Mini Transformer?

[tomerp]

Hi,

I need to find away to transform an input voltage of 220V to 3.3V, but I want to use some electronic transformer (if there is something like this). Just to be more clear I'm using the home electricity network (which is 220V-230V) and I need to transform it to 3.3V - without any Normative transformer.

Is there a way to acheive that?

Thanks,
Tomer.

 

[MikeMl]

How much current? Is your life insurance paid up?

 

[mbarazeen]

transformer is the safest way, if you are aware of the risk then its possible to use a voltage divider by using two capacitors and can regulate it to 3.3 by a zener. 1st you have to know the current required.

 

[EternityForest]

i think you are talking about a switching, also known as switchmode power supply. so yes, there are "electronic transformers"
and they work quite well.but why not just buy a 3.3v switching wall wart? it's exactly what you're talking about.

 

[antknee]

Yes buy one, don't make it, it just isn't worth the effort and expense. In fact I'd guess you possibly have something in the garage that has a similar if not the same supply. Buying one will cost say £5 or $8. I'm assuming you just want a plug in power adapter.

 

[tomerp]

Thanks for your replys!

The reason why I don't want to use the wall wart is because I want to build a circuit which will be independent and without the need to be near a wall socket, it supose to be connected to the home electricity network directly.

 

[Boncuk]

I don't get the point.

A device being supplied by mains has to be within the range of the "home electricity network" (generally a wall outlet) anyway.

Operating a 3.3V circuit directly from mains, be it 115 or 230VAC requires some kind of stepdown. Many cell phone and camera charging devices provide 3.3V output voltage.

You might remove the enclosure and make the contained SMPS part of your circuit.

Boncuk

 

[Sceadwian]

I think this is like many posts of this nature Boncuk, they want small size, and think even the SMPS designs are 'large'
I could be wrong though.

 

[dknguyen]

Thanks for your replys!

The reason why I don't want to use the wall wart is because I want to build a circuit which will be independent and without the need to be near a wall socket, it supose to be connected to the home electricity network directly.

So open up the wall wart and hook it up directly...

An SMPS is going to use a transformer somewhere for that kind of step-down anyways...

 

[Sceadwian]

No actually DK they won't always, buck boost or sepic converters can work without transformers. The only requirement is initial rectification.

 

[Boncuk]

I think this is like many posts of this nature Boncuk, they want small size, and think even the SMPS designs are 'large'
I could be wrong though.

You're not wrong at all. The charger for my Motorola cell phone measures 1.5X1X1" and provides 6.25V at 300mA.

A linear power supply of the same power output will require a 2.8VA (9V/311mA) transformer at least measuring 1.3X1.09X1.34" just for the transformer, not counting for the regulator and caps.

 

[dknguyen]

No actually DK they won't always, buck boost or sepic converters can work without transformers. The only requirement is initial rectification.

I didn't say always. I said "for that kind" of step down, referring for the OP's enormous step-down ratio. The low duty cycles required translates into very short switching times which are pretty unreasonable. Hence said transformer, or if you want to get extravagant cascading multiple buck converter stages. Pretty silly though to take that route since we're not stepping down a massive DC voltage to a very low DC voltage- we actually have an initial AC voltage to use a transformer on.