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slow start up -15v regulator circuit

Discussion in 'Electronic Design' started by Paul Taylor, Dec 15, 2005.

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  1. Paul Taylor

    Paul Taylor Guest

    Has anybody done a circuit for a slow start up negative voltage regulator? I
    am using a dual supply of +15 and -15v, I need the -15v to start up after a
    small delay the time is not critical! I know that you can do it with a +15v
    regulator any help on this is much appreciated.
  2. PeteS

    PeteS Guest

    The techniques are about the same. Without knowing the specific device
    and a general idea of circuit topology, it's hard to help.


  3. Fred Bloggs

    Fred Bloggs Guest

    There are basically two approaches: phase-in the regulator reference
    slowly or fool the feedback into thinking output is higher than it
    actually is for the phase-in period. Do you have any description of the
    regulator you're using or is that too much detail for you to handle?
  4. Rich Grise

    Rich Grise Guest

    Well, the pinout of a 7915 is different from a 7815, but other than that,
    just turn the caps and transistors upside-down, and it's the same circuit. :)

  5. LM337 and slug caps on the adj pin?

  6. ehsjr

    ehsjr Guest

    Here's a simple lock out circuit. It's a little different than
    what you requested, but a lock out not only provides the delay
    you want, it guarantees that Vin won't be killed by trying to
    start both regs at once if the + reg fails to start. A delayed
    start won't necessarily do that. It also interlocks the supplies
    so that -15 will drop out if +15 fails (which may or may not be


    +15 > ------+
    | +--- < Vin
    +----+ |
    k| | o---
    [D1] [RY1] o--^
    | | |
    +----+ +---> To - regulator input
    Gnd --------+
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