Current mode control as usually implemented
in switching power supplies actually senses and
controls peak inductor current. This gives rise to
many serious problems, including poor noise
immunity, a need for slope compensation, and
peak-to-average current errors which the inherently
low current loop gain cannot correct. Average
current mode control eliminates these problems
and may be used effectively to control currents
other than inductor current, allowing a much
broader range of topological application.

for details information, you can download:\Average Current Mode Control of Switching Power Supplies