Unregulated Power PCB - 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 5th September 2010, 08:13 PM   #1
diyAudio Member
 
luvdunhill's Avatar
 
Join Date: Jul 2006
Default Unregulated Power PCB

I have a few uses for a simple PCB that supports a number of different ~25VA PCB mount transformers with a bit of filtering on each side of the transformer. I'm trying to nail down the schematic a bit and wanted to see if there was any advice out there Improvements perhaps?

Click the image to open in full size.
  Reply With Quote
Old 5th September 2010, 09:49 PM   #2
diyAudio Member
 
luvdunhill's Avatar
 
Join Date: Jul 2006
ECO #1 is a properly connected bridge on the bottom half
  Reply With Quote
Old 5th September 2010, 10:22 PM   #3
JimT is offline JimT  Canada
diyAudio Member
 
Join Date: Oct 2004
Location: Waterloo
I would allow for a thermistor like a CL60 on the input of the transformer.

Jim
  Reply With Quote
Old 6th September 2010, 03:36 AM   #4
diyAudio Member
 
luvdunhill's Avatar
 
Join Date: Jul 2006
Quote:
Originally Posted by JimT View Post
I would allow for a thermistor like a CL60 on the input of the transformer.

Jim
Jim, I could do that, but we're dealing with probably a max of 25VA here. What value would be appropriate in this case? Seems like it wouldn't be much of an issue?
  Reply With Quote
Old 6th September 2010, 05:33 AM   #5
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Please wire the transformer as CT'd and use one FWB.
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote
Old 6th September 2010, 01:22 PM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
How about adding lots of MOVs or similar across the L to N to limit the voltage spikes from the mains?
Allow for R+C across the diodes. some diodes do not need snubbers, other do need snubbers. Some misbehave badly when a single cap is paralleled across the diode.

Nothing wrong with dual rectifier. Rectifying each secondary and connecting them in series after the first stage smoothing is recommended by many.

Move the Safety Earth/Chassis connection from the output end of the PSU to the common point between the first stage smoothing caps. Join this zero volts point to the PSU output.
Send the PSU output to the main audio ground.
__________________
regards Andrew T.
  Reply With Quote
Old 6th September 2010, 03:28 PM   #7
diyAudio Member
 
luvdunhill's Avatar
 
Join Date: Jul 2006
Thanks for the help, first of all!

A few comments:

I've never used a MOV, but the theory seems the same as a thermistor? Would it be possible to incorporate two of the suggestions and put one CL60 thermistor between the secondaries for 240V operation and use two for 120V? Around 10 ohms I'd assume would be fine? If I've assumed incorrectly, and a MOV behaves differently, any recommended part?

I understand moving the ground loop breaker to the first stage smoothing cap, good catch. However, if I connect this zero volt point to the output, I've effectively shorted one of the chokes, and ruining the idea of using a common mode device. Comments?

Finally, in hunting for these common mode devices, some don't list inductance at all in the datasheets, but impedance at a given frequency, DCR and a rated current. Some investigation says not much inductance is really required. I'm looking at this device at the moment and was wondering what you guys think:

http://www.steward.com/web_info/CADP...71B-10-C-2.pdf

It's one of the rare, relatively compact through hole devices... my question is, perhaps I should be looking at a higher impedance device, in the order of 4-5 times larger?
  Reply With Quote
Old 6th September 2010, 04:13 PM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
MOV metal oxide varistor.
Varistor - Wikipedia, the free encyclopedia
It avalanches when the voltage exceeds it's rating, passing enormous current for a very short time.
Quite different from a Thermistor.
__________________
regards Andrew T.
  Reply With Quote
Old 6th September 2010, 05:40 PM   #9
diyAudio Member
 
luvdunhill's Avatar
 
Join Date: Jul 2006
yup, I see that now. I think this will be suitable:

V250LA2P Littelfuse Varistors - MOV
  Reply With Quote
Old 7th September 2010, 09:48 AM   #10
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
almost, but the wrong voltage rating.
In the UK we use 275Vac, chosen to exceed our maximum of 254Vac on our 240Vac nominal supply.

I would expect there to be 130/135/140Vac suitable for your lower voltage supply.

John Curl recommends a 10uF cap across the L&N at the distribution board to help with this spike and harmonic attenuation.
__________________
regards Andrew T.
  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
High Power Transformer/Power supply PCB for Sale. Count Tubeula Parts 2 26th October 2012 08:45 AM
Unregulated PSU MarcH Solid State 8 8th June 2008 10:35 AM
Why are servo power supplies often unregulated? philpoole Digital Source 6 28th September 2006 10:40 AM
unregulated wallmart power supply cap size ash_dac Power Supplies 11 18th August 2005 12:39 AM
My first-ever PCB board: Unregulated PSU for a two gainclones eranrund Power Supplies 21 4th June 2005 11:56 PM


New To Site? Need Help?

All times are GMT. The time now is 04:31 AM.


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