Introduction to the current control approach
Integrated Inductive Switch-mode Power Supply. Fundamentals Feedback Loops : Voltage and Current Mode Controllers

The principle of current control of a non-isolated static converter is illustrated in figure 14. A first, internal loop processes the current in the inductor. A voltage, the image of the inductance current, is present at the input of a comparator. This comparator provides the value of the duty cycle. A ramp voltage will be added to the current image voltage, in the case of a duty cycle of more than 50%, for reasons of stability, discussed later.

A second, external control loop monitors the converter output voltage. We'll explain later why a single (current) loop isn't enough. The voltage loop compares the instantaneous output voltage with a reference voltage, and a compensation filter provides an error (or comparison) voltage. This comparison voltage with the voltage image of the current in the inductor...