Delaying output voltage in linear power supply

[fjpompeo]

Hi I would like to slow down the increase in the output voltage of the attached power supply. Actually I use an YAESU FP-757HD power supply that lasts up to 1s to the outpuot voltage rise from 0 to 13,8V and want to do the same with this project.
I 'm not sure if install a capacitor in parallel with R1 or U1.
73,
Fernando J. Pompeo -PU2PLL - Brazil

 

[dick_freebird]

A capacitor in parallel with zener U1 will slow the rate
of establishing the reference voltage. However, this
schematic looks wrong to me (expecting a closed loop
linear supply, this has no closed loop feedback from
the (-) node). Even in a closed loop supply, controlling
the reference does not necessarily result in a clean,
start-from-zero ramp. The error amp needs to work
clean with inputs near the + rail (not the forte of
LM741) and preferably the error amp will have excess
(or at least adequate) headroom before the soft start
cycle gets very far at all.

I think the schematic is missing something.

 

[mtwieg]

The schematic does have negative feedback (the earth ground symbol is shared by the negative output and one end of the feedback attenuator). Also an LM741 should work okay for this specific configuration, since when operating none of the inputs or outputs need to be near the supply rails.

Putting a capacitor across U1 will slow down the output voltage ramp rate, though it won't be very linear.