Study On Pulse Train Control Based Switching DC-DC Converters

Pulse train(PT)control is a new control method for converters,it has the advantages of simple structure,fast dynamic response and good robustness.In addition,it does not need error amplifier and compensation network.For PT controlled switching converters,as the inductor current is in continuous conduction mode(CCM),the output voltage has low frequency oscillation,which affects the performance of converters seriously.This thesis mainly studies the strategies of suppressing low frequency voltage oscillation as PT controlled DC-DC converters are operated in CCM.Firstly,the research background and significance of switching DC-DC converters are summarized,and the converters are classified from two aspects of topology and control method.In addition,the working principle of PT control is clarified,so are the research statuses of PT controlled DCM and CCM converters.Secondly,the pulse phase shift pulse train(PPS-PT)is proposed.The mechanism of PPS-PT suppressing low frequency oscillation is introduced,and the approximate discrete iteration model is established.By mumerical simulation and experiment the proposed novel method can be verified,simulation and experimental results indicate that low frequency oscillation can be suppressed effectively as the shifting phase is set reasonably.Thirdly,the capacitor current feedback pulse train(CCF-PT)is proposed and applied to parallel connected Buck converters.Capacitor current is introduced to determine the selection of control pulse together with output voltage.The working principle of CCF-PT control and mechanism of low frequency oscillation suppression are analyzed in detail.Simulation and experimental results indicate that low frequency oscillation can be suppressed as the feedback coefficient of capacitor current is selected properly.Finally,a PT controlled single input dual output(SIDO)Buck converter with coupled inductor is proposed.The working principle of SIDO Buck converter is analyzed in detail.The mechanism of loop 1 suppressing low frequency oscillation is analyzed.The output power characteristic of loop 2 is discussed.The results show that low frequency voltage oscillation of loop 1 can be suppressed by reasonably configuring the inductor coupling coefficient and the voltage of equivalent power supply terminal,in addition the maximum output power of loop 2 can be controlled.