High voltage PSU Mosfet choice

Thread Starter

MarcusFunt

Joined Aug 20, 2022
5
Hi!

I am building a device for a national competition ("Unge forskere") That should be able to sterilize hands with nothing but electricity.

For this project, I need a High-Voltage power supply, capable of delivering 12(or so)kV at 30-100khz.
Therefore my head automatically went to the very popular "ZVS driver" because I want a very efficient operation without much heat as it will be placed in a closed box.
You can look at my current schematic in the attached picture.
I modeled the schematic in lTSPICE and found that 71v spikes occur at startup, and therefore can't use the 60v IRFZ44N I originally wanted to use.
Now the problem is that I don't know what other MOSFET I can use.
I don't care if it is SMD or THT.
I found a few FETs I think will work, but I'm not certain
https://www.mouser.dk/ProductDetail/onsemi/NTP011N15MC?qs=DPoM0jnrROX1k1aAlpufTw=
https://www.mouser.dk/ProductDetail/onsemi-Fairchild/FDP085N10A-F102?qs=0lQeLiL1qyaFktU8QMby%2BQ==
https://www.mouser.dk/ProductDetail/Infineon-IR/IRLR3110ZTRPBF?qs=Z8%2BeY1k3TILcI4snfu078g==

Any help, both with MOSFET choice and flaws in my design are greatly appreciated
 

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Thread Starter

MarcusFunt

Joined Aug 20, 2022
5
My input voltage will be 12vdc from a commercial smps. but the voltage across the MOSFET is dependent on the resonant circuit formed by the primary coil and resonant capacitor. the resonant voltages and current are calculated by LTSPICE: 17A peak. 42vac peak. I will at max be drawing a few milliamps from the transformer.
The MOSFETs will however only pass around 10A max.
The gates will be getting 12v protected by Zener's and flyback diodes(probably not necessary)
the inductance of my primary is going to be around 3-6microheny(very vague I know)
 

LowQCab

Joined Nov 6, 2012
2,506
Aside from the fact that High-Voltage will do nothing to clean Hands ......................
Try an On-Semiconductor FQPF45N15V2,
DigiKey has them in stock.

Differences in Gate-Capacitance "may" cause a Frequency shift,
but You need to be running the Frequency as low as practical in any case,
this will tend towards keeping the Heat-dissipation low.
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Thread Starter

MarcusFunt

Joined Aug 20, 2022
5
Thanks for the replies. The way the high voltage is going to clean hands is via dielectric barrier discharge forming high concentrations of ozone and nitrogen dioxide around the skin. The ozone oxidizes the bacteria rupturing the cell walls and removing viruses' ability to duplicate. The ozone is thereafter quickly sucked into a filtration system. So, your right, high voltage cannot sterilize hands, but ozone can :)
 

LowQCab

Joined Nov 6, 2012
2,506
An Ultra-Violet Florescent-Tube will also work.
It's better to just beef-up your Immune-System with a proper Diet and Vitamins,
rather than worrying about Germs.
On the other hand, You might just make a good income catering to the worriers.
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Thread Starter

MarcusFunt

Joined Aug 20, 2022
5
I agree. A germicidal tube would work as well, it's just a little slower than ozone, an eye hazard and it is very well researched already, thus not as good for a research project:)
Yes, a better diet would resolve a lot of problems right now.

The FET you suggested is probably going to work, but I am a little concerned with the high on-resistance.
I could use the IRFP260NPBF but it has the same problem.
Something with on-resistance below 30mohms probably wouldn't heat up at all, which is important because of the small enclosure I will need to put the supply in
 

shortbus

Joined Sep 30, 2009
9,643

Thread Starter

MarcusFunt

Joined Aug 20, 2022
5
I know that ozone is a pretty nasty chemical. That is also why I am going to put a filtration system, that is going to stop the ozone from getting into people's lungs. I have tried many times to have my hands in high concentration ozone(When toughing sgtc's)
And I have never felt anything. I must be getting a really low dose
 
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