Switching Regulator

I have a transformer which is rated at 12V AC, 1A

I'd like to turn that into 5V at up to 2A, or a little less than 2A if there's not enough margin.

What's the best switching regulator chip to use with easily available peripheral components? And preferably in a DIP package.

This is a one time build so I don't need super low cost.

I'm not unable to search google, digikey etc myself but it often happens that someone here will suggest a better device.

Reply to
John Smith
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hard to beat the price and simplicity of something like this

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-Lasse

Reply to
Lasse Langwadt Christensen

Perfect. Thanks Lasse.

Reply to
John Smith

ns

you are welcome

if all you want is something that can give 5V@2A from a mains supply I wouldn't bother with a transformer and switcher, just go buy a random USB cell cellphone charger, most are 5V@2A

-Lasse

Reply to
Lasse Langwadt Christensen

Lasse Langwadt Christensen brought next idea :

Bad Bad Advice.. You cannot get 2 amps out of a 1 amp transformer without letting the magic smoke out.

PLEASE LEARN THE FACTS before you give advice. B-)

--
John G Sydney.
Reply to
John G

Den mandag den 21. december 2015 kl. 01.18.39 UTC+1 skrev John G:

ns

it is a switching regulator, input: 12V*1A = 12W, output: 5V*2A = 10W

so it will work as long as the switcher is resonably efficient

ditto..

-Lasse

Reply to
Lasse Langwadt Christensen

I go to the junk store and get those little qubes you plug in that gives a USB port. I remove the board from its case and mount it on the project board.

The last one I did I allowed the USB to be exposed so that I could plug in a device for charging, supply or back feed from a 5 volt source from elsewhere.

Not bad for something that only cost 50 cents at the junk store.

Jamie

Reply to
M Philbrook

Den mandag den 21. december 2015 kl. 01.35.46 UTC+1 skrev M Philbrook:

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just gotta be aware that alot of the cheap fakes cannot deliver what they p romise and are questionable, to say the least, with regards to safety

-Lasse

Reply to
Lasse Langwadt Christensen

Seems like doing it the hard way. You don't say, but assuming you want 5VDC and have 12VAC, you're gonna need rectifiers and caps plus the board and two cords and a fuse and a box to put it in...

5VDC 2A wall warts are easy to find and already packaged and UL approved and...and...they just work.
Reply to
mike

of course.

All the ones I have gotten so far have a transformer in them.

Since the freq is high, the transformer is small.

I would say they are not the best in perfect regulation but they do for hack work. I do put a TVS across it just to make sure in cases where I may have some sensitive stuff.

Jamie

Reply to
M Philbrook

True but that adds to the fun of building it. It's partly for educational purposes (not my education). I was thinking of using a DIP package switcher chip with inductor, schottky diode, ceramic caps etc soldered together but a ready made board saves time.

Reply to
John Smith

Den mandag den 21. december 2015 kl. 01.57.29 UTC+1 skrev M Philbrook:

sure they have a transformer, but that doesn't help much when the isolation on the PCB is less than 1mm

-Lasse

Reply to
Lasse Langwadt Christensen

Ah, details details.. :)

Jamie

Reply to
M Philbrook

Sounds like a contradiction. If it's fun, you'd want to spend more time on it.

Reply to
mike

PLEASE RESEARCH "switching regulator."

Reply to
John Larkin

The National Simple Switchers tend to work great. Some are in multi-pin TO220 type packages.

Reply to
John Larkin

Depends on who's spending what amount of time and what they're learning from it.

Also, soldering it together won't exactly follow the layout guidelines in the data sheets so could potentially run into hard to diagnose stability issues.

Reply to
John Smith

Look at the circuit of a down-chopper:

Second picture on

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and-step-down-chopper

In the proposed set-up the transformer is followed by a rectifier and of course a sufficiently large capacitor, and then comes the down-chopper.

For a 2:1 (input/output) voltage ratio of the down-chopper, the (average 2 A) current through the transistor during conduction only occurs half of the time. Therefore the capacitor on the DC side of the rectifier delivers 2 A to the chopper half of the time.

The transformer is delivering the same average (absolute value of the) current as the capacitor delivers, otherwise the (average) voltage over the capacitor would raise or lower without bound. Therefore the transformer (or rather the rectifier) is loaded with a DC current of more or less 1 A.

Simply put, choppers are DC-transformers.

joe

Reply to
Joe Hey

A 'wall wart' also contains a 'ready made board'. :)

joe

Reply to
Joe Hey

But it's harder to see and probe because you'd have to break the plastic container open. :) And you may not have a schematic for it.

Reply to
John Smith

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