I *may* be barking up the wrong tree here....but if you wish to dop a voltage by a specific ammount....independant of the 'input' voltage, then a voltage reference with a pot across it should do.

The voltage reference would force the voltage across the pot to be fixed, and use use that as a voltage divider. So say you use a 2.5V reference (accurate to 0.1%) adjusting the pot would give you a voltage 'drop' of 0-2.5V.

Not exactly for 'power' but it'll work as a reference for a power regulator.

Hope this helps.

Blueteeth

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Inconsistency is the key to flexibility!

 

It has to be adjustable, 0.1V - 0.9V, and it has to switch in and out at specified levels of the input voltage. It's an interesting alternative to what I posted, and I think it could be made to work. As always, the devil is in the details.
Perhaps you could provide a schematic.

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Ron

 

Hi Ron,

Is it a challenge ?

on1aag.

 

Not exactly, but a lot of people post vague suggestions here, to OPs who are avowed noobs. "You could use a 555, a constant-velocity joint and a couple of Hotsky diodes to do that", as if they could design it themselves, now that they are steered in the right direction. Blueteeth's idea wasn't quite that vague, but, as I said, the devil is in the details. You might be able to save a few parts using Blueteeth's idea, but I don't think he had read the entire thread. Maybe it was just a simple suggestion for a possible way to do it, and he thought maybe someone else could run with it.

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Ron