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

First Linear Power Supply Build Questions
First Linear Power Supply Build Questions
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 August 2019, 06:06 PM   #11
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Taking into consideration concerns stated so far, I realize it would be wise to stay with my original calculations using 1.5A as the required current.

As for CLC filtering, information I am seeing so far mentions its applications in SMPS and DC-DC converters? Either way, while it may be beneficial I am trying to keep costs in check and may have to forgo including additional features for now.

I am under the impression that the general circuit I have is sound, albeit inefficient?

Thanks to everyone offering input, I appreciate it!
  Reply With Quote
Old 22nd August 2019, 05:19 PM   #12
phase is online now phase  United States
diyAudio Member
 
Join Date: Oct 2004
If you are watching the budget, I would get a 12-0-12 toroidal transformer, and power supply board (with your choice of regulation)from that auction site, and get some quality replacement caps from a known supplier, or even a well rated seller of surplus parts if they can provide date codes.
That will give you a real +\- power supply for headphone/preamp/dac use.

A fuse before the transformer at the least is good practice too. There are power cord sockets that have a fuse built-in for reasonable prices for low current applications.
  Reply With Quote
Old 23rd August 2019, 06:53 AM   #13
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Quote:
Originally Posted by LateraLiz View Post
Regarding your note on short circuit conditions, diodes D2 and D3 in the schematic are included based on the suggestion to include them on the LM317 datasheet. Specifically, in the event "the input is shorted to ground during a fault condition, protection diodes provide measures to prevent the possibility of external capacitors discharging through low-impedance paths in the IC" and D2 and D3 prevent capacitors discharging into the output of the regulator. Does this satisfy the concerns you mention?
Short answer - no. Those considerations with the diodes are to re-direct currents from charged up capacitors under short-circuit conditions and work well, but only with the LM317 used within the datasheet parameters. My concern was the potential of going beyond the datasheet's maximum, something those diodes don't address.

Quote:
Regarding the regulation of my transformer, I do not know if it does or doesn't have regulation.
Regulation isn't a feature of a transformer, all have it to some degree. Its a measure of the transformer's windings resistance. Regulation is expressed as a percentage change in the output voltage between zero and full-load. I looked at the datasheets at the links you posted and neither gives any indication about the regulation - but for 100VA in an EI transformer I'd guess in the region of 10%. When the regulation figure is known then the maximum off-load voltage out of the trafo can be calculated.

Incidentally I commend your selection of a split-bobbin type of transformer. They generally have lower leakage current from mains due to lower inter-winding capacitance.
__________________
I know you think you understand what you thought I said but I'm not sure you realize that what you heard is not what I meant - Alan Greenspan
  Reply With Quote
Old 23rd August 2019, 07:21 PM   #14
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Quote:
Originally Posted by phase View Post
If you are watching the budget, I would get a 12-0-12 toroidal transformer, and power supply board (with your choice of regulation)from that auction site, and get some quality replacement caps from a known supplier, or even a well rated seller of surplus parts if they can provide date codes.
That will give you a real +\- power supply for headphone/preamp/dac use.

A fuse before the transformer at the least is good practice too. There are power cord sockets that have a fuse built-in for reasonable prices for low current applications.
While budget may be among the chief drivers for this project, its not the primary directive. Buying a kit would circumvent the learning process inherent in designing even a simple power supply design. And that would defy the primary directive.

This and the fact that in addition to this project, I already have the parts and pcb done and ready to assemble for the Goldpoint VG2 circuit to take the output from this power supply and split it into a dual supply for audio use. Which is a needlessly complicated way of obtaining a split supply sure, but it sure does satisfy the primary directive.

And I love the idea of using a power cord socket with a built in fuse - hadn't thought of that, thanks for the tip!
  Reply With Quote
Old 23rd August 2019, 07:36 PM   #15
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Quote:
Originally Posted by abraxalito View Post
Short answer - no. Those considerations with the diodes are to re-direct currents from charged up capacitors under short-circuit conditions and work well, but only with the LM317 used within the datasheet parameters. My concern was the potential of going beyond the datasheet's maximum, something those diodes don't address.


Regulation isn't a feature of a transformer, all have it to some degree. Its a measure of the transformer's windings resistance. Regulation is expressed as a percentage change in the output voltage between zero and full-load. I looked at the datasheets at the links you posted and neither gives any indication about the regulation - but for 100VA in an EI transformer I'd guess in the region of 10%. When the regulation figure is known then the maximum off-load voltage out of the trafo can be calculated.

Incidentally I commend your selection of a split-bobbin type of transformer. They generally have lower leakage current from mains due to lower inter-winding capacitance.
So I spent some time reworking this project based on some of the feedback given, which led me to replace the LM317 with the similar LM338, distinguished by its ability to output upwards of 5A and 7A surge current.

With 30vdc @ 3a output required, the LM338 should forgo some of the inefficiency concerns with the LM317. As such it doesn't exceed the datasheet specifications and therefore the protection diodes would indeed maintain their protective faculties, is this correct?

With a 28vac @3.57a trafo, assuming the appx. 10% regulation figure you provided, achieving a 30vdc shouldn't be an issue. Unless I'm misunderstanding what you are saying, that is. I appreciate you taking the time to look over those datasheets and provide some pointers for me!
  Reply With Quote
Old 23rd August 2019, 07:50 PM   #16
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Quote:
Originally Posted by jean-paul View Post
Why LM317? There are better ultra low drop regulator ICs availabe. I would use CLC filtering before the reg as well. With a modern IC you can probably use a 24V transformer and have less energy wasted in heat. Maybe not a design goal but cooler electronics also live longer. A key parameter is the desired output current.
You were right, LM317 was a poor choice and current was a necessary output parameter to consider. With this in mind, required current is 3A @ 30vdc output which is better served using the LM338. I have also replaced the transformer with one rated at 28vac @3.57a. The LM338 was the only IC I found capable of handling upwards of 5A current in addition to handling over 35vdc input. To keep things cool ill be adding a fan(s) as well as the obvious heatsinks.

CLC filtering was a good idea, thanks for sending me in that direction. At this time I will include a CRC filter, while less effective at reducing ripple than CLC, its still better than just C.

Having calculated that I'll need 60,000uF for 0.5v of ripple at 3a, I'll be taking the rectified DC signal from the bridge through 30,000uF (as 3x 10,000uF in series), followed by R (~0.17 oHms), and 30,000uF after that. Does that sound about right?
  Reply With Quote
Old 23rd August 2019, 08:15 PM   #17
guavatone is offline guavatone  United States
diyAudio Member
 
Join Date: Apr 2008
http://www.hammondmfg.com/pdf/5c007.pdf

Great guide for calculating current.

AS-2215 - 200VA 15V Transformer - AnTek Products Corp

Good for 30V regulated or +/- 15v

Sounds like you need to define your design needs. In general power amps arenít regulated. Maybe youíll do better with a simple pass transistor voltage stabilization.
  Reply With Quote
Old 23rd August 2019, 08:25 PM   #18
LateraLiz is offline LateraLiz  United States
diyAudio Member
 
Join Date: Aug 2019
Quote:
Originally Posted by guavatone View Post
http://www.hammondmfg.com/pdf/5c007.pdf

Great guide for calculating current.

AS-2215 - 200VA 15V Transformer - AnTek Products Corp

Good for 30V regulated or +/- 15v

Sounds like you need to define your design needs. In general power amps arenít regulated. Maybe youíll do better with a simple pass transistor voltage stabilization.
Isn't that what I'm doing here - designing a regulated, single output, power supply based on the (now) LM338?

Design needs have been established as 30vdc at 3a output.

Forgoing a toroid tranfo for now to keep cost in check, but thank you for providing a link for what appears to be a well priced option in the future. Also, the Hammond calculation pdf is very helpful, thank you!
  Reply With Quote
Old 24th August 2019, 11:08 AM   #19
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Quote:
Originally Posted by LateraLiz View Post
With 30vdc @ 3a output required, the LM338 should forgo some of the inefficiency concerns with the LM317. As such it doesn't exceed the datasheet specifications and therefore the protection diodes would indeed maintain their protective faculties, is this correct?
The protection diodes aren't addressing the issue I've been referring to, which is potentially exceeding the DS max input to output voltage under short-circuit conditions.

Quote:
With a 28vac @3.57a trafo, assuming the appx. 10% regulation figure you provided, achieving a 30vdc shouldn't be an issue.
Assuming 10% regulation with a 28VAC trafo, your offload voltage under nominal mains input will be 28*sqrt(2)*1.1 - 1.2V = 42.4V. A short-circuit applied under this condition is potentially going to destroy the regulator. With higher than nominal mains the likelihood of device destruction is going to be greater.

Quote:
Unless I'm misunderstanding what you are saying, that is.
It does indeed look that way.
__________________
I know you think you understand what you thought I said but I'm not sure you realize that what you heard is not what I meant - Alan Greenspan
  Reply With Quote
Old 25th August 2019, 08:53 AM   #20
icesteve is offline icesteve  Australia
diyAudio Member
 
Join Date: Jul 2016
Location: Sydney
While you're experimenting, you could also take a look at the current boost configuration commonly used with these devices. Basic example here:
LM317 Adjustable Voltage current Boost Power Supply
You said you have fan in your design - and you're going to need it (!) - the 317/337 will get extremely hot you will discover. It's dissipating power (lots of heat) at the current you are drawing in the load (I) x (Vin - Vout).
And as you experiment you'll then realise that you don't want the fan on all the time...so a little thermistor control circuit needed next. Then you'll perhaps want some current limit control. Welcome to experimenting with electronics
  Reply With Quote

Reply


First Linear Power Supply Build QuestionsHide 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
Questions about amp camp amp and linear power supply Jonse Pass Labs 22 17th February 2018 07:37 PM
Op amp Linear power supply Marksd Power Supplies 158 27th January 2018 08:44 AM
Linear DAC power supply jean-paul Analog Line Level 0 30th April 2015 10:53 AM
Help a novice steadily build a linear 12V power supply? SGK Power Supplies 117 27th May 2014 07:38 AM
Tubelab SE build and power supply questions. Binaural Tubelab 54 3rd March 2010 03:20 AM


New To Site? Need Help?

All times are GMT. The time now is 10:18 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki