寬廣負載下具有較高效率及功率因數之數位式功率因數修正控制方法

Abstract

一個採用傳統類比控制的升壓式PFC轉換器，要在寬廣的負載變化下，均能保持高效率與高功因，是相當困難的。本文提出一種數位多模式PFC控制方法，採用變頻控制方式，結合反覆控制與適應性控制技術，改善輕載操作模式的效率與功因。本文同時提出一種新的電流取樣方式，使得回授電流在定頻、變頻以及不連續導通模式下，不需經過電流取樣修正演算法或快速取樣來取得平均電流。在輕載下應用適應性控制技術調整開關頻率，降低開關損耗而提升效率。本文提出系統化的設計程序，使反覆控制器配合電流迴路的設計可兼具頻寬與穩定性，消除因系統變化與非線性因素或是負載波動所造成的週期性穩態誤差，使線電流在負載變化下，仍能維持低諧波失真。本文同時說明DSP PFC控制器的實現議題，採用TMS320F28035實驗驗證所提出的控制方法，針對數位控制器的解析度分析、控制演算法的實現與反覆控制器的實現等等，進行系統化的說明。本文以額定功率為675 W的PFC轉換器進行實現驗證，在10~100 %的負載變化下，進行了分析比較，實驗結果顯示所提出的方法在負載低於50 %的條件下，均有較優異的表現。

To maintain high efficiency and power factor over wide load variation range is very difficult by a boost PFC converter using conventional analog control. This thesis proposes a multi-mode control method using repetitive and adaptive control techniques to improve light load efficiency and power factor. A new current sensing scheme is developed to detect the average current under fixed, variable switching frequency operation or in discontinuous mode without current sampling correction or oversampling method. An adaptive switching frequency control technique is developed to reduce switching losses and improve efficiency at light load. A design procedure is given for synthesizing the current loop controller and repetitive controller to minimize periodic errors caused by system, nonlinear characteristic or load variation, and maintains low total harmonic distortion. This thesis also illustrates the implementation issues of digital PFC controllers aimed at resolution, control algorithms, repetitive controller and so on. A 675 W single-phase boost PFC converter with programmable DSP controller has been constructed for the verification and comparison of the proposed control scheme under 10~100 % loads. Experimental results show that the proposed control scheme has better performances over wide load range especially below 50 % load.