HACKED!: Adding a Current Limit Feature to a Buck/Boost Converter

6 років тому

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More project information (schematic, pictures,....) on Instructables: www.instructables.com/id/Addi...
Parts list (incomplete, see Instructables for more, affiliate links):
Aliexpress:
1x Buck/Boost Converter: s.click.aliexpress.com/e/_dTe...
1x LF33 Voltage Regulator: s.click.aliexpress.com/e/_dT0...
1x 10nF Capacitor: s.click.aliexpress.com/e/_dU4...
1x 10µF Capacitor: s.click.aliexpress.com/e/_d7d...
1x 0.1Ω Current shunt: s.click.aliexpress.com/e/_dSy...
2x 3.3kΩ, 2x 100kΩ Resistor: s.click.aliexpress.com/e/_dTP...
1x MCP602 OpAmp: s.click.aliexpress.com/e/_dTv...
1x 10kΩ Trimmer: s.click.aliexpress.com/e/_dTF...
1x UF4007 Diode: s.click.aliexpress.com/e/_dYR...
1x Voltage/Current Meter: s.click.aliexpress.com/e/_d8l...
Ebay:
1x Buck/Boost Converter: rover.ebay.com/rover/1/711-532...
1x LF33 Voltage Regulator: rover.ebay.com/rover/1/711-532...
1x 10nF Capacitor: rover.ebay.com/rover/1/711-532...
1x 10µF Capacitor: rover.ebay.com/rover/1/711-532...
1x 0.1Ω Current shunt: rover.ebay.com/rover/1/711-532...
2x 3.3kΩ, 2x 100kΩ Resistor: rover.ebay.com/rover/1/711-532...
1x MCP602 OpAmp: rover.ebay.com/rover/1/711-532...
1x 10kΩ Trimmer: rover.ebay.com/rover/1/711-532...
1x UF4007 Diode: rover.ebay.com/rover/1/711-532...
1x Voltage/Current Meter: rover.ebay.com/rover/1/711-532...
Music:
2011 Lookalike by Bartlebeats
Ecstatic Wave, Jens Kiilstofte
machinimasound.com/music
In this episode of HACKED! I will have a closer look at a common buck/boost converter and create a small, additional circuit that adds a current limit feature to it. With it, the buck/boost converter can be used just like a variable lab bench power supply.

КОМЕНТАРІ: 593

@kristiandelchev7362 3 роки тому

To make full CV (constant voltage)/ CC (constant current) operation - the voltage and current feed-backs are to be combined into the FB pin. Whoever is higher will take control. Most commonly people use a resistor divider (to FB pin) for the voltage feedback and current sense amp for the current feedback. How to combine them? The simplest is to connect the current feedback signal to FB pin via diode. The drawback? - diodes have voltage drop changing with temperature *by 2mV/deg C). The most accurate solution is to "idealize" the diode by op amp. The current feedback signal is applied to the non inverting input of an op amp. Its output drives an NPN emitter follower, whose emitter is connected to the op amp inverting input. The circuit can only pull up, but not down i.e. does affect the voltage control in normal operation. Should the current limit be exceeded, the current feedback will take over

@llama1917 2 роки тому

Software Engineer. Always have to remind myself that with circuits and hardware in general you cannot just "get started and refactor when you know what what you're doing more" 😎

@yashsvidixit7169 4 місяці тому

And that's where simulation enters the chat.

@SayanMitraepicstuff 6 років тому

The two main ways Scott starts his video: -Recently... -In ze previous video...

@greatscottlab 6 років тому

But not this time

@DarkSlayer-xk3fb 6 років тому

XD lol

@pablobski 4 роки тому

totally!

@fertilizerspike 3 роки тому

"let's find it out!"

@noelsherron 3 роки тому

“A while ago”

@anugrahkorambeth431 6 років тому

eventhough I donot understand anything, I still watch your videos and I like them. Please keep em coming 👍👌✌

@JKnight89 4 роки тому

This video helps me. I have a junk benchtop power supply that eventually I wish to rebuild, so this gives me a place to start looking for possible starting point. Thanks!!

@epiendless1128 4 роки тому

The issue I have with differential amplifiers for current sense is that they are very sensitive to errors in the resistor values. A 1% resistor error will give an output error of 1% of the _supply voltage,_ which is comparable to the thing you're trying to measure. Alternative is to use a current sense amplifier. Silicon Labs SI8540-B-FWR is just one example.

@thecombatengineer7069 6 років тому

This is very clever and I have enjoyed watching your skills and experiments progress. Thanks for the dedication mate!

@jeffreygoodson2563 4 роки тому

I LOVE the way you explained this! You're a great teacher. Thank You!

@TheOleHermit 4 роки тому

This is exactly what I needed to know/do! Thanks! While using buck/boost converters to build a DIY solar charger on a LiPo power pack (w/o mfr's circuitry), I've fried my rework station's internal 15 VDC PSU, a buck/boost converter, a buck converter, a boost converter, and a solar tracker... so far.🥴 Unfortunately, I was unable to keep up with the video. So, I'll watch it about a dozen more times and head to your project info links. Ha! just noticed a link to your DIY LiPo solar charger video. (How did you know?) See ya. 😎

@Jones12ax7 6 років тому

I used an ATX power supply with one of these buck modules to make a crude powersupply. It worked so well that I plan to increment that and this circuit will be very handy! Thanks!

@shariqzaman2834 6 років тому

I was searching for this type of project for a long time :D ..Thanks GreatScott :)

@Trancelebration 6 років тому

Good idea is to add a bit integration to comparator circuit. Something around 10nF between output and inverting input does the trick. Much cleaner output voltage and less hissing sound from inductor.

@ritvikaneesh5980 2 роки тому

I just started electronics a few months ago and I have learned so much from these videos. I have recently made my own power supply, no current limit feature though this video should help

@fmdj 2 роки тому

When Great Scott has a video on the exact thing I'm trying to do... AWESOME! thanks!

@marlonmartins82 6 років тому

This is exactly what a was trying to learn this week. add current limiting to my power supplies. thanks!

@45llamas 6 років тому

I love your videos and how you explain it function so clearly !!

@tommihommi1 6 років тому

Another advantage of lab PSUs is a much, much cleaner voltage. Try to power a radio with a circuit like this and you'll see what I mean

@greatscottlab 6 років тому

True

@mattimhiyasmith 6 років тому

You should be able to reduce the ripple by loading the buck/boost converter with high load but kinda makes the current limiting in this video pointless :P or use a LDO or RC in series to from the converter

@vaguedirector_7342 6 років тому

I'd just add an LC filter to the output for lower noise operation.

@TheOswald42 6 років тому

I see, LDO, RC or LC filter.....is there more solution for cleaner voltage?

@brucefox6580 6 років тому

A linear PSU perhaps.

@jensschroder8214 3 роки тому

You can also switch off a buck converter by introducing a feedback voltage greater than the reference voltage. In the case of a boost, the output voltage would then roughly correspond to the input voltage.

@ReagueOfRegends 6 років тому

I'm always left wondering, how many people watching here are electrical engineers vs. hobbyists? :)

@philxcskier 6 років тому

I'm sure there are a ton engineering students.. I happen to be studying mechanical engineering, and it's nice to be able to check these out whenever I have no idea what a circuit does.

@Lovreli 6 років тому

Spurdo Sparde both lol

@vaguedirector_7342 6 років тому

ECSE student here, binge watching all the good electronics channels

@aunreza 6 років тому

Electrical engineering student here. I watch these videos for fun but i might build this circuit for a project.

@spudhead169 6 років тому

Hobbyists are 100x smarter.

@jayzo 6 років тому

I've learned more _useful_ information about electronic circuits with the likes of GreatScott than I did in school.

@owalkmachinemaishitechdobr3674 4 роки тому

Your videos are amazing! Thanks to share knowledge and your experiences!

@BlackXeno 6 років тому

Just to be sure if I have understood the feedback as you have explained: when you see the output voltage swinging a bit on the scope, that is the switching noise, not the error direction of the control feedback.

@maxximumb 6 років тому

Thanks for posting this.It's exactly what I'm looking for.

@greenman2262 3 роки тому

GREAT Scott a well thought out and worth while doing little project thanks.

@rtesimpson 6 років тому

Very neat handwriting and schematics!

@navjotsingh0006 5 років тому

I enjoyed it alot and you created what i wanted to have in my little electronic project but its not easy for me to build just like you did it but great video its always fun to watch your videos.

@vaseemmehrancp9372 3 роки тому

Real blend of creativity , fundamentals and hacking

@extrims70 5 років тому

Hope somebody has already caught electrical schenatic typo at 05:49 - differential amplifier IC1A won't work the way it shown :( Non-inverting pin.3 should be connected to junction between R2 and R3. Anyway - that's is great work, Great Scott!

@matejhusek6855 6 років тому

Thanks!!! I Made it and with dome changes i Made my super Power supply!!!! Very good video.

@briannielsbergh 6 років тому

Your videos are just so cool, thanks for sharing your knowledege :P

@dave_dennis 6 років тому

I've done this many times. The problem I've sometimes had was that the high side of the feedback resistor would sometimes exceed the common mode input capability of the opamp. This has often forced a careful selection of a high voltage capable opamp.

@electroumit 6 років тому

Thank you. Your voice and speech is great. I very like.

@houseofelectronics5869 6 років тому

Great video @GreatScott. Your channel is a perfect guideline for any electronics beginner. I learn a lot from each of ur videos. Thanks man :)

@greatscottlab 6 років тому

You're welcome

@PropaneTreeFiddy 6 років тому

0:45 That NOISE!!! You can literally see the LED flickering in the footage. If you want to use a buck-boost converter for anything that requires a fairly stable voltage, I highly suggest adding a good amount of filtering!

@pankajroy5124 6 років тому

Great Scott YOU ROCK!!!!!. Another great video. You are helping and motivating youngsters to learn electronic. Good work. Keep it up.

@apeman9001 4 роки тому

Spoken like a true politician! I take it you belong neither to the EE group nor the hobbyist group, but the bureaucrat group. Just kidding!

@Beakerzor 6 років тому

wow, what a well organized tutorial! well done!

@toastinat0r 6 років тому

great video! Id love to see a Current Limiting circuit for a High Amperage High Voltage AC Circuit (600v-25a)

@engician7620 6 років тому

I don't understand any thing !!! But I love watching your videos It gives me a kind of satisfaction.😌🙏💁

@phrankus2009 2 роки тому

The beauty of Scott not glossing over the finer details is that it inspires me to "really" study the circuit or concept intensively, by consulting MANY sources (including the Wiki, even) until I have a truly intuitive (deep) understanding of the FLOW, the LOGIC, and the MATH. .. I do not care how long it takes. .. I resent being rushed through anything that I do not yet "fully own". .. Scott seems to OWN the knowledge, which he shares, and his uncompromised, comprehensive and detailed presentation illuminates the degree of my shortcomings. .. This allows me to fully remediate my deficiencies, however frustrating.

@kshysztof9649 Рік тому

Yes, absolutely ! When I first watched the Nixie tube video, I didn't knew what was going on, but after few hours of research, I came back to the video, and could clearly see what problems and solution he has used.

@nitinnahar7713 4 роки тому

Really I would say the video is very excellent. You are really Great Scott

@plamenpetkov6958 5 років тому

There are ready made CC, CV Buck Boost converters, with additional trim pot for current limit adjustment. They typically use low side current sense resistor (shunt), making it easier to process the current feedback signal. Typically the current feedback signal after non inverting amplification is fed to the FB pin via diode. The FB pin is controlled by the higher of of voltage and current feedback signals. Nothing wrong using high side current sensing...but the accuracy of the simplest 4 resistor diff amp even with 0.1% resistors could exceed 2% due to unwanted sensitivity to voltage due to resistor mismatch. TI and AD have an extensive range of tiny current sense amplifiers, more suitable for this role than a general op amp (comparable on size and cost).

@rainbowspeedy 5 років тому

Ich don't understand what Scott is talking about. But I love his voice. That's why I watch his videos.

@jossydornelles7606 3 роки тому

GreatScott! Thank you for the class on this circuitry! I assembled the circuito but, for any reason, I was not able to control the output current. I am using a step down LM2596S-ADJ (yes, the feedback pin is 4), and I would like to know: should I have to disconnect pin 4 from the board? How much current I am able to control?

@michaelumenyi6907 6 років тому

Your videos always exists me!!

@richardnanis 6 років тому

Excellent video and tipp! much appreciated! Did you also investigate the behavior of the buck/boost converter when input voltage drops below 3.8 V? I figured out that the output rises suddenly to its maximum when input voltage drops below 3.5V. This would be fatal if powered by a liion e.g. that suddenly drops below 3.5V. Then it could happen that the output of the buck-boost rises to 30 or 40 V destroying an led that might be connected to its output (or anything else). I think i got exactly the same buck-boost converter from ebay (chinese seller) - which cost me only little more than 1 euro.

@Darieee 6 років тому

Amazing as always !

@ergindemir7366 3 роки тому

It might be a good idea to use a pot for the feedback resistor to calibrate the opamp for the precise current measurement.

@manliomalavolti9640 3 роки тому

Great video, thx! I wonder what could happe if a boost converter designed to boost to 12V, sees an input (from solar panels in full sun) coming @ 16V. Would it fry?

@asasif7 6 років тому

Greeting from PAKISTAN.. Greatscott you always do a great job. You are a great teacher for me. i learnt using arduino totally from you.

@kishorgoodday276 3 роки тому

Thanks for this great hack bro...i searching for this type of hack...😍

@vaioskaliakoudas6388 6 років тому

After this explaination, make sure to make the successor of your DIY Buck/Boost Converter, which will feature that as well. Also, the horsepower of an electric motor, depends by how much current/voltage flows form the battery packs into

@matuga92 2 роки тому

Hi, great video as always. Can this be used to power a super capacitor bank? Thank you.

@nosafetyswitch9378 5 років тому

Without really noticing, everyone here is being taught/shown basic control theory principles under their noses! Well done! Usually its scary shit!

@vojislavhoc4467 6 років тому

Great video as always,greetings from Serbia,and i have one question how can i make fine-course adjustments for voltage and current for my DIY variable power supply?

@damascenoalisson 6 років тому

You can easily buy current-limiting converters from eBay... But DIY is so much better haha Great project btw! :-)

@jesussanchez1971 6 років тому

Excellent video.!!! One question. How are conect the two inductors on the PCB? On the datasheet, appears a transformer. Thanks. (sorry for my English)

@stalwartekwere2157 Місяць тому

Nice project

@tansateknisi3541 4 роки тому

Owesome explanation.... bravo..

@techexplained5725 6 років тому

Hi nice vid as always. btw. whats the MIC you are using. sound is crystal clear. thanks.

@pradipkantimandal1521 5 років тому

Great Scott... U r great... Very neat and clean explanation.. ::))..

@theofilocc 6 років тому

Could you please explain the purpose of R2 and R3 in the circuit you designed? Great work btw.

@Nick-zp7hk 5 років тому

wow ..... you are great man, you make great videos ........ super !!!!

@Anthnuno 6 років тому

I discover your videos today! Congratulations! They are amazing! I l have a step down regulator! I need a fix current of 12v, connected to a gel battery! The problem is when the battery is full we regulator to 12v, but the problems is that the voltage of the battery will decrease and voltage of the regulator will decrease too. Do you know any step down that the output voltage can be fixed without input voltage decreases?

@MakerMike-bx5ms 4 місяці тому

Thank you! Nice job!!!

@dzee9481 4 роки тому

Very good video, I have been trying to look for a boost converter that will take a single 18650 Li Ion Cell and boost its voltage from 4.12 Volts to 30 volts. Most of the boost converter go with a min voltage of 5 volts. Is there such a boost converter or could one be made?

@thomasgotthulk3629 6 років тому

comes in handy, thanks

@tusharsinghrajawat9405 5 років тому

Your videos are awesome

@kristiandelchev7362 3 роки тому

It is better to use dedicated current sense amplifier like INA193. The proposed op amp base design has two main deficiencies:first, with gain of 30 the op amp inputs get too close to the power rail. Many op amps have limited common mode range on the upper side. The second problem is the effect of tolerances between the paired resistors. This results in sensitivity to voltage, not just current. Laser trimmed resistor quad IC like LM5400 can help, but it is easier to use dedicated current sense amp.

@BukkitViper 6 років тому

You really improved the quality of your videos, keep up the good work! Also your german so thats a plus. Can you tell me how to build a li ion charger with arduino? I need to measure the current with a shunt resistor but the values from the ADC just make no sense. thanks.

@TheSliderW 6 років тому

Very interesting as always. : )

@joesoh 6 років тому

Hi Scott, great video as always! Mind to share where did you buy the probe shown at :2:49?

@PezDJ 6 років тому

Awesome :D! You shoult teach us how to do a diy VFD for AC power :) if one would want to drive a ac motor to build a lathe or something connected to 230v :)!

@RegiPavan 6 років тому

Thanks Scott for another great vídeo...

@greatscottlab 6 років тому

Glad you liked it :-)

@FarhanRashid123 6 років тому

Luv ur videos . Ur awesome

@cybaneticcybanetic441 6 років тому

great video Scott. can you please make a video on an SMPS power supply build??? it has proven difficult for me to understand

@vaguedirector_7342 6 років тому

Nice, I'd tried to make one myself with a very similar configuration (current shunt & comparator) but never got it to work.

@ajaya1542 6 років тому

Thank you very much I asked for it you did it again I thank you very much

@ehraz786 9 місяців тому

Do I specifically need mcp602 i/p or mcp602 i/sn will do?

@bucketlistbeginner 4 роки тому

Is there a former video or one you can recommend I am using one if not two server smps for a bench supply. I do plating and induction heating plus vac tube repairs as a hobby I need to build a buck boost with CC adjustable as well as voltage with gauges. I need for at least 1500 watts at 24 v any help would be great

@chrysoulakefalopoulou736 4 роки тому

Nice video.A small error thought at 6:20,I think the diff. Ampl circui5 is not correct at the point where you have shown the ground. The non inverting input should be connected after the 3.3k and then the 100k from the non inverting to ground?

@ruimvp 4 роки тому

Hello GS. In this type of power supplies can i use a big electrolytic capacitor at output, like in a linear power supply, to avoid ripple? Thank you. Keep the good schematics.

@milanhlavacek6730 4 роки тому

Due to the quite high frequency i thin its better to use film or ceramic caps

@utkuserin9750 8 місяців тому

Hi. This is the video that I am searching for. Is there any cheaper solution? For example which opamp I can use instead of mcp602? I cannot reach it currently. Unavailable. How I can decide the compınents?

@budandbean1 6 років тому

Man, you are pretty amazing and one heck of an instructor! It's like you make almost everything understandable. Please continue your fine work... :-)

@greatscottlab 6 років тому

Thanks for the feedback. I will try my best.

@micah2936 8 місяців тому

Current can be dependent on load resistance, or it can be dependent on voltage. In this case, it is dependent on voltage. What if you need constant voltage and constant current? Can’t you make a current limiter dependent on a variable resistance such as a thermistor which is designed to heat up for a specific resistance, or a photoresistor designed to be exposed to a specific light intensity for a specific resistance?

@andrejlacko1870 6 років тому

Great scott can you make some type of portable tv with reciever ? Thanks for answer

@kane100574 6 років тому

Excellent!

@mickg8340 6 років тому

Very interesting idea. I was wondering how you would do something similar to this. Lol my thoughts involved a 555 timer IC to increase or decrease the switching time of the feedback to limit the current, which iswhat i believe you are using. Lol i havent checked your schematic yet

@anandsingh8987 4 роки тому

This was awesome..

@pbsolutions119 3 роки тому

Thank you very much

@dokterac6880 2 роки тому

Amazing....

@RealDjMarkuZ 6 років тому

Great stuff great Scott!, I always follow your channel. As an electronics fan I always wanted to do a kirlian camera as an experiment for myself, yes that camera that supossedly takes photos of the aura, it is possible to do that with a circuit?

@tanyalobyam 5 років тому

Great video always

@meanxmeanx1763 6 років тому

It would be interesting to see the voltage on a scope. I fear it would be more PWM style than flat.

@muhammadsayed59 6 років тому

Perfect explane

@MatejVelican 6 років тому

Try making electronic police/warning light with 4 bit counter, with 16 segments making hexadecagon? It might be better because no moving parts.

@Se7enAte 6 років тому

What kind of power supply would I use if I wanted to hook up some LED off road light bars (say 180 watts) as outdoor lights? So taking mains and converting to 12v while supplying enough power. And isn't too expensive

@NNNILabs 6 років тому

@GreatScott!, Why use an Op-Amp?A dedicated Comparator like the LM393 is much faster.

@plamenpetkov7132 2 роки тому

op amp pin 2 connected wrongfully to GND instead of the mid point of R2,R3. Also low side current sensing breaks the input ground from output one. This implies that a short circuit towards the input GND bypasses the current sense shunt i.e. eliminates the protection. Also a current sense amp is preferable to common op amp. In this example the 4 resistor diff amp is sensitive to resistor values match i.e. tolerances result to unwanted sensitivity to output voltage, not just current (1 % resistors may result in say 5% error)

@brainpoweredelectronics3351 6 років тому

Very useful hack. I was looking into doing something as elegant for a a linear regulated power supply. Perhaps you could could think of a similar way to Implement current limiting using an Lm317?

@blackbrayn 6 років тому

Brainpowered Electronics i just burned a lm317 with overvoltage , i was lucky to have a spare lm338 , this reminds me to buy some more.