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I am trying to make an high voltage arc generator which is approximately 2 kV output. Here I can easily drive this circuit with 19 volts (laptop battery). Just like in the circuit bellow, I connected negative terminal of BAT1 to negative terminal of 19 V battery. The transformer that I designed is for 300 V input with a turn ratio of 1:7. My first try with a duty cycle of 70% I observed small arcs at the output of transformer. Now I want to try to connect 300 V DC instead of 19 V DC. But I am not sure about connecting negative terminals of BAT1 and 300 V together.

schematic

simulate this circuit – Schematic created using CircuitLab

1) How can I improve this circuit to use it with high voltages such as 300 V DC which is rectified from the mains?

2) If I connect negative of 19 volt and BAT1 separately then mosfet doesn't go off I didn't understand the reason. When connecting to 300 V how should I connect negative terminals? Or should I use earthed cable?

U2 is TLP250.

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1 Answer 1

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Why not use something like a ignition coil transformer, if your goal is higher voltages?

  1. mosfet rated to handle it, and input fuse, I might also suggest deriving your 12V supply from the mains,
  2. You will need to have a common voltage point between the 2 circuits unless you use something like an isolated mosfet driver (they exist for this purpose) Please use a transformer to act as some level of barrier from the wall if you really wish to stay with the mains idea, and use a suitable fuse so it things go badly, the damage is limited

Be aware at some voltage the insulation between the turns of the transformer, and even primary and secondary of the transformer may begin to breakdown,

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  • \$\begingroup\$ Thanks a lot for your answer. Since ignition coils are operating low voltages my output current will be very low if I increase it to 2KV. I want at least 40mA. I didn't understand what do you mean by common voltage point. Once I tried to operate this circuit directly from mains (instead of 19V I used 310 volts rectified) I thought my mosfet which is 500V Vds will handle it. But TLP250 just blowed up. I think the reason is that: I connected 12 volts driver voltage negative terminal with 310V negative terminal. But if I seperate them then mosfet wont go off. \$\endgroup\$
    – Ismail
    Apr 16, 2020 at 13:12
  • \$\begingroup\$ 500V is not actually enough, as you have no protection diode in parellel with the transformer, when you switch it off the voltage may ring to much higher voltages, treat the transformer like an inductive load, its voltage spikes when current flow is stopped. \$\endgroup\$
    – Reroute
    Apr 16, 2020 at 13:16
  • \$\begingroup\$ A common voltage point would be like a circuit ground, just don't confuse it with mains earth, they may not be the same thing, \$\endgroup\$
    – Reroute
    Apr 16, 2020 at 13:16
  • \$\begingroup\$ So If I use a snubber to remove ringing then it shouldn't be a problem to use this circuit? As I understand mosfets source and 12V battery's negative terminal and also high voltage's negative terminal should be connected to a same lets say chassis ground. Is that correct ? Thanks for your efforts. \$\endgroup\$
    – Ismail
    Apr 16, 2020 at 13:28
  • \$\begingroup\$ Not chassis ground, but rectifier negative (not the same thing usually), and while a snubber can help, I would still strongly recommend a diode in parrellel with your primary coil pointing up to deal with anything the snubber misses if you get your values off by a little. \$\endgroup\$
    – Reroute
    Apr 16, 2020 at 13:35

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