| Abstract |
This paper studies the issues in the control design in
a buck converter under constant-current control. The transfer
functions that characterize the dynamical performance of
constant-current-controlled converters are derived from the
corresponding two-port model of a constant-voltage buck
converter by applying duality. The paper presents the controlloop
design procedure for both Type-2 and Type-3 controllers by
means of the control-to-output transfer function. The
conventional control design is usually based on resistive loads,
which actually might exclude the use of Type-2 controllers. The
nominal model, however, reveals that both Type-2 and Type-3
can be used. The constant-current control has, however,
tendency to increase the crossover frequency of the nominal
control-to-output transfer function even a decade compared to
the corresponding transfer function with resistive load. The high
crossover frequency makes the control-loop design challenging
and appropriate zero-pole placements for Type-3 and Type-2
controllers are proposed to tackle the design well. |
