#772

Рет қаралды 406,193

3 жыл бұрын

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...
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@irgski Жыл бұрын

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.

@awm0121 9 күн бұрын

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?

@Leo-pd8ww 3 жыл бұрын

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 3 жыл бұрын

Glad you liked it!

@jj74qformerlyjailbreak3 10 ай бұрын

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

@bobkozlarekwa2sqq59 3 жыл бұрын

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

@eevibessite 5 ай бұрын

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@ovalwingnut 2 жыл бұрын

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.

@davidmiller8618 Жыл бұрын

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

@ronjon7942 Жыл бұрын

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.

@grounded9623 Жыл бұрын

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

@L2.Lagrange Жыл бұрын

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

@danpedersen5816 Жыл бұрын

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 Жыл бұрын

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@ekanugraha7024 Жыл бұрын

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

@ahmedgaafar5369 Жыл бұрын

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

@tze-ven Жыл бұрын

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 2 ай бұрын

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.

@3d8d Жыл бұрын

World's best smps tutorial। Hats off 👍👍

@homeralbufera7068 Жыл бұрын

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

@Den_Electro Жыл бұрын

Hi, friend. Watch my video! kzfaq.info/get/bejne/aLeiaa2U0p7bknU.html

@emelitoduran1571 Жыл бұрын

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 5 ай бұрын

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@JohnPooley-te9ei 8 күн бұрын

Nice1 Imsai & thank u

@JulioMartinez-eh2fw Жыл бұрын

Very good explanation, you make look so easy, thanks!

@72chargerse72 6 ай бұрын

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

@shinningraj 10 ай бұрын

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 5 ай бұрын

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@cdray1968 8 ай бұрын

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

@ihorpol8431 7 ай бұрын

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

@handyertanto76 Жыл бұрын

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

@Edisson. Жыл бұрын

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 Жыл бұрын

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@tinkerpertao8383 Жыл бұрын

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.

@styzr 8 ай бұрын

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

@k.pathirana.8868 Жыл бұрын

Very nice explanation. Congratulations, Sir. 👍🙏

@amigo4558 6 ай бұрын

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.

@kabandajamir9844 Жыл бұрын

The world's best teacher thanks sir

@RichChh Жыл бұрын

I enjoyed watching this. Thank you.

@RodHartzell 11 ай бұрын

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 11 ай бұрын

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

@fo76 10 ай бұрын

@@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 10 ай бұрын

@@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 9 ай бұрын

@@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 6 ай бұрын

Thanks!!@@d614gakadoug9

@GiC7 2 ай бұрын

Thanks, master great lesson. Thanks a lot for the fine explanation.

@nlimchua 6 ай бұрын

awesome walk-thru!

@jdmccorful 3 жыл бұрын

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.

@pipatp1288 Жыл бұрын

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

@forhadahmed4643 Жыл бұрын

one of the best teacher on youtube

@MrFiveStarzz 2 жыл бұрын

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.

@argcargv 3 жыл бұрын

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).

@paulcohen1555 3 жыл бұрын

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

$@fractal_logic$

@fractal_logic Жыл бұрын

The best explanation! Thank you.

@user-de7mq1ox4b 5 ай бұрын

Excellent presentation!!!

@ponymoore6140 7 ай бұрын

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

@blas2437 Жыл бұрын

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..

@futurederrick 5 ай бұрын

Thanks for sharing. It's a valuable lesson

@Bianchi77 9 ай бұрын

Nice video, well done, thank you for sharing it with us :)

@martym2464 9 ай бұрын

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

@guitchess 2 жыл бұрын

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 Жыл бұрын

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@dr0mtm Жыл бұрын

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?

@miguelbarella1173 Жыл бұрын

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

@fijabo 6 ай бұрын

Thank you for your great videos. 👍

@takoroto8809 Жыл бұрын

explanations are excellent and practical ,Mérci monsieur

@sakhankek6324 Жыл бұрын

Thanks for good explanation.

@BS11155 2 жыл бұрын

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 Жыл бұрын

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@ajitmohanty1684 2 жыл бұрын

Thank you, very nicely explained.

@lupojacobo9892 2 жыл бұрын

Thanks for sharing your knowledge Master

@Den_Electro Жыл бұрын

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@simpleelectronics7863 Жыл бұрын

Excellent explanation 👌

@danman32 2 ай бұрын

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.

@sliverknight2194 6 ай бұрын

You are good teacher . thank you for lecture

@grahamhall2662 Жыл бұрын

Brilliant, educated me, thank you.

@JohnyRalte Жыл бұрын

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 Жыл бұрын

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

@sterrname5824 Жыл бұрын

Great video, thank You fo sharing.

@demef758 Жыл бұрын

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 5 ай бұрын

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@jgabrito 9 ай бұрын

You are the best, man!

@soroushzarein3246 Жыл бұрын

beautifully explained .thank you indeed

@stuartgoldsmith2310 4 ай бұрын

Really clear explanation thanks

@Electronzap Жыл бұрын

That was a good explanation.

@4thesakeofitname 7 ай бұрын

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

@TheGazza83 Жыл бұрын

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

@Den_Electro Жыл бұрын

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@bobdoritique7347 Жыл бұрын

A big thanks, very interresting.

@sreejithshankark2012 Жыл бұрын

Thank you.. Simple explanation ❤️❤️❤️

@garysmith9772 Жыл бұрын

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

@ethanclement9647 Жыл бұрын

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

@eliasgeorge8534 Жыл бұрын

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

@jbrown468 2 жыл бұрын

I love the video and explanation.

@Den_Electro Жыл бұрын

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@felyguinabo2422 Жыл бұрын

Nice and good explanation!

@IMSAIGuy Жыл бұрын

Thanks!

@kingshahzad78 21 күн бұрын

Best Explanation❤

@mariohruby Жыл бұрын

Nice explanation 👌

@MoslimMahmood 10 ай бұрын

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

@IMSAIGuy 10 ай бұрын

Thanks for the sub!

@erikvincent5846 Жыл бұрын

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?

@theoldbigmoose Жыл бұрын

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

@aunglatthakha2386 Жыл бұрын

Thank you so much for sharing 🙏🙏🙏

@user-tb1ze7ds5m 3 ай бұрын

thanks a lot for this video,god bless u bro

@user-wu3qm7kt6o 5 ай бұрын

Thanks a lot Teacher.

@0bandwidth 10 ай бұрын

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

@gdvissch Жыл бұрын

Doesn’t the blue capacitor you talk about in the end interfere with the isolation of the high and low voltage part?

@daisychs2664 Жыл бұрын

this is such a nice video...thank u thank u very much

@YTspeurder Жыл бұрын

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

@geraldelwood9660 10 ай бұрын

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.

@ashirnvd5 4 ай бұрын

great job

@jamess7636 3 ай бұрын

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).

@anhhongtran2337 Жыл бұрын

tkx master , so great you help me to understand lesson on school./.

@ivanclaros7878 11 ай бұрын

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

@IMSAIGuy 11 ай бұрын

gracias

@ats89117 3 жыл бұрын

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).

@toddanonymous5295 3 жыл бұрын

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 :)

@IMSAIGuy 3 жыл бұрын

That is awesome!

@robertpearson8546 Ай бұрын

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.

@pbs570 10 ай бұрын

Thanks A million!

@egbertgroot2737 3 жыл бұрын

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

@Den_Electro Жыл бұрын

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@Onkel.Moetrik Жыл бұрын

Hi, great video. Can you explain this to me? Why is one single rectify diode on the switched ac enough, when a full bridged rectifier is used on the mains ac? Thanks Claus

@IMSAIGuy Жыл бұрын

it is rectifying pulsed DC not true AC

@rogergreenwood1536 3 жыл бұрын

Do they operate on different switching frequencies or are they all pretty similar? I also note that on a 240V supply the rectified voltage will be around 330V which would not be pleasant to touch :-)

@IMSAIGuy 3 жыл бұрын

they all use different frequencies. Yes these things are very dangerous the voltages are high and the capacitors will hold that voltage.

@EJEuth Жыл бұрын

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.

@MKINDYR107 6 ай бұрын

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 6 ай бұрын

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