應用於準諧振返馳式轉換器之諧振波谷電壓偵測與切換電路

Abstract

在隔離型電源轉換器中，返馳式轉換器由於具有電路架構簡單、低成本和較少的元件數目之特性，因此廣泛地使用在低功率電子產品上。為了降低返馳式轉換器技術中所面臨的開關切換損耗，柔性切換技術因應而生；準諧振波谷切換即為可實現開關柔性切換的技術之一，它和傳統的硬性切換返馳式轉換器相比擁有許多優點，但仍保有返馳式轉換器的特性。 本論文提出利用擾動觀察法與微分器架構兩種不同方式，皆能實現波谷切換，並且不受電路延遲問題影響，達成開關電晶體於汲極電壓最低點時導通，藉此減少切換損失，以提高系統效率與降低電磁干擾(EMI)。最後，本論文提供兩種架構之實際晶片實驗結果，並比較兩者之差異與優缺。

Of all the isolated power converters, flyback converters are widely used for low power electrical applications since its property of the simple circuit topology and low cost. In order to reduce the switching losses in flyback converters, many kinds of soft-switching techniques are developed. One of them is the valley-switching quasi-resonant converter (QRC), which has many advantages and still possesses the merits of conventional flyback converters. In this thesis, two different valley-switching techniques are proposed and implemented for the quasi-resonant flyback converter: perturbation and observation method and differentiator architecture. The circuit transmission delay and gate-drive delay are both considered and cancelled out in the proposed circuits. Therefore, the power MOSFET can be turned on when the drain-to-source voltage is at the valley of resonance, which is independent of the circuit transmission delay and gate-drive delay. By using the proposed architectures, the switching losses are minimized, the system efficiency is improved, and the EMI is also reduced. Finally, the experimental results are provided to verify the analysis and simulations.