A high frequency power transformer

[unitt]

Hi, All

I am search for a sinus high frequency power trafo. I am searching for a long time on the web but I found nothing, still not a direction, nothing by the professionals. The way to get such a trafo is then DIY. One advantage is one
can do what he/she wants, and like. Oh, take a smps one say.
I know that possibility, but the output of a smps is not clean enough, caused through the current. I read this in the Linn cd 12 review on the side of stereophile.

This is useble for any audio application, too for recording.
Linn use a 60Khz oscillator..
Is here anyone who can help me, with a explanation, diagram, circuit. or
anything that can solve mine question, thanks,
unitt

 

[FvM]

There's nothing special with designing a transformer for 60 kHz sine compared to the usual SMPS transformers operated with square waves. Switched mode converters utilizing resonance transformers have approximately sine current waveforms, by the way. There are probably more out there than you are aware of.

It seems like you're also looking for power converter circuits that generates sine waveforms, but I miss a clear question in this regard or even a specification. It would be reasonable to tell what you're exactly looking for.

 

[unitt]

Hi FvM
I want a transformer that will transfer power on 50-60 Khz. A pure sinus, and no sqare
or pulse trough the core.
Thanks for your reaction.

 

[unitt]

Hi FvM,
I forgot to tell that the output is 9 Vac (rms), that become rectified about 12Vdc, and a max,
output power of 25W.
Can you help me for a basic circuit?

 

[FvM]

I don't yet understand the design objectives and involved parameters.

 

[shatruddha]

you'll find this video tut. very much suitable for your transformer design
http://www.youtube.com/watch?v=3nfqBzPMknY

Apart from this you can get some knowledge through following sites
http://www.mag-inc.com/design/design-guides/Transformer-Design-with-Magnetics-Ferrite-Cores
**broken link removed**

you just need to decide a core first. then decide the change in flux that will support your operation. Rest all calculations can be done by equations on these sites.

I'm sure this will help you
Regards
Shatruddha

 

[unitt]

Hi Shatruddha,
Sorry I'am some late, but still tanks a lot for your reaction. Your samples about transformers
is very helpfull, so a good start with explanation. When I read back I guess, I still not clear
what I want. I searching for a diagram that shows a transformer whit an input signal of a pure
sinus wave of 50-60 Khz. Whit a output of 12Vac and 25VA .Rectifier like a lineair way. I know if the input is a square wave a pwm ic is used. This is not what I want.
So, mine question, how can I realize this.

 

[szhighstar]

can you advise input current and output current? and dimension requested for the transformer? thanks!

 

[shatruddha]

Well!!! its a tedious job to generate exact sinusoid. Generally it is done by using spwm. You search a bit about SPWM.
Now the question is do you really need an exact sinusoid? Since transformer works on principle of magnetisation and demagnetisation, even with the square wave, your current increases gradually and so does your magnetic flux. And you get a near sine wave on output. If you want an exact sinusoid, you can add Low pass filters on primary/secondary side. That will yield a pure sinusoid for you.

 

[FvM]

Unfortunately, the OP didn't tell his design objectives. It looks like the "sinus high frequency power trafo" is intended as a kind of low EMI power supply for high end audio equipment as the reference to Linn cd 12 suggests.

I'm not aware of technical design details, so I need to guess. Rather sure, no "sine PWM" is used on the primary (the switching frequency required for a 60 kHz sine would be much too high) . An analog power stage, which would supply ultimate sine quality is unlikely as well because it would involve too much power dissipation. So most likely, we have a square wave switcher, e.g. a H-bridge with a LC filter before the transformer.

A simple bridge rectifier on the secondary would generate a lot of distortions as well, so there's probably another filter on the secondary.

Or these guesses are wrong, there's no true sine waveform, just a series or parallel resonant converter.

 

[unitt]

Hi, guys
Thank you very much for your reaction.
Still for clearity, I have no experience about this item.
But I'am so buzy in mine head with this subject. An explanation
about a smps is not nesessary because they are easily to buy.
I assume that Linn use a "sinus smps on 60 khz" to clean up the output of the smps, because the current output.
I fully realize that we not know what Linn exactly did.
So, I asume Linn use a pure sinus wave. If that is right, the question is , how they controll this circuit?
For example, I need 12V ac out,a corrent of 2 A out. input 12V, trafo 1:1 the output of the smps is around 12V dc.
Mine goal is that I ever self can make such kind of a ps.
I like this discussion.

 

[unitt]

Hi shatruddha,
I have google with spwm, and so far I have understand, its a kind of modulation, a low sinus frequency carrying through a higher wave frequency. It's used for 12VDC to 50/60 Hz 115/230 Vac. An autor stated that residuals
remains in the output signal. I think that is unwanted by what I will. So we will learn.

 

[FvM]

Yes, the Linn design (or anything similar you may want to design) hasn't to do with SPWM, as already mentioned.

 

[unitt]

Hi FvM
I could not expect that Linn have used a noisy PS in that player. But what have they do ?
Szhighstar have you an idea what's happens in that player?

 

[unitt]

Hi.
On the site of EDN I found the voltage doubler.
https://www.edn.com/design/4318130/...nherent-features-of-push-pull-dc-dc-converter, is more explanation.
Then why? I gues the basic can be used for what I search.
Only this circuit generate a square, its switch on and off.

Mine question is how to adjust this circuit so that the input can be a sinus