Simplistic Mosfet HV Shunt Regs - Page 300 - 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 10th May 2012, 10:31 AM   #2991
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
Quote:
Originally Posted by Sergelisses View Post
Hi Salas

Is it a good idea to replace a 5AR4 by a HV Shunt reg ?

Best regards
Serge
Let me know if you do and how you liked it .
  Reply With Quote
Old 10th May 2012, 10:51 AM   #2992
diyAudio Member
 
triode_al's Avatar
 
Join Date: May 2004
Location: Westland
Blog Entries: 1
Default Counter intuitive trouble with SSHV1

Hi,
I built a Salas shunt for my preamp. The preamp draws between 30 mA, design is for 250V.

However I get some strange effects with the SSHV1.
I get less and less current out of it.

The current source I use is with 2SK585, slightly higher knee (5V/about1A) than the stock IRF6910 (4V/about1A).
My LEDS: an array of 5 red LEDS on 68k giving 7,9 volt. The source voltage is around 3 volts (across the bias resistor) and this starts to drop as the current demand increases.
With a test on a lab supply set I got 58mA (rbias=47ohm) out of it, with 270V in, but once installed in the preamp the current source drops in value.
I get
  1. 39 mA with 74 ohm raw 298V
  2. 41 mA with 68 ohm; the input starts to drop. 297V
  3. 40 mA with 51 ohm. in = 291V
  4. 30 mA with 42 ohm. in=249V
Pretty counterintuitive!
At the same time the raw input starts to drop. This means the supply is loaded (but the current drops ).

I reduced my output from initial 218V to 200, now it is barely 185V when the regulation starts.

My power supply: 300V AC (rs=50 ohm) / 5R4GY / L=1,75, 200ohm / C= 10 uF / L= 7 H, 300 ohm / 30 uF.
So it is choke loaded. The output starts to sag from 300V DC down to lower than 250V. I tried a solid state drop-in rectifier, same effects, but drop is less. The LCLC regulates well.
There is no oscillation visible on my scope.

Is the LED array to small? Do these effects then happen?

I first had an OD3 and a EL84 shunt on 250V; this gave a higher raw voltage in: 325 volts DC could be obtained. (But the Salas SSHV1 is so much more silent, I can post the pictures).

Has anybody noted such strange behaviour (not enough current and dropping) and detoriation (sagging output over time)? Every on-off cycle reduces the current capability???? The voltage of the knee where the shunt starts seems to drop every time. [Maybe I should add the 12Vzener to guard the shunt IRFIB5N65A ...]

My guess: the LEDS are too weak. I already added one extra to go from 4 to 5 pieces . Add one more ?? or replace one red (1,58V@4mA) with yellow (2V@4mA).

Hope this is clear
albert
__________________
DAC TDA1541 S1; Kondo post-I/V filter; MC30-Super --> two stage RIAA; Pre: SP-6 clone ; F5 ; 300B PP ; ESL 57

Last edited by triode_al; 10th May 2012 at 10:53 AM.
  Reply With Quote
Old 10th May 2012, 11:57 AM   #2993
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
There are two parts to the supply.
The CCS and the Shunt regulator.

You can build and test the CCS without any of the shunt components in place.

Build the CCS.
Apply a low safe working voltage. Maybe 20Vdc.
Attach a 1r0 power resistor from the CCS output to Power Ground.
Measure the voltage across the 1r0 dummy load resistor.
Adjust your CCS current to the value you need.

Remove the temporary low voltage supply.
Add into the build all the shunt components.
Replace or parallel the big voltage dropper in the sense circuit to reduce the regulated voltage to ~20Vdc. Now apply a temporary low voltage to the CCS input and see what current is flowing in the CCS. Measure the regulated output voltage. Determine the Vdrop across the CCS that allows correct operation of the CCS and the shunt regulator. This is the absolute minimum DC voltage that can be allowed during high voltage operation for the CCS+Shunt to work properly.
Now take off the temporary parallel resistor jumper to reset the sensor circuit to the high voltage version.

Both parts of the regulator have been tested. It is now relatively safe to apply high voltage to the CCS input. Measure the CCS Vdrop. It must be bigger than that minimum value you determined during the LV testing.
It must remain higher than that minimum Vdrop even when mains voltage has dropped to the minimum supply voltage that your electricity supplier has given you.
__________________
regards Andrew T.
  Reply With Quote
Old 10th May 2012, 12:28 PM   #2994
diyAudio Member
 
triode_al's Avatar
 
Join Date: May 2004
Location: Westland
Blog Entries: 1
I added a LED, and this solved the issue.
Now I can get:
  • 57 mA with 68 ohms, V in is 287V
  • 64 mA with 56 ohms, V in is 287V
  • 240V out, with 21 mA shunt current (sub Herz not nice)
  • but 210 is better, with 30 mA shunt draw
looked at the calculator again and this confirms my findings: at a higher current the voltage over the bias resistor drops (of course ).

The sub Herz flutter remains a problem; the shunt needs quite some current to cope with it and get a very smooth output line.
With a solid state rectifier I see some residue of below 1 mV pp of rectifier peaks; with the tube rectifier I did not see it.
So my next step: revert to the tube.
albert
__________________
DAC TDA1541 S1; Kondo post-I/V filter; MC30-Super --> two stage RIAA; Pre: SP-6 clone ; F5 ; 300B PP ; ESL 57
  Reply With Quote
Old 10th May 2012, 12:32 PM   #2995
diyAudio Member
 
triode_al's Avatar
 
Join Date: May 2004
Location: Westland
Blog Entries: 1
Quote:
Originally Posted by AndrewT View Post
There are two parts to the supply.
The CCS and the Shunt regulator.

You can build and test the CCS without any of the shunt components in place with a low voltage supply & 1 ohm shunt & adapted LED resistor.
Yes this s good idea. Much better than my tweaking method (in situ, replacing parts . . .)
albert
__________________
DAC TDA1541 S1; Kondo post-I/V filter; MC30-Super --> two stage RIAA; Pre: SP-6 clone ; F5 ; 300B PP ; ESL 57
  Reply With Quote
Old 10th May 2012, 03:06 PM   #2996
diyAudio Member
 
Join Date: Nov 2003
Location: Near PARIS
Quote:
Originally Posted by nigel pearson View Post
Let me know if you do and how you liked it .
I have never worked with tubes so i am not sure that it's a good idea

Serge
  Reply With Quote
Old 10th May 2012, 03:25 PM   #2997
diyAudio Member
 
Join Date: Mar 2007
Location: Oxfordshire
Someone will say I am sure . I have a design to use near my computer . Keeping it neat and tidy helps . I probably will not get time to do it .
  Reply With Quote
Old 10th May 2012, 07:49 PM   #2998
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by triode_al View Post
I added a LED, and this solved the issue.
Now I can get:
  • 57 mA with 68 ohms, V in is 287V
  • 64 mA with 56 ohms, V in is 287V
  • 240V out, with 21 mA shunt current (sub Herz not nice)
  • but 210 is better, with 30 mA shunt draw
looked at the calculator again and this confirms my findings: at a higher current the voltage over the bias resistor drops (of course ).

The sub Herz flutter remains a problem; the shunt needs quite some current to cope with it and get a very smooth output line.
With a solid state rectifier I see some residue of below 1 mV pp of rectifier peaks; with the tube rectifier I did not see it.
So my next step: revert to the tube.
albert
If not having an ID/VGS graph of an alternative CCS MOSFET component to readily refer to, it certainly takes some experimentation for the level of the LEDs reference. But you saw that. You can also filter the main voltage reference in the shunt part with more uF to depress 1/f better but it will take a zener to protect the Jfet current reference from sustained overvoltage during charge up (see SSHV2). Transcoductance and ID curve of chosen MOSFETS plays a role on how well they reject with given spare mA at 1/f also. In general, the hotter the better (within practical bounds).
  Reply With Quote
Old 11th May 2012, 06:45 AM   #2999
diyAudio Member
 
triode_al's Avatar
 
Join Date: May 2004
Location: Westland
Blog Entries: 1
Yep. I will add either a TIP50 (Hfe 150, 400V max) or an IRFIB5N65A (650V mosfet) as gyrator: with a 10k resistor and a 10-47 uF capacitor. This regulates sub-Herz a bit better than a 100H eChoke, I noted.
And maybe add a 220 uF electrolytic.
The 2SJ585 has embedded zeners, that is why I choose this one over the 2SJ449 I also have, both being 250V. So increasing to say 4 uF would be possible without extra zener.

Quote:
You can also filter the main voltage reference in the shunt part with more uF to depress 1/f better
You mean increasing C2? (I have 1,2 uF), I have a 250V type (Philips MKP).
SSHV1.png

Just an idea - Could it be that with this type running against its max that I get this noise? Because the shunt seems to have behaved better initially.

Thanks, albert
__________________
DAC TDA1541 S1; Kondo post-I/V filter; MC30-Super --> two stage RIAA; Pre: SP-6 clone ; F5 ; 300B PP ; ESL 57
  Reply With Quote
Old 11th May 2012, 08:49 AM   #3000
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Not sure if stressing the dielectric can do such. I use 400V there. More inclined to that the different Mosfets can be wilder at 1/f and you need more C2 value. But strap a 12V Zener from C2&R9 node to +Vo rail (cathode up) along upping the capacitance not to zap the JFET.
  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 01:17 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