#772

[@jj74qformerlyjailbreak3]

This channel could never get enough credit for all the work you’ve done here on YT. Best switcher video I’ve seen. Thanks

[@Leo-pd8ww]

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!

[@IMSAIGuy]

Glad you liked it!

[@bobkozlarekwa2sqq59]

You’ve done a great job simplifying switching power supplies something that I’ve been somewhat intimidated about

[@eevibessite]

kzbin.info/www/bejne/gqPElZV-ibGJhrs

[@irgski]

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.

[@lem0121]

Good input! Just randomly came across this video and thought it would be a good refresher for me. A few questions that I didn't see answered in the video that maybe you can help. 1 - I was especially hoping to see more about the grounds. You mention to never connect dc side and ac grounds together. In the schematic shown in the video, the dc output has a floating ground reference. Couldn't this cause issues when connecting to devices that are earth referenced? What's the proper strategy around having an earth-referenced ground output on the dc side? 2 - Galvanic action due to two dissimilar metals being in contact with each other, correct? Is that really what it's protecting against? I've seen this mentioned before, and I have always wondered why it is actually called galvanic?

[@j.fanning8158]

I think you did an excellent tutorial of this version of a Switched Mode Power Supply ! Thanks for taking the time to help others to better understand how it works.

[@robinmidgett7134]

Excellent tutorial on SMPS, thank you. The blue cap across the transformer is seen as a short circuit path to ground for VHF frequencies generated by the switching action of the DK1203. The DK1203 is an on/off switch with a fast switching speed, therefore it generates lots of VHF spikes / harmonics, which would lead to undesirable RFI; the cap gives a path to ground (snubbed) for those VHF components. Recall that Xc is the inverse of 2 π FC, so as frequency goes up, the impedance seen by those frequencies goes down...hence the VHF energy is shunted to ground while the lower frequency energy is kept in the transformer primary.

[@ovalwingnut]

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.

[@emelitoduran1571]

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

[@eevibessite]

kzbin.info/www/bejne/ZpOlfqGOqr2ngtk

[@72chargerse72]

Wow im 60 and had no idea how this worked. its very simple once you explained it. Thanks.

[@tze-ven]

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.

[@Deno-technologies3081]

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.

[@davidmiller8618]

Your videos are excellent! Great content, explained masterfully. A pleasure to watch.

[@Edisson.]

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

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@brahimtoumi4368]

i have just found your channel and judging from the videos I saw so far you sir are a good explainer. thank you mr

[@Qooooo8964]

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.

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@medatrium6714]

There is a misrepresentation about the "AC" at the transformer. By definition, AC stands for Alternating Current. After the rectifier, the current is DC all the way. The transformer in this case has DC on the high voltage side. Because of the switching, the current running through the high voltage side changes all the time. This change of current drives the transformer and produces current on the low voltage side.

[@RodHartzell]

Thank you. That confused me. I think it makes sense the way you explained it.

[@michaelkeymont501]

It IS alternating current at the transformer. It changes between 2 definite values, ramping up and down due to the time constant of the inductance of the transformer. It may be caused by the switching, but it is alternating current nonetheless. If it weren’t AC, the transformer wouldn’t be doing anything because there would be no change in the magnetic field.

[@coledavidson5630]

A voltage that is changing periodically is AC. It doesn't really matter if it's a square or sine wave

[@mschwage]

@@michaelkeymont501 isn't it pulsating dc? A transformer only takes a change in electric field; it doesn't have to reverse. But the definition of AC means that it goes both positive and negative.

[@michaelkeymont501]

@@mschwage it’s chopped DC - when the DC gets chopped from full on to full off, it a voltage is induced in the coil and the result is a current that goes positive and negative about a virtual ground. “Negative” because the direction of current flow reverses when the DC is turned off, because the collapsing magnetic field is trying to oppose the instantaneous change. The current goes positive while DC is on and negative when it is off, hence alternating current. That’s also the reason that you need a snubber diode across the coil. If it weren’t there, that opposite polarity current would fry the switching circuit because it’s initially a very high voltage spike in the wrong direction. When I worked in failure analysis for a power supply company, we used to see that voltage spike get out of control - literally - if the adhesive in the potted transformers started to fail. As the air gap changed the characteristics of the transformer, they would get extremely hot and burn up from the voltage spikes blowing out the snubber diode and taking out the MOSFET in a magnificent puff of smoke.

[@amigo4558]

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.

[@TheSixth1]

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).

[@argcargv]

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 <a href="#" class="seekto" data-time="601">10:1</a> 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).

[@paulcohen1555]

And the name/topology of this type is "flyback".

[@danpedersen5816]

Thanks for the video, you explain the working of the components in a crystal clear manner, so even I get it, very helpful video 👍

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@ronjon7942]

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.

[@milkaimwaga-ju7gh]

The best explanation for smps I have ever heard! I had to subscribe ❤❤❤

[@tinkerpertao8383]

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.

[@grounded9623]

Sir, your explanations are excellent and practical; thank-you. -Daniel

[@anandawijesinghe6298]

The 'old' conventional approach delivered unregulated 12vdc output with 10-fold step down transformer to first get approximately 12 vac, a rectifier to convert that ac to dc, and a ripple filter to smooth the dc output, and a 3 wire linear regulator to stabilize the dc voltge output. Can you explain 1. How this smps circuit delivers a regulated dc output, and 2. How the smps approach reduces the cost and size of the unit compared to the 'old' conventional approach? The cost and size advantage is central to the near universal use of the smps approach for PC power supplies.

[@IMSAIGuy]

1. I explain that in the video, feedback is through opto-coupler 2. size is due to low current. old has high current in transformer, new has low current. by using a high voltage you only need low current for the same power.

[@SonnetGomes]

Wow. This is so simplified and easy to understand. Thank you so much for posting this informative video.

[@L2.Lagrange]

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

[@RodHartzell]

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.

[@IMSAIGuy]

requires very large transformer. switching supplies are smaller and more efficient.

[@fo76]

@@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!!

[@jvk-pj8jr]

@@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.

[@d614gakadoug9]

@@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).

[@wims58ej]

Thanks!!@@d614gakadoug9

[@handyertanto76]

Very brief explanation and your English is quite easy to understand for me Indonesian. Well done sir. Thank you so much 👍🙂

[@demef758]

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.

[@eevibessite]

kzbin.info/www/bejne/ZpOlfqGOqr2ngtk

[@shinningraj]

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!!

[@eevibessite]

kzbin.info/www/bejne/ZpOlfqGOqr2ngtk

[@ahmedgaafar5369]

what a freaken lucid explanation...!!! well done man.

[@guitchess]

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.

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@forhadahmed4643]

one of the best teacher on youtube

[@ponymoore6140]

At kast I understand how a Switching Power Supply works - thank you.

[@martym2464]

Thanks for this clear explanation..... I also like how you can simulate all electronic components by your fingers😁

[@ats89117]

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).

[@thanatosor]

Someone need to help this guy to film & edit the video, because heck did a great job & we don't want him to be distracted 😂

[@milenkovasic9070]

very interesting way of explaining, you draw a diagram and then keep it covered with your hands the whole time!

[@kabandajamir9844]

The world's best teacher thanks sir

[@johndale7760]

Nice vid, and very clear and helpful commentary. It would have been useful to briefly mention "why use a SM PS?" The answer being that the size and weight - especially of the transformer - is much reduced, and that this is made possible by the AC frequency at the transformer being much higher than the 50/60 Hz of the mains. The downside (as you mentioned) is that this higher frequency gets emitted as interference to nearby electronics, even when quietened down by on board capacitors. Loved the use of a simple design to demonstrate the principle. The more complex SM PS are often difficult to fault-find and repair.

[@adrianjanssen7489]

My sense for the capacitor across the 2 sides of the transformer is that it changes the defacto capacitance to a different value and thereby changes what signal frequencies are transmitted?

[@IMSAIGuy]

no, it provides a high frequency path back to the other ground to kill emission spikes

[@adrianjanssen7489]

@@IMSAIGuy ah, cool thanks

[@ihorpol8431]

Thank you so much. This is the best explanations that I ever saw.

[@pipatp1288]

great ! Thank you for help me out from darkness. I will try repair my computer supply once again after this vdo clip.

[@garysmith9772]

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

[@homeralbufera7068]

Very clear explanation on how SPS works. Thanks for sharing!

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@Greebstreebling]

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....

[@d614gakadoug9]

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.

[@wfenwick]

It's good but you should pin down the board to a breadboard or block of wood or something, when probing for safety's sake.

[@rad2304]

Thanks very much for the video. How I wish you can show the signals for each section on an oscilloscope.

[@3d8d]

World's best smps tutorial। Hats off 👍👍

[@0bandwidth]

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

[@manueladao8653]

I think the showed Y blue capacitor (min <a href="#" class="seekto" data-time="1392">23:12</a>), must be connected between both ground (-). See in 15.21 the final diagram.

[@styzr]

Best explanation I have come across. Thank you. You got a new sub.

[@blas2437]

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..

[@egbertgroot2737]

Always wanted to know the use of the BLUE CAPACITOR! Thx

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@miguelbarella1173]

Excellent!!! And the HP 32S... I had one... and a 45 before.

[@4thesakeofitname]

Thank you sir... Although I remember having already subscribed, now it seems I've not, and thus I'm (re) subscribing... Great explanation skill.

[@ethanclement9647]

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

[@sliverknight2194]

You are good teacher . thank you for lecture

[@ALIQudsi-j5i]

thanks for fantastic job , just wondering if you could tell me about transformer wire size the primery and secondary or if possible to make a video about how to make step down /up transfarmer . many thanks

[@MKINDYR107]

I enjoyed the video and followed it through your logical steps. I like the addition of the TL431 for the dc o/p feedback and the pot to adjust the final output. 1 Question : why is the -12V not connected to ground (or 0V line)?

[@IMSAIGuy]

the design would have be different to use a single supply, the -V allows the op-amp to operate correctly around zero

[@CNoteZzz]

Subbed!!! I LOVED!!... your explination, because most of the KZbinrs put out a poor explination, thank you sir.

[@IMSAIGuy]

Thanks for the sub!

[@ekanugraha7024]

This is very good explanation about SMPS that we all need. Thank you

[@Power_DC_Official]

Great video! Any suggestions on building a 12V 35A PSU from this design?

[@IMSAIGuy]

it would be awful. 35A needs better

[@eliasgeorge8534]

Love the HP32S! I still have and use my 32SII from High School. LOL

[@YTspeurder]

Does that mean that when the optocoupler led stops working, that the output will go overvoltage and possibly break your connected device?

[@danman32]

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.

[@danielwhite5705]

Need help here! I just wanted to know how to power up any ferrite transformer with 220v ac 50kHz. What can amplify the frequency?

[@IMSAIGuy]

the 50khz would be generated by the controller IC. in this case DK1203

[@danielwhite5705]

@@IMSAIGuy is there a need for a MOSFET?

[@danielwhite5705]

@@IMSAIGuy lemme see if I got it right : First I need a rectifier bridge and a capacitor to convert 220 ac to DC then for the tapping work I need the DK1203 you've mentioned then I can connect to the primary ferrite core coil.

[@IMSAIGuy]

@@danielwhite5705 just buy one, it is cheaper, this was $7

[@IMSAIGuy]

this control chip has a built in FET, higher current designs need an external one.

[@RichardGirou]

In your schematic, you have a resistor that ends nowhere, in the lower right corner. It is in the monitoring circuit I believe.

[@IMSAIGuy]

it is marked +12, it connects to the 12v

[@JohnPooley-te9ei]

Nice1 Imsai & thank u

[@優さん-n7m]

I did not understand the snubber circuit thing you mentioned about the capacitor in series with the resistor

[@plamenpetkov7132]

secondary rectifier GND is to be linked to TL431

[@wessss]

So if you omit the rectifier, flip the transformer, swap out the output capacitors, and retune the voltage divider, you could use it as a 10x dc boost converter right?

[@IMSAIGuy]

not with the parts shown.

[@geraldelwood9660]

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.

[@craxd1]

If I had my bet, the idea came from the military, mainly the Air Force, using 400 Hz inverters, and noticing how the transformer's core was smaller due to the higher switching frequency. Frequency directly affects the core's size.

[@toddanonymous5295]

At <a href="#" class="seekto" data-time="1001">16:41</a> 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 :)

[@IMSAIGuy]

That is awesome!

[@cdray1968]

Thank you so much for explaining this, very easy to understand!

[@u9Nails]

When you draw a connection to ground, they tend to go to a magical place. That is, in my mind at least! Since I'm looking at a schematic magical map with a "portal" which connects an upside-down triangle to somewhere else in physical space. Let's look at the power LED for example, is the ground wire connected to the 12V DC -? That seems logical to me. But here's a bonus question. There isn't a "ground" on the AC side right? The DK1203 has a ground on pin 5. So, would that also connecting to 12V DC -?

[@d614gakadoug9]

A "Y1" capacitor is used between the input and output side as a local return path for high frequency noise. Noise coupled through the transformer to the secondary side goes back to the primary side in a short loop instead of radiating from anything connect to the secondary and acting as an antenna. This capacitor is in a very critical position with regard to safety. If it were to fail short-circuit it would create a potentially lethal electric shock hazard - the entire secondary would have to be regarded as connected directly to AC mains. Y1 capacitors are essentially two capacitors in series - the equivalent of "double insulated" structure. Their nominal voltage rating is according to the AC mains voltage for which they are intended but the actual breakdown voltage is very much higher than that - several kilovolts. The probability of a short-circuit failure is extremely low. X capacitors are designed so as not to catch fire if they fail short-circuit - they "self heal" to clear the fault by burning away the foil in the area where the short occurs. This could be disastrous if used where a Y cap should be since the fault would persist until sufficient current could be passed, mean a potentially lethal shock hazard would be there until someone or something got fried.

[@RG-ve8io]

what about the design calculations or values for turns of the isolation transformer?? how is it calculated ? how is transformer turns ratio decided for this circuit?

[@TheGazza83]

This is very complicated stuff. Thanks for trying to explain to me how it works

[@Den_Electro]

Hi, friend. Watch my video! kzbin.info/www/bejne/aILVZ32Zop2qmKM

[@Martinko_Pcik]

I guess this could be modified to a MPPT solar panel power source for a water heater. Just the feedback loop would be a bit more complex and involve a microprocessor to balance the right load for light conditions. Cool. I learned something

[@fijabo]

Doen"t the Y capacitor defeat the input-output isolation? I wonder if the Y capacitor can cause a shock sensation to someone touching the output and a grounded part.

[@k.pathirana.8868]

Very nice explanation. Congratulations, Sir. 👍🙏

[@sakhankek6324]

Thanks for good explanation.

[@erikvincent5846]

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 <a href="#" class="seekto" data-time="601">10:1</a> ratio to step down, but are there any other things to look for?

[@theoldbigmoose]

The data sheet has a nice little blurb on designing the power transformer. I found it useful

[@osmancanbaz7312]

Thanks from Türkiye

[@robertpearson8546]

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.

[@RichChh]

I enjoyed watching this. Thank you.

[@EJEuth]

Sometimes with TL431 as the Voltage Sensor, optocoupler has a resistor (like 1K) in parallel with the LED, to avoid it being lit by the quiescent current of the TL431.

[@richardsardini5585]

Just curious, with the blue capacitor jumping the coils, doesn't that end our circuit isolation? We now have a physical connection from one side to the other.

[@IMSAIGuy]

only at high frequencies

[@richardsardini5585]

@@IMSAIGuy Right, but what if the component short circuits? Wouldn't frequency no longer be an issue? After all, isolation was always about protecting against component failure, Right? Again, I am just curious.

[@IMSAIGuy]

well if the transformer shorted what would be bad news, if the capacitor shorts you just connect input ground to output ground and the output is low voltage DC anyway. so not too bad

[@shaskhim]

Hello there and thanks for so useful video... I have a problem with my power supply and there is no DC voltage on the rectifier (nor on the main capacitor) What should i do to fix the problem?

[@IMSAIGuy]

could be many things wrong. I can't help you. check the fuse

[@shaskhim]

Thanks for reply. I checked the fuse and just replaced the rectifier bridge (it was GBP310 and i replaced with KBP410 (what i had at home). Also checked the input AC and it's OK. I don't know what is the problem. It may be a lose connection on the board or something like that.@@IMSAIGuy

[@fijabo]

Thank you for your great videos. 👍

[@MrFiveStarzz]

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.

[@ytrew9717]

Where is your playlist "ac to dc converter" ? (Please add it in the description)

[@JohnyRalte]

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.

[@IMSAIGuy]

computer supplies can be very complicated and explaining how one works is probably only valid for that one design.

[@takoroto8809]

explanations are excellent and practical ,Mérci monsieur

[@hugobarbosa7753]

Bridge rect direct to AC? WHOA! -Can I do that with those 1 piece units??

[@IMSAIGuy]

yes if it has the correct voltage rating

[@ivanclaros7878]

Sos un capo. Explicas muy bien. You are really good at teaching. Nuevo suscriptor. New subscriber.

[@IMSAIGuy]

gracias

[@TeshomeTessema-m4m]

Excellent presentation!!!

[@geirha75]

Very good explanation... I still have a general question, why AC -> DC -> AC -> DC ( 12 V ). Old fashion way: AC -> DC

[@IMSAIGuy]

requires very large transformer. switching supplies are smaller and more efficient.