Inductor Current Sensing Scheme for High-Precision Output Current Control

近年來，由於各方面的技術提升，高亮度白光LED已逐漸取代其他的照明而成為最佳的發光源。初級側調控器(Primary-Side Regulator, PSR)憑藉著其對輸出電流的控制能力和可以接受全電壓輸入的特性，被廣泛地應用於LED照明驅動器。但是，傳統的初級側調控器在部分的應用中，卻潛藏著輸出電流失控的問題，因而減少LED壽命。本論文主旨在提出一種高精確度輸出電流控制的電感電流感測方法(Inductor Current Sensing Scheme, ICS2)。同時，本策略不僅可以應用於隔離式功率轉換器，亦可以應用到非隔離式功率轉換器等多種場合。本論文所提出ICS2乃是利用電感電流線性斜率的特性，來修正無法在實際線路上量測到的電感電流的波峰和波谷值。藉由正確電感電流的波峰、波谷值和電感電流的導通時間，在不需要精確電感參數的情形下，計算出每一切換週期實際的輸出電流。一旦實際的輸出電流可以正確的回授到控制器內，即可達到精確控制的穩態輸出電流。本論文針對所提出之電感電流量測策略的操作原理與數學推導做詳盡的描述。最後，實作採用ICS2之四組由小到大不同功率與不同架構轉換器所做成的LED驅動器雛型機，並且透過電腦模擬與實測結果來驗證本電感電流感測方法的效能。Recently, the high brightness white light-emitted diode (LED) has become the best lighting source. A primary-side regulator (PSR) is widely used for the LED lighting application. However, the PSR often experiences the drawback of output current inaccuracy which will shorten the LED’s lift-time. The objective of this dissertation is to propose the inductor current sensing scheme (ICS2) which can be adopted to different circuit topologies to achieve high-precision output current. The proposed ICS2 senses the slope of inductor current to obtain the correct peak and valley values of inductor current. With the correct value and conduction time of the inductor current, the proposed ICS2 can achieve high-precision output current regulation. The operation principle and mathematic derivation of the proposed ICS2 are developed thoroughly. Four ICS2-based prototypes with small, middle and large power ratings for LED lighting application are built and tested. Computer simulations and experimental results are presented to confirm the performance of the proposed ICS2