>Has anyone found a 5V Voltage regulator with an output of approximately
1A..
>that can handle a 30+ Volt input?


Jameel,


If you MUST use a linear regulator in such a high drop application then use
of a series resistor that drops most of the voltage at maximum current will
allow your semiconductor to run cooler. This can be a desirable arrangement
from a  reliability point of view.
Resistors are generally designed to run in a free air non-heatsunk
configuration (but watch your air flow).

eg 24v i, 5v out, 1A max.
Assume 24 volt is absolute minimum Vin. if not use the real Vin min.
Look at regulator dropout voltage WORST CASE across output current range.
Allow a suitable safety margin. Most older tech regulators will require 2
volts or so worst case.

Vdrop max = (24-5-2) = 17 volts.
A 17r resistor would drop all of this at 1A.
Choose something smaller to give you a little more headroom - say 15r or
even 12r.
At 1A a 15r will dissipate 15 watts. Check to see what conditions this is
under (ambient temperature, mounting etc). Allow a factor of 2 or so so you
need a resistor that can nominally dissipate 30 watts continuous (!) Running
a resistor at its full rated value is asking for trouble.
The regulator now still needs to dissipate 4 watts (  (24 - 5 -15) = 4 volts
x 1A = 4 watts) so watch your heatsinking.

A switching regulator is fairly attractive with this amount of voltage drop.




      Russell McMahon
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