SMPS Hissing &amp; Whining Noises - Page 2 - diyAudio
 SMPS Hissing & Whining Noises
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 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
 21st December 2008, 04:49 AM #11 diyAudio Member     Join Date: Mar 2008 Hi Guys, Thanks you so much for your help, it's been really educational At first I was confused about how you came up with Np = 96 turns for the sample calculation and then I realised that Ae needs to be entered in square meters and so needed to convert up from square millimetres. Seems this is a much simpler method for Np calculation. So my current transformer design with Np=5:0:5 was wrong for 70kHz, but should be happy running f = 48 kHz which should be an interesting test. Will report back. Just to be sure I really understand this, can we just review the design at 70kHz with the Ae = 1.206 cm2 core? Np = (12*70000^-1*0.48)/(0.2*(1.206/(100*100))) = 3.41 (rounded to 4 turns) Ns = 4*(55/12) = 18.333 (rounded to 19) Thus the new 70kHz 55V + 55V output transformer should be as follows correct? Np = 4:0:4 Ns = 19:0:19
 21st December 2008, 05:54 PM #12 diyAudio Member     Join Date: Mar 2008 Awesome success today. Just changed the frequency after using the new equation and the SMPS is running like it should. Cool even with moderate loading and only draws about 200mA when idle. I suppose if I used regulation it would be even more efficient when idle. I'm using it at the moment to power a mosfet power amplifier and am very happy indeed :-D I didn't even change the number of Np windings or the poor winding technique as highlighted previously. Next step will be to wind up a new transformer with the bifilar winding technique and also adjust Ns to get a higher Vout. Thanks so much! I might have to start thinking about the offline version sooner than expected.
diyAudio Member

Join Date: Oct 2008
Location: Plano, TX, USA
I come out with 4 turns on the primary and 18 for the secondary.

However if the voltage can drop to10.5V then you'll need 3 turns and 15 turns.
Attached Files
 pushpull calc.pdf (15.2 KB, 56 views)

 22nd December 2008, 01:42 AM #14 diyAudio Member     Join Date: Oct 2003 Location: Near the sea I think that the problem is related to anything but the amount of primary turns. Could you post pictures of your prototype and transformer? Linear audio amplifiers are almost fool-proof but for SMPS layout matters. ITL501 inductors seem to be made with gapped ferrite cores and thus are *completely* unsuitable for your purpose. The cores from the other ITL series inductors are not suitable either. Get a straight ferrite toroid core, there are several on-line sources. Most materials will do, for example, I use 3E25 which is intended for signal transformers and EMI filters rather than power transformers but the only penalty is one or two more turns (and a longer dead time is required to achieve Zero Voltage Switching resonant operation due to the higher permability and resulting inductance). __________________ I use to feel like the small child in The Emperor's New Clothes tale
 22nd December 2008, 04:01 AM #15 diyAudio Member   Join Date: Oct 2008 Location: Plano, TX, USA I would alsp suggest that before you crank it to full power you carefully review the primary/secondary leakage since the high current you will have in the leakage will give you a very large leakage inductance spike at turn off. You need that leakage to be as small as you can get it. Tony
diyAudio Member

Join Date: Mar 2008
Hmmm - It's really working quite well seemingly with just a frequency change. Yes the output voltage is lower than hoped, but higher enough to run the amp to make some noise.

The SG3525 is just on a breadboard right now and the Mosfets (F25MN60N) are mounted on a small heatsink.

Sounds like you're very familiar with gapped cores. The ITL501 from Wilco doesn't appear to be gapped at all, at least there's no mention of it in the product information page unless it's implied by the other parameters that are given. The page I'm referring to is here:

http://www.wilcocorp.com/catalog/series.cfm?series=ITL

The page notes explicitly mention ITL501 being a ferrite core so I'm confused by your comments. I must be missing something I suppose, so thanks for your patience :-S

Here are some photos of the amateur setup.

Thanks for looking.
Attached Images
 img_0336 (medium).jpg (48.3 KB, 385 views)

diyAudio Member

Join Date: Mar 2008
And another...
Attached Images
 img_0325 (medium).jpg (57.2 KB, 386 views)

 22nd December 2008, 10:12 AM #18 diyAudio Member     Join Date: Oct 2003 Location: Near the sea There is no way to get the inductance and saturation current values stated unless the ferrite core is gapped. Your layout is completely wrong. There is not even an input filter on the 12V line. The input and output filters, MOSFET and transformer require a PCB. Never use point to point for SMPS. Transformer winding layout is also completely wrong. It results in maximum leakage inductance that way. There are several threads describing the optimum way to do these things, so you should do some research. __________________ I use to feel like the small child in The Emperor's New Clothes tale
diyAudio Member

Join Date: Mar 2008
Ah that would be where my inexperience is letting me down. I'm not familiar with inductors parameters and gapped cores etc.

I suppose an unpainted core would make it obvious if there was a gap. Just had a scratch in my stash of stuff and have found some other ferrite cores to play with (photo attached)

A first PCB will be finalised now as I at least have something stable that doesn't threaten to catch fire or deafen me with it's shrieks and whines.

So how does the existing gapped core effect performance and / or design? What is leakage inductance? I'll Google it too.

It seems that even this gapped core is working quite well after correcting the switch frequency following use of the correct formulae. Is there something I can measure to see where this gap is letting me down?
Attached Images
 img_0344 (medium).jpg (59.4 KB, 329 views)

 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 OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post willos Digital Source 50 1st December 2008 04:41 AM contentryder Car Audio 9 24th February 2008 03:59 AM Alex Barnett Digital Source 3 7th October 2007 04:07 PM Todor Power Supplies 20 15th July 2005 11:56 PM tr3 Tubes / Valves 5 23rd June 2002 07:11 PM

 New To Site? Need Help?

All times are GMT. The time now is 04:16 PM.