Need SMPS circuit for LM3886 based audio amp

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I haven't read this thread from the top, and I'm to lazy to do that, so what kind of an SMPS are you looking for, how "big", what kind of power are we talking about, how much is to much, costly.... You can basically use a "555", it can handle about 150mA of current, and the frequency is easy to set, so you have xHz and a couple of drivers and two proper FETs, and a transformer+LP-filters(one is not enough, and I hope you're well versed in math... ). There's a cheap and useful circuit called TL497 by TexasInstrument checkout that one, it's only for single supply, but it gives you an idea how to regulate U/I w/ a SMPS....
 
By the way, you can get great circuit diagrams from datasheets, if you just know what circuit you want, then look up the datasheet on the net or if you get it from your dealer... and use the typical application, and you have all the necessary data to modify the "typical application", to suite your needs.... just a tip...
 
The only difference I can see, in the datasheets, are "Sigma", current divided with the core-area. And the ratio seems to be the same, but ED59 will saturate with lower currents than ED49 .... so the turn-ratio i the SAME! Hence the ratio is the same, the difference between the two, is the the amount of iron in the core. The bigger the core = more current. If turn-ratio is 1:1.5 for example, then it is the same, although you've change the core. You have 10V -> 1.5:1 -> 15V or 10V -> 1:1.5 6.6667V. If the U is the same and you want the same values, but more current, the core don't saturate, the ratio remains the same..... Change "10V" to "20V" -> 1.5:1 -> 30V.... then you need to change the ratio... but T=sqrt U1/U2, were U1 is the voltage in and U2 is the output voltage(this is from memory, I might get it wrong!). And the same formula goes for impedance (Z) and current (I), I think...
 
An EE-core vs. toroid or C-core, has only to do with saturation, and EMF. If u build-old-school, with linear PSU, and u gonna use it in an audio application, you want to use a toroid or a c-coe, basically because they are made with ferrite core. EE-transformers has E-shaped discs, each a few millimeters thick, made out of "black-steel". While a toroid or C-cores(looks like an oval-toroid, but has two C-shaped half, they often has very high current handle, and are expensive and only for mains use) are form-pressed ferrite-powder, and they don't saturate as fast as E-shaped steel plates does. And the round-shape, decrease the electro magnetism, it tend to radiate towards the center.
So you don't need to shield it, just place a 2 mm thick aluminum-plate towards the circuit(usually you need not do anything 'bout the radiation).

Read these links for more info!

Transformer - widings

Scroll down to Power Supplies

Rod Elliot Sound page, is a great site for you, he takes you through linear to SMPS, cap-multiplyers and much more....!!
Every formula, question you might have 'bout PSU, UPS, SMPS, POWER-AMP'S, PRE-AMP'S.. anything and everything worth knowing about audio, you will find there!

ESP home

Now you know what you'll be doing for a year or two, so much information is there!! "Go ahead my son, and become an Audio-Guru" :D


(I'm afraid there's no shortcuts when it comes to understanding AF/RF, different power supplies etc. Math, at least a year on collage. You might get by with senior year on high school, but if truly wan to understand WHY, and it's AC which audio, radio, smps are, you need a good understanding of derivatives, trigonometry, complex numbers.....:yikes: )
 
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well don't use it if you don't know how to see it, you don't need it...
Yes you will need fast diode for negative too, higher voltage rating that is inside for 5v, 100v will be enough

I don't know it looks your supply, but I didn't seen one yet that would be 1:1, but if you mean output inductors, I guess you could take them out
 
unseemly proposal....

OK, I spent my day to learn about SMPS construction. I guess I will use only some parts from that PC PSU and will start to make new SMPS.
I can only agree! Locate the Switch Circuit, and keep the switching-output FETs for +12V and if you have the skill and will, keep the trafo as well, remember that yellow is +12V an red is +5V if you back-track, the 20-pin ATX-header have negative voltage(to ground), I'm holding a 420W ATX12V(24-pins), and the total sum of + and - power is 2/3 of the total power rating, but each 12V, +12/-12V, is about 16A.

Or use the +12V connector(4-pin, 2xyellow and 2xblack - ground), which supplies the CPU cores, if it's a "ATX12V - 24-pin", but then it becomes expensive and a good "modern" PC-PSU goes to waste, drive to any junk yard, or recycle station and I'll bet, you'll find a dozen old AT/ATX psu. And what colour is what, you'll find of the net!

Or do the most sensible thing, ask around for a good IC, look up its datasheet!
As I wrote in another reply, why don't you start with a simple 555-cicuit, and two moderate FETs(or BJT), and a core, and play around... it costs nothing, you can try out your idea, take some measurements, calculate and wind the coil for the "real deal", with the data you get from you super simple SMPS.. and with some ingenuity you can even get +/- voltage, you need to AC couple the output from the IC555, so you lift the voltage to ½Vx, but you only drive some low power BJTs with the "555" and add the "right" voltage to the 'source'...

This is just a proposal, to get the "know how", and a cheap why to "teach your self" SMPS!
 
Hmm, isn't this a bit too small for 250W PSU?
 

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The PSU is using KA7500B [analogue of TL494 but I've heard that it generates "cleaner" freqs"]
And sorry about bad pics, and my bad English.

I just found one S494P too.
 

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I think I will rewind trafo. I should left primary untouched right? And for secondary count how much windings there were for 12v rail, then use 12*2,7=32,4V. It means that I have to make one centre tapped winding for secondary, and there have to be 2,7X more turns on each "half" then it was before[for 12v rail]
 
luka: that inductor.. will it be ok if i remove all windings, and will use better wire and the same thing as trafo - previous turns*2,7?
Btw there are nice SMPS at your website


If the inductor is from powder core, I can't substitute it with EE type core? Or maybe this variant: original was yellow-white, but I have some yellow from other, 350W PSU. Maybe this suits for substitution
 
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for primary use same number of turns and how they were put on (1/2+1/2)
for 12v I think you will find 4turns so use so much that you will get 35v or more if you will have regulation... you will need around 11-12 turns for each sec

for inductor, take all of them off, and wind two wire in same direction as many times as it will be needed to core whole core and then some... that you want to make is coupled output inductor
 
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