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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: power supply discharge
Date: Sat, 28 Sep 2024 09:44:44 -0400
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On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:

>
>Given a benchtop power supply, you can turn the voltage up and then
>down, and it goes down. Most have a substantial amount of output
>capacitance, and can be driving an external cap too. So something
>pulls the output down.
>
>I guess that there are no standards for this, but I've never seen a
>supply that just hangs high when it's cranked down.
>
>I'm designing some programmable multi-channel power suplies and that
>is one of many tangled issues in the project.

Twiddling the adjustment knob on a bench supply doesn't 
represent a dramatic change - and most adjustible 
supplies don't load their output terminals with a 
lot of capacitance.

DC coupled programable supplies, or bipolar programmable 
supplies are made to drive loads in the first and third 
quadrants.

There are issues in the second and fourth quadrants, where 
the supply is expected to absorb power.

An amplifier driving a pure reactance experiences the same 
losses as driving a dead short.

RL