Help with HV adjustable power supplies for radiation detectors.

[Richard Hull]

I have found these little high frequency transformers very handy for supplies up to 2kv. They can supply a decent amount of current of 1ma if driven hard. Most really large screen TV's that have twenty or more CCFL tubes used 4 or more of these on their driver boards. Such boards feed these with 24-48 volts DC. Yes, they are current hogs, but do supply decent current out of up to several mA needed to light the long tubes. Each transformer might supply 5 or more long tubes in banks. I have collected about 100 various types of these from scrapped flat screens. I originally hoped to use them as bias supplies for GM, PM and neutron detectors, but you have too many varieties in such a pile that each one or set of 4 would require to hand trim each group of supplies to spec. For one offs, they are great, however.

They can be made portable for battery power if under driven and only a few microamps are needed. I find the trend was to use 4-6 small transformers on the driver boards on big screens, but now they tend to use only two much larger, weighty transformers to reduce the component count. Battery, portable operation would tend to make these larger ones problematic, but mains operation could see these used for rather stiff high frequency, high voltage supplies.

Richard Hull

[Sarmad suseyn]

Hi .
Isn't easier to buy one?
Like this one it tried it works just fine
https://a.aliexpress.com/_dXvy7er
Good luck

[Richard Hull]

The board says 200 volts. Is that enough? Can you blast in more than the stated 5 volts to get more voltage. If so, what is the current drain from the low voltage supply. Will the pot on the board allow for more than 200 volt adjustment. Not many nuclear detectors will work at 200 volts. what is your detector? Ion chambers can work as low as 150 volts.

Richard Hull

[Sarmad suseyn]

Dear Richard Hull
No its not 200v !
On 5 volts maximum you will get 700v
But on 9 v you will get 1000v
There is a soldiering points fixed voltage 200v, 50v , 170v
The green terminal is the main out voltage
And you can adjust the voltage with the variable resistor
Have a good day

[Sarmad suseyn]

And the easiest way to find a high voltage Module is from
Rechargeable Electric Mosquito Zapper it gives 2000 volts
And some adjusting with variable resistor you can use it
Its called the poor mans Hv you can get it for 10$

[Cai Arcos]

Hi:

I was aware of the mosquitoe killing HV source. It is a "Joule Thief" like the one I previously discussed (i.e a blocking oscillator) with added voltage multiplication at the output. Thus, it's noise makes it unsuitable to my needs.
What is the noise in the commercial module you described before?
EDIT: It seems like the different voltages are taking out at different stages of the output multiplier. Can it sustain the current claimed at the latter stages of multiplication?

[John Futter]

Cai
most of these can do up to 10 watts of output some a little more
from that you can work it out

[Cai Arcos]

John:

That seems way too high. Taking the output directly the output at the transformer (thus avoiding any losses in the multiplier) we get a power 1.5 W (the 75V claimed times the *optimistic* 20mA). At 400V that is around 4 mA, which is respectable.
Still, the noise is what worries me the most... It also seems like there is no feedback. The circuit is just a 555 square wave generator and a N-Channel MOSFET! A quick homemade blocking oscillator is cheaper, doesn't have shipping time and should be stiffer. Furthermore, by using a small capacitor between between base and colector (multiplied by Miller Effect) one compromises on the rise time (and thus output voltage) but can significantly reduce noise.

[John Futter]

Cai
Both Doug Coulter and myself have used similar bought from Mouser and I got 15 watts max out of mine they are meant to run one or two 5-8 watt flouro tubes as used in laptop LCDs

[Cai Arcos]

John:

I think we are talking about different things. You probably reference something like this: https://www.mouser.es/ProductDetail/JKL ... qjc3YDs%3D. Which I have read about in Doug post "Standard HV Supply for detectors". I was talking about the cheapo module referenced above from Aliexpress.