Why Does An ATX Power Supply Have Two Main Smoothing Capacitors? How ATX PSU Works Tutorial
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- čas přidán 4. 02. 2023
- Have you ever wondered why an ATX Power Supply has two main smoothing capacitors after the bridge rectifier? Did you ever think they could just fit one larger capacitor instead? Well now you can find out how this circuit works, no maths, no waffle, no fluff just the facts you need to know to understand and fix this stuff!
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Thank you
Richard
I am always impressed by your ability to draft up a circuit, in realtime, with annotations, explanatory notes, colour keyed current flows, and graphs. All while running a narrative. Your brain works in ways mine doesn't, and we all benefit from your desire to teach. Thank you!
Thank You 😊
I mentioned your post to my wife and she want's to point out that in her opinion I'm (like all men apparently ) hopeless at multitasking 😂😂😂
@@LearnElectronicsRepair and thats why your wife loves you sir!
@@LearnElectronicsRepair Good explanation but would it be important to have two capacitors rather than one, and also is it really important to change the squar wave for a sinewave? Because the circuit get bigger and bigger and the purpose of it seems strange as the square wave can just as do the job???
@@democracyforallWell yes, it's important to have two capacitors. If you had only one capacitor, you would have no Junction between the two capacitors; and it's important to have the LLC circuit for more efficiency.
You are the best teacher I never had.
I learned more about circuits and electronics in 42min. than 4 years in the University.
I didn’t realize the video was 42 minutes long until it was over. Well done.
the best explanation in my 20 year line, even if 1 capacitor is bad the smps won't work, have 3 cooler master smps 2 with active pfc, trying to repair since ages, no 5Vvsb present in all.
I'm just 7 minutes into the video and this is the most I have learned about power supplies.
agree
I have learnt more in 45mins with you than any other presenter
Fan fook in fantastic! That was brilliant - I was losing it a bit up until the bell analogy came in - the summary brought it all into perspective. Lots learned - thanks very much - 40yrs guessing made easier watching this 👍
the effort put here is so impressive.
Universities must include this to better their lecture
This was an excellent presentation on how this type of PSU operates, the bell analogy for resonance is the best I've seen.
The thoroughness and pace is very appreciated.
You have missed your calling, you should have been an instructor. You are to clever to be playing around with flea market old stuff. Your knowledge is immense and you put it over well.
In schools and universities, you have to follow study plans, deal with students who don't even want to be there. On CZcams, it's different. You were probably looking for a video on the topic of power supplies and you have an interest, and that's why you learn. And don't get me wrong, I also believe that the video's author has an incredible teaching ability.
Your explanations are gold. The fact that you explain what happens to the wave while it passes through the components and why the components are where they are, makes all the difference. Cheers.
Dear. Rich, bell analogy to explain LLC topology is simply...fantastic! Never thought that way...regards from Italy.
Saluti 🙂
The LLC circuit explanation is great. I'd often wondered about that, as it seemed logical that sending an analogue device like a transformer a square wave would not be doing the system much good from a noise perspective. The bell analogy will stick in the head nicely, thanks!
Loved the bell . Always thought about the resonance but genius to think of the pendulum as a square wave . No matter how quickly or slowly you hit the bell with the pendulum, the bell still rings at its resonant frequency . Genius .
@Dave T , Yeah exactly that! The pendulum/hammer/clanger injects🙂 energy into the system but the resonance does the work
Thanks for another great vid. I'm an electrician with limited electronics knowledge (I dabble at fixing gear for myself, friends + family, mostly because I love fixing instead of replacing). I already knew a lot of what you explained but I still learned a lot. Every day's a school day. p.s. Parents: go easy on kids who take their toys apart - they may be studying electronics early but you don't realise it. :)
practically explained perfectly ... the bell was the obsolute example for a resonator 😊😊👍👍👌👌
This is the best power supply explanation on AT I have seen ! Thank you very much. Raj (India)
Of several youtube videos on this subject, your video was by far the best explanation. Thank you!
That makes sense to me now why the transistors went short on the other video when one of the filter caps was open circuit. Thank you for these videos it really does help me understand.
Before I begin watching, I shall say the 2 capacitor type is typical of center-tapped split rail configurations as typically used in half-bridge designs.
There are designs that can use half bridge but biases the ballast resonance capacitor to HVDC Ground instead of half HVDC, they both still work, but the one capacitor configuration requires more support components on the MOSFETs to stop them blowing up.
There's other topologies too, including current mode switching, current feed switching, voltage mode switching and then there's various versions of those too.
Some can put high reverse spikes of voltages on the output (Flyback not using discontinuous buck topologies, thus during the off-time the collapsing field can produce a larger voltage in reverse, apparently, though with the ones I played with, gave a negative voltage of the usual output when rectified and wired to a capacitor. YMMV of course.)
Many of the modern ATX PSUs I use usually have what appears to be some hybrid current-mode flyback topology (Antec 650W, didn't think flyback could do such a power level), the older and cheaper PSUs use this split rail format, which I dislike working on for some reason, IDK why, but I just expect one transistor to go short into a shorted resonance capacitor and charge a 200V capacitor to 380Vdc.... maybe I'm being paranoid about those.
But back on topic, yeah, looks to be a half-bridge topology of sorts. onto watching the video now.
You should start your own channel! Or do you just prefer to try and make yourself look smarter than the people creating the content?
@dedr4m Well, you were wrong, weren't you.
I really enjoyed watching this video. So much so I'll be watching it again and maybe a third time. Your analogy with the bell was a good one. Brilliantly done. 😁😁
Cheers Edwin, I was really chuffed with the bell when I thought of it
Very helpful to my understanding of PSU. The fact you add a sketch to explain things is great.
As always, a video full of well dispensed knowledge.
Side note : not all LLC circuits are resonant. They do transform square waves into sinusoidal waves but it is not what it is called resonance.
In a LLC circuit and basically all RLC circuits, resonance occurs at a certain frequency. The phenomenon is a noticeable voltage therefore current increase in the circuit due to combined characteristics of all components.
Often, accidental resonance means destruction of the circuit.
The same phenomenon applies to physical oscillators. That's how wind or troops walking at pace can destroy bridges.
Very well explained, in fact, clear as a bell.
Yeah I never saw a quality bell that was glass.
Thank you. I thought the bell was the best part 🙂
Thank you for explaining this along with the LLC part of it. I never quite understood the way it worked, but the way you explained it nicely. It smooths the sharp edges of the square wave.
Great video! I had some prior understanding how ATX power supplies work but this video explained some details I wasn't previously aware of.
That was great, thanks for not getting bogged down in the resonant imaginary components!
I learned so much from this video, I feel like I owe you money now 😂. Thank you so much for this. You have a new subscriber.
Really enjoyed this explanation mate.
Thanks for taking the time to put such effort into this video.
Thanks so much Richard. You pretty much answered any questions I had. I have a few on the bench currently, an ATX psu from a customer computer that came in. swapped for a good one now I'll look at this one. I've got a bazillion of them here to play with.
Excellent video ... worth watching several times to internalize. Thx!
Thanks for this one, Richard. Great explanation 👌
Addicted to your videos now, so glad I found this channel, I have learnt so much and find your description of circuits very clear and easy to understand. Thank you sir
Great explanation I was wondering why there's two caps instead of the usual 400V caps, now it makes sense. Thank you
A good simple explanation, of a complicated circuit. Thank you.
Very informative, feel like i am back in school, new suber after watching this. Ty for your effort and time.
Thank you for making the operation of that circuit easy for me to understand,. I really enjoyed yout explanation.
I appreciate the clear explanations, as well as saving power supplies from the e-waste bin.
Excellent explanation of LLC resonator circuit for higher efficiency. Thank you very much.
Brilliant Explanation! I don't recall a great explanation in my electronic classed where theory meets reality. I really enjoy your videos. Keep em on.
Thank you for commenting and attaching this video, it's a new to me, but I've watched it. I mean the video :D cause I didn't have LIKE on it till now. But, I will use it for my apprentices and technicians as it's a GREAT resource for them to learn. Like a all in one :).
Much obliged for your amazing work in educating us!!!
GOLD. The bell made it much easier to understand it.
Brilliant! Devastatingly useful! Thank you! Liked and Subscribed.
On older supplies they have a 110/240v selector, somehow the selector changes the capacitor config to a voltage doubler
Yeah, we can have a look at that. One of the PSU I rejected when making this video (as over complicating things) has the 240V/120V selector and it simply shorts two points on the PCB when set to 120V
For 120V, the center of the 2 caps is tied to the AC neutral. The diode bridge charges one cap on the positive half cycle, the other on the negative half cycle. It's basically two half-wave rectifiers, AKA a voltage doubler, to get 320V DC from 120V AC.
Very well explained as always. Thanks Richard
The world's best teacher thanks sir
this video tied up so much about what I learned from you in past videos - thx!
Great explanation Richard. Love the Bell idea, it makes sense. Many thanks
Brilliant! Many, many thanks! I have to say, all of your tutorials are simply amazing. I have learnt so much. Thank-you again!
Nice job. Thanks for the description, very visual, loved the bell analogy, I will use that.
gave you a thumbs up especially for the bell analogy
I learned a lot! I always thought transistors were low voltage devices. I can see now that I could fry my oscilloscope if I were to randomly probe transistors inside one of these supplies!
Be careful connecting your oscilloscope to the collector or drain of a FET switching transistor. I have done it but don't recommend it. Best to use a high voltage probe to prevent damage to your scope.
A video that could be helpful:
czcams.com/video/xaELqAo4kkQ/video.html
Thanks! Another brilliantly explained subject.
ding dong.............. ive never heard it put like that before. it really makes the point. thank you richard
Thank you, thank you, thank you! I learned a lot of very helpful information and now understand this stuff better!
Thank you for this very detailed and easy to understand video. And yes, i did like the bell analogy! :)
Thanks for the recap on Bridge rectifiers, hadn't seen that since 1st or 2nd year Electrical engineering degree.
Fascinating - great design and explanation.
Thanks for the very educational video. LLC is a new thing (at least it is to my old brain when thinking about SMPS LOL).
thanks for your teaching you do a great service for the people who like the electronics. long live with the god's blessings....
Explained very well. Thank you.
Brilliant work. Really clear. Thank you!
Brilliant job , one of your best yet. Thanks.
So , if you did change the value of BOTH of the large caps to a lower capacitor value (not voltage rating) it would still work but at a lower max output .
Love this video Richard! Thank you!
Great video, very well explained.
Great Stuff ! Thank you, Richard.
Great explanation, always enjoy your videos...
Great analogy! Love the video
really enjoyed the video
and learnt something new
Quite a good presentation. Liked the bell analogy.
I'm honing my understanding of the functions of and the relationships between these components and the resulting outcome. With your help. I really appreciate it.
Would it be I were just approaching career age level of life, but that is not the case. Strangely, I never feel like an 'old dog'. Never have felt fully 'grown up'. I suppose my inate sense of curiosity multiplied by a strong desire to understand things, (and then put that to use)divided by my age , in years√ has helped to learn new tricks, everyday, which we all know, an old dog cannot.
There may be an algebraic formula in the preceding lines, and it may need to be revised, and I would absolutely and happily accept any input from you all out there in comment land. 👍
Very good Richard. Many thanks.
Great explanation ! 🥂
Very nicely explained !!!
Thanks!!!
Good explanation, thank you.👌🍒
what an awesome explanation :)
the video was very informative , thanks
Thankyou. Awesome tutorial
I am fixing an old Iwatsu scope's power supply and it has dual diodes for 12V, -12V and 5V rails and the anodes are actually connected together. And a single 4ns rectifier diode for the 54 volt rail. Not sure if it was done for added current handling, but the specs for rectifier diodes were hard to meet with newer components when I looked for replacements. The 54volt rail consumes the least current so they used an ultrafast 1 amp diode for it, but other rails are higher current.
I ended up replacing the 1 amp diode that had burned with a 4 amp rated diode that had a matching forward voltage/current curve all the way to 1 amps. And I only found one that had matching speed, capacitance and forward voltage when I looked up from Mouser :)
Nice, thanks for your explanation
Great explanation I loved it '👍
You really do make a great teacher! Some of the others just run through everything g way to fast at least for me. Not enough time to think about what they are saying, but you are great!!! Thank you! I said this before but you should build a single to 3 phase converter. I think it would get a lot of views
Why rectify the AC, only to convert to +/- square wave to put through a transformer? Why not stick the AC straight into the transformer to derive the lower voltage rails, then rectify only on the secondary sides? Especially if sine waves are more efficient at driving transformers than square waves? Just discovered your channel -- you're the first person I've seen explain ATX power supply topologies in this much detail. Thank you!
Yes i did learn, apreciate it.
Very interesting watched pretty much the whole thing, wish there was more on what's driving the two power transistor bases though .
Hey up nah rich great vid m8 learning all the time 👍antiphase is my word of the week KTF
Great video. Thanks
You are a legend. Thank you.
a good video. Most of the power supplies I have worked on with 2 smoothing caps have either been as you describe here or they are 110 240 switchable or even autosensing using a thyristor between midpoint and bridge for 110 240 selection, of course, most modern PSU's have PFC so no need for the selection.
I was waiting for him explain the clever way of allowing a 120/240 voltage selector for free in the design as well. like this i.stack.imgur.com/1jiaD.png
When this PSUs are 120V/220V switchable they pull an extra trick, at 120 circuit is more like a capacitor doubler circuit, so V+ is still 300V or so. At 220V is just a full bridge with the two caps in series and V+ is 311.
Thanks Sir, very helpful
28:20 You forgot 1uF polypropylene capacitor in series with the winding. This is critical. Actually it holds the charge.
Great teaching..thanks.
Excellent! Thank you.
Great work !...cheers.
Amazing ability to tech complex ATX PSU. Pls make some latest ATX PSU anatomy.
Go Ahead.
Good work!
Love the bell anology.
im sorry, in respect to your knowlage of electronics love your work (1) {12:45}' neutral is zero ' my understanding any A.C. current is ( positive is above zero & negitive is below) though we do see it in a way it apears to flip over, (2) i had this problem myself with R.F. high frequency a.c. ...ground, neutral, earth, ..and i will say thank you for sharing you knowlage with us cheers