Searching \ for '[EE]: Transformer Q...' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: techref.massmind.org/techref/power.htm?key=transformer
Search entire site for: 'Transformer Q...'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Transformer Q...'
2002\12\24@150519 by PicDude

flavicon
face
part 1 600 bytes content-type:text/plain; (decoded 7bit)

Last ditch effort to finish this DC-DC converter before
I head out for vacation...

Winding a toroidal transformer and wondering how the
"dots" align for the schematic symbol.

In the attached image, both coils are wound in the same
"direction" around the toroid.  How does the coil wire
ends match up with the schematic wire ends?  If A1 = X1
and A2 = X2, then B1 = Y? and B2 = Y?

Thanks,
-Neil.


--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics




part 2 17174 bytes content-type:image/jpeg; (decode)


part 3 2 bytes
-

2002\12\24@151920 by Rick C.

flavicon
face
B1=Y1 and B2=Y2
I believe, but you should swap Y1 and Y2 on the schematic and move the dot to
the top, for correct schematic etiquette.
Rick

PicDude wrote:

{Quote hidden}

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics

2002\12\24@163639 by Tal

flavicon
face
Is it so important? which is which? we are talking ac here,
I really don't understand the problem.
please correct me..

Tal

{Original Message removed}

2002\12\24@170758 by Rick C.

flavicon
face
It's very important, depending upon the application. Even more so when a third
or fourth winding are added. Phase relationship, depending upon the application
will make the difference between working or not working at all. Let's say that
two of his torroids are being driven from one AC source and he wants to drive a
complimentary switching circuit or other phase adding circuit. It won't work if
one secondary's wires are crossed. Of course we all know what happens when we
have an out of phase stereo feed such as speaker wiring. In the FM radio
broadcast field that I'm in, phase is so critical because if my audio feed was
out of phase somewhere in the audio chain, someone listening to a mono voice
over a stereo generated transmission would hear nothing on a mono (portable)
radio.
Rick

Tal wrote:

> Is it so important? which is which? we are talking ac here,
> I really don't understand the problem.
> please correct me..
>
> Tal
>
> {Original Message removed}

2002\12\24@171418 by Steve Smith

flavicon
face
Phasing my learnerd friend if the dots are in opposing corners the the
signal is 180 deg out of phase with the input (wen the input is rising
the out put is falling) verry important really.

Steve...

{Original Message removed}

2002\12\24@172040 by Tal

flavicon
face
Rick

I regarded it as 1 coil to one coil winding and as a dc-dc converter, which
mean later you "just"
regulate it so it look to me not so important. in case of sampling
(feedbacks..etc..) then phases are more important.
in case of fm circuit the rules are changing as you mentioned.
this sums my poor switching understanding...:-(

Tal

{Original Message removed}

2002\12\24@172247 by PicDude

flavicon
face
Okay, I'll go with what you say.
BTW, does the "correct schematic etiquette" vary for
toroids vs other transformers?  I ask because this is
the dot-orientation that NS's switching design tools
(SMS & Webench) produce for me.

Cheers,
-Neil.




> {Original Message removed}

2002\12\24@172453 by PicDude

flavicon
face
I really think it is important since the secondary
output will be used to drive the feedback on the
switcher chip.  If the o/p voltage is low, the
switcher will try to adjust the PWM in a certain
direction to compensate, and if this is in the
wrong direction, it could drive the PWM to one of
the extremes (0% or 100%) and not work.

Cheers,
-Neil.




> {Original Message removed}

2002\12\24@172700 by PicDude

flavicon
face
In this specific case, a DC-DC converter with the o/p
fed back to the switcher chip for regulation feedback.

Cheers,
-Neil.



> {Original Message removed}

2002\12\24@173114 by Tal

flavicon
face
Neil

That's exactly what I say. if just regulate it then there is no need to find
the phase.
is your case (now I understand what you mean...) it's very important.

Tal

{Original Message removed}

2002\12\24@175639 by Rick C.

flavicon
face
Either way is okay, but for readability and consistancy, and the actual
application may dictate the dot location. Torroids and other transformers are
treated the same way. Another way of looking at the torroid is to think of it
as if the core were flexible and you cut it and straightened it out. The two
coil phases would look more understandable.
Rick

PicDude wrote:

> Okay, I'll go with what you say.
> BTW, does the "correct schematic etiquette" vary for
> toroids vs other transformers?  I ask because this is
> the dot-orientation that NS's switching design tools
> (SMS & Webench) produce for me.
>
> Cheers,
> -Neil.
>
> > {Original Message removed}

2002\12\25@012808 by Russell McMahon

face
flavicon
face
> That's exactly what I say. if just regulate it then there is no need to
find
> the phase.
> is your case (now I understand what you mean...) it's very important.

Even if you "just regulate it" the polarity can be very important.

Many forms of switching converters (probably most) are designed to deliver
power on one half of a cycle and not the other. Examples include forward
converters, flyback converters and even push pull converters where the
inductor drives a centre tapped output winding. Swapping the winding
connections in most cases will result in poor operation or none at all.



       Russell McMahon

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


'[EE]: Transformer Q...'
2003\03\05@133035 by PicDude
flavicon
face
In my ongoing saga to get this DC-DC converter working, I'm
questioning my transformer design, and would appreciate any
help on this from you gurus in this area, as I've not done
many of these in the past.  The design spec (from National's
SMS tool) calls for...

Primary:  18.18uh, 33.45 mOhms.
Secondary:  0.96uh, 58.46 mOhms.

I've calculated this as followings (using a T-130-3 (gray)
toroidal core)...
Primary:  23 turns of 20-awg, yielding 18.5uh, ~33 mOhms.
Secondary:  22 turns of 20-awg, yielding 0.96 ratio, ~32 mOhms.

The secondary resistance is much lower than required, but is
that a problem?  NS's websim tool seems in indicate that it
is not.

I've wound the coils non-overlapping this time, btw.  See..
http://www.narwani.org/neil/stuff/transformer-03.jpg

For coil phase/orientation, I'm winding with the same direction
(start over the core, going down thru the middle, and moving
counter-clockwise as I wind the turns), with the start of each
winding marked as the "dot".  See the following pic, in which
my "dots" are on A1 and B1.
http://www.narwani.org/neil/stuff/transformer-phase.jpg

Can anyone spot a problem here?

Thanks,
-Neil.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

2003\03\05@134509 by John Dammeyer

flavicon
face
What made you choose the T-130-3?

John

Wireless CAN with the CANRF module now available.
http://www.autoartisans.com/products
Automation Artisans Inc.
Ph. 1 250 544 4950


> {Original Message removed}

2003\03\05@135658 by erholm (QAC)

flavicon
face
First you say :

Primary:  18.18uh...
Secondary:  0.96uh...

then you say :

Primary:  18.5uh...
Secondary: 0.96 ratio...

Why *ratio* in the second case ?

From the first cse I get a ratio of about 0.05 (or 20
depending on which way you look at it).

Jan-Erik Soderholm

{Original Message removed}

2003\03\05@144021 by Roman Black

flavicon
face
PicDude wrote:

> Primary:  23 turns of 20-awg, yielding 18.5uh, ~33 mOhms.
> Secondary:  22 turns of 20-awg, yielding 0.96 ratio, ~32 mOhms.


Sorry if you've already posted this info, but what
input V and I, and what output V and I are you aiming
for, and how big is that toroid?
:o)
-Roman

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

2003\03\05@150026 by PicDude

flavicon
face
Oops... I should've mentioned.  Switching freq is 100khz.

Cheers,
-Neil.



{Quote hidden}

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

2003\03\05@150525 by PicDude

flavicon
face
Another oops ... the .96uh should've been 0.96 (ratio).
I used 23 turns on the primary, and 22 on the secondary
to get the .96 ratio.

Cheers,
-Neil.



> {Original Message removed}

2003\03\05@151149 by PicDude

flavicon
face
Ideally, I need input from a vehicle battery, so I've been
using 10-15V for lots of room on either extreme.  For this
test version, I used 8-15V, so I can power if off a 9-volt
battery.

Output voltage = 12V at 1A (for this test version).

Toroid is a T130-3.  Switching freq = 100khz.

Cheers,
-Neil.





> {Original Message removed}

2003\03\05@160255 by Roman Black

flavicon
face
PicDude wrote:
>
> Ideally, I need input from a vehicle battery, so I've been
> using 10-15V for lots of room on either extreme.  For this
> test version, I used 8-15V, so I can power if off a 9-volt
> battery.
>
> Output voltage = 12V at 1A (for this test version).
>
> Toroid is a T130-3.  Switching freq = 100khz.


18uH seems very low for 100kHz?? Does the chip datasheet
specify it should be 18uH?? I would try doubling your
windings (or even more) to bump it up to 70uH or so,
and give that a go. :o)

Yeah ok, not very "scientific" but then you did ask for
tips with the transformer design. Re blowing up the chip,
are you using a variable load? Maybe also try putting a
3w 20v zener across your DC input and/or chip, if you
have a winding reversed (hint hint) it might make lots
of volts on flyback and fry your chip. :o)
-Roman

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

2003\03\05@165736 by PicDude

flavicon
face
Roman Black scribbled:
>
> 18uH seems very low for 100kHz?? Does the chip datasheet
> specify it should be 18uH?? I would try doubling your
> windings (or even more) to bump it up to 70uH or so,
> and give that a go. :o)

Not specifically the datasheet, but their online and
standalone design tool.  The datasheet has similar
designs that call for a 1:1 transformer with a 22uh
primary.


> Yeah ok, not very "scientific" but then you did ask for
> tips with the transformer design.

True.  Fine, I'll bite.


> Re blowing up the chip,
> are you using a variable load?

No, just a fixed 150-ohm resistor across the output.
This should give me 80mA for now.


> Maybe also try putting a
> 3w 20v zener across your DC input and/or chip, if you
> have a winding reversed (hint hint) it might make lots
> of volts on flyback and fry your chip. :o)

Hmmm.... maybe you could be right.


> -Roman
>

Cheers,
-Neil.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

More... (looser matching)
- Last day of these posts
- In 2003 , 2004 only
- Today
- New search...