Power Supply Resevoir Size - Page 43 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th August 2012, 12:48 AM   #421
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Quote:
Originally Posted by Terry Given View Post
Frank & Tom:

If you remove the entire amplifier & modulated load from the sim, and replace with a resistor, you will see the droop caused by the transformer "regulation" - which will be mostly due to the leakage inductance and the narrow conduction angle. I'd also look carefully at the rectifier model as well - its probably fine, but there are, for example, 10BQ100 spice models with 100R slope resistance (I found them the hard way)
Don't worry, Terry, I've been around the perfect resistive load scenario a vast number of times; the trick here is to deal with the real world of amplifier linear PS's, and class AB loading, and to see what the best way to handle that is ...

Frank
  Reply With Quote
Old 9th August 2012, 03:42 AM   #422
diyAudio Member
 
Join Date: Oct 2006
Will your sims allow for the speaker(s) reacting?
Can't help but think that a proper model from AC mains to speaker is a level of work that'd be a 3rd of a phd. Add a good model of the human ear and psychoacoustics and you'd be looking at tenure.

Does the speaker prefer current to be stored in a cap for bursts or flowing via transformer, I dunno, but I do know that its easier to add caps to a psu than it is add transformers to a case thats already been laid out.
  Reply With Quote
Old 9th August 2012, 03:49 AM   #423
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Quote:
Originally Posted by fas42 View Post
Just a cautionary thought, Tom ... my belief is that real circuitry should be used to load the PS, otherwise one's thinking can possibly be led down an unnecessarily torturous detour. Ultimately, what one comes up with in terms of results has to relate to real, on the bench, bits of circuitry, because that's what the whole exercise is about ...

Cheers,
Frank
Frank,

By "real circuitry" I assume that you mean "simulated real circuitry" instead of behavioral current sources driven by equations. <smile>

Normally I would tend to agree but in this case there is an important advantage to using the B-sources, and, I can't see any difference in their behavior, compared to "real" circuitry.

I figure I can at least use the the B-sources to examine the output error and then use "real" circuitry for verification.

Cheers,

Tom
  Reply With Quote
Old 9th August 2012, 05:24 AM   #424
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Quote:
Originally Posted by gootee View Post
Frank,

By "real circuitry" I assume that you mean "simulated real circuitry" instead of behavioral current sources driven by equations. <smile>

Normally I would tend to agree but in this case there is an important advantage to using the B-sources, and, I can't see any difference in their behavior, compared to "real" circuitry.

I figure I can at least use the the B-sources to examine the output error and then use "real" circuitry for verification.

Cheers,

Tom
Yep , but what I'm questioning is the fact that using the u(x) step function is reverting the sim to a "perfect" class B amp, rather than class AB. The fact that you had to bypass with a cap says that it's not matching reality, you're switching the supplies on and off too hard ...

But, there are always many ways to skin a ... -- if it works for you, go for it!

Cheers,
Frank
  Reply With Quote
Old 9th August 2012, 05:34 AM   #425
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Quote:
Originally Posted by dry joint View Post
Will your sims allow for the speaker(s) reacting?
There's no reason why the kitchen sink can't be thrown at doing a mockup in terms of the detail added; the good thing is that it gives one a highly flexible, and speedy handle on understanding what's really important, and what's not. So a really nasty speaker load, and badly distorted AC mains can be introduced down the track, to check their impact.

Frank
  Reply With Quote
Old 9th August 2012, 05:43 AM   #426
Banned
 
Join Date: Aug 2012
capacitance multiplier, jee I thought this was a serious forum.
  Reply With Quote
Old 9th August 2012, 05:56 AM   #427
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Quote:
Originally Posted by liching1952 View Post
capacitance multiplier, jee I thought this was a serious forum.
...

Frank
  Reply With Quote
Old 9th August 2012, 06:48 AM   #428
diyAudio Member
 
Nico Ras's Avatar
 
Join Date: Nov 2005
Location: East Coast of South Africa
Quote:
Originally Posted by liching1952 View Post
capacitance multiplier, jee I thought this was a serious forum.
I am of the opinion that a capacitance multiplier would be the worse candidate for a dynamically changing load as it just slows things down even more. Unless you have some example or explain your thoughts a little.
__________________
Kindest regards
Nico
  Reply With Quote
Old 9th August 2012, 07:00 AM   #429
diyAudio Member
 
Join Date: Mar 2008
Frank, yeah I realise that, and its why this is such a neat thread.

the suggestion was merely to illustrate where the droop is coming from.

Andrews "filter" approach is a nice way of looking at it.

but I think what this thread has shown is that we can clearly see three regions: LF (< 100Hz), MF and HF (> 10kHz) (arbitrary numbers, YMMV)

in the MF region its a capacitor bank with ESR. more C, less ESR = good

the HF region handles the transient response, and is dominated by parasitics - ESR, ESL - of both the components and the construction. low-inductance layout/interconnect and paralleling many smaller caps (if done properly) = good.

this has been most of the focus of this thread. But "optimal" (whatever that is) design of the cap bank taking all this into account wont help with....

the LF region, which the droop aspect highlights. It is dominated by the transformer and its interaction with the DC bus caps (more C = narrower conduction angle = higher peak current = greater voltage drop in xfmr).

I think it fair to say that what frank, tom et al have demonstrated is that the transformer needs to be designed too. probably every bit as carefully as an audio output transformer. low leakage inductance is a must, and even then it needs to be designed in conjunction with the cap bank, rather than just blindly throwing C at it, followed by stupidly oversized transformers.

A toroid is, of course, a good start, but it would be really interesting to look at a range of transformers and see how well they perform. my experience with LF transformers is that they tend to be designed automatically, and invariably emphasise electrical safety and thermal performance ahead of electrical performance.

I've seen designs from a variety of places (including some that really ought to know better) that completely ignore proximity effect - "its an HF thing". no it aint, its just that as long as your conductor diameter < 5mm it wont matter at 50/60Hz, so for little stuff its almost never a problem - but above 10kW or so it can and does matter. really big stuff is of course done properly (thou shalt not screw up power systems).

a physically split bobbin to keep primary and secondary separate is a brilliant way to produce a very high leakage inductance, and makes electrical safety (e.g. hipot testing) a breeze....
  Reply With Quote
Old 9th August 2012, 07:37 AM   #430
Banned
 
Join Date: Aug 2012
Quote:
Originally Posted by Nico Ras View Post
I am of the opinion that a capacitance multiplier would be the worse candidate for a dynamically changing load as it just slows things down even more. Unless you have some example or explain your thoughts a little.
C multiplier will not work at all. See my comment above. Wondering that nobody saw that.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Valve power supply - How to size transformer? SanderW Power Supplies 25 4th January 2013 04:12 PM
How do you calculate choke size in a power supply? Original Burnedfingers Tubes / Valves 25 5th January 2012 12:23 AM
power supply bypass cap size BigE Power Supplies 11 5th July 2011 02:59 PM
Power Supply Case Size diymixer Power Supplies 1 10th October 2010 05:47 AM
What size power supply should I get for repair work? spooney Car Audio 3 6th December 2007 11:50 PM


New To Site? Need Help?

All times are GMT. The time now is 03:04 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2