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gootee
diyAudio Member

Join Date: Nov 2006
Location: Indiana
Quote:
 Originally Posted by fas42 Bit of a thread to digest, so I'll wind up my energy to chomp my way through it later on. At a quick glance, I can see that people get into trouble by ignoring the lead and connections' inductances; this will kill any benefit of bypassing, possibly make it worse, unless it's done precisely where it's needed. Rule of thumb, the smaller the cap the closer it has to be where the HF noise is the actual problem. In general, ESR is relatively constant over the range that the cap deals with, it's the impedance that starts capacitive, momentarily becomes resistive, and then remains forever inductive, with rising frequency. Frank
I was going to respectfully disagree, and was going to say the following:

----------------

ESR varies directly with frequency. (It is part of the impedance, too).

DF = TAN(DELTA)@f = 2Pi*f*C*ESR(f)

The tan(delta), or DF (dissipation factor), varies by only about 100%, usually. So we can use that to estimate ESR versus frequency, with

ESR(f) = tan(delta)/(2 Pi f C)

----------------

But then I looked at:

Cornell Dubilier Electronics

which gives something like this:

http://www.diyaudio.com/forums/attac...ps-cdejava.jpg

And so another long-held misconception bites the dust.

Thank you. I just wish I had noticed that, years ago, before it cost me so much extra effort when doing spice modeling and simulation. (But the capacitor spice models from that CDE java applet are coool.)

Cheers,

Tom

P.S.

I'm definitely with you on the inductance issues, and also for demanded current instead of just noise, in a decoupling context.

Last edited by gootee; 25th July 2012 at 06:11 AM.

 25th July 2012, 06:10 AM #292 abraxalito   diyAudio Member     Join Date: Sep 2007 Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though... Inspiring to see that even the 'old hands' are learning things here Tom - WTG __________________ 'The total potential here must be nothing less than astronomical.' 'Nothing less. The number 10 raised almost literally to the power of infinity.'
fas42
Banned

Join Date: Jun 2012
Location: NSW, Australia
Quote:
 Originally Posted by gootee I was going to respectfully disagree, and was going to say the following: ---------------- Thank you. I just wish I had noticed that, years ago, before it cost me so much extra effort when doing spice modeling and simulation. (But the capacitor spice models from that CDE java applet are coool.) Cheers, Tom P.S. I'm definitely with you on the inductance issues, and also for demanded current instead of just noise, in a decoupling context.
And I've just run through some of your "vigorous" input in that thread - we are on the same page!! I've done a lot of thrashing myself using LTspice, that duplicates in many areas the sort of things you were so passionately researching. So, I know exactly why you were beating the drum about current requirements as strongly as you did, and the need to acquire full understanding of all the parasitics in the equation ...

Frank

forr
diyAudio Member

Join Date: Dec 2004
Location: Next door
Quote:
 Originally Posted by gootee Just did a quick LTSpice simulation of a 40V linear power supply with a 14000 uF reservoir cap and an 8 Ohm load, with no ESR and with 0.1 Ohm ESR. The attached ripple voltage plot shows the effect. It's due to ESR.

Thanks for this finding. It's worth more investigation.
Is it not a good way to determine the optimal value of the reservoir cap such as the peak in the waveform with ESR does not show up ?

PChi
diyAudio Member

Join Date: Jan 2012
Location: Staines, UK
Quote:
 Originally Posted by forr Thanks for this finding. It's worth more investigation. Is it not a good way to determine the optimal value of the reservoir cap such as the peak in the waveform with ESR does not show up ?
I don't think that it's a good way to determine the optimal value.
If the waveform show significant distortion due to Capacitor ESR it's time to buy a new capacitor.
It's either not a very good capacitor to start with or it has been abused and it's getting near the end of it's life.
In my experience all the reputable manufacturers' capacitors won't show that effect in a typical circuit. I have only seen that sort of waveform with poor quality electrolytic capacitors.

OnAudio
diyAudio Member

Join Date: Oct 2011
Quote:
 Originally Posted by gootee which gives something like this: http://www.diyaudio.com/forums/attac...ps-cdejava.jpg

forr
diyAudio Member

Join Date: Dec 2004
Location: Next door
Quote:
 Originally Posted by PChi I don't think that it's a good way to determine the optimal value. If the waveform show significant distortion due to Capacitor ESR it's time to buy a new capacitor. It's either not a very good capacitor to start with or it has been abused and it's getting near the end of it's life. In my experience all the reputable manufacturers' capacitors won't show that effect in a typical circuit. I have only seen that sort of waveform with poor quality electrolytic capacitors.
Since ten years, I always check all the electrolytic capacitors I use with Cyril Bateman's tan-delta-meter and a capacitor meter. I am not sure many people are equipped with such an apparatus and are so methodical. I hope you are.
Among many I tested, SIC-SAFCO caps always show dependable, reliable, excellent performances.

 25th July 2012, 05:35 PM #298 MiiB   diyAudio Member   Join Date: May 2005 Location: Denmark There's at lot to learn here....capacitance falls radically with frequency, impedance rises with frequency as the caps turns inductive...hmm...This much more than I had expected. having polypropylene's/ceramic as final reservoirs seems almost mandatory..what is superb spec's worth, if there's no current to deliver.
PChi
diyAudio Member

Join Date: Jan 2012
Location: Staines, UK
Quote:
 Originally Posted by forr Since ten years, I always check all the electrolytic capacitors I use with Cyril Bateman's tan-delta-meter and a capacitor meter. I am not sure many people are equipped with such an apparatus and are so methodical. I hope you are. Among many I tested, SIC-SAFCO caps always show dependable, reliable, excellent performances.
I don't have Cyril Bateman's tan-delta-meter and I haven't been so methodical.
I was commenting on experience, OK many years ago, when only LCR electrolytic capacitors had significant ESR for a Linear simple rectified power supply though they were cheap.
The Nippon Chemi-con capacitors that were generally used had a low enough ESR that the effect on the wave form was largely absent.

 25th July 2012, 06:20 PM #300 OnAudio diyAudio Member     Join Date: Oct 2011 Hi guys replace your onboard caps with these caps http://www.diyaudio.com/forums/solid...ml#post3102253

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