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Précis d'electronique
Guest
Mon Aug 30, 2010 9:43 pm
Hi, I would like to know if someone knows a voltage reference like the
LM431 but for Vf 100v max
Do you know how to calculate the Resistor for the opto's LED? is it
just a matter of mA? for example in this schematic (www.onsemi.com/
pub_link/Collateral/AND8038-D.PDF) (page 1) if my output is 50v what
is the value of R3?
thank you
Hammy
Guest
Mon Aug 30, 2010 9:53 pm
Précis d'electronique <ee.jcesar_at_gmail.com> wrote in news:37a921c4-ce51-
442b-a313-42592f131814_at_q2g2000yqq.googlegroups.com:
Quote:
Hi, I would like to know if someone knows a voltage reference like the
LM431 but for Vf 100v max
Do you know how to calculate the Resistor for the opto's LED? is it
just a matter of mA? for example in this schematic (www.onsemi.com/
pub_link/Collateral/AND8038-D.PDF) (page 1) if my output is 50v what
is the value of R3?
thank you
Go to the NCP1200 product folder.
http://www.onsemi.com/PowerSolutions/product.do?id=NCP1200
Look under Technical Information, click on Design & Development Tools.
You will find excel based spreadsheets for calculating all components for a
basic flyback called "Flyback Current Mode Loop Compensation Design
Worksheet". They also have spice models with transient and AC templates.
Why do you need a 100Vf refrence?
whit3rd
Guest
Mon Aug 30, 2010 11:02 pm
On Aug 30, 11:43 am, Précis d'electronique <ee.jce...@gmail.com>
wrote:
Quote:
Hi, I would like to know if someone knows a voltage reference like the
LM431 but for Vf 100v max
The LM431 wants a few mA to stabilize, at 100V you'd be dissipating
a lot of power if you used that design. The old IC regulators, like
LM305 and uA723, can be configured with external components
to do this kind of thing. They need 10V or so minimum for their
internal power, you might want to run 'em from low voltage power
and just put the output device on the 100V.
Précis d'electronique
Guest
Tue Aug 31, 2010 12:07 am
On Aug 30, 3:53 pm, Hammy <Ha...@hamster.ca> wrote:
Quote:
Précis d'electronique <ee.jce...@gmail.com> wrote in news:37a921c4-ce51-
442b-a313-42592f131...@q2g2000yqq.googlegroups.com:
Hi, I would like to know if someone knows a voltage reference like the
LM431 but for Vf 100v max
Do you know how to calculate the Resistor for the opto's LED? is it
just a matter of mA? for example in this schematic (www.onsemi.com/
pub_link/Collateral/AND8038-D.PDF) (page 1) if my output is 50v what
is the value of R3?
thank you
Go to the NCP1200 product folder.
http://www.onsemi.com/PowerSolutions/product.do?id=NCP1200
Look under Technical Information, click on Design & Development Tools.
You will find excel based spreadsheets for calculating all components for a
basic flyback called "Flyback Current Mode Loop Compensation Design
Worksheet". They also have spice models with transient and AC templates.
Why do you need a 100Vf refrence?
Hi, thank you
My output is 90v and 0.100A, I already calculated R5,R6,R4 and I have
the transformer but I get 5 volts in the output (in a squared signal)
and I cant find a LM431 for my reference.
Hammy
Guest
Tue Aug 31, 2010 12:16 am
Précis d'electronique <ee.jcesar_at_gmail.com> wrote in
news:c07a80ed-590c-4dc8-b447-918eeb9f9bf1_at_i31g2000yqm.googlegroups.com:
Quote:
Hi, thank you
My output is 90v and 0.100A, I already calculated R5,R6,R4 and I have
the transformer but I get 5 volts in the output (in a squared signal)
and I cant find a LM431 for my reference.
Where did you get the transformer? You know you cant use just any old
transformer and that a flyback uses coupled inductors for energy transfer.
You can just use a zener/opto to feedback like this.
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/an25.pdf
You do know that you need a rectifier on the secondary with a capacitor?
You could also regulate the Vcc winding and just have your output voltage
regulated by the turns ratio.This woukdnt require an opto coupler but
regulation wouldnt be tight depends on your requirments.
Tauno Voipio
Guest
Tue Aug 31, 2010 8:58 pm
Précis d'electronique wrote:
Quote:
Hi, I would like to know if someone knows a voltage reference like the
LM431 but for Vf 100v max
OA2 or VR-105? You can google for them.
--
Tauno Voipio, OH2UG
Précis d'electronique
Guest
Tue Aug 31, 2010 9:05 pm
On Aug 30, 6:16 pm, Hammy <Ha...@hamster.ca> wrote:
Quote:
Précis d'electronique <ee.jce...@gmail.com> wrote innews:c07a80ed-590c-4dc8-b447-918eeb9f9bf1_at_i31g2000yqm.googlegroups.com:
Hi, thank you
My output is 90v and 0.100A, I already calculated R5,R6,R4 and I have
the transformer but I get 5 volts in the output (in a squared signal)
and I cant find a LM431 for my reference.
Where did you get the transformer? You know you cant use just any old
transformer and that a flyback uses coupled inductors for energy transfer..
You can just use a zener/opto to feedback like this.
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/an25.pdf
You do know that you need a rectifier on the secondary with a capacitor?
You could also regulate the Vcc winding and just have your output voltage
regulated by the turns ratio.This woukdnt require an opto coupler but
regulation wouldnt be tight depends on your requirments.
HI, Wurth Elektronik gave me the transformer (custom) for 90v
what rectifier? the D2 on the schematic?
Could you help me to calculate the values for the opto/zener feedback?
that would be a 75 volt zener, a 1k resistor in parallel to the LED ,
or to the Rled too?
thank you
ehsjr
Guest
Thu Sep 02, 2010 6:25 am
Précis d'electronique wrote:
Quote:
On Aug 30, 6:16 pm, Hammy <Ha...@hamster.ca> wrote:
Précis d'electronique <ee.jce...@gmail.com> wrote innews:c07a80ed-590c-4dc8-b447-918eeb9f9bf1_at_i31g2000yqm.googlegroups.com:
Hi, thank you
My output is 90v and 0.100A, I already calculated R5,R6,R4 and I have
the transformer but I get 5 volts in the output (in a squared signal)
and I cant find a LM431 for my reference.
Where did you get the transformer? You know you cant use just any old
transformer and that a flyback uses coupled inductors for energy transfer.
You can just use a zener/opto to feedback like this.
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/an25.pdf
You do know that you need a rectifier on the secondary with a capacitor?
You could also regulate the Vcc winding and just have your output voltage
regulated by the turns ratio.This woukdnt require an opto coupler but
regulation wouldnt be tight depends on your requirments.
HI, Wurth Elektronik gave me the transformer (custom) for 90v
what rectifier? the D2 on the schematic?
Could you help me to calculate the values for the opto/zener feedback?
that would be a 75 volt zener, a 1k resistor in parallel to the LED ,
or to the Rled too?
thank you
Not sure, but I think you're trying to do this:
---[L2]-----+---> +90V
|
|
\__|__ [R5]
/ \ \ |
/___\--------+
| |
| [R6]
| |
+----------+
|
[1N5374] 75V, 5W Zener diode
|
Gnd ----+
You compute the R5 and R6 values as you did before, except
that, with the zener added, you base the computation on
Vout - Vzener. With Vzener = 75, then you base on 15 volts
instead of 90 (Vout). Note that regulation will not be as crisp
because of the addition of the 75V zener - but without it
the TL431 max V is exceeded. The datasheet for a 5W 75V
zener shows a range from 71.25 to 78.75 volts, at 20 mA.
That means your output voltage could vary +/- 3.75 volts
from nominal. A different current would result in a different
(likely wider) range. The the 20 mA test current on the datasheet,
the zener would be dissipating 1.5 watts.
It may be that the advantages of the 431 are swamped by the
"mushyness" of the zener - depends on what your output
voltage requirements are.
I don't know what you are referring to when you mention
"a 1k resistor in parallel to the LED , or to the Rled too? "
Ed
ehsjr
Guest
Thu Sep 02, 2010 5:54 pm
Précis d'electronique wrote:
Quote:
On Sep 2, 12:25 am, ehsjr <eh...@nospamverizon.net> wrote:
Précis d'electronique wrote:
On Aug 30, 6:16 pm, Hammy <Ha...@hamster.ca> wrote:
Précis d'electronique <ee.jce...@gmail.com> wrote innews:c07a80ed-590c-4dc8-b447-918eeb9f9bf1_at_i31g2000yqm.googlegroups.com:
Hi, thank you
My output is 90v and 0.100A, I already calculated R5,R6,R4 and I have
the transformer but I get 5 volts in the output (in a squared signal)
and I cant find a LM431 for my reference.
Where did you get the transformer? You know you cant use just any old
transformer and that a flyback uses coupled inductors for energy transfer.
You can just use a zener/opto to feedback like this.
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/an25.pdf
You do know that you need a rectifier on the secondary with a capacitor?
You could also regulate the Vcc winding and just have your output voltage
regulated by the turns ratio.This woukdnt require an opto coupler but
regulation wouldnt be tight depends on your requirments.
HI, Wurth Elektronik gave me the transformer (custom) for 90v
what rectifier? the D2 on the schematic?
Could you help me to calculate the values for the opto/zener feedback?
that would be a 75 volt zener, a 1k resistor in parallel to the LED ,
or to the Rled too?
thank you
Not sure, but I think you're trying to do this:
---[L2]-----+---> +90V
|
|
\__|__ [R5]
/ \ \ |
/___\--------+
| |
| [R6]
| |
+----------+
|
[1N5374] 75V, 5W Zener diode
|
Gnd ----+
You compute the R5 and R6 values as you did before, except
that, with the zener added, you base the computation on
Vout - Vzener. With Vzener = 75, then you base on 15 volts
instead of 90 (Vout). Note that regulation will not be as crisp
because of the addition of the 75V zener - but without it
the TL431 max V is exceeded. The datasheet for a 5W 75V
zener shows a range from 71.25 to 78.75 volts, at 20 mA.
That means your output voltage could vary +/- 3.75 volts
from nominal. A different current would result in a different
(likely wider) range. The the 20 mA test current on the datasheet,
the zener would be dissipating 1.5 watts.
It may be that the advantages of the 431 are swamped by the
"mushyness" of the zener - depends on what your output
voltage requirements are.
I don't know what you are referring to when you mention
"a 1k resistor in parallel to the LED , or to the Rled too? "
Ed
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
Ok. The 1K resistor is not a problem. The circuit as shown at the
url you provided is for 5 or 12 volts and is not a problem at those
voltages, but at 100 volts it is. The TL431 can't handle that much
voltage, as you have said. Its max rating is 37 volts. I thought
that was why you mentioned the 75V zener - to keep the voltage
that the 431 sees well below its maximum rating.
In any event, the circuit as drawn at the site you mentioned won't
work for your 100 volt requirement. There's nothing to protect the
431 from overvoltage - all you'll do is burn it out.
Ed
Précis d'electronique
Guest
Thu Sep 02, 2010 6:24 pm
On Sep 2, 12:25 am, ehsjr <eh...@nospamverizon.net> wrote:
Quote:
Précis d'electronique wrote:
On Aug 30, 6:16 pm, Hammy <Ha...@hamster.ca> wrote:
Précis d'electronique <ee.jce...@gmail.com> wrote innews:c07a80ed-590c-4dc8-b447-918eeb9f9bf1_at_i31g2000yqm.googlegroups.com:
Hi, thank you
My output is 90v and 0.100A, I already calculated R5,R6,R4 and I have
the transformer but I get 5 volts in the output (in a squared signal)
and I cant find a LM431 for my reference.
Where did you get the transformer? You know you cant use just any old
transformer and that a flyback uses coupled inductors for energy transfer.
You can just use a zener/opto to feedback like this.
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/an25.pdf
You do know that you need a rectifier on the secondary with a capacitor?
You could also regulate the Vcc winding and just have your output voltage
regulated by the turns ratio.This woukdnt require an opto coupler but
regulation wouldnt be tight depends on your requirments.
HI, Wurth Elektronik gave me the transformer (custom) for 90v
what rectifier? the D2 on the schematic?
Could you help me to calculate the values for the opto/zener feedback?
that would be a 75 volt zener, a 1k resistor in parallel to the LED ,
or to the Rled too?
thank you
Not sure, but I think you're trying to do this:
---[L2]-----+---> +90V
|
|
\__|__ [R5]
/ \ \ |
/___\--------+
| |
| [R6]
| |
+----------+
|
[1N5374] 75V, 5W Zener diode
|
Gnd ----+
You compute the R5 and R6 values as you did before, except
that, with the zener added, you base the computation on
Vout - Vzener. With Vzener = 75, then you base on 15 volts
instead of 90 (Vout). Note that regulation will not be as crisp
because of the addition of the 75V zener - but without it
the TL431 max V is exceeded. The datasheet for a 5W 75V
zener shows a range from 71.25 to 78.75 volts, at 20 mA.
That means your output voltage could vary +/- 3.75 volts
from nominal. A different current would result in a different
(likely wider) range. The the 20 mA test current on the datasheet,
the zener would be dissipating 1.5 watts.
It may be that the advantages of the 431 are swamped by the
"mushyness" of the zener - depends on what your output
voltage requirements are.
I don't know what you are referring to when you mention
"a 1k resistor in parallel to the LED , or to the Rled too? "
Ed
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
John Fields
Guest
Thu Sep 02, 2010 6:39 pm
On Thu, 2 Sep 2010 08:24:37 -0700 (PDT), Précis d'electronique
<ee.jcesar_at_gmail.com> wrote:
Quote:
---
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
Hammy
Guest
Thu Sep 02, 2010 9:45 pm
Précis d'electronique <ee.jcesar_at_gmail.com> wrote in
news: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,C1113,P112210
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
Guest
Thu Sep 02, 2010 10:28 pm
Hammy <Hammy_at_hamster.ca> wrote in
news:Xns9DE7AA8753CFDHammyhamsterca_at_69.16.185.247:
[snip
Quote:
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.
Martin Riddle
Guest
Thu Sep 02, 2010 11:25 pm
"John Fields" <jfields_at_austininstruments.com> wrote in message
news:12nv7657o0gecpin0kp91s8j0ot2q32u53_at_4ax.com...
Quote:
I think he needs to stack the LM431's to achieve Vf = 100v eg: 4 lm431's
stacked and set for 25v each.
Now I have no idea if he's rectifying the transformer voltage or just
clipping the output at 100v.
Cheers
Précis d'electronique
Guest
Thu Sep 02, 2010 11:33 pm
On Sep 2, 12:39 pm, John Fields <jfie...@austininstruments.com> wrote:
Quote:
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
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