Use and mods to Analog Metric SR50 Shunt Regulator - 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 21st July 2014, 11:15 AM   #1
diyAudio Member
 
Join Date: Feb 2009
Location: Wales UK
Default Use and mods to Analog Metric SR50 Shunt Regulator

Over the last few months I have been using and tweaking this for a 5v 1A shunt regulated supply for a Raspberry Pi based music server, http://http://www.analogmetric.com/goods.php?id=2211 and though I would share my findings with the forum members.

First of all I need to make clear that a lot of my findings have been based on simulated Spice CAD results (NI Multisim) and my test equipment is very basic, oscilloscope, frequency counter, dvm. Now this may ruffle a few feathers, but all measurements are comparative and the reason in sharing my findings is to offer them up to my peers for review and criticism even! Hopefully, someone with better equipment might try a few ideas and make some real world measurements? Glad to get that out of the way!

Now this kit gives excellent value for money and is of good quality, but it will not provided 1A @ 5v and it will only provide around 89dB of PSRR in its original form. However, a couple of simple mods will give the required current and significantly improve the PSRR. If you follow the link below it will give the schematic for reference.

Mod 1 - to get 1A at 5v simply replace Q2 with a Darlington type, I used a TIP137, which is a pin for pin replacement for the MJ15031. The Darlington increases the vbe of Q2 to allow Q1 to turn on enough to enable the current source at this level. This mod also improves PSRR due probably to the higher hfe of the Darlington. R1 needs to be around 0.5Ohm to give 1A out.

Mod 2 - to improve PSRR even further, disconnect R4 (10k) from the junction of R3, D1 and Q3 and connect it directly to the +ve regulator output, i.e. collector of Q2. This is in line with the typical applications part of the TL431 datasheet. The pot will have to be adjusted to get the right Vout of 5v, but it is within its adjustment range. This mod increases PSRR to almost 140dB up to around 20KHz and from there it deteriorates back to around 88dB at 600KHz

There are further mods that can be carried out to improve PSRR even further over a wider bandwidth, but they require more "surgery". If this thread generates any interest then I will be happy to share those too.

I have used this modified regulator for a few months and can report that it has been rock solid and quiet and the sound quality improved with every mod that I tried.

Your feedback would be appreciated ladies and gents!
Attached Files
File Type: pdf SR50 Shunt Regulator.pdf (71.6 KB, 172 views)
  Reply With Quote
Old 21st July 2014, 11:37 AM   #2
udok is online now udok  Austria
diyAudio Member
 
Join Date: Jul 2011
Nice work :-)
What is the advantage of a shunt regulator in comparison to a LM1117 or similar?
  Reply With Quote
Old 21st July 2014, 01:45 PM   #3
diyAudio Member
 
Join Date: Feb 2009
Location: Wales UK
Quote:
Originally Posted by udok View Post
Nice work :-)
What is the advantage of a shunt regulator in comparison to a LM1117 or similar?
Now that could be a loaded question! We all have our individual ideas and preferences, its a bit like driving a Ford or a BMW?

I first got into shunt regs in the 90s after reading Allen Wright's Tube Preamp Cookbook, a wonderful book and a well respected designer, now no longer with us.

The best analogy I can offer is that you can compare a series regulator to a class B (at best) amp and a shunt reg as a class A amp. The series reg works by switching on/off (very quickly) depending on load demand. The shunt device is fed by a constant current source and the shunt transistor varies according to load, but it is always on. Remove the load and all the set current is dissipated in the shunt device, short the output and all the current goes to the short, but it can be no more that what is set by the CCS, so in a way, it is inherently short circuit proof.

The other main advantage of the shunt reg is that it is bi-directional. In a series reg any transients generated on the load rails will bounce back against the series device output, causing it to switch off until the energy is dispersed somewhere. In a shunt reg, the transient is absorbed by the shunt device and error amp working in combination, thus leading to less unsettling of the load circuitry.

Now that has probably opened a can of worms!
  Reply With Quote
Old 23rd July 2014, 11:45 AM   #4
udok is online now udok  Austria
diyAudio Member
 
Join Date: Jul 2011
You mentioned some good points in favor of shunt regulators!

Have you include output caps ESL/ESR in your simulation? This may be important for stability.

Cheers,
Udo
  Reply With Quote
Old 23rd July 2014, 12:49 PM   #5
Ketje is offline Ketje  Belgium
diyAudio Member
 
Join Date: Dec 2012
Location: Flanders
Why make things that complicated
Mona
Attached Images
File Type: jpg Sreg.JPG (52.9 KB, 325 views)
  Reply With Quote
Old 26th July 2014, 05:40 AM   #6
diyAudio Member
 
Join Date: Jul 2004
Location: Hastings
Default I'm interested

Hi Druid,
I know little about SS but shunt regs, especially low voltage high current ones, are still generally thin on the ground so I would love to hear about your mods and your findings. Thank you, tim
  Reply With Quote
Old 26th July 2014, 09:44 AM   #7
Ketje is offline Ketje  Belgium
diyAudio Member
 
Join Date: Dec 2012
Location: Flanders
Well,I did it again
The extra electrolytic I put it in the wrong way
This shows the right place ,( I hope )
Mona
Attached Images
File Type: jpg Sreg.JPG (53.8 KB, 287 views)
  Reply With Quote
Old 26th July 2014, 11:25 AM   #8
udok is online now udok  Austria
diyAudio Member
 
Join Date: Jul 2011
Have you actually buld the regulator? Is it stable?
  Reply With Quote
Old 26th July 2014, 01:03 PM   #9
Ketje is offline Ketje  Belgium
diyAudio Member
 
Join Date: Dec 2012
Location: Flanders
Quote:
Originally Posted by udok View Post
Have you actually buld the regulator?
No, diy=do it yourself ,why not let others do something too ?
Mona
  Reply With Quote
Old 2nd August 2014, 10:30 AM   #10
diyAudio Member
 
Join Date: Feb 2009
Location: Wales UK
Sorry for the delay in replying, I have been away and only able to briefly view this post during that time. Many thanks for the contributions.

Udo, you brought up a good point about output capacitor ESL and ESR and the software does assume a perfect capacitor, so out of curiosity I put a 10mH inductor and 10R resistor in series with the output capacitor and all was well. There is a 100nF capacitor in parallel with the output cap, not 22uF as shown on the posted circuit diagram, so this will help reduce the ESR and ESL. As I have previously mentioned, I have been using this regulator for a while now and it is behaving perfectly. However, I am very grateful to you for bringing this up, because it caused me to investigate the regulator output more closely on simulation and whilst the basic mods cause no problems, the more modified version does show some very low level high frequency oscillation, which required a small fix. Bear with me and I will come back to this as I progress and learn how to post pictures of my simulation results on this thread.

Mona, your idea of simplifying the design is a good one, it does actually give a PSRR of -112dB up to around 50KHz, deteriorating to -85dB at 600KHz, which is excellent performance. The error amplifier you have omitted basically gives the TL431 more gain, allowing greater PSRR. I have tried a few tweaks on this and it is possible to improve the PSRR to -130dB, so when I have learned the art of posting results, I will be happy to share those if you want?

Tim, low voltage shunt regulators are a challenge as they offer little voltage headroom for the error amp and other power transistors to operate. However, if they are configured to pull around 1A, which is the case here, they offer other advantages in allowing the introduction of choke regulation of relatively small values. Early in this thread I mentioned Allen Wright's influence on my thoughts some years ago an he was a big fan of choke regulation and so am I.

As I hinted above to Udo, the introduction of inductors can cause their own problems and so have to be treated with care and respect or they can actually make things worse!

Now to find out how to post pictures, many thanks.

Paul
  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
Analogue Metric Shunt Reg problem Almeg69 Power Supplies 47 17th July 2014 09:46 PM
Analog Metric Softstart Board Nirvana5253 Power Supplies 7 29th March 2013 07:38 PM
Analog Metric 2A3 PP Kit x3me00 Tubes / Valves 0 8th August 2012 02:24 PM
FS: Analog Metric DAC TDA1541A S1 Amauta Swap Meet 3 13th July 2011 04:19 PM
Analog Metric grounded grid preamp kit sharpi31 Tubes / Valves 6 18th November 2008 07:59 PM


New To Site? Need Help?

All times are GMT. The time now is 10:30 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