具動態時脈控制技巧之高性能電流-電壓雙模式直流-直流降壓穩壓器

Abstract

本論文提出一具有高轉換效率、快速暫態響應以及低成本之電流-電壓雙模式直流-直流降壓穩壓器。本次提出之電流-電壓雙模式可以根據電路不同的環境需求，將其控制模式切換至電流模式或是電壓模式，以求最好的整體效能。而透過本次提出的動態時脈控制技巧，可以使電路在做暫態響應時能夠改變其切換頻率，進而改善其輸出變化，也同時加速其反應時間。此外，在緩啟動電路上亦提出一全新控制電路，以解決緩啟動電路中的嵌入式電容因為漏電流的誤判造成電路瞬間啟動時產生出的大電流。在本次設計中，除了輸出電感、輸出電容以及分壓電阻外，其餘電路皆實現在晶片中，故在面積及花費上也有所改善。此電流-電壓雙模式控制降壓型穩壓器的電路設計是由台灣積體電路製造股份有限公司2P4M 0.35μm互補式金氧半製程來實現。輸入電壓為2.7~4.2V，輸出電壓為0.9~2.7V，此規格適用於手持式產品之應用。當輸出負載瞬間從50mA抽載至500mA時，其回復時間與輸出電壓變化分別小於5μs與94mV，與傳統架構相比，則分別減少了83％的回復時間及36%的電壓變化。本次設計之電路在負載電流為100mA時可以達到其最大轉換效能95.784％。在輸出負載電流為30mA~600mA的範圍內，其轉換效能皆可達90％以上。透過本次提出之設計，可以使直流-直流降壓穩壓器之整體性能有效地提升。

This thesis presents a novel high-efficiency, fast-transient, and low-cost current-voltage dual-mode (CVDM) dc-dc buck converter using adaptive clock controller (ACC). The proposed CVDM control can switch the control method between current mode and voltage mode to improve the performance according to different situations. By using the ACC technique, the circuit can dynamically and smoothly adjust the switching frequency during the transient response to improve the undershoot, overshoot voltage, and recovery time. Moreover, the proposed on-chip soft-start circuit can eliminate the excess large current during the startup of the regulator. In this work, only an output inductor, capacitor, and feedback resistors are outside the system on chip (SoC), so the chip area and the cost can be reduced effectively. The circuit was implemented by TSMC 0.35-μm CMOS process. The input voltage is 2.7~4.2V and the output voltage is 0.9~2.7V accordingly, which is suitable for portable devices. The transient recovery time and undershoot voltage are less than 5μs and 94mV, respectively, for the load current change from 50mA to 500mA. As compared with the traditional structure without any fast transient technique, the performance of transient recovery time and undershoot voltage can be reduced by 83% and 36%, respectively. The maximum conversion efficiency is 95.784% at 100mA load current. Above 90% conversion efficiency can be achieved for load current from 30mA to 600mA. With the proposed techniques, the performance of the dc-dc converter is improved significantly.