[sdiy] "Zerolytics"

René Schmitz synth at schmitzbits.de
Tue May 5 15:24:12 CEST 2020


Hi Mark and all,

On 04.05.2020 12:40, mark verbos wrote:
> Is this the solution?

Maybe one, but surely not the only one.

(Apart from asking if the problem statement is accurate to begin with. 
AKA solution in search of problem...)

If one wants to raise the reliability of a PSU, then there are other 
options. For example: good thermal design, keeping Al-Electrolytics cool 
and spread current loads to as many caps (=larger area/volume) as 
feasible. After all one can (and does) parallel many Al-electrolytics, 
and lower ESR and inductance by that too.
(Up to a point, as some regulators actually need some series R for 
stability. Which goes also when you use ceramics as sole reservoir cap.)

MLCCs come with their own set of problems. Notably nonlinear behaviour 
in their dielectrics. So you have to use higher values than nominal if 
there is DC on them.

Then, apart from special types, which have worse volume effiency, they 
tend to fail short. Much like tantalums. Excessive flexing of the PCB 
can result in the ceramic cracking and possibly shorting the rails 
together. And you might not want that on the high-voltage side of a SMPS.

It is also to consider that paralleling lots of caps, can reduce the MTBF.

A well designed modular PSU, which can also be easily and quickly 
serviced or exchanged sounds to me like the better solution for creating 
a more long term reliable PSU.

Best,
  René

--
synth at schmitzbits.de
http://schmitzbits.de



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