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sPuDd

Senior Member

Joined: 10/07/2007
Location: Australia
Posts: 251

Posted: 12:47am 26 Jun 2009

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oztules said Spud,s circuit needs soft start, as there is no over current surge protection apparently.

Bang Baby Bang !!

I will add current limiting, once I have the unit working properly. But for now its just one less thing to worry about.

sPuDd..

It should work ...in theory

Cornelius

Newbie

Joined: 26/12/2008
Location: Norway
Posts: 27

Posted: 07:40am 26 Jun 2009

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Ok folks; i'm feeling a bit chicken today, so i'm going to se if i can dig up another that works guaranteed, (i'll test it before i start the slaughter) and start over.

Maybe i can find one without bent component legs too...

Dinges
Senior Member

Joined: 04/01/2008
Location: Albania
Posts: 510

Posted: 12:58am 27 Jun 2009

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[quote=Cornelius]Maybe i can find one without bent component legs too[/quote]
Smooth seas do not make skillful sailors....

[quote=Oztules]I'm not that excited about the soft start on pin 4. With the current limiting in place,... you don't need it. There is no surge beyond the current limit set.... so nothing to protect against..... I just ground it. [/quote]
Oztules, I figure the softstart can't do harm? As I understand it, it's intended to deal with the transients as the PSU switches states from 'off' to 'on'. Where voltages and signals haven't stabilized yet and before the feedback loops have stabilized. I figure that as long as these loops aren't running stable that you can't rely on them to protect the PSU? Hence the benefit of having a softstart to protect things during this inital unstable situation?

As a sidenote to this and the other thread and something which I haven't seen mentioned yet: grounding pin 16 of the TL494 may not be trivial. I recall one particular PSU where the current control wasn't working properly till I grounded pin 16 via a separate wire to another place of the PCB (where all the black wires are soldered to the PCB); this single modification changed the behaviour of that PSU from nasty to perfectly behaved (w.r.t. current control).

Peter.

Cornelius

Newbie

Joined: 26/12/2008
Location: Norway
Posts: 27

Posted: 10:04am 27 Jun 2009

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Now, i'm an old tallship sailor, so i'll manage...

Here's my new lamb for the slaughter:

I put some more detailed pictures in my gallery

This one have a KA7500B on a daughterboard, and no optocoupler back to the HV side. All in all; a much neater layout.

Edit:
And this one works initially too!

I fired up the pc it powered before starting to disassemble it...

Edited by Cornelius 2009-06-28

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