功率因数校正技术是减小用电设备对电网造成的谐波污染，提高用电效率的一项有力措施。用电设备的功率因数是衡量其性能的一项重要指标，而提高功率因数的最根本途径就是采用有源功率因数校正技术。近年来，随着对用电设备性能指标要求的不断提高，这一技术成为电力电子领域研究的热点，并得到了广泛的实际应用。 从本质上来讲，功率因数校正的目的就是要控制输入电流，使得用电设备的输入端口仅从交流电网中汲取能量，而不要把任何能量反馈回交流电网，也就是说，要使用电设备的输入端口对交流电网呈“纯阻性”，保证输入电流和电网电压随时成正比。有源功率因数校正技术正是采用电力电子技术中各种基本变换器或其衍生结构，通过对能量传输的适当控制来实现这一目的。 本论文对功率因数的定义、有源功率因数校正(APFC)技术做了分析，在比较三种工作模式的基础上选择了临界导电模式作为本文的研究对象。论文详细分析了临界导电模式功率因数校正Boost开关变换器的工作原理，稳态特性，得出了开关频率与输入电压、输入功率的关系，对器件的应力和输出电压纹波进行了详细的分析，为电路的设计提供了依据。 在此基础上，总结得出了临界导电模式功率因数校正Boost开关变换器的设计方法，并设计出了一台样机，运用Pspice对电路进行了仿真。 实验结果表明，所设计的以MC33262为核心的临界导电模式有源功率因数校正器能在90V~270V的宽电压输入范围内得到非常稳定的400V直流电压输出，并使得功率因数达到0.99，达到了设计要求，系统性能优越。

Power-Factor-Correction (PFC) is a state-of-art technique for reducing harmonic distortion and increasing the power supply network efficiency. Power-Factor(PF) is one of the quality indices of electric equipment, and the Active-Power- Factor-Correction (APFC) is the fundamental way to improve it. In recent years, with the stricter quality requirement of electric equipment, this technique has become the focus in the power electronics research field and has been widely applied. The essence of PFC technology is to shape the input current of electrical equipment, and to take power from the supply network but not to give any back. In other words, the input impedance should present to the AC source a resistive load, and the input current should be proportionate to the AC voltage instantaneously. Using power electrical converter, the APFC technology achieves this by controlling energy transportation. In this paper the definition of power factor and the technology of active power factor correction are analyzed, In the basis of comparing three kind of mode critical conduction mode (CRM) is chosen to study in the paper. The working principle and the steady-state of CRM power factor correction Boost converters are analyzed detailedly. The relationship between the switch frequency and the input voltage and the input power are worked out, respectively. The stresses on each device and the output voltage ripple are analyzed. All of these are in order to provide the foundation of the design. The design methods of CRM PFC Boost converters are summarized. Experiment and simulation results are in positive with the theoretical ones. Experiment results show that the APFC can achieve a fixed output of 400V DC voltage in the universal input range of AC 90～270V. The power factor is 0.99, and the performance of this system has many advantages.