非同步自動調零技術使輸出電壓變化小於3%的固定導通時間控制轉換器應用於28奈米製程的5G無線通訊系統

Abstract

此論文提出一應用於固定導通時間控制之切換式電源轉換器並具備輸出電壓漣波恢復補償器、暫態增強機制、及非同步自動調零技術。由於固定導通時間控制法將因為輸出電容等效串聯電阻太小，致使系統的穩定度會大幅受影響。但大的等效串聯電阻雖然可以確保系統穩定性，卻也使得輸出電壓漣波過大。因此在此提出輸出電壓漣波恢復補償器，可以使系統應用於小的輸出電容等效串聯電阻，並提高系統的穩定度。另外針對輸出電壓的高精準度，在先進製程中也非常的重要，另外，由於先進製程對供應電壓變化的容忍度較低，電壓過高易造成電晶體過壓燒壞，而電壓過低則會影響到整個系統的操作。在這邊針對電源轉換器的輸出電壓受影響的兩大因素，分別是穩態時的偏移電壓及暫態響應，提出了非同步自動調零技術及暫態增強機制，使輸出電壓在穩態時的偏移電壓從 ±3% 改善至 ±0.5% ，且在抽載範圍為500毫安培時，變化仍小於 3% 。本論文所提出的架構實現於二十八奈米製程，適用於5G無線通訊系統，晶片面積僅0.0019平方公釐。

An integrated constant on-time (COT) controlled step-down converter in a 28nm CMOS process with the proposed ripple-recovered compensator (RRC), transient-enhanced (TE), and asynchronous auto-zero (AAZ) technique is presented in this thesis. The RRC technique increases system stability and ensures small output voltage ripple without using an output capacitor which contains a large equivalent series resistance (ESR) for increasing system stability compared to conventional designs. With the adoption of TE technique, transient response time in case of load change is decreased compared to conventional COT controlled step-down converter. Furthermore, the AAZ technique is seamlessly incorporated into the proposed converter without modifying the original operation of COT control, demonstrating a genuine and robust DC offset cancellation solution without the need of large transistor dimensions or the use of I/O devices. Experimental results show voltage variation can be limited within ±3% of its rated value during a transient perturbation of 500 mA step load change. Proven with a small silicon area of 0.0019mm2, the regulated steady state voltage error is suppressed from ±3% to ±0.5% with the AAZ technique. The proposed COT controlled step-down converter provides a reliable solution to the stringent requirement of the IEEE 802.11ac compliant 5G wireless fidelity (Wi-Fi) systems realized in 28nm CMOS process.