Based on the those additional details, it might be worth a quick check of the
voltage-loop stability margin: if for example your load draws 50 ma, briefly
add a 390 ohm 2W resistor across a 15V output (I = 50 ma + 38 ma = 88 ma, well
below any overcurrent limit on the 100 ma module) and quickly release it. If
the output voltage doesn’t ring (i.e. if the step-load response is overdamped),
no problem, stability margin with the 47 uF capacitor is fine. The
instability-relevant ring time constant would likely be 10 us < t < 1 us; any
faster features would be irrelevant to voltage-loop stability. Success with
this test could rule out a narrow stability margin that could otherwise at some
later date (with aging and temperature) add noise.
From: [email protected]
[mailto:[email protected]] On Behalf Of Paul Nicholson
Sent: Monday, November 27, 2017 2:27 PM
To: [email protected]
Subject: Re: LF: RE: Todmorden receiver
> Considerably reducing DC-DC converter output filter > capacitance and/or
> load current can almost always solve > the problem of erratic power supply
> startup related to > high source resistance,
When I checked the data sheet for the IP1215S isolating DC-DC converter I
spotted that it said max 47uF load capacitance - and I had 100uF hanging on
Hopefully that's the answer. For some reason I can't reproduce the start-up
problem in the office even though I've got slightly higher cable resistance.
I like these XP power IP series converters, good isolation and they have a
large input voltage range.