SMPS(flyback question)

[[email protected]]

A similar one:
http://focus.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slup084&fileType=pdf

Thanks for the links John.
Looks like just the thing to fill some "big" gaps in my knowledge!!
Maybe I'll take the wife out for sushi , and then get stuck in :0 )
Thanks again.
Cheers
Rob

 

[Genome]

Hi to all.
I have a quick question about a flyback convertor I'm working on.
Its 220V ac in 13.7V dc out. I'm using a uc3842 contriller chip.
At 60W ( about 4.5A) load everything seems good. At about 80 to 100W
the cct starts to
get unstable. I can hear a hissing sound etc. Looking at the switching
FET's
drain waveform I can see that the frequency is changing ( hopping
around). I have found that if
I keep the output diode(BYV32) cool (with a fan) then the stability
problems
go away. The diode is mounted on a small heatsink. At 50W the heatsink
is just to
hot to touch for more than say 5-10s( probable about 60 deg c , hav'nt
measured). Obviously at higher currents it gets a lot hotter.Why would
the diode temperature cause the instability at higher temperatures?
The obvious solution is to use a bigger heatsink , which I will be
doing , but I still would like to know whats happening at higher temps
to cause instability.
I am far from an expert with SMPS's , so any pointers/help will be
appreciated.
Hope I have not been to vague.
Cheers
Rob

Took a bit of time but you might like to have a look at....

http://genomerics.org/seegon/seegon.html

DNA

 

[[email protected]]

Took a bit of time but you might like to have a look at....

http://genomerics.org/seegon/seegon.html

DNA

WOW!!
That must have taken ages. Lots there for me to go through.
Thanks a bunch.
Rob

 

[Genome]

WOW!!
That must have taken ages. Lots there for me to go through.
Thanks a bunch.
Rob

Don't forget, if you have LTspice then you can download the simulation files
by clicking on the LT logo beneath the circuit pictures. Then you can have a
play.

DNA