I'm confident you've misunderstood or misread their application note.
+ ----+----+------+----+----+----+----+--->On Mon, 15 Oct 2007 15:22:26 -0700, Tim Wescott <tim@seemywebsite.com
wrote:
Yes, you can use the itty bitty caps. Verify their current ratings if
you can -- some of what makes the spendy caps spendy is the AC ripple
current they can deliver without overheating.
I'm confused. This ripple current is surely what I want the caps to
absorb, not to deliver, or am I on the wrong tack as usual?
Anyways, it seems that the increased surface area of many small caps
over one big one would favour heat dissipation. Just depends on what
you can get your hands on for reasonable moolah. Seventy-five cents
for 4700uF seems pretty good value?
You can parallel as many caps as you want, for more capacity and
current. 50V isn't enough for a 36V supply.
Someone jumped on me for suspecting this
You can connect caps in
series as long as you use some balance resistors. You ought to have a
ballast resistor on the supply anyway, to make sure the caps discharge
by themselves
Is this really necessary for 36V? Or is safety not the only reason to
discharge caps?
-- you can combine the ballast and balance functions by
ballasting each capacitor bank separately.
How does the balance work? What value and where would you put these
resistors?
Absolutely not. They are entirely passive components. They get charged up every 10msEeyore wrote:
spamfree@spam.heaven wrote:
I'm confused. This ripple current is surely what I want the caps to
absorb, not to deliver, or am I on the wrong tack as usual?
The caps do both. They 'absorb' the current as the cap is recharged at the peak
of the input voltage from the transformer/rectifier and then deliver it to the
load when that input is providing no more charge. You see the
transformer/rectifier deleivers the input power in 'blips' every 10ms and the
caps job ios to smooth it out.
Yes, I understand the buffering effect, but had not thought of the
caps as producing their own ripple.
And you can avoid the issue entirely by accepting that 50V caps (with a 63V
Page 7. jack
No, I thought I was asking a question about something I know little
Umm, can you not mention which components in those circuits are more
"This produces a pulsing DC. the pulses are at twice the frequency of
From the formula on page 9 of the Evox Rifa article.So who is the grade one idiot between you and the Evox Rifa folk whose
formula tells me I need only 10,800 uF - less than half your
calculation?
Where do you get 10,800 uF from ?
And tell me, what percentage of ripple suppression were you aiming at
So you don't like NEMA? I thought it was fairly relevant to US
OK, thanks for that. Just out of curiosity, what actually filters out
Thanks so much for that, Ed. most useful, jack
Must be my misunderstanding of the word "deliver". I get the sense ofspamfree@spam.heaven wrote:
Eeyore wrote:
spamfree@spam.heaven wrote:
I'm confused. This ripple current is surely what I want the caps to
absorb, not to deliver, or am I on the wrong tack as usual?
The caps do both. They 'absorb' the current as the cap is recharged at the peak
of the input voltage from the transformer/rectifier and then deliver it to the
load when that input is providing no more charge. You see the
transformer/rectifier deleivers the input power in 'blips' every 10ms and the
caps job ios to smooth it out.
Yes, I understand the buffering effect, but had not thought of the
caps as producing their own ripple.
Absolutely not. They are entirely passive components. They get charged up every 10ms
and then they release some of their charge during the rest of the mains half cycle.
That's where the ripple comes from, from the regular charge and discharge of the
caps.
Wow, worse than Sadaam Hussein, perhaps?
Well where else would transients come from in this situation?
Surely that depends on how much energy is in the mains transients.
Why? Perhaps he believes the controllers (which he is familiar with,
As I thought. It refers to transients on the mains. Such transients won't
There's the crazy bit. 100mV is an insane target for ripple voltage here.
Yes, a cookbook formula. I prefer working with the raw data.
I wasn't working with any 'percentage' that's not a particularly useful measure. I was
The sheer size of the reservoir caps just 'absorb' the transients.
It's not a case of whether I like it or not. It has no authority or relevance outside the borders
Most US regs have typically been rather different to International ones, although UL is now
You'd have to look for yourself but I do know that wherever the IEC rates power in all the
The caps do no manufacturing, they simply store charge and deliver it on demand.Eeyore wrote:
spamfree@spam.heaven wrote:
Eeyore wrote:
spamfree@spam.heaven wrote:
I'm confused. This ripple current is surely what I want the caps to
absorb, not to deliver, or am I on the wrong tack as usual?
The caps do both. They 'absorb' the current as the cap is recharged at the peak
of the input voltage from the transformer/rectifier and then deliver it to the
load when that input is providing no more charge. You see the
transformer/rectifier deleivers the input power in 'blips' every 10ms and the
caps job ios to smooth it out.
Yes, I understand the buffering effect, but had not thought of the
caps as producing their own ripple.
Absolutely not. They are entirely passive components. They get charged up every 10ms
and then they release some of their charge during the rest of the mains half cycle.
That's where the ripple comes from, from the regular charge and discharge of the
caps.
Must be my misunderstanding of the word "deliver". I get the sense of
"manufacture and then pass on", but my dictionary states otherwise,
and that is to merely "pass along". All's clear now, thanks for your
persistence, jack