ABSTRACT
DCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 7.3 The Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
7.3.1 System Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 7.3.2 Controller Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
7.3.2.1 Derivation of Existence Conditions . . . . . . . . . . 137 7.3.2.2 Derivation of Control Equations for
PWM-Based Controller . . . . . . . . . . . . . . . . . . . . . . . 140 7.4 Simulation Results and Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
7.4.1 Buck Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 7.4.1.1 Steady-State Performance . . . . . . . . . . . . . . . . . . . . 146 7.4.1.2 Transient Performance . . . . . . . . . . . . . . . . . . . . . . . 148
7.4.2 Boost Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 7.4.2.1 Steady-State Performance . . . . . . . . . . . . . . . . . . . . 148 7.4.2.2 Transient Performance . . . . . . . . . . . . . . . . . . . . . . . 150
7.4.3 Buck-Boost Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 7.4.3.1 Steady-State Performance . . . . . . . . . . . . . . . . . . . . 154 7.4.3.2 Transient Performance . . . . . . . . . . . . . . . . . . . . . . . 154
7.5 Other Application of DCM SM Control: Hybrid Dual-Operating-Mode Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 7.5.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 7.5.2 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 7.5.3 Simulation Results and Discussions . . . . . . . . . . . . . . . . . . . . . 162
7.5.3.1 Buck Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 7.5.3.2 Boost Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
DC-DC converters can operate in either continuous conduction mode (CCM) or discontinuous conduction mode (DCM), depending upon the choice of the
of Switching Power
and the relative sizes the load and the inductive storage. The design of pulse-width modulation (PWM)-based SM controllers for DC-DC converters in CCM operation has been thoroughly discussed in the previous chapter, in which the system models, SM control laws, and computer simulations are presented in detail. In practice, DCM operation enjoys a faster transient response at the expense of higher device stresses. It is still a popular operating mode for low power applications and its practical importance should not be overlooked. However, the results presented in the previous chapter are not applicable to DC-DC converters operating in DCM because of the fundamental difference in the dynamical property between the two operations. Thus, if PWM-based SM controllers are to be used for DC-DC converters in DCM operation, system models and control laws have to be redeveloped. The main difference lies in the structural composition of the respective converter models for CCM converters (bilinear) and DCM converters (trilinear).
