ฝัง
- เผยแพร่เมื่อ 21 เม.ย. 2021
- Episode 772
Let's look at a switch mode power supply. Reverse engineer and draw schematic. Then look at the design. A basic introduction to switching supplies.
My videos on DC-DC converters: • #689 DC-DC Boost Conve...
Power supply used: www.banggood.com/custlink/vKK...
Be a Patron:
/ imsaiguy - วิทยาศาสตร์และเทคโนโลยี
Very good explanation of one of the “mysteries” of electronics - AC to DC switching power supplies!
A few comments/suggestions:
1) You forgot to show the “AC side” GND symbol/connection to the “-“ side of the bridge. This is typically designated with a different and unique GND symbol to signify that it is DIFFERENT than the GND potential on the “DC side”.
2. The “DC Side” GND symbol should be unique and distinct from the AC side GND. They should NEVER be connected together.
3. You should highlight the main reason for both the transformer and optoisolator is to create a galvanic isolation between the AC and DC sides of the circuit to prevent stray currents, emi noise and, to safely separate and isolate the high voltage AC and rectified DC from the low voltage DC side of the circuit.
4. Finally, perhaps a mention should be given for connecting an oscilloscope to this circuit..esp the AC side and how this should be done with a high voltage differential probe or a battery powered scope that can handle high voltages.
And finally,
5. SAFETY FIRST when working with high voltage AC or DC circuits. Preferably use an isolation transformer and a VARIAC.
Final note: Y” caps failure mode is “open” and “X” caps fail shorted..which would cause the AC line fuse to blow.
These caps control and minimize the common mode voltages and currents.
This channel could never get enough credit for all the work you’ve done here on YT.
Best switcher video I’ve seen.
Thanks
Your videos are excellent! Great content, explained masterfully. A pleasure to watch.
My first vid of your channel. Liked, subscribed - this is exactly the walk thru that works for me. Especially since I've taken to looking at the various power supplies I have cannibalised from computer and tv equipment. I appreciate the way you describe a device by mapping out the circuit and providing explanation about the chip and circuit operation. Nice work.
This is super helpful. I am working on a power supply for UMN smallsat ground support equipment, but my design is the bridge rectifier -> capacitors -> voltage regulators -> more capacitors type. The previous module was a switch mode power supply which somebody had bought off the shelf. While we are going with something along the lines of what I designed, but it is very helpful understanding more about the switching types of power supplies. Who knows maybe we will change our mind and I will make one of those. Thanks for the info! Usually I come to you for DIY synth stuff hah
Sir, your explanations are excellent and practical; thank-you. -Daniel
I've been looking for a while now for a clear top down approach of power supply basics exactly like this. Explained very well. I really like the approach, thank you!
Glad you liked it!
You have a gift of explaining complex stuff easy to understand for ordinary people like me who's interested in electronics. I hope you teach by profession because your really good. Anyway tnx to youtube and the net that ive seen your videos, keep it up master
th-cam.com/video/0bBMnXuXtLw/w-d-xo.html
You’ve done a great job simplifying switching power supplies something that I’ve been somewhat intimidated about
th-cam.com/video/LradbHTLVPY/w-d-xo.html
Thanks for the video, you explain the working of the components in a crystal clear manner, so even I get it, very helpful video 👍
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
This is very good explanation about SMPS that we all need. Thank you
World's best smps tutorial। Hats off 👍👍
Thank you sir for taking so much of pain to make us understand Switching PS. You made it so easy to follow of my used to be nightmare before watching your video. You instilled so much of CONFIDENCE in me to design one of my own. Really grateful to you Sir.
Hats off!!
th-cam.com/video/0bBMnXuXtLw/w-d-xo.html
Wow im 60 and had no idea how this worked. its very simple once you explained it. Thanks.
Very clear explanation on how SPS works. Thanks for sharing!
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
what a freaken lucid explanation...!!! well done man.
Very brief explanation and your English is quite easy to understand for me Indonesian. Well done sir. Thank you so much 👍🙂
Thank you so much. This is the best explanations that I ever saw.
Very good explanation, you make look so easy, thanks!
one of the best teacher on youtube
Step by step guide and explanation on how an eliminater works. I have a good number of adaptors, not functioning. I shall try to put them in order with your guidance. Thank you so much.
Wonderful talk. At the risk of sounding "to adult" :) I'd like to say I don't think many things in life are as Noble as passing your experience(s) forward to others. It [is] a form of immortality. I don't think we would have succeeded as a species without this one (very) important self-sacrificing attribute. You are a "good human" IMSA Guy. Live long and prosper. Cheers.
Great autopsy. Nuts and bolts eliminate "black box" go no go concept. Like knowing reason for the capacitor across winding of transformer. Y makes sense in that location. Although I still prefer linear supplies.Thanks for the look.
The world's best teacher thanks sir
The best explanation! Thank you.
great ! Thank you for help me out from darkness. I will try repair my computer supply once again after this vdo clip.
Excellent presentation!!!
Very nice explanation. Congratulations, Sir. 👍🙏
Thanks, master great lesson. Thanks a lot for the fine explanation.
Thanks bro. . For sharilng this video. Explained Very well. It's big help for me, As a beginner,
very useful for trouble shooting of power supply..
Great video! The Class Y capacitor is the correct choice for inter-transformer windings applications like the one you were looking at. X capacitors are used to prevent fires. Y capacitors are used to prevent shock. Y capacitors are more expensive, so it's common to see X capacitors where you need Y, but less common to see the reverse (unless the capacitor is rated for both, which is very common).
I enjoyed watching this. Thank you.
Excellent explanation 👌
Thanks for sharing. It's a valuable lesson
Thanks for this clear explanation..... I also like how you can simulate all electronic components by your fingers😁
Thanks for this tutorial. could you please explain how the voltage control feedback through the optocoupler actually controls the voltage. It seems to me that by slowing the switching, the frequency of the AC output would change, but surely the voltage is still a function of the ratio of the windings.
Best explanation I have come across. Thank you. You got a new sub.
explanations are excellent and practical ,Mérci monsieur
Thanks for good explanation.
Great! Clear explanation of what can be a complicated subject. However, you didn't mention how the controller ic gets its power. Thanks for the vid.
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
Thank you so much for explaining this, very easy to understand!
beautifully explained .thank you indeed
Thanks for sharing your knowledge Master
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
awesome walk-thru!
Thank you, very nicely explained.
Excellent!!! And the HP 32S... I had one... and a 45 before.
Thank you for your great videos. 👍
You are good teacher . thank you for lecture
Brilliant, educated me, thank you.
At kast I understand how a Switching Power Supply works - thank you.
Thank you my brother for sharing all this great knowledge really appreciate your work I have a SMPS that use to work from 100v to 240v AC but recently started working only at 240v can you please tell me what might be the problem why it's not working at 110v anymore thanks in advance.
Really clear explanation thanks
Thank you so much for sharing 🙏🙏🙏
You are the best, man!
Pointing each component on the board and explaining the function on your sheet, one of the best explanation of a switching power supply I've seen so far. Can you do the same on a more complicated power supply like a computer SMPS.
computer supplies can be very complicated and explaining how one works is probably only valid for that one design.
d '"drawing a schematic" part, pointing out d individual components, n basic explanation of d role/function of each component (optocoupler, zener diode, voltage divider, n so on) is excellent! thank you. GOD BLESS.
Nice explanation 👌
Hello, thank you for the great explanation, I have a question please, when I design a smps how can I define the output voltage and current?
Nice video, well done, thank you for sharing it with us :)
I love the video and explanation.
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
That was a good explanation.
Hi, well done instructional video although with small inaccuracies in the description of the voltage conversion on the transformer - it is not AC, but modulated DC (creating an AC inverter with a sine wave is difficult). Well, now to the question of why capacitors "X" are used somewhere and "Y" somewhere - it's for safety reasons - that's why the design is also different, these capacitors work mostly in high voltage circuits and if they fail, there could be damage, or unpleasant accidents. X and Y contain not only how the capacitor will behave in case of failure, but each of the types must meet different safety requirements - these are marked with a number after a letter - for example X1 or Y3:
The X-marked capacitor must be cut in case of fatal failure
Conversely, the capacitor marked Y must not be interrupted
There are also capacitors marked XY - they must meet the safety protocols of both classes.
Due to the different design, they also behave differently in the circuit, thanks to the design, capacitors X can be used as a voltage reducer in AC voltage circuits, where thanks to the capacitive reactance, the voltage will be reduced almost without the power limitation that would have to be taken into account when limiting the voltage using resistors .
Nice day 🙂 Tom
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
Thank you.. Simple explanation ❤️❤️❤️
That Y-capacitor is unlikely connected as in your schematic as it would make the EMI worse. It probably be connected from the secondary GND to primary GND instead. Connecting the ~2nF capacitor the way you drew will give quite a good shock to an unsuspecting user touching any part of the secondary side if the secondary GND is left floating.
The Y-cap is to isolate the primary from the secondary. Though, it has to connected such that one terminal to the Secondary GND and the other to the +ve primary.
Great video, thank You fo sharing.
Nice and good explanation!
Thanks!
thanks a lot for this video,god bless u bro
This is very complicated stuff. Thanks for trying to explain to me how it works
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
A big thanks, very interresting.
Thanks very much for the video. How I wish you can show the signals for each section on an oscilloscope.
This is great explanation about SMPS.
I’m come from Taiwan.
I just say the Y-Cap, it should be across between Pri. ground and Sec. ground.
The some noise from X’fmr will be closed loop thru Y-cap.
Maybe it can high voltage in pri. But we have to think about the stress on there.
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
Love the HP32S! I still have and use my 32SII from High School. LOL
A couple things that perhaps were already addressed in previous comments:
You used same symbol for two different sets of ground. There's a ground on the high voltage side, and a different ground on the low voltage side, which the two sides should not be tied together.
Also for the high voltage side, you're missing your ground source reference.
Thanks a lot Teacher.
Thank you sir... Although I remember having already subscribed, now it seems I've not, and thus I'm (re) subscribing... Great explanation skill.
VERY VERY THANK YOU 🙏🙏🙏
If you have AC line voltage it seems silly to rectify it first then turn it back to ac before stepping it down. Why not just step it down directly from the line voltage without the intermediate rectification? I know this is a 2 year old video so, probably won't get an answer, but I am curious. I 100% appreciate the way you just broke it all down and drew the circuit and explained every detail. Fascinating. You might just be my new favorite YT channel.
requires very large transformer. switching supplies are smaller and more efficient.
@@IMSAIGuyWhy do you need a larger transformer to make 12V AC out of 120V AC than making 16V pulse modulated DC out of 164 V pulse modulated DC? Also, why is the output of the rectifier 164V DC, when the input is 120V AC? Im just beginning to learn electronics, so please excuse my dumb questions... 😊
Great video, by the way - love your channel! Keep up the great work!!
@@fo76 The line voltage is 60 Hz. In this switch mode design the DC is switched at more than 1000 times that. Transformers at low frequencies require a lot of iron which makes them big and heavy. Even 50 Hz transformers are significantly bigger and heavier than their 60 Hz equivalents. That is one reason why aircraft use 400 Hz AC rather than 50/60 Hz.
@@fo76
They certainly are not dumb questions.
When no load is connected to a transformer the primary winding just looks like an inductor. With sinusoidal AC applied to the winding there will be magnetic field at the same frequency created. In an ideal inductor the voltage and current will be out of phase and the power will be zero, even if the current is high. But there is resistance in the primary winding, so you want to keep that current quite low so you don't waste power according to I²R in the resistance of the winding. That means you must make the inductive reactance quite large to make that "magnetizing current" quite small (the reactance of an inductor is 2 • pi • f • L, where f is the frequency in hertz and L is the inductance in henries and the reactance in ohms) At AC mains frequency (50 or 60 Hz, depending on where you live) that means you need quite a lot of inductance. That translates to lots of turns of wire and/or a large iron core. The inductance is proportional to the square of the number of turns.
When the secondary winding is connected to a load, current that is in phase with the primary voltage begins to flow in both the primary and secondary winding. The current in the secondary "cancels" the current in the primary, so there is no change in that magnetizing current we had before. But the primary and secondary currents are now determined by the load connected to the secondary and the turns ratio of primary to secondary. We have to use wire that is large enough to carry the current without getting too hot. It's hard to get the heat of the winding of a transformer, so the wire is much bigger than we'd use if it were just a single conductor in free air for the same current. We already knew how many turns we'd need, so now we more or less multiply that by the cross sectional area of wire to get the total cross sectional area of each of the windings. We have to be able to fit that into the area available in the "window" of the core. If we need lots of turns of heavy wire, we need a big core with a big window to be able to fit the windings. The bigger core MAY change the inductance of the primary, so we may use an iterative approach to arrive at the best combination of core, wire size and turns. Usually we check some published tables that give us a good starting point, though.
If you raise the frequency, you can get tolerable magnetizing current with far fewer turns of wire. That means you can use a smaller core.The core material must be different at high frequency because some energy is lost in the core material itself. "Hysteresis" and "eddy current" losses are the big players, but that's a topic unto itself. At line frequency "silicon steel" is the usual core material. For switch mode power supplies the usual core material is ferrite - a ceramic made mostly of iron oxide. There are many formulations of ferrites. Most companies that make ferrite cores will offer three or four that are suitable for switchers, each with somewhat different properties.
As for 164volts - AC line voltage is specified as RMS - Root Mean Square. If you divide a whole AC cycle into tiny time increments, take the instantaneous voltage in each of those intervals, square it, calculate the mean (average) of all those squares and take the square root of the mean you get the RMS voltage. AC mains is a sinewave. The peak (from zero) of a sine wave is 1.414 (square root of 2) times the RMS value of the sinewave. So 120 VAC gives you 120 x 1.414 = 170 at the peak. When there is no load, the input filter capacitors charge up to the peak voltage. (RMS is used because heating (power) in a resistor is equal to the RMS voltage squared divide by the resistance, just as with DC the power is the voltage squared divided by the resistance).
Thanks!!@@d614gakadoug9
You at least partially answered my question regarding that blue capacitor across primary and secondary windings. I have a power supply which has a significant AC signal on the secondary output side in the 60 Hz range. When I remove that strange blue capacitor with AC signal on the secondary disappears interestingly enough. So I remain a little baffled maybe you had more information regarding the so-called Y capacitor. Ethan
tkx master , so great you help me to understand lesson on school./.
great job
The description of the pulsed DC as AC is a bit of a misnomer that could be confusing as this pulsed DC has a DC bias, it does not change polarity or alternate. For this reason there are several aspects of the description that don't match AC power supply designs. For example, the windings on the transformer don't need to meet any 10:1 ratio like an AC stepdown transformer, although it often approximately does. The transformer is "charged up" when the switch is on and "discharged" when the switch is on. The transformer is not transforming current, when the switch is off the energy has no place to go but out the output diode and the voltage will rise to whatever value it needs to to exit the circuit. The windings do play a role in each side in determining the voltage when the switch is on (for the diode breakdown voltage) or when the diode is conducting (for the breakdown voltage of the mosfet switch).
And the name/topology of this type is "flyback".
Thanks A million!
very informative and nice video i want to add that the blue capacitor always attached between two grounds . in diagram you showed that the one leg is attached with the output of ic i hope you understand
They use a Y-capacitor instead of an X-capacitor between the primary and secondary windings for EMI reduction because if a Y-cap fails it fails as an open. X-caps fail as a short. So if you instead used an X-cap between the primary and secondary windings, a failure in the cap would short the high voltage side to the low voltage side (typically not a good thing).
Subbed!!! I LOVED!!... your explination, because most of the TH-camrs put out a poor explination, thank you sir.
Thanks for the sub!
It would be interesting to see the wave form at different points in the power supply I’m assuming the output would be like a pulsing square wave d c you see is that correct? Thanks
this is such a nice video...thank u thank u very much
A very accurate model to describe the TL431 is a non-inverting op amp with its negative lead connected to a 2.5V reference. Using two feedback resistors like you do for any non-inverting op amp, you can multiply the output voltage to create Vout = Vref * (1+ R2/R1) where Vref = 2.5V and R1/R2 are the two feedback resistors. The only difference is that the TL431 can only sink current; it cannot source it. Easy peasy! Rumor has it that the incorporation of the TL431 in the original Apple ][ switching power supply circuitry led to the TL431 being the world's most popular integrated circuit. Prior to the Apple ][, most personal computer power supplies were big bulky linears. The ]['s power supply was tiny and light in comparison.
th-cam.com/video/0bBMnXuXtLw/w-d-xo.html
Try a Bridgeless PFC converter followed by a Four-switch step-down storageless converter. Something from the 21st century. Or a VRM, 48V in 1.5V out at 200A.
it's an perfect explanation, thank you....
Doesn’t the blue capacitor you talk about in the end interfere with the isolation of the high and low voltage part?
At 16:41 when your DVM timed out my wife thought the microwave oven in our kitchen timed out . I took the video back and did we laugh :)
That is awesome!
Thank you for a clear explanation. Why does the frequency affect the output voltage? Why not just set a 555 timer to pulse @ 50Hz? I couldn't understand why the feedback is neccessary....
This circuit is called a "flyback converter." The name comes from a sort of similar circuit that is used to sweep the electron beam across a CRT, like a TV screen. When the beam gets to the end of its sweep of one line it "flies back" to the other side. If you look at the voltage waverforms those in flyback switcher are kind of similar and the circuit is similar, though the CRT circuit is concerned with making magnetic or electrostatic fields rather than generating voltage (in a TV it actually does both - manages the magnetic field to sweep the beam and generate the high voltage required to make the beam).
Anyway - with a flyback converter you aren't actually transforming voltage directly. Each cycle delivers a "packet" of energy. If the current requirement of the load increases and the packets are being delivered at a constant rate (frequency) then each packet must be made bigger to maintain the voltage across the load. The feedback circuit detects that the voltage at the output is not what it should be and commands the input side to adjust the size of the packets. If the voltage is too high, make the packets smaller. If it is too low, make them larger. This is "negative feedback." The are made larger or small by adjusting the amount of time the switch on the input side is ON - "pulse width modulation."
Feedback circuits also make sure that things like power losses (inefficiency) in the circuit are corrected for. The feedback circuit doesn't need to know what is causing the disturbance, only that it is happening and a change must be made in the appropriate direction to correct for it. It's like controlling the speed of a car with the gas pedal. You don't really need to know if you are fighting a headwind, or going up hill, all you know is that you need to push the pedal down so your speed is maintained. Feedback also corrects for variation in the input voltage.
Sos un capo. Explicas muy bien. You are really good at teaching. Nuevo suscriptor. New subscriber.
gracias
Great! Thank you so much!
i can say u r great helper
God Save And Bless You
Always wanted to know the use of the BLUE CAPACITOR! Thx
Hi, friend. Watch my video!
th-cam.com/video/2Qr6Jcm8wbA/w-d-xo.html
Fantastic video. If one were to build their own version of this, when sourcing the transformer, what things should one look for? We know it needs to handle a certain amount of current and that it needs a 10:1 ratio to step down, but are there any other things to look for?
The data sheet has a nice little blurb on designing the power transformer. I found it useful
love it.