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1、南京航空航天大学博士学位论文 - i - 摘 要 本文研究了两部分内容：隔离 Boost 变换器和反激逆变器。 电气隔离型 Boost 变换器具有高频电气隔离，易于多路输出，输入电流纹波小，负载短路时可靠性高等优点。它适用于有隔离要求的高压多路输出、双向PWM 直流变换和单级 PFC 等场合。本文对隔离 Boost 变换器的发展作了系统的总结和分类，并详细讨论了它们的特点。研究一种新颖的隔离 boost 变换器，它具有开关管电压应力低，没有变压器单向磁饱和问题，可以实现交错并联双管正激电路所有开关管零电压开关。 但是隔离 Boost 变换器需要重点解决两个问题：1) 减小功率开关关断时两端浪涌
2、电压；2) 隔离 Boost变换器的起动。本文综合了两种箝位电路：1) LCD箝位电路，箝位电容上电压不反向；2) 通过增加一个与升压电感耦合的反激线圈和一个连接到输出电容的整流二极管，构成反激箝位电路。 分析了两个起动过程：1) 电压电流双闭环控制 Flyback 变换器的起动过程， 可分为电流过冲阶段，电流调节器调节阶段和电压调节器调节阶段三个阶段。2) 电压电流双闭环控制隔离 Boost变换器起动过程分 Flyback 工作、Buck 工作、Boost 工作三个工作阶段。起动电流过冲发生在 Flyback 工作阶段。 研究了一种反激逆变器， 它是由两路双向反激直流变换器原边并联副边串联构
3、成。根据其结构特点，提出差动控制和单边控制方案，单边控制策略克服了差动控制策略由于能量循环导致效率低的缺点。研究了两种反激逆变器的单边控制方法：同一双向反激直流变换器两只开关管非互补导通和互补导通。 基于电流断续模式的单边非互补导通控制反激逆变器：副边常通开关管在常通期间流过负载电流，具有较小的导通损耗；逆变器占空比不受拓扑限制，可以在 0 到 0.8 之间变化，方便的实现宽的输出电压范围。实验结果表明该逆变器具有以下优点：双向功率传输、拓扑结构简单、使用器件少、控制方案简单、可靠性高以及良好的动态响应。 基于电流连续模式的单边互补导通控制反激逆变器： 输出功率较大时实现同 步整流，较小时实现
4、零电压开通，从而有效地降低了整流二极管导通损耗，将效率提高到 85.8%。 关键词：变换器/Boost变换器，箝位，起动，逆变器，反激变换器，同步整流 隔离 Boost 变换器和反激逆变器的研究 - ii - Abstract The main research contents of this dissertation have two parts: isolated boost converter and flyback inverter. Isolated boost converter has advantages of high frequency electrical isolat
5、ion, multi- output solutions, lower input ripple current and high reliability for the short circuit of load, etc. It is attractive in applications such as high voltage multiple outputs with isolation requirement, single stage power factor correction and bi- directional DC/DC converters. This paper c
6、omprehensively summarizes the typical topologies of isolated Boost converter family, and classifies existing topologies into several categories. The characteristic of those topologies are analyzed in detail. A novel isolated interleaving two- transistor forward boost converter is proposed in this pa
7、per. This converter has less voltage stress of power switches, and no transformer magnetic deviation. In all interleaving two- transistor forward switches, zero voltage switching can be obtained which can apparently improve the power density. However the isolated boost converters need to resolve two
8、 problems. 1) The transformer leakage inductance will cause surge voltage across the switches. Two clamp circuits are combined to solve this problem: LCD clamp circuit, in which the voltage across clamp capacitor is no reverse; flyback clamp circuit, which consists of an additional flyback winding c
9、oupled with the boost inductor and a diode connected to the output terminal. 2) The low output voltage causes the control loop to call for maximum duty cycle and a large surge of input current when converter starts up, thus damaging the converter. The peak current mode PWM controller can limit the d
10、uty cycle. Flyback can deliver the stored energy in primary side to the output side during power switch off period. These two methods can alleviate the inrush current. This paper research voltage and current close- loop control Flyback converter and isolated Boost converter with peak current mode PW
11、M controller. The start process of Flyback converter is divided into three stages: inrush current, current regulating and voltage regulating stages. The start process of isolated boost converter is divided into three stages: Flyback work, Buck work and Boost work. Isolated boost converter inrush cur
12、rent occur during Flyback work. A flyback inverter is studied in this paper which consists of two bi- directional 南京航空航天大学博士学位论文 - iii - flyback converters in parallel at the input- end and in series at the output- end. On the basis of structure, it proposes two control scheme: difference scheme and
13、 unilateral scheme. Unilateral scheme overcome the disadvantage of difference scheme circulating energy. Two kinds control of unilateral scheme is studied in this paper: two switches are non- complementary turned- on or complementary turned- on in same bi- directional flyback converter. Based on the
14、 discontinuous conduction mode (DCM) operation of the flyback inverter, unilateral non- complementary control scheme is established. Wider range output voltage can be realized by varying the duty ratio from 0 to 0.8. The conduction losses can be outstandingly reduced by load current flowing through
15、the normally- on switches. The experimented results show the validity of the flyback inverter that have some advantages as single stage, electrical isolation, bi- directional power flow, compact topology and good dynamic response. Based on the continuous conduction mode (CCM) operation of the flybac
16、k inverter, unilateral complementary control scheme is established. Synchronous rectification in large power and soft switching in small power reduces the conduction losses of the rectifier diodes and improves the efficiency of the inverter up to 85.8%. Key words: converter/Boost converter, clamping circuit, start up circuit, inverter, Flyback converter, Synchronous Rectification 承诺书 本人声明所呈交的博士学位论文是本人在导师指导下进行的研究工作及取得的研究成果。除了文中特别加以标注和致谢的地方外，论文中不包含其他人已经发表或撰写过的研究成果，也不包含为获得南京航空航天
