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0-300V DC signal generator

Discussion in 'Electronic Design' started by Marco Trapanese, May 3, 2013.

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  1. Hi,

    which circuit would you recommend to generate a DC voltage between 0 and
    300V? I have a 24V as input. The output current is quite negligible:
    less than 1 mA @ 300V.

    I'm afraid about the high output/input ratio change.

    Marco
     
  2. Push-pull driving transformer -> voltage doubler with about an 8:1
    xfmr turns ratio (CT primary and secondary)?
     
  3. Joerg

    Joerg Guest

    In one word: SEPIC. You can use pretty much any boost converter chip for
    that.

    That is only really a concern for high power situation. 300mW doesn't
    quite qualify as high power :)
     
  4. amdx

    amdx Guest

    You say you have 24V, Everyone assumed DC.

    Do you have 120vac available?

    Variac-- 120 to 240 volt isolation transformer--Full wave bridge--filter
    caps-- large value load resistor. Good for 0 to 330 volts
    I've seen small variacs that would be great for this.
    Mikek
     
  5. Jeroen

    Jeroen Guest

    A *what*???

    Ah, Cockcroft-Walton, I suppose.

    Jeroen Belleman
     
  6. Tim Williams

    Tim Williams Guest

    One of many circuits that'll do;
    http://www.seventransistorlabs.com/Images/High_Voltage_Generator2.png
    (Note the little feedback winding is on the same core)

    I'm also fond of boost-flyback circuits like this one,
    http://www.seventransistorlabs.com/Images/Deadbug_Sch.png

    And numerous chip based solutions (interal or external switch).

    Both of these are wound for about half the voltage, obviously you'd double
    the turns ratio and feedback resistors to get there. No problems with
    parasitic capacitance, at least at this level.

    For off-the-shelf-ness, you could try shanking a camera photoflash
    circuit. The current may be lower, and the supply voltage too low,
    however. And you'd have to add your own regulation.

    Tim
     
  7. Robert Baer

    Robert Baer Guest

    I am not a fan of CFL inverters used this way; the design is to
    produce high voltage at very little current voltage for "first strike"
    to produce ions), and then produce current at low voltages (typically
    ionization potential of Hg = = 32V).
    I seriously doubt that any "reasonable" current can be maintained at
    300V using a CFL inverter - even a "high power" ne made to drive camper
    lights.
     
  8. Il 03/05/2013 20:26, Jim Thompson ha scritto:

    I haven't yet such a details but I think 7-8 bit should be enough with a
    ripple less than a LSB.


    I'll looking for some app notes.
    Thanks
    Marco
     
  9. Il 03/05/2013 20:37, Tim Wescott ha scritto:

    I said "signal generator" because the output current is very small, so
    in my mind it's not a "power supply".


    The power rail. The output voltage is set by a microcontroller.


    So what the difference between a 0-300V power supply derived from 24V
    and a 0-300V DC generator derived from a 24V? I ask this to use the
    right terms.

    Thanks
    Marco
     
  10. Il 03/05/2013 22:30, amdx ha scritto:

    Nope.
    Marco
     
  11. Il 03/05/2013 23:21, Vladimir Vassilevsky ha scritto:

    I knew it as voltage multiplier (composed of a cascaded half-wave doubles).

    I will do some simulation to understand how it works with such a large
    span of voltages.

    Of course avoiding magnetics is a great thing ;)

    Marco
     
  12. Phil Allison

    Phil Allison Guest

    "Marco Trapanese"

    ** Absurd logic.

    WTF constitutes a " signal" in your book ?

    ** The term "power supply" describes the purpose.

    Using a "DC generator" is one way to achieve it.

    BTW:

    You need to say if the 300V supply needs to have ( galvanic) isolation from
    the 24V one.

    Makes a big difference to the topology.



    ..... Phil
     
  13. Il 04/05/2013 09:03, Phil Allison ha scritto:

    A voltage (or current) with negligible power. It is used to control
    something rather than power something. Am I wrong?


    The galvanic isolation is welcome but not mandatory. Of course there
    must be protection against over-current and short-circuits.

    Thanks
    Marco
     
  14. Phil Allison

    Phil Allison Guest

    "Marco Trapanese"
    ** A "signal" contains information.

    It is wrong to use the term for things that do not.

    ** How ambiguous.

    Wot a code scribbler.


    .... Phil
     
  15. Il 04/05/2013 09:31, Phil Allison ha scritto:

    Well, that voltage *does* contain information! It's the output variable
    of the system.

    Marco
     
  16. The little backlight lamps I have used run at a couple of hundred
    volts. The inverters are basically AC constant current sources. An
    oscillator at ~20kHz drives a high voltage transformer producing a
    couple kV AC at a few mA. This is fed out via a low value capacitor, so
    there is kV available at the output to strike the lamp when it is high
    impedance, then operates as a constant current drive when it is low
    impedance. But the transformer still maintains most of its original
    voltage, it is dropped across the series capacitor.

    This is for the small CCFL invertors used for LCD displays.

    But Phils diode sees the full transformer reverse voltage, potentially
    several kV. A bridge rectifier would avoid this.
    No, he said he only wants <1mA, even the tiniest ones for small LCD
    backlights can do that.
     
  17. Phil Allison

    Phil Allison Guest

    "Marco Trapanese = CONTEXT SHIFTING WOG PIG "
    ** That is not ( on that info alone ) information.

    **** off - wog fool.
     
  18. Joerg

    Joerg Guest

    They can easily supply a few mA but they aren't really well regulated,
    at least not at low voltages. Such converters can be modified with a
    current source in the central primary connection but at very low output
    voltage levels they can behave more like a two-stroke engine with fouled
    spark plugs. Not very clean, if that's important to Marco.
     
  19. Nico Coesel

    Nico Coesel Guest

    I'd use a step-up switcher. Maybe one with a gapped transformer to
    keep the duty-cycle reasonable and then use a linear regulator to make
    the required voltage. Some transistors and an opamp should do the
    trick.
     
  20. Robert Baer

    Robert Baer Guest

    Correction - magnetics is rather attractive..
     
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