The other day I built a basic buck power supply on a breadboard from scratch (i.e. sawtooth generator, comparator, zener power supplies for control circuitry and references, feedback loop, and low-pass filter for the power output).
It got me thinking - could any off-the-shelf power supply chip be made into a current source using the following arrangement of the feedback?
simulate this circuit – Schematic created using CircuitLab
For the sake of example here, this would be a buck converter with an internal 1V FB reference which has been designed as a 1A current source. Rather than the traditional voltage divider feedback loop for voltage feedback, this uses a 0.01\$ \Omega \$ feedback resistor with some generic amplifier block (could be an IA, could have an active low-pass filter as well for noise/anti-aliasing etc.) with a gain of 100x.
Once the voltage is increasingly ramped until the current through the resistor hits 1A, the feedback voltage will reach 1V - and so the power supply will maintain the voltage (and therefore current) at that level.
Obviously, buck, boost, or buck-boost would have to be chosen appropriately to ensure the output voltage was correctly reachable, over the desired current compliance range.
Any first-glance reasons why this wouldn't work?
EDIT: Decided to simulate it with a basic linear tech buck part. Seems to work (note, this has a reference of 2.21V). Obviously as some have pointed out, the op-amps will affect the transfer function in the feedback loop. I believe as long as the correct op-amps were chosen (high-frequency, high CMRR, proper filtering), this is a viable solution however. Feel free to disagree, but.