Power supply help - 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 19th June 2008, 06:45 PM   #1
diyAudio Member
 
Join Date: Dec 2006
Default Power supply help

So this is my first "complicated" power supply I'm making and I don't know where to start. Its for a mono version of this amp.

It needs to be able to supply 410V and about 125ma (I'm simply halving what the transformer he used in his schematic, a hammond 372JX, could provide in ma). Its a bit of over kill but I want to use my 4B32's to rectify the supply (half wave each and have about a 12v voltage drop, 16v MAX. Page on them. ). I want to go with a simple LC filter as I have had problems in the past with capacitor input when using gas rectifiers.

The part I really need help with is making it a tube regulated supply. I don't have the foggiest idea of where to begin (though I know I want to somehow fit a 6C33C in the design for the irony). If it makes any difference I plan of having the transformers custom made. This amp is for a sub woofer as well.
  Reply With Quote
Old 20th June 2008, 01:24 AM   #2
diyAudio Member
 
Join Date: Dec 2006
Sorry for the double post but I saw no option for editing my previous post.
To get the basic layout of the power supply I decided to use a program (PSUD2) instead of doing all of the math out by hand (mainly because I lost the formulas my friend gave me and I didn't feel like deriving my own). I'm not 100% sure I'm using it right (I had never considered the resistance of the mains transformer windings and the filter capacitor). I also couldn't find a model for the 4C32 so I used one for the 3B28 (next best thing as far as I know).
As far as I can tell from the program a 245-0-245 transformer (490VCT) into a hammond choke (10H, 82ohm) with a good valued capacitor will give me ~410v depending on the load (was assuming the primary impedance of the output transformer a good value for Rload? I've never designed a power supply this way. I've always been a "trial-error-eh?-meh...good enough" kind of guy).

Is this a good starting point or did I screw something up in the program?
  Reply With Quote
Old 20th June 2008, 02:19 AM   #3
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
If you really want to experience new things, how about an off-line flyback? It's far more efficient in every respect (stray fields/EMI, cost, size, weight, output regulation, current limiting, losses, life expectancy...) And you only need 50W...
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 20th June 2008, 03:01 AM   #4
diyAudio Member
 
Join Date: Dec 2006
Quote:
If you really want to experience new things, how about an off-line flyback? It's far more efficient in every respect (stray fields/EMI, cost, size, weight, output regulation, current limiting, losses, life expectancy...) And you only need 50W...
Hell no! I've seen fist hand what flyback transformers can do...joe still twitches every once and a while. I stay away from those things...
  Reply With Quote
Old 20th June 2008, 06:21 AM   #5
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
That was not worse than the harm that 490V AC or a 10H choke charged to 100mA can do

I have no experience with tubes, but if this class A choke loaded output stage is properly biased, it should be conducting slightly more than 410V/4800ohm~=90mA when idle (I suppose the pots are intended for bias adjustment). Current consumption may double during negative signal peaks and may drop to 0 during positive peaks, so net current draw remains at 90mA.

BTW: A good 400V flyback SMPS would actually have four 100V outputs in series to allow to use 200V ultrafast diodes. This has nothing to do with the 25KV to 50KV secondaries found on TV flybacks...
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 20th June 2008, 09:11 PM   #6
diyAudio Member
 
Join Date: Dec 2006
Yup I think that is what the pots are for. Really never played with choke loaded tubes seriously but it's suppose to be better.

Is what I've worked out for the power supply correct so far?
How do I regulate it with tubes?
  Reply With Quote
Old 20th June 2008, 10:12 PM   #7
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Here's a thread with some interesting stuff on HV regulators, although the regulators discussed are transistor types.

High Voltage Regulator

Can you post a schematic? And a description of your assumptions or datasheet parameters?

490vrms is ~680 pk, so 410V sounds a little low

What regulated output do you require?

w
  Reply With Quote
Old 21st June 2008, 12:48 AM   #8
Banned
 
Join Date: Jan 2008
Blog Entries: 2
I'm not really a tube guy, but this is what I think a tube regulator might look like.

Click the image to open in full size.

w
  Reply With Quote
Old 25th June 2008, 11:51 PM   #9
diyAudio Member
 
Join Date: Dec 2006
This is what I've been playing with but I don't know what certain values should be. Any help would be appreciated.
Attached Images
File Type: png untitled.png (80.6 KB, 209 views)
  Reply With Quote
Old 28th June 2008, 12:33 AM   #10
Banned
 
Join Date: Jan 2008
Blog Entries: 2
OK, like I said, I don't really do tubes, I did them in school years ago, but it's been silicon ever since...

I had a play with PSUD2 and I looked at your circuit. From first principles the topology you have chosen will produce a peak output of <346V with 245v secondaries (rms volts * sqrt(2)). Therefore the value you should enter in the transformer properties is 245 not 490.

Entering the values for the choke and cap as in your circuit gives me an output voltage of ~200V with a 5k load. 5k is not an unreasonable figure, but you can backfigure the load by dividing your target voltage by the anticipated current draw 410/0.125 =3280ohms. V=IR.

Messing with the capacitor resistance value (ESR) affects mostly the ripple, so this is a parameter with a minor influence on your output voltage. I'm a bit surprised that so much voltage is lost as a result of the tx resistance and choke, but you live and learn.

To get the voltage you want with the 2-tube fullwave rectifier you will require a much higher voltage secondary, about twice what you have now.

Maybe somebody who's a bit more up to speed on this will chip in.

w
  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
Split Voltage Switching Power Supply for Power Amp vectorplane Swap Meet 2 24th April 2011 12:48 AM
LTspice tool for power amp power supply component evaluation andy_c Software Tools 2 23rd August 2009 06:10 PM
Can i use a computer power supply to power audio amplifiers? destroyer X Solid State 91 25th September 2006 05:36 AM
selling high current power supply for power amps. ericpeters Swap Meet 0 14th January 2005 03:21 PM
heater supply (xformer specs are 6.3V 2.5A) as supply for a power LED? jarthel Tubes / Valves 10 21st July 2003 02:30 PM


New To Site? Need Help?

All times are GMT. The time now is 11:40 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