Re: power supply discharge

On Sun, 6 Oct 2024 15:11:21 +0100, Clive Arthur
<clive@nowaytoday.co.uk> wrote:

On 06/10/2024 01:56, Jasen Betts wrote:

On 2024-09-27, john larkin <jl@glen--canyon.com> wrote:

On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
>

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.

>
A DC-coupled audio amplifier chip might work as a fully-controllable
bi-directional power supply if your current and voltage requirements
were fairly modest.  They have the advantage of being relatively cheap,
well-protected and very fast (by power supply standards).  Some of them
have the tab at input earth voltage, so they don't require isolation
from the heat sink.

>
Unfortunately, it has to be a switching regulator.

 
how is that different from a class D audio amplifier?

>
Audio doesn't go down to DC.

Audio amps are usually full-bridge, which doesn't reverse pump up the
power supply under pathological conditions, like a half-bridge can.

And loudspeakers are very inefficient so don't store much energy and
as you note don't go down to DC, again storing not much energy.

A big capacitor bank, or a battery, or a motor can store a lot of
energy, so there can be a dilemma when the load voltage is higher than
the supply setpoint.