Re: Building computer - power supplies
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.
--doug
--
Blessed are the peacemakers..for they shall be shot at from both sides.
--A.M.Greeley
Reply to: