[sdiy] Snubber Capacitors

[ASSI]

On Thursday 02 February 2012, 19:05:14, Stewart Pye wrote:
> I'm designing a power supply for my synth. I want to put snubber caps
> for the bridge rectifier on the PCB in case I find a need for them, but
> am not sure whether to have one across each diode, or just one across
> the bridge. Also sometimes a series RC circuit is used. Would it be best
> to include room for a resistor as well?

If you do need a snubber, it has to be RC to be effective, each diode will 
need one and you will have to take into account that the smoothing 
capacitance will reduce over the lifetime off the supply (by 30% is a good 
guess).

You didn't say how much current and voltage you are designing it for, but it 
would probably be better to select rectifier diodes and dimension the 
transformer and smoothing caps correctly so that you don't need a snubber in 
the first place.  Excessive ringing at current levels below some 10A is 
usually a sign of misguidedly overdimensioned components (resulting in too 
high quality factor of the LC tank) and a harbinger of more problems with 
that design.  BTW, the smoothing caps after a rectifier bridge are one of 
those places where too low ESR is counterproductive.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Samples for the Waldorf Blofeld:
http://Synth.Stromeko.net/Downloads.html#BlofeldSamplesExtra