具降壓-線性混合技術應用於改善輸出下降電壓和暫態響應之負載預備降壓轉換器

Abstract

近來在消費性電子產品中，以可攜式產品的應用上，需求越來越廣泛，如:手機、筆記型電腦等。因此，高轉換效率的電壓轉換器會是非常重要的元件在眾多可攜式產品中。一個使用電感的切換式直流/直流轉換器可以達到高轉換效率，但是它的頻寬卻受限於自身的操作頻率。相對地，線性轉換器犧牲了效率，但擁有高頻寬。因此，先前的文獻中有利用串聯或並聯的方法，結合線性轉換器和切換式轉換器的特性，以此來提升效率。然而線性轉換器卻只在暫態時才工作，因此會造成積體電路面積的浪費。 本論文提出，應用於系統單晶片具有線性-降壓混合技術之負載預備降壓器。在本篇提出具有混合模式的轉換器，可以在負載瞬間發生變動時，有效地改善直流/直流轉換器的暫態響應，實現較小的輸出電壓變動和加快暫態回復時間。除了高轉換效率能夠實現之外，一個輔助的電源開關只有在負載暫態期間才會操作在混合模式。量測結果中顯示了，暫態響應中的輸出下降電壓和回復時間都有明顯地改善。當負載電流瞬間由100毫安培增加至550毫安培時，輸出下降電壓可以從320毫伏特減少為150毫伏特而且暫態周期也由80微秒縮短成30微秒。相較於傳統沒有線性-降壓混合技術的設計，在輸出下降電壓和回復時間可以分別有57%和70%的改善，且在規格上的最高輸入電壓時，會有最高8%的效率改善。

Recently, portable and battery powered products such as mobile phones, notebook are increasing. High conversion efficiency voltage regulators are critical components in many portable products. It can be obtained with a switch-mode inductive DC/DC converter, but its bandwidth is limited due to practical switching frequency. Relatively, linear regulators enable higher bandwidth at the cost of efficiency. Therefore, previous works use a modulator which combines linear regulator with a switch-mode converter in series connection or parallel connection. This method increase efficiency successfully. However, the linear regulator function just works in the transient period. It wastes a chip area for that method. A hybrid buck-linear (HBL) technique in a load-preparation buck (LPB) converter for system-on-a-chip (Soc) applications is proposed in this paper. The proposed converter with hybrid operation can effectively enhance the transient response with a small dip voltage and fast transient recovery time in case of a sudden load variation in Soc applications. In addition, high power conversion efficiency can be derived, as an auxiliary power switch assures that hybrid operation is only activated in the load transient period. Experimental results demonstrate the improved transient performance at transient dip voltage and recovery time. The dip voltage is is reduced from 320 mV to 150 mV and the transient period is shortened from 80 μs to 30 μs as the load current suddenly changes from 100mA to 550mA. Compared with the conventional design without HBL technique, the performances of dip voltage and recovery time are enhanced 57% and 70%. The 8% peak efficiency improves at the highest input voltage.