Howto repair switch mode power supplies #1: basics, and block diagram of a PSU
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- Опубликовано: 1 окт 2024
- The repair of switch mode power supplies (SMPS) is economically a good investment for electronics repair shops and for hobbyists. However, in contrast to the old low frequency transformers and linear power supply units (PSUs), SMPS are rather complex. Still, due to their low weight, high efficiency, and being able to provide stable voltage output, they have became an ubiquitous component in almost every electronic equipment.
I assume that the viewer has only a basic knowledge of electronics. In this video series we will cover SMPSs and ATX computer supplies starting from the basics and going into the details in the repair of such units. Here we look into the most important components and building blocks of an SMPS, and we cover the block diagram. Understanding the block diagram is highly important, since it provides an easy way for a technician to narrow down the potential components which are defective in an SMPS unit.
Due to high amounts of heat dissipated and high switching voltages, and frequencies, power supplies are the most frequent source of failure. Thus, although it takes more time and effort to understand the basics of SMPS, in the long turn it pays off to learn about their inner workings and also about their most frequent failure modes.
In this video we cover the power input, filtering stage and rectification portion of an SMPS. I explain the need for inrush current limiting. Next, the power distribution is explained on the high voltage DC side, where through the two different paths the stand-by and the high power chopping circuits will be fed, driving the transformers.
The main building blocks and how they are tied together in a modern switch mode power supply:
-power input plug or cable for mains voltage
-input protection (fuse, metal oxide varistor MOV)
-EMI/RFI filter (Xcaps, Ycaps, common mode chokes)
-rectifier diode bridge
-inrush current rimiting NTC Thermistor
-active or passive power factor correction (PFC) circuit
-bulk mains filter capacitor
-controller circuit for the FET of the stand-by power and main power
-switching FETs
-stand-by and main power transformers (high frequency ferrite)
-Schottky diodes for the secondary side rectification
-electrolytic filter caps
-voltage reference circuit
-optocoupler and feedback loop
-over-voltage and over-current protection circuit
Finally someone explains what the parts do and in what order they do them , Thanks !
hi everyone ,if anyone else needs to find out about
remote computer repair
try Saankramer Electronic Magazine System (just google it ) ? Ive heard some pretty good things about it and my mate got excellent results with it.
Why are you watching electronics vids? I thought you were an architect...!
start from 5VSB check
Yes indeed
@@paulrichard4945 scammer
Understanding electronics in layman's terms ,I've learned more in this video than hundreds of other ones thank you 👍
Absolutely brilliant. I love the diagrams and your abstractions are spot on for me.
Thanks for the comment. Please go through the whole series (I am still producing new episodes) because it will describe the whole SMPS step-by-step for hobbyist repairers and for repair technicians.
You mean that your teacher never taught you well?
If you’re reading comments to know whether to watch this video, I’d say go for it 👍🏻
Literally amazing!
I feel like I can say with confidence that I understand circuits a lot more now.
The best video I have ever watched about psu's. Thank you, appreciate it.
Great video. Much better dealing with the blocks before having to delve directly into the countless variations of schematics. Top level view and back to basics is always a better approach.
One word of extra caution however, especially for the UK (and potentially, previously British colonies) the nominal 220-230v European mains, in the UK tends to be 240v nominal (still within the European spec limits) but is OFTEN sitting at 250 volts AC (my own domestic mains supply certainly is).
This means the the rectified mains DC bulk capacitors frequently have a static DC voltage of over 350 (!!) volts (250 X 1.414)! Please use great caution when "playing" with such supplies.
Also, PLEASE DO NOT do what many people advise and simply short the capacitor terminals with a screwdriver! This is potentially lethal to your eyes and skin! The stored energy (0.5 CV^2) can easily exceed 15 to 20 joules or more and is MORE than sufficient to blow the end off the screwdriver as molten metal!!!
Use a voltmeter FIRST, a sufficiently high value resistor SECOND of say 5 megohms and 0.5 watt and suitable for the voltage (yes, resistors have a voltage rating too). If in doubt use multiple resistors in series instead to "bleed" the energy from the capacitor. Strictly speaking GOOD designs will incorporate such a resistor anyway, but never assume that.
ADDITIONALLY, using a screwdriver or other short circuit can easily cause hidden internal damage and or weakening of the capacitor which will simply cause long term unreliability!
Very informative comment.
Especially microwave oven capacitors ;-)
Yes, I've seen damage to switching FET''s and IGBT's due to this foolish practice. At my bench, since I deal with large linear and switch mode supplies, I utilise a 200 ohm 20 watt resistor that has old volt meter style test probes attached to it to discharge these primary filters.
For someone brought up in the valve/tube era, this type of tutorial is simply excellent. I very much like your step by step approach, and am really looking forward to subsequent videos. Thank you very much for sharing your knowledge in this way. Saludos!
Valves were the real deal. For audio they are still *the best ever!*
I started out with valves, since as a kid I had no access to books on transistors, and even Germanium transistors were hard to get from used Russian electronics ;) Just keep on watching the series, I will make more videos for sure.
Much respect and appreciation from Kenya for the time, dedication and patience you have put in this wonderful series to impart this invaluable knowledge in such a simplistic and holistic way!!!
Thanks mate. This was a great vid. I'm looking forward to the next one.
This was exactly what I was looking for. Helps so much to understand the schematics and identification of parts as a rookie :)
Thnx a ton for making the video, liked and subbed.
Me too!
Thank you thank you. I'm watching from Zimbabwe Africa. This what I was looking for. I love your video.
Thanks so much for taking the time to make such an informative video!
great mate, simply great. also loved your comment about mathematics nonsense in university and any education about what you really need.
Yeah, nowadays sadly they pump you full with stuff what you will almost never use, and things which you can easily look up in a specialized engineering book. In contrast, the basic ideas, working principles and showing you the rope of designing stuff are almost never given, which is a shame when we consider how expensive "education" is. From some YT videos I learn more in 5 minutes, than I was from sitting through a 50 minute lecture.
Couldn't agree more regarding useless mathematics:
They tried to teach us how to calculate the capacitance of a component given its physical dimensions & the material used as the dielectric.....
I still have the ridiculous formula somewhere, including all the factors for the various possible dielectric material....ranging from air to blackberry jam!
(Only joking with the jam....but you see my point.)
Why? Just why? Complete waste of time.
We were training to be 1st Aiders on electronic equipment...not designers.
And it still is this way today:
Seems to me, they are just extra hurdles put in the way of practical guys with great common sense, but not necessarily with fabulous mathematical skills!
The 3-year course I took could have been easily cut by 50% without the totally Useless-In-The-Field mathematical aspects.
Thanks, your videos are among the best on RUclips for the practical repair of electronics power supplies.
Well, so far I am presenting mostly theory, and many people are complaining about this. However, explaining practical repair without basic theory is impossible.
the best video about how switch mode power supplies work
Thanks for the positive comment!
so true 1:30 I went to tech school too and they gave us math books instead of showing us real world troubleshooting steps. I wasted 30k, 2 years of my life, and that school closed so my degree is worthless but still have to pay off that gov loan. On job experience, license or certifications I highly recommend. thanks for sharing your knowledge 👏👏👏👍
Finally someone who thinks the same as I do!
When I give people advise that nowadays schools often tend to be a *huge waste* of time and money, they think that I just want to stop them from reaching their dreams. I wasted several years from my life looking into textbooks for almost nothing...
As you wrote, experience counts more than a degree! One can get a degree *after* if it is required by the employer. Especially in the field of tech and IT, certifications are the real deal.
Back in my days "1980" when I took electronics, was the same way. The only difference with me was that my dad was an electronic technician Radio/Television... He taught and showed me the how's,when and why. But I agree Tampa Tech.. my books which I still have them was too much math and little hands on... am sorry to know about your unfortunate event. A personal note.. I love Cleveland Institute of Electronics!! my dad always spoke highly of them. In any event you are great Tech Bro!! Joe-K4JGA - JGA Electronics Repair Center - Fl
Donkey Learning IT so true, billionaires will say the same thing and they have. The government wants us to go to college because they make money off of that loan interest but reality is that experience, certifications and licenses are more valuable in tech field.
Samsun lcd
Sounds like ITT to me. I went there 2 years. On the job training gives much more valuable experieince.
Excellent presentation ""despite"" or maybe thanks to not using unnecessarily complicated diagrams and animations.
Thanks for sharing Your knowledge :)
Best regards
Information and explanation = Amazing
Accent = Priceless
Keep up the good work! I'm a huge fan!!!
I think he's Romanian.
@@milanhorvat6494 Austrian
Thankyouforexplainingwithsimplewordsandaveryeloquenttalkingthattomeitshouldbethewaypeopleintheenglishspeakingworldshouldtalkfromnowon.
Great video. finally i understand switch mode
Ahh, you just got started understanding the Matrix, but this is just the beginning ;)
There are several more videos in the series, and next year I will upload more until I cover all parts.
very helpful, schools need to really start teaching practical theory of how things really are.
From many years of college, schools are a business there to make money off of people, they do not teach practical skills such as how to do things to earn a living. They do not help people with actual skills to get a good income, or anything else other than theory and have not since John Dewey was involved with education. In the 1800's and was completely removed after 1980's as there were classes in the 1970's and 1980's as I had taken a few. But when all the shop classes were removed along with adding none left behind the complete education system is there only to program people to think a certain way, and no practical skills. I say this from knowing a number of teachers from grade level to college classes. Also I have a masters in engineering, and have passed the exams to be a teacher, and engineer etc. Even when I was taking the hands on classes it was not directly the school but ROP. Think about what no child left behind is, it means the classes are designed to bring everyone down to the level of the lowest student and not put them in the special classes that they belong. Also students are taught to pass a test instead of get the life skills that they need and with those skills they could pass ANY test. There is a big difference between helping and programming, when people ask for things that the ones in charge do not like they get thought programming. The best thing is to have community home schooling and get back to just a couple books as was used in the 1860's when those people could do things that most people with a doctorate would have a hard time doing. That is someone with a single room school can and did the things most are unable to do with a bachelors degree. It involves thinking for ones self, and not thinking to what someone else has put in a book. This is dangerous thought to those who pull the strings in this world. This world from what I see is there far more to promote harm than good. It is more of a crime to attack those who harm us than to harm others. This goes against everything that many of us have been taught for thousands of years.
P R you are 100 % right! ROP student here too.
Just got more thumbs an subs comrade, our collective pursuit of, and access to knowledge(like this especially) benefits all society. =) thank you.
Are you serious? Where have you been my whole "electronics" life?
Definitely the best video on components ever made!! Very Much Appreciated!
Great Video Nice Explanition
This is a brilliant video. Thank you!
Thank you, you are such a great teacher subscribing and notification is on. Thank you thank you.
Very helpful video,thank you!
Stick around for the new videos as well. It takes a while for me to produce a video, but sooner or later they will be uploaded.
This is the best tutorial on switch mode power supplies. A++ Thank you
Awesome better than all Universities in the World....!!
Thanks for the positive comment. Though, I really hope that university education will never degrade below the level of a random video done by a donkey published on a social media platform. I still have hope in higher education...
@@DonkeyLearningIT lol...ok
The reason semiconductors are so called is because they are less conductive than conductors and more conductive than insulators. Not a preference for DC as you suggest around 7:00
Ok, you are right, but dont just skip all the good info he said to catch him on this only, everyone makes mistakes, there is another mistake he said when he was talking about the NTC values but its fine everyone makes mistakes and im sure he learned from it. Thanks to him for the good video
Best video I have seen for explaining how a PSU works. I'm looking forward to watching the next parts! Thank you!
Thanks for the comment.
Since I have the slides all done, it should not take too long to make the video.
On Friday it should be out if all goes right.
@8:10 FULL BRIDGE REKTIFAJAAA! :D
Not a dumb single diode rectifier
i see you too are a man of culture
Blade Runner ElectroBoom fan detected
Great course, thanks for taking the time sharing this, much appreciated 👍🏻
Great video. Just amazing. You made it so simple. Can’t wait to watch the part 2 of the video.
Kimondottan színvonalasan beszél(sz) angolul nyelvtani szempontból - viszont kiejtés szempontból szívesen segítenék (ugyanezt a szöveget újra felvenni) mert amúgy rendkívül jó anyag lenne. Dzsászt disz inkredibli hángérijen pronunsziéjsön, ju nó :)
I bought a Nox Urano II 630w atx power supply, but it never turns off, with the fan always running without being connected to any motherboard, I think the green Power On wire is short circuited with the black wires?
How can I solve this problem ?
very knowledgeable and practical presentations. I have gone through all videos related switch mode power supplies. Its just my hobby to look into faulty electronic devices. I have JBL system Called DSC-500 {DIGITAL SYMPLY CINEMA). The power supply runs for a while and then switches off. After a while switches on by itself. ON and OFF goes on. Even after going through all your videos I am not able make what is problem. is it possible for you to suggest or guide. thanks
I have a power supply that input volt 110 to 240 and out put 14dc, the problem is it working in 110AC BUT NOT WORKING IN 240, Please help me to find out the problem
Sir can pulse be sent to igbt gate by only two transistors (8550 and bc 548b) in smps ( without microcontroller or pwm ic) if yes then how?
If you were a super hero you'd be MR FANTASTIC - a massive THANK YOU
Thanks for the comment, made my day.
Related to Mr. Fantastic, I was thinking about that famous Frank Zappa song ;)
Cannot write that refrain from the Bobby Brown song here, because RUclips would censor it out.
hey guys, i have a power supply MAXWELL - 150 - 5V 26A for a LED panel. My first diagnosis was that the F5A 250V round fuse was blown so i replaced it and it blows again. I'm new in this field but i really want to repair it, new ones are expensive and the repair doesn't seem to be that expensive. Any advice what else i should check? Thanks.
hello sir you are the best i loved the way you explain things ' thank you very much
This comment will probably be buried where no one will see it, but on the off chance someone comes along and reads all the comments before embarking on this playlist, be advised that while there is much to learn in the videos that are already posted, as of April, 2021 there have been no new videos posted in over 2 years and the playlist stops while still explaining theory of operation. It never actually made it as far as beginning to describe the repair of SMPS.
Hopefully @Donkey Learning IT will someday return and finish the series, what's already here is great and I learned a lot!
Rick your only about 5 lines from the top so your comment is not wasted. I read it and i make note. Even though its not finished Donkey does a real good job of explaining electronic circuit blocks for beginners like me he has given me enough basics to look around youtube for other tutorials on electronics and there lots of those that don't explain basics. Thanks for the heads up. I specially like the way he explained the block diagrams very slowly. to help beginners understand every step. see I'm already babbleing. Cheers
Hello,
I'm not quite sure how to calculate the DC to get the AC [once it has gone through the rectifier bridge] I'm not getting the same values as you. And what is 1.4142? Please let me know.thank you
Specifically referring to two things, the fact I modded my ytube handle successfully, and failed to sign out on first try... G@@g1e true is 3√|L
I have a question
On a power supply that has a 110 and 220 switch
You have it set to operate on 110v and you accidentity plug it in 220vac the fuse blows and maybe you destroy the electrolytic capacitator . why does the electrolytic get destroyed when it works ok if you have power supply set for 220 and plug. Into 220 ?
Good day sir, i have longwei 30v switching psu, do you know what could be the problem? It only reach upto 8.9v? I tried to replaced the multi turn pot but same issue. It wont turn upto 30volts
One of the best tutorial video ever on this topic.... thanks a lot for sharing
I shorted my ender 3 3d printer power supply, when + and - touch the machine off, then i remove the short and its on again, but now the voltage only 19v, its supposed to be 24v, can you point me what is wrong with my psu?
Great video, and excellent approach to breaking the system down to explainable sub-components.
Appreciate your knowledge and no disrespect but you digress a lot, easy to loose interest. It would be helpful if you had left out needless information and covered the primary operations. Few care about things like companies saving money by skimping out on parts... just sayin.
Very easy to understand. Thank you sir.
Thanks you sharing, very impactful knowledge
Hi bro, please do a video on this topic or please farward some information,What can cause a power supply voltage to exceeds it's settings And how to find the cause and rectify the problem.🙂
This is exactly the video I've been looking for!
Yahoo! this guys accent is really strong but he is going slow for blockheads like me and he really is giving an excellent electronics and diagnostics class. Hope he gets a good job as a teacher in his spare time high school kids and me need this kind of teaching and a little math (This puter has a calculator} to show the equivalencies. DONkey huh oh well Liked an subbed!! I hope he shows how to charge a car ignition cap for fun and profit. in my auto shop class when people rode dinosaurs a fun trick was to charge a capacitor and leave it around the distributor machine for someone to pick up . this was some fun!!! shocking what kids do for fun! cheers
Long explanation. You think people watching this has a brain of a kindergarten?
I get it already. Move it to the next session. Please make this whole series just in 1 video in like 15minutes or less. I already watched the whole series and feel like wasting some of my time
Very good information for me. I have a question : My Panasonic music system create noise like humming on radio mode when I power on my house led bulbs, chargers etc. What is the solution to get rid of humming noise. Thanks in advance
I could not agree more with tampatec. The series of videos is absolutely fantastic. I will be sending links to my friends who might be interested. Thank you very much. Your presentations are wonderful and even for my puny brain they will be imprinted for a much longer period of time than would have been the case with all the math and a book. My undergraduate degree is in mathematics but this is much better. Having watched your series of videos I fully understand why you have broken this information down this way and have this much detail in your presentations. Thank you so much for all of your efforts. Do you have a patreon account?
It was about time to see such videos. This subject was never well explained before. Thanks for sharing!
Thanks for watching and commenting as well!
Excellent...i wanna know the difference between NTC wich used to limit inrush current and the viaristor whic used with fuse in protection srave?
Great video, loved it, one question though: Iz there eni kvestcsön? Köszi
The explanation is beautiful as video shows the functions step by step. Incidentally the title will transform the learner from donkey to racing horse so the title needs to be rewied
As a Hungarian I have a difficult time understanding English with a strong Hungarian accent. Do I hear that here?
You teached me so much! Your diagramm is really easy to undertand aswell!
Greetings from Germany.
Leon.
I'm glad you liked it!
Though, this is just the first part of the series, most likely you want to go through the videos in the playlist. Grüße aus Österreich!
hi donkey . are you still doing more .when will part 12 be coming .top top teaching my friend
Hi enjoyed your video and wonder how to contact you Maybe you could send a message via The Clever Coop Company
Very good explanation. Thank you.
seerku means circuit. I understood after couple of minutes.
Great vid. Im a newbie who try to fix my totally dead projector, and it is what im googling for, can't wait to have the next vid. Thank you
The follow up video will be up next week.
Btw, is the lamp of the projector actually being fed by an SMPS?
Just asking, since in the more simple projectors which I have seen had no regulation, and they used just a special high pressure incadescent halogen lamp.
Thank you very much! Very good explaining. I am electrican and repair TV s for fun/ hobby. i don't like the way of the manufacturers nowadays.
They want that we buy every 2-3 years new insted of repairing the items.
Your video is the best that I found in the last two years. I am looking forward to the next video
It is sony vpl-dx140, the stand by led doesn't come up. If i disconect the mainbord there are only fluxtuating 1 to 3 volt, 8 to 11 volt, at the output meauserment of the SMPS.
Are there any voltage levels shown on the PCB? I mean on the PCB mask are there any explicit levels defined, like +5V or +3.3V for the standy-by?
If there is an explicit stand-by voltage shown, track it down, and try to figure out where does it go on the PCB of the SMPS. First thing what *must work* is the stand-by power (it will be covered in the second video, which I have already half-way done).
Be *super* careful of not to touch anything due to the high voltages present!
By fluctuating voltage do you mean that you move your multimeter on different output leads, or you keep it on the same lead, and the voltage fluctuates? In the latter case the SMPS might be just turning the high power stage down, since it detect no load on the output.
Thanks for you kind words. The second part of the video is almost done. The audio is a bit messy since I am having a cold, but it should be still informative.
Regarding the 2-3 years, I disagree. Most manufacturers want you to buy a new product *every year*!
Great, really helpful video. Thank-you so much
This guy will talk your head off and you'll have to jump to another video another video in another video
5 seconds into the video i became a new subscriber...good job....
Thanks for the feedback! Btw, I hope that after you watched the rest of the video, you have not pressed the unsubscribe button twice, the unsee button and the thumbs down button as well ;)
It's very interesting playlist,can you add subtitle for this?
Great video - Thank You for making
Very well explained! Thanks!
Donkey reading electronic articel seems like expert one but I think not Donkey😀
What about atx smpsu works in schematic diagram explain
saludos muy interesante la funcion de cada parte de la fuente conmutada..
Thank you so very much, you are so clear and concise, I've been out of electronics repair since 1990 and trying to get caught up!
You are welcome. Since 1990 some things have changed, but most things stayed the same, as usual.
Are you interested mostly in digital or in analog/power electronics? Namely, nowadays everything have become digital.
Same here Joseph...I gave up with the introduction of the microchips....
But when you consider now, that most problems are directly down to the power supplies.... this stuff here is extremely useful.
The microchips, after all, are dealing with currents that are so infinitesimal, the problems, generally, are 90% of the time somewhere in the power supplies...Where heat & current levels are high...and there are lots of them.....
I strongly recommend the videos of TAMPATEC.
Excellent video, thanks for the time you put into this! Explained very well.
Liked, commented and subscribed. That's great.
Many thanks man. Wish you a happy new year!
beautifully done am now going to watch your other vids thanks a million
really funny accent, but really well explained 👍👍👍👍👍
Hello Sir, thanks for the explanation,I really enjoyed it and I wish to have more videos like this one from you. I love Electronic so much and I'll like to be an expert in this field
I hate bullshit flow charts power point shit slides ......show the circuit with em connected and how to test them without datasheet lol
Nice sir i love electronics
❤❤❤ good explaining about how this works
Thanks to the likes of you, RUclips is a school 🏫 in itself.. thumbs up to you 👍
Donkey Leaning .. EEEAAWWWays explains it better .......great teaching method.Thanks
Hi... Can i replace tny276 with tny278?
Subscribed before watching to the end!
This came up on my recommended channel list (on 2024) and I have to say that this is the absolute best explanation of how these circuits work, thank you so much for uploading this, it has given me a lot of confidence in moving forward to trying to repair these power supplies. Thank you 😎👍
Great video!!one of the best tutorial of SMPS on youtube
Thanks for the feedback. This is just the first part, introducing the power input circuit. If you find the video helpful, go through the whole series. More videos are coming up, part 7 should be uploaded soon as well.
thanks for this great work.keep it up please!!
4:17 Clunking power switch? That's a new one on me!
Excuse me Sir is NTC polarized or Non?
Absolutely positively Superb! Very well done. Great teacher.
Does the number 1.4142 have a name? Is it called a "constant"? Or a "factor" A "coeficient"? Please let me
Know. Great video. Cheers!
Square root of two. I would refer to it as a factor.
Sir my power supply shock me with a huge current when touching the red probe aslo the black probe.. even 5v dc can you help me please....
0-15v 3amp -my power supply
lesson #2 answered my question.