Simplistic Mosfet HV Shunt Regs - Page 167 - 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 2nd March 2011, 09:13 PM   #1661
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Yes. Will do. Thanks Salas.
  Reply With Quote
Old 2nd March 2011, 09:14 PM   #1662
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by Bas Horneman View Post
Just did some quick measurements:

200v=36mA
180v=43,5mA
160v=50mA
But you Vin remains steady? How high input DC you feed?
  Reply With Quote
Old 2nd March 2011, 09:16 PM   #1663
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
The Vin drops as well.
  Reply With Quote
Old 2nd March 2011, 09:20 PM   #1664
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Its a balancing act because you have small sinks and a Vin that sags with increasing CCS. I would say, determine a Vout B+ target first. Simulate your load consumption with proper dummy. Then set R1 and Vout (trimmer) until you get 1.Target B+ 2.Target CCS. 3.Vin remains equal or more than (Vout+15V).
  Reply With Quote
Old 3rd March 2011, 08:45 PM   #1665
rolls is offline rolls  Switzerland
diyAudio Member
 
Join Date: Aug 2007
Hello
I have come across your pages because I am looking for a shunt reg for my tube power amp. I have already tried a CCS to see what was going on. It seems that a CCS blocks the mains dirt, and since then it was able to listen the whole day, not just during the night. Of course the shunt is missing, so output transformer, driver transformer and CCS are fighting against each other.
I have gone nearly through all the pages and I am impressed to notice how nice people are, there has not been a bad word.
I think about the pnp transistor, because I need at least 360V, and I would feel uneasy pushing a 375V transistor nearly to its limit. I have found a Fairchild Darlington, FJPF9020TU, it can stand 15W, and 550V up to 7mA. It is an end of life product, but there are still more than 400 available at Mouser.
Last I would like to thank Salas to be such a creative genius and for his endless patience.

Andre
Attached Files
File Type: pdf FJPF9020.pdf (67.4 KB, 58 views)
  Reply With Quote
Old 3rd March 2011, 10:11 PM   #1666
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
You would need the #967 circuit. Has an HV PNP that drives a 500V NMOSFET. It uses low current defined by the MOSFET's VGS/BJT's collector load resistor. An MJE5731A should hold well since MJE350 has been reported to hold at 330V in an example. I would be careful with the Darlington not to ring in that position, because it has to modify the OLG and PM of the circuit probably. Also the steep hfe curves are not inspiring for mA region linearity. If it will work, its higher Vbe is welcome for stabilizing even better the K170 Jfet as CCS that is nesting in it.
  Reply With Quote
Old 3rd March 2011, 11:44 PM   #1667
rolls is offline rolls  Switzerland
diyAudio Member
 
Join Date: Aug 2007
Hi Salas
I see darlingtons could be troublesome. Ringing seems to be the main problem with this shunt, even if I think that it is not intrinsic in this circuit.
I have also the idea to move the FET to the negative side. This way the transistor could be a npn, and the following a p-ch Mosfet.
Personally I am going through all the options theoretically in the first place, because when I am working on the amp I have to be very careful, this one starts with 750V, but the tubes are stacked, there is one ccs for both on the negative side, then one shunt for the driver, about 200V, another one for the output tube, from 360V- 400V. I think nobody has done this before, but I don't want to remove the ccs any more, so I have to go the full monty.
Thank you
Andre
  Reply With Quote
Old 4th March 2011, 12:15 AM   #1668
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
The #967 has 90deg phase margin. In shunt the problems start when the load becomes inductive. You could try cascoding MJE350s since NMOS HV is easier to get is another option. It shortens PM by 10deg only theoretically. I use NPN drive & PMOS output in the LV circuits, its certainly feasible if you have PMOS with enough Vmax for your application. See it has as much transconductance as the IRF840 at least, else the Zo is going to rise. Good luck.
Attached Images
File Type: gif SSHVcasc.gif (7.0 KB, 357 views)
  Reply With Quote
Old 4th March 2011, 09:59 PM   #1669
rolls is offline rolls  Switzerland
diyAudio Member
 
Join Date: Aug 2007
Thank you for your help. I think it is time to start now with a trial board.
  Reply With Quote
Old 4th March 2011, 10:16 PM   #1670
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
@salas,

what is your take on connecting a zener in series with the collector of the MJE350 to address Vceo issues when output voltage is greater than 300 volts?
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  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
Regs - Shunt vs Series richie00boy Solid State 42 14th March 2013 06:45 PM


New To Site? Need Help?

All times are GMT. The time now is 11:45 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