Re: [EE] solid aluminum caps on 60hz

Hi Russell,

Interesting datapoint - in my work on the EMC book, I did experiments on
RFI from ordinary rectifiers. I was unable to generate any! I was able to
make big reverse recovery spikes but the dI/dt was too slow to produce
harmonics high enough to be radiated to any significant degree with
reasonable wire lengths. I had heard of this problem before but not
actually experienced it in line-frequency devices. Have you seen it "in the
wild"?

Sean


On Thu, May 15, 2025 at 3:13 AM RussellMc <[email protected]> wrote:

> On Thu, 15 May 2025 at 12:11, madscientistatlarge <
> [email protected]> wrote:
>
> > I'm building a small (2A 12v) power supply off of a transfomer so 60Hz.
> > Is using the solid caps a problem?  I understand they have a reduced
> > impediance and am worried about the power on current initially charging
> the
> > cap and during each half cycle when the caps charge back up.  Thank you.
> >
> > Peripheral but some relevance.
>
>
> Placing a series "spreading resistor" between the rectifier output and the
> filter capacitors will increase the conduction angle of the diodes. This
> reduces peak current and  also reduces RFI from the rectifiers which do not
> switch so sharply.
>
> The resistor dissipates some energy and drops peak voltage. It's value
> wants to be small enough to not reduce available output at target voltage.
>
>
>
>                        Russell
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