so I needn't have bothered writing all this
No, it's good to read, because what i've now found from “controllable dc-dc converter”s, like IR3475M or Semtech SC190, is when the chip has some easier scheme than external resistors for voltage setting, they all still require a ton of components as drawn in typical applications. Coils, capacitances, resistances. It's weird why they don't make circuits with all introduced. I think i won't be able to gear such a chip up. Or like in the solution like from this article: arduino-digitally-controlled-step-down-buck-dc-converter on eevbldg it's the same too.
That way the digital resistor way also becomes too complicated.
And special Peltier-controllers (i think i also searched for them before, but this page is the most clear), these are too expensive. Like 235 E. So maybe i'll unevitably have to wire up the inductor and a diode. If it's just as much, maybe i won't mess it down. But i'll have to calculate them.
Also i can't fully get this idea: you both, dwightthinker and Paul_B, write that constant current is better. Is it just “than PWM”, or “among the constant current and constant voltage“ still constant current is better? I know that an inductor will do the constant current way, but if i ever can implement any of'em fully, just what to choose.
The other option is to go with a D/A and a linear power source ( possible modified old power supply )
Is it possible to use a DAC here? (i don't understand why linear source though) From the parameter searcher i got the feeling they are small power devices.