Ferrite transformer calculations for SMPS

[@peep39]

This is excellent and is very educational to someone just learning SMPS theory. Thank you for taking the time to make this video

[@maheendrannair9557]

Sir you have given each and every minute aspect of design of SMPS ferrite transformer. I have seen many tutorials in this regard but this is the most exhaustive explanation ever I seen.Thank you very much.

[@AntonioBdeJesus]

Thank you very much Mr. Silvio de Leonardo, thatś a huge help. I have have some dificulties with the formulas but you made it quite easy to understand. Keep doing the good job ...

[@chbonnici]

Very good explanation "Prosit" people like you make a difference. Thank you.

[@BBC1ish]

Excellent informative and practical break down of the design procedure, thank you.

[@hamidsaberi8472]

sir explaination is very good and nice. speaking in english is easy to understand for me thank you very much.

[@hervefaro4450]

Excellent tutorial.I think that it will be of great value to students and technicians.Thanks.

[@amardeepsvirdi]

Excellent video with crystal clear explanation of each concept at different stages of winding. Thanks...

[@genetecnica.]

OLÁ SILVIO !!! É MUITO FÁCIL DE ENTENDER SUAS EXPLICAÇÕES , POIS TUDO É ESCLARECIDO COM RICOS DETALHES , SEM NADA OMITIR .. MEUS PARABÉNS , E CONTINUE SEMPRE ASSIM !!!

[@triao6598]

I've learned many things after your videos, thank you so much!

[@sundiesel1232]

Thank you for your excellent explanation. I am sure that it will certainly be of great deal of help to many as it is to me.

[@darren70215]

Thank you very much Silvio De Leonardo. This is the best video on youtbe. so very good explanation. and English is very very good. well done. Thank you. :)

[@lesstime1678]

you are so good on formulas,very good video very smart men,i love these type things.

[@yoramstein]

Great video. A good reminder. Silvio you promised to leave a link to the copper wire chart but forgot to do so.

[@supersilve]

I gave the link on top of the comments. You can stop the video on 32:17 and copy it from there.

[@jaideep6968]

Very Nice Video. Was looking for something like this for a long time.

[@ajithkumar-ff8ey]

Leonardo,this tutorial helped me much..thank you

[@sparkyy0007]

Thank you for uploading this, very helpful.

[@ministeriomundialliberando8403]

Thank you, very important information. You can also convert from meter to feet directly uisng this: 1m x 3.28feet/m=3.28feet.

[@abdultairu]

This is very informative and the author left nothing out. Thanks.

[@hadighaemipoor6354]

Tank you very very goood i need underestand this work and you very good teacher

[@eamonhannon1103]

Very good video . There is one thing missing . How to select the magnetic core ? It would be good to add a video covering this topic .

[@keithmaddox1469]

Love it. Thanks for the video.

[@Kapalek84]

Very nice explanation. Thank you for sharing.

[@supersilve]

Glad it was helpful!

[@eamonhannon1103]

Very good video . Thank you .

[@esoterex]

The feedback to the opto must NEVER be taken after the second LC filter. Supply can become unstable due to the extra phase shift.

[@justingreen8006]

Great video with very clear explanation. I subscribed and hope you will create more videos. :-)

[@jimis04]

MR Silvio please reupload the actual winding video of this transformer! I think you deleted it. It was so informative and its rare to find a real handmade tutorial for ferrite tranformers like the procedure that was this video described! Thank you

[@supersilve]

I will upload a better one in the future

[@jimis04]

i hope you do, this video was your first video i watched from your channel and i think was the motive for most of your suscribers! i was ready to try to build a coil winder with counter like the one you did! Anyway.Keep up the good work!

[@lakmalidarshani1179]

Thanks sir I understand very well . thak you very much your lesson. bye

[@AnirbanKarmakar108]

Thanks for the video. Very helpful.

[@anlpereira]

Great video. For a flyback topology in the primary turns calculation I should use 310V instead of 155V of the half bridge? Thank you very much.

[@supersilve]

Yes you can.

[@audiokees4045]

Hi There. I was some busy with the smps, I have decided to use resonant version, one with current feedback so I have fast respons and still stability. Did go to 10 amps 65 x 65 who is more then enough, the smsps can do easely the music peaks who live short, and I do never play so loud, ears will be give up earlyer then the suppy. For the tubes a 100 watt (overkill) LCC resonant can do, (also for audio better) these can run very nicely also without a load, burst mode for llc is not what I want, the ripple get bad and I need clean amp because it is high end class hybrid. The question now, LCC resonance do need a transformer calculation, and in all papers she just talk about N this is coupled with tank calculations, never I see how high induction will be only AC who is the load max and min. I presume the smps transformer needs to have these reactante with max and min load valeu? I do not now if you did resonance stuff, for LLC I do have tools and can calculate for LCC not because it is a older system, but it is used for led,s because of the nice respons for that. regards

[@ibrahimcafe9586]

Thank you very much sir

[@mudugulababu8517]

Tq for putting explaining

[@supersilve]

Welcome 😊

[@VanVihari]

Content quality is too good, but could you please make a video little clear and with pen or sketch?

[@etce_09_dharanikumar50]

Thank you sir for your sharing of knowledge to all. I read all the public comment of this video. But I have a question that why we can't use the laminated iron core for high frequency? Thank you

[@supersilve]

A laminated core is not suitable for high frequency it only can handle up to 400Hz.

[@etce_09_dharanikumar50]

@@supersilve Thank you sir

[@kymostken]

great demonstration friend

[@mohammadmoezi3813]

hi sir..thankyou for make this video..sir at your video you writ turn=58mm. how you do calculate this number please if you can describe it ...thankyou sir

[@muralibissannagari]

Thank you very much for clear calculations. ....may i have one of your publication about this caluculations....thanks.

[@vrssrv12]

Very useful to us Sir ..

[@naeemkhan-ii8tx]

very nice sir

[@freeenergy8713]

Hello Friend, I congratulate you on the video, I have a question, how to calculate the power of the ferrite transformer with square or circular core, thank you

[@nosafetyswitch9378]

Very good job!

[@G.Rengarajan]

Excellent tutorial.

[@supersilve]

Glad you liked it!

[@prasanth.m6220]

Super sir thank you so much

[@ifnzutech]

Thanx for your timely response, but let me ask you weather to do primary culculation first and then do secondry or to do secondary first and then primary for inverter chopper.

[@supersilve]

Usually inverters have a push pull topology for the primary as this is driven by low voltage, This will incorporate 2 primary windings one in series with the other. According to the number of turns in the primary then a simple sum will get the number of turns in the secondary. Let us say you have 4v per turn then it will become quite easy to figure out.

[@ifnzutech]

@@supersilve Sir.If i use AWG25*4 wire use what will be the frequency in calculation?Please explain i appreciate your channel it solve most of our problems. tnx

[@supersilve]

@@ifnzutech As I explained in the Video every diameter of wire has its maximum frequency of operation due to skin depth of the current. A shot at the chart can be found at 31:59. You can see that the maximum operation frequency for 25 AWG wire is 85Khz.

[@supersilve]

For invertor chopper it is best to wind the primary first as this can be put more easily on the flat bobbin surface. The secondary may consist of multiple wires and the winding may not be so flat.

[@ifnzutech]

@@supersilve Thanks sir for the quick reply my question is that if i use AWG 25×4 mean AWG 25 four wire it's frequency will b 85Khz or 85khz × 4 = 345 khz and when I'll calculate it i use 85khz or 345khz.

[@faidularcs]

Thankyou very much for helpful email 💝

[@monolito8556]

Excellent video . Can you make a similar for ferrite toroidal? . Excellent job once again

[@supersilve]

It is the same formula. You have to find the cross sectional area of the ring core. Outside diameter less inside diameter. Divide by 2 and multiply by the height.

[@piyushbanerjee2471]

Thank you for this really good video on transformer winding calculations. I was just wondering whether the auxiliary coil layer would be wound after the first half of the primary is wound OR after the secondary layer?

[@supersilve]

Aux windings are not so important and can be wound after the main secondary before the last half of the primary

[@piyushbanerjee2471]

Silvio De Leonardo Thanks man! 👍

[@mohammadhashemi1771]

Nice work, you seem to know about coils. I am working on a generator and need help with choosing and winding the right coils for the machine would you help?

[@kabandajamilu9036]

So educative

[@supersilve]

Thank you

[@rajehsaassouh1154]

thank you so much for this video.

[@AbdulRahman-en3ow]

if i am using ee55 ferrite transformer at 100khz frequency and b max i think would be around 900 than what should be the volt per turn? thanks

[@jbgaming6283]

thanks a lot sir.

[@Diego4322237]

Muchas gracias amigo! me ayudó mucho.

[@NiceTech22]

great video. How can I calculate the size of the transformer core for the given power that is 120watt?

[@skylineofsu9791]

Thank you so much

[@630NESS]

How you can get 350W with 33Khz? i undertand that at higher frequency, more power can be transferred from primary to secondary

[@audiokees4045]

at higher frequency you need less windings, and can use smaller transformer. you can even get 350 watts or more with 10 Khz. Does not matter much, just parts need fit like transformer material and inducttion.

[@zagyify]

Mr. Silvio, thanks for this video that simplifies HF ferrite transformer practical design. I have tried to understand it from different books, but this way, I have learned more from your video in about half of hour, than in couple of days by reading different books. Unfortunately, there is no more this kind videos from you. Can you please explain how to calculate a flyback transformer? I need to design 12V to 300V converter for capacitor charger but I am a little confused about flyback transformer design. Thanks in advance and please try to find more time to make this like videos. Regards.

[@supersilve]

The formula used here is only suitable for Full bridge, half bridge and push pull design. It is not suitable for flyback design

[@1959Berre]

To disassemble a transformer safely heat it up in boiling water for about 5 to 10 minutes, depending on its size.

[@supersilve]

It will not always work sometimes the cores are glued with hard epoxy resin and boiling will not dissolve it.

[@AliensInc.]

Hi Silvio. I've been watching this with a very big interest as I'm thinking of trying to build my own Boost Converter from 12V to 24V just to try it and is using this video as a tutorial, but I got some questions. What is Bmax? and how did you deside to go with the value 1200-2000? For the turns for both primary and secondary windings, why do you have more than one layer? how did you figure this number out? Wouldn't a full bridge topology be more efficient?

[@supersilve]

Well there is a guide as for half bridge it all depends on what frequency is used. The higher the frequency the lower the B Max. For 33Khz a B Max of 1800 Guass is just right. if the frequency was lower say 25Khz I will have gone for 2000 Guass. B is the number of magnetic lines in the core. B max is the highest B according to the input voltage. Mains voltage fluctuates and goes up and down higher voltage brings more flux in the core according to the number of turns in the trafo. In your case the calculation for a boost converter using only one switching transistor is somewhat different. If it is as I said you will also be needing a gap in the center leg of the core. The larger the gap the lower the permeability of the core. That calculation I used in the video is suitable only for full bridge, half bridge and push pull topology. If there is more than one layer for a single voltage then coupling between windings will be lower but due to the high current needed it had to be like that otherwise it will not fit. I got more than a 1000 watts with half bridge with a suitable core. Check my 1000 watts smps on you tube. I hope that helps.

[@AliensInc.]

I'll check that out, thanks :)

[@AliensInc.]

I've been trying this but it won't work. Have no clue where the error is. If you feel like I'd love to see your calculation for a fullbridge 12V to 24V SMPS with about 1 or 2 amps output. 😉

[@karastom2304]

Thanks so much, very good explanation , can you please explain how you get the value of Bmax

[@supersilve]

The B max should be between 1200 to 2000 gauss depending on the core material and power absorbed from trafo

[@joshnabours9102]

Is the 1200 to 2000 gauss max flux range related to the material type? Where too low of a flux level for the material will mean you could have used a smaller size transformer for better size/weight efficiency? And likewise, more flux than that range will cause magnetic saturation of the ferrite core material as well as heavy power losses and risk of burning the magic smoke out of the transformer?

[@supersilve]

Regarding flux density I always make some reverse engineering when extracting cores from ATX psu. I will calculate the switching frequency according to the chip used noticing the timing capacitor and resistor values. I will count the number of turns in the primary of the core. This will give me a good approximate of the flux used and also the core material. I will then adjust according to the new frequency used.

[@joshnabours9102]

@@supersilve oh, so it is a rule of thumb type estimate based off of your reverse engineering of the original schematic the part was in. Thank you for the info. I really appreciate your videos by the way. A lot of this stuff can be really hard to learn without seeing someone do it step by step. Thank you for the many hours you must have put in to make these.

[@ayushsharma5379]

1. Formula Shown at Video time 10:15 will also work for a uncut Ring/Toroidal core? 2. What will be the rough B max value we should consider for uncut Ring Core?

[@supersilve]

B max will change according to frequency used 2000 guass at 20Khz and 1200 guass at 100khz. As for the ring core you can calculate the core area and plug it in the formula. Make sure that it is not a powdered iron core as it is not suitable. They act as core with air gap.

[@sc0or]

B I think is Tesla or Webber/m2, not Gauss. Gauss is Ampere/m-1. Gauss is Ф

[@stevenbliss989]

What about the max 90% (2 x 45%) PWM of the SG3525 outputs. Does that not also need to be added as another 10% headroom?

[@supersilve]

For HB, FB, and push pull topologies at 45% duty on each 1/2 cycle we are already at 90% duty. However to regulate at a specific voltage you need to add around root 2 (x1.414 to the wanted regulated voltage)

[@SaiKiran208]

Is this transfor calculation is same for same output voltage but dufferent circuit?

[@jbmlp91]

Thanks for this video!

[@alirazzaghi7207]

Hi Silvio ; very nice -- Just a question can we apply (( push-pull topology = 1/2 Nominal voltage ))

[@supersilve]

In push pull topology you must use the full input voltage in the formula. If for example you are using 12v then the centre tap winding shall be 12v-0-12v.

[@viswanathancr2801]

good video

[@owatthorne2538]

hi very interesting, i am also finding a way to lower high voltage and frequency, this is a good example thank you :) i wonder what will be the output frequency of the 24v secondary? i am just a beginner and experimenting on high frequency drivers.

[@supersilve]

What exactly do you want hi or low frequency? The frequency of the 24v output is the same frequency of the primary of the smps . In the example I shown is 33KHz.

[@owatthorne2538]

i am using high frequency high driver at 10-15 khz going through a high voltage transformer and i just want to tap another transformer to lower the frequency to give me lower voltage at lower frequency if possible 60hz, while keeping the high frequency high voltage running on the side.

[@supersilve]

What output voltage do you need. is it DC or AC? What are you going to power an amplifier charger etc. Maybe I can understand clearly what you really want?

[@mohammadmoezi3813]

hi sir i saw your video that was realy good..sir i want make switching trans with 220Vin and +17v 0 -17v and i dont know i must use of what type of ferrite and that must how type of wire for secendary and primary...pleas lead me thankyou

[@supersilve]

I guess you need your transformer for audio amplifier as I see you need a center tap voltage. For a switching power supply you must know the peak DC output voltage to make the necessary calculation. For audio purpose we usually make a non regulated smps. The size of the transformer depend on the power needed. If you need more information please give me more details.

[@mohammadmoezi3813]

@@supersilve hi mr silvio at first i want say thankyou for answer my question i send several message for several people but that people dont answer to me. so i realy realy thankyou for answer my question...sir for me it's hard that talk at this place...that is my insta page::exorcistmmt. and if you need my emil i can send it for you just enough you tell me..i need more information for make ferrite ...please lead me more sir...again i want thankyou

[@mrinaldas4714]

Leonardo, You are using Half Bridge Topology So voltage is 155v , But if I use Flyback Topology Then what will be the voltage?

[@stephanc7192]

Good video

[@supersilve]

Thank you, you should also see winding small transformers for smps.

[@raer7844]

sir i dont understand secondery winding. cause amper calculation . how can calculate copper 0.6 = 2 amp ? . its not have on chart. and primary layer is grow and center is to big first calculate . first center area = 58 mm. what is secondary area ? where is gone 7 wires ? can u tell again that point ? thank u

[@lbassaudiofactorylalith8729]

thanks for you

[@scienceinnovativebrain]

How you calculated from Windows area this core is suitable for 350 watt can you explain in deep. Or any excel sheet for calculation pls share with me

[@jonasribeiro3479]

What is the number of first and second AWG wires, EE65 Inverse from 12v to 220v? Thank you

[@Chetanrawat77]

Dear sir, thanks for such an informative video. I wanted to ask you that whether I can use the same calculation for getting HT output from transformer..? Thanks you in advance. 😊

[@supersilve]

Yes you can but be careful as the voltage gets higher there is more chance that the HT winding will spark over and short out. Square waves have a lot of DC content and tend to are more readily than sine waves.

[@Chetanrawat77]

@@supersilve thanks sir, well noted. 🙏

[@pacocable]

muy bueno. tiene un like y me he suscrito a su canal. gracias

[@johnconrad5487]

Very good. thanks for sharing. I have subscribed to you. you are an experienced transformer designer. made everything clear. what is the size of the core? I have been looking for a core like that but cannot find it. thanks again

[@supersilve]

The core size is an E I 33

[@johnconrad5487]

thanks.

[@prasanthchigurupatii]

Nice explanation Engineer, but @ 33khz and u using EI33 core so i think it cant handle 14amps and core gets toomuch heat losses

[@supersilve]

It depends on the total power not the current. The core is capable for 350w@33khz

[@prasanthchigurupatii]

@@supersilve yes, considering the total power, I cannot handle more than 5 amps and also please refer power handling chart and kindly do let me know your comment

[@picapauff7886]

amigo si utilizo un hilo q soporta una frecuencia y Hz y sar en un derrumbe para una frecuencia Khz puede dar algún problema

[@rohanchinnicl8059]

Could you please tell me how to calculate for step up inverter, for push pull topology and the core is EE65/32/27 and also what would be the core's maximum power, at what frequency??

[@JulieTech]

Thanks for sharing Sir!!!

[@edmondsimendi]

your chart is saying 0.6mm wire can handle only 0.92 amps, but for 350 watts you need atleast 2.25 amps at 155V primary, how is it possible...?

[@supersilve]

You can calculate the amperage of wire from the area of the wire size for continuous rating you calculate the area of each wire at 4 amps per mm squared. If for example you have 0.5 mm dia wire you find the area 3.142 X 0.25 X 0.25 = 0.196 mm squared so 0.196 X 4 = 0.7 amps. if it is not for continuous rating you can multiply by 6 and even 8 if you have a fan blowing at the transformer. Normally for audio purposes it is multiplied by 6 as the load is not continuous when powering an amplifier for example. so 0.196 X 6 = 1.17 amps now dividing this with with the input current comes 2.25 / 1.17 = 1.92 wires so you use 2 wires side by side to wind your primary winding

[@elger4685]

Mr. Silvio, thank you for your video, I want to ask you what is the difference between the formulas to calculate transformers with nucleus of ferrite and that of the transformers of iron nuclos, because from what I see are very similar

[@supersilve]

Yes they are in fact they just differ a little in the constant when using square wave (4) or sine wave (4.44)

[@elger4685]

thank you, God bless you

[@ArceusMaster50]

I'm a little late asking this but when it comes to making a step down transformer rather than a step up does it matter whether i wrap the primary coil first or the secondary?

[@supersilve]

no not really but its good practice to put the longest winding in the bottom due to it being of finer wire gauge. The secondary in this case may be shorter but thicker and it will fit better on top. Thus like this the primary will be neat and flat on the bottom.

[@NiceTech22]

nice video. Can I use this formula for fly back converter (smps) as well?

[@supersilve]

No the formula is only suitable for half bridge, full bridge and push pull converter.

[@jitendrakumar-ni4ys]

For Secondary turn is it necessary to consider the frequency because i was thinking that 7 wires side by side for more amps to get is a lot. Can it may be made with some THICKER wire probably to reduce that numbers?

[@supersilve]

The wire gauge is selected according to the frequency of operation. This is due to the skin dept as current tend to travel on the outer part of the copper wire. The higher the frequency the thinner the wire should be. I just posted a link on the previous post for the copper wire table there you will find the maximum frequency for each wire gauge can handle . One also has to consider how the wires will fit in the bobbin. Remember that wire in a transformer cannot loose heat quickly due to it being warped on top of each other thus the current handling will be less. Usually 3 to 4amps per mm² for continuous rating and 6 to 7 amps per mm² for 50% duty cycle.

[@jitendrakumar-ni4ys]

@@supersilve thank you

[@abdelazeemhassan3701]

thanks a lot for you but did you know the type of the ferrite material of this core or not and if i did not know the type of the material how i can choose the value of Bmax (max flux density)

[@supersilve]

If I would have known the core material I would have chosen a Bmax of 2000 guass instead as according to the frequency used it would have taken it quite easy. I played it safe and chose 1800 instead. Usually computer ATX smps uses an N87 or PC40 core.

[@cesarmarcedo4472]

Hello Master. 1 doubt. Where did you get this 1414 from

[@supersilve]

1.414 = square root of 2

[@mangducthem]

hello Silvio, your video is very interesting, but could you please help me how to calculate power of Transformer, i mean, if i need transfer 500W, so i will need transformer which how many is square?

[@supersilve]

It all depend on the frequency used and the available window space to accomodate the copper wire according to the current involved in both primary and secondary. It also depend on typology used. Half, full and push pull use the 4 quadrants of the flux while a flyback only use 1 quadrant. The latter the core has to be larger to get the same power compared to half bridge for example.

[@valakatz3967]

Great video thank you for sharing. Can you upload the notes for this video in a pdf file, thanks in advance.

[@carlychat]

Muy bueno amigo... Me gustaría saber cómo optienes número de hilos de los primarios y secundarios...espero no sea mucha molestia gracias.

[@supersilve]

Puede traducir los subtítulos del video a su idioma y comprenderá cómo calcular el número de turnos

[@alexandermorales8460]

excelente thank you

[@electronicsolution9787]

Berry good sir

[@ifnzutech]

Sir can we use this formula for inverter chopper if don't then how to calculate inverter chopper.

[@supersilve]

Yes

[@manya555]

If the input voltage to the power supply was between 100V and 240V will the nominal voltage be: 240V -100V = 140V, 140/2 = 70V giving 100+70V = 170V RMS, 170V x 1.414 = 240V DC peak nominal voltage. If using half-bridge topology 240V/2 = 120V, if using full-bridge topology will it be 240V DC?

[@supersilve]

If the calculation for the primary turns had to be with a wide input voltage such as 100-240 then the calculation for the maximum input has to be considered or at least one has to calculate the maximum B at maximum voltage and see that this does not exceed limits otherwise there is a chance of saturation in the transformer. In return the secondary windings have to be calculated at the minimum input voltage so the desired output voltage can be maintained throughout all the input voltage range. Feedback is essential otherwise the output voltage will vary considerably. As far as half or full bridge it will be the same thing for calculation. Half bridge uses half rectified voltage full bridge uses the full voltage.

[@manya555]

Thank you for the clarification

[@TheWeftmen]

Hello sir, I have 350 watt atx psu, in my transformer primer winding two wire together, the one wire diameter is 0.028 the other is 1.04 and two primer layer and 20 turns Now, I want to rewinding with only one wire diameter, which wire diameter should I choose any idea? And how can I choose working frequency, how can we calculate or understand our atx smps working frequency? My transformer is ERL-35-2 what is the meaning ERL or 35 and 2 any idea? And I see you choose 33 khz, how? Why? How can you calculate 33 khz ? Or this is just a guess? For example why you don't choose 70 khz ? Thank you sir.

[@supersilve]

An ERL35 is a type of transformer core, for example the one in the video is an EI 33 but that does not concern you at the moment. What interest you is the center core area which is calculated by the radius squared multiplied by pie (3.142) This is how to calculate the area of a circle. The cross sectional area of ERL35 is 1.11cm^2. You did not say why you want to rewind the transformer and what are you going to use the smps for. You can use a frequency of up to around 100kHz if you want but do not go beyond that frequency as the core may not be intended to work at higher frequencies. With high frequency there will be more core losses. Not all transistors can handle such high frequencies and care must be taken as they tend to heat up quickly and blow. Mosfets are more suited for high frequency. This will all depend if you are going to use the same switching transistors or not. A mosfet cannot be driven with the same base drive transformer because the voltage and current is different from an NPN transistor. The wire diameter depend on the frequency of operation and the higher the frequency the thinner the wire will get due to skin effect. For up to 68Khz 0.5mm copper wire can be used. For 350w you have to use 2 wires x 0.5mm for the primary. ( if the smps is used for audio) If the frequency is lower say 50khz then 0.6mm can be used. I am assuming that the topology is half bridge. If you want to know approximately the operating frequency you need to download the datasheet of the IC in use and then check the value of the timing capacitor and resistor. You can work out the frequency by the formula details shown on the datasheet.

[@TheWeftmen]

@@supersilve thank you for your nice answer, This is my Power Man and IP-P350AJ3-1 model number computer atx smps, and I can not determine this psu topology ! In high voltage side only one mosfet it is 11N90C and only 2 transformer one is big power transformer(ERL-35-2) other is small, I don't know topology.. I want to rewind because my transformer damaged before, I am sure my transformer is fault, As your answer maybe I rewind for 60 khz, but I think there must be some way or formul for calculating the working frequency with other circuit components(pwm ic or small capacitor and resistor ..etc)

[@supersilve]

@@TheWeftmen As you still have the transformer you can unwind it and count the turns and do it as it was. The thin winding is there to compensate for the switching spikes and probably is connected only at one end. The topology is probably flyback. For calculating flyback topology is more complicated and is beyond the scope of this video.

[@TheWeftmen]

@@supersilve yes thin wire connected only at one end, I want to calculate seconder for 12 volt turns, 5 volt turns and 3.3 volt turns, how can I determine and calculate, I measure the transformer primer pins it shows 450 dc volt,

[@mdsarwerzahan849]

please make a video for push pull transformer winding for 12-0-12 or 24-0-24 to out put 220V AC any watts.