高速磁滯電壓轉換器之漣波電壓改善

Abstract

本論文提出一高速磁滯電壓轉換器，透過負載判定回授的方式，藉以達到在不改變輕載的漣波電壓下，降低重載的漣波電壓。此一電路建構在磁滯式控制的電壓轉換器。整體電路可細分為能隙電壓產生電路、磁滯比較器、輸出級、過電流保護比較器、過電流保護計時電路及負載判定回授等部份。磁滯式控制的電壓轉換器主要是藉由輸出電壓的回授訊號與晶片內部所產生的能隙電壓相比較，從而決定輸出級的開關比，而本論文所提出的系統其運作的方式主要是偵測系統的負載情況，並將負載狀況回授給磁滯比較器，磁滯比較器將依照負載的回授量控制系統的磁滯電壓大小，以達成降低重載時的電壓漣波的功能。 在晶片啟動時，電感電流在未受保護的情形下會有過高而破壞系統的可能性，因此設計了過電流保護電路來防止電感電流過大的情形發生，而軟啟動的功能也同時藉由此一電路來達成。最後經由實驗證明，本系統能夠達到負載偵測、控制系統磁滯及提升系統效率的預期目標。

High-speed switch converter based on hysteretic control algorithm with improved loading adjustment feedback control is proposed. The whole-chip is built by bandgap reference circuit, high-speed hysteretic comparator, driver stage, over-current protection circuit, delay-time control, and load detection feedback control. Output voltage feedback signal compares with the bandgap reference voltage by hysteretic comparator to decide the duty ratio. This thesis is to control the hysteresis voltage based window to reduce the output ripple voltage at heavy loads. The inductor current may be too larger if the less of over-current protection function. The large current will either saturate the inductor or crack the system by heat. As a result, the over-current protection circuit is added to avoid this situation. Soft-start function is induced in this block, too.