Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Beginning SMPS?
Beginning SMPS?
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
Thread Tools Search this Thread
Old 31st August 2005, 12:23 AM   #41
thomas997 is offline thomas997  Canada
diyAudio Member
thomas997's Avatar
Join Date: Feb 2004
Location: Vancouver
Originally posted by funberry
Are you sure the toroids are ferrite? There are a lot of powdered iron toroids floating around, and it's not easy to tell them apart. If anyone out there knows how to use simple bench tests to differentiate between ferrite ans powdered Fe, please come forward and say.
You need to calculate the cross-sectional area of the toroid, make sure it's the same as that of the central post of the transformer you're replacing.

Aaaaaaah.... the bobbins.... Now you understand why it's important to preserve them (with the core they're on). This is an even more elusive product than the ferrite. They seem to be about $3 when paying an "authorized disributor's" resale list price. You can't easily find a distibutor that has them, and is willing to sell just two or three.


They were sold as ferrite, so I hope the guy knew what he was talking about... Also theres no coating on them, but I dont know if iron powder cores come like that as well.

  Reply With Quote
Old 31st August 2005, 06:22 AM   #42
funberry is offline funberry  United States
diyAudio Member
Join Date: Aug 2005
This is Electrovalue, in the UK, listing ETD49 cores at 1.73 BP, and bobbins for it at 75 pence.


In a bind, I guess it might do.

Dexter Magnetics , will cost you less, and they have all cores and bobbins at decent prices, but minimum order is $100.

Ultimately, any core shape will do; the only glamour about ETD cores is their special geometry which is optimized for the most power with the least amount of copper.

Since you may not know the grade of ferrite in your toroids, you can go trial-and-error: You test the prototype under reduced supply voltage and well fused. As you increase the voltage, monitor the Xformer temperature. If the core gets too hot to touch, there may be too much core loss. (wrong grade, wrong frequency). If the copper or the transistors get too hot. the core may be saturating (freq too low for ferrite grade) If nothing heats up too much, and power output is low, frequecy could be too high for the ferrite grade.

Since this experimentation is often accompanied by smoke, I try to avoid unknown material grades for SMPS power transformers. I figure 6-8 hours of experimentation, accompanied by cursing, smoke, injury, and some semiconductor losses, are a higher cost than 6 bucks paid for a known good material.

IMHO, the only unknown ferrite safe for an SMPS power transformer is a ferrite that comes from an SMPS power transformer.
  Reply With Quote
Old 31st August 2005, 03:21 PM   #43
N-Channel is offline N-Channel  United States
diyAudio Member
N-Channel's Avatar
Join Date: Mar 2003
Location: Sol System
Send a message via AIM to N-Channel
Default Ferrite and Powdered-Iron Toroids

I have several Ferrite Toroids, and there is not much of a way to tell the different FERRITE materials apart from each other, but you CAN tell the difference between a Ferrite and Powdered-Iron (PI) core. Most manufacturers, (Amidon, Fair-Rite, Ferroxcube and others) use a standard color code for their PI Toroids.

For example, Amidon Coproration's Jan 2000 Catalog shows the color code for their P-I Toroids:

Material Color
0 Tan
1 Blue
2 Red
3 Grey
6 Yellow
7 White
10 Black
12 Green/White
15 Red/White
17 Blue Yellow
26 Yellow/White.

The BIG toroid found in most AT and ATX SMPSs is most often the Yellow/White #26 P-I material. 26's magnetic properties are in the catalog.

For the Ferrites, I am not aware of any color code that exists for the different types of materials. However, Amidon's catalog has all the charts and graphs of all the ferrite materials' magnetic properties.

The material most often used iin the main power Xfmr in half-bridge AT/ATX boxes is the #77 mix, with a u=2000. I can't speak to the flyback types.

For a very cut-n-dried process on how to figure the number if turns for a specific application, check out George Chryssis' book "High Frequency Switching Power Supplies", (c) 1989 edition. I can't remember the chapter number, but the chapter on transformers gives a very good procedure for both forward transformers and flyback transformer-chokes. I have used this design procedure many times winding toroids, with great success.

For winding P-I Toroids, I use the A(L) value charts to figure the number of turns for a desired inductance.

Check out www.amidoncorp.com and ask for their latest catalog or spec sheet.

Hope this helps,

  Reply With Quote
Old 31st August 2005, 10:38 PM   #44
Eva is offline Eva  Spain
diyAudio Member
Eva's Avatar
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
In order to check for core material properties, build a simple current-limited flyback converter that allows to regulate duty cycle and frequency with a potentiometer. Wrap several turns on the core as a primary winding and use a very low value non-inductive resistor as a current sense element. Power the whole thing from an adjustable low voltage current limited power supply.

The primary current versus time waveform will tell a lot of useful information. Iron powder will show very low permeabilities so primary current will skyrocket if not enough primary turns are used. Power ferrites will show moderate permeabilities and progressive saturation. Signal ferrites will show high permeabilities and very sharp saturation. Saturable reactors will look a lot like signal ferrites but they will need an adjustable DC current source (in opposite direction to switch current) in order to get biased and to adjust saturation time.

For iron powder cores (and gapped ferrites), inductance may be calculated by dividing the applied voltage by the observed current slope in amps/second . Current versus time waveform will also show saturation current level. Inductance and saturation current may be extrapolated for other turn counts with the following formulas:
L2 = L1 * N2^2 / N1^2
Is2 = Is1 * N2 / N1
(Note that this gets less and less accurate for lower permeability materials and longer air gaps due to leakage inductance).

For ferrite cores (ungapped), the time the core takes to saturate for a given amount of turns and voltage may be easily extrapolated for different conditions, allowing to choose optimum turn counts for unknown materials. Time will be proportional to turns and inversely proportional to voltage. Note that saturation time will be doubled when bipolar excitation is employed (push-pull converters.

I use this empirical method even when I actually have material specifications. I feel it's better to actually check transformer and inductor properties before using them instead of just relying on equations and material parameters.
  Reply With Quote
Old 12th September 2005, 09:59 PM   #45
richwalters is offline richwalters
diyAudio Member
richwalters's Avatar
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
The config Eva uses is well known......Caveat emptor......nearly all of Magnetics Inc cores are the same colour !

  Reply With Quote
Old 26th September 2005, 09:52 PM   #46
Dan2 is offline Dan2  South Africa
diyAudio Member
Join Date: Sep 2005
Anyway I can find a lot of 12V smps circuits and designs, but not a whole lot of 120V.

hey thomas997, i need a 12v SMPS that can give me 50v. I know it's late, but if you can help me with a circuit design that would be great.
  Reply With Quote
Old 2nd October 2005, 04:44 AM   #47
thomas997 is offline thomas997  Canada
diyAudio Member
thomas997's Avatar
Join Date: Feb 2004
Location: Vancouver
Originally posted by Dan2
Anyway I can find a lot of 12V smps circuits and designs, but not a whole lot of 120V.

hey thomas997, i need a 12v SMPS that can give me 50v. I know it's late, but if you can help me with a circuit design that would be great.

I'm not the one to ask sorry
  Reply With Quote
Old 3rd October 2005, 04:48 AM   #48
marcus66 is offline marcus66
diyAudio Member
Join Date: Aug 2002
Location: Uppsala, Sweden
I have a question for you SMPS experts here. I did not want to start a new thread, and I figured that it is a beginner's question, so here goes:

On the homepage of amp manufacturer LAB.Gruppen they say the following about the SMPS in their (now discontinued) amplifier model LAB1300C (a 2x600W class AB amp):

'' In contrast to many of our competitors, who use so-called push-pull converters and other designs, which require current limiting, we have designed the LAB 1300 to obtain the same caracteristics as a conventional power supply. It works by of injecting a magnetic pulse from the AC-line during a pulse time segment, which is separated from the output charge current pulse. Because of this no current limiting is needed for the secondary side of the transformer, and high peak power and good bass response are guaranteed. ''

What kind of circuit do you think they are talking about here? In contrast to QSC, there are no schematics available on the homepage of this company, but the corresponding user manual gives a clue that sense windings are used to achieve the above operation. Are schematics for a similar smps available somewhere?
  Reply With Quote


Beginning SMPS?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
beginning of a car amp rwaudio Car Audio 8 27th March 2007 11:10 AM
Beginning my aleph 30 bobsinclar Pass Labs 85 4th November 2006 11:01 AM
beginning dome406 Solid State 0 2nd November 2004 06:12 PM
In the beginning ..... gpsmithii Pass Labs 15 24th November 2003 05:34 PM
Beginning my first project onebadziggy Multi-Way 38 28th January 2003 02:23 AM

New To Site? Need Help?

All times are GMT. The time now is 11:59 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio