Go Back   Home > Forums > >

Tube use? 24->300V large cap charger with 300V 150mA reg
Tube use? 24->300V large cap charger with 300V 150mA reg
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
Old 3rd March 2021, 04:52 AM   #1
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
Default Tube use? 24->300V large cap charger with 300V 150mA reg

24V dc to 300V dc capacitor charger with regulation (300V at 150mA at 78% efficiency): https://www.analog.com/media/en/tech...ets/lt3751.pdf

So this not only can cope with managing inrush on a 2+mF 300V cap, it can also then regulate current output too. User configurable max charging limit too..

Seems it may be of interest to tube users.. now if only there was a larger regulated 500mA-1A version.

There’s also a coilcraft transformer specifically for this..
  Reply With Quote
Old 3rd March 2021, 05:57 AM   #2
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
Actually with 150mA you could make all the 6SN7+6AS7 single tube amps.. one per channel and you're laughing. 6mF + 5.1R resistor then 1.5mF and 2K and you've got a -90dB at 100Hz second order passive filter. Probably the quietest bottle head amp out driven by a SMPS. (would need to check the cap high frequency responses before claiming that though).

The LT3750 is essentially the non-regulating version of this and works on 6-24V, there's no feedback from the secondary side of the transformer. I thought about using this as an initial charge up of the system before switching out for a larger standard switched mode power supply where it wouldn't see the pre-charged caps as a short.

Last edited by NickKUK; 3rd March 2021 at 06:01 AM.
  Reply With Quote
Old 3rd March 2021, 06:54 AM   #3
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
I found this thread on the subject previously but I don't think it goes into much more than using it as standard 400V: LT3751 Driven, +/-400V Shunt Regulated Supply

Actually using a Coilcraft 3460-BL that's 50A output 12-24V input and 500V out: GA3460-BL | Coilcraft

So theoretical max of 600VA (50A*12V) now that means you can change switching fet in parallel. I missed the examples on the phone this morning: https://www.analog.com/media/en/tech...ets/LT3751.pdf A number of ideas - including a 42A capacitor charger (12V in and HV out), a 100-400vdc in 100-400vdc out etc etc.

The interesting bit for me is that it could provide the power I need albeit with a 20Vripple as documented in the thread above. Not a problem if you have output available only issue is how much current secondary side do I have to play with.

So a 500W 12-24V supply, a current limiting and capacitor short aware step system like this, and it could be two steps with a capacitor to give a decent power supply. Not as efficient as a single step but it's isolated unlike a straight AC-boost PFC to 390V and it copes with it's own inrush automatically.

The LTspice model seems good, I'm just trying with a 6mF cap to see the resulting output.

With appropriate setting of resistors it's possible to get 200V and 300mA+ out of it according to the data sheet but this is dependant on the transformer.

Last edited by NickKUK; 3rd March 2021 at 07:22 AM.
  Reply With Quote
Old 3rd March 2021, 10:46 AM   #4
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
This model is driving a 5.1 ohm 6mF LPF and the results seem pretty decent:

Screenshot 2021-03-03 at 11.44.09.png

The model is super slow but 200+V and less noise than I was expecting (MHz showing harmonics I believe) but still.. interesting.

Last edited by NickKUK; 3rd March 2021 at 11:02 AM.
  Reply With Quote
Old 3rd March 2021, 12:06 PM   #5
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
A little longer in the model, using filter to capture the noise properly now we have more data:

Screenshot 2021-03-03 at 13.03.10.png

Screenshot 2021-03-03 at 13.07.26.png

This looking more promising. This is using a simple 24V source rather than a SMPS model, but still this is decent and I'd expect an SMPS with PFC to have less harmonics lower down.

Last edited by NickKUK; 3rd March 2021 at 12:08 PM.
  Reply With Quote
Old 3rd March 2021, 01:22 PM   #6
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
I've attached the LTSpice model - this is takes the model found in the previously referenced thread then applies:
* Updated transformer for 50A Coilcraft transformer
* Adjusted the model to follow the 42A capacitor charger model but instead of 500V it's set to 200V) it also uses two mosfets in parallel for switching.
* added a 5.1ohm + 6mF cap in the feedback loop - this is a 0.5Hz LPF
* changed the load resistance to 280 ohm to give 500mA draw
* I can remove C8..

I'm currently running a model with a second 500ohm+750uF cap to see if it reduces the noise floor further.

The linear supply was, on the whole, quieter except the 100Hz and harmonics created by non-PFC current spike which needed some further draconian LPF to get them to -90dB which meant even more power needed.

This is a non-isolated DC-DC supply, so it would be borrowing it's isolation from the SMPS - I'd probably use a Meanwell 500W 12V isolated SMPS.

This seems to have a need for about 300W possibly 600W. I'd need to make an average plot rather than the current spikes by eye approximation.
Attached Files
File Type: asc LT3751_Patrick.asc (10.8 KB, 5 views)

Last edited by NickKUK; 3rd March 2021 at 01:24 PM.
  Reply With Quote
Old 3rd March 2021, 02:36 PM   #7
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
Update on model..
Screenshot 2021-03-03 at 15.35.15.png
  Reply With Quote
Old 3rd March 2021, 02:58 PM   #8
v4lve lover is offline v4lve lover  Netherlands
diyAudio Member
 
Join Date: Aug 2010
Location: Surrounded by glass, no really my room is full of tubes
Tube use? 24->300V large cap charger with 300V 150mA reg Tube use? 24->300V large cap charger with 300V 150mA reg
Ferryster 1068YMD UC3843 controlled im working on that.


Thread here: There is little interest in Flyback from the audio folks


Development topic 12=>200-450V 100mA flyback.


If you need some pointers on how you get rid of the AM/FM band interference. Look up AN101F by Jim williams
  Reply With Quote
Old 3rd March 2021, 03:52 PM   #9
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
Quote:
Originally Posted by v4lve lover View Post
Ferryster 1068YMD UC3843 controlled im working on that.


Thread here: There is little interest in Flyback from the audio folks


Development topic 12=>200-450V 100mA flyback.


If you need some pointers on how you get rid of the AM/FM band interference. Look up AN101F by Jim williams
Thank you - that looks good and I'll read it later tonight, there's a few interesting tools out there, but this is more specific: RF Tools | LC Filter Design Tool

I've used active LPF before however they tended to be opamp based. I've put in a 60Khz 5th order butterworth, let's see what comes out and how much drop I get keeping with passive.
  Reply With Quote
Old 3rd March 2021, 05:13 PM   #10
NickKUK is offline NickKUK  United Kingdom
diyAudio Member
 
Join Date: Dec 2019
The interesting thing with the LT3751 (apart from the PCB ground pad) is depending on the Feedback pin, it will switch behaviours - charge, regulate or no load.

Charge - it goes for maximum charging depending on the limits programmed.
Regulate - once charged, it then switches duty cycle with a focus to reduce noise.
No-load- it goes into async/on-demand to provide power as needed.

Naturally you can program it to always sit in charge mode, but I'm hoping that it could be made to run in regulation mode.

Running another model, but let's see..

Screenshot 2021-03-03 at 18.14.29.png

Blue - after the first filter (and where the FB loop attaches) and Green - after the second filter! An LDO would probably do well here lol!

Early into the model but I suspect given an LDO/smaller second order, that would be great:
Screenshot 2021-03-03 at 18.19.31.png

Last edited by NickKUK; 3rd March 2021 at 05:20 PM.
  Reply With Quote

Reply


Tube use? 24->300V large cap charger with 300V 150mA regHide this!Advertise here!
Thread Tools

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
Noir, a two transistor headphone amp: class-A, single ended, 150mA bias Mark Johnson Headphone Systems 301 9th May 2021 07:31 PM
good driver tube with 150mA heater? SemperFi Tubes / Valves 21 14th May 2016 09:32 PM
WTB Lundahl LL1688-150ma brommermartin Swap Meet 0 4th March 2016 10:37 AM
Mosfet reg vs Mosfet shunt reg linuxfan Power Supplies 3 30th May 2013 01:30 AM
5kV DC / 150mA PSU for sale Bakmeel Swap Meet 0 1st November 2002 01:09 AM


New To Site? Need Help?

All times are GMT. The time now is 09:46 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki