15W AC/DC converter high efficiency

[themaccabee]

Hi,

I want to design an isolated AC/DC converter 12V,15W with universal AC input.The efficiency should be as high as possible. 85 percentage typically.
Also the overall size should be minimum..I was thinking of power integration chips..
Any suggestions??

 

[D.A.(Tony)Stewart]

What are your specs?
PFC value?
EMC compliance?
Safety Compliance?
How many?
Qty vs cost?
Load regulation %?
Line regulation%?

Generally the smallest simplest design is a flyback step-down regulator with optical feedback for regulation. A small torroidal core with center tapped primary and secondary is useful here for switching at high speed so high freq. ferrite can be used vs 50/60 Hz iron core. But skill in choosing the transformer is essential. With additional windings tracking secondary DC outputs is easy.

Otherwise , single phase non-center-tapped is slightly less efficient but uses only one transistor. Both are self-oscillating flyback step-down transformers < 1" diam.


If you just want one PS... a wall transformer is cheapest <30 cents /watt

 

[mtwieg]

For those specs, I'd recommend a transition mode flyback. Transformer design is going to have the greatest influence on size/efficiency. Do some investigation into what sort of core materials and geometries are available to you.

There are numerous control ICs which are specifically designed for these applications.

 

[mister_rf]

The Flyback SMPS theory and some design calculations details here:

**broken link removed**

Switch Mode Power Supply Circuit Design Software /Transformer Calculation / Simulation Tool here:


http://www.poweresim.com

 

[ZekeR]

Here's a nice all-in-one solution, with universal input and active PFC, providing 50 watts.

You can buy the demo board and tweak it to meet your needs.