Hi guys ,

I'm developing an application for a university project
which requires high frequency AC power supply.

The frequencies are in the 10khz - 500khz range,
the voltages are 100-200v and the currents running
are below 1ma.

It seems to me like a challenging range of parameters (the freq. range can be narrowed down a bit : 100khz-300khz).

I remembered that the newer neon transformers use switching power supplies,
so i am wondering what would happen if instead of feeding a neon psu from 110ac, i will give it half the power, will the output be more or less proportional ?
And what about the frequency - some spec sheets mention that the frequency and the output V is variable, depending on the load (the neon itself).


I would appreciate any advice the seniors might have.

Also : on a related topic. I once made the mistake of asking in the forum how to generate a high voltage AC signal from a battery. The thread was closed and i realized that my question must have been really stupid. It might be totally my fault, but i never was able to figure out the fundamental issue with that configuration.... If power in < power out, what is the root reason for this problem being difficult ?

Thanks for all the advice !
Lenny

 

Hi guys ,

I'm developing an application for a university project
which requires high frequency AC power supply.

The frequencies are in the 10khz - 500khz range,
the voltages are 100-200v and the currents running
are below 1ma.

It seems to me like a challenging range of parameters (the freq. range can be narrowed down a bit : 100khz-300khz).

I remembered that the newer neon transformers use switching power supplies,
so i am wondering what would happen if instead of feeding a neon psu from 110ac, i will give it half the power, will the output be more or less proportional ?
And what about the frequency - some spec sheets mention that the frequency and the output V is variable, depending on the load (the neon itself).

Lenny

I did a search on the net about fluorescence ballast. I found that many accept an input voltage between 110 V and 277 V at 50/60 Hz. There was only one place that mentioned the voltage output to start the lamp was 500 V or 600 V (it depended on the lamp).
I don't think providing half the voltage will work since you need to high output voltage to start the lamp (to ionize the gas in the tube). Once the gas has been ionized and the current flowing, it doesn't require as high a voltage, so I believe the voltage drops down.

Added: Some of the ballast operate between 42 kHz and 54 kHz.

 

First, any claim that power out is greater than power in is called perpetual motion and therefore banned on this site, or any site that isn't full of crack pots. If you don't know the difference between power and voltage, get yourself studying.

Second, all (AFIK) gas discharge tubes require a fairly high voltage to start the arc, then use an inductor to limit the current. The characteristic of the inductor is that it will increase its output voltage hugely until it can discharge the energy that has been pumped into it. That is how the circuit keeps current flowing after the first ionization arc. If you increase the frequency from 50 Hz to 60 Hz, the necessary inductor become smaller. If you increase the frequency from 60Hz to 20,000 Hz, the necessary inductor becomes a lot smaller.

That's a start at explaining gas discharge tubes. This includes mercury vapor, high pressure sodium, neon signs, fluorescent tubes, helium-neon lasers, and a few others.

 

#12 , Thanks, I made a mistake on the sign: it was supposed to be the other way around: power in > power out, just to show that the basic energy conservation still holds.


I have found this transformer:
http://www.amazing1.com/products/mi...requency-transformer-7kv-10ma-20k-100khz.html

which specifies a range of operating frequencies. The website mentions that this transformer may be used in self oscillating circuitry where the feedback winding is utilized, or in a conventional timer controlled inverter circuit. Operates with 9-14 vdc input.

I would like to understand how is such a transformer typically used.
My previous experience with transformers had them specified by a ratio of resistances, or voltages, but it seems to be different here, as this type of info is not being specified.

My question is this : could someone point me to a tutorial-type text or a simple circuit that i could run in spice and gain some insight how this transformer might be used ?
that, or any other advice that would lead to furthering my education on this would be very much appreciated !!

Thanks
Lenny

 

That transformer is fairly well specified. It says 7KV at 10 ma and the input will work with 12 volts. Therefore, it must be providing 70 watts at the output and the input must be more than 70 watts. 70W/12V = 5.8333 amps. Presto. You have a crude estimate of how to make the driver circuit. Choose a frequency between 20,000 Hz and 100,000 Hz and build an oscillator that can pass about 6 amps of current at that speed. Schematics provided with your purchase of 3 or more transformers.

I don't "sim" so somebody else will have to point out that part.