bigdaddy said:
Perhaps I did not make myself clear. I already have regulated supply
of 20V DC in the shape of Dell Power Pack. I want to reduce its
supply of 20V to 13V with a 1 Am. Would it make any difference if I
have excess of 1 Am, when the demand if 1Am ? Thanks
Your Dell power Pack has the capability of providing 20V at _up to_ 3.5
amps. The 3.5 amps is a _maximum_. Your Dell almost never requires
that much current, and sometimes much less (e.g. while it's in energy
saver mode, with the HD and display turned off).
Your power supply is perfectly happy supplying exactly 20V at much less
than 3.5A too, so if you only need 1 amp, or even less, that's OK.
Some switching power supplies require a minimum load, but laptop
supplies are made to be hot plugged, and so your Power Pack will
operate well even with zero current output.
The advice given above by Petrus was good. The Velleman kit (with a
heat sink for the LM317) is a practically foolproof way to get where
you want to go. Also, the instruction sheet assumes you're a newbie,
and relies on pictures rather than text to get ideas across. It's a
winner -- go for it.
Hope this answers your question.
Good luck
Chris
