slow start up -15v regulator circuit

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.

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?

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. :-)

Cheers! Rich

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 desireable.)

Ed

+15 > ------+ | [R1] | +--- < Vin +----+ | k| | o--- [D1] [RY1] o--^ | | | +----+ +---> To - regulator input | Gnd --------+

LM337 and slug caps on the adj pin?

martin