Flyback SMPS Design Question

[Gandalf_Sr]

flyback smps design

I'm looking at building audio amps but the standard PSUs look like they were invented by Marconi; this has me wondering why nobody uses SMPSs for the 35+35 supply. In the example I provide in the picture, there's a transformer/multi-winding inductor that probably runs at nkHz and is small; it seems to have the combined advantages of efficiency and isolation. I ripped apart an old computer PSU and saw that the 115 AC is rectified onto a high voltage electrolytic cap before being fed into the switcher circuit. These PSUs are only $25-$35 apiece.

I understand all the technology but where do you start in terms of prototyping such a circuit? Are there standard transformers/multi-winding inductors to be had or do you have to wind your own? If you do, where do you get the cores and how do you chose the values?

Any guidance appreciated.

 

[devura]

flyback smps

Hi

The circuit U copied is from the TopSwitch design from Power Integrations (visit at www.powerint.com)

U will learn more about SMPS and all related stuff

 

[Gandalf_Sr]

flyback design

Thanks,

I've attached another diagram. I'll be more specific with my question...

The data sheet for the TOP250 says this:

It is recommended that the transformer be designed for
maximum operating flux density of 3000 Gauss and a peak flux
density of 4200 Gauss at maximum current limit. The turns ratio
should be chosen for a reflected voltage (VOR) no greater than
135 V when using a Zener clamp, or 150 V (max) when using
an RCD clamp with current limit reduction with line voltage
(overload protection).

What I'm really after is some guidance, where do I start in terms of building a prototype for the flyback transformer? I'm thinking of either buying one or winding my own.

 

[japroach]

smps theory

People tend to not use smps for audio due to the noise it can introduce. You have to be more careful choosing operating frequency and output filtering when designing a smps for audio. However they should be good for subwoofers.

Another reason is safety. You are dealing with rectified mains which can be very dangerous. I would look into getting an isolation transformer or a variac at least, they can be fairly cheap.

First I would learn some basic theory for smps, this page has some basic info: **broken link removed**

www.smps.com has some design tools but I dont know how useful they are.

Cores probably best to get them off ebay or local electronics store. Salvaging from PSUs is possible, but chances are you will just crack the core (it would need to be rewound). Much easier to get core w/ plastic bobbin that is super easy to wind for a few dollars. There is a fairly common core size/name that I have a couple of but I forget the name atm.

Wish I could help more but I know very little, hope to learn more soon.

 

[devura]

what is reflected voltage in smps

Hi

Just go to

https://www.smps.us/magnetics.html

and get to know more about this

 

[Gandalf_Sr]

zener clamp flyback

Thanks guys, there's a lot of good information in the links you provided

 

[farzam]

feedback loop design basic+flyback +smps

hi
how can we design the feedback loop of flyback topology when using DPAswitch or other similar devices
thanks

 

[jsps]

transformer smps wind

you can visit Precision-inc.com for the transformer with full specifications, they are one of very good experts

 

[vaibhav.k]

smps design software download

hi
U have mentioned POWER Integration site>
that Site is really good u can download software PI EXPERT SITE from that site.In that they have transformer designer also.So u can design transformer according to there instruction.