功率因數修正器是將輸入電流重新塑形以減少主要諧波上的虛功率損耗。在交流輸入的電源供應器裡，功率因數修正器電路廣泛的討論，在高功率應用中，升壓型功率因數修正轉換器通常操作在連續導通模式，而選擇的控制晶片通常為UC3854，然而操作在低功率的範圍時部分週期會出現不連續導通模式，造成輸入電流失真。此外當轉換器操作在高壓輸入，負載為輕載時，EMI濾波器會造成輸入電壓與輸入電流的相位差。類比晶片內建的功能無法適應操作在各種模式下的電路，導致功率因數變差和總諧波失真提高。利用數位控制的優點，實現更複雜的控制方式以改善功率因數和總諧波失真，有靈活性高、減少元件的數量、抗雜訊能力強、低成本及高效率等優點，研究並應用在升壓型功率因數修正轉換器上的數位控制器是個吸引人的題目。
本論文所提出的數位控制方式採用取樣修正、前饋責任週期和EMI濾波電容器電流注入演算法，以解決上述的問題。實現400W升壓型功率因數修正轉換器，以驗證所提出的控制演算法可行性，實驗結果顯示在連續導通模式與不連續導通模式下，功率因數與總諧波失真皆有改進

Power factor correction (PFC) shapes the input current to minimize the reactive power drawing from the mains. The use of PFC circuits is widely discussed and considered for most off-line power supplies. For high power applications, boost PFC converter operated in continuous conduction mode is usually employed and controlled by analog ICs such as UC3854. However, when the converter operates at lower power range, discontinuous conduction mode will appear during parts of line period, causing input current distortion. Moreover, the input EMI filter causes the significant displacement between input voltage and input current when the converter operates at high-line light-load condition. With functions integrated inside analog ICs, they cannot be adapted to various mode of operation of circuit, resulting in poor power factor (PF) and high total harmonic distortion (THD). In order to implement more complex control scheme to improve PF and THD, the advantages of digital control are exploited. With flexibility, decreased number of components, less sensitivity with change of noise, low cost and increased performance, the digital controller is an interesting topic to research and employ for boost PFC converter.
In this thesis, the digital controller what employs the Sample Correction, Duty Ratio Feed Forward and EMI filter capacitance current injection algorithms is proposed to solve above problems. A 400W Boost PFC prototype is implemented to verify the feasibility of the proposed control algorithms. The experimental results show the PF and THD improvements in both CCM and DCM operations.

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