19 Jan
2010
19 Jan
'10
6:22 a.m.
Date: Tue, 19 Jan 2010 08:37:58 -0500
From: ajp166 at verizon.net
To:
Subject: Re: [personal] Re: Altair 680 power supply...
Mike Hatch wrote:
Hi
While it is incorrect to parallel regulators, one can always split
the power rails to balance the loads. I've seen this done on
a S-100 memory board.
In general, well heat sinked 7805s can be paralleled if the power
drop in is not too large. They do have a built in current limiter
that is designed to handle a continuous constant current without
failure.
It does require good bypass capacitors or the board can make
a nice 1MHz oscillator.
Dwight
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----- Original Message ----- From: "Dave
McGuire" <mcguire at neurotica.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Tuesday, January 19, 2010 8:34 AM
Subject: [personal] Re: Altair 680 power supply...
You cannot parallel fixed regulators such as 7805. If you need more
current either go
to a device that can handle the current or use a regulator and
transistor combination.
I've used the rather low power 7805(to220 part) with an external pass
transistor
to get 5A, the design is straight out of National Semi (and others) apnotes.
Allison
>
>>
>> -Dave
>>>
>>
>>
>> --
>> Dave McGuire
>> Port Charlotte, FL On Jan 18, 2010, at 5:00 PM, Chris Elmquist
wrote:
What's the current ?, 78S05 will give 2A
7805 cannot be directly paralleled due to the small difference in
regulation points part to part. You would need a small value series
resistor per part to load share.
Best regards,
Mike Hatch
soemtron.org
Is it fair (as in rational, smart, non-stupid) to
put multiple 7805 in
parallel? Can't say I've ever seen that done. Only the more typical
design of adding a pass transistor to carry more current.
What about balancing problems? They won't be identical from part
to part..