文档介绍：Current-Mode Control:
Modeling and its Digital Application
Jian Li
Dissertation submitted to the Faculty of the
Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
in
Electrical Engineering
APPROVED
Fred C. Lee, Chair
Dushan Boroyevich
Ming Xu
Douglas K. Lindner
Carlos T. A. Suchicital
April 14th, 2009
Blacksburg, Virginia
Keywords: current-mode control, modeling, describing function,
equivalent circuit, digital control, DPWM
© 2009, Jian Li
Current-Mode Control:
Modeling and its Digital Application
Jian Li
(Abstract)
Due to unique characteristics, current-mode control architectures with different
implementation approaches have been widely used in power converter design to achieve
current sharing, AVP control, and light-load efficiency improvement. Therefore, an
accurate model for current-mode control is indispensable to system design due to the
existence of subharmonic oscillations. The fundamental difference between current-mode
control and voltage-mode control is the PWM modulation. The inductor current, one of
state variables, is used in the modulator in current-mode control while an external ramp is
used in voltage-mode control. The dynamic nonlinearity of current-mode control results in
the difficulty of obtaining the small-signal model for current-mode control in the frequency
domain. There has been a long history of the current-mode control modeling. Many
previous attempts have been made especially for constant-frequency peak current-mode
control. However, few models are available for variable-frequency constant on-time
control and V2 current-mode control. It’s hard to directly extend the model of peak
current-mode control to those controls. Furthermore, there is no simple way of modeling
the effects of the capacitor ripple which may result in subharmonic