I. INTRODUCTION
The main objective of controlling a DC-DC converter is to
attain a regulated output voltage even under perturbations
which may arise due to change in load current as well as in
presence of disturbances one of the sources of which may be
due to change in input voltage. This is a classical problem of
robust control. Different robust control techniques have been
applied in literature [1]-[9] for voltage regulation of converters.
Both linear and nonlinear controllers have been used for
control of switching power converters [1]-[3]. -synthesis has
been employed in [4] to design a robust voltage controller for a
buck-boost converter to handle unstructured uncertainties.
Genetic algorithm based on Queen-bee optimization method
has been used in [5] to design a proportional-integralderivative
(PID) controller for controlling boost converter. An
improved linear quadratic regulator (LQR) with state feedback
has been attempted in [6] for control of switching power
converters in discrete-time domain. [7]-[9] have applied
different linear and nonlinear control techniques to obtain
robust control of switching power converters. All these
techniques are one degree-of-freedom (1 DOF) in nature which
is based on conventional servomechanism as shown in Fig. 1.
The 1 DOF control scheme suffers from the limitation that the
satisfactory response and loop performance may not be
simultaneously accomplished. The achievement of one
compromises the other.