transformers

Thread Starter

chrisw1990

Joined Oct 22, 2011
551
im trying to locate small transformers for mains supplies, e.g. 3.3V SMPS power supplies, does anyone know of a good source?
tried my usual channels but can only find massive transformers
ideally looking for small surface mount versions (if there are such things)
 

SgtWookie

Joined Jul 17, 2007
22,210
I didn't see your "mains around 25v transformer" statement.

I thought you wanted to go directly from mains to 3.3V DC. That's what the supplies I linked to will do.
 

Thread Starter

chrisw1990

Joined Oct 22, 2011
551
i already have a design for a switched mode power supply, i thought that just putting a transformer, with.. mains on primary : around 25V out (mains around 25v transformer statement) and rectifying it would be a supreme low cost solution compared to trying to get a transformer to work with 3.3V 4A make sense?
 

SgtWookie

Joined Jul 17, 2007
22,210
A mains-frequency transformer capable of 4A @ 25VAC, 50Hz will be quite large, heavy, and not all that cheap.

That's one of the reasons why SMPS's have become popular; the higher you go in frequency, the smaller the transformer can be - within certain limits, of course.
 

Thread Starter

chrisw1990

Joined Oct 22, 2011
551
i know :D
i used the national semi/Texas instruments WebBench tool, says at about 24V input, it will take 450mA current, while this might not be hugely accurate, its a lot better than 4A!

so maybe this is the place to put it, but the LED lighting strips, where they fit into the 5ft flourescent tube slots? how do they convert the AC to DC?
 

SgtWookie

Joined Jul 17, 2007
22,210
LED lighting strips use LV supplies.
Long fluorescent tubes have a ballast to generate high voltage necessary to ionize the gas in the tube.
CCFL's have small HV flyback supplies that will generate 500v to ~1,300v or so to ionize the gas, then they maintain the ionization at a lower voltage with a controlled current.
 

thatoneguy

Joined Feb 19, 2009
6,359
so maybe this is the place to put it, but the LED lighting strips, where they fit into the 5ft flourescent tube slots? how do they convert the AC to DC?
Line powered LEDs are a different animal, and the construction of the power supplies for them are forbidden by the rules of the forum.

Some larger LED installations use a single output switching power supply, think 5V phone charger with USB jack output that only weighs an ounce, but built into the chassis of the light.

The other method is very dangerous and not suited at all to people not well versed with electronics. The danger is the reason the topic is banned here. We can however, help you work with your 24V supply for an LED strip.
 
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