Re: failure of the low-ESR electrolytic capacitor in second winding

On Fri, 30 Nov 2007 19:36:06 +0000, Eeyore
<rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:



legg wrote:

Eeyore wrote:
legg wrote:
Eeyore wrote:
Winfield wrote:

The ripple current is equal to your load current.

Win !

Wash your mouth out.
This is a reasonably assumed limit.

In fact it's always less.

Utter and complete nonsense.


It's the winding rms current that exceeds the output current.

Time for a refresher, buddy.

You first sunshine.

What I stated is 100% correct.

I'm staggered quite frankly that so few people here know how to design something
as simple as a PSU competently.

I mean SERIOUSLY ! Not to know how to determine the required ripple current
rating of a capacitor ? Bizarre.

Find refresher penance attached on a.b.s.e.

Exactly.

The ripple current is NOT the same as the load current.

Legg's calculations, and mine, show that for the discontinuous conduction
case with constant output current, they are the same (value) for a duty
cycle somewhere between 60% and 70%.

It's very strongly affected by the conduction angle/period.

So it is. And, in fact, it's so strongly affected, that below a certain
duty cycle, the capacitor ripple current is greater than the output
current, and above that duty cycle, the capacitor ripple current is less
than the output current.


Graham

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