新型適應性類定導通時間電流模式控制之降壓型轉換器

Abstract

近幾年來，定導通時間(Constant On-Time, COT)控制器被廣泛地應用在直流電源轉換器上。這種類型的轉換器的特色為其無論在輕載或重載下皆有很高的效率。然而，除非使用一些特殊的電路來加快其負載暫態響應，否則此種定導通時間控制的步階響應並不是很好。 本論文描述一種適應性類定導通時間電流模式控制(Adaptive Quasi-Constant On-Time Current-Mode, AQCOTCM)之控制架構並實現在降壓型轉換器上。應用此電路架構的轉換器在負載變化時將得以取得快速的暫態響應，且其操作之切換頻率不會隨著負載改變；同時亦保留傳統的定導通時間電流模式(Constant On-Time Current-Mode, COTCM)控制的好處。 本論文將先解釋傳統COT負載響應速度較慢速的特性。接著將於論文中描述修改後之AQCOTCM架構。本文亦提出本架構之小訊號模型，此模型對於如何合適地設計轉換器之回授控制是相當需要的。此外，亦提供實驗結果以作驗證之用。本論文亦涉及將此概念延伸至多相降壓型轉換器之應用。

In recent years, there have been a variety of constant on-time control (COT) schemes for DC power converter applications. This class of converters features high efficiency for both the heavy load and the light load conditions. However, its step-load transient response is, by-and-large, poor unless special circuitry is used to speed up the response. In this dissertation, an adaptive quasi-constant on time current mode (AQCOTCM) control scheme is described. Using this control scheme, a converter can achieve faster step-load response and operating frequency independence of load level while preserving the basic advantages of a conventional constant on-time current mode (COTCM) converter. In the dissertation, an explanation is given first about the basic characteristic of slow step-response of conventional COT schemes. Then modifications are described that lead to the AQCOTCM scheme. A small-signal control model is then developed that is essential for the proper design of the converter feedback control. Experimental results are shown for the verifications. Extension of the concept to multiphase buck converter application is also described