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Is there any variable DC-DC converter suitable for pre-regulation?
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Wolfgang:
Hi,

I never suggested to build something you dont understand. I never do that, either.
Nobody stops you from learning and understanding designs from others (including simulation) and improving or adapting them on your own.

bloguetronica:
Sorry for misunderstanding. I never taken you as being that "assertive", and it was not my intention to do so, hence the word "suggestion".

Anyway, I have an idea for a schematic, but I'm having a busy day. Will post it as soon as possible.

Kind regards, Samuel Lourenço
T3sl4co1l:
So you want something you created and understand, but that is worse than the standard approach?

Tim
bloguetronica:
Hi Tim,

How it is worse? I didn't presented the schematic yet!  What is the standard approach? Am I taking the wrong approach by basically not copying a design (at least blindly)? Although Wolfgang presented a pretty much valid and working design, I decided not to use it, but thanked anyway.

What can I say? I like to reinvent the wheel, despite the fact of often being criticized for that. I like to experiment, and even if I do mistakes it is not important, because I can learn from them. Nothing beats our own experience.

I also don't know the concept of "standard" in electronics. There is just different ways of doing things. And since I was over-complicating I just decided to be back to the drawing board (the "computation block" would never work as intended, BTW, because I was thinking wrong in the first place). Simpler, more elegant design, with less problems and caveats.

Regarding the pre-regulator DC-DC, I'll use the PNP transistor to control it, and it will be based on the output voltage. As you suggested earlier:

--- Quote from: T3sl4co1l on September 08, 2018, 03:59:26 am ---You don't want the SMPS output to track DAC/setpoint output, because it won't follow under a current limit condition.  That's why it's made to follow the actual output instead. :)
...

--- End quote ---

Kind regards, Samuel Lourenço
T3sl4co1l:
It's a behavior I've seen a lot in audiophile circles, and that's probably why I snapped at it.  They can get away with it, because audio amplification is a very easy problem (tolerant of poor solutions), and few of their designs ever have to face the rigors of reality.

It works, for some range of "works", but that doesn't mean it's a good idea.

It's very much a good thing to be different, to explore the available design space -- there are many valid ways to wire up components (although very, very many more invalid ways in total!), all with different tradeoffs.  Having the experience to know which combinations of tradeoffs are best for a given application, is the payoff.

The problem is if you get far enough into the project that it works, then you stop without going the extra step to finish it up, to make it work consistently and reliably -- that's the part that bugs me the most.

Another way to put it: is this a learning experience, or a challenge towards a stated goal?

If it's the former, definitely do play around and test -- emphasizing in particular, the many ways a circuit can go wrong.  Test the extremes of inputs and outputs, of environmental conditions (temperature and such), of component ratings.  See how things fail, and understand why manufacturers choose ratings as they do.

While, if it's the latter, you have a clear goal in mind -- a power supply with some minimum efficiency, maximum noise, operating range, functionality and so on (probably with size and cost being secondary considerations) -- there is a far smaller space to choose from, that will meet those goals.

I'm probably wrong for emphasizing a goal here, and that's probably because my experience points me, very quickly, to a set of possible solutions.  I should reflect more often on what it was like without that experience...

Tim
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