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RE: LF: RE: Todmorden receiver

To: <[email protected]rg>
Subject: RE: LF: RE: Todmorden receiver
From: <[email protected]>
Date: Mon, 27 Nov 2017 17:31:57 -0500
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Hello Paul,

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.  


Jim AA5BW           

-----Original Message-----
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

Jim wrote:

 > 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 
each rail.

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.

Paul Nicholson

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