buck converter feedback control
The LT7803 will try and regulate the voltage on the Vfb pin to 0.8V (in its regular running mode). That means if the voltage is lower on this pin it switch 'more' and allow more current to regulate the voltage up. You don't need a resistive divider to accomplish the feedback, you can insert anything you like (like a bunch of opamps, you could even turn this into an MPPT tracker, I've done that once before, or even a DAC an ADC so you could put software in the loop). But realize that you could create instabilities, and you will have to compensate the loop to keep it stable.

Source: https://www.analog.com/media/en/technical-documentation/data-sheets/ltc7803.pdf