數位式初級側調整式返馳式轉換器之電池充電器

Abstract

本研究目的在研製一返馳式轉換器之數位式鋰電池充電系統，有別於傳統充電控制使用兩組類比轉數位(ADC)通道回授控制以達到定電流、定電壓控制，本研究僅使用一組類比轉數位通道回授即可達成定電壓、定電流之充電規則。整體系統架構分為兩部分：第一部分為返馳式轉換器，此轉換器操作於直流-直流且不連續導通模式下，利用此轉換器並加入初級側調整技術，經由輔助繞組回授輸出電壓，可以去除傳統式使用光耦合器回授之溫度限制以及降低成本。第二部分為數位化控制迴路，利用一德州儀器公司製造生產之數位訊號處理器(DSP)進行訊號處理。在定電流充電的情況下，我們使用所提出之責任週期控制法，僅回授輸出電壓而無回授輸出電流資訊的情況下，經由控制器運算亦可達到輸出定電流之需求，電流誤差在輸出額定電流0.7安培上為7%；而在定電壓充電的情況下，我們採用一數位式比例-積分(PI)控制器來達到穩定輸出定電壓之需求。

A flyback converter of a lithium battery charging system by digital control is proposed in this thesis. To compare with conventional researches of constant current (CC) and constant voltage (CV) regulation, the thesis proposes an improved control method by utilizing only one ADC channel to achieve CC and CV regulation. The system contains two stages. The first stage is a front-end flyback converter which operates in DC-DC discontinuous current mode (DCM), and used primary side regulation (PSR) to sense the output voltage from auxiliary winding. The PSR replaces the opto-coupler for eliminating from temperature limitation and reducing the cost. The second stage is the digital feedback loop, which processes the controlled signal by a digital signal processor (DSP) TMS320F2812 from Texas Instrument (TI). The procedure of control methods are shown as follows. At CC charge mode, it is proposed a duty control method to regulate the output current only by sensing the output voltage. Without current sensing, this proposed method still can achieve CC regulation precisely. The deviation of rated output current 0.7A is 7%. The CV charge is adopted a digital proportional-integral (PI) controller to regulate the output voltage.