Re: Building computer - power supplies
On Sun, 2013-09-29 at 13:20 -0400, Doug wrote:
> On 09/29/2013 06:47 AM, Ralf Mardorf wrote:
> > On Sun, 2013-09-29 at 19:02 +0900, Joel Rees wrote:
> >> I7m confused. Did you mean can't produce a gain in current or power?
> >
> > Assumed there should be a linear voltage regulator able to provide the
> > needed Ampere, how large should the heat sink be? The voltage isn't an
> > issue. By a quick search I found a max. of 10 Ampere. My laboratory
> > power supply does provide only 2 Ampere and the heat sink is
> > 10 cm x 10 cm x 5 cm "small". The once mentioned in "The Art Of
> > Electronics" Horowitz/Hill original 1989 Cambridge University Press,
> > here the German translation 3. edition 1998 provide less than 10 Ampere.
> >
> >
> The size of heatsinks is a function of the heat dissipated in the active
> device, whether it be a regulator, an amplifier, or a rectifier, or even
> a power resistor. It is then a function of the heat transfer
> characteristics of the heat sink. That is dependent on the size of the
> sink, but also on the number and size of the radiating fins, if any, and
> the airflow around the sink, whether is is convection, or aided
> by a fan. All of this is calculated by the maximum desired (or
> allowable) temperature of the active device, the thermal resistance of
> the device to the heatsink, and the thermal resistance of the heatsink
> to the ambient air, which is usually defined as being 25 degrees C.
> All of this is not done by "seat-of-the-pants" design, but by published
> specifications of all the devices--the active device, the insulator, if
> any, the heatsink, and the airflow. The calculations are
> straightforward, but will not be related here.
Sure, some heat sinks can be smaller than others, for the same task, but
assumed there should be a linear voltage regulator > 10 Ampere, the
needed heat sink would be huge or a fan would be needed and as you
already pointed out, the ampere input has to be as high as the output.
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