Revie my +-15V and +5V power supply - 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 23rd June 2012, 12:59 PM   #1
diyAudio Member
 
Join Date: Jan 2009
Default Revie my +-15V and +5V power supply

Hi I am starting my first (bigger) DIY project box(spdif receiver/DAC/preamplifier). For powering opa627 I need +-15V supply and for powering other chips +5V or lower. After I made a research on the internet (mainly Power Supply for Preamps ) I came up with this schematics. In this power supply I was thinking about using Panasonic FC(35-50V) caps. One thing I still don't know if I would be okey with 2x18V 15VA toroidal transformer. Because it has 420ma supply per rail. I tried to roughly calculate how much current would be drawn by my box and excluding 3 voltage regulators seen in the schematics and two LDO regulators from texas instrumets for powering receiver and DAC. I've got that semiconductor parts: 8xopa627 (60mA), 2xBUF634 (40mA), cs8614 (11,8mA), wm8741 (95mA) and atmega8 should draw about ~25mA. So the total current on + rail would be 231,8mA if I am correct.

So any thoughts on this power supply or my chosen toroidal transformer are very welcome.
P.S. I want to get it right from the first time:]
Attached Images
File Type: png power supply.png (51.0 KB, 231 views)
  Reply With Quote
Old 23rd June 2012, 01:14 PM   #2
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
Most low power amp circuits are operated in Class A so I would at least double your expected current draw.
  Reply With Quote
Old 23rd June 2012, 01:21 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I have not checked the datasheets, but I think the currents you are quoting for the ICs are the quiescent currents when no signal is passing.

If the IC passes current to the load (on each IC) then that load current is additional to the quiescent current (for each IC).
__________________
regards Andrew T.
  Reply With Quote
Old 23rd June 2012, 01:26 PM   #4
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
I reckon your 15VA transformer will be too small. Personally I would be looking at a 60VA unit and design your rails at 1A. The LM317 and LM337 will be fine but might need a bit of sinking.
  Reply With Quote
Old 23rd June 2012, 01:49 PM   #5
diyAudio Member
 
Join Date: Jan 2009
Thank you very much for our opinion. Yes some the currents were Iq. Just out of curiosity is there a way to calculate typical supply current from Iq? (I am a starter at electronics and still need a lot of knowledge..)
  Reply With Quote
Old 23rd June 2012, 05:57 PM   #6
diyAudio Member
 
Join Date: Sep 2010
The fuses should be located before the rectifiers.

You can add 10 to 100 uF capacitors across R2, R4 and R6, as mentioned in the datasheets for increased ripple rejection. They give a worthwhile performance increase.

I would feed the 5 V supply directly from the transformer to avoid loading the +15 V with 'digital' current. Using a double half bridge rectifier for this keeps the two windings on the transformer equally loaded as well. In other words feed the 5 V regulator from JP1 and JP4 via two rectifier diodes, cathodes tied together, like this:
http://upload.wikimedia.org/wikipedi...ctifier.en.svg
Keep the Gnd-Gnd connection.
Of course add a 1000 to 2200 uF filter capacitor at the input to the 5 V regulator.

You may find a small series resistor (1 ohm, 1-2 W) on the input side of each regulator useful to easily measure current when in use. Inserting this resistor between the 2200 uF filter capacitors also improves filtering a little bit.

Last edited by discrete; 23rd June 2012 at 06:00 PM.
  Reply With Quote
Old 23rd June 2012, 08:10 PM   #7
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by zmogedra View Post
Hi I am starting my first (bigger) DIY project box(spdif receiver/DAC/preamplifier). For powering opa627 I need +-15V supply and for powering other chips +5V or lower. After I made a research on the internet (mainly Power Supply for Preamps ) I came up with this schematics. In this power supply I was thinking about using Panasonic FC(35-50V) caps. One thing I still don't know if I would be okey with 2x18V 15VA toroidal transformer. Because it has 420ma supply per rail. I tried to roughly calculate how much current would be drawn by my box and excluding 3 voltage regulators seen in the schematics and two LDO regulators from texas instrumets for powering receiver and DAC. I've got that semiconductor parts: 8xopa627 (60mA), 2xBUF634 (40mA), cs8614 (11,8mA), wm8741 (95mA) and atmega8 should draw about ~25mA. So the total current on + rail would be 231,8mA if I am correct.

So any thoughts on this power supply or my chosen toroidal transformer are very welcome.
P.S. I want to get it right from the first time:]
also remember the power that the regulators will burn off.

Last edited by AudioSan; 23rd June 2012 at 08:30 PM.
  Reply With Quote
Old 23rd June 2012, 09:41 PM   #8
diyAudio Member
 
Join Date: Jan 2009
WOW thanks discrete for your tips!
  Reply With Quote
Old 24th June 2012, 08:07 AM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
The secondary fuses achieve no added safety when fitted before the smoothing capacitors.
Fit a close rated mains fuse. That protects against the transformer and/or the rectifier and/or the smoothing capacitors going seriously faulty.
Added protection can be gained by fitting secondary fuses after the smoothing capacitance.
__________________
regards Andrew T.
  Reply With Quote
Old 24th June 2012, 03:00 PM   #10
diyAudio Member
 
Join Date: Sep 2010
Hi Andrew,

I agree with the close-rated mains fuse.
However, with small transformers (<50 VA?) I do not trust any primary fuse to protect the transformer in case of rectifier or filter capacitor failure and add secondary fuses as a rule.

If the concern is to protect the regulators / audio circuits, then for sure add some fuses to each load after the main filter capacitors.
  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
Circuit Sanity Check: +15V, -15V, +9V Power Supply miallen Power Supplies 4 18th July 2009 08:18 PM
Using 15V laptop power supply on t-amp aussiebuddha Class D 9 20th September 2006 01:44 PM
+/-15v Power supply argonrepublic Parts 3 4th January 2006 08:10 AM
5V, 9V, 15V or 24V human prototype Solid State 1 31st July 2001 03:42 AM


New To Site? Need Help?

All times are GMT. The time now is 03:32 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