Today's Message Index:
----------------------
1. 06:01 AM - Schottky steering diodes in parallel (user9253)
2. 09:27 AM - Re: Schottky steering diodes in parallel (Richard Tasker)
3. 10:23 AM - Re: Schottky steering diodes in parallel (user9253)
4. 11:55 AM - On a brighter note: (Robert L. Nuckolls, III)
Message 1
INDEX | Back to Main INDEX |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Schottky steering diodes in parallel |
A search of the archives turned up this:
> 01/02/06
> http://www.opensubscriber.com/message/aeroelectric-list-digest@matronics.com/2983404.html
> . . . . .You can wire multiple diodes in parallel but don't depend
> on this technique to "double" current rating of the steering diode.
> Bob . . .
Does the above statement apply only to multiple diodes contained in one package
such as a bridge rectifier?
If two discrete diodes are connected in parallel, would the total current capacity
be almost doubled? If not, then why? It seems to me that each diode would
carry half of the total current. If one of the diodes were to carry more than
half of the current, then the voltage drop across that diode would increase.
Thus the load would then draw current from the other diode which has a higher
voltage output.
Your explanation of diode physics will be appreciated.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=373751#373751
Message 2
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Schottky steering diodes in parallel |
If the electrical characteristics of the two diodes were exactly the same, then
your supposition would be correct.
The problem comes in when they are not exactly the same - which is all the time.
For example, one diode may have a
0.65V drop at one amp while the other diode only has to pass 1/2 amp for the same
voltage drop. So in this example,
with a total current of 1.5A, one diode handles 2/3 of the total current and the
other handles 1/3.
Because the voltage drop changes very little for a change in current, it only takes
a very small difference in
characteristics to cause a big mismatch in current sharing.
Dick Tasker
user9253 wrote:
> --> AeroElectric-List message posted by: "user9253"<fran4sew@banyanol.com>
>
> A search of the archives turned up this:
>
>> 01/02/06
>> http://www.opensubscriber.com/message/aeroelectric-list-digest@matronics.com/2983404.html
>> . . . . .You can wire multiple diodes in parallel but don't depend
>> on this technique to "double" current rating of the steering diode.
>> Bob . . .
> Does the above statement apply only to multiple diodes contained in one package
such as a bridge rectifier?
> If two discrete diodes are connected in parallel, would the total current capacity
be almost doubled? If not, then why? It seems to me that each diode would
carry half of the total current. If one of the diodes were to carry more
than half of the current, then the voltage drop across that diode would increase.
Thus the load would then draw current from the other diode which has a higher
voltage output.
> Your explanation of diode physics will be appreciated.
> Joe
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=373751#373751
>
>
Message 3
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Schottky steering diodes in parallel |
Thanks Dick Tasker,
You explained that very well. It looks like it would be better to use one diode
rated for the current, rather than parallel smaller diodes.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=373776#373776
Message 4
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | On a brighter note: |
Tried to post this last night but I was not cognizant of
changes Matt had to make to the SMTP servers at matronics.
Seems some Brazilian hacker figured out a way to pipe
gigabytes of trash through Matt's machines. He got it fixed
but it took me awhile to become aware of the changes to
my email client needed to make me compatible. So . . . onward
and upward . . .
--------------------------
I sure hope that this list isn't going to go down a path that leads
to this kind of end. I don't think that we're anywhere close to that
state yet, and that's why I bring it up- this is how it starts, and
like many other infectious patterns, early intervention is certainly
the most effort-effective solution.
I was about to suggest the same thing Jared,
thanks. I know it's getting hot and the hammock
out under the tree looks inviting . . . but
let's not let the heat stagnate our gray matter
or civlity.
Which reminds me. I have a list server set up
for a forum on perceptions of the human condition.
I've got about 50 names of individuals who indicated
and interest. All I need is a 36 hour day . . .
But I do know that I have enough faith in Bob's work to bet my life
on it, and I'd certainly like to have a place where I can stay
abreast of changes and updates to the system designs, and the gradual
changes to what we think of as best practices.
Fortunately, very few cases of serious injury
or damage has roots in system architecture or
selection of components. I think the greatest
value of what we offer here is collaboration
on failure tolerant design and lowest cost
of ownership tailored to the aircraft and its
proposed mission.
Wouldn't it be great if this list can continue to be that
source? Isn't that more likely to be the case if we can stay away
from these kinds of discussions, whether or not we agree with the points?
Agreed.
On a brighter note, the power FETS for the joint
collaboration on a new Wig-Wag are here. I thought
I was going to get time to build some POC first articles
last night . . . but one of the light fixtures over my
bench crapped.
TWO lessons learned: These $10 Wallmart fixtures
are very unfriendly for replacement of ballast.
Further, if ballast replacement in less than 10 years
is a modern reality, then make sure your installation
is friendly to the task of taking the entire fixture
down for replacement. The toggle bolts I used to hold
a two-fixture strip to the ceiling went through close
fit holes in the fixture (insert cursing and blood
spatters here). NOW the bolt goes through a large
clearance hole courtesy of Mr. Dremmel and his
magic cut-off wheels. The next replacement will be
easy.
Anyhow, I'll get the two POC items built this evening.
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|