniel]

More like, poor Sagan. All that frustration because he's too young to understand the world around him, and lacked that ability to communicate just yet.

[@sabamacx]

Magnificent video Dave!

[@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.

[@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.

[@xFuaZe]

Is it really the best way to up the amperes by adding more LT3080's? And how to increase the voltage range?

[@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).

[@BenBilesBB-box]

Great video , might have a go at building this as i'm trying to learn more about DC power supplies LDO's bucs charge pumps etc :) Think it would be a great idea if you did a video of a dual rail positive / negative dual rail tracking supply? Theres a lot of audio types that would love it !!! Or maybe dual rail is a bit over complicated for beginers like me? Anyone know if the LT3080 can be used for the negative part of a dual rail +-v supply ? have two and reverse the output of the second for the negative rail and link the amp & voltage control pins together for the tracking ?

[@felixar90]

Could you add some circuitry that drains the output capacitor when you hit the current limit? (And also when you decide to lower the voltage)

[@muhammadmustaphaibraheem8632]

Great job Dave, Thanks

[@olafmarzocchi6194]

At 35:17 it is shown to connect the negative input of the opamp to the Adj pin to avoid the error with the resistors. What if that feedback is taken from the output itself? Would it work? it would avoid the 1.25V offset.

[@EEVblog]

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

[@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.

[@power-max]

in LTspice, I stuck a PNP transistor where the emitter was connected to Vcc, base to the input of the LT3080, and the collector tied to the output, and I bridged the connection between the emitter and base with a 10 ohm resistor, so that the majority of the current was routed through the PNP transistor. (same config used for the classic 7805 10A linear reg) which, looking at closer, effectively made a Sziklai pair. In LTspice, this appears to work fine, although I think it does bypass device protections a bit. Can anyone give me insight if this would be problematic in real use?

[@andre-michelgoulet6933]

Love the videos, perfect level. Tap, tap, tap-tap! Lol.

[@First2ner]

man I love this long videos

[@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.

[@Nadrealis]

What type of package did you use for the LT 3080 in your final design?

[@iNotFound]

So this supply will not actually be 0-V-full-range?

[@danielmccann2979]

This is awesome thank for going through this

[@Joru666]

Im wondering why didnt you pull the negative input of voltage set opamp straight to output of the IC? wouldnt it save all the fuss and bring more precision?

[@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?

[@joteromontes]

simulate this, step by step, this will give you the overview of the board you need to set in your bread board... then you can compare your simulation with your real measurements

[@trentjackson4816]

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.

[@Marzec309]

What rail to rail op-amp are you planning to use?

[@PlayZilla.Studio]

Hi and thanks alot for this video! You sir are awesome!!! Can I use lm2576 instead of lm8030 for this project(with some math work of course)? I need a little bit more power for my soldering iron which requires 1.5A...

[@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.

[@techgood]

what can i say, as always wonderful video, good teaching , thank you very much Sir - I am thinking of building a 0-30v 0-30A power supply, should i build or buy?

[@jtb8631]

Is there a negative voltage equivalent to the lt3080?

[@emuman100]

David, this video is amazing! Thank you so much!

[@williefleete]

i got some quad LM324 op amps. would those work ok for this sort of thing. cause i might give this a go, my current power supply uses a regulator made from a 741 a series pass and some diodes for reference , crap regulation but it lasted longer than the 5 amp LM338's cause the transistor is pretty beefy. in fact the transformer blew out before the transistor in one case

[@FalcoGer]

Why do you call the operational amplifier - a comparator - an error amplifier - a buffer and why? as far as I got it, it tries to match the voltage on the output referenced to ground to the input voltage on the + connection. Why do you sometimes draw only 3 connections? What are the other two connections for?

[@darer13]

For those that may have the same question : The name comes from the use of op amps in mathematical operations. The name stuck!

[@sabamacx]

At 35:26, the two resistors in the amplifier feedback loop "can be anything". Why not set them to something high, say 1M Ohm, to keep current low?

[@lambertax]

Very interesting, as usual. Thanks from France.

[@fiatluxstop]

Very nice design. I really like these design to execution projects, and your explanations of the traps for young players really help out for those of us that don't know about the foolishness of the datasheets. But I have to know, do you have a Clint Eastwood shirt for Lab Power Supply part III? :-D

[@hellterminator]

20:50 Dave, you're reading it wrong. The whole solid line is the 2.2 μF cap, the 10 μF cap is represented by the dashed line.

[@EEVblog]

@milos1993milos PWM is simpler though. You need a 10bit one to get 10mV resolution in 10V output.

[@benotsilent6703]

23:03 - made me bust out laughing when you said the power supply driving the power supply would probably be rather stable. I'm starting from a scavenged transformer from a battery charger.

[@FrankSandqvist]

One thing I wonder, why does the offset voltage become worse, because of a larger die? Anyway really great video, as always!

[@nachiketathakur697]

did someone try making one? how was the experience?

[@deadcatism]

Dave, sorry, i do not understand. Won't LT3080 internal current source produce unnecessary voltage drop on 10k colletctor resistor? If i am correct this resistor was initially placed to reduce collector current and this is not necessary since LT3080 has internal source.

[@ch2o2]

..amazing knowledge and presentation, that's great, Dave. But what I don't understand is - when you have so much troubles with pulling your minimum output voltage down to zero (status quo is 0,8V?) ...why don't you bring the GND up to this level - which means: why not realizing a "virutal GND" which is rather easy to do with a smart op-amp configuration (especially for a skilled and smart engineer like you are)?

[@EEVblog]

@CampKohler Never heard of it...

[@slap_my_hand]

op amps are awesome.

[@rish1459]

This is a great video; I just had to laugh at the design requirement change! Even though, in this case, it makes perfect sense (for the application). Your design specs are 0V out. I wish I could tell the product spec guys that -- eh; 0.9V is good enough! Instead, we end up spending more design iterations and dollars to give them the 0V out -- in reality it won't be used down there!

[@milos1993milos]

14:30 would be better to use resistor ladder D/A converter instead of PWM one ? its cheap, and if you dont have I/O you can always use port expander

[@newsogn5148]

Can someone help me understand why on low side current monitoring you still have a voltage drop? Let’s say the lt3080 is outputting 10v to the load, wouldn’t the voltage at the loads input still be 10v?…. As I write this I realize if a 1ohm resistor is used for current sensing then the load can only drop 9v and the current sense resistor will drop 1 volt….. so the load will actually only see 9volts….. I thought of this because for whatever reason I can’t get any op amp to work as a high side differential amplifier…..

[@EEVblog]

@sabamacx You can, but not arbitrarily high like 1M. The discharge resistor can't be that high otherwise it'd take forever for the constant current to kick in.

[@philhooper5769]

Cam for the video content. Stayed for the content AND the accent

[@boldford]

Much as I like Dave's videos I have to turn the sound down really low. His squeaky antipodean accent is like drawing fingernails across a blackboard.

[@ivanblogs]

@DanFrederiksen I'm not sure Dave's KZbin subscribers are the target market for such a circuit walk-thru.

[@vstoykovbg]

I think that when the transistor is turned on it will not lower the output of LT3080 to zero, because there is a resistor 1K between the transistor and LT3080.

[@felixar90]

Old comment, but dropping low is good enough for the current limiting purpose, no need to drop to zero. This should drop the set voltage to 10 mV, which will be enough to limit the current through pretty much any load other than a short circuit. (And even then it should keep the current within reasonable limits)

[@Yarule88]

When is part III going to be uploaded?

[@EEVblog]

@Nadrealis TO-220-5

[@EEVblog]

@techgood Building is more fun, but 0-30V supplies are dirt cheap these days. If buying at least replace the controls with good quality 10 turn pots. Why do you need 30A in a general bench supply? 30V/30V is 900W!

[@BraunsJo]

I think you made a small mistake with the equation at 16:45. It has to be V_In / V_Out not the other way round or your V_Out will explode (75 dB ->2811 V; 20 dB -> 5 V) and you won't get anywhere near the results you gave. For those who wan't to go deeper into ripple rejection in linear regulators this document from TI gives a nice summary about this topic: www (dot) ti (dot) com/lit/an/slyt202/slyt202.pdf

[@CampKohler]

Dave, are you going to enter Agilent's PS contest and try to win that juicy USD11K digital supply?

[@EEVblog]

@TheMcMonster I have little interest in very high power supplies.

[@SamuelJohnsonBungie]

the hell happened to your thumb in that video?

[@MarkMcDaniel]

My thought exactly. I thought it was an errant hammer swing that missed the nail head.

[@nizarch22]

@@MarkMcDaniel why y'all using the same exact filter

[@abdullahalmosalami2373]

Are people seriously complaining about the taps? I didn't even notice the taps until I read it in the comments because I was wholly concerned with the content Dave was trying to explain.

[@carlosbarberis49]

Great circuit and great show, but I think somethings are missing here. I believe you claim this circuit will work as a an adjustable power supply from 0-1Vin for 0 to 10Vout and similarly 0 to 1V Vicntrl for 0 to 1A I out and all of this is done with a single supply rail?? Please show me how. Your circuit will work as described but I need to have at least a small negative rail for the current sense and voltage drive amplifier. I actually used LTC Spice to verify the above. Perhaps I am missing something.

[@vstoykovbg]

Link to the part 3: kzbin.info/www/bejne/bl7UkqVrq8yhmMU

[@efesstuff4936]

Lol 30:50 did you see the message hidden?

[@mrkv4k]

I'm really not in favor of using LM334, IMHO it's too expencive solution (It costs about 1 dollar in local retail store, about 40 cents from wholesale distributor). Simple 2N7002 as current source, with one LED and resistor will do even better job for about 10 frikin' cents!!!

[@mrkv4k]

Ayush Chand I don't know how would a current mirror help :) If you use LED, you can even use it for signalisation that supply is On...

[@thegoodhen]

The current rating of 2N7002 and its heatsink (or the lack of it) makes it pretty much unusable in my opinion.

[@mrkv4k]

thegoodhen Why? Remember, Dave used LM334 to create constant current sink of 0,5mA. You won't have any problems drawing that little with 2N7002. And power consumption? Even at 30V and 5mA (which is not even needed) you will get 150mW -> no problem there...

[@thegoodhen]

mrkv4k Oh. I misread the LM334 as LM 317, not realizing he used LT3080 and thought you were saying he could use the 2N7002 as a power device. You are probably right, sry about that!

[@izimsi]

@TheMcMonster Aren't modern 2n3055 100% fake and having shitty specs, making them unusable?

[@lionlinux]

in brif "never try to make lab power supply by your self"

[@user-cf4lc8bw1s]

awesome 太牛逼了

[@MisterY1986]

I have seen many of your videos, and I loved them because of their simplicity, and because you focus on the principals, and not overthinking things. But at this one it looks to me, like you ran into that trap. In the end you develop an opamp curcuit to overcome the the fact, that your are raping voltage regualtors as darlingtons. So... Why do you not just use a simple darlington transistor? The feedback loops look nearly the same then... The use of constant voltage regulators would just make sense, if you wanted to have a constant voltage or current, but if you let the opamps do the work, which is what you do, a simple darlington would get the job done. And as far as I can see, your regulators will not save you from building an oszilator on the current regulator by accident. So what should be the benefit of using this regulators, instead of a darlington?

[@lionlinux]

Use 494 - it's gonna be easyer