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

'150W' 12VDC isolated 25kHz step-up smps for B+
'150W' 12VDC isolated 25kHz step-up smps for B+
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 9th October 2017, 07:32 AM   #1
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Default '150W' 12VDC isolated 25kHz step-up smps for B+

eBay has a cheap isolated smps to generate B+ from 12VDC with enough throughput for a substantial valve amplifier. This is a neat way for DIY to not require any AC mains wiring within an amp. A suitable mains plug-pack, with regulated 12VDC and enough current to suit valve heaters and this dc-dc, is all that is needed.

Click the image to open in full size.

I just got two units in from:
150W Inverter Boost Board Transformer DC-AC Converter 12V to 110V 200V 220V 280V | eBay

A recent thread was on the diodes in that power supply:
Suggestions needed for a diode to rectify 37kHz

The primary side uses a SG3525A controlled push-pull with a YP17575C fet each side on a heatsink. Can't find datasheet for the FET but it seems to be pretty good for the job. PCB layout is good for leaded parts. The secondary offers an isolated 0-110-200-220-280V winding/taps, and a full bridge of HER207 fast diodes.

A basic doubler using the 0-220V winding provides a simple means to generate approx 430Vdc for a PP output stage, as well as 215V for preamp stages, and suitable for a push-pull pair of any common valve such as 6L6GC etc., as the output power delivery seems to be fine for at least 60-100W.

A doubler allows two 300-350VDC small electrolytics to easily fit on the pcb -
I used 10uF which have sufficient ripple current capability (especially due to the 25kHz fundamental ripple - 50kHz as seen from the B+ output). The voltage rating needs to cover the maximum voltage that could be output - as the output voltage is unregulated, it will increase with module input voltage (so idle voltage could exceed 500V if the input dc exceeds 14V).

I removed the HER207 diodes, and the blue connector, and fitted 2x UF4007 on the rear for the doubler diodes, which gave a neat small switching current loop along with the electrolytics. There is no need for 'larger' or better diodes imho, and the capacitance of larger diodes will just add to switching losses.

The pcb pads for the HER207 diodes can be conveniently used for inserting some low value resistors, or inductors, to act as a balanced high-frequency filter with a shunt capacitor on the rear of the output terminals.

As I had some smt caps, I was able to easily fit them to minimise some switching current loop lengths, but its doubtful whether any noise would be noticeable (it would probably need a good spectrum plot of the final amp to detect).

I only had a 12Vdc 5A plug pack (12VDC 5A Desktop Power Supply - Fixed 2.5mm Plug | Jaycar Electronics) so just tested to 97mA 41.2W loading on 426V output, with 3.8A input.

No load loss within the dc/dc module is about 2.5W with 12Vdc input, and that loss increased to about 3.3W for 41W output - where FET heatsinks didn't rise by more than 2-3degC, and transformer winding outer surface was about 20degC rise.

If going this DIY path, then I recommend using a good quality AC smps plugpack with a protective earth pin that connects through to the 12Vdc output, as that then provides a protective earth path for the amp chassis, and the plugpack to have current limiting. As an example - the compliance file for my plugpack is https://www.jaycar.com.au/medias/sys...aSheetMain.pdf
  Reply With Quote
Old 16th October 2017, 02:21 PM   #2
speaker is offline speaker  United States
diyAudio Member
 
speaker's Avatar
 
Join Date: Mar 2004
Location: USA
Have you looked at the output of yours under load on a 'scope? Just curious how well they do and how clean the voltage delivered is.

(I just purchased one of these below. It's a lower voltage DC only variant.)

Click the image to open in full size.

Last edited by speaker; 16th October 2017 at 02:25 PM.
  Reply With Quote
Old 17th October 2017, 07:14 AM   #3
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
At the 41W output loading, I had a bit over a 100mV sawtooth ripple on 12Vdc input, but I was using a standard 100:1 probe with ground lead so signal was a bit noisy. I checked for output ripple on my Kiethley 197 on AC and lowest 200mVac range and the ripple/noise was 'low' but not reliably measurable, but would have been well below 100mVrms. I didn't put the CRO probe on the output, as I was a bit reluctant to damage my $1 USB soundcard interface
  Reply With Quote
Old 17th October 2017, 03:30 PM   #4
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
I've used these many times, usually at 280V for HP/Phono/Preamp service. I also use the 220V AC output with UF5408 doubler to run the Williamson front end of a power amp.

It will fail prematurely if you use a large choke on it's output, and the weak point is the transformer.

A better choice for running power amplifier would be it's big brother at 500W.

MINI DC-AC Inverter 12V to 18V220V/380V 500W Boost Step UP Power Module New Hot | eBay

I am using one of these to power PP 6P3S, using a disassembled ATX power supply for the 12V.

There is also this one: DC-DC 8-32V to +-45V-390V Step-up ZVS High Voltage Capacitor Module Charge Board | eBay

Adjustable output, regulated, however not isolated. I use these in Phono amps. it's Bipolar, too.

Cheers.

Last edited by kodabmx; 17th October 2017 at 03:36 PM.
  Reply With Quote
Old 17th October 2017, 05:37 PM   #5
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Were the units failing within the transformer? Was there a failure mode?
  Reply With Quote
Old 17th October 2017, 06:10 PM   #6
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
In my case the transformer windings got hot enough to melt and short. Haven't had the problem since I stopped using a 4.5H choke input filter. And I use UF5408 or HER208 now. I've also had a failure from the MOSFETs getting too hot. The heatsinks reached over 95c.

Generally I de-rate them to less than half of the stated output power. The 150W inverter is good for about 70W without a fan in 50c ambient temperature.
  Reply With Quote
Old 17th October 2017, 06:43 PM   #7
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Thanks for adding that info. I'm interested to get more of an understanding of your experiences if you don't mind the queries

Was the '4.5H choke input filter' actually a circuit with the UF5408 diodes rectifying directly in to the choke without any local filter capacitor buffer (ie. a CLC filter arrangement) ?

I could hardly detect a temperature rise on the FETs when pushing out 41W with a 12Vdc input. For your '95C' situation, were you pushing through a lot more power, or operating with a different input voltage, or using the choke output filter or?
  Reply With Quote
Old 17th October 2017, 06:56 PM   #8
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
I was using the DC output of the boost converter (green screws) using the stock HER207 rectifiers, into a 6Z4 tube (both halves in parallel) into the 4.5H choke into 100uf into the load.

The ambient case temperature of the preamp it was inside was over 50c. I also find the choke filter causes the adjustable ones to oscillate. It was powered from an SMPS set to 12.6VDC. It will put out more power and run cooler with a fan obviously but I want a silent supply for audio Nobody wants to hear fan noise, right? Is your module the new revision (there is a diode soldered to the back of the board)? I had issues only with the older version without that diode. I see yours uses different MOSFETs... Mine uses a generic Chinese version of the IRF3205.

Last edited by kodabmx; 17th October 2017 at 06:58 PM.
  Reply With Quote
Old 17th October 2017, 07:47 PM   #9
ErikdeBest is offline ErikdeBest  Switzerland
mostly thinkerer
diyAudio Member
 
Join Date: Mar 2003
Location: Zürich
'150W' 12VDC isolated 25kHz step-up smps for B+
Very interesting info, subscribed!
__________________
my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!
  Reply With Quote
Old 17th October 2017, 08:35 PM   #10
trobbins is offline trobbins  Australia
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Strangely, of the 2 units I purchased, only one had the extra protection diode clamp!

I would certainly recommend never to use a choke input filter with such a smps, and suggest that that would be a key issue with some of your failures/stressed units.

Smps like that should imho aim for the smallest loop rectification and capacitance filtering.
  Reply With Quote

Reply


'150W' 12VDC isolated 25kHz step-up smps for B+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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
12VDC Step up to 300VDC FelixTech Power Supplies 1 21st September 2012 01:21 AM
smps design using 12Vdc to CCS for LED lighting AndrewT Power Supplies 19 7th September 2012 09:03 AM
Isolated voltage feedback for SMPS rtarbell Power Supplies 2 25th July 2007 03:41 AM
SMPS 12VDC to +-45VDC Luciperro Car Audio 11 6th June 2007 12:01 PM


New To Site? Need Help?

All times are GMT. The time now is 05:07 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki