Idiomatic way to control output voltage of buck/boost converters using microcontroller
Usually Peltier are driven in current but whatever your manufacturer says…
Unless you are using some kind of digital regulator, the standard is to trick its control loop influencing the feedback voltage. Good luck if the FB node is not available externally.
In 99.9% of the regulators the voltage on the FB pin is compared with some constant value and the loop is governed to make them equal. So, usually, you put some divider on the output and put the result into FB. Keep in mind that the FB pin has an internal impedance (it's in the datasheet, often they only give the leakage current).
So you could add some current to make it sense more voltage than it's there: the loop will pull the output down. If instead you sink some current it will see less than the threshold requires and the output will go up.
There are dedicated ICs for that (Linear has one &quot;power margining DAC&quot;, calibrated in mA) but actually the trick work with most voltage output DAC and some current output DAC too. It's only a little more difficult to compute and often some experimentation is needed to find the right value for the summing resistor.