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'[EE]:Re: 7805 heating up...'
2002\04\03@181211 by Barry Gershenfeld

picon face
>I was thinking similarly about dropping the voltage a bit before letting
>the regulator have it, but I thought of 2 regulators -- first drop to 9V
>or 8V, then the 7805.

Another regulator, a resistor, a light bulb...Just remember that
it all goes to the same place--heat--so you still have the
same problem of shedding it.

This is why switchers are different.  They don't "burn" the extra.

In the old days when cars went to 12v they ran the 6v gauges
using a "switcher" made from a relay.  Probably why the gauges
are so heavily damped.

Barry

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2002\04\03@193022 by Byron A Jeff

face picon face
On Wed, Apr 03, 2002 at 03:00:56PM -0800, Barry Gershenfeld wrote:
> >I was thinking similarly about dropping the voltage a bit before letting
> >the regulator have it, but I thought of 2 regulators -- first drop to 9V
> >or 8V, then the 7805.
>
> Another regulator, a resistor, a light bulb...Just remember that
> it all goes to the same place--heat--so you still have the
> same problem of shedding it.

Yes. And no. The yes part is that heat is of course generated. The no part is
that you can easily use a part that is better suited to manage the heat
dissapation. For example a TO3 power resistor controlled by that 7805 or a
zener can handle the heat better than the 7805 itself. Check out the use of
a pass transistor in your linear regulator.

>
> This is why switchers are different.  They don't "burn" the extra.

Or rather only burn very little during the switching phase.

BAJ

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