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Increasing DC Voltage

Discussion in 'Electronic Design' started by Dan Mills, Feb 11, 2004.

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  1. Dan Mills

    Dan Mills Guest

    Well, you will need a oscilator of some form to pull this off, no way around
    it. But you might also want to look at the energy balance given above,

    10.6 * 150 mA = 1.59W, 16v @ 100mA = 1.6W so you would in any case need an
    efficiency slightly greater the 100%. Let the Nobel comittee know if you
    pull it off.

    Regards, Dan.
     
  2. EEng

    EEng Guest

    Does anyone know of a way to increase DC voltage WITHOUT using any
    kind of oscillator? Can't use any DC-DC converters that rely on
    oscillators of any kind.... transformers, buck boosts, etc....
    because it goes on a high density PCB wtih lotts of Audio and RF.

    I'm trying to convert a DC input that unreliably varies from 10.6V -
    16V @ 150mA up to any voltage greater than or equal to 16V and can't
    drop under 100mA . FYI, I'm using a 15Vzener to limit anything
    greater than that.

    Currently we're using a simple op amp with gain to provide the higher
    voltage but it causes the necessity for several dynamic circuits to
    develop bias voltages throughout the circuit that change with the
    input. What I'm trying to do is eliminate all the extra circuitry
    that accounts for varying biases. If I can accomplish this, it will
    reduce component count by 20% and PCB real estate by 30%.

    This ones a poser....several engineers at a Fortune 50 company and I,
    have been scratching our heads over it. If I haven't been absolutely
    clear on what I need, please let me know which parts need explaining.
    Thanks in advance, this NG has always rocked.
     
  3. Without using an oscillator (or having AC available to you from some other
    part of the circuit), you are not going to succeed.
    If there is any point where there is an AC signla available, there are a
    number of solutions. Otherwise you will _have_ to use an oscillator.
    Proper design, and careful board layour will allow such devices to be used
    in 'noise critical' enviroments. As an example, I have a board here used as
    part of a sensor head, that presents of 10^12 ohm input impedance to the
    sensor, and is reading signals in the uV area, yet has such an inverter, and
    gives no problems. It comes down to careful design.

    Best Wishes
     
  4. Ian Stirling

    Ian Stirling Guest

    LED + solar cells.
    Should have an efficiancy of over 5%, picking the right LED.
     
  5. EEng

    EEng Guest

    That's the conclusion we've come to as well. I just wanted to see if
    anyone else had an idea we hadn't thought of. Looks like the op amp
    will have to remain, and the variably considered bias voltages dammit.

    Thanks for trying. Great minds not only think alike, they also pain
    alike.
    LED + solar cells is not an option.
     
  6. Tim Wescott

    Tim Wescott Guest

    I've seen this done, too, with great success. We were measuring to 16-bit
    accuracies with no problem with step-down regulators on the board. Linear
    Technology and National both have app notes on ultra-quiet switched
    regulator design. If you're really going to lose 30% of your component then
    the layout and shielding attention is probably worth it.
     
  7. Take 2 caps, charge them from the voltage you have.
    Now disconnect and put them in series.
    But you will have to do this repeatedly, so you assign someone to do
    it for you (cheap labor country).
    To toggle the switch....
    But an OSCILLATOR could switch some transistors....
    In stead of oscillator you can use usenet bitstream.
    I DID IT WITHOUT OSCILLATOR :)
     
  8. Jamie

    Jamie Guest

    going from what your describing here i would say that your merly using
    the DC input as a refence to activate a function ?
    why not use a voltage comparator ?
    you can set the - input of an op amp around 10 volts and the supply
    voltage of the OP to be 16 volts.
    using the + input of the OP you can then have a steady 15 volts
    when ever the input is >= the - input..
     
  9. Ben Bradley

    Ben Bradley Guest

    I thought of the LED-and-photocell thing too. There's something
    that might have a little more efficiency, that "technically" meets
    your specs (it's "not an oscillator"), but is even less practical: A
    dynamo (motor-generator). So, now that you've totally dismissed me...

    Presuming you're concerned about audio and RF interference
    generated by the voltage converter, some sort of sinusoidal (so almost
    all of its current pull variation and radiation is at the fundamental
    frequency) RF oscillator (in the 20kHz to 200kHz range, low enough
    that it radiates very little) is your best bet. There's a model of
    studio condenser microphone (I forget what model, it was discussed on
    rec.audio.pro) that uses an RF oscillator and transformer to generate
    its 50-odd volts bias voltage (if you haven't guessed, that's a
    demanding, low-noise application). A well-designed (probably Class A,
    or for better efficiency, push-pull Class AB) converter circuit should
    not generate significant signal interference to nearby circuitry.
    Great, send us our consulting fee. :)
     
  10. Add a battery in series with the supply?
     
  11. N. Thornton

    N. Thornton Guest

    Well, it depends on your app but another perhaps could be to use an
    already existing signal amplified to drive the convertor power stage.
    This sneaky way of getting round interference problems is just to save
    design time, if you have a suitable f already present.
    One of us isnt making sense of this, but I dont know who. You cant get
    a higher Vout from an opamp than its Vsupply: perhaps you could
    explain clearly?

    Also why must you convert an unstable dc voltage? With the V figures
    you give, and what youre asking, I'm guessing its a lead acid powered
    item. Why arent you designing the circuit to run on whats given? What
    does the circuit do and why must it have >16v?
    Could you explain this varying biasing? It is a mystery to me, hence
    it is impossible to suggest anything.

    Regards, NT
     
  12. So!? But Whatever as long as they pay....
    So this is *not* a power supply - because the supply of that op amp must be
    higher - why is it a problem then? You can apply any transformation you
    like.

    PS: If it is a power supply, the circuit should be redesigned to eat
    whatever it is fed!
     
  13. R.Legg

    R.Legg Guest

    It's got RF but you can't allow (another) oscillator on the board?

    Use the RF section to generate the milliwatts required for a higher
    integrity rail. Your RF guys should be up to it. Believe me, if it's
    RF, you've got AC on board.

    Partition critical sections only to run on the higher integrity rail
    (minimum power drain).

    RL
     
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