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Modifying power Supply - worth it?

Discussion in 'Electronic Design' started by quietguy, Nov 6, 2005.

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  1. quietguy

    quietguy Guest

    Yep, shows a nice square wave from the cal terminal
    While I wouldn;t want to challenge the 'rightness' of what you say Walter, my
    initial thoughts are that to provide such an artifical power source may lead to
    probs when the circuit has to eventually face the real world.

    Isn;t it better to design so that the circuit handles the real world of power
    surges etc? Rather than find this out later?

  2. message

    IME, the first time you power up your circuit, the question is not usually
    "how well does this handle real world conditions", it's "did I wire this
    thing up the right way or not". If the answer is "or not," you'd rather
    find out when the voltage on it is about a volt, not when it's 5v and too

    David's right that there are circuits that don't handle a gradual ramp up in
    power; latchup, oscillation. But personally I'd worry less about that than
    about zapping an untested circuit with full juice.

    Current limiting is obviously a very important feature in a power supply.
    With good current limiting many other sins are forgiven. Sometimes I start
    the circuit at full voltage but with the current limiting set to zero, and
    then ramp in the current instead of ramping up the voltage.
  3. quietguy

    quietguy Guest

    OK thanks Walter. Having just got back into electronics after a 30 year break,
    I am not used to all the luxeries that are around today - Back in those days
    playing with my Exidy scorcerer and a bunch of TTL interfacing stuff it was a
    matter of getting right 1st time!

    But times have changed, and I need to change too

    Thanks for the good advice


  4. Yes, adjustable current limiting is an essential feature of any good
    power supply.
    Gotta watch it sometimes though, one setting might be OK for the steady
    state current requiremens of the circuit, but the power on current
    requirement is often much larger. So the current limiter will kick in
    for a brief period and can cause latch up problems as I mentioned. Can
    be really hard to track down if you don't know what's happening.

    If you have a current limited supply then the general rule is as you
    mention - set the volts you want and ramp up the current.
    If you don't have a current limited supply then you would do the
    opposite and ramp the volts up and watch the current meter.

    Dave :)
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