| In this paper, several key technologies of DC-DC converter with large conversion ratios are analyzed.First, Transient analysis and control of bias magnetic state in transformers of on-Line PWM switching full bridge DC-DC converters.An indirectly coupled field-circuit method is introduced to predict the transient bias magnetic state. To increase the flexibility of the proposed model, a novel transformer model, which can address not only its basic input-output characteristic, but also the nonlinear magnetizing inductance, are proposed. Finally, the peak magnetizing current control method based on on-line magnetizing current computation is introduced.Second, system stability design and output voltage ripple analysis of a peak-current-mode controlled Buck converter. To drive the converter into the stable state with the input voltage and the load varying globally, a symmetric method for design of the PID controller is introduced. As the output voltage ripple of the converter is also influenced by the load, a method based on the combination of the Fourier transform and the AC equivalent impedance of the output circuit is proposed, which can improve the current model by considering only the capacitance. To verify the theory, a switching detailed model is built for a peak-current-model-controlled Buck converter. The results of transient and steady state performance obtained by numerical simulation in the Matlab/Simulink environment agree well with the theory.Third, Modeling and analysis of DC-DC converter based on chaotic dynamics, Based on Matlab software, Laplace transform model, switching detailed model and precise mathematical discrete model of voltage-mode controlled Buck converter are constructed, the algorithms of some numerical methods in chaos research are given, and the time-domain waveforms, phase-space trajectory, poincare sections, bifurcation diagram are drawn by Matlab programming, which can indicate the complex dynamic behaviors of the Buck converter.
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