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n my application I've to generate HVDC(~700V) for firing of ultrasonic probes to generate RF signal. Here is the circuit diagram i'm using: enter image description here

I'm generating two differential square wave(complemented) which will drive N channel MOSFET (RSS100N03) +5V is generated from battery through (LM1117-5 regulator )

EDITS: Further Details:

Square wave is of frequency ~40-50kHz

U22 is NAND gate SN74LV00

  1. can someone tell me how HVDC is getting generate here, since as far as I know Transformer works on AC only?

  2. What does RSS1000N03 do here?

  3. Is there any other concept/circuit to generate HVDC from low DC?

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  • \$\begingroup\$ Do you really have a capacitor of 4.7kF, or am I failing the sight test? \$\endgroup\$
    – Dmitry Grigoryev
    Commented Sep 22, 2016 at 8:59
  • \$\begingroup\$ it's actually 4.7Kpf.. \$\endgroup\$
    – nkg2743
    Commented Sep 22, 2016 at 9:06
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    \$\begingroup\$ @nkg2743: 4.7Kpf means 4.7 kelvin pico something. "k" for kilo, "K" for kelvin, "p" for pico, "F" for farad. Capitals matter. See SI units. \$\endgroup\$
    – Transistor
    Commented Sep 22, 2016 at 9:49
  • \$\begingroup\$ The square wave IS AC. | What frequency is the square wave. Unless VERY low frequency things need changing. | What part number is U22? | Make R12, R13 VERY low to get max gate drive CURRENT to FETS. - say a few Ohms - maybe 10 Ohms. R14 R15 should not be needed except if U22 is open collector - which it should NOT be. | How did you dimension R25. | How much power do the probes need. Average and peak? | What is spec of TR1 (web link?) turns ratio. How was it chosen? ||There are many ways to make HVDC but what you actually need needs knowing. \$\endgroup\$
    – Russell McMahon ♦
    Commented Sep 22, 2016 at 12:46
  • \$\begingroup\$ @RussellMcMahon can you provide me few links where I can get more insight about the topic \$\endgroup\$
    – nkg2743
    Commented Sep 23, 2016 at 5:30

1 Answer 1

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The high voltage in this system is generated from the high voltage secundary winding of the transformer followed by a voltage double circuit. When the voltage from the transformer goes negative on connection 5 the capacitor C 58 is charged trough D48. When the transformer voltage goes positive on connection 5 the transformer voltage is in series with the capacitor voltage of C 58 and C59 will be charged at a double value trough D47. The RSS 100NO3 are driving the transformer alternating each one half the square wave comming from the input.That is why the incomming square wave is inverted by the as inverter connected nor gates.

There are other possibilities to generate HV. but that you have to find yourself

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  • \$\begingroup\$ what you explained is about after transformer but I'm more interested in what happens before transformer section and that's what question is about. I know arrangement of diode will form doubler/tripler. \$\endgroup\$
    – nkg2743
    Commented Sep 22, 2016 at 9:09
  • \$\begingroup\$ @nkg2743: didn't you already tell in your question that you feed it a square wave? \$\endgroup\$
    – PlasmaHH
    Commented Sep 22, 2016 at 9:17
  • \$\begingroup\$ Since you indicated that the transformer produces AC and your question is about AC to HVDC i explained the doubler. Anyway have added some info about the driving circuit. \$\endgroup\$
    – Decapod
    Commented Sep 22, 2016 at 9:25

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