AVR-Chat

Hi all,

I am resurecting an old project atm and I need to build a powersupply, 
it will take in an average of 120Vdc (from ~100 - 160Vdc) and provide 
regulated 24V and 5V rails. Total wattage around 60W.

I chose the uc3842 SMPS controller as the regulator. I am trying to work 
out the design of the transformer.

I am using a ferroxcube ETD34/17/11 with the 3C90 cores. I have worked 
the example in the philips UC3842 appnote ( 
moon.feld.cvut.cz/hw/philips/acrobat/8014.pdf ) Using the values of the 
EC35 core with the 3C81 core (it says a 3C8 core but I can find no info 
and believe the last digit is missing)

I am getting very strange results in my calculations and as transformer 
theory is not my area, I need some help lol

TIA

Kat.
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----- Original Message ----- 

From: Kathy Quinlan
To: AVR-Chat@yahoogroups.com
Sent: Friday, January 21, 2005 1:51 PM
Subject: [AVR-Chat] OT Magnetics design problems


Hi all,

I am resurecting an old project atm and I need to build a powersupply,
it will take in an average of 120Vdc (from ~100 - 160Vdc) and provide
regulated 24V and 5V rails. Total wattage around 60W.

I chose the uc3842 SMPS controller as the regulator. I am trying to work
out the design of the transformer.

I am using a ferroxcube ETD34/17/11 with the 3C90 cores. I have worked
the example in the philips UC3842 appnote (
moon.feld.cvut.cz/hw/philips/acrobat/8014.pdf ) Using the values of the
EC35 core with the 3C81 core (it says a 3C8 core but I can find no info
and believe the last digit is missing)

I am getting very strange results in my calculations and as transformer
theory is not my area, I need some help lol


This is very useful: 
http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/smps_e.html

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller



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Kathy Quinlan wrote:
> Hi all,
> 
> I am resurecting an old project atm and I need to build a powersupply, 
> it will take in an average of 120Vdc (from ~100 - 160Vdc) and provide 
> regulated 24V and 5V rails. Total wattage around 60W.
> 
> I chose the uc3842 SMPS controller as the regulator. I am trying to work 
> out the design of the transformer.
> 
> I am using a ferroxcube ETD34/17/11 with the 3C90 cores. I have worked 
> the example in the philips UC3842 appnote ( 
> moon.feld.cvut.cz/hw/philips/acrobat/8014.pdf ) Using the values of the 
> EC35 core with the 3C81 core (it says a 3C8 core but I can find no info 
> and believe the last digit is missing)
> 
> I am getting very strange results in my calculations and as transformer 
> theory is not my area, I need some help lol
> 
> TIA
> 
> Kat.

99% of the energy is stored in the air gap and for a flyback
supply you must have one. Then you must know the core cross-sectional
area, the saturation flux density (0.3 Tesla is usual), length
of the primary pulse, and flyback voltage across the transistor.
 From that, you can determine the turns-per-volt. However, thermal
problems limit how small the transformer can be, and winding
capacitance limits how high the frequency can be.

why a new power source? i'm using some PC sources, if
this are modified you can use in any output you need.

in the net you have some modification to this to make
a comminucation power source, general this are about
13,8V and 15 Amps or more.

The only thing you need to do is change the secondary
wending of the power transformer and chage the value
of the reference resistor of the TL494.

For you aplication notes this, the 5V outlet have 15
or 20 Amps and the 12V section have 5 or less.

If you don't need much than a few amperes i'm think
only changing the 12V wending you can have 24V and 2
or 3 amperes.

this power sources have about 300W to 450Watts.

Best Regards
Frank

 --- Russell Shaw <rjshaw@netspace.net.au> escribió: 
> 
> Kathy Quinlan wrote:
> > Hi all,
> > 
> > I am resurecting an old project atm and I need to
> build a powersupply, 
> > it will take in an average of 120Vdc (from ~100 -
> 160Vdc) and provide 
> > regulated 24V and 5V rails. Total wattage around
> 60W.
> > 
> > I chose the uc3842 SMPS controller as the
> regulator. I am trying to work 
> > out the design of the transformer.
> > 
> > I am using a ferroxcube ETD34/17/11 with the 3C90
> cores. I have worked 
> > the example in the philips UC3842 appnote ( 
> > moon.feld.cvut.cz/hw/philips/acrobat/8014.pdf )
> Using the values of the 
> > EC35 core with the 3C81 core (it says a 3C8 core
> but I can find no info 
> > and believe the last digit is missing)
> > 
> > I am getting very strange results in my
> calculations and as transformer 
> > theory is not my area, I need some help lol
> > 
> > TIA
> > 
> > Kat.
> 
> 99% of the energy is stored in the air gap and for a
> flyback
> supply you must have one. Then you must know the
> core cross-sectional
> area, the saturation flux density (0.3 Tesla is
> usual), length
> of the primary pulse, and flyback voltage across the
> transistor.
>  From that, you can determine the turns-per-volt.
> However, thermal
> problems limit how small the transformer can be, and
> winding
> capacitance limits how high the frequency can be.
> 
> 
>  
> Yahoo! Groups Links
> 
> 
>     AVR-Chat-unsubscribe@yahoogroups.com
> 
>  
> 
> 
> 
>  


	

	
		
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Franco wrote:

> why a new power source? i'm using some PC sources, if
> this are modified you can use in any output you need.
> 
> in the net you have some modification to this to make
> a comminucation power source, general this are about
> 13,8V and 15 Amps or more.
> 
> The only thing you need to do is change the secondary
> wending of the power transformer and chage the value
> of the reference resistor of the TL494.
> 
> For you aplication notes this, the 5V outlet have 15
> or 20 Amps and the 12V section have 5 or less.
> 
> If you don't need much than a few amperes i'm think
> only changing the 12V wending you can have 24V and 2
> or 3 amperes.
> 
> this power sources have about 300W to 450Watts.
> 
> Best Regards
> Frank

I tried that, but the input voltage requirements were the problem :(

A 120Vac powersupply uses a voltage doubler to up the DC to ~340Vdc, I 
only have a nominal supply of 120Vdc to play with.

Regards,

Kat.

-- 
---------------------------------------------------------------
K.A.Q. Electronics	Website: www.kaqelectronics.dyndns.org
IM: Yahoo: PinkyDwaggy  MSN: katinka@kaqelectronics.dyndns.org
For Everything Electronics     Phone: 0419 923 731
---------------------------------------------------------------	


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Hummm, it's a problem becose you have a big Vcc to get
down to 24Vcc, the angle of the square signal is too
small i'm think.

Other solution is use a transformer and modulate the
input of this to obtain the 24Vcc.

Why don't use a power souce from a Tv or VCR? that
power sources don't use a doubler becose this are
power less than a Pc.

Find some Tv or VCR manual and copy the input stage of
the power source, buy the same transformer and then
using a scope try to adjust the winding for the rigth
angle for the 24Vcc, this sources are realy nice
becose the tv's power stage and the modulator are
integrated in only one IC.

Writing this my light switch on!, in my work we use an
multi-voltaje power sources, this devices are
programable voltaje output, come with a lot of plugs,
each are a resistor calibrated for each voltaje, and..
this source is a switching and have 3 or more Amps.

Ok is for a AC outlet but inside i hope use a
rectifier, is the same if you want to use in a DC
outlet, and this deviced are too auto-input switched,
don't mare if you have 240Vac or 100Vac!

Regards 
Frank




 --- Kathy Quinlan
<kat-yahoo@kaqelectronics.dyndns.org> escribió: 
> 
> Franco wrote:
> 
> > why a new power source? i'm using some PC sources,
> if
> > this are modified you can use in any output you
> need.
> > 
> > in the net you have some modification to this to
> make
> > a comminucation power source, general this are
> about
> > 13,8V and 15 Amps or more.
> > 
> > The only thing you need to do is change the
> secondary
> > wending of the power transformer and chage the
> value
> > of the reference resistor of the TL494.
> > 
> > For you aplication notes this, the 5V outlet have
> 15
> > or 20 Amps and the 12V section have 5 or less.
> > 
> > If you don't need much than a few amperes i'm
> think
> > only changing the 12V wending you can have 24V and
> 2
> > or 3 amperes.
> > 
> > this power sources have about 300W to 450Watts.
> > 
> > Best Regards
> > Frank
> 
> I tried that, but the input voltage requirements
> were the problem :(
> 
> A 120Vac powersupply uses a voltage doubler to up
> the DC to ~340Vdc, I 
> only have a nominal supply of 120Vdc to play with.
> 
> Regards,
> 
> Kat.
> 
> -- 
>
---------------------------------------------------------------
> K.A.Q. Electronics	Website:
> www.kaqelectronics.dyndns.org
> IM: Yahoo: PinkyDwaggy  MSN:
> katinka@kaqelectronics.dyndns.org
> For Everything Electronics     Phone: 0419 923 731
>
---------------------------------------------------------------
> 
> 
> 
> -- 
> No virus found in this outgoing message.
> Checked by AVG Anti-Virus.
> Version: 7.0.300 / Virus Database: 265.7.1 - Release
> Date: 19/01/2005
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
>     AVR-Chat-unsubscribe@yahoogroups.com
> 
>  
> 
> 
> 
>  

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