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I need to build a HV HF power supply to ionize gas. The specifications are 12V input voltage and 10kV output voltage @ 13.56MHz. I know this is not an easy task at all, since in this frequency area, all the paracitic capacitors and inductors have to be taken into account.

What I have tried to simulate yet is:

1.) Slayer Exciter: The problem here is, that the resonance frequency mostly depends on the parasitic capacitors and I don't reach such an output frequency at all if I want to use electrodes with a capacitance of some nF.

enter image description here

2.) Royer Converter:I tried to simulate the behaviour of a Royer Converter, but also with an output capacitance of a few pF, the frequency comes not in the needed range.

enter image description here

3.) Flyback Transformer: Most people use flyback transformers to generate high voltage for ionizing gas, but I think this would not work at all at this frequency, since the transformer is saturated.

Has anyone an Idea how this could be done, or is it impossible from 12V? If it's nearly impossible, has anyone a suggestions what could be done to generate this 10kV at a high frequency as possible.

Edit: I simulated now the class-E amplifier circuit and the switching behaviour works fine. The problem is, that I cannot put the input voltage too high to achieve a high output voltage, especially also because of the MOSFET. How could I go from here to increase the voltage to 10kV AC? Tesla magnifier? Another problem is the huge input power of around 1kW.

enter image description here

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    \$\begingroup\$ That is a hell of a slew rate, an IOT might be the right choice, what is the actual power level you need? \$\endgroup\$ – PlasmaHH Jul 2 '18 at 14:28
  • \$\begingroup\$ I need only around 10W of power. The slew rate really seems to kill this build. \$\endgroup\$ – HansPeterLoft Jul 2 '18 at 14:30
  • \$\begingroup\$ What about using DC switching power supply ICs? Do you have to use 13.56 MHz only? \$\endgroup\$ – Uwe Jul 2 '18 at 14:33
  • \$\begingroup\$ That sounds like a good idea, the frequency is constant at 13.56MHz. \$\endgroup\$ – HansPeterLoft Jul 2 '18 at 14:42
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    \$\begingroup\$ You will likely have to go with a resonant circuit (if this is possible at all). I get 600mA RMS current into 10nF at 10kV. That would be rather a high current at 12V with a simple transformer. What is the expected power output requirement? 10W seems very low. \$\endgroup\$ – Spehro Pefhany Jul 2 '18 at 14:49
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This task needs to be broken down into several more easily manageable chunks. Presumably the choice of 13.56MHz is to hit the ISM band. This only runs from 13.553 to 13.567, so you have very little tuning range available. This means you really need an amplifier driven by that frequency, and tune the load, rather than use an oscillator like a Slayer or Royer that adapts to the load's tuning.

'To ionise gas'. The ioniser construction will dictate the capacitance you have to drive. You need to obtain or build that first, and then work backwards. Ionised gas is conductive, un-ionised gas is insulating. This means the start-up and the running load will be very different. It may be that you can tolerate different conditions at the ioniser, perhaps a higher voltage to start, and a lower voltage when running?

10W (the power you say you need in comments) is fairly straightforward at 13MHz, if approached as a transmitter into a 50 ohm load.

If I had to get from 10W/50ohms to 10kV, I'd probably do it in two steps. The first step would be a straightforward transformer, to step up to some intermediate voltage. A well-coupled transformer to 10kV would be very difficult to build without the self-resonance frequency (SRF) falling well below where you wanted to operate it.

The second step would be a series inductor, Tesla magnifier style, into your load capacitance. At resonance this would magnify the voltage up to a maximum of Q times its driving voltage. This inductor would be long and single layer, and could be designed with a high SRF.

You still have the problem of tuning the magnifier.

The amplifier either needs to be protected from reverse power when it's presented with an unmatched load, or be beefy enough to shrug off reverse power. Look at minicircuits, they have a nice parametric search for amplifiers. There's a 100k to 200M one with 45W output power, safe into open and short, which would make a good lab experimental power source, but it's not cheap.

Bonus Edit A comment from Dan Mills about a 1/4 wave feedline reminded me that reality is what it is, even if our descriptions change. We can make a synthetic transmission line from a CLC section. If you run a 1/4 wave line open circuit, then you get voltage magnification at the open end. If you take the Tesla magnifier L and load C, and compute what they mean in terms of a synthetic transmission line, you'll notice they are 1/4 wave at resonance. Take the impedance, the sqrt(L/C), and that's the ratio by which feedpoint current becomes the open load voltage, just as for a real 1/4 wave transmission line. Two descriptions, one reality.

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    \$\begingroup\$ All good advice: Such a narrow band likely requires a crystal oscillator signal source at 13.56 MHz....followed by an amplifier. For 10W a hand-adjusted LC tuner would be OK (higher power units often have auto-tuners for this service). The amplifier must be robust to handle all kinds of load impedance without smoking. \$\endgroup\$ – glen_geek Jul 2 '18 at 15:57
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    \$\begingroup\$ IIRC at least one of the power fet vendors (IXYS) has an app note for 13.56MHz power. Plasma breakdown dynamics are 'FUN' in terms of what it does to the load reflections, take a hint from the RF laser guys, a 1/4 wave feedline and current limited supply to the finals is the way to fly, that way an open circuit at the plasma turns into a low Z at the driver and you get lots of volts for ignition. You will still find that the apparent load impedance depends on the power which can give rise to instability. \$\endgroup\$ – Dan Mills Jul 2 '18 at 16:47
  • \$\begingroup\$ Thank you guys for your detailed descriptions of how this could be achieved. In the Appnote from IXYS (ixys.com/Documents/AppNotes/CO1.pdf) is described how to design this Class-E Amplifier, so i will give this design a try, but I need to increase the Q-Factor (seems to be pretty difficult) and also the input DC voltage should be in the kV range. \$\endgroup\$ – HansPeterLoft Jul 3 '18 at 16:14
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High don’t know if I can help but I have a 28 kv trNsformer Pushing 13.5 mghz for an old triumph lazer seems to use about 11000 Watts first a large berillium valve is heated with 5 volts 130 amps then small frequency drivers drive the valve they run at 20 volts rectified from 3 phase 380 to ocillator plates and then a large 3 phase coolant pump drives the Lazer tubes helium carbon dioxide mix excited and I t fires The whole circuit is water cooled lots of backfeed to Mach the copasatance field operate if u want more info lancelot.good1@gmail.com for hands Peter loft

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    \$\begingroup\$ Welcome to EE.SE, lance, but this is almost unreadable due to poor spelling, incorrect capitalisation and lack of punctuation. Can you clean it up? See Write to the best of your ability in the site's rules / help pages. If English is not your first language then please say so in your user profile so we can make allowances for grammar and spelling (but not punctuation!). \$\endgroup\$ – Transistor Jan 12 at 0:52

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