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I am looking to build a Pulse Transformer Switch Mode Power Supply.
Input - Volts: 120V AC | Current: 15A | Total Power 1800 Watts
Output: Variable Voltage: 0 V - 1 MV DC as well as offsetting the pulses over any dc voltage level from 0 V to 1 MV Variable Frequency: 1 Hz - 1 MHz or higher Variable Duty Cycle: 0 - 100% Variable Waveform: Sine, Triangular, Sawtooth, and Square waves
I decided on using a PIC with a crystal to control the frequency and duty cycle. Using USB I should be able to control the PIC from a PC as well as get data from the PIC and save it on the PC.
I am unclear how I can vary the voltage output or offset the voltage pulses as was done with the HVPS-PRO I linked to. I also do not know how I can vary waveforms.
So my first stumbling block I think is how do I change the wall voltage to DC while creating Sine, Triangular, Sawtooth, and Square (Smooth) waves which then get switched on an off by the MOSFET when triggered by the PIC chip?
My second stumbling block is raising the voltage high enough. In that HVPS-PRO article it shows the designer using a flyback transformer from a CRT. I have read in other places that a flyback transformer cannot take in much power (the HVPS-PRO uses batteries). Is a flyback transformer no good for the first voltage raising primary/secondary coil combo? If not, what are my other options? A spark plug coil?
I figured I would use copper tubing and an air coil (like a tesla coil) for the second voltage raising primary/secondary coil combo.
Thirdly how can I control the voltage amplitude and offset voltage (preferrably also from the PC)?
Registered Member #1911
Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165
Robert Francis wrote ...
I am looking to build a Pulse Transformer Switch Mode Power Supply.
Input - Volts: 120V AC | Current: 15A | Total Power 1800 Watts
Output: Variable Voltage: 0 V - 1 MV DC as well as offsetting the pulses over any dc voltage level from 0 V to 1 MV
Without some kind of multiplier or a transformer of an incredible size (when compared to an NST) you will not be able to achieve a 1MV discharge. I recommend that you bring down your expectations, or expect to pay around $5,000 in order to have this apparatus built on this ground alone.
Well, here, we have the problem that as you go higher and higher in frequency, the more skin effect begins to be apparent. When you get to 1MHz, skin effect is so great that you would (almost) never be able to insulate 1MV. Also...variable waveforms? If you use something like a flyback (LOPT) transformer you will need to drive it at a high frequency because of the core material; the flyback transformer will need to be driven around 20KHz and would, thus, limit frequency output to <1KHz for any reasonably clean waveform. Duty cycle? Meh, it can be done. Sine, Triangle, Sawtooth and Square waves? Methinks not, for the same reason that is mentioned earlier in this post.
Robert Francis wrote ...
I am unclear how I can vary the voltage output or offset the voltage pulses as was done with the HVPS-PRO I linked to. I also do not know how I can vary waveforms.
You cannot with any efficiency.
Robert Francis wrote ...
So my first stumbling block I think is how do I change the wall voltage to DC while creating Sine, Triangular, Sawtooth, and Square (Smooth) waves which then get switched on an off by the MOSFET when triggered by the PIC chip?
It's not gonna' work, my friend. High voltage transients are not your friend; I am.
Robert Francis wrote ...
My second stumbling block is raising the voltage high enough. In that HVPS-PRO article it shows the designer using a flyback transformer from a CRT. I have read in other places that a flyback transformer cannot take in much power (the HVPS-PRO uses batteries). Is a flyback transformer no good for the first voltage raising primary/secondary coil combo? If not, what are my other options? A spark plug coil?
The highest voltage transformer available at any reasonable size/cost/voltage is an X-ray transformer which has an output of, usually, 1KV (at 60Hz). The output could then be modulated via mechanical switches to a certain frequency after the step-up transformer, however the contacts would not take too kindly to this.
Robert Francis wrote ...
I figured I would use copper tubing and an air coil (like a tesla coil) for the second voltage raising primary/secondary coil combo.
Thirdly how can I control the voltage amplitude and offset voltage (preferrably also from the PC)?
Well, if you're using an air-core transformer, you will need ridiculously high frequencies (KHz), naturally, and you will need to expect an efficiency of well less than 5%. You could control the output voltage via a mechanical tap on a transformer that is similar to a variac (an autotransformer).
Robert Francis wrote ...
Suggestions? Recommendations?
Don't expect to be able to build this yourself without years of experience, and don't expect to be able to build it without around $500K.
I imagine that you were hoping to build this as a 'play-thing' and not for any sort of realistic experiment. I apologize if you find that rude, however I have met more people with little experience whom want no more than to make pretty sparks and arcs.
Well, here, we have the problem that as you go higher and higher in frequency, the more skin effect begins to be apparent. When you get to 1MHz, skin effect is so great that you would (almost) never be able to insulate 1MV. Also...variable waveforms? If you use something like a flyback (LOPT) transformer you will need to drive it at a high frequency because of the core material; the flyback transformer will need to be driven around 20KHz and would, thus, limit frequency output to <1KHz for any reasonably clean waveform. Duty cycle? Meh, it can be done. Sine, Triangle, Sawtooth and Square waves? Methinks not, for the same reason that is mentioned earlier in this post.
It would be like a giant 1.8kW transmitter with an excessively high voltage. It would also generate a large flame/steamers because of the air breaking down.
Plasma Lover wrote ...
Robert Francis wrote ...
My second stumbling block is raising the voltage high enough. In that HVPS-PRO article it shows the designer using a flyback transformer from a CRT. I have read in other places that a flyback transformer cannot take in much power (the HVPS-PRO uses batteries). Is a flyback transformer no good for the first voltage raising primary/secondary coil combo? If not, what are my other options? A spark plug coil?
The highest voltage transformer available at any reasonable size/cost/voltage is an X-ray transformer which has an output of, usually, 1KV (at 60Hz). The output could then be modulated via mechanical switches to a certain frequency after the step-up transformer, however the contacts would not take too kindly to this.
From what I remember, x-ray transformers around around the 75-100kV range and must be submerged in oil to prevent internal arc overs because of air bubbles.
Plasma Lover wrote ...
Robert Francis wrote ...
I figured I would use copper tubing and an air coil (like a tesla coil) for the second voltage raising primary/secondary coil combo.
Thirdly how can I control the voltage amplitude and offset voltage (preferrably also from the PC)?
Well, if you're using an air-core transformer, you will need ridiculously high frequencies (KHz), naturally, and you will need to expect an efficiency of well less than 5%. You could control the output voltage via a mechanical tap on a transformer that is similar to a variac (an autotransformer).
There is no single device that can amplify that large of a frequency range. Where did you get the number 5%? And no, you don't need something in the kHz range. You would probably want something in the 100s of kHz to MHz range to get a reasonable amount of power coupled to the secondary.
Plasma Lover wrote ...
Robert Francis wrote ...
Suggestions? Recommendations?
Don't expect to be able to build this yourself without years of experience, and don't expect to be able to build it without around $500K.
I imagine that you were hoping to build this as a 'play-thing' and not for any sort of realistic experiment. I apologize if you find that rude, however I have met more people with little experience whom want no more than to make pretty sparks and arcs.
You would need a very complicated driver circuit (more complicated than anyone here could design I assume). See this thread for a similar topic
You would need a very complicated driver circuit (more complicated than anyone here could design I assume). See this thread for a similar topic
Ok, point conceded.
This power supply is actually going to be used for a research experiment and not for spark visuals. I am going to test the anomalies seen in the anomalies section of the Robert Talley report titled Twenty First Century Propulsion Concept (page 83). In it a slight force was recorded in vacuum at 19 kV and 600 Hz pulsed DC (I assume square wave 50% duty cycle). I wanted to test all possible combinations of voltage pulse amplitude, offset voltage with voltage pulse, frequency, and duty cycle, recording each parameter through the PIC to the PC as well as use a scale with a USB port to record weight at the time as well. Basically to see if any combos turned up anything.
What sorts of ranges and accompanying transformers would be more manageable? I could build multiple power supplies instead of just the one "universal" one. I would like to cover the ranges I listed in my first post even if it means I have to build many power supplies. I want to be as thorough as possible in this experiment.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
building multiple supplies could work, as then you can have appropriate drivers and transformers for each, but aware of limitations - such as "mix and matching" waveforms and the like... many have tried to build a truly universal HV Supply, and many have gotten noting out of it... including myself, even with a much simpler one than you describe, making an HV supply multi-purpose is challenging to say the least
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Dear Robert, After few years of experimenting with HV I can ensure you that your aims are not real. 1MV is very difficult to get even with well designed multiplier. 1MV in 1MHz sounds more like some crazy military project. You should reconsider your needs, you can get 1MV but rather DC, or pulsed but in 10’s Hz range. You can get 1MHz but maximum in KV. These are reasonable but still pretty tough projects the guys here can help. In other words go back to the ground...
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Eek! JL Naudin connection detected! Keep it testable, folks.
The goals you set out in your first post are very ambitious indeed. The basic way to achieve them would be to make a high voltage amplifier, that makes a high-voltage replica of a reference voltage fed into it. For instance, if it produces 10kV for every volt of reference voltage, then if you feed in a triangle wave oscillating between 1V and 4V, you'll get out a triangle wave oscillating between 10kV and 40kV.
The amplifier could be linear with vacuum tubes (maybe those HV regulator triodes from old tube TV sets?) or it could be switched-mode: a PWM controller such as the TL494 driving a TV flyback, with negative feedback from the output voltage. Which is almost certainly how "Xavier Borg"'s device works. If it works at all: I notice he hasn't posted traces of the actual output voltage.
If you set your sights a little lower than 1MV, you could probably make this work. A Tesla coil as the second stage probably wouldn't work, because of the difficulty of rectifying the output: you said you wanted DC.
As for PC control: In the past I've built instruments that used the FT232 chip to convert USB to RS232, then fed the RS232 through optoisolators to a PIC inside the instrument that did the controlling. These days, you should investigate IrDA and Bluetooth too.
A Tesla coil as the second stage probably wouldn't work, because of the difficulty of rectifying the output: you said you wanted DC.
I was under the impression that air core transformers can't increase/decrease constant DC voltage because the magnetic field does not change but that it can increase/decrease pulsed DC voltage or AC voltage because the magnetic field does change. Are you sure pulsed DC gets turned into AC by a transformer? If so, how does a pulse transformer work?
The basic way to achieve them would be to make a high voltage amplifier, that makes a high-voltage replica of a reference voltage fed into it. For instance, if it produces 10kV for every volt of reference voltage, then if you feed in a triangle wave oscillating between 1V and 4V, you'll get out a triangle wave oscillating between 10kV and 40kV.
Looks like I have a lot of reading to do this weekend, I hadn't heard of voltage amplifiers until now. I know the Exar XR2206 chip can output a variety of waveforms so if I could build a linear amplifier that amplifies the output of that chip, that would work to get me the different waveforms.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Yes, let's not hear any discussion of what this power supply is to be used for! If this thread wanders off into electrogravitics, it will be locked. It's just a power supply folks, put those UFO dossiers down.
Transformers only work on AC. This is high school physics stuff.
Pulsed DC can be thought of as a steady DC current plus a series of AC components: the proof of this is by Fourier analysis. Only the AC components pass through the transformer, the DC component is blocked. This is true for air-cored Tesla transformers as well as magnetic cored ones.
So, if you want DC out of a transformer, you must restore the DC component by using a rectifier of some sort on the output. Most TV flybacks have a high voltage diode built in, so it's already done for you.
Pulse transformers can work without a rectifier, if they're driving a non-linear load that can do the rectifying itself. For instance, a radar magnetron or X-ray tube is basically a diode, and won't conduct in the "wrong" direction.
And yes, that trick with the XR2206 chip is exactly what I meant.
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In Need of a Little Help in Designing a Versatile High Voltage Power Supply
