應用在LLC同步整流控制器的低輸入漂移電壓、低共模電壓的放大器

Abstract

由於各國對於能源轉換效率的要求不斷提高，因此業界為了提高LLC轉換器的轉換效率，而提出同步整流的架構。同步整流是以電晶體開關取代傳統的整流二極體。為了讓電晶體開關能夠模擬出整流二極體的行為，需要同步整流控制器去控制電晶體開關。 但是，由於製程的非理想性，使得應用在同步整流控制器的比較器帶有一個輸入漂移電壓。此輸入漂移電壓會抵消系統送來的訊號量，造成同步整流控制器無法及時地關掉電晶體開關，造成轉換效率降低的問題。在本論文中，提出了一個具有低輸入漂移電壓、低共模電壓的前級放大器，此前級放大器能夠先將系統送來的訊號量放大後，再送給比較器。由於其具有低輸入漂移電壓的特性，所以系統的訊號量不會被抵消，並且由於低輸入共模偏壓的特性，使其能在同步整流的應用環境中正常工作。

The requirements of the power converter efficiency are gradually increasing, therefore, the synchronous rectifier had been provided for LLC converter. The basic concept of synchronous rectifier is utilized a transistor switch to replace the traditional rectifying diode and a synchronous controller is required to control the transistor switch to work as a rectifying diode. Nonetheless, owing to the nonideal phenomena of the manufacture process, the comparator of the synchronous controller suffers an offset voltage which affects the signal from the LLC system. Therefore, the synchronous controller can not be turned off in time and the power conversion efficiency is decreased. In this thesis, a preamplifier with low input offset voltage and low common mode voltage is provided. Due to characteristic of the low input offset voltage, signal from LLC system will not be affected and can be amplified then transferred to the comparator. The characteristic of low common mode voltage ensures the preamplifier works.