remote sense on power supplies

[zappedagain]

I'm used to using the remote sense lines on a power supply when I have a widely varying load, so the line loss is compensated to keep the voltage constant at the load independent of current draw. I've only done this with the load fairly close to the supply though.

A colleague is suggesting using this technique across a long cable between the power supply (controller) and a sensor head. I would think the delay along the cable could cause loop instabilities, and potential EMC/EMI pickup on the cable could drive the power supply crazy. Am I being overly concerned, or does it really depend upon the application? Any success or horror stories out there?

Z

 

[jimbofitz]

A shielded remote sense wire would certainly reduce the EMC/EMI issues you are concerned of. I wouldn't worry abouth the a delay but I'm not sure what kind of distance you are speaking of.

 

[ScottyUK]

Shouldn't be anything to worry about on the loop stability, and good design practice should keep keep the EMI under control. Include a low-ish value resistor between the main output and the sense lines to cope with the day when the sense line gets disconnected.


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If we learn from our mistakes I'm getting a great education!

 

[IRstuff]

1 km roundtrip at c = 6.7 microseconds, so unless your load is violently changing at 150 kHz, there should be little problem.

However, I doubt if the the sense circuit has that fast a response time, in which case, you'd be seeing a low-pass filtered response to the load, which should be OK.

TTFN

FAQ731-376

 

[zappedagain]

Thanks all! I'll keep that option open.

Z

 

[Comcokid]

I have seen the following done - at the power supply, connect the remote sense to each supply terminal with a 100 Ohm resistor. Then run the long length sense line to the remote load. Normally, this is done so if the sense line should open, the power supply and load will remain within reasonable limits. But with a long sense length this should make it very difficult to couple any significant noise to the sense line even given any phase delay.