DC-DC converter, what to do?

Question

Electronics

I am making a DC-DC converter, the output should be stable 12 Volts, two options are possible at the input, either 13.5 - 21 Volts, or 16.2 - 25.2 Volts (you guessed it, these are 5S or 6S Li-batteries Ion).
We need maximum efficiency and minimum dimensions. The output current is 100 amperes (!). What is on the market does not fit in size and form factor, and therefore a "custom" is needed.
How and what is the best way to do it?
The easiest way that I came up with, and which suits me, is to assemble a bridge from LM267x with a fixed output, 16 pieces in a row. I'll get my 100 amps. But perhaps there is a better option? Or analogues with large transferred currents, better efficiency (in general, the maximum possible efficiency is needed, ideally more than 96%, and better than 98% in general, since the cooling will be passive), smaller sizes. I just don’t know where to dig and how to select components in general.
These components should also be available, so that in which case it would be possible to buy, conditionally, on Amazon or from the Chinese, and not from one seller. And then I found, for example, this thing: https://datasheets.maximintegrated.com/en/ds/MAX86... it seems like it should fit, 4 pieces, and there will be happiness, but some of it is very rare.

Answer 1

You can parallelize finite field-effect transistors, and not modules with control circuits, otherwise expect trouble.
You need to take a dc-dc buck / step-down external switch chip (these are the keywords for searching) a converter without an integrated output transistor, the required number of mosfets suitable for current / voltage, drivers for them, wind / find a large inductance, and put them together typical scheme.
Here is something like this, for example: www.ti.com/lit/ds/symlink/lm3477.pdf if you can pick up one / two suitable mosfets that it will pull, or even without a driver inside, using external drivers.

Answer 2

passive cooling is not applicable. from ready-made it is possible to find something from powerful controllers for brushed model motors or from sources for electroplating.
the words "bridge from LM267x" can be used with pathos for stories to friends, in practice it is better to forget.
customizing is relatively easy, but with time and money spent on debugging and burned components.

Answer 3

You can look towards multi-phase converters. For example, MAX5038EAI33.
Or dig https://www.powerelectronics.com/white-papers/step...

Answer 4

assemble a bridge from LM267x with a fixed output, 16 pieces in a row. I'll get my 100 amps.

so put and assemble, just do not forget the Schottky diodes for decoupling. Something tells me that you can still stick a group stabilization choke on a powdered iron core.
It would be interesting to read an article based on the results on Habré)

Answer 5

100A is only circuits on external transistors. Paralleling them is not so easy, now polyphase circuits are "in vogue".
That's just the subject of the mailing list flew: https://spb.terraelectronica.ru/rd/TI/PMP11184