Shunt Voltage Reference LM431

Hammy <Ha...@hamster.ca> wrote innews:Xns9DE7AA8753CFDHammyhamsterca_at_69.16.185.247:

[snip



If you go to the onsemi folder for the NCP1200 they have a pspice model for
it with a template using a simple zener/opto feedback. Just so you know
regulation isn't going to be tight probably +/- 10% or so when you factor
in all tolerances.

Here's a screen shot of the spice template using the zener/opto. I can't
fit the whole schematic in but the relevant portions are visible.

http://i51.tinypic.com/2uo1jdg.png

This is just the provided template with the default components.I just added  
R7 for Izener.

On Sep 2, 12:39 pm, John Fields <jfie...@austininstruments.com> wrote:
On Thu, 2 Sep 2010 08:24:37 -0700 (PDT), Précis d'electronique

ee.jce...@gmail.com> wrote:
thank you, I make the desgin in PIExpert for 100 output and gives me
no error, just the same circuit, so I am more confused about that,
take a look
https://sites.google.com/site/eelabsproject/test.png
and that is the resistor of 1k, for 1mA

---
I've read through this thread a couple times and I'm completely
confused.

Do you have this?:

http://www.powerint.com/sites/default/files/product-docs/an43.pdf

Also, what more can you tell us about the transformer you have on
hand?

---
JF

yes!, well I am sorry I cant explain my doubts

I have this transformer for my 90v output, WurthElektronik designed it
for my specs. and I thought that a simple changes (resistors, caps)
could make my 90v work, I have not made a smps before but with all the
application notes around there I was just scary about the layout.

The problem so far is the TL431 (programmable zener by definition),
that can not work above 36v, the solution is, another winding for AUX
(ex 12v) or Zener-resistor as feedback, or zener for reduce voltage
and tl431, but I have not seen this configuration on ONsemi and PI


PIExpert gives me this

https://sites.google.com/site/eelabsproject/Untitled.png

Précis d'electronique <ee.jce...@gmail.com> wrote innews:9b292613-823a-4831-893b-5fef0749444b_at_m1g2000yqo.googlegroups.com:

[snip]

Sorry for the late follow-up I've been busy.

Here is an application note from PI with a 48V output showing how to use a TL431 at higher voltages With pretty well component by
component explanation.

http://www.powerint.com/sites/default/files/PDFFiles/der97.pdf

Who designed your custom transformer?

Like I said earlier you could also just regulate the primary side ie the Vcc winding if your transformer has one the output would just
be regulated by the turns ratio.

You could also just use a zener/opto for regulating the output.Where the output is approximatly regulated to Vzener + Vf of the optos
LED. I'm sure PI and Onsemi have examples of this I've seen them before just never had the need to use it when you can get a 431 for the
same price as a zener.

You could also look at no opto coupler isolated controller like the LT3748.

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1....

You would need a Vcc winding on your transformer.

What controller are you useing? What are the transformers specs? What are the output tolerance requirments ?

You may get more help if you provide more details.You've gone from an unknown Onsemi controller to now an unknown PI controller.

Is this your first SMPS?

Hammy <Ha...@hamster.ca> wrote innews:Xns9DE7AA8753CFDHammyhamsterca_at_69.16.185.247:

[snip



If you go to the onsemi folder for the NCP1200 they have a pspice model for
it with a template using a simple zener/opto feedback. Just so you know
regulation isn't going to be tight probably +/- 10% or so when you factor
in all tolerances.

Here's a screen shot of the spice template using the zener/opto. I can't
fit the whole schematic in but the relevant portions are visible.

http://i51.tinypic.com/2uo1jdg.png

This is just the provided template with the default components.I just added  
R7 for Izener.

Hammy <Ha...@hamster.ca> wrote innews:Xns9DE7AA8753CFDHammyhamsterca_at_69.16.185.247:

[snip



If you go to the onsemi folder for the NCP1200 they have a pspice model for
it with a template using a simple zener/opto feedback. Just so you know
regulation isn't going to be tight probably +/- 10% or so when you factor
in all tolerances.

Here's a screen shot of the spice template using the zener/opto. I can't
fit the whole schematic in but the relevant portions are visible.

http://i51.tinypic.com/2uo1jdg.png

This is just the provided template with the default components.I just added  
R7 for Izener.

"John Fields" <jfie...@austininstruments.com> wrote in message

news:12nv7657o0gecpin0kp91s8j0ot2q32u53_at_4ax.com...





On Thu, 2 Sep 2010 08:24:37 -0700 (PDT), Précis d'electronique
ee.jce...@gmail.com> wrote:

thank you, I make the desgin in PIExpert for 100 output and gives me
no error, just the same circuit, so I am more confused about that,
take a look
https://sites.google.com/site/eelabsproject/test.png
and that is the resistor of 1k, for 1mA

---
I've read through this thread a couple times and I'm completely
confused.

Do you have this?:

http://www.powerint.com/sites/default/files/product-docs/an43.pdf

Also, what more can you tell us about the transformer you have on
hand?

---
JF

I think he needs to stack theLM431'sto achieve Vf = 100v eg: 4lm431's
stacked and set for 25v each.

Now I have no idea if he's rectifying the transformervoltageor just
clipping the output at 100v.

Cheers

I think he needs to stack the LM431's to achieve Vf = 100v eg: 4 lm431's
stacked and set for 25v each.