SMPS circuit to drop from 220V to 12V

[Mishka]

Hello everyone.
I'm looking for SMPS circuit with high efficiency to drop from 220Vac to around 12Vac that can supply around 1.5Apms.
Please help me to find a circuit matches the requirements above.
And another question, if i'll supply to this circuit just 110Vac, i'll still get 12Vac? or just 6Vac?
Thanks in advance.

Mishka

 

[Reloadron]

A SMPS will typically deliver a DC voltage. If you just want 220 VAC to 12 VAC why not just use a simple transformer or AC output wall wart transformer. If you put 120 VAC in a 220 VAC transformer designed for 12 VAC out you will get 6 VAC. What's the reasoning for a switch mode power supply? You are only looking for 1.5 amps.

Ron

 

[Mishka]

Sorry, my mistake, i need 220Vac to 12Vdc, so SMPS is great for this purposes.
even at 1.5Amps transformer is much bigger that SMPS, less efficient and cost more.

 

[Nigel Goodwin]

Sorry, my mistake, i need 220Vac to 12Vdc, so SMPS is great for this purposes.
even at 1.5Amps transformer is much bigger that SMPS, less efficient and cost more.

You can easily, and cheaply, buy such supplies as 'wall warts' - far cheaper and easier than making your own.

 

[Reloadron]

Option #1

OK, then if SMPS is what you want you can run out and buy **broken link removed** with an input voltage anywhere between 85-264 Vac. Excellent specifications as you can see. It carries a price of about $130 USD.

Option #2

You can hack an old ATX home computer SMPS for considerably less money. Sort of overkill.

Option #3

Just use a simple everyday wall wart. Which has been suggested.

Ron

 

[dougy83]

You can use an integrated converter chip, e.g. FSQ0370, FSDM0565. Just needs a transformer and a few support components.

You can set the thing up to run happily with a wide range of input voltages, e.g. 85-240VAC (or whatever) and to provide the same output voltage (e.g. 12VDC).

 

[Nigel Goodwin]

You can use an integrated converter chip, e.g. FSQ0370, FSDM0565. Just needs a transformer and a few support components.

The problem is the transformer, you would normally have to wind it yourself.

 

[dougy83]

The problem is the transformer, you would normally have to wind it yourself.

That's an easy problem to solve. There's not that many turns on the primary (in the order of 100 or so), and the secondary is a tenth of that.

 

[Nigel Goodwin]

That's an easy problem to solve. There's not that many turns on the primary (in the order of 100 or so), and the secondary is a tenth of that.

And how safe is a homemade transformer?, it's a crucial safety item, I wouldn't like to trust my safety to a homewound one.

In any case, the cost of the parts is still going to be higher than a wallwart.

 

[dougy83]

Of course, it's as safe as you make it. I would trust one I made.

Yes, it's likely going to be more expensive to make one yourself than to buy a mass-produced consumer item, but it really depends on what the goal is as to which approach to choose. An easy approach for an SMPS converter is incorporating the aforementioned IC.

 

[Mishka]

Thanks you all, but i searching for a circuit to SMPS like in the WallWart.
i know many other options, but i want to build it myself for learning more about control circuit in aSMPS.

Mishka

 

[dougy83]

Basic circuit (needs a little extra gear) on page 2, full schematic (doesn't need as much stuff) on page 15: https://www.electro-tech-online.com/custompdfs/2011/08/FSDM0565RE.pdf

Same deal for the FSQ0370, circuits on pages 2 & 12: https://www.electro-tech-online.com/custompdfs/2011/08/FSQ0170RNA.pdf

These circuits are used in SMPS wallwarts. Note that for 18W output, the FSQ070 may need some heatsinking (stated guidelines of 13W max for plugpack)

 

[simonbramble]

If you are good at electronics (read: you will not blow yourself up) look at Power Integrations. They do a whole ton of chips for this exact purpose. The LNK link switches are the cheapest, but non isolated. Some transformer manufacturers have teamed up with them to provide off the shelf solutions for the magnetics too

 

[simonbramble]

The standard component that old wall warts used to use is the 3842/3844 from ST.com with a TL431 to close the feedback loop. Things have moved on in recent years and Power Integrations have sewn up the market for the single chip solutions.

 

[Mishka]

FSDM0*65RE and FSQ0*70RNA on Ebay cost around 10$ each.
But 3842 and TL431 cost less than a dollar together!
So if i can built SMPS 220V to 12V 1.5Amps from 3842 and TL431, it will cost just few bucks.
simonbramble, do you have the circuit that can do the job?
thanks for the help.

Mishka

 

[simonbramble]

Personally I would look at the Link Switches and Top Switches from Power Integrations. The 3842 is very old and needs a lot of (finely tuned) components around it and it might not work stabily at the end of the design. The PI devices have all the compensation built in, so should work first time. Have a look on their website for hundreds of reference designs

 

[SneaKSz]

If you care about safety, you can use a flyback. I can give you the schematics and formulas to design a 220 AC to 12V.

 

[simonbramble]

Here are the design equations for a Flyback Converter:
http://www.simonbramble.co.uk/dc_dc_converter_design/flyback_converter/flyback_converter_design.htm

with LTSpice simulation files too, although these are only for low voltage applications. Offline should be the same

- Simon

 

[Mishka]

I don't so worry about safety because all the system will be closed, hope in epoxy, and no one will can't touch it.
I searching for design with efficiently over 90% and as much cheaper as can.

Mishka

 

[Mr RB]

Just buy a Chinese 12v SMPS 1.5A wall-wart from ebay and pull out the little 90% efficient PCB and set it in epoxy then?

It sounds to me that its not really about learning as you juts want to make one unit and then it's set in epoxy and finished? Just buy one for $10 and save yourself hours of blown parts and possible lethal danger.