| This paper studies the basic structure, operating principles of ZVT-boost soft-switching PFC circuit and the implementing principle of soft switch. Based on those information, main circuit structure was ascertained,and proposal of control system was proposed. ZVT- boost soft-switching converter with 200W output power and DC 400v output voltage also is studied and designed in this paper. Among those contents , the set up of DCM/CCM combined turnon mode average model, average model circuit structure under PSPICE simulation software environment and the design of main circuit and controlling circuit were covered,and by using PSPICE simulation software, simulating analyses of designed system were done . In view of the characteristics of the PSPICE simulation software , i.e. accuracy , visualizability and the consistency of the simulation result and the test result, the principles obtained from simulationg could be used to guide practice.During the design process of main circuit parameters , through the combination of theory study and computer stimulating, the rules of influence to the loss of main switch and auxiliary switch caused by auxiliary resonance circuit parameters were obtained , and the selective principle of full-range soft-switching auxiliary resonance circuit parameters in fixed loading condition were ascertained. The rules could be used to guide practice, shorten design process and help the accurateselection of relevant parameters. It could also provide information for the design of high quality soft-switching circuit and could be used to help the resonance parameter selection of other types of soft-switching converter.The setup method of DCM/CCM combined turnon mode average model discussed in this paper shows the characteristics of simple and visualizability, and it provides a new way for the founding of switching-mode convert average model.Becaused of the diversity and complexity of soft-switching circuit and difficulty to find suitable soft-switching controller,ZVT-boost soft-switching PFC control circuit which meet the system requirements was design by ourselves. The study and design of control circuit including: study and design of current loop, voltage loop, frequency generactor, time sequence logical circuit of soft switch , driving circuit and protect circuit o The rules of influence to circuit performance caused by compensation circuit parameters of current loop and voltage loop were studied,thus the selective principles of these parameters were drew.The characteristics of designed conrol surcuit are: 1. Wider input AC voltage range (70VAC-25OVAC);2 Within the input voltage range the output voltage and the output power were constant;3. Main and auxiliary switch were in soft- switching situation within the whole input voltage and load range;4.Minor harmonic distortion, high power factor.5. Zero voltage inspect circuit was used to check the voltage of drain electrode ofmain switch, make the main switch turn on when reaching zero voltage,meanwhile the auxiliary loop will be cut off timely, then the cycling loss of the auxiliary loop was decreased. This design overcomes the disadvantage of previous way,i.e. the auxiliary loop working on in system-allowed fixed max working time.Finally, simulating analysis was performed on the designed system and efficiency and power factor were calculated based on it. Comparactive analyses were done among no-improved ZVT-boost soft switch PFC converter, improved ZVT-boost soft switch PFC converter and hard-switching boost-PFC converter. The rules of influence to circuit performance caused by input inductor and output capacitor were studied,and the selective principles of these parameters were obtained. The rules of influence to circuit performance caused by high frequency triangular wave were analysed. Through simulation studies,some critical conclusions which could be used to guide the later R&D were obtained. |
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