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MOSFET Headache

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Here's the schematic, and approximately what the waveform should look like. Is this the way you have it hooked up?
 

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Try changing the 10k resistor to 100k The peak voltage will drop, but the ringing should be apparent.
 
These pics are with a 100kohm resistor between pin 3 and the secondary. The first one is at 10usec/div, second is at 20usec/div and third is at 100usec/div.

BTW, what time zone are you in, Roff?
 

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turbobill said:
These pics are with a 100kohm resistor between pin 3 and the secondary. The first one is at 10usec/div, second is at 20usec/div and third is at 100usec/div.
Finally we get some useful results. As you can see, the period of the ringing is about 8 usec, which means your resonant frequency is about 125kHz. With 1000 turns of wire, I doubt that the probe capacitance is adding more than 10% to the stray capacitance of the coil, i.e., the actual resonance without the probe is still probably close to 125kHz. There is no way I can think of that you can drive this at 2MHz and get anything significant out of it. The secondary is a bandpass filter. I think your transformer is a dead horse, at least at the frequency you have in mind. You might want to divulge what you are trying to accomplish in more detail. Maybe I or someone else can come up with an alternate solution.
BTW, what time zone are you in, Roff?
I'm on Mountain Daylight time (Idaho). Where are you?
 
Roff said:
the actual resonance without the probe is still probably close to 125kHz. There is no way I can think of that you can drive this at 2MHz and get anything significant out of it. The secondary is a bandpass filter. I think your transformer is a dead horse, at least at the frequency you have in mind. You might want to divulge what you are trying to accomplish in more detail. Maybe I or someone else can come up with an alternate solution.

I just need to get 3kv from a 12v battery. I don't have to drive it at any certain frequency. As long as it will do the job, I don't care what I have to drive it at. The primary should run at a pretty hefty current, hence the #4 wire.

So would you suggest a certain frequency? Someone suggested it needed to be very short to keep from exploding the battery. Sounds reasonable to me.

I'm on Mountain Daylight time (Idaho). Where are you?

I'm in eastern time zone, Florida.
 
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Hey, y'all.
I was born in Florida, back when everyone there had a southern accent (OK, so many of them still do, technically, since Cuba, Colombia, etc., are farther south than Florida).:rolleyes:
How much current do you need at 3kV?
 
turbobill said:
We'd like to get around .4A, but as close as possible or practicle will work for now.
:eek:
That's 1.2 kilowatts! If you could get 100% efficiency, that would require 100 amps from your battery. You would be extremely lucky to get 70% efficiency. How many batteries do you plan to have in parallel?
BTW, I'm assuming you want 3kV DC, not pulsed.
 
Do you mean 0.4A at 3kDC or do you mean that the supply shall have a short circuit current of 0.4A?
 
Roff said:
:eek:
That's 1.2 kilowatts! If you could get 100% efficiency, that would require 100 amps from your battery. You would be extremely lucky to get 70% efficiency. How many batteries do you plan to have in parallel?
BTW, I'm assuming you want 3kV DC, not pulsed.

Yes, 3kV DC, not pulsed. Or you could say 1200 Watts, or 12 one hundred watt light bulbs. It's really not that much if you look at it from an electricity point of view, but it is if you look at it from an electronics p.o.v..

Hero999 said:
Do you mean 0.4A at 3kDC or do you mean that the supply shall have a short circuit current of 0.4A?

I mean 0.4A at 3kV DC.
 
turbobill said:
Yes, 3kV DC, not pulsed. Or you could say 1200 Watts, or 12 one hundred watt light bulbs. It's really not that much if you look at it from an electricity point of view, but it is if you look at it from an electronics p.o.v..



I mean 0.4A at 3kV DC.
It's a lot of power if you look at it from a 12V battery standpoint. What are you charging the battery with? How long do you expect the battery to last?
 
Roff said:
What are you charging the battery with?

It would not be prudent to tell you that. Let's just assume that charging the battery is not a problem and I need to get the 3kv from it. And let's not be too concerned about how much amperage for the time being.

How can I get the most out of the current system( battery, MOSFET pulser and the current air core transformer ) without blowing it up?

I really do appreciate you guy's help. I'm a total amateur and I know that this is somewhat unorthodox but I really need to do this somehow.
 
I don't know how to do it. There are probably consultants who can design this for you. If I knew how to do this, I probably wouldn't do it for free. Maybe one of the other guys here can help you.
 
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