MS20. Now PSU design

[Tony Allgood]

Ingo wrote:

> IMHO it's better to have the common ground point close to the
smoothing
> cap rather than to the transformer/rectifier. The cleanest DC (least
> ripple) before regulation is across the cap's terminals. The
connection
> between the cap and the transformer/rectifier carries heavy ripple
> current and you'll always have some voltage drop across this
connection
> no matter how thick it is.

Absolutely correct. I wasn't thinking. This is a much better way to
reduce line ripple to your regulators. Mind you, it gets a bit more
complicated if you have two or more caps in parallel. 

Whilst on this topic, is anyone in favour of putting 100n caps across
the rectifiers to reduce reverse recovery spikes? It does work, but is
it worth it? I don't know. I've also heard that it not a great idea to
put smaller caps in parallel with big smoothers as it can create a
parallel LCR with the smoother's inductance. Not sure about this one
either.

I have a big problem with 100Hz noise on my studio 150+150 amp. Maplin
MOSFET kit. I've tried every possible combination of earthing there is,
and the noise is still there. It only has about 200mV of 100Hz, it's a
55volt supply, but it still audible on my speakers. Some things are
left to try us!


Tony Allgood.

Penrith, Cumbria, UK     

e-mail: oakley at enterprise.net

'I may live in the middle of nowhere, but the views are nice'