High- Voltage Adjustable Regulator

[alfa88]

I'm looking to build a bench power supply to do some vacuum tube(valve) experiments and was wondering if anyone knows of a solid state solution for a adjustable voltage regulator that could withstand 350Vdc input, output 300Vdc @~ 300ma. I got to about the 6th page on Google and start seeing the same results come up.

 

[OLIVE2222]

Hi Alfa88,

Here under 2 solid stats high-voltage power supplies. The pages are in french but they are on the first page of the Google query result

The schematic is straightforward, the voltage can be changed by changing a R value

http://www.dissident-audio.com/RegulHT/Regul.html

This is a more complex lab power supply (50 à 450 V / 500 mA) based on an article published in LED magazine ("field proven" so)

http://www.novotone.be/index.php?option=com_content&task=view&id=32&Itemid=34
http://www.novotone.be/_site/projets/Projet05/Fig05.pdf
http://www.novotone.be/_site/projets/Projet05/Fig04.pdf

cheers,
Olivier

 

[davenn]

ohhh those ccts are neat

thanks for the links

Dave

 

[alfa88]

Nice,nice, nice. Looks like I have a new project. Thanks.

 

[alfa88]

Transformer Options

I've been exploring circuit options but step 1 seems to be finding a transformer. I've seen a suggestion on finding and scrapping old 'boat anchor' oscilloscopes but it occurs to me that I could simply get step-down transformers and reverse them. An example would be 120 Volt to 28 Volt @ 3 Amp transformer to supply 514 Volts @ 700mA .

 

[Resqueline]

No you can't do that to that extreme, due to the core saturation (& overheating) that would occur. There will be only a small overvoltage allowance (10-20%).
There will be differences between brands how much you can overvolt them. Using a 50Hz transformer on 60Hz mains would always allow you to overvolt it by 20% safely.
Using two european transformers in reverse (230/240V primaries in series) would easily reach the goal.

 

[alfa88]

It's a good thing I asked. So are you saying get a couple Euro. 1:2 transformers, parallel the '2' windings as input and connect the '1' windings in series as output?

 

[OLIVE2222]

Hi, yes having two 1:2 will be OK but the rectified voltage will be quite high:
(2X230)X1.41=~650 Volts, the 1:1 + 1:2 combination should better match (110+230)X1.41 ~480 Volts.

Olivier

 

[Proschuno]

On the subject of reversing step-down transformers, I have a transformer from a radio power supply that I am attempting to do almost the exact same thing with, to power tubes; it can handle probably about 20 amps on its secondary which is stepped down to various windings of 40, 20, and 4 volts.

Given an awesome current rating and lots of magnetization, could I use this as a step up using the 20 volt windings to make 720 volts?

 

[duke37]

You cannot get much more voltage out of a winding than it was designrd for. The core will go into saturation.

Putting the secondaries of two transformers in series may work but you are relying on the insulation in the transformer being adequate. I would not do it.

Running a transformer in reverse will give a somewhat low voltage out since the transformer in normal operation has a high voltage out to compensate for voltage drop when under load.

A voltage doubler (or tripler) can be used to obtain higher voltages.