Research On The Standardization And Relevant Stability For Middle Power Level AC/DC Converters

This dissertation includes two parts. Part I, topology optimizations for boost type PFC converter and front end DC/DC converter with wide input voltage range. Part II, modeling for peak current mode (PCM) control and average current mode (ACM) control, with the generalized small signal model for current mode controlled converter the stability of the PCM converter is analyzed. The small signal model for PFC converter is built based on the DC/DC model with a little modification, and the stability of pfc converter is analyzed.In the power level higher than 500 watt, the Boost type PFC topology is more preferred due to its high power factor, low thd, wide power range. However the conventional Boost PFC converter suffers from high conduction loss when it is used in universal line voltage. Due to the wide input voltage range (90Vac-265Vac) the efficiency at low line is much lower than high line. The optimization focus on the efficiency improvement, meanwhile the complexity of circuit, the volume of auxiliary network, and power level limitation are considered. Based on the optimization some generalized Boost type PFC topology is deduced and analyzed, which can be used as general topology in system integration application in different power level.In conventional front end DC/DC full bridge converters the efficiency is sensitive to the input voltage range. Therefore when these dc/dc topologies used in wide voltage range (100V-400V) the efficiency falls significantly. To achieve high efficiency at such wide input voltage range, a new rectifier structure at secondary side and a hybrid control strategy are proposed. with the new rectifier structure and new control strategy the voltage stress of rectifier devices is reduced to half. Therefore the conduction loss of secondary side is reduced, and the efficiency is improved.In part 2, an improved small signal model for PCM converter is proposed using geometry method. This low frequency small signal model is more precise than the conventional PCM model. Also the ACM small signal model is built using similar method. with the synthesis of the PCM and ACM model, a general small signal symbolic model is got. using the general model for current mode control, the stability of PCM controlled converter is analyzed with different load, and the design criterion for loop compensation with different load condition is proposed. A simple design criterion for EMI filter is proposed for PCM DC/DC converter based on the proposed small signal model.The small signal model for Boost type PFC converter with ACM control is built. Analysis and experimental results verify that the small signal for PFC converter is almost identical to that of DC/DC converter with same control method. The design criterion for voltage loop band width is proposed based on the synthesizing analysis.