[Nut-upsdev] Voltage transfer points.

[Kjell Claesson]

sön 2006-02-26 klockan 18:19 -0500 skrev Charles Lepple:
> On 2/26/06, Kjell Claesson <kjell.claesson at telia.com> wrote:
> > As I find it, there is only one point where the boost or buck (trim)
> > kicks in.
> 
> Right, but the input voltage at which it exits the boost or trim mode
> might be slightly different than where it enters that mode.
> 
Yes you are right about that. But this is due to the fact that if it 
would use the same voltage, it could start oscillating setting buck
(boost) on and off if the voltage is on the transfer point.

It is not so difficult to make the on and off voltage to be the same
by electronic. You don't get the same hysteresis as you do on a room 
termostat.

Measuring the voltage with a OP-Amp to a reference gives a sharp point
for the trig-point. As the op has high input impedance it would not
interfere with the voltage measuring.
 
This could kill your ups fast if it starts to switch this on and 
off. So i think they have split the on and off points on purpose. 
 
> It's like your thermostat - there is usually some hysteresis around
> the temperature set point.
> 
> On the other hand, some UPSes may just implement a time filter that
> checks to see if the voltage has been past the set point for a certain
> amount of time.
> 

Yes and that is why i put it on the list. Good to discuss this so we 
can make the best of it for all.

Btw the on-line type ups don't have the buck (trim) and boost. They
have bypass ranges just like the boost and buck ranges before it goes
to battery. 

> As Peter mentioned, it would be good to get clarification from Arnaud
> as to whether the separate settings are all necessary.

Yes, I'm not in to change anything. But as i started to rewrite parts
of the bcmxcp driver. I noticed this and needed a clarification.

Thank's for your answers.

/Kjell