On different forums, I often find people asking for help in
calculating the required turns for a ferrite transformer they are going to use
in high-frequency/SMPS inverters. In a high-frequency/SMPS inverter, the
ferrite transformer is used in the step-up/boost stage where the low voltage DC
from the battery is stepped up to high voltage DC. In this situation, there are
really only two choices when selecting topology – push-pull and full-bridge.
For transformer design, the difference between a push-pull and a full-bridge
transformer for same voltage and power will be that the push-pull transformer
will require a center tap, meaning it will require twice the number of primary
turns as the full-bridge transformer.

Calculation of required turns is actually quite simple and I’ll
explain this here.

For explanation, I’ll use an example and go through the
calculation process.

Let’s say the ferrite transformer will be used in a 250W
inverter. The selected topology is push-pull. The power source is a 12V
battery. Output voltage of the DC-DC converter stage will be 310V. Switching
frequency is 50kHz. The selected core is ETD39. Remember that the output of the transformer will be high frequency AC (50kHz square wave in this case). When I refer to an output of high voltage DC (eg 310VDC mentioned above), this is the DC output obtained after rectification (using ultrafast recovery diodes configured as bridge rectifier) and filtration (using LC filter).

During operation, the battery voltage does not stay fixed at
12V. With high loads, the voltage will be less than 12V. With low loads and
near-fully charged battery, the voltage may be higher than 13V. So, it must be
kept in mind that the input voltage is not constant, but is variable. In
inverters, the battery low-cut is usually set at 10.5V. So, we’ll take this as
our lowest possible input voltage.

Vinmin = 10.5V

The formula for calculating the number of required primary
turns is:

For our push-pull transformer, this will be one-half the
required number of turns.

N

_{pri}means number of primary turns; N_{sec}means number of secondary turns; N_{aux}means number of auxiliary turns and so on. But just N (with no subscript) refers to turns ratio.
For calculating the required number of primary turns using
the formula, the parameters or variables that need to be considered are:

- Vin
_{(nom) }– Nominal Input Voltage. We’ll take this as 12V. So, Vin_{(nom)}= 12. - f – The operating switching frequency in Hertz. Since our switching frequency is 50kHz, f = 50000.
- B
_{max}– Maximum flux density in Gauss. If you’re used to using Tesla or milliTesla (T or mT) for flux density, just remember that 1T = 10^{4}Gauss. B_{max}really depends on the design and the transformer cores being used. In my designs, I usually take B_{max}to be in the range 1300G to 2000G. This will be acceptable for most transformer cores. In this example, let’s start with 1500G. So B_{max}= 1500. Remember that too high a B_{max}will cause the transformer to saturate. Too low a B_{max}will be under utilizing the core. - A
_{c}– Effective Cross-Sectional Area in cm^{2}. You will get this information from the datasheets of the ferrite cores. A_{c}is also sometimes referred to as A_{e}. For ETD39, the effective cross-sectional area given in the datasheet/specification sheet (I’m referring to TDK E141. You can download it from here: www.tdk.co.jp/tefe02/e141.pdf ), the effective cross-sectional area (in the specification sheet, it’s referred to as A_{e}but as I’ve said, it’s the same thing as A_{c}) is given as 125mm^{2}. That is equal to 1.25cm^{2}. So, A_{c}= 1.25 for ETD39.

So now, we’ve obtained the values of all required parameters
for calculation Npri – the number of required primary turns.

Vin

_{(nom)}= 12 f = 50000 B_{max}= 1500 A_{c}= 1.25
Plugging these values into the formula:

N

_{pri}= 3.2
We won’t be using fractional windings, so we’ll round off N

_{pri}to the nearest whole number, in this case, rounded down to 3 turns. Now, before we finalize this and select N_{pri}= 3, we better make sure that B_{max}is still within acceptable bounds. As we’ve decreased the number of turns from the calculated figure (down to 3.0 from 3.2), B_{max}will increase. We now need to figure out just how much B_{max}has increased and if that is still an acceptable value.
Vin

_{(nom)}= 12 f = 50000 N_{pri}= 3 A_{c}= 1.25
B

_{max}= 1600
The new value of B

_{max}is well within acceptable bounds and so we can proceed with N_{pri}= 3.
So, we now know that for the primary, our transformer will
require 3 turns + 3 turns.

In any design, if you need to adjust the values, you can
easily do so. But always remember to check that B

_{max}is acceptable.- For example, if for construction difficulties, winding
3 turns + 3 turns becomes difficult, you may use 2 turns + 2 turns or 4 turns +
4 turns. Increasing number of turns won’t hurt – you’ll just be under utilizing
the core. However, decreasing number of turns increases B
_{max}, so just recheck to make sure B_{max}is okay. The range I’ve stated for B_{max}(1300G to 2000G) is just an estimate. It will work for most cores. However, with many cores, you can go higher to decrease the number of turns. Going lower will just be under utilizing the core, but may sometimes be required if number of turns is too low.

- I’ve started off with a set B
_{max}and gone on to calculate N_{pri}from there. You can also assign a value of N_{pri}and then check if B_{max}is okay. If not, you can then increase or decrease N_{pri}as required and then check if B_{max}is okay, and repeat this process until you get a satisfactory result. For example, you may have set Npri = 2 and calculated Bmax and decided that this was too high. So, you set Npri = 3 and calculated Bmax and decided it was okay. Or you may have started with Npri = 4 and calculated Bmax and decided that it was too low. So, you set Npri = 3 and calculated Bmax and decided it was okay.

Now it’s time to move on to the secondary. The output of our DC-DC
converter is 310V. So, the transformer output must be 310V at all input voltages,
from all the way up from 13.5V to all the way down to 10.5V. Naturally,
feedback will be implemented to keep the output voltage fixed even with line
and load variations – changes due to battery voltage change and also due to
load change. So, some headroom must be left for feedback to work. So, we’ll
design the transformer with secondary rated at 330V. Feedback will just adjust
the voltage required by changing the duty cycle of the PWM control signals.
Besides feedback, the headroom also compensates for some of the losses in the
converter and thus compensates for the voltage drops at different stages – for example,
in the MOSFETs, in the transformer itself, in the output rectifiers, output
inductor, etc.

This means that the output must be capable of supplying 330V
with input voltage equal to 10.5V and also input voltage equal to 13.5V. For
the PWM controller, we’ll take maximum duty cycle to be 98%. The gap allows for
dead-time.

At minimum input voltage (when Vin = Vinmin), duty cycle will
be maximum. Thus duty cycle will be 98% when Vin = 10.5 = Vinmin. At maximum
duty cycle = 98%, voltage to transformer = 0.98 * 10.5V = 10.29V.

So, voltage ratio (secondary : primary) = 330V : 10.29V =
32.1

Since voltage ratio (secondary : primary) = 32.1, turns ratio
(secondary : primary) must also be 32.1 as turns ratio (secondary : primary) =
voltage ratio (secondary : primary). Turns ratio is designated by N. So, in our
case, N = 32.1 (I’ve taken N as the ratio secondary : primary).

N

_{pri}= 3
N

_{sec}= N * N_{pri}= 32.1 * 3 = 96.3
Round off to the nearest whole number. N

_{sec}= 96.
Thus 96 turns are required for the secondary. With proper
implementation of feedback, a constant 310VDC output will be obtained
throughout the entire input voltage range of 10.5V to 13.5V.

Here, one thing to note is that even though I took 98% as the
maximum duty cycle, maximum duty cycle in practice will be smaller since our
transformer was calculated to provide 330V output. In the circuit, the output will
be 310V, so the duty cycle will be even lower. However, the advantage here is
that you can be certain that the output will not drop below 330V even with
heavy loads since a large enough headroom is provided for feedback to kick in and
maintain the output voltage even at high loads.

If any auxiliary windings are required, the required turns can
be easily calculated. Let me show with an example. Let’s say we need an
auxiliary winding to provide 19V. I know that the output 310V will be regulated,
whatever the input voltage may be, within the range initially specified (Vinmin
to Vinmax – 10.5V to 13.5V). So, the turns ratio for the auxiliary winding can
be calculated with respect to the secondary winding. Let’s call this turns
ratio (secondary : auxiliary) N

_{A}.
N

_{A}= N_{sec}/ N_{aux}= V_{sec}/ (V_{aux}+ V_{d}). V_{d}is the output diode forward drop. Let’s assume that in our application, a schottky rectifier with a V_{d}= 0.5V is used.
So, N

_{A}= 310V / 19.5V =15.9
N

_{sec}/ N_{aux}= N_{A}
N

_{aux}= N_{sec}/ N_{A}= 96 / 15.9 = 5.96
Let’s round off N

_{aux}to 6 and see what the output voltage is.
V

_{sec}/ (V_{aux}+ V_{d}) = N_{A}= N_{sec}/ N_{aux}= 96 / 6 =16.0
(V

_{aux}+ V_{d}) = V_{sec}/ N_{A}= 310V / 16.0 = 19.375V
V

_{aux}= 19.375V – 0.5V = 18.875V (rounded off)
I would say that’s great for an auxiliary supply. If in your calculations you come to a voltage that is too far off the required target voltage and thus greater
accuracy is required, take V

For example, if in our previous example, instead of18.875V we had gotten 19.8V but needed more accuracy, we could've used 24V or thereabouts and used a voltage regulator to give 19V output.

_{aux}as something higher and use a voltage regulator.For example, if in our previous example, instead of18.875V we had gotten 19.8V but needed more accuracy, we could've used 24V or thereabouts and used a voltage regulator to give 19V output.

So, there we have it. Our transformer has 3 turns + 3 turns
for primary, 96 turns for secondary and 6 turns for auxiliary.

Here’s our transformer:

Calculating required number of turns for a transformer is
actually a simple task and I hope that I could help you understand how to do
this. I hope this tutorial helps you in your ferrite transformer designs. Do
let me know your comments and feedback.

yes thamid it helps me very much,i have a dought generally ferrite transformers required high frequency to drive is 50khz enough to convert 12vdc to 310vdc?

ReplyDeleteone more question home appliances required 230v then y we go for 310v ?

310 = 230V RMS

DeleteHi sandy,

ReplyDeleteI'm glad that my tutorial has helped you.

1) 50kHz is enough for use with ferrite transformer. Frequencies between 20kHz and 100kHz are usually used, with 30kHz, 50kHz, 75kHz and 100kHz being common frequencies.

2) I assumed 220V instead of 230V. I was thinking of sine wave inverter. So, to obtain a sine wave with RMS 220V, the peak must be 220V * sqrt(2) = 311V [sqrt(2) means square root 2, which is equal to 1.4142135....]. So, I took 310V since the DC bus voltage will be the peak voltage. When SPWM (sinusoidal pulse width modulation) is carried out, you will receive an output of 220V.

If you are interested regarding SPWM, you may go through these:

http://tahmidmc.blogspot.com/2011/01/generation-and-implementation-of-sine.html

http://tahmidmc.blogspot.com/2012/10/smart-sine-software-to-generate-sine.html

http://tahmidmc.blogspot.com/2012/10/generation-of-sine-wave-using-spwm-in_10.html

http://tahmidmc.blogspot.com/2012/11/feedback-in-sine-wave-inverter-pic16f.html

Hope this helps.

Tahmid.

yes thamid i have a small request i am trying to develope a 150w inverter with smps transformer ,plz give your mail or send me a mail to this sandy.nani5@gmail.com .i will send my circuit diagram to your mail ,plz verify it for my satisfaction.

ReplyDeletedear tahmid

ReplyDeleteIts really helpful for me I was designing boost converter for my solar home ups. I need help from after reading the following link http://tahmidmc.blogspot.in/2012/09/some-of-my-smps-circuits.html

I was in need of LCR Mere circuit can you post the firmware and circuit.

Thanks for sharing this info.Please visit my site also-design of transformer

DeleteYou can get it if you search on Google. A good design was, I think, the IronBark LC Meter. Do take a look.

ReplyDeleteThanks for your reply...!

ReplyDeleteregards

veera

Dear Thamid I live in Chittagong. I'm also doing Power electronics research. Please contact me at electrorony@gmail.com, or my website is www.ekushebangla.com

ReplyDeleteHi,

ReplyDeleteIf you are interested in contacting me, you can email me at inferno-rage (at) hotmail.com

hi, tahmid the circuits i have see its useful for any fast projects

ReplyDeletei have idea to build power inverter 6kw out put and input voltage is 48vdc the output voltage is 240vac, but in here i want to use SMPS transformer to built and the power mosfet ,can you help me to have any idea to guide me to help on it ,thanks

so keep and touch

hi,TAHmid I forgot give you online email, you can directly email me via segarlinktech@gmail.com

ReplyDeleteand also we can share many more on it TAHMID

my name is SEGAR.

THANKS BYE

Hi,

ReplyDeleteUse SG3525 to feed into high-low side drivers that drive MOSFETs in full-bridge configuration. These MOSFETs will drive a ferrite transformer. Rectify and filter the output. That's the DC-DC stage done. AC conversion stage will depend on a lot of things, most important being the desired otuput. My hunch is that it's sine wave. So use microcontroller and high-low side drivers to generate SPWM and drive MOSFETs in bridge configuration. Filter the output of the bridge and you have a sine wave output!

Hello tahmid.

ReplyDeleteI am planning on building a msps for a car amp. The amp requires a single 50v rail and 300watts.

I rather design the smps to be able to deliver this power continously rather than applying some music coeficient.

So, : 300w , 12v to single 50v (regulated) . My big problem is choosing the transformer core. To be more precise how do i know how much power can a core handle? I know this varies with the frequency but have no idea how to determine it.

For example in here:http://www.irf.com/technical-info/refdesigns/iraudps1.pdf they use a 29mm ring core for 500w(or even 1kw if i understood corectly). I have this core witf 3F3 material http://www.farnell.com/datasheets/1595842.pdf

Will this core be able to handle the 300W continously? Also for this core , Bmax should be 100mT?

Thank you !

How much power a core can handle depends on the core itself and varies from manufacturer to manufacturer. Other factors that affect the power include operating frequency, selected topology, etc.

DeleteA rough idea can be found in Abraham Pressman's "Switching Power Supply Design" book.

I will take a look at the core datasheets you have linked to and let you know more.

Regards,

Tahmid.

hi i really love your tutorials but i would like to ask how i would go about when in comes to winding transformers for switch mode power supplies

ReplyDeletedoes the same rule apply and i would also like you to email me a h-bridge inverter circuit i would love to construct one for my final year project my email address is djultra0008@gmail.com thanks

Hi,

DeleteThe tutorial presented here is for switch mode power supplies. I had the push-pull and full-bridge SMPS transformers in mind when designing it. Of course, I had in mind a low voltage to high voltage converter, although the same idea/principle can be applied for high voltage to low voltage converter.

As for the H-bridge circuit, I suggest you do some research and design the circuit. If you're stuck somewhere, then I can try to help.

Regards,

Tahmid.

how can we calculate b(max)..flux density for E55 core..?? can u please tell me.?input voltage 12 volts dc,output 350 volts dc,

ReplyDeleteChoose something between 1300G and 2000G. That shouldn't be a problem. How about starting with 1500G?

DeleteRegards,

Tahmid.

such a gr8 blog.please visit my site also.......Potential Transformers

Deleteby using push pull topology

ReplyDeletedude..!!! how do we know that ..specific core has specific gauss?? am using E55 core ..can u tell me how much gauss it will be?? and for e65 core also..?? please tell me how much gauss it will be??reply me soon

ReplyDeleteA core doesn't have a specific flux density. You choose what flux density the core is to be "operated". This is done by selecting the number of turns with respect to the applied voltage. A core has a limit up to which the flux density can be. This is usually quite a bit larger than 3000G. So, by selecting an operating max flux density in the range 1300G to 2000G, we're "playing it safe".

ReplyDeleteRegards,

Tahmid.

Hi Tahmid, i found your articles very informative and helpful.

Deletecan we use 1300G to 2000G fulx density for 50 or 60 hz transformer if yes then what will be the turns fromula

thanks

ragards M.Abrar

hi tahmid i have some h-bridge circuits i would like to share with you how can i get it across to you one involves the popular tl494 and the other involves the use of the use of the 556 and cd4013 and another involve the ir2153 chip i would like you to have a look at them and i need a few explanation on some areas my email is djultra0008@gmail.com thnks.

ReplyDeleteUpload the files to a file storage site such as rapidshare and share the links here. Just remember to make the files public.

DeleteRegards,

Tahmid.

plz tahmid bro tell me calculations for full bridge same as u have explained push-pull here. i seriously need them for my final year project, plz reply me on my email

ReplyDeletemuhammad.mohiuddin@live.com

or plz post it on your blog i will vist it sometime later, thanx

If you go through this tutorial here, you'll see that I've mentioned that the same calculation can be used for push-pull and full-bridge. The only difference will be that, where in a push-pull transformer, the primary consists of Npri + Npri turns, the full-bridge transformer will only have Npri turns for the primary - no center tap.

DeleteRegards,

Tahmid.

Hi Thamid . Can u please describe How to select a core for a certain power. suppose i need 500w output power, and i also have Ac an Al values form core datasheet, now how to calculate delivered power? Actually it will be very helpful for ur reader if you refer using to relation between area product, winding area and core area, You know what i mean. And thanks for a good artical

ReplyDeleteHi,

DeleteI'll try to write an article on this topic and post it soon. Thanks for the suggestion!

Regards,

Tahmid.

Hi Tahmid, please can this calculation work for torroidal cores as well?

ReplyDeletethanks

It should - just take the appropriate values from the datasheet. Although, I haven't thought of it before. It's intersting and it's good that you brought it up. It should work. But just to be sure, I'll research into it and let you know. In the mean time, you could do some searching too! You might learn something interesting!

DeleteRegards,

Tahmid.

thanks tahmid. just another issue, its not easy getting these ferrite transformer here let alone getting the datasheet. i use to try salvaging the ones from computer psu please how can i identify the type of transformer they are e.g etd39 or etd49 and so on. do you have experience with this pleae help out thanks.

DeleteLook for the datasheet, eg for ETD39 or ETD49. The number (eg 49 or 39) is dependent on the dimensions of the core. The preceding letters (ETD) denote the "shape" and type of transformer. So, by matching the dimensions of your core against the datasheet figures you can identify which core.

DeleteCommon cores used in computer power supplies are EI33 (most popular) and ERL35.

Regards,

Tahmid.

thanks, i will sure check them out more. but please do you know where i could get this cores in india.

DeleteI think you should be able to get them quite easily. I know that Farnell India, which I think is now element14, has quite a lot of them.

DeleteRegards,

Tahmid.

hi tamid could you pls check out this h-bridge circuit use this link https://rapidshare.com/files/850668221/ir2153%20fill-bridge.png

ReplyDeletemy email is djultra0008@gmail.com i would post some later

I'll see and let you know.

DeleteRegards,

Tahmid.

sir plz given me inverter circuit diagram on this transformer....plz sir tahmid needed me inverter circuit diagram

ReplyDeleteof this ferrite core transformer...this transformer of any not found circuit diagram now me.....

You can design the circuit yourself using the SG3525 PWM controller. I've written an article / tutorial regarding using the SG3525: http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

DeleteHope you find this helpful.

Regards,

Tahmid.

or some circuit diagram received but the diagram in auxiliary winding not found...

ReplyDeleteThe transformer was calculated using an example. You can use the calculation methodology for your own use in your own circuits.

DeleteRegards,

Tahmid.

hello Tahmid keep the good work going. I am running into a lot of problems that only u can help me. I recalculated my primary turns for 24v transformer in the formular u gave but when I check I am getting nearly two times the secondary voltage i worked it out for Is there anything else to be changed in the formular other than the input nominal voltage from 12 to 24 v when working out the turns for the transformer. Thank u

DeleteRecheck the calculations carefully to make sure you've done them correctly.

DeleteMake sure you have an LC filter and a minimum load at the output. Don't measure the output voltage without load, feedback or LC filter. With no load, the output capacitor will charge to the peak voltage. Without the load and LC filter, you won't obtain the "averaging" desired and output will be too high.

Regards,

Tahmid.

thank you Tahmid for your support I will do as u suggest because i was checking the voltage without load

DeleteYou're welcome.

DeleteDo let me know the results.

Regards,

Tahmid.

sir your answer of waiting.......

ReplyDeleteSorry for the late replies. I was very busy with school exams.

Deleteplz tell me... where do u live.....?

ReplyDeleteplz......dont your mind plz......i m only asking.....

I live in Dhaka. What about you?

DeleteHi Tahmid,

ReplyDeleteThanks for supporting designers,

we r working on 1KW inverter with below specs

12v-350v dc-dc converter with pushpull topology

e65 core ferrite

full bridge topology with igbt for ac-dc inversion

we r planning to provide the isolated feedback with a transformer

transformer specs are input will be from e65 core transformer and output must be scaled down to 5v dc to connect to sg3525.

plz provide us the details of the transforme like core to be used and no tunrs

thanks in advance.

You can calculate the transformer turns if you thoroughly go through this tutorial. All steps have been covered.

DeleteRegards,

Tahmid.

tahmid plz tell me inverter circuit diagram 12v to 220v step up on this trnasformer ferrite core...if you are knowledge....

ReplyDeleteGo through this: http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

DeleteRegards,

Tahmid.

hi tahmid thanks for your formula on calculating the primary and secondary turns for ferrite etd 39 core i understand the nominal voltage in which is 12 the switching frequency 50khz which is 50000 the bmax or flux density you choose to be 1500 and the core area 1.25cm2 to give 330V but i dont know how you arrive at the 10 to the eighth power or the number 4 placed in the formula could you please give an explanation on it because i would truely appreciate it and secondly if i am going to calculate the number of primary and secondary turns for the transformer to work from 24VDC do i just have to put in 24 as the nominal voltage in or there is other things in the formula that will have to be adjusted or changed i truely have high regards for your work time and your answers to our questions thanks again please give an answer at anytime within your convenience thanks

ReplyDeleteHi,

DeleteThanks for the compliments.

The 10^8 term comes due to conversion of the different units to "standard units", ie from cm^2 to m^2 and Gauss to Tesla. You can eliminate the term 10^8 if you use m^2 instead of cm^2 and Tesla instead of Gauss.

Remember that 1 m^2 = 10^4 cm^2 and that 1T = 10^4 G . That's where the 10^8 comes from.

I hope that clears things up.

You can just put in 24VDC there. Nothing else needs to be adjusted.

Wishing you success on your project,

Tahmid.

thanks tahmid i fully understand everything worked on my project and everything is working well but one more thing the 98% duty cycle you choose to calculate the number of secondary turns is it that you must use 98% or you can choose a lower duty cycle and whether the duty cycle is high or low what effect would it have on running home appliances thanks again you are the BOSS

DeleteThanks for the compliments.

DeleteI chose 98% as a maximum to prevent cross-conduction. In practice it'll be much lower due to feedback. There isn't a benefit to running it low. Instead, you'll need more turns on the transformers.

Feel free to ask if you have any further questions/queries.

Regards,

Tahmid.

hi tahmid my project has been successful so far but i need to get something clear about "FEEDBACK" i plan to have 288VDC at the output of my dc-dc converter with lc filter, feedback and a minimum load, so from pin 16 to pin 2 of the "SG3525" i put a 5k6 resistor thus voltage at pin 2 is 3.2, from the output of the dc-dc converter i put a 450k resistor to pin 1 and 5k from pin 1 to ground so the voltage at pin 1 and 2 are equal, so 450:5 would give a 90:1 resistance ratio, so 90*3.2 would be 288, NOTE BRIEFLY i am operating from 24VDC i made my calculations for primary turns using the formula, checked b max and everything is in acceptable position i know i need some headroom for "FEEDBACK" to work so i took 98% duty cycle and calculate 0.98*22.5 minimum voltage which gives 22.05, so i calculate my secondary turns by taking 308V:22.05=13.96 so 13.96*7 which is my number of primary turns gives 97.77 rounded off to 98 to be my number of secondary turns do you think my calculations is right? i am looking forward for your reply thanks again in advance and remember you are the BOSS......

DeleteIf you put a 5k6 resistor from pin 16 to pin 2, with no other resistor from pin 2 to ground, the voltage at pin 2 will be 5V and not 3.2V as you have mentioned.

DeleteThe resistance ratio will be 91:1 and not 90:1 as you have mentioned.

Regards,

Tahmid.

hi Tahmid,

ReplyDeletehow do i determine the current rating of wire for a particular transformer power.

This will depend on the wire itself. You can get charts online. Just Google for wire current rating tables or charts. There are loads available.

DeleteRegards,

Tahmid.

Hi Tahmid,

ReplyDeleteabout the ferrite transformer above, how about the diameter of wire?

whether does not effect with the output voltage?

thank you for your advise.

BR

Heri

Choose the wire such that it can carry the entire current without heating significantly. However, don't use thick wires. They'll suffer due to skin effect. Use multiple thin wires.

DeleteTake a look at this:

http://www.powerstream.com/Wire_Size.htm

Regards,

Tahmid.

Hi Tahmid,

ReplyDeleteThis is an excellent post. Please elaborate on wire sizing, is there any different wiring sizing for high frequency transformers ?

Thanks

Amruth

Hi,

DeleteI'll definitely write an article for wire selection. For now, know that you need to choose the wire such that it can carry the entire current without heating significantly. However, don't use thick wires. They'll suffer due to skin effect. Use multiple thin wires.

Take a look at this:

http://www.powerstream.com/Wire_Size.htm

Regards,

Tahmid.

Thanks for sharing it is relevant beneficial information....

ReplyDeleteTransformer turns ratio meter

I'm glad you found it helpful.

DeleteRegards,

Tahmid.

the 98% duty cycle you choose when calculating the number of secondary turns could you choose a lower duty cycle and what effect would it have when load is applied to the dc to dc converter

ReplyDelete98% is the maximum duty cycle that I have taken to be allowable. This has been done to prevent cross-conduction between switching devices, which would result in a short-circuit. There isn't much of an advantage to using a lower duty cycle. The actual duty cycle will be much lower than this in normal operation, due to the implementation of feedback.

DeleteRegards,

Tahmid.

Hi Tahmid I think this is the best pratical inverter building forum on the internet u are teaching the world. I have been trying to put together an inverter over a year now and it since I saw ur blog I am getting some good results.I have three questions

ReplyDelete1 with no AC load on my h bridge should i be getting my 5v drive voltage on the gates of the fets in the dc-dc converter I am using one of ur drive circuits

( My voltage only comes on when a load is connected and increase with added load. off when there is no load ) ?????

2 My AC voltage increases with the amount of load I apply eg from 125 to 140v AC which stage could be giving me this problem I am using 556 and 4013 configuration

Thank u for ur ususal support

Thanks man. I hope to add more and make my blog even better. Your ideas and suggestions are welcome.

Delete1) There should always be a load at the H-bridge output. Testing without load can give erroneous readings. Which driver are you using? Can you show the schematic?

2) It could be the drive stage. A circuit diagram will reveal where the problem may lie. Without a diagram, all I'll be doing is guessing.

You can upload your schematic to imageshack or photobucket or other such site.

Regards,

Tahmid.

Thank u for your reply Thamid but i am not sure I got A Clear answer. I said I want to know if i should have the drive volt on the gate of the fet any at all with no load connected to the h bridge or only when a load is applied this voltage should come up on the gate. I am using a drive circuit similar to you figure 5 design the only difference is there is no 10k from base to ground on my circuit. Could u answer the other part of the question about the increase in AC voltage with increase load which stage could be giving me that problem . Thank you for usual support

DeleteThe drive voltage doesn't show properly on the high-side due to the "virtual ground". If you must test it, remove the MOSFETs, connect VS to ground and test the voltage and frequency at HO with respect to ground. If all's well, remove the short from VS to ground and then connect the MOSFETs.

DeleteRegarding voltage difference, it'll be difficult to try to figure out where the problem lies without taking a look at the circuit diagram. Make sure that the driver circuit is working properly. It sounds like a problem in the driver circuit, even though nothing can be said with certainty without taking a look at the circuit.

I suggest that you, instead of using 556 and 4013, use SG3525. That will be better. Then, just feed the otuput of the SG3525 to the MOSFET high-low side drivers.

I hope you have received the answer to your questions. Feel free to ask if you have any query or doubt.

Regards,

Tahmid.

Regards,

Tahmid.

Thank you Thamid for your reply I will check to see my drive circuit is working properly. One more question which design is better to handle heavier loads the paralell or series transformer configuration in the dc to dc converter. Thank you for your support

DeleteI recommend using one transformer instead of multiple in series/parallel. However, if you must use more than one transformer, you should use the converters in parallel and not the transformers themselves. For example, if you're using push-pull topology and have two transformers, use two push-pull stages to drive both transformers, both from the same input signal. You can connect the outputs in parallel, with current limiting.

DeleteRegards,

Tahmid.

hi tahmid.i am new to this smps stuff.. i have been following all your you-tube posts and blogs on eda board... i am building a 1kw smps inverter according to the circuit diagram you gave in ur link... the only problem is that i am unable to find ft37-77 core.. so could u please help me by suggesting an etd core as an alternative to toroid core and ways to wind it with copper wire...i will be really thankful..

ReplyDeleteHi,

DeleteCould you please mention which link (1kW SMPS inverter) you are talking about?

You can choose one of the higher power ETD cores for this purpose. Some cores you may be able to use are ETD49, ETD54, etc. Of course, you need to keep in mind other factors such as winding, frequency, etc.

Hope this helps!

Regards,

Tahmid.

thanks a lot for responding tahmid... i am building a 1kw inverter based on push pull topology for the dc boost stage which is 12v to 32o v dc using ka3525 pwm chip as in ur link.. at 50 khz. initially i thought of using ft37-77 core but later realized i cant find them in here..i know very little about winding an ETD core so i thought if u could help in selecting an ETD and procedure for winding it...thnks again..

Deletehere is the link to the circuit diagram http://www.ziddu.com/download/21937039/invertercircuit.png.html

DeleteI have mentioned some ETD core names in the above post.

DeleteMy antivirus and browser prevent the webpage (where you uploaded the circuit diagram) from loading due to a "suspected web attack". Please upload again or to another file storage site.

Regards,

Tahmid.

hi again tahmid my project is more successful as i go along, according to your blog on ferrite transformer turns calculation i now have a clear understanding on how to work it out with respect to voltage, frequency, bmax and all that, but there is a few things i want to get more clearly, my questions to you now is, at a switching frequency of 50 khz if i use 22 awg wire to wind the transformer, if i change my switching frequency to 75 khz do i need a smaller wire like about 26 awg to wind the transformer......? next do i have to use a higher switching frequency for a higher wattage inverter or it does not matter as long as the calculations are right...... thanks again for your usual support......

ReplyDeleteYes, as switching frequency increases, you should look to use thinner wire.

DeleteRefer to this chart:

http://www.powerstream.com/Wire_Size.htm

You can use a not too high frequency and just make sure that the calculations are correct. Keep in mind that the higher the switching frequency, the lower the required inductance, capacitance and transformer turns, but the higher the switching losses.

Hope this helps.

Regards,

Tahmid.

thanks tahmid all this really helps so to be more clear on all this you are saying its best to use a lower switching frequency for higher wattage inverters and one more thing, i have seen inverters with the transformers in parallel connection and some with the transformers in series connection, which do you think works better.......thanks again for your support......

Deletehi tamid i designed a 47kz push pull 12v to 310v converter but there is problem i seem to be getting close to 500vdc when rectified i am using an ei33 core ripped from a computer power supply though i have not yet implemented the feedback yet i did all the calculation for the transformer and got 3 + 3 turns for primary and 100 turns for secondary i am wondering if is bcos i winded the primary turns first b4 secondary i chose 1600g as flux pls any help would be appreciated.

ReplyDeleteYou have to use feedback. Without feedback, you'll be running at near 100% duty cycle which will mean very high voltages. Remember that the calculations are done, assuming that proper feedback is in place. The feedback circuitry is to regulate the output voltage depending on input line voltage and output load. The nominal operating duty cycle with correct feedback implementation will be quite a bit lower than 100%.

DeleteHope this helps.

Regards,

Tahmid.

Hello Tahmid I have attached the inverter circuit to an email and sent it to ur email address. This is the circuit I am having the gate voltage problem with.Please check to see if there is a circuit error. Thank you

DeleteHi Tahmid,

ReplyDeletei have ferrite core Type E55/28/28 http://www.ferroxcube.com/prod/assets/ecores.htm

with Ae 420mm2 = 4.20cm2

my question is :

1. i use TL394 for produce 38kHz for drive the push pull. what the problem if i applied this transformer use push pull with frequency 38 kHz ?

2. can i produce 1500 Watt spms use this transformer at 38 kHz push pull?

3. what a good frequency for this application ?

Thnks

Regards

Heri

1) You can very easily use 38kHz. No problems.

Delete2) I think you should increase the frequency.

3) I would say 50kHz to 75kHz. Make sure you use good MOSFET drivers / driver circuits.

Regards,

Tahmid.

Dear Sir,

ReplyDeleteThanks for your valuble information about Ferrite Transformer you can give great help about transformer.

Luminous Inverter

I'm extremely glad that you've found my blog helpful!

DeleteRegards,

Tahmid.

hi tahmid your blog has helped me out the most sucessful way, i have now managed to build a inverter using four dc-dc converters in parallel supplying 310vdc, could u point me to a h bridge circiut that i could build with eight mosfets so i could get 230vac, i really need this and thanks much again

ReplyDeleteI am extremely glad that my blog has helped you. I hope to make my blog even better to reach out to help many more people like you.

DeleteFor the PWM controller, you can use SG3525. Set the frequency to 50Hz/60Hz as required. I've written a tutorial covering the use of the popular PWM controller SG3525. Check it out here:

http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

For the MOSFET driver, you can use IR2110. I've written a tutorial covering the use of IR2110 for MOSFET drive in high-low side configurations (bridge configurations included). Check it out here:

http://tahmidmc.blogspot.com/2013/01/using-high-low-side-driver-ir2110-with.html

Hope this helps!

Regards,

Tahmid.

hi again sir, is there any difference with the h bridge in a 12 volt inverter than that of a 24 volt or its just a standard circuit or the h bridge circuit is built according to the wattage of the inverter thanks........

ReplyDeleteNo matter what voltage you use, the principle is obviously the same. 24V is preferred over 12V for higher powers due to the lower current (for the same power output). This makes component selection and even wire selection easier and due to the lower current, places less "stress" on the components as they need to handle half the current.

DeleteRegards,

Tahmid.

hi tamid here is a funny senario i built a 12v-310v dc-dc converter using an e-i33 core the funny thing here is when i read the ac output section with my meter it shows250v but when i read the dc section its giving me 500vdc is that the recovery diodes are recovering too fast or what ithe diodes i am using is mur460 pls if you have any solution it would be helpful thnks

ReplyDeleteSince your output is DC (you're using a DC-DC converter), you should be using the DC section of the voltmeter. The AC section will give you incorrect reading.

DeleteIt sounds like you're measuring the output voltage with no feedback in place and with no load in place. Place a sufficient load and use a feedback circuitry and then test again.

Regards,

Tahmid.

hi tamid i wound a transformer with with 1 primary turn and 3 sec turns for a push pull. my bm is 2230 for 20khz 6 volt input 3.35cm2 core area. but i dont get any output at transformer can u plz help me

ReplyDeleteHow are you driving the transformer? What is the switching device you are using? Where do the drive signals come from?

DeleteYour answering these questions will shed more light on the problem.

Regards,

Tahmid.

hi tamid do pls know how to manually calculate the area of an etd core ,well since where i live it difficult to buy one so i usually come across so many core but with no labeling so i don't know the core type or its area if you any solutions it would be helpful thnks

ReplyDeleteYou can measure the dimensions of the core and match the values against the values of a standard datasheet to identify which core you have. That way, you can identify the core without needing to have labelling provided to you by your ferrite core supplier.

DeleteRegards,

Tahmid.

when you say 3 turns + 3 turns,that is a number of 6 turns in the primary with 2 wires sticking out or what?please explain

ReplyDeleteThe transformer has a total of 6 turns primary, with a center tap. You take a wire. Join one end to one of the bobbin pins - A. Then wind three turns and join the other end to another bobbin pin - B. Take another piece of wire and join one end to the end B. In the same direction (clockwise/anticlockwise) in which you wound the first three turns, wind three more turns. Then attach the other end of the wire to another bobbin pin - C. A is one end that goes to a MOSFET "leg". B is the center tap that goes to the positive supply (since this is for a push-pull converter). C is the other end that goes to another MOSFET "leg".

DeleteHope this helps.

Regards,

Tahmid.

hi tahmid thumbs up again for your blog, i need some help on selecting some mosfets for my dc-dc converter for a 600 watts inverter ( push pull topology } i use two irfz46n to drive my ferrite transformer but they heat and blow out in a short while...... the irfz46n is rated 50 amps so do i have to add more in parallel to my converter or do i need to purchase mosfets rated at higher amps for example irf3205 which is rated 110 amps and how much should i use, PLEASE i need your help or do you have a way to calculate and parallel mosfets to add up to a certain AMP for 600 WATTS ? PLEASE give me your most clear answer on this and keep up the good work thanks again BOSS ......

ReplyDeleteHow much load did you have at the output when the MOSFETs blew?

DeleteWhich PWM controller are you using?

Describe the MOSFET drivers you are using.

Regards,

Tahmid.

hi again tahmid thanks for your continued help my question to you is, i have a ferrite torodial core the effective cross sectional area in cm2 is 0.946 could i use it in the formula for my transformer calculations....thanks again

ReplyDeleteYes, you should be able to plug it in the formula for the calculation.

DeleteRegards,

Tahmid.

hi tamid in your replies on me getting about 500v dc you said i should place a load on the output and then implement feedback the question is how do i place a load on a 310vdc output and what kind of load are you talking about coz i dont have a load that will take such voltage i am buliding a small inverter and hope to build the circuit in sections thnks

ReplyDeletePlace any load that draws a current resulting in an output power of greater than minimum required power. You can use 2 light bulbs in series. You might use 2 60W or 100W incandescent bulbs in series.

DeleteWhen you don't have sufficient load at the output, the voltage rises to the peak voltage as the capacitor charges to the peak voltage. Peak voltage in your cases seems to be 500V.

Regards,

Tahmid.

This is very useful blog.This blog is useful for construction.Thanks for sharing this blog.transformer suppliers

ReplyDeleteI'm extremely glad to hear that you've found the blog useful. Feel free to share any suggestions you may have.

DeleteRegards,

Tahmid.

Hi Tahmid,

ReplyDeletei have ferrite core Type E55/28/25 http://www.ferroxcube.com/prod/assets/ecores.htm

with Ae 420mm2 = 4.20cm2

my question is :

1. i use TL394 for produce 38kHz for drive the push pull. whether any problem if i applied this transformer use push pull with frequency 38 kHz ?

2. can i produce 1500 Watt spms use this transformer at 38 kHz push pull?

3. what a good frequency for this application ?

thank you very much.

Regards

Heri

1) You can very easily use 38kHz. No problems.

Delete2) I think you should increase the frequency.

3) I would say 50kHz to 75kHz. Make sure you use good MOSFET drivers / driver circuits.

Regards,

Tahmid.

hi tamid in terms of feedback implementation how do i calculate my duty cycle for instance using the sg3535 setting pin 2 to 2.5v as reference how do i calculate the resistor values for pin 1 for a lets say 90% duty cycle since these pins are responsible for the duty cycle thnks

ReplyDeleteYou will get your answer here if you go through it thoroughly:

Deletehttp://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

Regards,

Tahmid.

hi sir,

ReplyDeletei red ur blog and lot of info in ur blog to me, thank for u.

my question is :

my project's primary turns are 4, i turn on my project but switching mosfet are short-circuit , plz help me....

That could be due to a lot of things. Without more information, it would be too difficult to understand what's causing the error.

DeleteWhich controller are you using?

Which driver are you using?

Which topology are you using?

Describe the feedback circuitry you're using.

What are the input and output specifications? What frequency did you use?

What did you select as the maximum duty cycle?

Which MOSFETs are you using?

Describe the transformer output section.

Which transformer core are you using?

What is your load?

Your answering the above will help shed more light on to the problem.

Regards,

Tahmid.

hi Tamid, I,m bret from nigeria.. i really found your blog very useful since i discovered it. keep the good work. Pls i want you to tell me how to do the transformer turn calculation for an smps charger using the half bridge topology. my chager is to handle about 30Amps and 13.8V output frm 220Vac input.

ReplyDeleteTake a look here:

Deletehttp://tahmidmc.blogspot.com/2013/02/ferrite-transformer-turns-calculation_22.html

I'm sure you'll get your answer there!

Regards,

Tahmid.

Hello,

ReplyDeleteThe airticle "Ferrite Transformer Turns Calculation for High-Frequency/SMPS Inverter " is out standing.I found so many entertaining stuff in your blog.Thanks

DC to AC power inverter

I'm glad you've found it helpful!

DeleteRegards,

Tahmid.

Hello Tahmid, Your Transformer calculation post has help me a lot in designing DC-DC converter but recently I moved to DC_AC inverter. I can use the method you post here for my high frequency low voltage DC to High voltage DC (20-400 VDC)tranformer design which works very well, also for the 400v DC side filter inductor design I used the methods in Abraham pressman book and my filter works well, BUT I am having problems with my SPWM wave input to Sine Wave output filter inductor. I am not sure if I should use the same method of low pass filter inductor core design method used in DC filtering or is there any special consideration you have to take into account in design of magnetic material for SPWM filter inductor (for pure sine wave output).

ReplyDeleteSorry for the long wind post. Your help will be greatly appreciated.

Faruq

Nigeria

For LC filter, choose values such that the resonant frequency is close to your output frequency. If your frequency is 50Hz, an LC filter with resonant frequency between 400Hz to 1500Hz should work well. Then you need to size the inductor and capacitor. Don't use too high an inductance - otherwise the output impedance will be very high. Don't use too high a capacitance - this will create rush currents.

DeleteRegards,

Tahmid.

Hello Thamid, I have a question about the equation to calculate an output inductor for a forward converter with a transformer (full bridge). I actually have several formulas and all of them are no the same. Which way do you use to calculate it?

ReplyDeleteTake a look at this:

Deletehttp://tahmidmc.blogspot.com/2013/03/output-inductance-calculation-for-smps.html

I think you should find that helpful.

Regards,

Tahmid.

Nice post about SMPS transformers thanks for sharing nice information. We are also Manufacturer & Supplier SMPS transformer in India

ReplyDeleteBro i want to design push pull invertor . plz help me to design transformer. input DC 40-45 V, output 330-340 V and 500 W . what turn ratio of transformer required .

ReplyDeleteDid you go through the entire tutorial? Everything is covered in this article. Please read it carefully and then ask me if you have any specific questions.

DeleteRegards,

Tahmid.

Dear,

ReplyDeleteI want to design transformer for 240V to 500V Input of AC supply and Output is 3.5V DC with 200mA .

Pls suggest design guideline.

??

What kind of transformer are you designing?

DeleteAre you using SMPS? What topology?

Hi, Tahmid

DeleteDo you still check your hotmail mailbox from time to time , i would like some advice on winding high voltage secondaries.

From what i saw in microwave smps, they seem to wind sections side by side instead of 1 layer over the other.

Hi Tahmid!!!

ReplyDeleteVery nice tutorials you have put up here, very informative.

Tahmid, need clarification on something. Firstly, there is no guide on the internet that shows how to wind a ferrite toroid, yes?

Reason is, I`m trying to wind one, and then to test it out. Say my calculations state 5 turns primary, so that means two wires on the primary side, with the center two, linking them, serving as CT, yes?

Lastly, the secondary and primary is wound the in the same direction? Or can one just wound this bifilar style for primary, over the many turns of secondary? In my circuit I need a step up.

There is a big credit of transformer for getting us current constantly. We cannot think about current without transformer. So it is better to know about transformer for every people. Thanks for sharing the information of transformer.

ReplyDeleteexcellent blog about Inverter Manufacturing.keep on posting

ReplyDeleteInverter Manufacturer

hi tahmid

ReplyDeletei have 2 qustion

1st is i make like you tarnsformer it work fine but it out 330v dc how i convert this to 230v 50hz sine wave Ac voltage ?

2nd is i make transformer to 12v-24v to 330v Vin min = 9v , Vin (nom) = 24v and it connect to 12v and out has a 40w bulb transformer sound like "trrrrr" why it is sound like trrrrr

please help me

The voltage transformers are used in case of voltage fluctuations. You can confer the rigth flow of electricity to the electrical appliances inside your home and save the same from damages.

ReplyDeleteAutomatic Voltage Stabilizer Manufacturers, Servo Stabilizer Manufacturers, Isolation Transformer Manufacturers

Hi really excellent blog, thank you very very much that you are willing to share your knowledge, not many do !

ReplyDeleteHere is a question, if I want to center tap the secondary to 96 + 96 turns, does the formulation change on the primary side to get the same output as with 1 secondary winding?

Or will the 2 secondaries just divided the output power between them.

Thanks for the reply :)

hello sir,i need to convert dc input range of 80v to 150v,and frequency range 160khz to 200khz,using e65 core,to 230v in ac,and power of 1kw,plz help me

ReplyDeletethank you

ReplyDeletethis information was very helpful to me

i'm designing smps to convert from 12vdc to 220vac 50hz

I'm wondering about what are the stages I should follow with arrangement using

also I don't know how to calculate the suitable frequency for the circuit

what is the most important element of the power supply I should choose first

hello tahmid sir.

ReplyDeleteplease solve my doubt

how to calculate the gauge of the wire for your above given example of 3+3 turns & 96 turns xmer 50khz.

can we apply P=VI & V=I(R+jXl) to find max ampere and accordingly the gauge or due to skin effect @ 50khz its better to use litz wire and if yes than of how many core wd respect to max current.

hola mi pregunta es como se comporta una bobina bifilar en un transformador de ferrita tipo E, yo le inyecto un voltaje de 24vcc a 10khz, sin conectarlo de manera tradicional, si no en serie con la carga, en este caso una celda tipo condensador de 1000uf

ReplyDeleteHi,

ReplyDeleteI made my transformer with 8 primary and 100 secondary turn 33KHz ETD29 (76mm^2) with 11V input. I get 10-15times more voltage while testing signal generator. However when I use the voltage (11V) coming from FET (bf245) I see 200mV on the output.what is the reason for that ?

any help is appreciated

hi, Tahmid, pls can u help me with the code or connection for pic 16f72 sine-wave inverter to enable me make use of the normal off / on switch not the soft push reset type, thanks fmtech83 @yahoo.com.

ReplyDeleteHi

ReplyDeletethis is really very helpful article. I go through this site really very nice information.thank for sharing such a nice information.

Dear Tahmid

ReplyDeleteNice to see ur blog. I am an electronics engineer working in thyristor based high current rectifiers. I am planning for design a high frequency rectifier for high current ranges with bridge rectifier construction. can u please guide me and help to design the same.

My questions are

1. for low voltage high current DC output bridge rectifier is suitable??

2. Can i follow your calculation for this rectifier??

3. what is the maximum current i can get from high frequency rectifier??

4. Any book which guide me for designing this system??

thanks

vasu

Hi tahmid

ReplyDeleteU r amasing pls i need ur assintance on how to calculte Ac or Ae of a ferrite transformer.how do I make d calclation for:

I have aaa ferrite core transformer with dis diamension

42mm*43mm*15mm. (Transformer) how d i calculate Ac or Ae

This comment has been removed by a blog administrator.

ReplyDeleteHi Tahmid,

ReplyDeleteI have calculated a transformer for a Push-Pull SMPS that works with 12Vdc and the output is 410V. It has 2+2 turns in the primary and 56+56 in the secondary, with a EE4215 core. In my country I can´t found a company that make that transformer,

Did you ever wound a transformer like this? Any suggestion?

Thanks you very much and congratulations for your blog that is very useful.

Hi tahmid! thanks a million for all your efforts. Just got a question to ask: does the same principle apply to toroidal transformer(in smps). If no, then how do we calculate the relationship between input and output voltage?...pls assist. thanks

ReplyDeleteThe isolation transformers are essentially devices that are used for the reduction of the power surges. The safety and security of the devices can be accomplished by the installation of the devices.

ReplyDeletehow do you determine the b max value?

ReplyDeletethere is not such a value on the datasheets.

hi dear

ReplyDeletecan u share more article on this so that i can get more information on calculation transformer losses

Hi very nice post. Very useful information regarding isolation transformer and its uses. Thanks for sharing this useful blog.

ReplyDeleteif i use primary of 21 turns and secondary of 3 turns and suppling 344volts dc then what voltage, current and frequency will i get in secondary using ferrite core u type transformer.

ReplyDeleteMany companies producing Power transformers in India. Power transformers that will establish the service dependably with the web page, Cost-efficient along with secure through the entire ages.

ReplyDeletehow to calculate the seccion of de windings

ReplyDeletegracias