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step up converter.

Discussion in 'Electronic Design' started by TT_Man, Aug 11, 2007.

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  1. TT_Man

    TT_Man Guest

    Can someone suggest a low cost solution....
    3V lithium I/P, 9-12V O/P unreg is ok. 5mA min, 10 mA max, but must have
    on/off control. Turn on time of up to 5mSec. is ok.
    Problem is to drive a 12V self oscillating piezo from a 3.3V micro....
  2. linnix

    linnix Guest

    Can be less than $1.
    You would need 40mA to 50mA current from 3V.
    Somewhere between the 7V @20mA:

    and the 30V @ 1mA:

    Try playing with R1 (Load resister) to get the right output power.
  3. Joerg

    Joerg Guest

    Cool! How did you program that interactive user interface?

    That one times out but could be a traffic jam on the web.
  4. Joerg

    Joerg Guest

    Cool! How did you program that interactive user interface?

    That one times out but could be a traffic jam on the web.
  5. John Larkin

    John Larkin Guest

    Do you have a pwm output available, or can you afford to make a
    software pwm waveform? Figure 10-25% duty cycle at 20-500 KHz. Then a
    very simple inductive boost circuit will work.

  6. TT_Man

    TT_Man Guest

    Yes I can get a pwm output,but even a simple inductive boost cct is beyond
    my knowledge.
    The larkin cct is ok but there's lots of components and I need to turn it on
    and off. Easy with software pwm O/P... Easy with a boost chip as well but I
    can only find expensive ones....
  7. linnix

    linnix Guest

    Apache + Php + Spice3f5 + gnuplot
    Yes, even with 3GHz quad xenon server with 8G memory. Every time I
    post, people are hitting the server all at once. Try a little later,
    it should be better.
  8. John Larkin

    John Larkin Guest

    | diode
    | |
    d |
    pwm----------g fet cap
    s |
    | |
    | gnd

    Fet is a small logic-level n-channel mosfet.

    L could be, say, a small 200-500 uH inductor.

    Diode is almost anything, 1N914, whatever.

    Cap is, say, 0.1 uF

    Just futz with the pwm duty cycle and period until the output voltage
    is right. Try maybe 25% on, 100 KHz to start.

    The output can't go below 3, so it's possible the piezo may peep a
    little down there. If so, you can use another fet or just a port pin
    to open its low side.

    Or you could do this, which does go to zero when you quit driving

    | diodes
    | | |
    d | |
    pwm----------g fet k cap
    s a |
    | | |
    | | gnd
    gnd gnd

    or this, with a small transformer,

    | +--------ak------+-------out
    | | |
    x||x* |
    x||x c
    x||x |
    *| | |
    | gnd gnd
    pwm----------g fet

  9. Joerg

    Joerg Guest

    And never, ever, let L go into saturation by keeping the FET on for too
    long. Else, phssstt ... POOF.

    Might want to add here that the transformer needs to have an airgap when
    used as a flyback like this.
  10. kevin93

    kevin93 Guest

    An RS232 level translator such as a MAX3232 (or equivalent from
    another vendor) can be an easy solution to this. It has a charge pump
    step up converter built in (just needs a few small caps) and you can
    either use the enable signal where available or put a diode in series
    with the output to drive a self-oscillating sounder by controlling the
    input. You could even drive a piezo sounder (non-self oscillating)
    directly and give it 40v p-p.

    The MAX3232 is guaranteed to provide 10V between the outputs when
    driving 5mA total. (2.5mA each).

  11. John Larkin

    John Larkin Guest

    It will drag down the 3.3 rail lithium battery, the low-voltage reset
    will kick in, and everything will turn off!

    A resistor from gate to ground might be prudent, I admit.

    Hey, this is Digital Power, the wave of the future!

  12. TT_Man

    TT_Man Guest

    Thanks for all the answers and help. I have enough to get a solution I
    think. Not going to 0 is ok as the piezo is cpu controlled and puts out a
    hi(3V3) for off and the pwm will be off.
    neat idea on the 40Vp-p with a max chip too!!
  13. Traver

    Traver Guest

    One last thought: Zetex (and others) make tiny LED driver ICs that are
    meant to do exactly what you want. They come in regulated and
    unregulated versions and make up a boost supply as others have
    mentioned. ZXSC310 is just one example.
  14. Joerg

    Joerg Guest

    .... after which the LV reset lets go, the uC wakes up again and then the
    whole thing starts pumping. Hey, a new oscillator!

    Here's hoping that it's not an industrial grade cell that decides to go

    A SW-engineer once proclaimed that since Max Planck everything can be
    reduced to digital. And this is a guy who plays the guitar and likes
    tube amps.
  15. John Larkin

    John Larkin Guest

    Who makes 56 Henry inductors in 0603?

  16. Who makes 56 henry inductors these days in anything smaller than laser

  17. Hammond manufacturing:
    Considerable smaller than a laser printer, but also
    considerable larger than an 0603.
  18. Joerg

    Joerg Guest

    Should be possible some day soon, with nano-technology. Of course, then
    it'll saturate at a few micro amps so the market would be a bit smallish.
  19. Fred Bartoli

    Fred Bartoli Guest

    Le Sun, 12 Aug 2007 17:28:13 -0700, Joerg a écrit:

    Hmmm, what can you do with 56H nano-inductors and nano-tubes?
  20. linnix

    linnix Guest

    Unlimited dreams. Nano motors and nano generators, etc.
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