Power supply?

Hello,

Asides from the traditional way of making
power supplies which is with a transformer
connected to a typical bridge and a couple
of caps for filter, I am far from being
a power supply specialist.

That being said, I have the choice of
searching for a power supply of 120vac to
to 14vdc or I can go with a power supply
of 120vac to 24 vdc.

My question is... which one of the two
would take up the least space in terms
of components.... for ex.... transformer
size.

I basically require about 300ma on the
secondary.

Also, is there other components available
that would accomplish my power supply
without the use of a big transformer??

thanks for all feedback..

r

I would just buy a power supply from MPJA.
http://www.mpja.com/power-supplies.asp

This one is 3 inches by 5 inches and is only 10 bucks..
http://www.mpja.com/24-Volt-Power-Supply-1A-Power-One/productinfo/18289+PS/

It depends on your application. What are you trying to power?
If you are going to power a circuit that has its own DC regulator, you need a DC supply that is about 2V higher than the regulated voltage.

Note that the voltage output stated on a wall adapter can be misleading. A wall wart that says 12VDC could very well be putting out 15 to 18VDC with no load.

Hence, as an example, if I needed 5VDC @ 500mA, I would try to find a 7 to 9VDC wall adapter. A 12VDC adapter will make the regulator run very hot.

You can usually tell the difference between an adapter with a transformer and one without. A transformerless wall adapter is usually smaller and lighter in weight. These are already regulated and one that outputs 5.1VDC @1A or 3A is quite common.

The decision to go with 14V or 24V depends on what you're going to power with it. For example, if you're going to use linear regulators to create 5V and 3.3V, then the 14VDC supply is better because you'll have less drop across the regulator than you would if you chose the 24V.