| In this thesis, the bifurcation and the control of chaos in PWM DC-DC converters are emphatically studied, and contents of study are as follow:First, definition and theories about chaos are summed up. Giving a brief introduction about the working theories of the basic DC-DC converters , buck and boost. On the other hand, their chaos control and development are generalized.Second, a new method of controlling chaos by employing a dynamical nonlinear controller is developed to DC-DC buck converters towards stead periodic orbit. The controller is piecewise- quadratic function in the form of x x .Third, the bifurcation and chaos of open loop current-programmed mode boost converters are studied ulteriorly. Respectively according to ir ef, E and C bifurcation parameters, bifurcation map of boost converter is obtained by applying flash sampling. The chaos control of this circuit system is investigated. Which by employing a dynamical nonlinear feedback controller achieve successfully chaos control in this circuit. The controller is piecewise-quadratic function in the form of x x. This method is suitable for stability control of diversified periodic orbit by adjusting feedback plus in the nonlinear feedback controller.Forth, an eleven-orders piecewise-smooth nonlinear dynamics model for three paralleled DC-DC buck converters is setup at first. Then the nonlinear dynamics behaviors of this converters are investigated preliminarily. It is found that with some parameters, this circuit system appears bifurcation, chaos and period activity. Lastly, the part synchronization is studied. The research results show that under certain conditions, there are plenty of synchronization phenomena in three buck converters'symmetrical variables. Not only is there chaos synchronization and period synchronization, but also chaos phase synchronization and period phase synchronization.Fifth, adopting nonlinear analysis means, the piecewise smooth state equations of the dc-dc...
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