Mains adaptor Ac to DC

Thread Starter


Joined Oct 19, 2010
How to design a compact mains adaptor AC to DC....
Spec 230V AC 50Hz to 5V DC 500mA....
Is thare any good literature available... i would like to keep the form factor minimum....I have to design for a portable application ....
Also Any lay out considerations for high voltage AC...
Please help
Rakesh M


Joined Mar 14, 2008
There are many of those available as wall-worts. Why do you want to build you own?

The smallest type use a switching converter which minimizes the size of the magnetics.


Joined Dec 26, 2010
It seems highly unlikely that you would be able to make anything as small and cheap as those which are now mass-produced in China.

Is this for a school assignment?

Thread Starter


Joined Oct 19, 2010
Application is for a sensor board... the requrement asks for a 230 V AC input.....
The whole voltage conversion should be done by the Sensor board , and power the sensor , microcontroller charge battery generate alarm etc....


Joined May 11, 2009
The problem in designing a switch mode power. May in many cases be to get a proper transformer. If you want to purchase 10000 no problem. But just a few that is not so easy. Once more is this a school project?


Joined Apr 27, 2007
Why don't you use a regulated linear power supply? They are much less hard to design and the parts are easy to find. Plus, they produce a very clean DC current. Does it really need to be compact?

Thread Starter


Joined Oct 19, 2010
Application needs a device that is of light weight and small size. Heavy magnetics will only make the product bulky ...
Though the design is hard it is not the critical part of our design .... So i would like to have a reference design which i could follow one to one ...
Please help in this aspect


Joined Jul 17, 2007
Is it absolutely essential that the power supply be on board the products' main board?

This will increase the size weight and cost of your product, and could make any certification process much more difficult. If you could instead use existing designs such as a regulated "wall wart", you would benefit very significantly, as these types of supplies are very compact, inexpensive, reliable, and would keep the heat that would otherwise be generated on your board at some distance.

You are going to need a power cord anyway; that power cord might as well have an efficient AC-DC converter on the wall outlet end of it.

If you really do need an on-board supply, you might consider an off-the-shelf solution such as this thru-hole PCB mount 3W supply:
The 5v 600mA 3W supply exceeds your requirements by 20%, which is a perfect fit for reliability concerns. The dimensions being L:37mm W:23mm H:15mm makes the device remarkably small. These board supplies already have numerous certifications, so that would help to speed up any certification process your product needs to go through.

The efficiency is only around 72%, which certainly is not stellar - but that's about what you can expect with a flyback converter solution.

Rapidonline stocks them:
£9.24/ea if you buy in quantities of 10.

If you try to "roll your own" supply for the board, you will likely save money on components, but you will have to sell a LOT of units to justify the engineering expense, and the additional expenses for certifications that will be required; after all, this product will need to be certified for operating in an explosive gas environment.